高效液相色谱-氢化物发生-原子荧光光谱法测定植物样品中的4种砷形态

HPLC-HG-AFS Determination of 4 Arsenic Species in Plant Samples

以0.15mol·L^(-1)硝酸溶液为提取溶剂超声提取植物样品2次,提取溶液经CNW ICGuard RP小柱净化后,进入高效液相色谱,以Hamilton PRP-X100色谱柱为固定相,以25mmol·L^(-1)磷酸氢二铵-甲酸溶液(pH 6.0)为流动相进行等度洗脱,分离其中的亚砷酸[As(Ⅲ)]、二甲基砷酸(DMA)、一甲基砷酸(MMA)和砷酸[As(Ⅴ)],4种砷形态在9min内可完全分离。将分离出的4种砷形态引入氢化物发生-原子荧光光谱仪进行测定,其中,硼氢化钾溶液(还原剂)的质量浓度为22.5g·L^(-1),盐酸溶液(载流)的浓度为1.2mol·L^(-1)。结果表明:4种砷形态的质量浓度在5~100μg·L^(-1)内与其对应的峰面积呈线性关系,检出限(3S/N)为0.20~0.46μg·L^(-1)。采用标准加入法进行回收试验,得到回收率为80.0%~101%,测定值的相对标准偏差(n=6)为2.1%~5.0%。按此方法测定大米、芥菜、空心菜、莲藕、柑橘叶片等植物样品中的砷形态,均未检出MMA,检出As(Ⅲ)的质量分数(0.053~0.81mg·kg^(-1))相对较高,且该方法测得砷形态总和占按照GB 5009.11-2014测得总砷含量的百分比为84.2%~104%。

The plant sample was ultrasonically extracted with 0.15 mol·L^(-1) nitric acid solution for 2 times.After centrifugation,the extraction solution was purified by the CNW IC-Guard RP column,then introduced into HPLC using Hamilton PRP-X100 chromatographic column as stationary phase and 25 mmol·L^(-1)(NH4)2 HPO4-HCOOH solution(pH 6.0)as mobile phase in isocratic elution.The 4 species of arsenic(arsenite,dimethylated arsenic,monomethylated arsenic and arsenate)in sample solution were completely separated within 9 min,then the 4 species of arsenic were determined by HG-AFS with 22.5 g·L^(-1) potassium borohydride solution as reductive agent and 1.2 mol· L^(-1) hydrochloric acid solution as carrying current.The results showed that linearity relationships between peak area and mass concentration of the 4 species of arsenic were kept in the same range of 5-100μg·L^(-1),with detection limits(3 S/N)in the range of 0.20-0.46μg·L^(-1).Values of recovery obtained by standard addition method were found in the range of 80.0% to 101%,and RSDs(n=6)of the measured values were found in the range of 2.1% to 5.0%.The proposed method was used for determination of plant samples including rice,mustard,swamp cabbage,lotus root,citrus leaves,and all of samples contained high mass fraction of arsenite(0.053-0.81 mg·kg^(-1))while monomethylated arsenic was not detected,with percentage of the total arsenic species measured between this method and national standard method of GB 5009.11-2014 in the range of84.2%-104%.