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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.

Frequently asked questions in near-infrared spectroscopy analysis – Part 1

Frequently asked questions in near-infrared spectroscopy analysis – Part 1

Whether you are new to the technique, a seasoned veteran, or merely just curious about near-infrared spectroscopy (NIRS), Metrohm is here to help you to learn all about how to perform the best analysis possible with your instruments.

In this series, we will cover several frequently asked questions regarding both our laboratory NIRS instruments as well as our line of Process Analysis NIRS products.

1. What is the difference between IR spectroscopy and NIR spectroscopy?

IR (infrared) and NIR (near-infrared) spectroscopy utilize different spectral ranges of light. Light in the NIR range is higher in energy than IR light (Figure 1), which affects the interaction with the molecules in a sample.

Electromagnetic Spectrum
Figure 1. The electromagnetic spectrum.

This energy difference has both advantages and disadvantages, and the selection of the ideal technology depends very much on the application. The higher energy NIR light is absorbed less than IR light by most organic materials, broadening the resulting bands and making it difficult to assign them to specific functional groups without mathematical processing.

However, this same feature makes it possible to perform analysis without sample preparation, as there is no need to prepare very thin layers of analyte or use ATR (attenuated total reflection). Additionally, NIRS can quantify the water content in samples up to 15%.

Want to learn more about how to perform faster quality control at lower operating costs by using NIRS in your lab? Download our free white paper here: Boost Efficiency in the QC laboratory: How NIRS helps reduce costs up to 90%.

The weaker absorption of NIR light leads to using long pathlengths for liquid measurements, which is particularly helpful in industrial process environments. Speaking of such process applications, with NIR spectroscopy, you can use long fiber optic cables to connect the analyzer to the measuring probe, allowing remote measurements throughout the process due to low absorbance of the NIR light by the fiber (Figure 2).

Electromagnetic Spectrum
Figure 2. Illustration of the long-distance measurement possibility of a NIRS process analyzer with the use of low-dispersion fiber optic cables. Many sampling options are available for completely automated analysis, allowing users to gather real-time data for immediate process adjustments.

For more information, read our previous blog post outlining the differences between infrared and near-infrared spectroscopy.

2. NIR spectroscopy is a «secondary technology». What does this mean?

To create prediction models in NIR spectroscopy, the NIR spectra are correlated with parameters of interest, e.g., the water content in a sample. These models are then used during routine quality control to analyze samples.

Values from a reference (primary) method need to be correlated with the NIR spectrum to create prediction models (Figure 3). Since NIR spectroscopy results depend on the availability of such reference values during prediction model development, NIR spectroscopy is therefore considered a secondary technology.

Electromagnetic Spectrum
Figure 3. Correlation plot of moisture content in samples measured by NIRS compared to the same samples measured with a primary laboratory method.

For more information about how Karl Fischer titration and NIR spectroscopy work in perfect synergy, download our brochure: Water Content Analysis – Karl Fischer titration and Near-Infrared Spectroscopy in perfect synergy.

Read our previous blog posts to learn more about NIRS as a secondary technique.

3. What is a prediction model, and how often do I need to create/update it?

In NIR spectroscopy, prediction models interpret a sample’s NIR spectrum to determine the values of key quality parameters such as water content, density, or total acid number, just to name a few. Prediction models are created by combining sample NIR spectra with reference values from reference methods, such as Karl Fischer titration for water content (Figure 3).

A prediction model, which consists of sufficient representative spectra and reference values, is typically created once and will only need an update if samples begin to vary (for example after a change of production process equipment or parameter, raw material supplier, etc.).

Want to know more about prediction models for NIRS? Read our blog post about the creation and validation of prediction models here.

4. How many samples are required to develop a prediction model?

The number of samples needed for a good prediction model depends on the complexity of the sample matrix and the molecular absorptivity of the key parameter.

For an «easy» matrix, e.g., a halogenated solvent with its water concentration as the measurement parameter, a sample set of 1020 spectra covering the complete concentration range of interest may be sufficient. For applications that are more complex, we recommend using at least 40–60 spectra in order  to build a reliable prediction model.

