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This article describes a simple and sensitive method for chromium(VI) determination in children's toys. The solution to be analyzed is prepared in accordance with DIN EN 71. Not only VIS detection but also post-column derivatization using diphenylcarbizide are parts of this method. The procedure described here is suitable for the precise determination of hexavalent chromium in the single-digit ppt range and, in addition, fulfils without difficulty the limit value of 10 ppt prescribed by the EU directive 2009/48/EC.

Underestimation of quality control (QC) processes is one of the major factors leading to internal and external product failure, which have been reported to cause a loss of turnover between 10–30%. As a result, many different norms are put in place to support manufacturers with their QC process. However, time to result and the associated costs for chemicals can be quite excessive, leading many companies to implement near-infrared spectroscopy (NIRS) in their QC process. This paper illustrates the potential of NIRS and displays cost saving potentials up to 90%.

Hydroxyl is an important functional group and knowledge of its content is required in many intermediate and end-use products such as polyols, resins, lacquer raw materials and fats (petroleum industry). The test method to be described determines primary and secondary hydroxyl groups. The hydroxyl number is defined as the mg of KOH equivalent to the hydroxyl content of 1 g of sample.The most frequently described method for determining the hydroxyl number is the conversion with acetic anhydride in pyridine with subsequent titration of the acetic acid released: H3C-CO-O-CO-CH3 + R-OH -> R-O-CO-CH3 + CH3COOH. However, this method suffers from the following drawbacks: - The sample must be boiled under reflux for 1 h (long reaction time and laborious, expensive sample handling) - The method cannot be automated - Small hydroxyl numbers cannot be determined exactly - Pyridine has to be used, which is both toxic and foul-smellingBoth standards, ASTM E1899-08 and DIN 53240-2, offer alternative methods that do not require manual sample preparation and therefore can be fully automated: The method suggested in ASTM E1899-08 is based on the reaction of the hydroxyl groups attached to primary and secondary carbon atoms with excess toluene-4-sulfonyl-isocyanate (TSI) to form an acidic carbamate. The latter can then be titrated in a non-aqueous medium with the strong base tetrabutyl- ammonium hydroxide (TBAOH). The method suggested in DIN 53240-2 is based on the catalyzed acetylation of the hydroxyl group. After hydrolysis of the intermediate, the remaining acetic acid is titrated in a non-aqueous medium with alcoholic KOH solution. The present work demonstrates and discusses an easy way to determine the hydroxyl number according to ASTM E1899-08 or DIN 53240-2 with a fully automated titrimetric system for a great variety of industrial oil samples.

This article demonstrates the utility of portable Raman spectroscopy as a versatile tool for process analytical technology (PAT) for raw material identification, in-situ monitoring of reactions in developing active pharmaceutical ingredients (APIs), and for real-time process monitoring. Raw material identification is done for verification of starting materials as required by PIC/S and cGMP, and can be readily done with handheld Raman. Portable Raman systems allow users to make measurements to bring process understanding and also provide proof of concept for the Raman measurements to be implemented in pilot plants or large-scale production sites. For known reactions which are repetitively performed or for continuous online process monitoring of reactions, Raman provides a convenient solution for process understanding and the basis for process control.

Raman spectroscopy’s use for process analytics in the pharmaceutical and chemical industries continues to grow due to its nondestructive measurements, fast analysis times, and ability to do both qualitative and quantitative analysis. Spectral preprocessing algorithms are routinely applied to quantitative spectroscopic data in order to enhance spectral features while minimizing variability unrelated to the analyte in question. In this technical note we discuss the main preprocessing options pertinent to Raman spectroscopy with real applications examples, and to review the algorithms available in B&W Tek and Metrohm software so that the reader becomes comfortable applying them to build Raman quantitative models.

