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This Application Bulletins describes the polarographic determination of pyridoxine (vitamin B6). The method given allows determination in monovitamin and in some multivitamin preparations. The linear range of the analysis is also specified. The limit of detection is approx. 100 µg/L pyridoxine · HCI.

The Bulletin describes the determination of the following parameters in wine: pH value, total titratable acid, free sulfurous acid, total sulfurous acid as well as ascorbic acid (vitamin C) and other reductones.

This Bulletin describes the determination of arsenic by anodic stripping voltammetry (ASV) at the rotating gold electrode. A determination limit of 0.5 μg/L can be achieved with 10 mL sample solution. A differentiation between the As(III) concentration and the total arsenic concentration can be made by appropriate selection of the deposition potential. The analyses are performed with a special gold electrode whose active surface is located laterally; c(HCl) = 5 mol/L is used as supporting electrolyte. For the determination of the total arsenic content, As(III) and As(V) are reduced at -1200 mV by nascent hydrogen to As0, which is preconcentrated on the electrode surface. If the deposition is carried out at -200 mV then only As(III) is reduced; this allows the differentiation between total arsenic and As(III). During the subsequent voltammetric determination the preconcentrated As0 is again oxidized to As(III).

The titrimetric determination of nonionic surfactants on the basis of polyoxyethylene adducts (POE adducts) is described in the Bulletin. The basis for the determination is the transfer of the nonionic surfactant into a pseudo-cation compound and its precipitation titration with sodium tetraphenylborate (Na-TPB). The NIO electrode is used for the indication of the potentiometric titration. This Bulletin describes determinations in raw products, formulations and wastewater and draws attention to special features, possibilities, limits and disruptions.

The standard method postulated by DIN 38406 Part 16 describes the determination of Zn, Cd, Pb, Cu, Tl, Ni, and Co in drinking, ground, surface and precipitation (e.g. rain) water. Because the presence of organic substances in the water samples can strongly interfere with the voltammetric determination, a pretreatment with UV digestion using hydrogen peroxide is necessary. This digestion ensures the elimination of all organic substances without introduction of blank values. These methods can, of course, also be applied for trace analysis in other materials, e.g. trace analysis in the production of semiconductor chips based on silicon. Zn, Cd, Pb, Cu, and Tl are determined on the HMDE by means of anodic stripping voltammetry (ASV), Ni and Co by means of adsorptive stripping voltammetry (AdSV).

The effectiveness of antioxidants can be expressed as antioxidant activity. It can be readily determined using the Rancimat method. This is accomplished by first determining the induction time of a mixture made up of hog fat and the antioxidant to be investigated and then by determining the corresponding time for hog fat alone. The quotient expresses the efficiency of the respective antioxidant and is referred to as the antioxidant activity index (AAI).This Application describes the determination of the antioxidant activity index of five common antioxidants.

Anionic surfactants can be titrated with cationic surfactants and vice-versa. The Bulletin describes a multitude of substances that can be determined in this fashion and specifies the respective working conditions and parameters. In contrast to the classic two-phase titration in accordance with Epton, the titration with the anionic and cationic surfactants electrodes can be performed without chloroform. Furthermore, the equivalence point of the titration is difficult to determine in some cases with the Epton method and the titration cannot be automated.In many cases, a surfactant ISE is a remedy that is both environmentally friendly and suitable here. It was developed specially for application with potentiometrically indicated surfactant determinations.

This Bulletin describes a simple method for the determination of the calcium content in dairy products. The use of CuEGTA and the ion-selective copper electrode (Cu ISE) as indicator electrode allows the determination to be performed without time-consuming sample preparation. If the complexing agent EDTA is used as titrant instead of EGTA, the sum of calcium and magnesium is obtained. The magnesium content can then be calculated from the difference between the results of the two titrations.

Determination of the oxidation stability of foods with a low fat content is a challenge. As an alternative, the oxidation stability can be specified indirectly. To accomplish this, a determination is made as to the extent that a sample that has been mixed with a fat as a standard solution, e.g., hog fat, will change the oxidation stability of that standard solution. This is accomplished by first determining the induction time of the mixture made up of hog fat and the sample and then by determining the corresponding time for the lard alone. The quotient is referred to as the stability index (SI).

This Application Bulletin describes the determination of cadmium and lead at a mercury film electrode (MFE) by anodic stripping voltammetry (ASV). The mercury film is plated ex situ on a glassy carbon electrode and can be used for up to one day. With a deposition time of 30 s, the limit of detection is ß(Cd2+) = 0.02 µg/L and ß(Pb2+) = 0.05 µg/L. The linear working range for both elements goes up to approx. 50 μg/L using the same deposition time.