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Save money by using automated titration systems

Save money by using automated titration systems

Perhaps you read my last blog entry: «Why consider automation – even for simple titrations» and liked the idea of disengaging yourself from the tedious, repetitive, and exhausting manual routine lab work by automating analyses and increasing the accuracy and reproducibility of your results at the same time.

Titration is known to be a bargain analytical method, as a glass buret or even a simple stand-alone titrator are quite inexpensive in comparison with other techniques such as spectroscopy or chromatography. In combination with the short determination time and results based on a known stoichiometry, titration is well-accepted in laboratories worldwide as a primary method.

Nevertheless, the increasing sample throughput in the last decades shows more and more why it is worth it to automate lab analysis. On many occasions, I had discussions with lab managers or purchasing agents who had doubts about buying an automation system for the «cheap» titration technique. These concerns are understandable, especially when adding automation to the titrator can cost the same as the titration installation, or even more. However, consider not only the costs for such an upgrade but also the many benefits.

I will now explain how the usage of a fully automated titration system can result in various savings.

 

Save valuable time

Time savings is one of the biggest benefits when using walk-away automation in the lab.

After preparing the sample and entering the required sample data into the controlling device, the system can run unattended for several hours or even days. During this time, lab technicians can spend their valuable time on samples that cannot be automated, evaluating data, preparing new samples, and documentation or inventing new methods or substances.

Don’t waste money on repetitions

In comparison to only using a stand-alone titrator, the automated system can reduce costs for repetitions. Due to the fact that the procedures have been tested before they are run autonomously, handling errors can be reduced to a minimum during the determination. These are typical tasks such as ensuring the sensor and buret tips are sufficiently covered by the sample solution, using the optimum stirring speed for the sample, as well as applying standardized cleaning procedures in between the analyses.

At first glance, these steps might not seem so important, but these have an impact if each lab technician involved in the analysis performs it in a slightly different manner based on their preference and experience. In the worst case, samples have to be repeated more often to prove the validity of the result. With automation, you no longer have to worry about this issue.

Reduce running expenses

The improved handling procedures mentioned above will reduce the costs for consumables such as electrodes. Thanks to the previously defined cleaning, conditioning, and storage procedures, the sensor lasts much longer. The only thing you have to consider is filling the electrolyte reservoir on a regular basis, which can not yet be automated.

However, if you are only running routine pH measurements, a solution already exists for this: the Ecotrode Gel, which allows you to run continuous measurements without any refilling until the electrolyte is exhausted.

The transparency of the electrolyte gel will show when it is time to change the electrode. Cool, isn’t it? 

Besides the electrodes, reagents and eventual waste disposal are topics that have to be taken into account when discussing the costs per analysis of an analytical device. Unfortunately, there are still several norms and standards using absurd amounts of organic solvents. All of these chemicals need a special treatment for proper disposal, i.e. the more waste solution produced, the higher the costs for its disposal—not to mention the impact on the environment.

In automated systems, the amount of these reagents can be reduced to a minimum as analyses can be carried out in beakers with a smaller diameter and perfectly positioned electrodes. Depending on the application, you can even reduce the cleaning procedure between the analyses to a simple dip in solvent rather than showering the electrode with an excess of solvent.

Fewer accidents thanks to walk-away automation

As an automated titration system runs independently for several hours or even overnight, the direct contact with harmful substances and reagents is already minimized. Modern titration systems do not only take over the analysis, but also guarantee the sample beakers are already pre-cleaned before you remove them from the system to put them in the dishwasher or dispose of them.

Even minimizing exposure to chemicals during the exchange of the reagents is possible if your system is equipped with 3S technology, which makes titrant change simpler than ever. The safer the system, the smaller the risk of exposure to hazardous chemicals while handling during sample analysis or disposal. 

We all know that an accident is one thing, but the administration afterwards can also be a real nightmare. Therefore, it is better to avoid situations prone to causing accidents, as it keeps people healthy and the associated costs down.

Increase your profit

Increasing the sample throughput has a direct impact on your profit. Without automation, more analysts are needed to handle the increasing number of samples, but finding well-educated lab technicians becomes ever more challenging and costly. Furthermore, boring routine titration analysis is not the work that lab staff desires.

Automation – not as expensive as you may have thought

Perhaps you started reading this blog post thinking that automation is too expensive for your lab, especially compared to the investment for a simple stand-alone titrator. However, as shown in this article, several kinds of savings can be achieved using an automated titration system.