Carbonyl compounds (CC) occur in many products, such as bio-oils and fuels, cyclic and acyclic solvents, flavors and mineral oils. Carbonyl compounds can be responsible for the instability of these products during storage or processing. Especially pyrolysis bio-oils are known to cause issues during storage, handling and upgrading. This bulletin describes an aqueous and a non-aqueous analytical titration method for the determination of carbonyl compounds by potentiometric titration.

4-Carboxybenzaldehyde, in the following referred to as 4-CBA, can be reduced directly at the dropping mercury electrode (DME) in an ammoniacal solution. After a very simple sample preparation it is now possible to determine the concentration of 4-CBA in terephthalic acid quickly and precisely by polarography down to the lower ppm range.

This Application Bulletin describes the determination of the thermostability of PVC in accordance with ISO 182 Part 3 using the dehydrochlorination method with the 895 Professional PVC Thermomat. The instrument permits fully automatic determination of the stability time. The test is suitable for monitoring the manufacture and processing of PVC products manufactured in the injection molding process, for their final clearance, characterization and for the comparison of PVC products and for testing the effectiveness of heat stabilizers.

Maleic and fumaric acid can be reduced electrochemically to succinic acid. In acidic solutions a differentiation of the two acids is not possible since both are reduced at the same potential. On the other hand, separation at pH 7.8...8.0 is easily possible since fumaric acid is now more difficult to reduce at the lower proton concentration (as a result of cis-trans isomerism) than maleic acid.

Polyisobutene (PIB) is an important raw material for a large range of products. Quality control requires the determination of the fluorine content. This task is easily done by Metrohm Combustion IC applying flame sensor technology and Inline Matrix Elimination.Keyword: pyrohydrolysis

Halobutyl rubber is frequently used in the production of pharmaceutical stoppers. It is ideal for this application due to its low permeability to gases and its chemical resistance. Chlorinated and brominated butyl rubber stoppers are analyzed for their halogen and sulfur content. Halogen and sulfur compounds are released by pyrohydrolysis and analyzed by subsequent ion chromatography (IC).

Combustion Ion Chromatography combines pro-hydrolytic sample combustion and the absorption of emerging combustion gases in an oxidizing, aqueous solution that is then channeled to an ion chromatograph for the analysis of halogenides and sulfur (as sulfate). The combustion and analysis of the certified reference materials (ZRM) makes clear the reliability of Metrohm Combustion Ion Chromatography.Keyword: pyrohydrolysis

This Application Note describes a fast, nondestructive, and reliable NIRS method for the determination of the hydroxyl number in polyols. Results are available in real-time for which reason NIRS is highly suited for in-process quality control. Second-derivative spectra and linear least-squares regression provide results that match very well with those obtained by titration.

This Application Note demonstrates the feasibility of Vis-NIRS for the simultaneous determination of multiple chemical and physical parameters in epoxy resins. Vis-NIRS is a fast alternative to conventional lab methods: it accelerates raw material inspection, process monitoring, and final product control.

Determination of the diethylene glycol content, isophthalic acid content, intrinsic viscosity (ASTM D4603), and the acid number (AN) of polyethylene terephthalate (PET) is a lengthy and challenging process due to the sample’s limited solubility and the need to use different analytical methods. This application note demonstrates that the DS2500 Solid Analyzer operating in the visible and near-infrared spectral region (Vis-NIR) provides a cost-efficient and fast solution for a simultaneous determination of these parameters in PET. Vis-NIR spectroscopy allows for the analysis of PET in less than one minute without sample preparation or using any chemical reagents.

Determination of the vinyl content of silicone rubber is a lengthy and challenging process. First, the vinyl groups must be converted to ethylene by reacting with an acid, followed by the determination of the produced ethylene with gas chromatography (GC).This application note demonstrates that Vis-NIR (visible near-infrared) spectroscopy provides a cost-efficient and fast solution for the determination of vinyl content in silicone rubbers. With the DS2500 Solid Analyzer it is possible to obtain results in less than a minute without sample preparation or any chemical reagents.

