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Fire and ice: discovering volcanic eruptions with ion chromatography

Fire and ice: discovering volcanic eruptions with ion chromatography

Some answers lie deep beneath the ice, waiting to be discovered.

Performing environmental chemistry research has taken me to the most remote places on Earth. In my doctoral studies, I was fortunate enough to handle samples from the South Pole and to perform my own research in Greenland, and later in Antarctica for my post-doc. What were we searching for, that took us to the middle of nowhere?

Volcanic eruptions are pretty unpredictable. Among the more active and aesthetic volcanoes with lava flows are Mount Etna in Catania (Italy), Kilauea on the large island of Hawaii (USA), and more recently Mount Fagradalsfjall in Iceland. When smaller events occur, people travel from all over to view this natural wonder. However, not all eruptions are equal…

Depending on a number of factors including the height of the eruption plume and the composition of the emissions, volcanic events can have quite a significant effect on the global climate. The Volcanic Explosivity Index (VEI) is a logarithmic scale used to measure the explosivity value of volcanic eruptions and categorize them from 0 (effusive) to 8 (mega-colossal). The largest of these events in the past century was the 1991 Pinatubo eruption in the Philippines (VEI 6, colossal). The cloud column reached high into the stratosphere, ejecting huge amounts of aerosols and gases, including sulfur dioxide (SO2) that scatter and absorb sunlight. This led to a measured global cooling effect for nearly two years after the eruption ended. Images of cloudless days at noon during this time showed a flat white hazy sky, indicative of the scattering effect of high-altitude sulfur aerosols.

Other large volcanic eruptions have led to periods of famine as well as enlightenment. It is said that the fantastic skies resulting from Krakatoa in 1883 (VEI 6, colossal) inspired Edvard Munch to paint his well-known masterpiece The Scream. If you’re familiar with Frankenstein, you can thank Mary Shelley for writing it during the wintry «year without a summer» in 1816, a result of the eruption of Mount Tambora (VEI 7, super-colossal).

Solving a mystery at the ends of the Earth

This cold period has been studied at length by several research groups and methodologies. In fact, the preceding decade had been found to be abnormally cool, however no record of another volcanic eruption was immediately apparent. Ultimately, it was pristine ice that held the clue that solved this mystery, and many others.

The sulfur dioxide emitted during volcanic eruptions is oxidized to sulfuric acid aerosols in the atmosphere, and depending on the height they reach, they can reside for days or even up to years. The deposition of volcanic sulfate on the polar ice sheets of Antarctica and Greenland preserves a record of eruptions via the continuous accumulation of snow in these areas. Therefore, records of volcanic activity can be found in polar ice cores by measuring the amount of sulfate. A fantastic way to determine sulfate, along with other a suite of major anions and cations in aqueous samples even at trace levels is with ion chromatography (IC).

The author holding a 1-meter long ice core drilled in Summit Camp, Greenland (left) and Dome Concordia, Antarctica (right).

Of course, gases can also be measured as they are trapped in the spaces between snowflakes, which are then compacted into firn and subsequently locked into the ice sheet. However, the time resolution for this is not fine enough for such volcanic measurements, nor is the volume of gas large enough to make an accurate estimate of the volcanic origin.

Gases trapped in the ice can be measured with special instrumentation and give insight into the prehistoric atmosphere.

Drilling ice cores for ion analysis is not a simple business. The logistics are staggering – getting both the field equipment and properly trained personnel to the middle of the ice sheet takes a sophisticated transportation network and cannot follow a strict schedule because Mother Nature plays by her own rules.

A complete medical checkup is necessary from top to bottom, as medical facilities can be rudimentary at best. This includes bloodwork, heart monitoring, full dental x-rays, and more (depending on your age and gender). It can take several days to evacuate a hurt or sick person to a proper hospital and therefore being in good health with an up-to-date medical record is part of being prepared for this type of remote work.

Equipment must be shipped to the site weeks or months in advance, often left at the mercy of the elements before being assembled again. Hopefully, everything works. If not, you must be very resourceful because there are no regular shipments and replacement parts are difficult to come by.

Boarding passes given to polar support staff leaving from Christchurch, New Zealand to McMurdo Station (USA) in Antarctica.

