On-line solid phase extraction preconcentration of ultratrace amounts of zinc in fractionated soil samples for determination by flow injection flame AAS

摘要

A flow injection on-line solid phase extraction (SPE) preconcentration system coupled to a flame atomic absorption spectrometer (FAAS) was developed for the determination of zinc at the mug L-1 level. Zinc is complexed with 1-(2-thiazolylazo)-2-naphthol (TAN) in the pH range of 9.5-11.0 in the flow injection system and adsorbed onto a C-18-bonded silica gel micro column. The preconcentrated Zn-TAN complex was eluted with acidified methanol (pHsimilar to2). The eluent was injected directly into the nebulizer of a FAAS for measurement. The enrichment factor was 120 with a 1-min preconcentration time and a sample throughput of 30 h(-1). The detection limit corresponding to three times the standard deviation of the blank was 0.15 mug L-1 with a precision of 2.5% (RSD) for five successive determinations of 5 mug L-1 of Zn. No significant interference was observed from neutral electrolytes and cations of soil samples. The method was also applied successfully in the analysis of soils which were fractionated as per BCR (now Standards, Measurements and Testing Program) using both the direct and standard addition (SA) methods. [References: 23]