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Trace metal analysis with solid-state electrodes – Part 3

Trace metal analysis with solid-state electrodes – Part 3

In Part 2 of this series on trace metal analysis with solid-state electrodes, we introduced the scTRACE Gold electrode. The third part of this series explains even more applications which can be performed with this electrode, but this time after modifying the gold micro-wire with a thin layer of another metal.

Catch up on the series «Trace metal analysis with solid-state electrodes» here:

Why modify the electrode material?

As explained for the Bi drop electrode in Part 1 of this series, stripping voltammetry is a two-step measurement.

In the first step, the analyte is deposited on the working electrode. In the case of anodic stripping voltammetry (ASV), the analyte is reduced and forms an alloy with the electrode material (Fig. 1). In the case of adsorptive stripping voltammetry (AdSV), the analyte forms a complex which is adsorbed to the working electrode.

In the subsequent stripping step, the deposit is brought back into solution, giving the analytical signal which is proportional to the deposited amount of analyte. In the case of ASV, the electrochemical reaction is the re-oxidation of the analyte during an anodic scan (Fig. 2). In the case of AdSV, the adsorbed metal complex is reduced during a cathodic scan.

Figure 1. Anodic stripping voltammetry (ASV) with Ag film modified scTrace Gold electrode – deposition of lead (solution stirred).

Figure 2. Anodic stripping voltammetry (ASV) with Ag film modified scTrace Gold electrode – stripping of lead (solution not stirred).

Both steps, deposition as well as stripping, are subject to the principles of kinetics and thermodynamics. Without going into detail, the result is simply that some analytes cannot be determined with certain electrode materials. One way to solve this problem is to modify an existing working electrode with a different material that is more suitable.

Applications

Lead in drinking water

Most of the lead which is present in surface and ground water is of anthropogenic origin, resulting from the leaching of contaminated soils. Lead in tap water, however, often originates from the household plumbing system. Pipes from lead metal were popular in some countries until the 1970s. Although Pb is barely soluble in water, it slowly dissolves in the presence of oxygen. As a result, the allowed limit for lead in tap water can be easily exceeded by a significant amount. Now lead pipes for municipal water transport are forbidden, but there are still houses with old installations intact. The WHO (World Health Organization) recommends a limit value for lead in drinking water of 10 µg/L. In the European Union, the upcoming limit is as low as 5 µg/L.

For the determination of lead, the scTRACE Gold electrode is modified with a silver film. The film is plated ex situ from a separate plating solution. Once plated, it can be used for multiple determinations. When the film is depleted, it can be removed, and then a fresh film is plated again. A side effect of the silver film is that the scTRACE Gold electrode lasts longer, since aging processes mainly affect the renewable silver film. In a repeatability study, determining 10 µg/L Pb with 3 different electrodes on 4 different days (total number of determinations = 10) the average recovery of Pb was 96% with a relative standard deviation of 5%.

Using the 884 Professional VA it is possible to measure lead concentrations in water down to 0.4 µg/L, allowing a simple and reliable determination of even the future limit in the European Union.

With the 946 Portable VA Analyzer, the limit of detection is only slightly higher: 0.6 µg/L. However, the mobile use offers the possibility for close monitoring of individual installations without the need to preserve samples and send them in to a central lab. Furthermore, the concerned resident gets an immediate result on the spot.

Free Application Note download: AN-V-214 Lead in drinking water – Straightforward determination by voltammetry using a gold microwire electrode.

If you want to learn more about our voltammetry product lines, lab as well as mobile, check out our website!

Nickel and cobalt in drinking water

Similar to lead, nickel concentrations present in water sources can be increased by human influence as well. Plumbing fixtures and faucets are often plated with a thin layer of nickel for protection against corrosion, even if the finish is made of chromium. Furthermore, nickel is part of many alloys from stainless steel to nickel brasses and bronze. Nickel steel alloy cookware or nickel pigmented dishes can also cause increased nickel levels. The maximum allowed level in drinking water in the European Union is 20 µg/L whereas the WHO recommends a limit of 70 µg/L.

