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[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5.0~50.0μg/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。
[Objective] The aim was to establish an automatic digestion-graphite furnace atomic absorption spectrometry for determination of lead in soil by optimizing the test conditions. [Method] The digestion effects of three digestion systems including aqua regia (hydrochloric acid: nitric acid = 3:1), aqua regia + hydrofluoric acid and mixed acid (nitric acid + hydrochloric acid + hydrofluoric acid + perchloric acid) Different graphite furnace matrix improvers, ashing temperature, integral rules on the determination of lead content, so as to select the best test conditions. The detection limit of automatic digestion - graphite furnace atomic absorption spectrometry under optimized conditions was calculated and the applicability of four soil reference materials assessment methods was evaluated. [Result] The aqua regia and hydrofluoric acid systems had the best digestion effect, short time-consuming and stable results. Ammonium dihydrogen phosphate (20 g / L) was an effective matrix modifier, which could reduce the matrix interference and improve the peak shape. When the temperature is 800 ℃, the background interference obviously decreases and the atomic absorption increases. The lead content of peak height integral is more close to the standard value, and the data is more stable. The detection limit of this method was 0.080 mg / kg and the linear range was 5.0 ~ 50.0 μg / L under the optimal working conditions. The results of the determination of four kinds of soil reference material all in the standard value range. [Conclusion] The automatic digestion - graphite furnace atomic absorption method using aqua regia + hydrofluoric acid as digestion system, ammonium dihydrogen phosphate as matrix modifier, ashing temperature was set at 800 ℃, and the peak height integral rule was used to calculate the soil Pb , Under the optimized conditions, digestion time is short, good reproducibility, suitable for the detection of lead in different soil samples.