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«Analyze This»: 2020 in review

«Analyze This»: 2020 in review

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

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

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

Stay healthy, and stay curious.

Best wishes,

Dr. Alyson Lanciki, Scientific Editor, Metrohm AG

Quickly jump directly to any section by clicking a topic:

Customer Stories

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

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

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

Titration

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

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

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

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

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

Karl Fischer Titration

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

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

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

Ion Chromatography (IC)

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

Metrohm IC user sitting at a laboratory bench.

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

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

Near-Infrared Spectroscopy (NIRS)

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

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

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

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

Raman Spectroscopy

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

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

Mira - handheld Raman keeping you safe in hazardous situations.

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

Process Analytics

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

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

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

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

Voltammetry (VA)

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

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

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

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

Electrochemistry (EC)

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

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

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

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

The History of…

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

Bertold Suhner, founder of Metrohm.

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

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

Specialty Topics

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

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

Industry-focused

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

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

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

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

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

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

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

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

Pharmaceutical / healthcare

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

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

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

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

Water analysis

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

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

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

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

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

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

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

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

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

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

Improving your conductivity measurements

Improving your conductivity measurements

Have you ever performed a conductivity measurement and obtained incorrect results? There are several possible reasons for this. In this post, I want to show you how you may overcome some of these issues.

By itself, conductivity measurement is performed quite easily. One takes a conductivity cell and a suitable measuring device, inserts the conductivity cell into the sample solution and reads the value given. However, there are some challenges such as choosing the right sensor, the temperature dependency of conductivity, or the CO2 uptake, which falsify your results.

The following topics will be covered in the rest of this post (click to jump to the topic):

 

So many measuring cells – which one to use?

The first and most important question about conductivity measurement is: which sensor is the most suitable for your application? The measuring range is dependent on the cell constant of your conductivity cell, and therefore this choice requires a few considerations:

  • What is the expected conductivity of my sample?
  • Do I have a broad range of conductivities within my samples?
  • What is the amount of sample I have available for measurement?

There are different types of conductivity measuring cells available on the market. Two-electrode cells have the advantage that they can be constructed within a smaller geometry, and are more accurate at low conductivities. On the other hand, other types of measuring cells show no influences towards polarization, have a larger linear range, and are less sensitive towards contaminations.

Figure 1 below shows you the wide application range of sensors with different cell constants. As a general rule: Sensors with a low cell constant are used for samples with a low conductivity and sensors with high cell constants should be used for high conductivity samples.

Figure 1. Illustration of the range of applications for different conductometric measuring cells offered by Metrohm (click to enlarge).

To get more information, check out our Electrode finder and select «conductivity measurement».

Determination of the cell constant

Each conductivity cell has its own conductivity cell constant and therefore needs to be determined regularly. The nominal cell constant is dependent of the area of the platinum contacts and the distance between the two surfaces:

:  Cell constant in cm-1
Aeff :  Effective area of the electrodes in cm2
delectrodes :  Distance between the electrodes in cm

However, no sensor is perfect and the effective cell constant does not exactly agree with the ideal cell constant. Thus, the effective cell constant is determined experimentally by measuring a suitable standard. Its measured conductivity is compared to the theoretical value:

:  Cell constant in cm-1
ϒtheor. :  Theoretical conductivity of the standard at the reference temperature in S/cm
Gmeas :  Measured conductance in S

With increasing lifetime usage, the properties of the measuring cell might change. Changing its properties means also changing its cell constant. Therefore, it is necessary to check the cell constant with a standard from time to time and to perform a redetermination of the cell constant if necessary.

Temperature dependency of the conductivity

Have you ever asked yourself why the conductivity is normally referred to at 20 °C or 25 °C in the literature? The reasoning is that the conductivity itself is very temperature-dependent and will vary with different temperatures. It is difficult to compare conductivity values measured at different temperatures, as the deviation is approximately 2%/°C. Therefore, please make sure you measure in a thermostated vessel or you use a temperature compensation coefficient.

What is a temperature compensation coefficient anyway?

The temperature compensation coefficient is a correction factor, which will correct your measured value at a certain temperature to the defined reference temperature. The factor itself depends on the sample matrix and is different for each sample.

For example, if you measure a value of 10 mS/cm at 24 °C, then the device will correct your value with a linear correction of 2%/°C to 10.2 mS/cm to the reference temperature of 25 °C. This feature of linear temperature compensation is very common and is implemented in most devices.

However, the temperature compensation coefficient is not linear for every sample. If the linear temperature compensation is not accurate enough, you can also use the feature of recording a temperature compensation function. There, you will measure the conductivity of your sample at different temperatures and afterwards fit a polynomial function though the measured points. For future temperature corrections, this polynomial function will be used, and more accurate results will be obtained.

And… what about the conductivity standard?

Figure 2. The blue curve shows the actual conductivity (mS/cm) and the orange line is a linear temperature compensation. The temperature compensation here varies from 2.39–4.04 %/°C.

Which standard do I have to choose?

In contrast to pH calibration, the conductivity cell only requires a one-point calibration. For this purpose, you need to choose a suitable standard, which has a conductivity value in the same range as your sample and is inert towards external influences.

As an example, consider a sample of deionized water, which has an expected conductivity of approximately 1 µS/cm. If you calibrate the conductivity cell with a higher conductivity standard around 12.88 mS/cm, this will lead to an enormous error in your measured sample value.

Most conductivity cells will not be suitable for both ranges. For such low conductivities (1 µS/cm), it is better to use a 100 µS/cm conductivity standard. While lower conductivity standards are available, proper handling becomes more difficult. For such low conductivities, the influence of CO2 influence increases.

Last but not least: To stir or not to stir?

This is a controversial question, as stirring has both advantages and disadvantages. Stirring enables your sample solution to be homogeneous, but it might also enhance the carbon dioxide uptake from ambient air.

Either way, it does not matter if you choose to stir or not to stir, just make sure that the same procedure is applied each time for the determination of the cell constant, and for the determination of the conductivity of your sample. Personally, I recommend to stir slightly, because then a stable value is reached faster and the effect of carbon dioxide uptake is almost negligible.

To summarize, it is quite easy to perform conductometric measurements, but some important points should be considered thoroughly before starting the analysis, like the temperature dependency, choice of suitable conductometric measuring cell, and the choice of calibration standard. Otherwise false results may be obtained.

Curious about conductivity measurements?

Read through our free comprehensive monograph:

Conductometry – Conductivity measurement

Additionally, you can download our free two-part Application Bulletin AB-102 – Conductometry below:   

Post written by Iris Kalkman, Product Specialist Titration at Metrohm International Headquarters, Herisau, Switzerland.