Consider your regular expenses for consumables, reagents, and time spent for repeated analyses. How often were the results not available either fast or good enough for the production to continue? Think about discussions on safety in the lab when a colleague was injured. Also, how often was the efficiency and profitability of your lab questioned due to the running costs? Considering this, you will see the return on investment is unbelievably good with automation. The more samples you perform fully automated, the faster the initial investment pays off and creates better financial statements for you.

At Metrohm, we don’t just sell titrators. We provide titration solutionsWe offer systems as sophisticated or as straightforward as you need them. Titrator, accessories, electrodes, sample changers, and software – all from a single source.

Looking for a titrator?

Check out our selection here!

Post written by Heike Risse, PM Titration (Automation) at Metrohm International Headquarters, Herisau, Switzerland.

Why consider automation – even for simple titrations

Why consider automation – even for simple titrations

If you are reading this blog post, you are most likely already familiar with the general principles of potentiometric titration. Although chromatographic and spectroscopic methods are preferred in many labs, titration is still “the” method for analysis of all kinds of sample types. Titration stands apart from other techniques because it is an absolute method (also known as a primary method). Whenever the analyte reacts in a known stoichiometric way with another reagent, titration is the method of choice, not only for official norms and standards.

Nowadays, titration is far more modern than it was back when I was a student. At that time we still used glass burets and color indicators, and suffered from inconsistent results. Although the automatic addition of the titrant and the recognition of the equivalence point are now performed by the titrator itself in most labs, there are still many manual steps that can go wrong and lead to unreliable results.

If the used titrator is a stand-alone type, the analysis becomes a full-time job for the lab technician. Not only must the sample be prepared, the titration itself has to be started after the sensor and buret tip have been placed in the sample solution. If using a titrator, the addition of the titrant as well as evaluation and calculation of the results will be done automatically. However, cleaning after each finished determination and preparation for the next sample still remains the task of the lab technician. In many cases, the titration does not take much longer than 3–5 minutes. Due to this short period, there are not many other tasks which can be completed by the technician during the analysis time.

Using a fully automated titration system results in not only more efficient analyses, but achieves better and even more reproducible ones at the same time. Let’s find out how!

Save valuable time

Time savings is one of the biggest benefits of using automation. To get a better idea about the general amount of time that can be saved, have a closer look at this diagram. You can already see how many steps can be done by an automated titration system, leaving analysts more time for other tasks.

A proper analysis starts with the correct liquid handling.

Sample determination in titration can consist of several manual steps beyond the addition of the titrant. Depending on the type of sample and analysis, different kinds of sample preparation steps are required. The most common ones are the manner of sampling itself, dilution, auxiliary reagent addition, pH, or temperature adjustment.

Taking the correct amount of representative sample can already be quite a demanding task. For many applications, the sample is weighed if it is solid (e.g., powder or tablets), but this does not work for all sample types. Liquids are normally measured using measuring cylinders or pipets. These are very accurate and helpful tools if the user knows how to handle them correctly.

As long as the same person is performing the sampling, the results should be very reproducible, but in most labs this is not the case. Usually more than one person is responsible for the same analysis due to shift work, which can result in differing or less reproducible results.

With fully automated volumetric sampling, the only thing you need to care about is making sure enough sample is placed in the sample beaker! The connected dosing device is able to pipet the requested sample amount very accurately to the titration cell. The big advantages of using an automated pipetting system is its flexibility (e.g., even 3.75 mL can be pipetted fully automatically). Due to its independence of the user, the sampling and the results become much more reproducible.

Dilution / Addition of auxiliary reagents

In many cases, the sample amount needed for the analysis is not sufficient enough to put the sensor directly in and begin analysis. Often deionized water (or another suitable solvent) is added to reach a sufficient volume for the sensors to be placed in.  As titration is an absolute method, the amount of added solvent has no impact on the titration results, as long as the solvent does not react in the same way as the sample does with the titrant. 

A typical example is the solvents used for TAN/ TBN analysis in the petrochemical industry. Here, it is important to measure the amount of added solvent accurately and make sure to determine the blank value in advance. 

There are quite a few other applications where an accurate amount of reagent must be added: e.g., to start or stop a reaction, preparing back titrations, or for general pH adjustments before the final titration can take place.

For these tasks, measuring cylinders and pipets are normally used, but this is often tedious and can lead to mistakes, especially if many samples have to be analyzed. These days, many stand-alone titrators already offer the possibility to automatically and accurately add reagents, including the titrant. Repetitive (and annoying!) manual preparation steps therefore no longer occupy the lab technician.