Ice cores obtained from polar areas and other remote places have been used for decades to analyze and reconstruct past events. Many considerations must be made regarding where to drill, how deep to go, and so on. The geographic location is of critical importance for several reasons including avoiding contamination from anthropogenic emissions, but also for its annual snowfall accumulation rate, proximity to volcanoes and even to other living beings (like penguin colonies, in the Antarctic).

Remote drill site based outside and upwind of Summit Camp, Greenland.

A fine resolution record of sulfate from ice cores drilled in Greenland and Antarctica has led to the discovery of previously unknown volcanic events. Ion chromatography with a dual channel system allows the simultaneous measurement of cations and anions from the same sample. When dealing with such critical samples and small volumes, this is a huge benefit for complete record keeping purposes. With the addition of automatic sample preparation like Metrohm Inline Ultrafiltration or Inline Dilution, human error is eliminated with a robust, time-saving analysis method.

Over the past two decades, the time resolution for data from ice core analysis has increased significantly. Conductivity used to be the measurement of choice to determine large volcanic events in ice cores, as it is difficult to see (unaided) the deposits of tephra from many eruptions, contrary to what you may think. The conductivity of sulfuric acid is higher than that of water, but conductivity is a sum parameter and does not disclose exactly what components are in the sample.

Tephra layers deposited by a volcanic eruption in Iceland.

Even when IC began to build traction in this space, the sample sizes did not allow researchers to determine monthly variations, but yearly approximations. This meant that any smaller sulfate peaks could have been overlooked. Researchers have tried to overcome this by matching records from ice cores around the globe to estimate the size, origin, and climatic impact of past volcanoes. Unfortunately, when the drill site is located close to active volcanism (as is the case with Greenland, downwind from Iceland), even smaller eruptions can seem to have an oversized effect.

Drilling into the ice always requires keeping track of the top and bottom ends of each meter!

The enhanced time resolution now possible with more sophisticated sample preparation (i.e. continuous flow setups for sample melting without contamination) for small volume IC injection allows for more accurate dating of volcanic eruptions without other apparent historical records.

Selected data from a drilled ice core, measured by IC. Trace analysis is necessary due to the low concentrations of ionic species deposited in remote locations. Annual layer counting was possible here, as shown with the yearly variations in several measured analytes. Grey bars represent the summer season.

Depending on the annual snowfall at the drill site and the depth of the core drilled, it can be possible to determine which month in a given year the deposition of sulfate from a volcanic eruption occurred.

This information, combined with other data (e.g., deposition length) helps pinpoint the circulation of the eruption plume and estimate the global impact. Aside from this, other data can be gained by measuring the isotopic composition of the deposited sulfate to determine the height of the eruption cloud (a more accurate method to confirm stratospheric eruptions), but that is beyond the scope of this article.

Storing hundreds of meters of ice cores during a summer research campaign in Antarctica.
Summers at Dome Concordia are not balmy, as shown in the temperature data (-54.3 °C wind chill!).

Using ion chromatography, it is possible even in the field to accurately determine the depth where specific volcanic events of interest lie in the ice. Then several ice cores can be drilled in the same location to procure a larger volume of ice to perform more detailed analyses.

My ice core research laboratory in Antarctica. Left: Metrohm IC working around the clock in the warm lab. Right: the ice core sample processing area in the cold lab (kept at -20 °C).

To solve this particular mystery, it was the combination of matching the same sulfate peak measured via IC in ice cores from both polar regions along with confirming the stratospheric nature of the eruption that led to the discovery of a previously unrecorded volcanic event in the tropics around the year 1809 C.E.

Transporting insulated ice cores back home for further research takes the cooperation of scientists, camp support staff, and the government. If flying, the entire flight must be kept cold to ensure the integrity of the ice. Any unlucky person catching a ride on a cold-deck flight must bundle up!

Cold period was extended by a second volcanic eruption

In fact, the stratospheric Tambora eruption in 1815 was already preceded by another huge climate-impacting event in the tropics just a few years before. This combination led to one of the coldest periods in the past 500 years. The data obtained by IC measurements of ice cores was instrumental in this discovery, and many more in the past few years.

Leaving the Antarctic continent can happen in a number of ways: by boat, military aircraft, or a plane. I was lucky enough to catch a first class ride on a government plane, with the added bonus of having a very interesting flight plan on screen.

