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Chemistry of Fireworks

Chemistry of Fireworks

Developed nearly two millennia ago in ancient China, fireworks are increasingly used in cultural celebrations around the world and enjoyed by nearly all ages. As one of the most entertaining forms of chemistry, fireworks appeal to our senses of sight and sound, offering a staggering variety of colors, sizes, shapes, sounds, and so on. We love to watch fireworks because they take our breath away with their magnificence and mystery.

However it is not all fun and games. The business of fireworks (and the field of pyrotechnics in general) is very serious since they should be made as safe as possible to use and also environmentally friendly. Beyond fireworks, other pyrotechnics are found in all kinds of entertainment, like in concerts, movies, and more serious applications for defense and security (e.g., safety measures like flares and signal lights).

What are fireworks made of?

Early fireworks were quite dangerous and were used for protection rather than for celebrations, and hardly resemble the ones we are now familiar with.

It all began back in Ancient China with the invention of gunpowder, which was created from a mixture of charcoal, sulfur, and saltpeter (potassium nitrate). Eventually, as new developments were made to increase the safety and predictability of using these early fireworks, experimentation with colors began and people started using them more for nonviolent purposes. Now there is an entire industry devoted to the development of all kinds of fireworks for consumers and professionals alike.

Learn more about the history of fireworks in the links below:

A firework, or aerial shell as it is also known, basically consists of three main parts aside from the housing: gunpowder and an igniter to make the rocket explode, and inside of the transported capsule on the top there are small garniture pods usually called «stars» (despite being shaped like spheres or cylinders) that include various chemicals for the desired effects. Stars consist of a colorant, a fuel, an oxidizer (oxygen providing substance, e.g., chlorates or nitrates), and a binder to hold the ingredient mixture together in a compact briquette.

The industry has spent a significant amount of time in development to make fireworks explode in shapes like stars and stripes, hearts, or even more complex forms like a cartoon figure, or letters and numbers if timed correctly.

Cross-sectional diagram of a firework capsule filled with star garnitures (72) and igniter (70). [1]

Forming a rainbow of colors

The vibrant colors of fireworks come from the combustion of metal ions which make up to 20% of the components. Metals have been used to color flames even before the invention of modern fireworks (e.g. Bengal fire). Chemically speaking, these metal ions change their electronic state by heating (addition of energy) and then going back to a lower energy state before emitting light of a certain color.

Table 1. List of metals used in pyrotechnics and their colors [2].

Color

Metal

Example compounds

Red

Strontium (intense red)

SrCO3 (strontium carbonate)

Lithium (medium red)

Li2CO3 (lithium carbonate)

LiCl (lithium chloride)

Orange

Calcium

CaCl2 (calcium chloride)

Yellow

Sodium

NaNO3 (sodium nitrate)

Green

Barium

BaCl2 (barium chloride)

B3N3 (boron nitride)

Blue

Copper halides

CuCl2 (copper chloride), at low temperature

Indigo

Cesium

CsNO3 (cesium nitrate)

Violet

Potassium

KNO3 (potassium nitrate)

Rubidium (violet-red)

RbNO3 (rubidium nitrate)

Gold

Charcoal, iron, or carbon black

 

White

Titanium, aluminum, beryllium, or magnesium powders

 

Very prominent here is the yellow color from sodium which is also seen in older street lightbulbs in some countries. Unfortunately, the most vibrant colors formed are also the most toxic for the environment, like strontium (red) and barium (green). These contaminants can be measured in the air, water, and even in the soil—but more on that later.

Find out more information about how fireworks get their colors in the links below:

Safety first

Safety is always a critical issue when discussing fireworks, whether concerning their construction, their use, or their storage. Too many serious accidents have happened over the years involving fireworks.

Learn more about how to handle fireworks in a safe manner here:

Among one of the largest fireworks disasters recorded in Europe was in Enschede (The Netherlands) in 2000. This explosion occurred in the warehouse of the S.E. Fireworks factory, which was located in the center of a residential area as the city grew and continued to build homes around it. An entire neighborhood was razed and the largest of the explosions was felt up to 30 kilometers away.

Because of this incident, sales of larger fireworks in most European countries is only allowed outdoors. Accumulating fireworks at home in preparation for celebrations should be avoided at least in confined environments like basements or apartments. It is better to store them in a ventilated shed or car parking to avoid problems in the case of a fire. Also do not store fireworks for long periods, since most of commercial fireworks are meant to be used within 3–6 months after production because the paper contents can get humid, ionic substances can dissolve and recrystallize, and therefore the likelihood of a failure increases.

In the event of a firework failure: Never have a look immediately! Wait at least 15 minutes at a proper distance and then use a tool to confine it afterwards—never touch it with your bare hands, especially when dealing with exploding fireworks or rockets.

Having said this, fireworks have integrated some safety features over the last several years to work more properly and reliably. For instance, the propellants have been modified from containing black powder to using technology from rockets such as plasticizers for better burning performance during launch, also resulting in less smoke and dust on the ground. A dedicated chain of reactions has to be followed, otherwise it will burn in a harmless way.

Knowledge is power: Prevent accidents with proper analytical testing

In order to help prevent fireworks accidents such as the one in Enschede and countless others, it is crucial to closely monitor different quality parameters including the water content of paper-based fireworks, grain size of the metal particles, and the purity and composition of the colorant, just to mention a few. Adequate quality control provides an entertaining, but safe fireworks experience even in the hands of the general public, when proper protocols are followed.