Since reagent addition is part of the sample determination procedure, these added volumes can be documented much easier and more accurately, meaning less trouble when it comes to the analysis procedure traceability.

So, how good can such a buret be? Metrohm offers burets with a resolution of 100,000 pulses where even minute volumes can be dosed with extreme accuracy. For example, when using a 50 mL cylinder unit we are speaking about 0.5 µL per pulse.

 

The best liquid handling is not good enough if the sensor measures incorrectly.

The heart of each titration or measurement is the chosen sensor. It is especially important in potentiometric titrations that both measuring and reference electrodes are properly cleaned, and if necessary, also conditioned between analyses. Otherwise, false equivalence points might be indicated, or instable curves will be shown, which leads to inaccurate and unreproducible results. Therefore, proper sensor maintenance is also important. Although many lab technicians are trained about handling the electrode correctly, some things may be forgotten after some time and this is where the trouble starts.

Quite often it takes some time before realizing that the wrong electrode treatment is the reason for the differing results. Several issues could be cleared up due to either the absence of electrode cleaning/conditioning or perhaps the cleaning step was not long enough. Similar to the titration itself, the manual cleaning steps also depend on the user performing this task. With an automated setup, this can be easily avoided as the electrode is treated in the exact same way for each determination. Additionally, automating the titration guarantees that the sensor is always properly stored, even if the sample series finishes in the middle of the night when no one is in the lab to do this.

In the blog entry «Avoiding the most common mistakes in pH measurement» you will find more useful hints for correct sensor handling in general.

 Last but not least, a well-treated electrode not only gives you outstanding results, but also lasts much longer and reduces the costs of consumables.

Automation rocks – even for simple titration applications.

Here I have explained several reasons to consider automation even for simple titration applications. By including as many sample preparation steps as possible directly into the analysis run, this guarantees that each sample is treated exactly the same way, along with a better documentation process. Not only is there a reduction in handling errors during sampling, liquid handling, and electrode treatment, but as a result of these the reproducibility will be increased. On top of this, lab technicians are no longer occupied with annoying routine sample preparation/determinations, but have more time for reporting tasks or other analyses which are not automated – i.e. the laboratory throughput increases.

Post written by Heike Risse, PM Titration (Automation) at Metrohm International Headquarters, Herisau, Switzerland.

To automate or not to automate? Advantages of PAT: Part 1

To automate or not to automate? Advantages of PAT: Part 1

I have to admit that the technological world of process analysis seemed foreign for me for a while. When I first heard about process automation, I imagined futuristic robots that do the work, similar to modern science fiction films. Perhaps many people might have the same impression.

There is often a great deal of uncertainty about what the expression «we automate your process» actually means. In this blog series, I want to show you that process analytical technology (PAT) is less complicated than expected and offers several advantages for users.

What does process analytical technology (PAT) mean? 

I was once told in conversation:

«Process analytics is for everyone who believes that they don’t need it.»

There is definitely truth in this statement, and it certainly shows the abundance of application possibilities. At the same time, it should be considered that in the future, users of process analytical technology will not only invest in conventional measurement technologies (e.g., direct measurement, TDLAS, GC), but also increasingly in the determination of substance properties and material compositions.

Pollution (gases and aerosols) in ambient air are especially harmful to human health. These substances can continuously and reliably be monitored by process analyzers.

PAT serves to analyze, optimize, and ultimately control processes and their critical parameters. This control makes a major contribution to quality assurance and the overall process reliability at the manufacturer. Thinking back to some well-known chemical disasters (e.g. Minamata, Toulouse, or Tianjin) in which poisonous substances were released, causing immense damage to people and the environment, the importance regarding regular monitoring of critical parameters becomes abundantly clear. The list of analytes that can and must be monitored is long, ranging from contamination in wastewater due to municipal or industrial wastewater treatment plants, to pharmaceutical agents, to gases and aerosols in the ambient air.

From Lab to Process

Considering the history of manufacturing and other industrial processes, it is clear that the ultimate goal is to increase throughput in ever-shorter timeframes, with an eye on safety measures and minimization of costs where possible. Independence through automation and fast, reliable data transfer is a high priority.

In order to make the process economically viable along the entire value chain, the resulting products should be manufactured at the highest quality in a short time and with minimal raw material and energy usage. For 24/7 operations in particular, knowledge of the composition of the starting materials and intermediate products (or rather, any impurities) is essential for optimal process control and reliability.