High impact data

Other new volcanic eruptions have been discovered in the ice core record as the analytical technology improves. Their eruption dates can also be more accurately determined, helping to explain which of them had a climatic impact or not. This information helps to improve the accuracy of climate models, as the high altitude sulfate aerosols resulting from large eruptions reflect the sun and cause long periods of global cooling. It is for this reason that some groups have proposed a form of geoengineering where controlled amounts of sulfur gases are injected high into the atmosphere to mimic the effects of a stratospheric eruption.

In conclusion

I hope that this brief summary of a niche of environmental research with ion chromatography has piqued your interest! Maybe the inspiration of knowing that such roles exist will push other young scientists to pursue a similar career path. Chemistry education does not always have to happen indoors!

Robust ion chromatography solutions

Metrohm has what you need!

Post written by Dr. Alyson Lanciki, Scientific 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!


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!


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.

Trace metal analysis with solid-state electrodes – Part 5

Trace metal analysis with solid-state electrodes – Part 5

In the last part of our series of articles about trace metal analysis using solid-state electrodes, we will have a look at the glassy carbon rotating disc electrode (GC RDE) and its application possibilities.

Did you read the other parts in this series? Find them here!

The Glassy Carbon Rotating Disc Electrode

A rotating disc electrode (RDE) consists of two parts: the electrode tip which is made available in different materials, and a driving axle. The electrode tip is simply screwed onto the axle (Figure 1) to assemble the complete working electrode.

Figure 1. The two parts which make up the RDE. Left: driving axle for RDE. Right: glassy carbon electrode tip, with shaft made of glass.

Glassy carbon (GC) has a long history as solid electrode material for trace metal analysis. In general, GC is carbon with an amorphous structure which is similar to glass or ceramics, but different from graphite or diamond which both have a crystalline structure.

Aside from properties including a high temperature stability and a hardness similar to quartz, glassy carbon is very chemically inert and has a low electrical resistance, making it a versatile electrode material.

In the Metrohm GC electrode tip (Figure 1), the glassy carbon rod is fused within a glass shaft—another inert material. This design creates an electrode tip that is inert against most chemicals and solvents and guarantees measurements with excellent reproducibility due to the seamless intersection between the electrode material and glass shaft.

Modification with a metal film

For trace metal applications, the GC electrode is modified with a metal film, usually mercury or bismuth. The film is plated ex-situ from an acid plating solution which contains about 20 mg/L Hg2+ or Bi3+. Such a solution can easily be prepared from commercially available metal standard solutions and can be used for the plating of several films.

Once the film is deposited on the glassy carbon electrode, multiple determinations can be carried out with the same film. When the performance deteriorates, the exhausted film is simply wiped off and a fresh film is plated. Since only the renewable film is affected by aging processes, the GC electrode itself can be used for a very long time.

Applications using glassy carbon electrodes exhibit excellent reproducibility and stability in combination with very low detection limits.

Figure 2. Glassy carbon rotating disc electrode in a 884 Professional VA instrument from Metrohm.


Cadmium and lead determinations

The risk of cadmium and lead poisoning from drinking water and the significance of the determination of these two elements has already been discussed in previous posts in this series. To monitor the guideline values of 3 µg/L for cadmium and 10 µg/L for lead, recommended by the WHO (World Health Organization), a detection limit of β(Cd) = 0.3 µg/L and β(Pb) = 1 µg/L would be sufficient.

With the glassy carbon electrode the determination is far more sensitive, featuring a ten-fold improvement on the limit of detection of β(Cd) = 0.02 µg/L and β(Pb) = 0.05 µg/L with a deposition time of 30 s. This limit can be lowered even more with an increased deposition time.

For this extremely sensitive determination, a mercury film is plated on the glassy carbon electrode. The determination of cadmium and lead is carried out by anodic stripping voltammetry (ASV).

To learn more about this application, please check our website.

Free Application Note download: AN-V-225 Cadmium and lead in drinking water – Simultaneous determination on a mercury film modified glassy carbon electrode.

The very low detection limit makes this application especially interesting when it is not only required to monitor limit values but to actually detect concentrations in the ppt (parts per trillion, ng/L) range, e.g. in environmental analysis such as for seawater research.

