Spectrophotometric determination of rhenium with di(2-pyridyl)ketone-2-furancarbothiohydrazone and other thiohydrazones

A simple rapid method is proposed for the determination of rhenium (as perrhenate) in which the brown-violet complex produced is measured at 546 nm. The system obeys Beer's law in the range 0.7–14.0 μg Re ml^-1; the molar absorptivity is 1.51 × 10⁴ l mol^-1 cm^-1 in ethanol and 1.64 × 10⁴ l mol^-1 cm^-1 for the complex extracted into methyl isobutyl ketone. Molybdenum (100-fold), tungsten (40-fold), copper (10-fold), and palladium (10-fold) are tolerable. Reactions of other metal ions such as Cu(II), Ni(II), Co(II) and Fe(II) with this ligand and reactions of perrhenate with analogous reagents are discussed.     

Evaluation of glycoalkaloids in tubers of genetically modified virus Y-resistant potato plants (var. Désirée) by non-aqueous capillary electrophoresis coupled with electrospray ionization mass spectrometry (NACE–ESI–MS)

The glycoalkaloid content of transgenic potatoes was evaluated by an optimised method based on non-aqueous capillary electrophoresis coupled on-line with electrospray ionization-mass spectrometry (NACE-ESI-MS). The potato material consisted of tubers from a conventional cv. Désirée and from three lines of modified plants resistant, intermediate and susceptible to infection by potato virus Y (PVY). The main glycoalkaloids were confirmed to be alpha-solanine and alpha-chaconine with parent ion masses m/z 852 and 868, respectively. In addition, an unknown minor peak at m/z 850.6 was found both in conventional (control) and susceptible line potato tubers. Such a compound exhibited an MS(2) spectrum with fragments ions at 704 and 396 m/z derived by loss of two ions, i.e. m/z 146 and 307, most likely corresponding to a rhamnose unit and a [glucose-(rhamnose)(2)] moiety, respectively. Up to 30-80-fold higher concentrations of total glycoalkaloids were found in the peel compared to flesh samples of all tubers examined. TGA content was nearly doubled in peel samples of resistant compared to control lines, and these levels were lower than the limit recommended for food safety, i.e. 20-60 mg of TGA per 100 g fresh weight. Moreover, it was established that tubers produced by virus-resistant clones are substantially equivalent in glycoalkaloid contents to those produced by conventional potato varieties.     

Characterisation of chlorinated hydrocarbons in a third generation candidate fish reference material (Limanda limanda) prepared under cryogenic conditions

Summary This paper describes the cryogenic preparation of 50 individual specimens of dab (Limanda limanda) from the Baltic Sea to produce a homogeneous fish material. 950 subsamples (8 g each) are stored in the gaseous phase over liquid nitrogen. Five series of analyses were randomly selected out of store. The results show that the obtained precision of 8 to 9% could be used as an indication unit for the deviation of the mean values of CHC concentrations from true values. If the analytical variability is 5%, the maximum inhomogeneity in the subsamples is 3–4%. It may be concluded that the subsamples of the candidate fish reference material (RM) are homogeneous enough for analytical purposes. Thus ESB (German Environmental Specimen Bank) material prepared in accordance with the standard operating procedure (SOP) [1] are valuable and appropriate reference materials. The prepared fish RM is suitable for the analysis of chlorinated hydrocarbons in fat containing marine samples.     

Comparison of different solid phase extraction materials and techniques by application of multiresidue methods for the determination of pesticides in water by high-performance liquid chromatography (HPLC)

Solid phase extraction materials and techniques (C-18 EMPORE^® disks, polystyrenedivinylbenzene (SDB) EMPORE^® disks, C-18 BondElut cartridges and ENVI-Carb cartridges) are compared for the preconcentration of 33 basic/neutral and 10 acidic/phenolic pesticides and three metabolites in water. The efficiency of the different extraction procedures was investigated by application of appropriate multiresidue separation methods by reversed phase-high performance liquid chromatography with UV-diode-array detection. Calibrations were performed with multicomponent standard mixtures and recoveries, relative standard deviations and determination limits were calculated for comparing the described enrichment methods. Experiences made in practical application of the different techniques and materials were also considered for the final evaluation.     

Stabilit?tsuntersuchungen an Uranylkomplexen substituierter Acetessigs?ureamide

Zusammenfassung Uranylionen bilden mit Acetessigsäureamiden Chelatkomplexe, deren Stabilitätskonstanten durch potentiometrische Bestimmung der Wasserstoffionenkonzentration ermittelt wurden. Der Einfluß der Substituenten der Amidgruppe auf die Stabilität der Komplexe wird diskutiert.

---

Investigations on the stability of uranyl complexes of substituted acetoacetamides

Uranyl ions form chelate compounds with acetoacetamides. The stability constants of these compounds have been determined by potentiometric pH-measurements. The variation of the stability constants with substituents of the amide group is interpreted.

---

---

Fräulein Sigrid Altfeld danken wir für experimentelle Mitarbeit.     

Correct identification of polychlorinated biphenyls in temperature-programmed GC with ECD detection

A method has been developed for peak identification of PCBs in GC with ECD detection under different temperature programs and isothermal conditions on two commonly used columns (DB-5 and DB-1701). This was achieved by means of accurate calibration of retention times based on the concept of the relative retention index P (i) and retention times of the selected PCB internal standards. The P (i) was calculated from the predicted retention times with the database of the retention parameters (A, B) and the migration equations. Through comparison of the calibrated and experimental retention times of PCBs in technical samples, it was shown that the developed method was effective for correct PCB comprehensive, quantitative, congener-specific (CQCS) analyses.     

FTIR-screening of carbonyl compounds in metal working fluid aerosols

Due to the complex composition of metal working fluids (MWF) the determination of all individual compounds is sometimes difficult and very expensive. Today the widely used method for the quantification of airborne MWFs consists of a non specific IR analysis of their C-H valence bands. With a new design of sample cell this inexpensive technique was extended to a more detailed screening of the MWF composition, especially the detection of carbonyl compounds in MWFs and their aerosols and vapors. The screening method was evaluated for the determination of concentrations of the aldehyde nonanal and the ketone diacetone alcohol in air in laboratory experiments. In preliminary workplace studies the applicability of this method to the (semi-)quantitative determination of carbonyl compounds in airborne MWFs is shown. The screening method was found to be very useful, specially to detect alterations in the composition of the MWF due to industrial use. Received: 16 January 1997 / Revised: 9 April 1998 / Accepted: 14 April 1998     

Determination of phenoxy acid herbicides by high-performance liquid chromatography and on-line enrichment

Summary Phenoxy acid herbicides have been determined by use of high-pressure liquid chromatography (HPLC). The separation efficiency of several stationary phases like octadecyl silica and nitril silica has been estimated using different mobile phases. Regarding the necessary experimental conditions for separating phenoxy acids, the enrichment phases for on-line operation have been tested by use of column switching. The method of sample enrichment is described and the enrichment factors have been calculated.

---

Bestimmung von Phenoxycarbonsäure-Herbiciden durch HPLC und On-line-AnreicherungI. Möglichkeiten der chromatographischen Trennung durch HPLC unter besonderer Berücksichtigung der On-line-Anreicherung der Herbicid-Verbindungen