How can reliable process monitoring be ensured around the clock? Very few companies have company laboratories with an actual 3-shift operation, and often send their samples to external laboratories. Additionally, the samples are sometimes taken with longer time intervals between them. This carries various risks.

On one hand, the time lost between the sampling event and receiving the results from the analysis is enormous. It is only possible to react to fluctuations and deviations from target concentrations or limit values ​​with a certain delay. On the other hand, working and environmental conditions are not comparable and can lead to changes in the sample. Oxidation, pressure or temperature changes, introduction of moisture, and many other factors can change a sample’s original properties during transport, waiting periods, and manual laboratory analysis.

Example trend graph comparing process deviations mitigated by manual control (grey) and fully automatic process control (orange) via PAT.

Process analyzers: automated operation around the clock

Analyses, which are usually carried out manually, are automated by using industrial process analyzers. The samples are automatically removed from critical points in the production process and processed further. The information obtained is used to control the process without any delay, as the data can be transferred immediately to a central computing system at the plant. Automated analysis right at the sample point allows for increased accuracy and reproducibility of the data.

In practice, this entails rerouting a partial stream from the process in question to be fed to the analyzer by means of valves, peristaltic pumps, or bypass lines. Each sample is therefore fresh and correlates to the current process conditions. Probes can also be integrated directly into the process for continuous inline measurement.

The analysis is performed using common titration, spectroscopy, ion chromatography, or electrochemical methods known from the laboratory, which are optimally integrated into the process analyzer for each individual application requirement. The methods can be used in combination, allowing several measuring points to be monitored in parallel with one system. Thanks to the process analyzers that are specifically configured and expandable for the application, the optimal conditions for stable process control are obtained.

Spectroscopic methods have become particularly well-established in recent years for process analysis and optimization purposes. In contrast to conventional analysis methods, near-infrared (NIR) spectroscopy shows a number of advantages, especially due to the analysis speed. Results can be acquired within a few seconds and transferred directly to the chemical control system so that production processes can be optimized quickly and reliably. Samples are analyzed in situ, completely without the use of chemicals, in a non-destructive manner, which means further added value for process safety.

The many advantages of PAT

Automation in the context of process analysis technology does not always have anything to do with futuristic robots. Instead, PAT offers companies a number of advantages:

 

  • Fully automatic, 24/7 monitoring of the process
  • Timely and automatic feedback of the analysis results to the system control for automatic process readjustment
  • Reduction in fluctuations of product quality
  • Increased process understanding to run production more efficiently
  • Independent of your own laboratory (or contract lab)
  • Complete digital traceability of analysis results
  • Total solution concepts including sample preconditioning, saving time and increasing safety

What’s next?

In our next post in this series, you will discover the role process analysis technology plays in digital transformation with regard to «Industry 4.0».

Want to learn more about the history of process analysis technology at Metrohm? Check out our previous blog post:

Read what our customers have to say!

We have supported customers even in the most unlikely of places⁠—from the production floor to the desert and even on active ships!

Post written by Dr. Kerstin Dreblow, Product Manager Wet Chemical Process Analyzers, Deutsche Metrohm Prozessanalytik (Germany), with contributions from Dr. Alyson Lanciki, Scientific Editor at Metrohm International Headquarters (Switzerland).

How Mira Became Mobile

How Mira Became Mobile

Handheld Raman spectrometers are truly like no other analytical chemical instruments. All spectrometers (e.g. IR/NIR, UV-Vis, GC/MS, and Raman) rely on interactions between matter and energy and include detectors that collect information about resulting atomic and molecular changes. This information is used to qualify and/or quantify various chemical species. Typically, a spectrometer is a benchtop instrument attached to a computer or other visual display that is used by an analytical chemist in a laboratory.

Classical Raman spectrometers fall into this category. Lasers, filters, detectors, and all associated hardware for sampling is combined in one unit, while data processing and viewing occurs nearby.

For a comparison of other spectroscopic techniques, visit our previous blog post «Infrared spectroscopy and near infrared spectroscopy – is there a difference?».

Raman is a unique investigative analytical technique in many ways. It is said, «If you can see it, Raman can ID it.»

Indeed, Raman’s strengths are its simple sampling methods combined with its specificity. Direct analysis is possible for many pure substances without sample preparation. Sampling is performed via direct contact with a substance, remotely, or through a barrier. Even solutes in water may be directly identified. This technique is highly specific; each material investigated with Raman produces a unique «fingerprint» spectrum. Raman spectroscopy is successful at positively identifying each distinct substance, while accurately rejecting even very similar compounds.