Nickel and cobalt measurements

Another application with very low detection limits using the GC electrode is the determination of nickel and cobalt. This electrode allows the detection of concentrations down to β(Ni) = 0.05 µg/L and β(Co) = 0.03 µg/L. For this application, the electrode is modified with a bismuth film. The determination of nickel and cobalt is carried out by adsorptive stripping voltammetry (AdSV) using the complexing agent DMG (dimethylglyoxime).

Figure 3. Determination of β(Ni) = 0.34 µg/L and β(Co) < LOD in tap water (30 s deposition time) using the GC RDE.

For decades, this method was successfully executed with the mercury drop electrode. The use of a bismuth film on a glassy carbon electrode offers a non-toxic alternative with a similar sensitivity as the established method. Besides the high sensitivity, this application also shows excellent repeatability.

20 consecutive determinations of β(Ni) = 0.5 µg/L and β(Co) = 0.5 µg/L, carried out on the same bismuth film, showed an average recovery of 105% for nickel, with a relative standard deviation (RSD) of 2.0%. The recovery for cobalt was 112% with a RSD of 3.3%. This makes this method a viable tool in environmental analysis when natural background concentrations, which are often in the ppt (ng/L) range, should be investigated.

For further details about this application, please refer to Application Note AN-V-224: Nickel and cobalt in drinking water – Simultaneous determination in low ng/L range on the GC RDE modified with a bismuth film.

Chromium(VI) monitoring

Legal limits for chromium are relatively high. For example, the guideline value of the World Health Organization (WHO) is 50 µg/L for drinking water. These values usually refer to the total chromium concentration, but there are significant differences in toxicity between Cr(III) and Cr(VI). Even miniscule doses of Cr(VI) are toxic as well as carcinogenic.

Since the beginning of this century, there have been ongoing discussions in the scientific community about whether an additional limit value only for Cr(VI) is required, and what this value should be.

Measuring techniques are needed which allow the determination of Cr(VI) in the ng/L range. Using the glassy carbon electrode modified with a mercury film it is possible to detect Cr(VI) concentrations down to 0.05 µg/L. Cr(VI) is determined by adsorptive stripping voltammetry (AdSV) with DTPA (diethylenetriaminepentaacetic acid) as complexing agent. The recovery of a concentration of β(Cr(VI)) = 0.1 µg/L is 111% with a relative standard deviation of 4.4% (triplicate determination).

If you are interested to learn more, download our free Application Note V-277: Chromium(VI) in drinking water – Ultra-sensitive determination on the mercury film modified glassy carbon electrode (DTPA method).

All the above-mentioned applications can be carried out manually with a 884 Professional VA system (Figure 4), but it is also possible to run small sample series with an automated setup.

Figure 4. 884 Professional VA with two 800 Dosinos for automatic addition of electrolyte and standard solution.


This was the last post in our five-part series on heavy metal analysis with solid state electrodes. If this or one of the previous posts sparked your interest in one of the applications, do not hesitate to contact your local Metrohm representative.

For a complete overview of the different applications that can be performed with the SSEs exhibited in this series, check out the table below. Click on each application note or bulletin for a free download! 

Overview: Applications with Metrohm SSEs
Element Electrode Application Document Lab Portable
Ag GC RDE Application Bulletin 207