Find out more about NIRS pre-calibrations built on prediction models and how they can save time and effort in the lab.

5. Which norms describe the use of NIR in regulated and non-regulated industries?

Norms describing how to implement a near-infrared spectroscopy system in a validated environment include USP <856> and USP <1856>. A general norm for non-regulated environments regarding how to create prediction models and basic requirements for near-infrared spectroscopy systems are described in ASTM E1655. Method validation and instrument validation are guided by ASTM D6122 and ASTM D6299, respectively.

Figure 4. Different steps for the successful development of quantitative methods according to international standards.

For specific measurements, e.g. RON and MON analysis in fuels, standards such as ASTM D2699 and ASTM D2700 should be followed.

For further information, download our free Application Note: Quality Control of Gasoline – Rapid determination of RON, MON, AKI, aromatic content, and density with NIRS.

6. How can NIRS be implemented in a production process?

Chemical analysis in process streams is not always a simple task. The chemical and physical properties such as viscosity and flammability of the sample streams can interfere in the analysis measurements. Some industrial processes are quite delicate—even the slightest changes to the process parameters can lead to significant variability in the properties of final products. Therefore, it is essential to measure the properties of the stream continuously and adjust the processing parameters via rapid feedback to assure a consistent and high quality product.

Figure 5. Example of the integration of inline NIRS analysis in a fluid bed dryer of a production plant.

Curious about this type of application? Download it for free from the Metrohm website!

The use of fiber optic probes in NIRS systems has opened up new perspectives for process monitoring. A suitable NIR probe connected to the spectrometer via optical fiber allows direct online and inline monitoring without interference in the process. Currently, a wide variety of NIR optical probes are available, from transmission pair probes and immersion probes to reflectance and transflectance probes, suitable for contact and non-contact measurements. This diversity allows NIR spectroscopy to be applied to almost any kind of sample composition, including melts, solutions, emulsions, and solid powders.

Selecting the right probe, or sample interface, to use with a NIR process analyzer is crucial to successful process implementation for inline or online process monitoring. Depending upon whether the sample is in a liquid, solid or gaseous state, transflectance or transmission probes are used to measure the sample, and specific fitting attachments are used to connect the probes to the reactor, tank, or pipe. With more than 45 years of experience, Metrohm Process Analytics can design the best solutions for your process. 

Visit our website to find a selection of free Application Notes to download related to NIRS measurements in industrial processes.

7. How can product quality be optimized with process NIRS?

Regular control of key process parameters is essential to comply with certain product and process specifications, and results in attaining optimal product quality and consistency in any industry. NIRS analyzers can provide data every 30 seconds for near real-time monitoring of production processes.

Figure 6. The Metrohm Process Analytics NIRS XDS Process Analyzer, shown here with multiplexer option allowing up to 9 measuring channels. Here, both microbundle (yellow) and single fiber (blue) optical cables are connected, with both a reflectance probe and transmission pair configured.

Using NIRS process analyzers is not only preferable for 24/7 monitoring of the manufacturing process, it is also extremely beneficial for inspecting the quality of raw materials and reagents. By providing data in «real-time» to the industrial control system (e.g., DCS or PLC), any process can be automated based on the NIRS data. As a result, downtimes are reduced, unforeseen situations are avoided, and costly company assets are safeguarded.

Furthermore, the included software on Metrohm Process Analytics NIRS instruments has a built-in chemometric package which allows qualification of a product even while it is still being produced. A report is then generated which can be directly used by the QC manager. Therefore, the product quality consistency is improved leading to potential added revenues.

Do you want to learn more about improving product quality with online or inline NIRS analysis? Take a look at our brochure!

In the next part of this FAQ, we will cover even more of your burning questions regarding NIRS for lab and process measurements. Don’t forget to subscribe to the blog so you don’t miss out on future posts!

Want to learn more about NIR spectroscopy and potential applications? Have a look at our free and comprehensive application booklet about NIR spectroscopy.

Download our Monograph

A guide to near-infrared spectroscopic analysis of industrial manufacturing processes

Post written by Dr. Nicolas Rühl (Product Manager Spectroscopy at Metrohm International Headquarters, Herisau, Switzerland) and Dr. Alexandre Olive (Product Manager Process Spectroscopy at Metrohm Applikon, Schiedam, The Netherlands).

