Analytical and Bioanalytical Chemistry (v.334, #4)

To evaluate pollution effects on ecosystems, more and more plant and animal samples are analyzed for their concentrations of pollutants and nutrient elements. Since chemical analyses of biological materials are largely influenced by matrix effects, their accuracy depends on the availability of reference materials. Unfortunately only very few such standards exist so far. The described interlaboratory comparison of beech leaves from Baden-Württemberg demonstrates the possibility of producing reference materials from selected organisms, which — though not certified — are sufficient for research projects. Apart from their function as reference materials, those standards show typical levels of elemental concentrations for their region of origin. First results are introduced.

Basic considerations are discussed and conditions are described for the careful production of oxide macro-samples in the mass range of 200 to 750 g, starting from compounds of tested purity. Solid state reactions were performed at high temperatures. Compounds sensitive to heating were added after heat treatment in a way which ensured homogeneity. The uptake of CO2/H2O during manipulations was controlled. The homogeneity of the samples was investigated as well as the success of the experimental approach to their desired, nominal analysis. Even after only moderate mechanical homogenisation, nominal and experimental values were found to be identical (within the limits of repeatability of the test methods), provided compounds with a sufficiently small grain size and of high enough a purity were used. The results obtained on these samples showed that spending a greater analytical effort to achieve the desired analysis, was unnecessary. A thoroughly performed control analysis — e.g., by reconstitution of the sample portion — was sufficient to exclude erroneous production steps. Then the nominal analysis was used to establish the internal laboratory certificate.

The determination of molybdenum(VI) in aquatic media by polarography, voltammetry and adsorptive stripping voltammetry using the formation of a Mo-chlorate-mandalic acid complex at +100 mV (SCE) is described. The 3 sblank-detection limit is 0.1 nmol/l with differential pulse adsorptive stripping voltammetry (DPAdsSV, catalytic current). The calibration graphs are linear up to 200 nmol/l for the latter, 400 nmol/l for staircase voltammetry without accumulation time and 1 mg/l for staircase polarography. The accuracy of the DPAdsSV method was checked by analysis of a standard reference water material. The utility of differential pulse voltammetry was tested in different aquatic media, e.g., tap water, ground water, surface water.

The effect of some surfactants and protective colloids on the absorbance of the iron(III)-phenylfluorone complex has been investigated. The binary complex formed at pH 9.0 show a molar absorptivity of 7.5×104 l · mol−1 · cm−1 at 530 nm. In the presence of 2% Triton X-100, at the same pH, the molar absorptivity of the sensitized complex was 1.19×105 l · mo−1 · cm−1 at 555 nm. Full colour development of the sensitized complex occurred within 25 min and Beer's law was followed up to 0.53 ppm of iron. The molar ratio and continuous variation methods indicated a 1∶3 metal-ligand ratio for the sensitized complex. The effect of various amounts of different ions has been studied under the experimental conditions and some masking agents were recommended. The method has been applied to the determination of iron in copper and nickel metals and some non-ferrous alloys.

Derivatization of nitrophenols in water with pentafluorobenzoylchloride for a gas-chromatographic determination with electron capture detection is achieved by phase transfer reaction using dicyclohexyl-18-crown-6 as catalyst.

A kinetic study of the colour reactions between butylated hydroxyanisole (BHA) and Gibbs and Ehrlich reagents carried out with a stopped-flow system is reported. Kinetic methods for the determination of BHA were developed with both reagents. The parameters used were the initial rate and the signal amplitude. The use of a diode-array photodetector allowed the application of an amplification method with a decreased detection limit. The different kinetic methods developed were satisfactorily applied to the determination of BHA in different commercial oil samples. Analytical recovery data are also reported.

A technique is presented for the extraction of free and conjugated drugs and related compounds out of small quantities of urine. The method is designed in such a way that many samples can be tested for a great number of substances at the same time. Furthermore, we tried to achieve a high quality analysis using when ever possible chemicals with relatively low toxicity to men and environment. Therefore we avoided e.g., halogenated hydrocarbons. The detection of the substances is only performed by thin-layer chromatography (TLC) using well known reagents, like ninhydrin, Dragendorff, iodoplatinate and ferric chloride solutions. If necessary, the extracts can also be used with other Chromatographic techniques, particularly with GC/MS, if a substance has to be clearly identified. Approximately 500 authentical urines have been analyzed in a 1 year period using the method described. We found about 75 different substances. These results are presented in a table.

The sampling technique described here combines approaches found in the Ames-sampling technique [7], the EPA 5 sampling train [4] and a recently published high volume sampling method [17]. The sampling strategy leads to one solid sample for Soxhlet extraction. The use of an all-glass apparatus minimizes the absorption of organic trace compounds. Spherical joints (KS) give the apparatus flexibility without losing stability, while a rack eases the handling during sampling, also under demanding field conditions.

New books (363-364).