Metrohm offers several analytical technologies and related applications for this area of research. Analyses can be performed for a wide variety of substances and quality parameters as well as trace materials in the laboratory, on the street, and in the air either via wet chemical methods (e.g., Karl Fischer titration, ion chromatography, voltammetry) or spectroscopic techniques (e.g., near-infrared spectroscopy [NIRS] and Raman spectroscopy).

As mentioned earlier, moisture is an important quality parameter when discussing the safety of explosive materials. Metrohm offers two different techniques for accurate analysis of water content in a variety of matrices which are outlined in the following blog posts.

When it comes to determining the individual concentrations of the main constituents, some wet chemical techniques really stand out. Suppressed anion chromatography is ideal for measuring the ionic components of e.g., firecracker powder, other explosive material, and even in explosion residues for forensic purposes. Coupling an ion chromatograph to a mass spectrometer (IC-MS) opens up even more analysis possibilities. Read more about these studies (and more) by downloading our free Application Notes.

The use of several different metal salts to create the vibrant colors of fireworks can be beautiful but also harmful to our health and that of our environment. Voltammetry (VA) is an electrochemical method suitable for the determination of trace and ultratrace concentrations of heavy metals and other electrochemically active substances. Not only is VA excellent at determining these substances in the laboratory, but also in the field such as for measuring the after effects of a fireworks display or an undesired event. Check out our selection of VA instruments and applications on our website.

Spectroscopic techniques like Raman can help to determine the presence of dangerous explosive materials even when keeping a safe distance by using different instrument attachments. Read our free White Paper about how to use MIRA DS from Metrohm Raman for the purpose of identifying explosives safely.

Environmentally friendly fireworks – a contradiction?

Although fireworks are a very spectacular form of entertainment, there is quite an environmental impact after big cultural events or national holidays. The general atmospheric pollution after a fireworks display has been set off can be seen in an increase of dust and smoke, but also heavy metal content in the air as most contemporary fireworks use these for coloring.

The unburnt material still contains a significant amount of heavy metals. After falling to the ground, this material can dissolve and enter the ground water after it rains. Plastics materials that covered the fireworks for safety reasons are found again as broken shell shrapnel or as microplastics. The combustion of the compounds inside the fireworks leads to increased air pollution in form of aerosols that can be measured and evaluated resulting in heavy metals in the air, fine dust, and even nanoparticles which are extremely harmful for our lungs.

Metrohm Process Analytics has developed the 2060 MARGA (Monitor for AeRosols and Gases in ambient Air) which is used by official agencies and research bodies worldwide to monitor the air quality fully autonomously. This instrument is based on the analytical technique of ion chromatography and can be used as a dedicated continuous air monitoring device that can be left unattended for several weeks at a time, or as a research instrument that can be used for other projects when not monitoring the air quality.

Learn more about the 2060 MARGA and its capabilities in our blog post.

To find out more about the use of Metrohm instruments to monitor the air quality, check out this selection of peer-reviewed articles.

A new «green» firework generation is being developed for both professional and indoor use to try to minimize the heavy metal content and also reduce aerosol forming agents. This makes them more suitable for indoor pyrotechnic shows and for movie production. In regular outdoor shows (e.g. at theme parks), the gunpowder for transport of the capsule has mostly been substituted with an air pressure gun mechanism.

A significant amount of research has gone into substituting heavy metal-based colorants with more environmentally benign substances by increasing the luminosity of lithium derivatives by substituting them for strontium, or by using boron instead of barium or chlorinated compounds.

Finally, the plastic parts commonly used to surround fireworks are planned to be substituted by microcrystalline cellulose mixtures with better plasticizing binders. This leads to a similar stability compared to the current plastic materials, but the cellulose-based containers burn up completely and do not leave harmful materials scattered on the ground.

The future of fireworks shows

All safety measures increase the joy of fireworks not only during, but also after the event—being green and being safe. Foretelling the future, some of these celebrations may now use a cadre of lighted drones in a choreographed dance. This has been happening more steadily as drones fall in price and increase in their handling and programming capabilities. However, fireworks have already been with us for a couple of thousand years, and probably will not disappear any time soon.

Download our free Application Notes

and White Papers related to explosives and propellants

Post written by Dr. Norbert Mayr (Ph.D. in the field of HEDM, pyrotechnics, propellants, and oxidizers), Marketing Specialist & Product Training at Metrohm International Headquarters, Herisau, Switzerland.

Supercharge your battery research – Part 1

Supercharge your battery research – Part 1

Replacing traditional fuel-powered vehicles with battery-powered options is essential to reduce carbon dioxide (CO2) emissions. This greenhouse gas results from the combustion of fossil fuels, therefore limiting its input into the atmosphere will also influence global warming. Battery research therefore focuses on discovering new materials with higher energy and power density as well as a more efficient energy storage.

Various critical parameters need to be determined to develop viable new batteries. In this first of two blog posts, I want to highlight a few of the analytical parameters which can be determined using high precision analytical instruments from Metrohm and provide some free downloads in this research area.

What’s in a lithium battery?

Today, lithium ion batteries are the most common rechargeable batteries available on the market. A battery consists of an anode (negative pole) and cathode (positive pole). An electrolyte facilitates charge transfer in the form of lithium ions between these two poles. Meanwhile a separator placed between anode and cathode prevents short-circuits. An example cross section can be seen in Figure 1.

