自动消解-石墨炉原子吸收法测定土壤中铅含量
Determination of lead concentration in soil using automatic digestion and graphite furnace atomic absorption spectrometry
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摘要:
目的 通过优化试验条件，建立自动消解-石墨炉原子吸收法测定土壤中的铅含量。
方法 比较王水（盐酸：硝酸=3：1）、王水+氢氟酸、混酸（硝酸+盐酸+氢氟酸+高氯酸）3种消解体系对土壤标准物质的消解效果，考察不同石墨炉基体改进剂、灰化温度、积分规则对铅含量测定的影响，从而选择最佳的试验条件。计算自动消解-石墨炉原子吸收法在优化条件下的检出限，并通过测定4种土壤标准物质评估方法的适用性。
结果 王水+氢氟酸体系的消解效果最佳，耗时短、结果稳定；磷酸二氢铵（20 g/L）是有效的基体改进剂，能降低基体干扰，改善峰形；灰化温度为800℃时，背景干扰明显下降，原子吸收增强；峰高积分比峰面积积分所得的铅含量更接近标准值，且数据更稳定。在优化的工作条件下，该方法的检出限为0.080 mg/kg，线性范围为5.0~50.0 μg/L。对4种土壤标准物质的测定结果全部在标准值范围内。
结论 自动消解-石墨炉原子吸收法采用王水+氢氟酸作为消解体系，选择磷酸二氢铵作为基体改进剂，灰化温度设定为800℃，以峰高积分规则计算土壤铅含量，在此优化条件下，消化时间短、重现性好，适合不同土壤样品铅含量的检测。
Abstract:Objective To establish a method for determination of lead concentration in soil using automatic digestion by graphite furnace atomic absorption spectrometry (AAS) after optimizing experimental conditions.
Methods The digestion effects on soil standard substance were compared among three kinds of digestive systems in cluding aqua regia (hydrochloric acid:nitric acid=3:1), aqua regia+hydrofluoric acid, and mixed acid (nitric acid+hydrochloric acid+hydrofluoric acid+perchloric acid). The influences of different graphite furnace matrix modifiers, ashing temperature, and in tegral rules on the determination of lead were investigated, and the optimal test conditions were selected. The limit of detection of automatic digestion-graphite furnace atomic absorption spectrometry was measured, and the applicability of the method was evaluated through determining four kinds of soil standard substances.
Results The assay proved to be time-saving and stable using aqua regia+hydrofluoric acid as digestive system. Ammonium dihydrogen phosphate (20 g/L) was an effective matrix modifier to reduce matrix interference and improve peak shape. The background interference was decreased and atomic absorption was enhanced obviously when ashing temperature was 800℃. The le ad content obtained by peak height integral was more stable and accurate than that by peak area integral. Under the optimized conditions, the linear range was 5.0-50.0μg/L, and the limit of detection was 0.080mg/kg. By applying the method, the determination results of four different soil standard materials were all within standard uncertainty range.
Conclusion Automatic digestion-graphite furnace atomic absorption spectrometry is developed for the determination of lead in soil, in which aqua regia+hydrofluoric acid is used as digestive system, ammonium dihydrogen phosphate is chosen as matrix modifier, ashing temperature is set at 800℃, and peak height integral is selected as calculation rule. The method is proved to be time saving, reproducible, and suitable for lead detection in massive soil samples.
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