Retention of arsenate using genetically modified coryneform bacteria and determination of arsenic in solid samples by ICP-MS

A novel method for the retention of arsenate [As(V)] combining time-controlled solid-phase extraction with living bacterial biomass is presented. As(V) retention was carried out by exposing the extractant, consisting of a living double-mutant of Corynebacterium glutamicum strain ArsC1-C2, to the sample for a retention time of 1–7 min, before the arsenic distribution equilibrium between the sample solution and the extractant was established. The amount of As(V) retained in the biomass was measured by inductively coupled plasma-mass spectrometry (ICP-MS) after the sample had been treated with nitric acid. A theoretical model of the retention process was developed to describe the experimental retention-time profiles obtained with the bacterial cells. This relationship provided a feasible quantification of the retention process before steady-state was reached, providing that the agitation conditions and the retention time had been controlled. An analytical procedure for the retention/quantification of As(V) was then developed; the detection limit was 0.1 ng As(V) mL−1 and the relative standard deviation 2.4–3.0%. The maximum effective retention capacity for As(V) was about 12.5 mg As (g biomass)−1. The developed procedure was applied to the determination of total arsenic in coal fly ash, using a sample that had undergone oxidative pre-treatment.