Dispersive liquid phase microextraction (DLPME) combined with graphite furnace atomic absorption spectrometry (GFAAS) for determination of trace Co and Ni in environmental water and rice samples

A new method of dispersive liquid phase microextraction (DLPME) combined with graphite furnace atomic absorption spectrometry (GFAAS) was proposed for the determination of trace Co and Ni using 1-(2-pyridylazo) 2-naphthol (PAN) as chelating reagent. Several factors influencing the microextraction efficiency of Co and Ni and their subsequent determinations, such as pH, extraction and disperser solvent type and their volume, concentration of the chelating agent, extraction time and ashing temperature and atomization temperature were studied, and the optimized experimental conditions were established. After extraction, the enrichment factors were 101 and 200 for Co and Ni, respectively. The detection limits of the method were 21 and 33 pg/mL for Co and Ni, and the relative standard deviations (R.S.Ds.) for five determinations of 0.5 ng/mL Co and Ni were 7.5% and 8.2%, respectively. The results for the determination of Co and Ni in East Lake water, Yangtse River water, Dongbei rice and spiked samples have demonstrated the accuracy, recovery and applicability of the proposed method. To validate the proposed method, two certified reference materials of Environment Water (GSBZ50009-88) and NIES No.10-b rice flour were analyzed, and the determined values were in good agreement with the certified values.