Ultrasonic extraction-ozonation sequential sample treatment for the determination of arsenic in environmental certified reference materials by hydride generation-atomic fluorescence spectrometry

A sample pretreatment method based on ultrasound-assisted extraction followed by ozonation is developed for sensitive determination of total As in biological and environmental certified reference materials and an unknown plant sample ( Acacia dealbata) by flow injection and continuous-flow hydride generation - atomic fluorescence spectrometry. The method is meant to minimize the use of corrosive and oxidizing acids for sample decomposition and common errors in trace analysis. Problems derived from introduction of sonicated extracts in continuous flow and flow injection manifolds in combination with an atomic fluorescence detector, such as excessive foaming and flame instability, are addressed. The following certified reference materials (CRMs) were employed for method assessment: BCR CRM 482 lichen; BCR CRM 60 and 61 aquatic plants; BCR CRM 279 sea lettuce; NIST 1633b fly ash; BCR 320 river sediment; RTC CRM 024-050 soil. Effect of variables such as extraction time, ultrasound amplitude, concentration of extractant acid, sample mass, drying mode, and particle size was investigated. Leaves of Acacia dealbata were also employed for method development. Limits of detection ranged from 0.03 to 0.15 mu g/g As depending on the sample. Between-batch precision values ranged from 2% to 11%. Sample throughput was 40 hr(-1) with flow injection.