For the voltammetric determination of nickel and cobalt, an ex situ plated bismuth film on the scTRACE Gold electrode is used as working electrode. Nickel as well as cobalt are determined in the form of their DMG (dimethylglyoxime) complex. This method had already proven its reliability with the mercury electrode, and therefore this application can now be transferred to a mercury-free electrode. With a detection limit of 1 µg/L with the 946 Portable Analyzer, and even lower at 0.2 µg/L with the 884 Professional VA lab instrument, the method is surely sufficient to monitor the compliance with legal requirements. The recovery for 1 µg/L Ni in a standard solution is about 99% (mean of 10 determinations) with a relative standard deviation of 5%.

Free Application Note download: AN-V-217 Nickel, cobalt in drinking water – Straightforward determination by voltammetry using a gold microwire electrode.

Chromium(VI) in drinking water

The problem of chromium(VI) in drinking water was brought to the attention of the general public with the movie «Erin Brockovich» in 2000, starring Julia Roberts. The plot is based on a true story, which happened in the small community of Hinkley, California, where the local energy provider contaminated the groundwater with the carcinogenic hexavalent chromium. The company attempted to cover up the incident, but an increased number of tumors and other health problems among the residents could finally be traced back to the contaminated drinking water.

Contamination with Cr(VI) in the environment is usually the result of improper handling of various industrial processes, especially abandoned waste dumped from galvanic chromium plating. The WHO recommends a maximum limit of 50 µg/L total chromium for drinking water

After modifying the scTRACE Gold electrode with an ex situ plated mercury film, Chromium(VI) can be determined as a complex with DTPA (diethylenetriaminepentaacetic acid). The recovery of a standard containing 30 µg/L Cr(VI) is 115% (mean of 3 determinations) with a relative standard deviation of 2%. Using the 946 Portable VA Analyzer it possible to determine concentrations down to 2 µg/L Cr(VI), allowing the on-site determination, providing immediate results without delay.

Free Application Note download: AN-V-230 Chromium(VI) in drinking water – Sensitive determination on the mercury film modified scTRACE Gold (DTPA method).

Summary

Talking about all of the applications that are possible with the scTRACE Gold electrode would go beyond the scope of this blog. The table here gives an overview of several elements for which methods with the scTRACE Gold are currently available from Metrohm. Your local Metrohm representative can assist in case of questions regarding the determination of one of the elements, or analysis in a specific matrix.

Figure 3. The scTRACE Gold electrode from Metrohm is suitable for trace analysis of several elements in water.

Overview: Applications with the scTRACE Gold
Element Application document
As(total) Application Note V-210
As(III) Application Note V-211
Hg Application Note V-212
Cu Application Note V-213
Pb Application Note V-214
Zn Application Note V-215
Tl Application Note V-228
Fe Application Note V-216
Ni, Co Application Note V-217
Bi Application Note V-218
Sb(III) Application Note V-229
Cr(VI) Application Note V-230

What’s next?

In Part 4 of this series, I will discuss the use of screen-printed electrodes (SPEs) which had already been introduced in the blog post «Virus detection using screen-printed electrodes». However, this time the focus will be on the determination of heavy metals using these disposable electrodes.

Post written by Barbara ZumbrägelProduct Manager VA/CVS at Metrohm International Headquarters, Herisau, Switzerland.

Trace metal analysis with solid-state electrodes – Part 3

Trace metal analysis with solid-state electrodes – Part 2

In the second part of our series on «heavy metal» analysis with solid-state electrodes, the focus lies on the scTRACE Gold electrode. Gold electrodes have been used in electrochemistry for decades. However, the scTRACE Gold has a very special design. Originally developed to improve the voltammetric determination of arsenic, the electrode has also proven to be suitable for the determination of a number of other elements, such as copper, iron, lead, and even the toxic chromium(VI).

How does it work?

The working electrode is a gold micro-wire (Fig. 1), which is thinner than a human hair. This special form of electrode leads to a very short initial preparation time. Different from other gold electrodes, the scTRACE Gold is ready for use within a few minutes.

Another advantage of this electrode is that it comes with the reference and the auxiliary electrode printed on the rear side of the sensor (Fig. 2). That does not only save on costs for the two additional electrodes required in a voltammetric system, it also makes maintenance for the reference electrode obsolete.

Figure 1. Close-up view of the gold micro-wire working electrode on the scTRACE Gold.