PVC (polyvinyl chloride) foils with a PVDC (polyvinylidene chloride) coating are often used for high performance packaging films like pharmaceutical blister packs or in food packaging. In multi-layer blister films, the PVC serves as the thermoformable backbone structure, whereas the PVDC coating acts as a barrier against moisture and oxygen. The Water Vapor Transmission Rate (WVTR) and Oxygen Transmission Rate (OTR) are influenced by the composition and the thickness of the coating. A fast way to monitor PVDC coating thickness is with near-infrared spectroscopy. Results are provided in a few seconds, indicating when adjustments in the polymer production process are necessary.

The standard test method for ash content analysis is thermogravimetric analysis (TGA). Although TGA is easy to perform, it is time-intensive and requires the use of nitrogen gas. In contrast to the primary method, near-infrared spectroscopy (NIRS) is a fast analytical technique which can measure multiple parameters including ash content in polymers within one minute.

This application highlights Metrohm’s XTR® technology to identify colored polymers by extracting the Raman signal from spectra with strong background fluorescence.

The presence of water in expandable polystyrene (EPS) can have a negative impact on the thermal insulation properties, as it increases thermal conductivity. If EPS is exposed to a high moisture environment, additional water may be absorbed, which can further affect thermal insulation.Direct analysis of the moisture content by Karl Fischer titration requires the water to be extracted from the EPS, which involves several time-consuming steps. Therefore, determination of the water content with an oven system is preferred. As EPS expands when heated, the use of sample boats, as required by ASTM D6869, is not possible, as the EPS will contaminate the oven system. This Application Note describes the determination of water content in EPS using an oven system with closed sample vials. A determination takes about 7 to 14 min depending on the water content of the sample and the sample size.

The water content of 2-methyl-1,3-butadiene and 2,5-norbornadiene is determined according to Karl Fischer using a special solvent mixture to prevent unwanted side reactions.

The water content of plastic chips is determined according to Karl Fischer. Because of the low water content of the sample, the oven method (200 °C) and coulometric titration have to be used.

The water content determination by volumetric Karl Fischer titration is one of the most important analyses worldwide. Using an OMNIS system consisting of an OMNIS Titrator and an OMNIS Sample Robot, the fully automatic analysis of water content is possible in various products and matrices. The OMNIS Sample Robot is capable of running several different titrations in parallel. In this Application Note, we present the results of a volumetric Karl Fischer titration run in parallel to an aqueous acid-base titration on the same system. The water content is not influenced by the parallel running aqueous titration, allowing the combination of potentiometric titrations and Karl Fischer titrations on the same automated system.

The thermostability of polyvinyl chloride (PVC) was determined using the dehydrochlorination procedure at 180 °C. Comparison of the thermostability of pure PVC polymer, blended PVC (blended with stabilizer, plasticizer, filler) and blended PVC after processing.

Determination of the thermostability of polyvinyl chloride (PVC) using the dehydrochlorination procedure at 200 °C.

Determination of Ni, Co, and Fe in a PTA solution containing HCl.

4-Carboxybenzaldehyde can be reduced directly on the DME in a solution containing ammonium.

To prevent styrene from polymerization at ambient temperature, tertiary-butylcatechol (TBC) must be added as a stabilizer during storage and transport. TBC concentration levels in styrene need to be maintained between 10 - 15 mg/L. With optimum storage conditions, the process analyzers from Metrohm Applikon for photometric analyses ensure that the TBC concentration in styrene does not fall below this value. The method is based on ASTM D4590.

Polyurethanes are a class of synthetic polymers formed by reacting liquid di/polyisocyanates and polyols with a catalyst and various additives in a reactor. Polymer properties are modified with stepwise additions of these chemicals at different points in time depending on whether the process has reached an equilibrium. NCO functional groups from unreacted isocyanates must be quenched at the end for a finished product, and this parameter must be known to determine the proper chemical mixing ratio. A fast, non-destructive real-time measurement of %NCO can be obtained by using NIR spectroscopy with a probe seated directly in the reactor.