Exposing secrets of ancient Greek civilization through chemistry

Exposing secrets of ancient Greek civilization through chemistry

This week, learn the story of how analytical instrumentation from Metrohm helps underwater archaeology locate hidden treasures beneath the seafloor.

 

Antikythera Mechanism: a machine lost to time

One of the most fascinating items ever salvaged from an ancient shipwreck is the so-called «Antikythera Mechanism». More than 2000 years old, this magnificent piece of mechanical engineering forced the scientific community to rewrite the history of science as it became clear that its unknown maker must have possessed knowledge and skills that were believed to simply not exist in the 1st century BC.

Figure 1. Digital reconstruction of the Antikythera Mechanism.

The Antikythera Mechanism was a complex and highly precise lunar and solar calendar that could also predict solar and lunar eclipses as well as the future dates of the Panhellenic Games. The complexity and precision of this machine inspired not only scientists but also Hublot, the Swiss brand famous for their luxury watches. Not only did Hublot recreate the Antikythera Mechanism in a wristwatch but they also started their own underwater archaeology program. This project of Hublot is fascinating—and we from Metrohm are part of it on every dive.

 The device was retrieved from an ancient shipwreck (70 BC) found off the coast of the Greek island of Antikythera in 1901. Since then, researchers have tried to get to the bottom of its mysteries. Dated to approximately 100 BC, the Antikythera Mechanism was a shockingly complex piece of machinery, the likes of which were not seen elsewhere for at least another millennium.

One of the challenges faced by underwater archeology is the fact that the cargo and debris of ancient shipwrecks is often randomly scattered across vast areas on the seafloor and also often covered by sediments. Because only fragments of the mechanism have been found and recovered, retrieving the missing pieces of the Antikythera Mechanism would be a scientific sensation.

Figure 2. Location where the Antikythera Mechanism was found in 1901 at a shipwreck in Greece.

As divers can only operate for very limited time spans at depths below 50 meters, drones are needed to investigate larger areas on the seafloor at such depths. Hublot’s engineers have built drones for this purpose, known as «Bubblots», and have equipped them with miniaturized voltammetric measuring stands from Metrohm.

«With a metal detector, all you get is «beep-beep-beep», which means there is metal around. However, in a bronze statue, there is copper, there is tin, and you have to detect the oxides of them, the exact kind of material you are facing. We have decided for Metrohm, because you are the most competent for the measuring technology we need in our drones.»

Mathias Buttet

R&D Director, Hublot

The Bubblots are utilized to perform real-time analyses of the seawater for unusual concentrations of dissolved metal salts typically associated with corroding bronze artefacts. Thus, the systematic and highly selective investigation of larger areas of seafloor for historical bronze artefacts becomes feasible.

Figure 3. Hublot’s underwater drones, known as «Bubblots», and the voltammetric measuring stand from Metrohm.

Voltammetry to the rescue

Due to its selectivity regarding different metals and their oxidation states, voltammetry is ideally suited for such investigations, as it is also very fast and robust technique. In the case of Hublot’s drones, results are obtained in a few seconds and this information can be immediately processed.

«We use this Metrohm instrument for voltammetric measurements. We take a water sample and do a live measurement of the aspirated water. The voltammetric measurement takes only a few seconds. This is enough to give us an idea of the different metals present in the solution. This allows us to do highly selective measurements very fast to cover different regions of the archaeological site.»

Sébastien Recalcati

Materials Engineer, Hublot

For a selection of free Metrohm Application Notes related to voltammetric measurements in seawater, visit our website!

Figure 4. The 910 PSTAT mini from Metrohm used in the study.
Figure 5. One of Metrohm’s disposable screen printed electrodes (SPEs) utilized in Hublot’s drone analysis of the seafloor.

Giving the Antikythera Mechanism a second life

The maker of this mechanism was far ahead of his time. He must have had skills and possessed scientific knowledge that are mind-boggling even today. The watchmakers from Hublot were inspired by this to a very special project: they rebuilt the Antikythera Mechanism in a wristwatch.

