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A high throughput automated system was developed to determine pH of culture media using a pH module equipped with an external flow cell. A custom septum-piercing, vented needle was developed to accommodate the shape and size of the customer sample vials. For this application, both accurate and precise pH measurements were required. The data presented in this document was collected by a customer as a part of their validation process and was provided for use with their consent.

Sodium fluoride is used as a preservative in biological samples for alcohol analysis. All submitted blood samples, including those taken from vehicle drivers suspected of driving under the influence of liquor, have to be tested for adequate preservation prior to alcohol determination by gas chromatography. This is critical to ensure adequate sample preservation. Inadequate sample preservation may allow glycolysis and/or microorganism growth to produce ethanol.In the past this has been done by direct potentiometric measurement using a fluoride-selective electrode (F ISE), an ion meter and certified NaF standards. The sodium fluoride level was determined manually by dipping the electrode directly into the blood sample. Results were recorded manually. This poster describes two independent automated methods of analysis that allow the minimization of this tedious and time-consuming procedure.In the first one, the fluoride content in a blood aliquot is measured by direct potentiometric measurement after the addition of TISAB and deionized water. The second method employs the titration of the sample aliquot with La(NO3)3 after adding a buffer solution.

Ion chromatography is used as a high-performance analysis method in numerous applications. For complex analysis tasks, alternative detectors such as the amperometric detector or the UV/VIS detector are often also used in addition to the conductivity detector. This article describes the areas of utilization of the amperometric detector. Catchword: Antibiotics

Raman spectroscopy is a well suited spectroscopic technique for process development and control within development laboratories in chemical, pharmaceutical, and other industries. This article demonstrates the utility of portable Raman spectroscopy as a simple and versatile tool for in situ monitoring of reactions using univariate analysis techniques such as peak trending, as well as multivariate analysis approaches to predict the end point of chemical reactions.

Raman spectroscopy is an advantageous analytical tool that allows for the measurement of molecular structure and identifying chemical composition of materials based on the rotational and vibrational modes of a molecule. With advanced technology and an optimized optical design, the B&W Tek BAC102 series E-grade probe can access lower frequency modes down to 65 cm-1, providing key information for applications in protein characterization, polymorph detection, and identification, along with material phase and structure determination.

This Application Bulletin describes …

Diazepam belongs to the 1,4-benzodiazepine group of compounds, which are used for medical purposes as tranquilizers and antidepressants. This Bulletin describes the determination of diazepam in tablets and body fluids (blood, serum, urine) by means of differential pulse polarography. If a Britton-Robinson buffer pH = 2.8 with a methanol volume fraction of 20% is used as the supporting electrolyte then a pronounced reduction peak is obtained at -0.73 V; this allows diazepam concentrations even below 0.05 µg/mL to be determined in blood. The necessary sample preparation steps are also dealt with in this Bulletin.

This Application Bulletin describes two methods for the determination of iron at the Multi Mode Electrode.Method 1, the polarographic determination at the DME, is recommended for concentrations of β(Fe) > 200 μg/L. For this method the linear range is up to β(Fe) = 800 μg/L.For concentrations < 200 μg/LMethod 2, the voltammetric determination at the HMDE, is to be preferred. The detection limit for this method is β(Fe) = 2 μg/L, the limit of quantification is β(Fe) = 6 μg/L. The sensitivity of the method cannot be increased by deposition.Iron(II) and iron(III) have the same sensitivity for both methods.These methods have been elaborated for the determination of iron in water samples. For water samples with high calcium and magnesium concentrations such as, for example, seawater, a slightly modified electrolyte is used in order to prevent precipitation of the corresponding metal hydroxides. The methods can also be used for samples with organic loading (wastewater, beverages, biological fluids, pharmaceutical or crude oil products) after appropriate digestion.

This Application Bulletins describes the polarographic determination of thiamine (vitamin B1). The procedure allows an analysis in monovitamin preparations. The linear range of the determination is also given. The limit of detection is approx. 50 µg/L thiamine.

Determination of acetic anhydride in the presence of acetic acid in acylation mixtures.

Tris(hydroxymethyl)aminomethane (TRIS) is often used in life science applications and its purity must be monitored. This analysis is possible with ion chromatography.

The lactulose/rhamnose (L/R) intestinal permeability test is used for the diagnosis of dysfunctional intestinal permeabilities. This test comprises the determination of mannitol, rhamnose, lactose and lactulose in addition to the usual blood sugars, e.g. glucose, galactose and saccharose. This Application Note presents the analysis of a blood plasma sample enriched with the four sugars mentioned above.Key word: leaky gut syndrome

The separation of lactose, lactobionic acid, sialic acid*, 6’-sialyllactose, and 3’-sialyllactose is shown as a proof of concept for the control of these components in fermentation process for a pharmaceutical product. The acceptance criterion of a minimum resolution of the peaks (< 1.3) is reached. The separation is achieved on a Metrosep Carb 2 - 250/4.0 column with subsequent pulsed amperometric detection.