As scTRACE Gold Application Note V-210
Application Note V-211

Bi scTRACE Gold Application Note V-218

Cd, Pb GC RDE (Hg film) Application Note V-225

Cd, Pb SPE (Hg film) Application Note V-231

Cd, Pb Bi drop Application Note V-221

Cr(VI) GC RDE (Hg film) Application Note V-227

Cr(VI) scTRACE Gold (Hg film) Application Note V-230

Cu scTRACE Gold Application Note V-213

Fe scTRACE Gold Application Note V-216

Fe Bi drop Application Note V-222

Hg scTRACE Gold Application Note V-212

Ni, Co scTRACE Gold (Bi film) Application Note V-217

Ni, Co GC RDE (Bi film) Application Note V-224

Ni, Co SPE (Bi film) Application Note V-232

Ni, Co Bi drop Application Note V-223

Pb scTRACE Gold (Ag film) Application Note V-214

Sb(III) scTRACE Gold Application Note V-229

Se(IV) scTRACE Gold Application Note V-233

Te(IV) scTRACE Gold Application Note V-234

Tl scTRACE Gold (Ag film) Application Note V-228

Zn scTRACE Gold Application Note V-215

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

Trace metal analysis with solid-state electrodes – Part 4

Trace metal analysis with solid-state electrodes – Part 4

In this series of articles featuring various solid state electrodes, we have introduced the new Bi drop electrode and the scTRACE Gold electrode and their potential in the determination of heavy metals in drinking water. In Part 4, we introduce the next type of sensors available for heavy metal analysis: the screen-printed electrode (SPE) together with two applications for the simultaneous determination of cadmium and lead as well as nickel and cobalt.

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

Screen-printed electrodes (SPEs)

Screen printing microfabrication technology is well established for the manufacture of thick film electrochemical sensors. This technology enables the mass production of reproducible and mechanically robust solid electrodes. The possibility of mass production has great impact on the price and makes the SPEs inexpensive and convenient for the determination of heavy metals.

Printing technology allows production of a maintenance-free reference electrode, making the preparation of the analytical system for the analysis of heavy metals faster and more straightforward. Here, you do not need to refill the reference electrode or clean the sensor after a finished determination. The integration of three electrodes (working, reference, and auxiliary – see Figure 1) on a single platform, with the simultaneous miniaturization of their size and the corresponding device, both supports and facilitates transportation of the equipment to the sampling point and the determination of heavy metals on-site.

Figure 1. Screen-printed electrode (SPE) from Metrohm DropSens.

The simplest and the fastest way to modify the properties of these screen-printed electrodes for heavy metal detection is to deposit (in situ or ex situ) a metal film (either bismuth or mercury) electrochemically on the working electrode. This approach allows flexible use of single sensor type (e.g. carbon) SPEs for a wide range of applications.

Mercury film modified SPEs

The mercury film on the carbon working electrode consists of a very thin layer of mercury adsorbed onto the electrode surface. The mechanisms of accumulation and the stripping are the same as those which occur at a conventional mercury drop electrode.

Bismuth film modified SPEs

Because bismuth is not toxic, there are two environmental friendly methods for the preparation of the bismuth film: in situ plating and ex situ plating. With ex situ plating, a bismuth film is prepared in a separate solution before the first determination. Then the modified electrode is rinsed with ultrapure water and can be further used for the analysis.

Screen-printed electrodes can only be used for a limited number of measurements and have to be replaced at regular intervals. The lifetime and the frequency of replacement depend on the type of electrode and the application.

Figure 2. 946 Portable VA Analyzer (SPE version).

For further information about the 946 Portable VA Analyzer, visit the Metrohm website!

Currently, screen printed electrodes allow the on-site, simultaneous determination of cadmium and lead. Therefore, below I will present a method for the cadmium and lead determination using the ex situ modification of the Metrohm DropSens 11L carbon screen printed electrodes with a mercury film.

In addition to the cadmium and lead determination, a method using an ex situ bismuth film for nickel and cobalt will be introduced. Both measurements (cadmium and lead, as well as nickel and cobalt) can be carried out with the 946 Portable VA Analyzer (version for screen printed electrodes (SPE), see Figure 2) or with any Metrohm VA Stand using the electrode shaft (see Figure 3).

Figure 3. Electrode shaft for screen-printed electrodes (SPE).

With the electrode shaft, you can now use screen-printed electrodes in any Metrohm VA Stand. Whether you are performing voltammetric trace analysis or you want to explore new application fields with your own modified sensor, the electrode shaft allows simple use of SPEs.

To download our free informative flyer, click the button below!

This leaflet explains even more about the handling and troubleshooting of the electrode shaft for screen-printed electrodes.


Anodic stripping voltammetric determination of cadmium and lead

Cadmium and lead are toxic elements, and their concentration in drinking water has to be monitored. The provisional guideline values in the World Health Organization’s «Guidelines for Drinking-water Quality» are set to a maximum concentration of 3 µg/L for cadmium and 10 µg/L for lead. The Metrohm DropSens 11L carbon screen printed electrode modified with an ex situ mercury film allows the simultaneous determination of cadmium and lead in drinking water samples (Figure 4).