Figure 2. Close-up view of the reference and auxiliary electrode on the rear side of the scTRACE Gold.

Applications

The high level of sensitivity and a straightforward setup makes voltammetry a valuable tool in drinking water analysis.

Availability of clean drinking water is one of the major concerns of the 21st century. Besides microbiological contaminations, such as bacteria and viruses, the presence of heavy metals in drinking water can be a health risk. The first step in providing clean water is to identify contaminants, since health-threatening concentrations of heavy metals are not visible. For many heavy metals, limit values in drinking water are specified by authorities like the U.S. Environmental Protection Agency (EPA) or the European Commission. Water quality laboratories often use ICP (inductively coupled plasma) to monitor metal concentrations in drinking water.

Voltammetry is one of the few analysis techniques which offers a comparable sensitivity. Needing only basic infrastructure and low running costs, voltammetry is a viable alternative to monitor some key elements. In the following sections, some selected application examples are shown which demonstrate the capabilities of the scTrace Gold electrode in water analysis.

Arsenic in drinking water

Arsenic gained some global notoriety when water wells were built in Bangladesh to avoid diseases caused by microbiological contaminations in the surface water. Rather than suffering from cholera or hepatitis, people were instead afflicted with chronic arsenic poisoning.

It would be somewhat careless to believe that arsenic is only a problem in less developed countries. Actually, arsenic can be found nearly everywhere in the earth’s crust. Though as Paracelsus already knew, «the concentration makes the poison».

Therefore, the crucial question is how much of this arsenic finds its way into the water table. The WHO (World Health Organization) recommends a concentration of 10 µg/L arsenic as the maximum level in water that is intended for human consumption. This figure is also the legal limit in many countries.

Want to know more about arsenic? Then download our free article: «Arsenic – The multipurpose poison».

The voltammetric determination of the limit value of 10 µg/L shows a recovery of about 92% (n = 10 determinations) with a relative standard deviation of 6.5%. With a detection limit of 1 µg/L, which is one tenth of the legal limit, voltammetry using the scTRACE Gold electrode offers a reliable and cost-effective way of monitoring the arsenic content of drinking water.

For more information, download our free application note AN-V-210: Total arsenic in mineral water – Straightforward determination by voltammetry on a gold microwire electrode.

The scTRACE Gold electrode can be used with the 884 Professional VA as well as with the 946 Portable VA Analyzer. The 884 Professional VA is designed for laboratory use. The system is extremely flexible and can be adapted to user requirements. The modular setup also allows a later extension of the instrument from manual to fully automated.

As the name says, the 946 Portable VA Analyzer is intended for mobile use. It allows for on-site determination, directly at the sample source.

Copper in surface water

Under normal circumstances, copper in drinking water is not a problem. The legal limits are comparably high, WHO recommends a maximum concentration of 2 mg/L. An example from the field illustrates where the determination of copper in water can nevertheless be advisable.

The production of distilled alcoholic beverages (e.g., gin, whiskey, brandy, schnapps) involves single or multiple distillation of the raw material, which is done in copper stills. Cleaning out the copper apparatus and draining the rinsing water to a river can contaminate the environment with copper.

Although regulatory limits in effluents are usually higher than in drinking water, the copper limits can still be exceeded if the water is not treated properly prior to discharge. Since pollution from this cleaning is not a continuous process but only occurs periodically, it is difficult to detect and even harder to confirm, especially in less accessible areas.

Here, mobile voltammetry using the scTRACE Gold with the 946 Portable VA Analyzer can make a valuable contribution to the protection of the environment due to the reliable determination of low concentrations of copper.

For a concentration of 5 µg/L, the mean recovery of 10 determinations is approximately 107%, with a relative standard deviation of 2%. Concentrations down to 0.5 µg/L copper in the water can be determined directly at the point of sampling. This allows immediate re-sampling in case of suspicious results, and can furthermore help to locate the source of the pollution. In this way, chances increase to identify the source and hold the responsible entity accountable.

For more information, download our free application note AN-V-213: Copper in drinking water – Straightforward determination by voltammetry using a gold microwire electrode.

Iron in water

According to WHO, iron does not pose a health concern in levels typically found in drinking water. In contrast, it is an essential element for human nutrition. Nevertheless, many countries specify a maximum contaminant level between 200 µg/L and 300 µg/L.