Determination of formate, acetate, chloride, benzoate, and oxalate in phenolic extracts using anion chromatography with conductivity detection after chemical suppression.

Sequential suppression in cation chromatography significantly improves detection limits. The determination of the blank value of the sample vial being used is thus essential for being able to achieve such low detection limits. The leaching tests of various sample vials proceed with the intelligent Preconcentration Technique with Matrix Elimination on the Metrosep C Supp 1 - 250/4.0 column with conductivity detection following sequential suppression. The 50 mL Corning® Cell Culture Flasks from Sigma-Aldrich (CLS430168) exhibit the lowest blank values.

Voltammetric determination of boron in plasma using Beryllon III as a ligand [L. Thunus (1996), Anal. Chim. Acta 318: 303–308].

Electrochemical impedance spectroscopy (EIS) is a powerful technique which provides information about the processes occurring at the electrode-electrolyte interface. The data collected with EIS are modeled with a suitable electrical equivalent circuit. The fitting procedure will change the values of the parameters until the mathematical function matches the experimental data within a certain margin of error. In this Application Note, some suggestions are given in order to get acceptable initial parameters and to perform an accurate fitting.

In this application note, the advantage of recording the raw time domain data for each individual frequency during an electrochemical impedance measurement is described.

The rotating cylinder electrode (RCE) is a technique used in corrosion research to simulate in a laboratory environment the turbulent flow which usually occurs when liquids are transported through pipelines. The RCE is used to generate a turbulent flow at the surface of a sample, simulating the pipe flow conditions. Experiments that involve an RCE are regulated by the ASTM G185 standard. In this application note, The RCE with a 1018 carbon steel cylinder sample was used with the linear polarization (LP) measurement technique.

This Application Note details ASTM G61-compliant corrosion measurements performed with VIONIC powered by INTELLO using Metrohm’s ASTM-compliant corrosion cells.

In the application note AN-EIS-004 on equivalent circuit models, an overview of the different circuit elements that are used to build an equivalent circuit model was given. After identifying a suitable model for the system under investigation, the next step in the data analysis is estimation of the model parameters. This is done by the non-linear regression of the model to the data. Most impedance systems come with a data-fitting program. In this application note, the way NOVA is uses to fit the data is shown.

In-situ spectroelectrochemistry provides dynamic electrochemical and spectroscopic information concurrently with the redox reaction occurring on the electrode surface. Although different spectroelectrochemical configurations can be used, simple equations explain how to relate electrochemistry and spectroscopy for each experimental setup. This Application Note describes how the quantification of one electrochemical parameter (the diffusion coefficient) is calculated from the spectroscopic data as a proof of this concept.

This Application Note details the photometric determination of chondroitin sulfate with 1-hexadecylpyridinium chloride as titrant and with the Optrode (660 nm). The method is in compliance with the Ph. Eur. and the USP.

Sodium lactate is a salt form of lactic acid used in many regulated industries—therefore an accurate determination of the lactate content is required and is already covered in several norms. One such monograph by the US Pharmacopoeia (USP) results in high accuracies and well-defined titration curves but uses titrants and solvents that are more costly than necessary. In comparison, the presented modified method from Metrohm requires a 1:1 mixture of water and acetone and uses aqueous hydrochloric acid as titrant, resulting in an estimated cost reduction of 40% per titration compared to the USP method (USP–NF 2021, Issue 2). Furthermore, the time needed for each analysis is reduced to just 12% of the USP method (excluding blank determination). This Application Note presents both methods to determine lactate content and shows the results obtained on an OMNIS system.

Traditional Chinese medicine (TCM) remedies are gaining popularity in other cultures. In some TCM, sulfur dioxide (SO2) is used as a preservative, antioxidant, and disinfectant. The products are treated by sulfurization with SO2 gas. However, sulfur dioxide is a very poisonous gas. Global health authorities have set strict limits for the content of SO2 in products. It is therefore of crucial importance to determine the sulfur dioxide content to comply with these limits. In this well-suited method, the SO2 content in different natural TCM products are analyzed reliably and accurately according to ISO 22590 using the Eco Titrator equipped with an Optrode and sodium hydroxide as titrant.

Determination of fluoride, chloride, phosphate, and monofluorophosphate in glutamine monofluorophosphate using anion chromatography with conductivity detection after chemical suppression.

Determination of chloride, nitrate, phosphate, and sulfate in a protein formulation using anion chromatography with conductivity detection after chemical suppression and dialysis for sample preparation.

Determination of chloride, nitrate, phosphate, sulfate, and oxalate in human urine using anion chromatography with conductivity detection after chemical suppression and dialysis for sample preparation.

Determination of chloride in a child's sweat using anion chromatography with conductivity detection after chemical suppression.