Figure 1. Cross-section illustration of a lithium ion battery. While the battery is being charged, lithium ions migrate from the cathode to the anode (from right to left), and during discharging they move from the anode to the cathode (from left to right).

The anode is made from graphite containing intercalated lithium applied to a copper foil, while the cathode consists of metal oxides dotted with lithium ions applied to an aluminum foil. The most common transition metals used in cathode materials are cobalt, nickel, manganese, or iron. The electrolyte is an anhydrous aprotic solvent containing a lithium salt (e.g., lithium hexafluorophosphate) to facilitate charge transfer. The separator is prepared from a porous material, acting as an insulator to prevent short-circuits. The composition of all of these components has a significant influence on the battery characteristics.

After this brief overview about the composition of a lithium battery, let’s take a look at selected key parameters and how they can be analyzed.

Water content in battery raw materials

Lithium-ion batteries should be free of water (concentration of H2O less than 20 mg/kg), because water reacts with the conducting salt (e.g., LiPF6) to form toxic hydrofluoric acid. Sensitive coulometric Karl Fischer titration is the ideal method for determining water content at trace levels. Water determination for solids is carried out using the Karl Fischer oven method – the residual moisture in the sample is evaporated and transferred to the titration cell where it is subsequently titrated. The working principle and advantages of the KF oven method are described in more detail in our blog post «Oven method for sample preparation in Karl Fischer titration».

For more details on how to carry out the water determination in one of the following battery components, download our free Application Bulletin AB-434:

 

  • raw materials for the manufacture of lithium-ion batteries
  • electrode coating preparations (slurry) for anode and cathode coating
  • the coated anode and cathode foils as well as in separator foils and in packed foil layers
  • electrolytes for lithium-ion batteries

Transition metal composition of cathode materials

The cathode of a lithium-ion battery is usually made from metal oxides derived from cobalt, nickel, manganese, iron, or aluminum. To produce the cathode, solutions containing the desired metal salts are used. For an optimized production process, the exact content of the metals present in the solution must be known. Additionally, the metal composition within the obtained cathode material should be determined. Potentiometric titration is a suitable technique to determine the metal content in starting solutions and the finished cathode materials.

The following mixtures of metals or metal oxides can be analyzed potentiometrically:

  • Nickel, cobalt, and manganese in solutions
  • Nickel, cobalt, and manganese in cathode materials such as cobalt tetraoxide (Co3O4), lithium manganite, or lithium cobaltite

For more details about the potentiometric analysis of a mixture of nickel, cobalt, and manganese download our free Application Note AN-T-218.

Analysis of lithium salts

Potentiometric titration is also ideally suited for determining the purity of lithium salts. For lithium hydroxide and lithium carbonate, the purity is determined using an aqueous acid-base titration. It is also possible to determine carbonate impurity within lithium hydroxide using this method.

For more details about performing the assay of lithium hydroxide and lithium carbonate, download our free Application Note AN-T-215.

For the assay of lithium chloride and lithium nitrate, the lithium is directly titrated using the precipitation reaction between lithium and fluoride in ethanolic solutions. For more details about how to carry out the assay of lithium chloride, download Application Note AN-T-181 and for lithium nitrate download AN-T-216.

The knowledge of other cations which might be present in lithium salts (and their concentration) is also of interest. Various cations (e.g., sodium, ammonium, or calcium) can be determined using ion chromatography (IC). IC is an efficient and precise multi-parameter method to quantify anions and cations over a wide concentration range.

The chromatogram in Figure 2 shows the separation of lithium, sodium, and calcium in a lithium ore processing stream.

Figure 2. Ion chromatogram of the lithium ore processing stream (1: lithium, 23.8 g/L; 2: sodium, 1.55 g/L; 3: calcium, 0.08 g/L).

For more information on how this analysis was carried out, download our free Application Note AN-C-189.

Eluated ions and decomposition products

In the development and optimization of lithium-ion batteries, one of the items of special interest is the content of ions (e.g., lithium, fluoride, and hexafluorophosphate) in the electrolyte or in eluates of different components. Ion chromatography allows the determination of decomposition products in electrolyte, or anions and cations eluated for example from finished batteries. Additionally, any sample preparation steps that might be required (e.g., preconcentration, dilution, filtration) can be automated with the Metrohm Inline Sample Preparation («MISP») techniques.

For more detailed information about selected IC applications for battery research, check out our Application Notes:

  • Cations in lithium hexafluorophosphate (AN-C-037)
  • Trace cations in lithium hexafluorophosphate (AN-CS-011)
  • Anions in electrolyte (AN-N-012)
  • Decomposition products of lithium hexaflurophosphate (AN-S-372)

Summary

This blog post contains only part of the analyses for battery research which are possible using Metrohm’s analytical instruments. Part 2 discusses the electrochemical characterization of batteries and their raw materials. Click below to read it!

Battery research

Positive experiences with top quality Metrohm equipment!

Post written by Lucia Meier, Technical Editor at Metrohm International Headquarters, Herisau, Switzerland.

Chemistry of Chocolate

Chemistry of Chocolate

Swiss… Belgian… Pure… Milk…

Here we are in mid-February again, bombarded by chocolate from all sides in preparation for Valentine’s Day on the 14th. Whether in a solid bar, as a chewy truffle, or as a luxurious drink, chocolate has completely infiltrated our lives. Most people can agree that this confectionary treat is fantastic for any occasion – to be given as a gift, to recover after having a bad day, as well as to celebrate a good one – chocolate is certainly meant to be enjoyed.