The reason is simply that higher concentrations have a negative effect on the taste of the water, and will stain laundry and sanitary appliances. 

With a detection limit of 10 µg/L, the voltammetric determination of iron offers a straightforward method for monitoring the iron concentration of the water supply. The recovery of a voltammetric determination of 20 µg/L Fe is in the range of 91% (n = 10 determinations) with a relative standard deviation of 1%.

For more information, download our free application note AN-V-216: Iron in drinking water – Straightforward determination by voltammetry using a gold microwire electrode (DHN method).

What’s next?

In part two of this series, I introduced the scTRACE Gold electrode which I will also continue to discuss in Part 3. In the next installment, I will focus on applications which are carried out after electrochemical modification of the gold micro-wire.

Post written by Barbara ZumbrägelProduct Manager VA/CVS at Metrohm International Headquarters, Herisau, Switzerland.

Making a better beer with chemistry

Making a better beer with chemistry

Lager or ale? Pale ale or stout? Specialty beer, or basic draft? This week, to celebrate the International Beer Day on Friday, August 7th, I have chosen to write about a subject near and dear to me: how to make a better beer! Like many others, at the beginning of my adult life, I enjoyed the beverage without giving much thought to the vast array of styles and how they differed, beyond the obvious visual and gustatory senses. However, as a chemist with many chemist friends, I was introduced at several points to the world of homebrewing. Eventually, I succumbed.

Back in 2014, my husband and I bought all of the accessories to brew 25 liters (~6.5 gallons) of our own beer at a time. The entire process is controlled by us, from designing a recipe and milling the grains to sanitizing and bottling the finished product. We enjoy being able to develop the exact bitterness, sweetness, mouthfeel, and alcohol content for each batch we brew.

Over the years we have become more serious about this hobby by optimizing the procedure and making various improvements to the setup – including building our own temperature-controlled fermentation fridge managed by software. However, without an automated system, we occasionally run into issues with reproducibility between batches when using the same recipe. This is an issue that every brewer can relate to, no matter the size of their operation.

Working for Metrohm since 2013 has allowed me to have access to different analytical instrumentation in order to check certain quality attributes (e.g., strike water composition, mash pH, bitterness). However, Metrohm can provide much more to those working in the brewing industry. Keep reading to discover how we have improved analysis at the largest brewery in Switzerland.

Are you looking for applications in alcoholic beverages? Check out this selection of FREE Application Notes from Metrohm:

Lagers vs. Ales

There are two primary classes of beer: lagers and ales. The major contrast between the two is the type of yeast used for the fermentation process. Lagers must be fermented at colder temperatures, which lends crisp flavors and low ester formation. However, colder processes take longer, and so fermentation steps can last for some months. Ales have a much more sweet and fruity palate of flavors and are much easier to create than lagers, as the fermentation takes place at warmer temperatures and happens at a much faster rate.

Comparison between the fermentation of lagers and ales.

Diving a bit deeper, there are several styles of beer, from light pilsners and pale ales to porters and black imperial stouts. The variety of colors and flavors depend mostly on the grains used during the mash, which is the initial process of soaking the milled grains at a specific temperature (or range) to modify the starches and sugars for the yeast to be able to digest. The strain of yeast also contributes to the final flavor, whether it is dry, fruity, or even sour. Taking good care of the yeast is one of the most important parts of creating a great tasting beer.

Brewing terminology

  • Malting: process of germinating and kilning barley to produce usable sugars in the grain
  • Milling: act of grinding the grains to increase surface area and optimize extraction of sugars
  • Mashing: releasing malt sugars by soaking the milled grains in (hot) water, providing wort
  • Wort: the solution of extracted grain sugars
  • Lautering: process of clarifying wort after mashing
  • Sparging: rinsing the used grains to extract the last amount of malt sugars
  • Boiling: clarified wort is boiled, accomplishing sterilization (hops are added in this step)
  • Cooling: wort must be cooled well below body temperature (37 °C) as quickly as possible to avoid infection
  • Pitching: prepared yeast (dry or slurry) is added to the cooled brewed wort, oxygen is introduced
  • Fermenting: the process whereby yeast consumes simple sugars and excretes ethanol and CO2 as major products