Mira (Metrohm Instant Raman Analyzer) with several sampling attachments for easy analysis: with or without sample contact.

The Raman spectrum

Raman spectra contain peaks across a range that correspond to specific molecular connectivity and can be used to determine the composition of a sample. The spectral range is dependent on spectrometer design, and embodies a balance of resolution and sensitivity.

The «fingerprint region» (400–1800 cm-1) is used to ID unknowns and verify known materials. The region below 400 cm-1 is helpful in the analysis of minerals, gemstones, metals, and semiconductors. For most organic materials (oils, polymers, plastics, proteins, sugars/starches, alcohols, solvents, etc…), very little information above 2255 cm-1 is useful in Raman applications, as carbon-hydrogen chains contribute little to molecular qualification.

A selection of different bonds and functional groups with their general regions of activity in the Raman portion of the electromagnetic spectrum (click to enlarge).

Mira’s measuring range of 400–2300 cm-1 is perfect for most Raman applications, including:

  • Pharma & Other Regulated Industries
  • Food
  • Personal Care & Cosmetics
  • Defense & Security
  • Process Analytics
  • Materials ID
  • Education & Research

Mira is available in different configurations for all kinds of applications and user needs.

Good things come in small packages

Technology, analysis, ease of use, accuracy—handheld Raman has all of this in a small format that escapes the confines of the lab. It also invites many new types of users who employ Raman for vastly new and exciting applications. In the rest of this blog post, I share details about the development of components that led to miniaturization of Raman. This is followed by the origin story of Metrohm Raman, manufacturer of Mira (Metrohm Instant Raman Analyzers).

Four significant innovations came together to create Mira: diode lasers, specialized filters and gratings, on-axis optics, and the CCD (Charge Coupled Device) in a unique design called the «astigmatic spectrograph». These basic components of a Raman spectrograph can be seen in the graphical representation above (click to enlarge). Note that this is not an accurate depiction of the unique geometries found within Mira’s case!

Raman spectroscopy is a technique which relies on the excitation of molecules with light (energy). C.V. Raman’s discovery of Raman scattering in 1928 was enabled by focused sunlight, which was then quickly replaced with a mercury lamp for excitation and photographic plates for detection. This resulted in a simple, popular, and effective method to determine the structure of simple molecules.

C.V. Raman. India Post, Government of India / GODL-India

The first commercial Raman spectrometer was available in the 1950’s. As lasers became more available in the 1960’s, followed by improved filter technology in the 1970’s, Raman grew in popularity as a technique for a wide range of chemical analysis. Integrated systems were first seen in the 1990’s, and the miniaturization of instruments began in the early 2000’s.

Miniaturization of Raman spectrometers

Diode lasers were the first step toward handheld Raman. For those of you at a certain age, you may remember that these are the kind of small, cool, low energy lasers used in CD players, stabilized at the source with a unique kind of diffraction grating.

Powerful, efficient optical filters also contribute to miniaturization by controlling laser light scattering within the spectrograph. The development of sensitive, small Charge Coupled Devices (CCDs), which are commonly used in mobile phone cameras, permitted the detection of Raman scattering and efficient transmission of the resulting signals to a computer for processing.

The astigmatic spectrograph simplified both geometry and alignment for the many components within a Raman spectrometer; this design was the final advancement in the development of handheld Raman.

From Wyoming to Switzerland

By the 1990’s, new technologies developed for diverse industries were being incorporated into Raman spectroscopy. In Laramie, WY (USA) at the time, Dr. Keith Carron was a professor of Analytical Chemistry with a focus on Surface Enhanced Raman Scattering (SERS). Dr. Carron already had robust SERS tests, but he envisioned a low-cost Raman system that would introduce his tests to industrial, medical, or defense and security markets. His next steps would revolutionize Raman spectroscopy. 

Using commercial off-the-shelf parts, Dr. Carron and his team developed an economical benchtop instrument that eliminated the high cost of Raman analysis, helping to enable its use in university curricula. In the early 2000’s, a research and education boom began as Raman grew from an esoteric technique used in high-end applications to becoming widely available for all kinds of tasks. Dr. Carron is responsible for ushering Raman into the current era. A collaboration led to a portable Raman system and, ultimately, to a new astigmatic spectrograph design in a very small instrument.

The U.S. tragedies on September 11, 2001 created an immediate push for technology to detect terrorist activity. Around this time, anthrax scares further enforced the need for “white powder” analyzers. Fieldable chemical analysis became the goal to achieve.