Even if you don’t like the taste, the chances are high that someone close to you does. So how can you be certain of its quality?

Components of a chocolate bar

For the sake of this article, let us consider the humble chocolate bar, without any extra additions (not to mention any Golden Tickets). This form can be found worldwide in nearly any grocery store or candy shop, generally designated as white, milk, or dark.

All of this variability comes from the edible seeds in the fruit of the cacao tree, which grows in hot, tropical regions around the equator. They must be fermented and then roasted after cleaning. From this, cocoa mass is produced, which is a starting base for several uses. Cocoa butter and cocoa solids are prepared from the cocoa mass and are utilized in products ranging from foods and beverages to personal care items.

As for chocolate bars, these are generally sweetened and modified from the pure form, which is very bitter. Milk (liquid, condensed, or powdered) is added to many types, but does not necessarily have to be present. Varying the content of the cocoa solids and cocoa butter in chocolate to different degrees results in the classifications of dark to white. While some dark chocolates do not contain any milk, white chocolates do to add to the significant amounts of cocoa fat used to produce them.

In general, dark chocolate contains a high ratio of cocoa solids to cocoa butter and may or may not contain any milk. It may be sweetened or unsweetened. Milk chocolate is a much broader category, containing less cocoa solids but not necessarily a different cocoa butter content compared to dark chocolate, as milk fats are also introduced. Milk chocolate is also sweetened, either with sugar or other substitutes. White chocolate contains no cocoa solids at all, but a blend of cocoa butter and milk, along with sweeteners.

Depending on the country, there are different regulations in place regarding the classification of the type of chocolate. If you are interested, you can find a selection of them here.

What makes your favorite chocolate unique?

Of course, more ingredients are added to chocolate bars to affect a number of things like the aroma, texture/mouthfeel, and certainly to enhance the flavor. The origin of the cacao beans, much like coffee, can impart certain characteristics to the resulting chocolate. The manufacturing process also plays a major part in determining e.g., whether the chocolate has a characteristic snap or has a distinct scent, setting it apart from other brands.

In some cases, vegetable fats are used to replace a portion of the cocoa fats, although this may not legally be considered «chocolate» in some countries. The adjustment of long-standing recipes for certain chocolate brands has sometimes led to customer backlash, as quality is perceived to have changed. Truly, chocolate is inextricably tied to our hearts.

Applications for chocolate quality analysis

Nobody wants to give their Valentine a bad gift, especially out-of-date chocolate from a dubious source. Here, we have prepared some interesting analyses for different chocolate quality parameters in the laboratory.

Sugar analysis via Ion Chromatography (IC)

Most types of chocolate contain sugars or sugar substitutes to sweeten the underlying bitterness. Considering different regulations regarding food labeling and also nutritional content, the accurate reporting of sugars is important for manufacturers and consumers alike.

Sugar analysis in chocolate can be performed with Metrohm IC and Pulsed Amperometric Detection (PAD). An example chromatogram of this analysis is given below.

A small amount of commercially produced sweetened milk chocolate was weighed and dissolved into ultrapure water. After further sample preparation using Metrohm Inline Ultrafiltration, the sample (20 µL) was injected on to the Metrosep Carb 2 – 150/4.0 separation column and separated using alkaline eluent. As shown, both lactose and sucrose elute without overlap in less than 20 minutes.

Learn more about Metrohm Inline Ultrafiltration for difficult sample matrices and safeguard your IC system!

In this example, the sugar content was listed on the label as 47 g per 100 g portion (470 g/kg). Lactose was determined to be 94.6 g/kg, and sucrose was measured at 385.6 g/kg. To learn about what other carbohydrates, sweeteners, and more can be determined in chocolate and other foods with Metrohm IC, download our free brochure about Food Analysis and check out the table on page 25!

Lactose content in lactose-free chocolate

The accurate measurement of lactose in lactose-free products, including chocolate, is of special importance to consumers who are lactose-intolerant and suffer from digestive issues after eating it. Foods which are labelled as lactose-free must adhere to guidelines concerning the actual non-zero lactose content. Foodstuff containing less than 0.1 g lactose per100 g (or 100 mL) is most frequently declared as lactose-free.

Determination of lactose in chocolate is possible with IC. Here is an chromatographic overlay of a dissolved chocolate sample with lactose spikes which was analyzed via Metrohm IC using the flexiPAD detection mode.

Milk chocolate, labelled lactose-free measured via Metrohm IC (0.57 ± 0.06 mg/100 g lactose, n = 6).

The sample contained 0.6 mg lactose per 100 g, with measurement of the lactose peak occurring at 13.2 minutes. The black line is the unspiked lactose-free chocolate sample, red and blue are spiked samples of increasing concentration. To prepare the samples, approximately 2.5–5 g chocolate was dissolved in heated ultrapure water, using Carrez reagents to remove excess proteins and fats from the sample matrix. Afterward, centrifugation of the samples was performed, followed by the direct injection of the supernatant (10 µL) into the IC system. Measurement was performed with the Metrosep Carb 2 – 250/4.0 separation column and an alkaline eluent.

Interested in lactose determinations with ion chromatography? Download our free Application Notes on the Metrohm website!

Water determination with Karl Fischer Titration

The amount of water in foods, including chocolate, can affect their shelf life and stability, as well as contribute to other physical and chemical factors. Aside from this, during the processing stage, the amount of water present affects the flow characteristics of the chocolate mass.