Ingredients for a proper beer

These days, beer can contain several different ingredients and still adhere to a style. Barley, oats, wheat, rye, fruit, honey, spices, hops, yeast, water, and more are all components of our contemporary beer culture. However, in Bavaria during the 1500’s, the rules were much more strict. A purity law known as the Reinheitsgebot (1516) stated that beer must only be produced with water, barley, and hops. Any other adjuncts were not allowed, which meant that other grains such as rye and wheat were forbidden to be used in the brewing process. We all know how seriously the Germans take their beer – you only need to visit the Oktoberfest once to understand!

Determination of the bitterness compounds in hops, known as «alpha acids», can be easily determined with Metrohm instrumentation. Check out our brochure for more information:

You may have noticed that yeast was not one of the few ingredients mentioned in the purity law, however it was still essential for the brewing process. The yeast was just harvested at the end of each batch and added into the next, and its propagation from the fermentation process always ensured there was enough at the end each time. Ensuring the health of the yeast is integral to fermentation and the quality of the final product. With proper nutrients, oxygen levels, stable temperatures, and a supply of simple digestible sugars, alcohol contents up to 25% (and even beyond) can be achieved with some yeast strains without distillation (through heating or freezing, as for eisbocks).

Improved quality with analytical testing

Good beers do not make themselves. For larger brewing operations, which rely on consistency in quality and flavor between large batch volumes as well as across different countries, comprehensive analytical testing is the key to success.

Metrohm is well-equipped for this task, offering many solutions for breweries large and small.

Don’t take it from me – listen to one of our customers, Jules Wyss, manager of the Quality Assurance laboratory at Feldschlösschen brewery, the largest brewery in Switzerland.

«I have decided to go with Metrohm, because they are the only ones who are up to such a job at all. They share with us their huge know-how.

I can’t think of any other supplier who would have been able to help me in the same way

Jules Wyss

Manager Quality Assurance Laboratory, Feldschlösschen Getränke AG

Previous solutions failed

For a long time, Jules determined the quality parameters in his beer samples using separate analysis systems: a titrator, HPLC system, alcohol measuring device, and a density meter. These separate measurements involved a huge amount of work: not only the analyses themselves, but also the documentation and archiving of the results all had to be handled separately. Furthermore, Jules often had to contend with unreliable results – depending on the measurement procedure, he had to analyze one sample up to three times in order to obtain an accurate result.

A tailor-made system for Feldschlösschen

Jules’ close collaboration with Metrohm has produced a system that takes care of the majority of the necessary measurements. According to Jules, the system can determine around 90% of the parameters he needs to measure. Jules’ new analysis system combines various analysis techniques: ion chromatography and titration from Metrohm as well as alcohol, density, and color measurement from another manufacturer. They are all controlled by the tiamo titration software. This means that bitterness, citric acid, pH value, alcohol content, density, and color can all be determined by executing a single method in tiamo.

Measurement of the overall water quality as well as downstream analysis of the sanitization process on the bottling line is also possible with Metrohm’s line of Process Analysis instrumentation.

Integrated analytical systems with automated capabilities allow for a «plug and play» determination of a variety of quality parameters for QA/QC analysts in the brewing industry. Sample analysis is streamlined and simplified, and throughput is increased via the automation of time-consuming preparative and data collection steps, which also reduces the chance of human error.

Something to celebrate: The Metrohm 6-pack (2018)

In 2018, Metrohm celebrated its 75 year Jubilee. At this time, I decided to combine my experience as a laboratory analyst as well as a marketing manager to brew a series of six different styles of beer for the company, as a giveaway for customers of our Metrohm Process Analytics brand, for whom I worked at the time. Each batch was brewed to contain precisely 7.5% ABV (alcohol by volume), to resonate with the 75 year anniversary. The array of ales was designed to appeal to a broad audience, featuring a stout, porter, brown ale, red ale, hefeweizen, and an India pale ale (IPA). Each style requires different actions especially during the mashing process, based on the type of grains used and the desired outcome (e.g., flavor balance, mouthfeel, alcohol content).

Bespoke bottle caps featuring the Metrohm logo.
The 6 styles of beers brewed as a special customer giveaway to celebrate the Metrohm 75 year Jubilee.

