HG AAS Research Articles

Preconcentration and separation of inorganic selenium on Dowex 1X8 prior to hydride generation—atomic absorption spectrometry

Exchange reactions between inorganic selenium species and chloride were studied on Dowex 1X8. The concentration exchange constants were determined with the batch technique at room temperature and used to predict the chromatographic enrichment and separation of tetra- and hexavalent selenium. A procedure for the determination of total selenium after digestion with permanganate and anion exchange preconcentration was also developed. The enrichment techniques were applied to the determination of Se(IV) and total dissolved selenium in drinking water and fresh water using flow injection hydride generation—atomic absorption spectrometry (HG—AAS). Results agreed with those obtained in a HG—AAS system where selenium was preconcentrated as hydrogen selenide in a trap at liquid nitrogen temperature.

Interferences from hydride-forming elements on selenium in hydride-generation atomic absorption spectrometry with a heated quartz tube atomizer

The interference from antimony(III), arsenic(III) and (V), bismuth(III), tin(IV) and tellurium(IV) on the determination of selenium(IV) in hydride-generation atomic absorption spectrometry (HG—AAS) was investigated systematically. Two commercially available units, a batch and a flow injection system, were compared. A dual system in which the interferent hydride was generated continuously, whereas the selenium hydride was generated intermittently and mixed with the interferent only shortly before the quartz tube atomizer, was used to further elucidate interference mechanisms. In the batch system, radical deficiency was found to be the main reason for the low tolerance of other hydride-forming elements. In the flow injection system, radical deficiency was not a major problem. The prevailing mechanism was an analyte atom decay interference due to surface alteration caused by deposition of the interferent in the quartz tube atomizer. Bismuth caused, in addition, a transport efficiency interference. Analyte decay interferences could be reduced by increasing the carrier gas flow. In the flow injection system, under optimized conditions, tolerance limits were 1–2 orders of magnitude higher than in the batch system. In most cases the big differences in the tolerance limits for hydride-forming elements reported in the literature could be interpreted on the basis of the conditions or the instrumentation used by these authors.

Determination of total selenium in water by atomic-absorption spectrometry after hydride generation and preconcentration in a cold trap system

A cold trap system for the determination of selenium by hydride generation—atomic absorption spectrometry (HG—AAS) is described. For a 30-ml sample the limit of detection is <2 ng/l. and the precision is better than 4% at the 30 ng/l. level. A number of digestion procedures for the destruction of organic matter prior to the determination of total dissolved selenium in water has been tested and compared. Concordant results were obtained except for oxidation by peroxodisulphate in strongly acidic solutions with a high content of organic material. The selenium concentrations found were in agreement with those obtained by HG—AAS after preconcentration by evaporation and dry ashing with the magnesium nitrate—nitric acid—hydrochloric acid method.

Trace elements analysis in steel and vacuum cast superalloys

A new sensitive analytical method for low level As and Bi determination in non-oriented electrical steel sheets and vacuum cast nickel superalloys was developed at our institute. Hydride generation/atomic absorption spectrometry (HG AAS) has proved to be a suitable method for the determination of hydride-forming elements, particularly at a low concentration level. The chemical and instrumental parameters were optimized. The chemical interferences of matrix elements and some metalloids were studied and eliminated. Certified standard reference materials were used to verify the method. The sensitivity, accuracy and reproducibility of data, and also the practical detection limit for each element, are gathered and assessed.