AOAC Official Method 977.10 lists Karl Fischer titration as the accepted analysis method for moisture in cacao products.

The determination of moisture in different chocolate products is exhibited in the following downloadable poster. As an example, several samples (n = 10) of dark chocolate (45% cocoa content) were analyzed for their moisture content with Metrohm Karl Fischer titration.  Results were found to be 0.96% water with a relative standard deviation (RSD) of 2.73%. More information about this analysis can be found in our poster about automated water determination in chocolate, or in chapter 11.6 of our comprehensive Monograph about Karl Fischer titration.

Oxidation stability with the Rancimat test

Oxidation stability is an important quality criterion of chocolate as it provides information about the long-term stability of the product. Cocoa contains various flavonoids that act as antioxidants. Although the flavonoid content may vary amongst chocolate type, in general, the greater the content of cocoa solids in the chocolate, the greater its antioxidant effect.

The 892 Professional Rancimat from Metrohm determines the oxidation stability of fat-containing foods and cosmetics. The Rancimat method accelerates the aging process of the sample and measures the induction time or oxidation stability index (OSI).

Chocolate cannot be measured directly with the classical Rancimat method, as no evaluable induction time is obtained. There are many reasons for this: e.g., the fat content is too low. Traditionally, extraction of the fat from the chocolate is necessary, but not always.

Learn more about the Rancimat method on our website, and download our free Application Note about the oxidation stability of chocolate. In this Application Note, the oxidation stability of white, milk and dark chocolate is determined without extraction.

Cadmium in chocolate by Voltammetric analysis

The toxic element cadmium (Cd) can be found in elevated concentrations with high bioavailability in some soils. Under such conditions, cacao trees can accumulate cadmium in the beans. Chocolate produced from the affected beans will contain elevated cadmium levels.

Typical limit values for Cd in chocolate in the European Union are between 100 µg/kg and 800 µg/kg (EU Commission Regulation 1881/2006) depending on the cocoa content of the chocolate. Anodic stripping voltammetry (ASV) can be used to accurately determine trace quantities of cadmium in chocolate down to approximately 10 µg/kg. The method is simple to perform, specific, and free of interferences.

Chocolate samples are first mineralized by dry ashing in a furnace at 450 °C for several hours. The remaining ash is then dissolved in an acidified matrix. The cadmium determination is then carried out on the 884 Professional VA instrument from Metrohm. To learn more about how to perform the analysis, download our free Application Note.

Happy Valentine’s Day from us all at Metrohm!

Post written by Dr. Alyson Lanciki, Scientific Editor at Metrohm International Headquarters, Herisau, Switzerland.

ASTM D6304: Easier determination of moisture in petroleum products

ASTM D6304: Easier determination of moisture in petroleum products

Water in petroleum products, such as lubricating oils, jet fuel, or other similar products can have deleterious effects. Moisture is often associated with corrosion and engine wear. Knowing the water content of petroleum products can prevent damage to costly infrastructure and ensure safer operations.

ASTM D6304 «Standard Test Method for Determination of Water in Petroleum Products, Lubricating Oils, and Additives by Coulometric Karl Fischer Titration» is a standard that is often cited for moisture determination in the specifications of various petroleum products. It has been recently updated (January 2021) and now offers three procedures for accurate moisture determination.

The direct sample injection into the titration cell (Procedure A) is recommended for low viscosity samples without expected interferences. An oven (Procedure B) or water evaporator accessory (Procedure C) can be used to analyze samples that do not readily dissolve in Karl Fischer reagent, viscous samples, and samples with components that are expected to interfere with the Karl Fischer reaction.

In this blog post I want to introduce these three procedures, and then discuss when it is appropriate to use each of them.

Determining the moisture content in petroleum products doesn’t have to be messy. Visit our website to learn more about the new automated measurement capabilities allowed with ASTM D6304.

A coulometric Karl Fischer Titrator such as the 851 Titrando from Metrohm is the basis for all three procedures of ASTM D6304.

Direct injection (Procedure A)

The direct sample injection into the titration cell is recommended for low viscosity samples without expected interferences. An aliquot of known mass or volume is injected into the conditioned titration cell of a coulometric Karl Fischer apparatus, where it is titrated automatically, and the results calculated.

Method D6304 permits the use of coulometric generator electrodes with and without diaphragm. We recommend the use of the generator electrode with diaphragm, due to the low water content of the samples.

Not all petroleum products are soluble in Karl Fischer reagent and phase separation can occur when using Procedure A. If phase separation occurs, the reagents need to be replaced. The number of samples which can be analyzed without phase separation depends on the volume and type of sample, the volume of reagent, and the sample solubility in the reagent.

The generator electrode with diaphragm is recommended for water determination according to ASTM D6304 Procedure A.

However, for these kinds of samples, Procedures B or C are often the better solution. The same is the case if your sample contains interfering substances.

For more information about ASTM D6304 Procedure A, download our free Application Bulletin (AB-209). For more tips and tricks about how to improve your Karl Fischer titration, have a look at our blog series: «Frequently asked questions in Karl Fischer titration».

Water extraction using an oven (Procedure B)

An oven (Procedure B) can be used to analyze samples that do not readily dissolve in Karl Fischer reagent, viscous samples, and samples with components that are expected to interfere with the Karl Fischer reaction.