Using a Metrohm Ion Chromatograph, I analyzed my home tap water for concentrations of major cations and anions to ensure no extra salts were needed to adjust it prior to mashing. After some of the beers were prepared, I tested my colleagues at Metrohm International Headquarters in the IC department, to see if they could determine the difference between two bottles with different ingredients:

Overlaid chromatograms from IC organic acid analysis highlighting the differences between 2 styles of the Metrohm 75 year Jubilee beers.

The IC analysis of organic acids and anions showed a clear difference between the beers, allowing them to determine which sample corresponded to which style, since I did not label them prior to shipping the bottles for analysis. As the milk stout contained added lactose, this peak was very pronounced and a perfect indicator to use.

Metrohm ion chromatography, along with titration, NIRS, and other techniques, allows for reliable, comprehensive beer analysis for all.

In conclusion, I wish you a very happy International Beer Day this Friday. Hopefully this article has illuminated the various ways that beer and other alcoholic beverages can be analytically tested for quality control parameters and more  fast, easy, and reliably with Metrohm instrumentation.

For more information about the beer quality parameters measured at Feldschlösschen brewery, take a look at our article: «In the kingdom of beer The largest brewery in Switzerland gets a made-to-measure system». Cheers!

Read the full article:

«In the kingdom of beer – The largest brewery in Switzerland gets a made-to-measure system»

Post written by Dr. Alyson Lanciki, Scientific Editor (and «chief brewing officer») at Metrohm International Headquarters, Herisau, Switzerland.

Combat food fraud: Meet Misa

Combat food fraud: Meet Misa

What’s on your plate?

Food fraud is an ever-present danger around the world. Despite increased regulations, huge scandals still occur regularly, such as deliberately tainted infant formula (2008), or the horse meat affair in the UK due to improper labelling (2013). Other more common examples include the adulteration of highly valued items with lower cost substitutes, or the illegal enhancement of color in foods and beverages with unsafe dyes.

As the population continues to increase, driving the demand for high quality food and beverage choices, so will the amount of food fraud cases. Only a concerted effort to test foodstuffs more frequently in an efficient manner along the supply chain with accurate and precise analytical techniques will bring these cases to light before more people come to harm.

Misa to the rescue

Meet the newest addition to the Metrohm Instant Raman Analyzer family: Misa, the Metrohm Instant SERS Analyzer. Misa is fast, smart, and portable with powerful algorithms that simplify high-tech analyses for non-technicians. Misa is designed with safety in mind, purposefully designed to detect illicit drugs and food additives in complex matrices.

The SERS Principle

Surface Enhanced Raman Scattering (SERS) is an extension of Raman. Perhaps you read in my previous blog post about Raman spectroscopy that «If you can see it, Raman can ID it»… well, SERS amplifies the Raman signal of trace analytes, making it an extremely sensitive method for «ID when you can’t see it.»

When SERS-active analytes adsorb to silver or gold nanoparticles, their Raman signal is enhanced as much as a million-fold, providing incredibly sensitive detection abilities.

SERS is used in biosensor applications, including single-cell sensing, antibody detection, and pathogen monitoring. It can be used to detect chemical warfare agents and illicit drug laboratory residues. Additionally, SERS is a particularly powerful technique for detecting trace contaminants in foodstuffs such as antibiotics fungicides, pesticides, herbicides, illicit dyes, and other additives.

If you know ID Kit for Mira DS, then you already know a little about SERS. SERS is an «enhancement» technique to Raman that enables detection of trace materials. For example, ID Kit was developed as a method for identifying heroin and fentanyl in street drug samples. The cutting agents and added stimulants that constitute the bulk of street heroin fluoresce under investigation with Raman and overwhelm the signal coming from heroin. SERS sees right through the cutting agents and identifies the drug.

Overlaid Raman and SERS spectra demonstrating the ability of SERS to detect the active ingredient in street heroin.

Another example of how Raman and SERS complement each other can be seen with Yaba, a common street drug in southeast Asia. Yaba is a red tablet that contains significant caffeine with a small amount of methamphetamine. When a red Yaba tablet is analyzed with Raman, caffeine and the red dye in the coating are the primary identification targets. This makes sense, because Raman is very good at identifying bulk materials.