Dr. Carron was inspired to invent a truly handheld, battery powered Raman device for the identification of explosives and other illicit materials. A number of iterations led to CBex, a palm-sized Raman system (even smaller than Mira!) designed by Snowy Range Industries, in February 2012 (see image). CBex caught the attention of Metrohm AG, and an offer of cooperation was sent to Dr. Carron in August 2013.

Along comes Mira

Mira was born in 2015. Not only is it a novel analytical instrument, but it is also unique amongst handheld Raman spectrometers. Mira has the smallest form factor of all commercially available Raman instruments. What truly sets Mira apart from the competition is its built-in Smart Acquire routines, which provide anyone, anywhere, access to highly accurate analytical results. It is rugged, meeting MIL-STD 810G and IP67 specifications—you can drop Mira or submerge it in a liquid to get an ID.

Once Raman escaped the confines of the laboratory, it suddenly had the potential for new uses by non-technical operators, who could perform highly analytical tests safely, quickly, and accurately.

In fact, miniaturization of Raman has revolutionized safety in a number of ways:

  • Direct analysis eliminates dangers from exposure to laboratory solvents and other chemicals.
  • Through-packaging analysis prevents user contact with potentially hazardous materials.
  • Simplified on-site materials ID verifies the quality of ingredients in foods, medicines, supplements, cosmetics, and skin care products.
  • ID of illicit materials such as narcotics, explosives, and chemical warfare agents supports quick action by military and civilian agencies.

What’s Next?

I hope that you have enjoyed learning about the evolution of Raman technology from benchtop systems to the handheld instruments we have today. In the coming months we will publish articles about Mira that describe, in detail, several interesting applications of handheld Raman spectroscopy—subscribe to our blog so you don’t miss out!

As a sneak preview: In 1 month we will be introducing a brand new system, aimed at protecting consumer safety through the ID of trace contaminants in foods. Stay tuned…

Free White Paper:

Instrument Calibration, System Verification, and Performance Validation for Mira

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

How to determine if your edible oils are rancid

How to determine if your edible oils are rancid

Rancidity is the process through which oils and fats become partially or completely oxidized after exposure to moisture, air, or even light. Though not always that obvious, foods can go rancid long before they become old. For oils, whose antioxidant properties are highly valued, such as for olive oil, this is especially problematic. A simple (and free) test for rancidity of oils can be performed at home using your own analytical instruments: your senses of smell and taste.

  1.  Pour a few milliliters of the oil into a shallow bowl or cup, and breathe in the scent.
  2.  If the smell is slightly sweet (like adhesive paste), or gives off a fermented odor, then the oil is probably rancid.
  3.  A taste test should be performed to be sure, since some oils may have a naturally sweet scent.
  4.  Ensure the oil sample is at room temperature, then sip a small amount into your mouth without swallowing. Similar to tasting wine, slurp air across the oil in your mouth, then exhale to determine if the oil has flavor.
  5.  If the oil has no flavor, it is most likely rancid. Do not consume it!

Once food has turned rancid, there is no way to go back and fix it. So, if you find out by means of the sensory test that the oil is rancid, it is already too late. For those of us who would rather skip this step to avoid having rancid food in our mouths, the possibility to accurately predict the future oxidation behavior of edible oils would be great. In fact, this is exactly what the Rancimat from Metrohm can do if you follow our tips and tricks in this article.

Rancimat to the rescue!

With the 892 Rancimat and the 893 Biodiesel Rancimat, Metrohm offers two instruments for the simple and reliable determination of the oxidation stability of natural fats and oils and of biodiesel, respectively. The method, also known as the Rancimat method or Rancimat test, is the same in both cases. It is based on a simple principle of reaction kinetics, according to which the rate of a chemical reaction (here the oxidation of fatty acids) can be accelerated by increasing the temperature.

The 892 Rancimat (L) and the 893 Biodiesel Rancimat (R) from Metrohm (click to enlarge image).

How does it work?

During the determination, a stream of air is passed through the sample at a constant temperature (e.g. 110 °C according to standard EN 14214 for biodiesel). Any oxidation products that develop are transferred by the air stream to a measuring vessel, where they are detected by the change in conductivity of an absorption solution. In addition to the temperature (both the accuracy and stability of which are guaranteed by the Rancimat system), the preparation of the measurement and the condition of the accessories also influence the quality and reproducibility of the results. In this blog post, we have compiled some practical experience in using the Rancimat to help you.

