Determination of Total Arsenic in Wastewater and Sewage Sludge Samples by Using Hydride-Generation Atomic Fluorescence Spectrometry Under the Optimized Analytical Conditions

摘要

In this work, an improved hydride-generation atomic fluorescence spectrometry (HG-AFS) method for the determination of total arsenic (As) in wastewater and sewage sludge samples was applied. The samples were digested completely with mixtures of HNO_3 and HClO_4. Analytical conditions were studied and optimized through uniform experimental design U*_(10)(10~8) combined with a single factor test. A mathematical model was established, and a quadratic polynomial stepwise regression analysis by using the DPS software was employed to obtain the factors that impact the fluorescence intensity. This technique is then combined with a single factor test. The optimized experimental conditions were obtained as follows: PMT voltage was 305 V, lamp current was 70 mA, KBH_4 concentration was 2.0% (m/v), carrier liquid (HCl) concentration was 5% (v/v), carrier gas (Ar) flow rate was 300 mL min~(-1), and reaction acidity was 10% (v/v) HCl. The pre-reduction of all forms of As to As(III) was performed by using a mixed solution of 1% thiourea and 1% ascorbic acid. The content of total As was determined under the optimized experimental conditions. The detection limits for total As in wastewater and sewage sludge were 0.09 μg L~(-1) and 0.01 mg kg~(-1), respectively. The linear ranges were 0.24-100 μg L~(-1), and the recovery was 91.0-102.0%. The relative standard deviation (RSD, n = 5) for eleven replicate measurements of the certified reference materials containing 60.6 ± 4.2 μg L~(-1) As (certified sample of water) and 10.7 ± 0.8 mg kg~(-1) As (certified sample of soil) were 3.1% and 1.6%, respectively. The proposed method was validated by the analysis of certified reference materials and was successfully applied to the determination of total As in real samples of wastewater and sewage sludge with satisfactory results.