«The original Antikythera Mechanism has the size of a shoe box. Reducing the size of the mechanism and putting it into a wrist watch was not so easy. Because the Antikythera Mechanism was not a clock, it was a machine with a driving crank to show the position of the moon and the sun in relation to the stars at any given date. The absolute dream is to find the missing parts of the machine. But the debris is hidden below the seafloor, covered by sediments, one meter, sometimes two meters.»

Mathias Buttet

R&D Director, Hublot

Figure 6. The Antikythera Mechanism miniaturized and captured in a Hublot wristwatch.

We are glad to support Hublot’s archaeological mission with our analytical instruments and our expertise in chemical analysis. Metrohm wishes the Hublot team all the best.

Visit our website to learn more

about this fascinating project and to discover more related applications from Metrohm

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

Trace metal analysis with solid-state electrodes – Part 3

Trace metal analysis with solid-state electrodes – Part 3

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

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

Why modify the electrode material?

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

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

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

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

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

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

Applications

Lead in drinking water

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

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

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

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

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

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

Nickel and cobalt in drinking water

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

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

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

Chromium(VI) in drinking water

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

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

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

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

Summary

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

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

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

What’s next?

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

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

Forewarned is Forearmed: Error and risk minimization in process analysis – Part 3

Forewarned is Forearmed: Error and risk minimization in process analysis – Part 3

In the course of life, each of us learns to trust our gut feelings or our experiences to avoid situations that seem dangerous or risky. You quite literally sense potential dangers with an uneasy feeling. Who hasn’t painfully learned that touching a hot stove top isn’t a good idea? Or who voluntarily goes outside during a tornado?

While humans can rely on their intuition and learned patterns to avoid dangers or use protective strategies, this is far more complicated with electronic systems or machines. All components of a system must be in a permanently safe state. Failures and malfunctions of individual components can have devastating consequences for production processes and the safety of the operators.

An example of this is the Seveso disaster in 1976, in which highly toxic dioxin TCDD escaped as a result of an uncontrolled reaction, and sustainably poisoned flora and fauna. With regard to other major chemical accidents, the European Seveso III Directive then came into force in 2012 to control major accident hazards to prevent major accidents.

Have you read Part 1 and Part 2 of our «Advantages of PAT (Process Analytical Technology)» series? If not, find them here!

Recognize, master, and avoid errors

Process engineering systems that are operated continuously contain countless components that can wear out or fail during their life cycle. However, if the measuring, control, or regulating circuit is affected, failures can cause immense damage. Under no circumstances should humans nor the environment be exposed to any kind of danger. For this reason, the functional safety of the components must be guaranteed, and their risk and hazard potential must be analyzed in detail.

The service life of mechanical components can be evaluated by observing mechanical wear and tear. However, the aging behavior of electronic components is difficult to assess. A unit of measure that makes risk reduction and thus functional safety quantifiable is the so-called «Safety Integrity Level» (SIL). 

The following procedure is followed:

  1.   Risk analysis
  2.   Realization of risk reduction
  3.   Evidence that the realized risk reduction corresponds at least to the required risk reduction

«Process analysis systems are part of the entire safety cycle of a manufacturing plant and therefore only one component whose risk of malfunctions and failures must be considered in an assessment.»

Risk assessmentA process is considered safe if the current risk has been reduced below the level of the tolerable risk. If safety is ensured by technical measures, one speaks of functional safety.

Significance for process analysis systems

Errors can happen anywhere, and can never be completely excluded. To minimize possible errors, it is therefore necessary to estimate the risk of occurrence and the damage to be expected from it as part of a risk analysis. A distinction must be made here between systematic and random errors.

Systematic errors are potentially avoidable and are caused, for example, by software errors or configuration deficiencies. Accordingly, they already exist during or prior to commissioning.

In contrast, random errors are potentially difficult to avoid because they occur arbitrarily. Nevertheless, the error rate or failure probability can be determined statistically and experimentally.

Random errors usually result from the hardware and occur during operation. Ultimately, systematic errors should be avoided, and random errors should be mastered to ensure trouble-free functionality.

