纳米钯基体改进剂-石墨炉原子吸收光谱法测定土壤和沉积物中镉的含量

Determination of Cadmium in Soil and Sediment by Graphite Furnace Atomic Absorption Spectrometry with Nanopalladium Matrix Modifier

取0.2~0.5 g已处理好的土壤或沉积物样品,用6 mL硝酸、2 mL盐酸和2 mL氢氟酸在微波升温程序下进行消解。冷却至室温,加入2 mL硝酸、1 mL氢氟酸和1 mL高氯酸,于130℃敞口加热赶酸,待全部消解且无黄烟后,继续加热至近干,用适量1%(体积分数)硝酸溶液溶解残渣,并定容至50 mL。以5μL的0.60 mg·L^(-1)纳米钯溶液为基体改进剂,在灰化2温度650℃、原子化温度1500℃的条件下,采用石墨炉原子吸收光谱法(GFAAS)测定上述溶液中镉的含量。结果表明,纳米钯从石墨炉干燥阶段起就提供保护氛围,能与镉作用形成合金防止其高温灰化损失,还可在较高的灰化温度下去除基体干扰,且在程序升温过程中对石墨管有涂渍作用,能使石墨管的使用寿命提高50%以上。镉的质量浓度在2.00μg·L^(-1)内与对应的吸光度呈线性关系,检出限(3.143s)为0.0078 mg·kg^(-1)。方法用于测定国家标准物质,所得测定值均在认定值范围内,测定值的相对标准偏差(n=6)为1.4%~3.7%。采用试验方法和文献报道的电感耦合等离子体质谱法测定实际土壤样品和沉积物样品,并利用F检验法和t检验法进行统计学评价,结果显示两种测定方法所测数据及其精密度均无显著性差异。

The treated soil or sediment sample(0.2-0.5 g)was taken,digested in 6 mL of nitric acid,2 mL of hydrochloric acid and 2 mL of hydrofluoric acid under program of temperature elevation of microwave digestion.After cooling to room temperature,2 mL of nitric acid,1 mL of hydrofluoric acid and 1 mL of perchloric acid were added and open heating was carried out to drive away acid at 130℃.After digestion was completed and yellow smoke disappeared,the solution was continued to heat to nearly dryness.The residue was dissolved in an appropriate amount of 1%(volume fraction)nitric acid solution,and its volume was made up to 50 mL.Cadmium in the above solution was determined by graphite furnace atomic absorption spectrometry(GFAAS),using 5μL of 0.60 mg·L^(-1)nanopalladium solution as matrix modifier at the ashing 2 temperature of 650℃and atomization temperature of 1500℃.As shown by the results,nanopalladium provided a protective atmosphere from the graphite furnace drying stage,and could react with cadmium to form an alloy to prevent the loss of high temperature ashing.Nanopalladium also could remove matrix interference at a higher ashing temperature,and had a coating effect on the graphite tube during the temperature programming process,which could increase the service life of graphite tube by more than 50%.Linear relationship beteewn the mass concentration of cadmiumcan and the corresponding absorbance was found within 2.00μg·L^(-1),and the detection limit(3.143s)was 0.0078 mg·kg^(-1).This method was applied to the determination of national reference materials,and the determined values were within the range of the certified values,with RSDs(n=6)of the determined values in the range of 1.4%-3.7%.This method and inductively coupled plasma mass spectrometry(ICP-MS)reported in the literature were simultaneously used to analyze the actual soil and sediment samples,and the F-test and t-test were used for statistical evaluation.It was shown that there was no significant difference in the determined data and their precision between the two methods.