For the analysis, a representative sample is weighed into a glass vial, which is sealed immediately. The vial is then heated in an oven to extract any water. The vaporized water is carried into the conditioned Karl Fischer titration cell by means of a dry carrier gas where it is titrated.

Schematic drawing of the Karl Fischer oven method.

The ideal temperature used for the evaporation depends on the sample. The 874 Oven Sample Processor can perform a temperature gradient test to determine the optimal temperature for removing water without degrading the sample.

To learn more about the oven method, its working principle and its advantages, check out our blog post: «Oven method for sample preparation in Karl Fischer titration».

Watch our LabCast video below to see the working principle and advantages of using Procedure B.

For more information about using the KF oven method for ASTM D6304 Procedure B, download our free Application Bulletin (AB-209) or free Application Note (AN-K-070).

Just want the highlights? Have a look at our short flyer about how ASTM D6304 has become much easier!

Water extraction using an evaporator (Procedure C)

Instead of using an oven, Procedure C explains how a water evaporator can be used for the water extraction of samples that do not readily dissolve in Karl Fischer reagent, viscous samples, and samples with components that are expected to interfere with the Karl Fischer reaction.

In this procedure, an aliquot of sample is transferred into a heated chamber containing a suitable solvent (most often, toluene). The temperature of the heated chamber depends on the solvent used. The water vaporizes along with the solvent in an azeotrope distillation. The azeotrope is then transferred into the conditioned Karl Fischer titration cell via a dry non-reactive carrier gas. 

Schematic drawing of the evaporator method.

If you wish to read more about the three procedures and their advantages and disadvantages, download our White Paper: «Moisture in petroleum products according to ASTM D6304».

When to use which procedure

Procedure A is mainly suited for liquid samples with a low viscosity, such as diesel fuel, jet fuel, or aromatics. A low viscosity is required in order to be able to add the sample easily into the Karl Fischer titration cell. Furthermore, the samples require a good solubility in Karl Fischer reagent. Otherwise phase separation will occur, which requires the replacement of the Karl Fischer reagents. While the reagent exchange can be automated, time is still required until the reagents reach dryness again.

Even if samples are soluble in Karl Fischer reagents, there might still be issues with using Procedure A due to the sample matrix creating side reactions and thus false results. In this case Procedure B or C are the better option.

Procedure B is suitable for all kinds of samples, regardless of their viscosity or matrix composition. It is only the evaporated water that is transferred into the titration cell, leaving the sample as well as interfering matrix components remaining in the sealed vial, which can be simply disposed of after the analysis. For this reason, the reagent exchange frequency is greatly reduced, saving costs, as less reagent is required. Depending on the workload in your lab, it is even possible to fully automate the analysis including reagent exchange using an automated Karl Fischer oven.

The 874 Karl Fischer Oven Processor with an 851 Titrando for a fully automated analysis according to ASTM D6304 Procedure B.

Procedure C, like Procedure B, is suitable for all kinds of samples, regardless of their viscosity or matrix constitution. It is only the evaporated water in an azeotrope with the solvent that is transferred into the titration cell. The sample, as well as interfering matrix components, remain in the evaporation chamber. However, it is necessary to manually empty and refill the evaporation chamber from time to time, which is time consuming, as the chamber needs to cool down before the content can be exchanged. Furthermore, walk-away automation is not possible with this method.

For a more detailed comparison of the various factors for each procedure, download our free White Paper: «Moisture in petroleum products according to ASTM D6304».

Visit our website

Save time with the new automated measurement capabilities allowed with ASTM D6304

Post written by Lucia Meier, Technical Editor at Metrohm International Headquarters, Herisau, Switzerland.

«Analyze This»: 2020 in review

«Analyze This»: 2020 in review

I wanted to end 2020 by thanking all of you for making «Analyze This» – the Metrohm blog for chemists such a success! For our 60th blog post, I’d like to look back and focus on the wealth of interesting topics we have published this year. There is truly something for everyone: it doesn’t matter whether your lab focuses on titration or spectroscopic techniques, or analyzes water samples or illicit substances – we’ve got you covered! If you’re looking to answer your most burning chemical analysis questions, we have FAQs and other series full of advice from the experts. Or if you’re just in the mood to learn something new in a few minutes, there are several posts about the chemical world to discover.

We love to hear back from you as well. Leaving comments on your favorite blog posts or contacting us through social media are great ways to voice your opinion—we at Metrohm are here for you!

Finally, I wish you and your families a safe, restful holiday season. «Analyze This» will return on January 11, 2021, so subscribe if you haven’t already done so, and bookmark this page for an overview of all of our articles grouped by topic!

Stay healthy, and stay curious.

Best wishes,

Dr. Alyson Lanciki, Scientific Editor, Metrohm AG

Quickly jump directly to any section by clicking a topic:

Customer Stories

We are curious by nature, and enjoy hearing about the variety of projects where our products are being used! For some examples of interesting situations where Metrohm analytical equipment is utilized, read on.

From underwater archaeological research to orbiting Earth on the International Space Station, Metrohm is there! We assist on all types of projects, like brewing top quality beers and even growing antibiotic-free shrimp – right here in Switzerland.

Interested in being featured? Contact your local Metrohm dealer for details!

Titration

Metrohm is the global market leader in analytical instruments for titration. Who else is better then to advise you in this area? Our experts are eager to share their knowledge with you, and show this with the abundance of topics they have contributed this year to our blog.

For more in-depth information about obtaining the most accurate pH measurements, take a look at our FAQ about pH calibration or read about avoiding the most common mistakes in pH measurement. You may pick up a few tips!