However, when a Yaba tablet is subjected to SERS analysis, the story is very different (reminder: these are both also capabilities of Mira DS!) Only SERS can ID the methamphetamine in Yaba and complete the story.

Protecting Consumer Safety with Misa

Consumer safety relies on the ability of food inspectors to detect unwanted additives and assure the quality of the products. Trace detection of food adulterants is traditionally very involved laboratory work, using HPLC, GC/MS, and other techniques requiring extensive sample preparation and scientific training. Misa is designed to simplify food testing, from sample preparation, to sharing results.

The unique capabilities of Misa and SERS analysis in food testing deserve some explanation. Raman is used in food testing in some incredible ways: identifying counterfeit honey, distinguishing scotch from different producers, discriminating between very similar sugars, even making a distinction between grass- and grain-fed beef. However, these are bulk, inherent qualities of a food.

Looking for trace levels of pesticides is a very different science. A successful SERS analyte must interact with nanoparticles—target molecules with amine, carboxyl, and thiol groups often have the required interaction. Fortunately, many food additives fit this definition. Metrohm Raman sponsored a year-long study to identify 82 different food adulterants that can be successfully detected with our SERS substrates. That was just the beginning.

Are you looking for applications suitable for Misa? Check out our free selection of application notes available on the Metrohm website: 

Additionally, reference spectra for several other analytes can be obtained by contacting your local Metrohm  sales organization. 

The next step was to determine the foods which were typically treated with these illicit substances, then how to simplify sample preparation for potentially demanding food matrices. Metrohm Raman is taking two different approaches to this challenge. First, Misa will be released with 17 different «real world» food safety applications (click to download):

Misa is a unique instrument, which is reflected in this broad collection of Application Notes (AN). In addition to standard spectra and experiments, each AN includes a special section titled «Field Test Protocol». Briefly, the Field Test Protocol guides any user through a complete experiment using Misa and the tools in the ID Kits. ID Kits for Misa contain dedicated SERS substrates, in addition to the basic tools required for field testing. These, combined with companion Operating Procedures included on Misa, make food safety testing accessible to anyone, anywhere.

Our second approach to application development for Misa is a very interactive process with our users as we identify the target and food matrix, provide standard spectra for library building, advise sample preparation, and help to optimize results. This approach acknowledges that food is different around the world, adulterants vary, and concerns may be localized. These ANs that accompany Misa at release are intended to give the user an idea of how to use SERS and when it is a useful technique for detection of food contaminants, but custom applications will certainly increase demand for Misa.

Metrohm Raman is excited to introduce you to Misa. Misa has all of the qualities that you appreciate about Mira—intuitive user interface, simple guided workflow, and smart attachments to facilitate onsite testing by non-chemists. Our approach to simplifying food testing includes libraries, dozens of reference spectra, and developed applications targeting food adulterants.

Visit our website

and discover more about how Misa can help the fight against food adulteration scandals.

Post written by Dr. Melissa Gelwicks, Technical Writer at Metrohm Raman, Laramie, Wyoming (USA).

Comprehensive water analysis: combining titration, IC, and direct measurement in one setup

Comprehensive water analysis: combining titration, IC, and direct measurement in one setup

If you perform water analyses on a regular basis, then you know that analyzing different parameters for drinking water can be quite time-consuming, expensive, and it requires significant manual labor. In this article, I’d like to show you an example of wider possibilities in automated sample analysis when it comes to combining different analytical techniques, especially for our drinking water.

Water is the source and basis of all life. It is essential for metabolism and is our most important foodstuff.

As a solvent and transporting agent it carries not only the vital minerals and nutrients, but also, increasingly, harmful pollutants, which accumulate in aquatic or terrestrial organisms.

Within the context of quality control and risk assessment, there is a need in the water laboratory for cost-effective and fast instruments and methods that can deal with the ever more complex spectrum of harmful substances, the increasing throughput of samples, and the decreasing detection limits.

Comprehensive analysis of ionic components in liquid samples such as water involves four analytical techniques:

  • Direct measurement
  • Titration
  • Ion chromatography
  • Voltammetry

Each of these techniques has its own particular strengths. However, applying them one after the other on discrete systems in the laboratory is a rather complex task that takes up significant time.

