No abstract

KeyWordsGas chromatography -mass spectrometry Extraction of polychlorinated compounds Soil and waste water Fluidized-bed extraction Soxhlet extraction SummaryThe extraction and determination of polychlorinated organic compounds, like hexachlorobenzene, pentachlorobenzene, octachlorostyrene and polychlorinated biphenyls in soils and solid wastes continues to be a subject for study In this work Soxhlet extraction and a new extraction technique, fluidized-bed extraction, have been compared. The extraction of polychlorJnated organic compounds by this technique has been optimized using experiemental design procedures. The variation of the number of extraction cycles, composition of extraction solvent (mixtures of n-hexane-acetone) and the holding time after reaching the heating temperature were considering as experimental variables to generate a surface response design. Gas chromatography with mass spectrometric detection was used to determine levels of the analytes in the extracts. Extraction and analysis of a certified reference material (BCR CRM 392) showed the applicability of the method.

No abstract

A method for the voltammetric determination of vanadium(v) using a carbon paste electrode in situ modified with cetyltrimethylammonium bromide (CTAB) is described. Vanadium is preconcentrated at the electrode surface via its anionic oxalate complex from acidic solution (0.01 M oxalic acid, 0.25 mM CTAB, pH 2.2) at a potential of -0.9 V [vs. the saturated calomel electrode (SCE)]. Simultaneously during accumulation, vanadium(v) in the complex is reduced to its tetravalent state. Differential pulse anodic stripping voltammetry exploiting the reoxidation can be used for the determination of trace levels of vanadium(v). Linearity between current and concentration exists for a range of 5 to 200 pgL-' V v with a preconcentration time of 1 min. The limit of detection (calculated as 3 u) is 0.07 pg.L-' with a preconcentration time of 10 min.

No abstract