Choose the best electrode for your needs and keep it in top condition with our best practices, and then learn how to standardize titrant properly. Better understand what to consider during back-titration, check out thermometric titration and its advantages and applications, or read about the most common challenges and how to overcome them when carrying out complexometric titrations

If you are interested in improving your conductivity measurements, measuring dissolved oxygen, or the determination of oxidation in edible fats and oils, check out these blog posts and download our free Application Notes and White Papers!

Finally, this article about comprehensive water analysis with a combination of titration and ion chromatography explains the many benefits for laboratories with large sample loads. The history behind the TitrIC analysis system used for these studies can be found in a separate blog post.

Karl Fischer Titration

Metrohm and Karl Fischer titration: a long history of success. Looking back on more than half a century of experience in KFT, Metrohm has shaped what coulometric and volumetric water analysis are today.

Aside from the other titration blog posts, our experts have also written a 2-part series including 20 of the most frequently asked questions for KFT arranged into three categories: instrument preparation and handling, titration troubleshooting, and the oven technique. Our article about how to properly standardize Karl Fischer titrant will take you step by step through the process to obtain correct results.

For more specific questions, read about the oven method for sample preparation, or which is the best technique to choose when measuring moisture in certain situations: Karl Fischer titration, near-infrared spectroscopy, or both?

Ion Chromatography (IC)

Ion chromatography has been a part of the Metrohm portfolio since the late 1980s. From routine IC analysis to research and development, and from stand-alone analyzers to fully automated systems, Metrohm has provided IC solutions for all situations. If you’re curious about the backstory of R&D, check out the ongoing series about the history of IC at Metrohm.

Metrohm IC user sitting at a laboratory bench.

Common questions for users are answered in blog posts about IC column tips and tricks and Metrohm inline ultrafiltration. Clear calculations showing how to increase productivity and profitability in environmental analysis with IC perfectly complement our article about comprehensive water analysis using IC and titration together for faster sample throughput.

On the topic of foods and beverages, you can find out how to determine total sulfite faster and easier than ever, measure herbicides in drinking water, or even learn how Metrohm IC is used in Switzerland to grow shrimp!

Near-Infrared Spectroscopy (NIRS)

Metrohm NIRS analyzers for the lab and for process analysis enable you to perform routine analysis quickly and with confidence – without requiring sample preparation or additional reagents and yielding results in less than a minute. Combining visible (Vis) and near-infrared (NIR) spectroscopy, these analyzers are capable of performing qualitative analysis of various materials and quantitative analysis of a number of physical and chemical parameters in one run.

Our experts have written all about the benefits of NIR spectroscopy in a 4-part series, which includes an explanation of the advantages of NIRS over conventional wet chemical analysis methods, differences between NIR and IR spectroscopy, how to implement NIRS in your laboratory workflow, and examples of how pre-calibrations make implementation even quicker.

A comparison between NIRS and the Karl Fischer titration method for moisture analysis is made in a dedicated article.

A 2-part FAQ about NIRS has also been written in a collaboration between our laboratory and process analysis colleagues, covering all kinds of questions related to both worlds.

Raman Spectroscopy

This latest addition to the Metrohm family expands the Metrohm portfolio to include novel, portable instruments for materials identification and verification. We offer both Metrohm Raman as well as B&W Tek products to cover a variety of needs and requirements.

Here you can find out some of the history of Raman spectroscopy including the origin story behind Mira, the handheld Raman instrument from Metrohm Raman. For a real-world situation involving methamphetamine identification by law enforcement and first responders, read about Mira DS in action – detecting drugs safely in the field.

Mira - handheld Raman keeping you safe in hazardous situations.

Are you looking for an easier way to detect food fraud? Our article about Misa describes its detection capabilities and provides several free Application Notes for download.

Process Analytics

We cater to both: the laboratory and the production floor. The techniques and methods for laboratory analysis are also available for automated in-process analysis with the Metrohm Process Analytics brand of industrial process analyzers.

Learn about how Metrohm became pioneers in the process world—developing the world’s first online wet chemistry process analyzer, and find out how Metrohm’s modular IC expertise has been used to push the limits in the industrial process optimization.

Additionally, a 2-part FAQ has been written about near-infrared spectroscopy by both laboratory and process analysis experts, which is helpful when starting out or even if you’re an advanced user.

Finally, we offer a 3-part series about the advantages of process analytical technology (PAT) covering the topics of process automation advantages, digital networking of production plants, and error and risk minimization in process analysis.

Voltammetry (VA)

Voltammetry is an electrochemical method for the determination of trace and ultratrace concentrations of heavy metals and other electrochemically active substances. Both benchtop and portable options are available with a variety of electrodes to choose from, allowing analysis in any situation.

A 5-part series about solid-state electrodes covers a range of new sensors suitable for the determination of «heavy metals» using voltammetric methods. This series offers information and example applications for the Bi drop electrode, scTrace Gold electrode (as well as a modified version), screen-printed electrodes, and the glassy carbon rotating disc electrode.

Come underwater with Metrohm and Hublot in our blog post as they try to find the missing pieces of the ancient Antikythera Mechanism in Greece with voltammetry.

If you’d like to learn about the combination of voltammetry with ion chromatography and the expanded application capabilities, take a look at our article about combined analysis techniques.

