Bifunctional magnesium oxide crystal successively as adsorbent and matrix modifier for preconcentration and determination of arsenic by graphite furnace atomic absorption spectrometry

A novel method for determination of total inorganic arsenic in water samples, based on magnesium oxide crystals quantitatively preconcentration and graphite furnace atomic absorption spectrometry (GFAAS) detection has been developed. As the MgO crystals could successively act as the adsorbent and matrix modifier, the method presents great potential in practical routine analysis of inorganic arsenic. With optimization of the experimental conditions, 1.5 mg of MgO was added into 4.0 mL water sample and ultrasonic dispersing 15 min for adsorbing the arsenic at first. Then, the mixture was centrifuged 5 min for separating the adsorbents and the water solution; the deposits were collected and dissolved with HNO3 for arsenic determination. The enrichment factor of 13, limit of detection (LOD) of 0.087 μg L− 1, relative standard deviation (RSD) of 4.5% (n = 7, c = 2.0 μg L− 1) were achieved under the optimized conditions. The procedure was validated by analysis of certified water sample (GBW08605), which results in good agreement between the certified and the found values. The method was further demonstrated for analysis of lake water, snow water and tap water, and satisfactory spiked recoveries of 98.5% to 103.0% were achieved for these samples. These preliminary results indicated the present method was practical and accurate for analysis of trace-arsenic in natural water samples.