Determination of iodide in a human 24 hour urine sample using anion chromatography with amperometric detection after chemical suppression. The result agrees with that of the photometric method. UV detection did not work.

Determination of oxalate and citrate in human urine using anion chromatography with conductivity detection after chemical suppression.

Determination of fluoride, chloride, bromide, nitrate, sulfate, and trifluoroacetate (TFA) in a peptide sample using anion chromatography with conductivity detection after chemical suppression.

Cell culture growth media contain all required components to keep cells alive. Here the amino acid composition is analyzed. A binary gradient separates in this example amino acids. The post-column reaction with ninhydrin requires a temperature of 120 °C, while the samples need to be cooled for stability.

The determination of amino acid is an important task in pharmaceutical and biochemical applications. A binary gradient separates in this example 17 amino acids of a commercially available standard solution. The post-column reaction with ninhydrin requires a temperature of 120 °C, while the samples need to be cooled for stability.

Determination of thiamine hydrochloride according to USP 28-NF 23 (second supplement) using RP chromatography with UV detection.

Determination of aluminum with Eriochrome Blue Black R at 60 °C in albumin lyophilizate after a wet digestion.

Determination of 1-methyl-nicotinamide hydrochloride in a standard using Na2CO3 as electrolyte.

Determination of cysteine and cystine in caseinate after sample preparation with NaOH.

Platinum in urine can be determined by adsorptive stripping voltammetry (AdSV) after UV digestion of the sample.

With significant global viral outbreaks becoming the norm rather than generational outliers, it is imperative that fast, sensitive, and cost-effective testing is available to the masses. Screen-printed electrodes (SPEs) allow rapid, widespread testing of populations for infectious disease, without the need of skilled personnel or burdensome equipment in the field. The possibility of point-of-care (POC) testing with SPEs has been exhibited in several recent studies. Metrohm DropSens combines high production capabilites of custom-made SPEs with a valid ISO 13485 certification "Manufacturing of sensors for medical devices", meaning testing procedures developed on these SPEs can be reliably scaled up for larger operations, with easier regulatory approval for commercialization.

This Application Bulletins describes the determination of nicotinamide (vitamin PP), a vitamin of the B series. Instructions for the determination in solutions (e.g. fruit juice), vitamin capsules and multivitamin tablets are given. The linearity range of the determination is also specified. The limit of detection is approximately 50 μg/L nicotinamide.

This Application Bulletin describes the polarographic determination of riboflavin (vitamin B2). The procedure allows an analysis in monovitamin preparations. The limit of determination is approx. 100 μg/L.

Determination of acetate, chloride, citrate, and sulfate in a concentrate of an infusion solution using anion chromatography with direct conductivity detection. Non-suppressed IC is used to avoid interferences by the amino acids.

A reference electrode has a stable and well-defined electrochemical potential (at constant temperature), against which the applied or measured potentials in an electrochemical cell are referred. A good reference electrode is therefore stable and non-polarizable. In other words, the potential of such an electrode will remain stable in the used environment and also upon the passage of a small current. This application note lists the most used reference electrodes, together with their range of use.

In recent years, field-effect transistors (FETs) have become more commonly used as a sensing platform for a multitude of electrochemical and biological applications. These devices are promising bioelectronic transducers that allow both low-potential operation and stable potentiometric measurements. FETs are now seen as an attractive alternative to using conventional electrochemical detection systems in the scientific community. This Application Note gives in-depth guidance about how to operate Metrohm DropSens bipotentiostat devices for the characterization of FETs and their use as transducers. A single μStat-i 400 device, a small and portable bipotentiostat and galvanostat, is used to demonstrate the experiments.

Low sensitivity has limited the use of Raman spectroscopy as a detection method. However, the surface-enhanced Raman scattering (SERS) effect has improved its effectivity for analytical use. Aldehyde dehydrogenase (ALDH) and cytochrome c are analyzed by Raman spectroelectrochemistry as a proof of concept in this Application Note.

The FOS/TAC value, sometimes referred to as VFA/TA, is a meaningful parameter for assessing both the current condition and the development of anaerobic digestion processes in a digester of a biogas plant. Knowledge of this value can help decrease the risk of acidification problems, which can result in a costly crash of the entire digestion process. Therefore, an accurate and reliable determination of the FOS/TAC value is important for both efficient and cost-effective production operations. This value is determined by an acid-base titration. Using the Eco Titrator from Metrohm equipped with an Ecotrode plus electrode, a reproducible and accurate determination of the FOS/TAC value is possible.

Determination of sulfate, phosphate, and pyrophosphate in human urine and mice urine using anion chromatography with conductivity detection after chemical suppression.

This Process Application Note presents a method to accurately monitor lactic acid and glucose inside a bioreactor in «real-time» with the 2060 Raman Analyzer from Metrohm Process Analytics.

Alamar Blue is monitored with fluorescence spectroelectrochemistry during its irreversible reduction to resorufin and further reversible reduction to dihydroresorufin.