Electrochemistry (EC)

Electrochemistry plays an important role in groundbreaking technologies such as battery research, fuel cells, and photovoltaics. Metrohm’s electrochemistry portfolio covers everything from potentiostats/galvanostats to accessories and software.

Our two subsidiaries specializing in electrochemistry, Metrohm Autolab (Utrecht, Netherlands) and Metrohm DropSens (Asturias, Spain) develop and produce a comprehensive portfolio of electrochemistry equipment.

This year, the COVID-19 pandemic has been at the top of the news, and with it came the discussion of testing – how reliable or accurate was the data? In our blog post about virus detection with screen-printed electrodes, we explain the differences between different testing methods and their drawbacks, the many benefits of electrochemical testing methods, and provide a free informative White Paper for interested laboratories involved in this research.

Our electrochemistry instruments have also gone to the International Space Station as part of a research project to more efficiently recycle water on board spacecraft for long-term missions.

The History of…

Stories inspire people, illuminating the origins of theories, concepts, and technologies that we may have become to take for granted. Metrohm aims to inspire chemists—young and old—to be the best and never stop learning. Here, you can find our blog posts that tell the stories behind the scenes, including the Metrohm founder Bertold Suhner.

Bertold Suhner, founder of Metrohm.

For more history behind the research and development behind Metrohm products, take a look at our series about the history of IC at Metrohm, or read about how Mira became mobile. If you are more interested in process analysis, then check out the story about the world’s first process analyzer, built by Metrohm Process Analytics.

Need something lighter? Then the 4-part history of chemistry series may be just what you’re looking for.

Specialty Topics

Some articles do not fit neatly into the same groups as the rest, but are nonetheless filled with informative content! Here you can find an overview of Metrohm’s free webinars, grouped by measurement technique.

If you work in a regulated industry such as pharmaceutical manufacturing or food and beverage production, don’t miss our introduction to Analytical Instrument Qualification and what it can mean for consumer safety!

Industry-focused

Finally, if you are more interested in reading articles related to the industry you work in, here are some compilations of our blog posts in various areas including pharmaceutical, illicit substances, food and beverages, and of course water analysis. More applications and information can be found on our website.

Food and beverages
All of these products can be measured for total sulfite content.

Oxidation stability is an estimate of how quickly a fat or oil will become rancid. It is a standard parameter of quality control in the production of oils and fats in the food industry or for the incoming goods inspection in processing facilities. To learn more about how to determine if your edible oils are rancid, read our blog post.

Determining total sulfite in foods and beverages has never been faster or easier than with our IC method. Read on about how to perform this notoriously frustrating analysis and get more details in our free LC/GC The Column article available for download within.

Measuring the true sodium content in foodstuff directly and inexpensively is possible using thermometric titration, which is discussed in more detail here. To find out the best way to determine moisture content in foods, our experts have written a blog post about the differences between Karl Fischer titration and near-infrared spectroscopy methods.

To determine if foods, beverages, spices, and more are adulterated, you no longer have to wait for the lab. With Misa, it is possible to measure a variety of illicit substances in complex matrices within minutes, even on the go.

All of these products can be measured for total sulfite content.

Making high quality products is a subject we are passionate about. This article discusses improving beer brewing practices and focuses on the tailor-made system built for Feldschlösschen, Switzerland’s largest brewer.

Pharmaceutical / healthcare

Like the food sector, pharmaceutical manufacturing is a very tightly regulated industry. Consumer health is on the line if quality drops.

Ensuring that the analytical instruments used in the production processes are professionally qualified is a must, especially when auditors come knocking. Find out more about this step in our blog post about Analytical Instrument Qualification (AIQ).

Moisture content in the excipients, active ingredients, and in the final product is imperative to measure. This can be accomplished with different analytical methods, which we compare and contrast for you here.

The topic of virus detection has been on the minds of everyone this year. In this blog post, we discuss virus detection based on screen-printed electrodes, which are a more cost-effective and customizable option compared to other conventional techniques.

Water analysis

Water is our business. From trace analysis up to high concentration determinations, Metrohm has you covered with a variety of analytical measurement techniques and methods developed by the experts.

Learn how to increase productivity and profitability in environmental analysis laboratories with IC with a real life example and cost calculations, or read about how one of our customers in Switzerland uses automated Metrohm IC to monitor the water quality in shrimp breeding pools.

If heavy metal analysis is what you are interested in, then you may find our 5-part series about trace analysis with solid-state electrodes very handy.

Unwanted substances may find their way into our water supply through agricultural practices. Find out an easier way to determine herbicides in drinking water here!

Water is arguably one of the most important ingredients in the brewing process. Determination of major anions and cations along with other parameters such as alkalinity are described in our blog post celebrating International Beer Day.

All of these products can be measured for total sulfite content.
Illicit / harmful substances

When you are unsure if your expensive spices are real or just a colored powder, if your dairy products have been adulterated with melamine, or fruits and vegetables were sprayed with illegal pesticides, it’s time to test for food fraud. Read our blog post about simple, fast determination of illicit substances in foods and beverages for more information.

Detection of drugs, explosives, and other illegal substances can be performed safely by law enforcement officers and first responders without the need for a lab or chemicals with Mira DS. Here you can read about a real life training to identify a methamphetamine laboratory.

Drinking water regulations are put in place by authorities out of concern for our health. Herbicides are important to measure in our drinking water as they have been found to be carcinogenic in many instances.

Post written by Dr. Alyson Lanciki, Scientific Editor at Metrohm International Headquarters, Herisau, Switzerland.