Oxidation stability: practical tips and tricks from the experts

Remove foreign particles from the reaction vessel

Foreign particles in the reaction vessel can catalyze reactions in the sample, leading to measurement results which are not reproducible. Remove foreign objects such as packaging remains from the reaction vessels using a strong gas stream (preferably nitrogen).

Weigh sample with a plastic spatula

Weigh the sample directly into the reaction vessel. Make sure that the maximum filling height does not exceed 3.5 cm. An error of ±10% in the sample weight has no influence on the final result.

Metal spatulas should not be used for weighing, as the metal ions could catalytically accelerate oxidation.

Reaction vessel lid

The green reaction vessel lid (see following image, article number: 6.2753.100) must seal the reaction vessel tightly. If this is no longer possible, the lid must be replaced. Leaky reaction vessel lids lead to incorrect and non-reproducible measurement results!

Tip: to make it easier to seal or to remove the lid, a fine film of silicone oil can be applied with a finger to the upper outer edge of the reaction vessel, to a height of about 1 cm.

Position and stability of the air tube

The stable, vertical positioning of the air tube (article number: 6.2418.100 or 6.2418.130) in the reaction vessel increases the reproducibility of the measurement results.

The air tube should protrude straight down into the vessel as illustrated in the following graphic representation (click image to enlarge).

Absorbent solution in the measuring vessel

Deionized water is used as the absorption solution with the Rancimat. Prior to beginning the analysis, the electrical conductivity of the water in the measuring vessel should not exceed 5 µS/cm.

If this value is higher, check the filters of the water system, and also ensure that there are no other sources of contamination.

Need replacement measuring vessels?

We’ve got you covered.

Positioning of the cannula for air supply

The PTFE (polytetrafluoroethylene) cannula for the air supply into the absorption solution (article number: 6.1819.080) must be aligned properly so that no air passes over the electrodes of the conductivity measuring cell, as shown in the graphic (click image to enlarge).

Air bubbles at the electrodes lead to noisy measurement curves that are difficult to evaluate.

Is it time to start the determination yet?

First, the temperature of the heating block (which is defined in the method) must be reached and stabilize before the reaction vessel is inserted into the instrument.

The sample identification data is then entered in the  StabNet software by the operator.

After connecting all of the tubing for the air supply, the reaction vessel can be inserted into the heating block. The sample measurement begins immediately after pressing the button on the Rancimat.

Cleaning: important for reproducible results

To obtain reliable analysis results, cleaning all accessories is of the utmost importance.

Both the reaction vessel and the inlet tube are disposable items. You can dispose of these materials immediately after cooling down. The rest of the accessories can be cleaned with a laboratory dishwasher (or equivalent) at maximum temperature and maximum drying time.

If you use glass or polycarbonate materials for the measuring vessels, you can of course also clean them in the same manner. The same applies to the measuring vessel lid with integrated conductivity electrode, the transparent silicone tubing, or the black Iso-Versinic tube, as well as the reaction vessel lid.

Tip: the silicone or Iso-Versinic tubing should be washed in a vertical position inside of the dishwasher to ensure it is thoroughly cleaned inside.

After washing, the transfer tubes and the reaction vessel lids should be heated at 80 °C for at least two hours in a drying cabinet, since the materials of these accessories absorb reaction products. This step further reduces the possibility of carryover to the next measurement which leads to unstable measurement results.

Maintenance

Depending on the use of the Rancimat, a regular visual control of the air filter on the back of the instrument is recommended. A clogged filter will lead to fluctuating air flows. The molecular sieve may also need a regular change depending on the instrument usage.

I hope that these tips have given you some helpful suggestions which will save you a little time and troubleshooting when using the Rancimat for determination of the oxidation stability of edible oils and other products. Good luck with your determinations!

Want to learn more?

Check out all of the stability measurement options offered by Metrohm.

Post written by Simon Lüthi, PM Titration (Meters & Measuring Instruments) at Metrohm International Headquarters, Herisau, Switzerland.

Determining the total sulfite in food and beverages: faster and easier than ever

Determining the total sulfite in food and beverages: faster and easier than ever

The chances are good that if you’re reading this, you are an analytical chemist or somehow connected to the food science sector. Maybe you have had the lucky experience of measuring sulfite (SO32-) before in the laboratory. I certainly have, and the adventure regarding tedious sample preparation and proper measurement of such a finicky analyte still haunts me today, years later.

Why sulfite?

