Search

Gaseous hydrogen selenide (H2Se) generated by the addition of sodium tetrahydroborate (NaBH4) into an acidic aqueous sample was collected using an aqueous ammonia solution. The selenium (Se) concentration was determined using graphite furnace atomic absorption spectrometry (AAS). Several experimental conditions, such as the type of the collection solution, volume of NaBH4 and hydrochloric acid, and collection time, were optimized. In addition, the effect of coexisting ions was quantitatively evaluated and eliminated. The limit of detection for Se in a standard water sample was 1.3 ng/mL. The additional recovery of spiked Se in tap water and river water samples ranged from 98 ± 2.4 to 100 ± 2.2%. The proposed method facilitates simple and sensitive analysis for Se in water samples without H2Se gas generator for AAS. [ABSTRACT FROM AUTHOR]

The effects of counter-anions on the reversed-phase HPLC retention of zwitterionic quinolones were studied. Four counter-anions, perchlorate, tetrafluoroborate, trifluoroacetate, and dihydrogenphosphate, were used as mobile phase additives. HPLC analysis was performed at a mobile phase pH 3, to ensure the complete protonation of the piperizine ring and to suppress the ionization of the carboxylic acid groups of the analytes. Results showed that retention factors of all analytes increased to varying degrees with increasing counter-anion concentration. The increase in retention of the analytes is attributed to the chaotropic effect exhibited by the counter-anions. Complete separation of all the studied compounds was achieved by varying the type and amount of counter-anions present in the mobile phase. The changes in selectivity offered by these counter-anions would be beneficial, especially for developing chromatographic methods for the analysis of quinolones in different sample matrices. [ABSTRACT FROM AUTHOR]