Back in 1998, Metrohm accepted the challenge of combining different analytical techniques in a single fully automated system, and the first TitrIC system was introduced.

What is TitrIC?

The TitrIC system from Metrohm combines direct measurement, titration, and ion chromatography in a fully automated system.

Direct measurements include temperature, conductivity, and pH. The acid capacity (m and p values) is determined titrimetrically. Major anions and cations are quantified by ion chromatography. Calcium and magnesium, which are used to calculate total hardness, can be determined by titration or ion chromatography.

The results are displayed in a common table, and a shared report is given out at the end of the analysis. All methods in TitrIC utilize the same liquid handling units and a common sample changer.

For more detailed information about the newest TitrIC system, which is available in two predefined packages (TitrIC flex I and TitrIC flex II), take a look at our informative brochure:

Efficient: Titrations and ion chromatography are performed simultaneously with the TitrIC flex system.

Figure 1. Flowchart of TitrIC flex II automated analysis and data acquisition.

How does TitrIC work?

Each water sample analysis is performed fully automated at the push of a button—fill up a sample beaker with the sample, place it on the sample rack, and start the measurement. The liquid handling units transfer the required sample volume (per measurement technique) for reproducible results. TitrIC carries out all the work, and analyzes up to 175 samples in a row without any manual intervention required, no matter what time the measurement series has begun. The high degree of automation reduces costs and increases both productivity and the precision of the analysis.

Figure 2. The Metrohm TitrIC flex II system with OMNIS Sample Robot S and Dis-Cover functionality.

To learn more about how to perform comprehensive water analysis with TitrIC flex II, download our free application note AN-S-387:

Would you like to know more about why automation should be preferred over manual titration? Check out our previous blog post on this topic:

Calculations with TitrIC

With the TitrIC system, not only are sample analyses simplified, but the result calculations are performed automatically. This saves time and most importantly, avoids sources of human error due to erroneously noting the measurement data or performing incorrect calculations.

Selection of calculations which can be automatically performed with TitrIC: 

  • Molar concentrations of all cations
  • Molar concentrations of all anions
  • Ionic balance
  • Total water hardness (Ca & Mg)
  • … and more

Ionic balances provide clarity

The calculation of the ion balance helps to determine the accuracy of your water analysis. The calculations are based on the principle of electro-neutrality, which requires that the sum in eq/L or meq/L of the positive ions (cations) must equal the sum of negative ions (anions) in solution.

TitrIC can deliver all necessary data required to calculate the ion balance out of one sample. Both anions and cations are analyzed by IC, and the carbonate concentration (indicative of the acid capacity of water) is determined by titration.

If the value for the difference in the above equation is almost zero, then this indicates that you have accurately determined the major anions and cations in your sample.

Advantages of a combined system like TitrIC

  • Utmost accuracy: all results come from the same sample beaker

  • Completely automated, leaving analysts more time for other tasks

  • One shared sample changer saves benchtop space and costs

  • Save time with parallel titration and IC analysis

  • Flexibility: use titration, direct measurement, or IC either alone or combined with the other techniques

  • Single database for all results and calculation of the ionic balance, which is only possible with such a combined system, and gives further credibility to the sample results

Even more possibility in sample analysis

TitrIC has been developed especially for automated drinking water analysis but can be adapted to suit any number of analytical requirements in food, electroplating, or pharmaceutical industries. Your application determines the parameters that are of interest.

If the combination of direct measurement, titration, and IC does not suit your needs, perhaps a combination of voltammetry and ion chromatography in a single, fully automatic system might be more fitting. Luckily, there is the VoltIC Professional from Metrohm which fulfills these requirements.

Check out our website to learn more about this system:

As you see, the possibility of combining different analysis techniques is almost endless. Metrohm, as a leading manufacturer of instruments for chemical analysis, is aware of your analytical challenges. For this reason, we offer not only the most advanced instruments, but complete solutions for very specific analytical issues. Get the best out of your daily work in the laboratory!

Discover even more

about combined analytical systems from Metrohm

Post written by Jennifer Lüber, Jr. Product Specialist Titration/TitrIC at Metrohm International Headquarters, Herisau, Switzerland.