Figure 4. Example for determination of cadmium and lead in tap water spiked with β(Cd) = 2 µg/L and β(Pb) = 2 µg/L.

Using the 946 Portable VA Analyzer with a 90 s deposition time, a limit of detection (LOD) of 0.3 µg/L for both elements can be achieved. This is more than sufficient to monitor the provisional WHO guideline values.

For more information about this application, download our free application note:

The relative standard deviation for 5 measurements in a check standard solution with β(Cd) = 2 µg/L and β(Pb) = 2 µg/L is 14% and 12%, and the recovery rate is 88% and 82% for cadmium and lead, respectively.

Adsorptive stripping voltammetric determination of nickel and cobalt

Nickel and cobalt can be released either directly, or via the wastewater–river pathway, into drinking water systems. In the EU, the legislation specifies 20 µg/L as the limit value for the nickel concentration in drinking water.

The simultaneous and straightforward determination of nickel and cobalt is based on adsorptive stripping voltammetry (AdSV) using dimethylglyoxime (DMG) as a complexing agent. Prior to the first determination, the Metrohm DropSens 11L carbon SPE has to be modified with an ex situ bismuth film. The unique properties of the non-toxic Bi film combined with AdSV results in an excellent performance in terms of sensitivity. When using the 946 Portable VA Analyzer the limit of detection for 30 s deposition time is approximately 0.4 µg/L for nickel and 0.2 µg/L for cobalt, and can be lowered further by increasing the deposition time.

The disposable sensor does not need maintenance such as mechanical polishing or mechanical cleaning. This method is best suited for manual systems.

Figure 5. Example determination of nickel and cobalt in tap water with the modified Metrohm DropSens 11L carbon SPE.

The relative standard deviation for 3 subsequent measurements in a check standard solution (β(Ni) = 2 µg/L β(Co) = 2 µg/L) is 7% and 8% respectively, and the recovery rate is 100% for nickel and 94% for cobalt.

For more information about this application, download our free application note:

Key features of the screen-printed electrodes

  • Mechanically robust, inexpensive, maintenance-free, miniaturized solid electrodes
  • Electrode holder fits all Metrohm VA Stands
    • 884 Professional VA, 797 VA Computrace, 663 VA Stand
  • Solution-proof electrode holder
  • Fast and easy exchange of SPEs
  • Simultaneous determination of Ni and Co, as well as Cd and Pb
  • Limit of detection in low μg/L and even high ng/L range
  • Suitable for on-site diagnostics

What’s next?

In the next part of this series on solid state electrodes, we will have a look at an ultra-sensitive and robust sensor for heavy metal detection: the glassy carbon electrode with some of its associated applications.

Post written by Dr. Jakub TymoczkoApplication Specialist VA/CVS at Metrohm International Headquarters, Herisau, Switzerland.

Fresh shrimp – made in Switzerland?

Fresh shrimp – made in Switzerland?

Shrimp from Rheinfelden

SwissShrimp AG, based in Rheinfelden, Switzerland, is the largest producer of shrimp in Europe. Michael Siragusa, a chemist and Technical Operations Manager, introduced us to the company during a visit and explained why a fully automatic IC system from Metrohm plays the main role in monitoring water quality in the breeding pools.

SwissShrimp, which are locally grown without antibiotics, shown in the packaging available in some grocery stores in Switzerland.

An ideal location

Shrimp farms are usually associated with tropical fields, especially in Southeast Asia. Often, one also thinks of the dubious reputation these farms have due to their large ecological footprint. The SwissShrimp project in Rheinfelden shows that shrimp can also be produced on a large scale in Switzerland without exhausting nature and entirely without the use of antibiotics. According to Plant Manager Michael Siragusa, many individual factors are decisive for the success of the project. One of the most important of these is that SwissShrimp AG, at its Rheinfelden site, can cover a large part of the enormous power requirements for heating the breeding pools, at very favorable conditions, using heat from the nearby Swiss Salinen AG (Swiss Salt Works).

Inconspicuous: SwissShrimp produces its shrimp in this hall located in the middle of a green meadow.
The Swiss saltworks evaporate brine for salt production. Its waste heat supplies a large part of the energy for heating SwissShrimpʹs breeding pools.