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

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.

The hydroxyl number is an important sum parameter for quantifying the presence of hydroxyl groups in a chemical substance. As a key quality parameter, it is regularly determined in various polymers like resins, paints, polyesterols, fats, and solvents. Unlike other standards, EN 4629-2 works pyridine-free and without refluxing at elevated temperatures for a longer time. The determination is based on the catalytic acetylation of the hydroxyl group. It is performed at room temperature, requires only a small sample volumen, and can be fully automated.This Application Note describes the potentiometric determination of the hydroxyl number in 1-octanol and polyethylene glycol according to EN 4629-2. Using the OMNIS DIS-Cover technique, all sample preparation steps can be fully automated. Furthermore, the use of an OMNIS Sample Robot allows parallel analysis of multiple samples. The average time per analysis for one sample is thus reduced from approximately 49 min to 25 min., considerably increasing productivity in the laboratory.

The hydroxyl number indicates the amount of potassium hydroxide in milligrams required to neutralize the acetic acid taken up on acetylation of 1 g of an unsaturated polyester resin (UPR) containing free hydroxyl groups. In this Application Note the determination of the hydroxyl number by automated, potentiometric titration according to EN ISO 2554 using KOH in methanol as titrant is described.

The hydroxyl number is an important sum parameter for quantifying the presence of hydroxyl groups in a chemical substance. As a key quality parameter, it is regularly determined in various polymers like resins, paints, polyesterols, fats and solvents. Unlinke other standards, ASTM E1899 works pyridine-free and without refluxing at elevated temperatures for a longer time. It is performed at room temperature, requires only a small sample size, is applicable to extremely low hydroxyl numbers (<1 mg KOH/g sample) and can be performed fully automatically. This Application Note describes the potentiometric determination of the hydroxyl number in 1-octanol and polyethylene glycol according to ASTM E1899, EN 15168 and DIN 53240-3. Using the OMNIS DIS-Cover technique all sample preparation steps can be fully automated. Moreover, the use of an OMNIS Sample Robot allows parallel analysis of multiple samples. The average time per analysis for one sample is thus reduced from approximately 24 min to 12 min., increasing productivity in the laboratory considerably.

The partial acid number (also partial acid value) describes the quantity of potassium hydroxide that is required for neutralizing all carboxyl-terminated groups and free acids plus half the anhydride groups in an unsaturated polyesterresin (UPR). This Application Note describes the determination of the partial acid value by automatic, potentiometric titration according to EN ISO 2114 using KOH in ethanol as titrant.

Although the process of building, validating and using a method is well-defined through software, the robustness of the method is dependent on proper practice of sampling, validation, and method maintenance. In this document, we will detail the recommended practices for using the multivariate method with NanoRam-1064. These practices are recommended for end users who are in the pharmaceutical environment, and can expand to other industries as well. This document aims to serve as a general reference for NanoRam-1064 users who would like to build an SOP for method development, validation and implementation.

Generally speaking, the gas extraction or oven method can be used for all samples which release their water when they are heated up. The oven method is indispensable in cases in which the direct volumetric or coulometric Karl Fischer titration is not possible, either because the sample contains disruptive components or because the consistency of the sample makes it very difficult or even impossible to transfer it into the titration vessel.The present Application Bulletin describes automatic water content determination with the aid of the oven technique and coulometric KF titration, using samples from the food, plastic, pharmaceutical and petrochemical industry.

Functional group and viscosity analysis (ASTM D789) of polyamides can be a lengthy and challenging process due to the sample’s limited solubility. This application note demonstrates that the DS2500 Solid Analyzer operating in the visible and near-infrared spectral region (Vis-NIR) provides a cost-efficient and fast solution for a simultaneous determination of the intrinsic viscosity as well as the amine, carboxylic, and moisture content in polyamides. With no sample preparation or chemicals needed, Vis-NIR spectroscopy allows for the analysis of polyamides in less than a minute.