Process analysis systems are the link between manual laboratory analysis and the industrial process. In applications where continuous and fully automatic monitoring of critical parameters is required, process analyzers are indispensable. Due to the different analysis conditions in the laboratory and directly in the process, there are some challenges when transferring the measurement technology from the lab to the process. The decisive factors are the working and environmental conditions (e.g., high temperatures, corrosive atmospheres, moisture, dust, or potentially explosive environments) which the process analyzers have to meet regarding their design, construction materials, and reliability of the components. The analyzer automatically and continuously transmits system and diagnostic data to prevent hardware or software components from failing through preventive measures. This significantly reduces the chance of random errors occurring.

General process analyzer setup

a) Analyzer Setup

Process analyzers have been specially developed for use in harsh and aggressive industrial environments. The IP66 protected housing is divided into two parts, and consists of separate wet and electronic parts. The electronics part contains all components relevant to control and operate the process analyzer. Modular components like burettes, valves, pumps, sampling systems, titration vessels, and electrodes can be found in the analyzer wet part. Representative samples can thus be taken from the process measuring point several meters away. The analysis procedure, the methods to be used, and method calculations are freely programmable.

A touchscreen with intuitive menu navigation allows easy operation, so that production processes can be optimized at any time. The course of the measurement is graphically represented and documented over the entire determination, so that the analysis process is completely controlled. The measurement results can be generated 24/7 and allow close and fully automatic monitoring of the process. Limits, alarms, or results are reliably transferred to the process control system.

When operating the analyzer, there is a risk that software errors can lead to failures. In order to recognize this with foresight, the system delivers self-diagnostic procedures as soon as it is powered on and also during operation. This includes, e.g., checking pumps and burettes, checking for leaks, or checking the communication between the I/O controller, the human interface, and the respective analysis module.

b) Sensors

The central component of a process analyzer is the measurement technique in use. In the case of sensors or electrodes, there are several requirements such as chemical resistance, ease of maintenance, robustness, or precision which they must meet. The safety-related risk arises from the possibility if measurement sensors fail due to aging, or if they become damaged and subsequently deliver incorrect measurement results.

Failure of the electrode, contamination, or damage must be reported immediately. With online analysis systems, the analysis is performed in an external measuring cell. In addition, recurring calibration and conditioning routines are predefined and are performed automatically. The status of the electrode is continuously monitored by the system.

Between measurements, the electrode is immersed in a membrane-friendly storage solution that prevents drying out and at the same time regenerates the swelling layer. The electrode is therefore always ready for use and does not have to be removed from the process for maintenance. This enables reliable process control even under harsh industrial conditions.

c) Analysis

Process analyzers must be able to handle samples for analysis over a wide concentration range (from % down to trace levels) without causing carry-over or cross-sensitivity issues. In many cases, different samples from several measuring points are determined in parallel in one system using different analysis techniques. The sample preparation (e.g., filtering, diluting, or wet chemical digestion) must be just as reliable and smooth as the fully automatic transfer of results to the process control system so that a quick response is possible.

Potential dangers for the entire system can be caused by incorrect measurement results. In order to minimize the risk, a detector is used to notify the system of the presence of sample in the vessel. The testing of the initial potential of the analysis or titration curves / color development in photometric measurements are diagnostic data that are continuously recorded and interpreted. Results can be verified by reference analysis or their plausibility can be clarified using standard and check solutions.

Detect errors before they arise

The risk assessment procedures that are carried out in the context of a SIL classification for process engineering plants are ultimately based on mathematical calculations. However, in the 24/7 operation of a plant, random errors can never be completely excluded. Residual risk always remains. Therefore, the importance of preventive maintenance activities is growing immensely in order to avoid hardware and software failures during operation.

A regular check of the process analyzer and its diagnostic data is the basic requirement for permanent, trouble-free operation. With tailor-made maintenance and service concepts, the analyzer is supported by certified service engineers over the entire life cycle. Regular maintenance plans, application support, calibration, or performance certificates, repairs, and original spare parts as well as proper commissioning are just a few examples.

