Методики

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.

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.

Psychoactive gamma-hydroxybutyrate (GHB) and its prodrug gamma-butyrolactone (GBL) are substances that are increasingly abused as date-rape and recreational (party) drugs. Since the non-controlled GBL converts into the illicit GHB both in-vivo and in-vitro, their legal distinction is of crucial importance.For the forensic determination of illegally added GHB and GBL in commonly consumed beverages, this work presents a simple and sensitive method that employs direct-injection ion chromatography combined with spectrophotometric detection. The method allows to trace GHB-GLB interconversion, whether in vivo or in vitro lactone cleavage or intramolecular GHB esterification, and thus complies with pertinent requirements of law enforcement agencies.

UV/VIS detection is one of the most sensitive detection techniques in trace-level chromatography. Sometimes, however, spectrophotometric detection lacks sensitivity, selectivity or reproducibility and chemical derivatizations are required. By using Metrohm`s rugged and versatile flow-through reactor, single- or multi-step derivatizations can be done fully automatically, in either pre- or post-column mode at any temperature between 25…120 °C. The variable reactor geometry allows to adjust the reactor residence time of the reactants according to derivatization kinetics. The flexibility of the reactor is demonstrated by optimizing four widespread post-column techniques: the relatively slow ninhydrin reaction with amino acids and the fast derivatizations of silicate, bromate and chromate(VI).

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.

The Rancimat method is an accelerated ageing test. Air is conducted through the sample in the reaction vessel at a constantly increased temperature. The fatty acids are oxidized during this process. Volatile secondary reaction products are formed at the end of the test that are conducted by air flow into a measuring vessel, where they are absorbed by a measuring solution (distilled water). The continually recorded electrical conductivity increases as a result of the absorption of the ionic reaction products. The time up to which the secondary reaction products arise is called the induction time. It characterizes the oxidation stability of oils and fats.This Application Bulletin provides a detailed description of the method, in particular also of the required sample preparation.

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 folic acid, a vitamin of the B series, also known as vitamin B9 or vitamin BC. Instructions for the determination in solutions (e.g. fruit juice), vitamin capsules and multivitamin tablets are given. The linear range of the determination is also specified. The limit of detection is approx. 75 µg/L folic acid.

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.

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.

This Application Bulletin describes …

The presented Application Bulletin describes the apparatus and methods that are used for acid-base analysis of whole blood and blood plasma by Joergensen and Stirum. Evaluation of the measured data is performed with a software sold by Komstar AG.

Determination of lysine as well as sodium, ammonium, potassium, and calcium in bulk lysine using cation chromatography with direct conductivity detection.

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.

The ASTM standard G61 is used to determine the susceptibility to localize corrosion on various alloys of iron, nickel and cobalt, in a chlorine environment. This application notes shows a measurement example in accordance with the ASTM G61 by using a Metrohm Autolab PGSTAT302N and a Metrohm Autolab 1 L corrosion cell.

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

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.

A fuel cell is an electrochemical energy conversion device that produces electricity and heat by electrochemically combining a fuel (typically hydrogen) and an oxidant (typically oxygen). The higher efficiency also results in much lower carbon dioxide emissions and negligible amounts of SOx and NOx (when reformed fuel is used) compared with fossil fuel-based technologies for the same power output.

To overcome the various technical problems, many different fuel cell types have been developed. In this Application Note, proton exchange membrane, direct methanol and solid oxide fuel cells are discussed in more detail.

In this Application Note the use of Electrochemical Impedance Spectroscopy (EIS) for the characterisation of PEM fuel will be demonstrated. It will be shown that EIS is a powerful diagnostic tool for the determination of the following factors that can influence the performance of a PEM fuel cell.

The use of impedance measurements on fuel cells under load makes it possible to study the influence of the different fuel cell elements on the behavior and (if detectable) on the ageing of the fuel cell. To perform high current density measurements, the Autolab systems can be connected to a third party electronic load. This extends the measurable range of the instrument by several current decades.

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.

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

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

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.

This Application describes the determination of moisture, nitrogen, and fat in stool samples using near-infrared spectroscopy. These parameters are of great importance in medical diagnostics.

Determination of key quality parameters of palm oil, namely free fatty acids (FFA), iodine value (IV), moisture content, deterioration of bleachability index (DOBI), and carotene require the use of several different analytical methods, which are laborious and can lack in accuracy. This application note demonstrates that the XDS RapidLiquid Analyzer operating in the visible and near infrared spectral region (Vis-NIR) provides a cost-efficient and fast solution for the determination of these quality control parameters in palm oil. With no sample preparation or chemicals needed, Vis-NIR spectroscopy allows for the analysis of palm oil in less than a minute and can be used by anyone.

Determination of citrate, succinate, lactate, β-hydroxybutyrate, and acetate in dry albumin powder using ion-exclusion chromatography with suppressed conductivity detection and dialysis for inline sample preparation.

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

A low-pressure gradient enables the separation of sugar acids strongly retained on the column and sugars within an appropriate analysis time. The saccharides are separated on a column of the Metrosep Carb 2 - 250/4.0 type with subsequent pulsed amperometric detection (PAD). Galactose and arabinose are not completely separated under the selected conditions.

This Application Note describes the separation of inositol, mannitol, glucose, xylose, fructose, lactose, sucrose and cellobiose on a column of the Metrosep Carb 2 - 150/4.0 type with subsequent pulsed amperometric detection (PAD).

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.

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.

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.

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 α-glycerophosphate and β-glycerophosphate in amino acids 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.

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.

Qualitative determination of chloride, phosphate, and sulfate as well as chlorite, nitrite, chlorate, bromide, and chromate in urine using anion chromatography with conductivity detection after chemical suppression.

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

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.

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.

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.

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.