Sulfite is a preservative added to a vast range of foods and beverages to prevent browning or oxidation. Some individuals are sensitive to sulfite additives and may experience a range of allergic reactions. Therefore, both the U.S. Food and Drug Administration (FDA) and European Union (EU) laws require that the presence of sulfites be declared on food labels when the concentration exceeds 10 mg/L.

To put this into perspective, an Olympic size swimming pool can hold about 2,500,000 liters, meaning anything beyond 25 kilograms (the average mass of one young child!) would need to be reported.

So, which foods contain sulfite?

Many foods and beverages contain sulfite – whether added to prolong the freshness, or occurring naturally as a byproduct from processes like fermentation. Typically, the first things that come to mind are wine, beer, or dried fruit snacks. However, many pickled and otherwise preserved items such as sauerkraut, canned fruits and vegetables, and even frozen foods contain significant levels of sulfites. Processed meats, several condiments, and some prepared doughs are also high on the list of offenders, so beware at your next picnic!

If you think you may be sensitive to sulfites, don’t forget to check the nutrition facts, and try to avoid such foodstuffs.

How is sulfite usually measured?

Several analytical methods exist to measure sulfite in food and beverages, however they suffer from repeatability issues, and can be quite cumbersome to perform.

Traditionally, the optimized Monier-Williams (OMW) AOAC Official Method 990.28 was used for quantification of sulfite in most foodstuffs, but the method detection limit now lies at the regulatory labeling threshold. Automated discrete analysis methods have been reported for sulfite analysis, but they are limited by their strong dependence on sample matrix type. Therefore these methods are less than ideal for laboratories where sulfite analysis is required for a wide variety of food and beverage products.

Methods based on ion chromatography (IC) with conductivity detection exhibit a lack of selectivity combined with an extended analysis time due to separation challenges. A newer method developed by AOAC (Method 990.31) focuses on the use of ion-exclusion chromatography followed by electrochemical (amperometric) detection of samples.

Another issue arises concerning the sensitivity of the detector. After a few injections, fouling from contaminants rapidly decreases the electrode sensitivity. Frequent reconditioning of the working electrode is necessary due to a rising background and baseline noise, and can be accomplished in a couple of ways. Manual polishing and utilizing pulsed amperometric detection (PAD) pulse sequences are the most common choices to recondition the surface of the working electrode, while other methods opt for disposable electrodes to avoid this step altogether.

What has improved?

Metrohm has filed a patent for an innovative, fast, and accurate ion chromatographic (IC) method based on direct current (DC) mode electrochemical detection. It works with the implementation of a unique working electrode conditioning function (patent pending) in the newest version of chromatographic software (MagIC Net 3.3) offered by Metrohm. A great diversity of food and beverage products were analyzed with sulfite recovery values near 100% in all cases. Using a single, robust chromatographic method, any sample can be treated identically, saving time and making laboratory work much easier.

Sample of garlic analyzed for sulfite content (spiked: red, unspiked: black). Recovery was calculated at 100%.
(Click to enlarge)

No matter what type of sample (solid, liquid), the preparation steps are nearly identical, and much simpler to perform than ever before. Additionally, the retention time of sulfite in the method does not shift. This saves even more time for analysts as they do not have to reprocess data. Since the electrode is automatically reconditioned after each analysis, results are both reliable and reproducible. Waste from disposable electrodes is reduced, as well as costs incurred by the materials and excess working hours which would generally be spent performing other manual steps. This is truly a win-win situation for food analysis!

Benefits to QC laboratories and beyond

In real terms, this improved method allows for up to 10x the throughput of samples compared to conventional methods. Previously, the contract laboratories involved in this study could measure 5 samples, with 2 analysts per 8-hour shift (15 samples per 24 hours, if you like). With our patent-pending technique, at 10 minutes per sample, including fully automatic regeneration of the electrode surface, this allows for up to 144 samples to be analyzed every day.

Whether you work in the food and beverage industry, wastewater analysis, or in daily analytical laboratory work, you can appreciate the numerous benefits this method offers. Robustness, reproducibility, time savings, cost savings, and a simpler procedure for sample preparation across the board – are you interested? With our expertise in ion chromatography as well as electrochemistry, among other techniques, Metrohm is able to offer such cutting edge methods for the most challenging applications.

Want to learn more?

Download our free Application Note:

Sulfite determination in food and beverages applying amperometric detection

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

Special thanks are given to Miguel Espinosa, Product Manager Ion Chromatography, at Metrohm Hispania (Madrid, Spain) for his assistance in providing the laboratory data for the study.