Advantages of preventive maintenance from Metrohm Process Analytics

  • Preservation of your investment
  • Minimized risk of failure
  • Reliable measurement results
  • Calculable costs
  • Original spare parts
  • Fast repair
  • Remote Support

In addition, transparent communication between the process control system and the analyzer is also relevant in the context of digitalization. The collection of performance data from the analyzer to assess the state of the control system is only one component. The continuous monitoring of relevant system components enables conclusions to be drawn about any necessary maintenance work, which ideally should be carried out at regular intervals. The question arises as to how the collected data is interpreted and how quickly it is necessary to intervene. Software care packages help to test the software according to the manufacturer’s specifications, to perform data backup and software maintenance.

«Remote support is particularly important in times when you cannot always be on site.»

In real emergency situations in which rapid error analysis is required, manufacturers can easily support the operator remotely using remote maintenance solutions. The system availability is increased, expensive failures and downtimes are avoided, and the optimal performance of the analyzer is ensured.

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).

Frequently asked questions in Karl Fischer titration – Part 2

Frequently asked questions in Karl Fischer titration – Part 2

Since I started working at Metrohm more than 15 years ago, I have received many questions about Karl Fischer titration. Some of those questions have been asked repeatedly from several people in different locations around the world. Therefore, I have chosen 20 of the most frequent questions received over the years concerning Karl Fischer equipment and arranged them into three categories: instrument preparation and handling, titration troubleshooting, and the oven technique. Part 1 covered instrument preparation and handling, and Part 2 will now focus on titration troubleshooting and the KF oven technique.

Summary of questions in the FAQ (click to go directly to each question):

Titration troubleshooting

1.  If the drift value is 0, does this mean that the titration cell is over-titrated?

A drift of zero can be a sign that the cell might be over-titrated. In combination with the mV signal (lower than end-point criteria) and the color of the working medium (darker yellow than usual), it is a clear indicator for over-titration. However, volumetric titrations sometimes exhibit a zero drift for a short time without being over-titrated. If you have a real excess of iodine in the titration cell, the result of the next determination will most likely be erroneous. Therefore, over-titration should be avoided. There are various possible reasons for over-titration, like the sample itself (e.g., oxidizing agents which generate iodine from the working medium), the electrode (coating or invisible depositions on the Pt pins/rings), the reagent, and method parameters (e.g., the titration is rate too high), to name just a few.

2.  Should I discard the Karl Fischer reagent immediately if it turns brown?

Different factors can cause over-titration, however, the reagent is not always the reason behind this issue. The indicator electrode can also be the reason for overshooting the endpoint. In this case, regular cleaning of the electrode can prevent over-titration (see also questions 7 to 9 from Part 1 in this series on cleaning).

A low stirring speed also increases the risk of over-titration, so make sure the solution is well mixed. Depending on the type of reagent, the parameters of the titration need to be adjusted. Especially if you use two-component reagents, I recommend decreasing the speed of the titrant addition to avoid over-titration. Over-titration has an influence on the result, especially if the degree of over-titration changes from one determination to the next. So over-titration should always be avoided to guarantee correct results.

3.  What is drift correction, and when should I use it?

I recommend using the drift correction in coulometric KF titration only. You can also use it in volumetric titration, but here the drift level is normally not as stable as for coulometric titrations. This can result in variations in the results. A stabilization time can reduce such an effect. However, compared to the absolute water amounts in volumetry, the influence of drift is usually negligible.

4.  My results are negative. What does a negative water content mean?

Negative values do occur if you have a high start drift and a sample with a very low water content. In this case, the value for drift correction can be higher than the absolute water content of the sample, resulting in a negative water content.

If possible, use a larger sample size to increase the amount of water added to the titration cell with the sample. Furthermore, you should try to reduce the drift value in general. Perhaps the molecular sieve or the septum need to be replaced. You can also use a stabilizing time to make sure the drift is stable before analyzing the sample.

Karl Fischer oven

5.  My samples are not soluble. What can I do?

In case the sample does not dissolve in KF reagents and additional solvents do not increase the solubility of the sample, then gas extraction or the oven technique could be the perfect solution.