Polypropylene (PP) is a general purpose resin widely used in industries such as electronic manufacturing and construction, as well as in packaging materials. PP resins must be melted first in order to be formed into the intended shape, and therefore flow properties are important characteristics which affect the production process. The standard procedure to analyze melt flow rate (MFR) requires a significant amount of work with packing the sample, preheating, and cleaning. With no sample preparation or chemicals needed, Vis-NIR spectroscopy allows the analysis of MFR in less than a minute.

The water content of organic peroxides is determined according to Karl Fischer using two-component reagents. To prevent any unwanted side reactions, the determinations are carried out at -20 °C.

Karl Fischer reagents contain buffer substances (usually imidazole) since the reaction constant is dependent on the pH value. A constant pH therefore ensures the most repeatable results. In 2015, imidazole was classified by European Union the as a CMR (carcinogenic, mutagenic or toxic) substance and the statement H360D was added, stating possible harm to fertility or a fetus. Meanwhile, other reagents free of imidazole are available for purchase. This Application Note summarizes test measurements with 34433 HYDRANAL™ NEXTGEN Coulomat AG-FI.

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.

The TSC SW Closed and TSC Battery cells are compact systems designed for measurements on air or moisture-sensitive materials, such as those used in batteries. In this document, two testing procedures are explained. The first procedure is withpotentiostatic cyclic voltammetry (CV), while the second is via electrochemical impedance spectroscopy (EIS).

1,3,5-trioxane is a heterocyclic compound formed by trimerization of formaldehyde. Trioxane is used for the production of polyformaldehyde plastics such as poly(oxymethylene) (POM) and solid fuels. Aqueous 1,3,5-trioxane solutions frequently contain trace triethylamine that requires quantification. This is performed on the Metrosep C 3 - 250/4.0 column with subsequent direct conductivity detection.

In the cumene process, phenol and acetone are produced from benzene and propylene. For a successful process control, it is crucial to monitor the sulfuric acid concentration, which impacts the acid-catalyzed cleavage of cumene hydroperoxide to yield phenol and acetone. This Process Application Note describes the online analysis of sulfuric acid using titration. In such hazardous environments, the analyzer can be ex-proof or located in an ex-proof shelter.

Compounds with carbonyl groups can be prone to oxidation for which reason their stability often decreases during storage or processing. The method presented here is suitable for the determination of aldehydes and ketones sparingly soluble in water.Samples are dissolved in deionized water. After a reaction with the hydroxylamine hydrochloride at 50 °C, carbonyl groups are quickly and accurately determined by potentiometric titration using the dUnitrode and sodium hydroxide as titrant.

The epoxy content of epoxy resins has a strong influence on the reactivity of the resins as well as on the properties of the coating obtained from the resin curing process. The epoxy content is thus an important quality control parameter for manufacturers as well as consumers. This analysis is based on the reaction of hydrogen bromide with the epoxy groups of the sample. Hydrogen bromide in turn is produced by the reaction of tetraethylammonium bromide (TEABr) with standardized perchloric acid. The standards EN ISO 3001 and ASTM D1652 describe the determination of the epoxy content expressed as epoxy equivalent weight (EEW) by titration. The use of a Titrando and Solvotrode easyClean instead of manual titration greatly increases the reproducibility and repeatability of the determination.

Enhance quality control in material and chemical production with NIRS. Fast, cost-effective, and no sample prep needed. Learn more in our eBook.

This e-book explains how Raman and near-infrared (NIR) spectroscopy enable rapid, nondestructive polymer analysis, ensuring high quality while reducing costs and waste.

Chemical manufacturing such as polyurethane production is characterized by a cost intensive production process combined with a negative ecological impact. These adverse effects can be significantly improved by using vibrational spectroscopy. This analytical technique can assist the operator of the plant to reduce costs and minimize the impact onthe environment as is demonstrated in the present white paper.