J.M. Eckert

Speciation of chromium in sea water

Dissolved chromium(III) and (VI) are coprecipitated separately from sea water, and chromium in the precipitates and particulate matter is determined by thin-film x-ray fluorescence spectrometry. In combination with an ultraviolet irradiation procedure whch releases bound metals, the method provides information about the speciation of chromium in near-shore surface sea water. The ratios of labile Cr(III)/(IIO+VI) generally lie in a narrow range (0.4–0.5) as do the sums of labile Cr(III) and (VI) concentrations (0.3–0.6 μg l−1). Bound chromium is variable (0–3 μg l−1) and constitutes from 0 to 90% of total dissolved chromium. Acidification of the samples in the traditional manner for trace metal determination is shown to alter the proportion of Cr(III) to Cr(VI).

The determination of dissolved and particulate vanadium in sea water by x-ray fluorescence spectrometry

Abstract Vanadium is coprecipitated from filtered sea water with a cobalt—pyrrolidinedithiocarbamate carrier complex at pH 4.0. The precipitate is collected as a thin film on a membrane filter (0.4-μm pore size) and, with the particulate material from the initial filtration, analysed directly for vanadium by x-ray fluorescence spectrometry. The detection limit, for 100-ml water samples and a counting time of 100 s, is 0.02 μg V l−1. The co-precipitation efficiency in the 0–5 μg l−1 range is 95% for vanadium(IV) or vanadium(V). Results for the determination of dissolved and particulate vanadium in sea-water samples are 1.4–1.7 μg l−1 and 0.06–0.61 μg l−1, respectively.

Reduction of chromium(VI) at sub-μg l−1 levels by fulvic acid

Abstract The rate of chromium(VI) reduction by a reference fulvic acid is studied by the separation of 51 Cr-labelled Cr(VI) from the reaction mixture with a cobalt tetramethylenedithiocarbamate carrier complex and γ-analysis of the carrier precipitates. This carrier is shown to suffer less from interferences than iron(III) hydroxide, the carrier used by previous workers to separate the reaction product, Cr(III). Information is obtained about the effects of pH, temperature and reactant concentrations on the rate of the reduction at the low levels (sub-μg l −1 ) of dissolved chromium that occur in clean natural waters. The method is used to study Cr(VI) reduction in an organic-rich, acidic lake water.

The determination of dissolved chromium(III) and chromium(VI) and particulate chromium in waters at μg l-1 levels by thin-film x-ray fluorescence spectrometry

A method is described for the determination of particulate chromium and dissolved chromium(III) and (VI) in water at μg l-1 levels. Particulate material is collected by filtration of the water sample through a membrane filter (0.4-μm pore-size). Chromium(III) and chromium(VI) are then coprecipitated, separately and in that order, with iron(III) hydroxide (at pH 8.5) and a cobalt—pyrrolidinedithiocarbamate carrier complex (at pH 4.0). Both precipitates are collected as thin films on membrane filters and, with the particulate material, analysed directly for chromium by x-ray fluorescence spectrometry. Detection limits, for a 100-ml water sample and counting times of 100 s, are 0.1 μg Cr l-1. The method is unaffected by sea salt and is applicable, without modifications, to river and estuarine waters.

An extraction—spectrophotometmc method for the determination of non-ionic surfactants

Abstract The surfactant is extracted into 1,2-dichlorobenzene as a neutral adduct with potassium tetrathiocyanatozincate(II), and zinc(II) in the extract is determined spectrophotometrically after addition of l-(2-pyridylazo)-2-naphthol and triethanolamine. With a 150-ml water sample, the limit of detection is 15 μg l -1 (as Triton X-100). The method requires only one extraction and is applicable, without modification, to fresh, estuarine and sea-water samples.

An atomic absorption spectrometric method for the determination of non-ionic surfactants

A method is described for the determination of non-ionic surfactants in the concentration range 0.05–2 mg l-1.Surfactant molecules are extracted into 1,2-dichlorobenzene as a neutral adduct with potassium tetrathiocyanatozincate(II) and the determination is completed by atomic absorption spectrometry. With a 150-ml water sample, the limit of detection is 0.03 mg l-1(as Triton X-100).The method requires a single phase separation step, is applicable, without modification, to fresh, estuarine and sea-water samples and is relatively free from interference by anionic surfactants; the presence of up to 5 mg l-1 of anionic surfactant (as LAS) introduces an error of no more than 0.07 mg l-1 (as Triton X-100) in the apparent non-ionic surfactant concentration.

Response of chromium(V) to the diphenylcarbazide spectrophotometric method for the determination of chromium(VI)

Abstract Two chromium(V) complexes are shown to respond to the diphenylcarbazide spectrophotometric method for the determination of chromium(VI), but with only 60% of the efficiency of Cr(VI). Acidification to pH 1–2 in the presence of dissolved organic matter results in substantial reduction of the Cr(V) within 24 h.

The determination of metals at ppb levels by thin-film x-ray fluorescence spectrometry after coprecipitation with a molybdenum carrier complex

Abstract A method is described for the determination of iron, cobalt, nickel, copper, zinc, cadmium and lead in water at μg 1 -1 levels, in which the metals are coprecipitated with a molybdenum—pyrrolidinedithiocarbamate carrier complex. The precipitate is collected as a thin film on a membrane filter (0.4-μm pore-size) and analysed directly by x-ray fluorescence spectrometry. Detection limits, for 100-ml water samples and counting times of 200 s per element, are 1 μg metal l -1 or lower. Total dissolved metal concentrations are obtained without boiling or u.v. irradiation of the water sample. The method is applicable to river and estuarine waters and is not affected by dissolved organic matter.

The determination of anionic detergents at p.p.b. levels by graphite furnace atomic absorption spectrometry

Abstract A method is described for the determination of anionic detergents at levels below 50 μg l -1 . The detergent anions are extracted into chloroform as an ion-association compound with the bis(ethylenediamine)copper(II) cation and determinations are completed by atomic absorption spectrometry with a graphite furnace atomizer. With a 750-ml water sample, the limit of detection is 2 μg l -1 (as linear alkyl sulphonic acids). The method requires a single extraction and is highly selective. It is applicable without modification to fresh, estuarine and sea-water samples.

Extraction-spectrophotometric determination of sulphide and sulphite in waters based on formation of the bis(2,9-dimethyl-1,10-phenanthroline) copper(I) ion

Abstract A spectrophotometric method is described for the determination of sulphide or sulphite. The bis(2,9-dimethyl-1,10-phenanthroline)copper(II) ion is reduced at pH 10 by sulphide in the presence of formaldehyde and by sulphide and sulphite in its absence. The resulting copper(I) complex is extracted into chloroform and measured. With any convenient sample volume between 1 and 100 ml, the limits of detection are 0.1 mg for sulphide and 0.25 μg for sulphite. The method is unaffected by iron(II) and nitrite, in concentrations of 100 and 1000 mg l -1 , respectively.