The sample is weighed in a headspace vial and closed with a septum cap. Then the vial is placed in the oven and heated to a predefined temperature, leading the sample to release its water. At the same time, a double hollow needle pierces through the septum. A dry carrier gas, usually nitrogen or dried air, flows into the sample vial. Taking the water of the sample with it, the carrier gas flows into the titration cell where the water content determination takes place.

6.  Can all types of samples be analyzed with the oven method?

Many samples can be analyzed with the oven. Whether an application actually works for a sample strongly depends on the sample itself. Of course, there are samples that are not suitable for the oven method, e.g., samples that decompose before releasing the water or that release their water at higher temperatures than the maximum oven temperature.

7.  How do I find the optimal oven temperature for water extraction?

Depending on the instrument used, you can run a temperature gradient of 2 °C/min. This means it is possible to heat a sample from 50 to 250 °C within 100 minutes. The software will then display a curve of water release against temperature (see graph).

From such a curve, the optimal temperature can be determined. Different peaks may show blank, adherent water, different kinds of bound water, or even decomposition of the sample.

This example curve shows the water release of a sample as it has been heated between 130 and 200 °C. At higher temperatures, the drift decreases to a stable and low level.

Generally, you should choose a temperature after the last water release peak (where the drift returns to the base level) but approximately 20 °C below decomposition temperature. Decomposition can be recognized by increasing drift, smoke, or a color change of the sample. In this example, there are no signs of decomposition up to an oven temperature of 250 °C. Therefore, the optimal oven temperature for this sample is 230 °C (250 °C – 20 °C).

In case the instrument you use does not offer the option to run a temperature gradient, you can manually increase the temperature and measure the sample at different temperatures. In an Excel spreadsheet, you can display the curve plotting released water against temperature. If there is a plateau (i.e., a temperature range where you find reproducible water contents), you have found the optimal oven temperature.

8.  What is the highest possible water content that can be measured with a Karl Fischer oven?

Very often, the oven is used in combination with a coulometric titrator. The coulometric titration cell used in an oven system is filled with 150 mL of reagent. Theoretically, this amount of reagent allows for the determination of 1500 mg of water. However, this amount is too high to be determined in one titration and it would lead to very long titration times and negative effects on the results. We recommend that the water content of a single sample (in a vial) should not be higher than 10 mg, ideally around 1000–2000 µg water. For samples with water contents in the higher percentage range, you should consider the combination with a volumetric titrator.

9.  What is the maximum sample size that can be used with the oven? If I use too much sample, will the needle be blocked?

The standard vial for the oven method has a volume of approximately 9 mL. However, we do not recommend filling the vial completely. Do not fill more than 5–6 mL of sample in a vial. We offer the possibility to customize our oven systems, allowing you to use your own vials. Please contact your local Metrohm agency for more information on customized oven systems.

For liquid samples, we recommend using a long needle to lead the gas through the sample. Solid samples and especially samples that melt during analysis require a short needle. The tip of the needle is positioned above the sample material to avoid needle blockage.

Additionally, you should use a «relative blank value», i.e., taking only the remaining air volume into account for blank subtraction. You can find more information about the relative blank and how to calculate it in Application Note AN-K-048.

10.  What is the detection limit of the oven method, and how much sample is required to analyze a sample with 10 ppm (mg/L) water content?

We recommend having at least 50 µg of water in the sample, if analyzed with coulometry. However, if conditions are absolutely perfect (i.e., very low and stable drift plus perfect blank determination), it is possible to determine even lower water contents, down to 20 µg of absolute water. For a sample with a water content of < 10 ppm (mg/L), this would correspond to a sample size of at least 2 g.

11.  How do I verify an oven method?

For the verification of an oven system, you can use a certified water standard for oven systems. With such a standard, you can check the reproducibility and the recovery. There are a few types of standards available for different temperature ranges.

I hope this collected information helps you to answer some of your most burning KF questions. If you have further unanswered questions, do not hesitate to contact your local Metrohm distributor or check out our selection of webinars.

Automate thermal sample preparation

It’s easy with an oven sample changer from Metrohm!

Post written by Michael Margreth, Sr. Product Specialist Titration (Karl Fischer Titration) at Metrohm International Headquarters, Herisau, Switzerland.