Large technical effort

There is a tropical climate in the companyʹs large, inconspicuous hall: Shrimp of the species Litopenaeus vannamei (Pacific white shrimp) are raised in a total of 16 pools, each measuring 40 x 5 x 0.50 meters, on two floors. At a constant water temperature of 28 degrees Celsius, these pools each have up to 200,000 shrimp, with the animals in one pool all at roughly the same stage of development. SwissShrimp sources the larvae from special, certified breeders in Europe or the USA. It takes around six months before shrimp of up to 14 cm in length have developed from tiny larvae, which are barely two millimeters in size.

Densely stocked: Each of the 16 pools holds up to 200,000 shrimp.

Until the shrimp grow to full size, they are fed automatically with a special, organic dry feed. The grain size and composition of this feed varies depending on the stage of development. The dense stocking of the pools means that cleaning the water requires a great deal of effort. In a total of eight water circuits, the entire volume in the breeding pools is cleaned mechanically, biologically, and chemically 20 times a day using the latest filter technology; three percent of this volume is replaced daily. 

Waste recycling: The feed for the shrimp is mainly made from fish waste. The composition and grain size is precisely matched to the different development stages of the shrimp.

An IC system from Metrohm controls the water quality

«Water treatment is essential for us. We purify the water in our pools about 20 times per day.

In order to allow the shrimp to grow and keep the biological equilibrium of the plant, we have to keep a close eye on the toxic parameters… ammonium, nitrite, and nitrate.

If we performed this monitoring by an alternative method…, the 10 to 20 determinations would take the whole day, every day

Michael Siragusa

Technical Operations Manager, SwissShrimp AG

When it comes to monitoring the water quality in the breeding pools, a fully automated IC system from Metrohm comes into play: In the SwissShrimp company laboratory, the water of each of the 8 water circuits is examined daily for concentrations of toxic pollutants such as nitrite, nitrate, and ammonium, which are introduced into the water by the excretions of the shrimp.

Download our free Application Notes below to learn more about ion chromatography and the analysis of nitrite, nitrate, and phosphate in seawater from a shrimp farm.

In the company laboratory: The water quality is monitored fully automatically with a 930 Compact IC Flex, 940 Professional IC Vario, and 858 Professional Sample Processor. In order for the shrimp to thrive, it is important to detect any deteriorations in water quality at an early stage so that corrective measures can be initiated in good time. Altogether, around 2000 multi-parameter analyses are carried out annually at this measuring station.

On the other hand, saltwater parameters important for the shrimp to thrive are measured. These include chloride, sodium, magnesium, calcium, and potassium. Given the sheer number of parameters that need to be monitored, the advantage of ion chromatography comes into effect: IC is a multi-parameter method, i.e. several different parameters can be determined with a single measurement. In addition, not only does the analysis run automatically, but sample preparation with the inline ultrafiltration and dilution steps is also integrated into this process. In fact, SwissShrimp does not need a full laboratory assistant position thanks to Metrohmʹs automated analysis system.

Learn more here about Metrohm Inline Sample Preparation (MISP) for difficult sample matrices:

In the profit zone starting this year

The operation in Rheinfelden did not begin until 2018, and SwissShrimp is not yet operating profitably. However, production is expected to increase to 60 tons annually by the end of 2021. This is when the project, costing 25 million francs, would generate a profit for the first time. The company is currently investing in marketing in order to achieve this goal, because it is not yet well known that the best shrimp to be purchased in Switzerland come from Rheinfelden.

No frozen goods

Shrimp from Rheinfelden are a delicacy and are marketed as such, but only in Switzerland so far. Around 70 to 80 kilograms of shrimp currently leave the company every day, delivered only on order. The fresh shrimp are delivered directly to end customers and select markets of the two major Swiss retailers, Migros and Coop, via Priority Mail within 24 hours in special transport boxes specially developed for SwissShrimp with integrated Peltier cooling elements. On-site collection by the customer after ordering is also possible.

Fresh shrimp, grown daily on the northern border of Switzerland.

To learn more about the production of shrimp in Rheinfelden, visit the SwissShrimp website.

Further free Application Notes for the analysis of several ions in seawater via ion chromatography can be found on the Metrohm website.

Visit our website

to learn more about how automated IC analysis can help save valuable time in your lab

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