电感耦合等离子体发射光谱法测定枸杞中的维生素C

Determination of vitamin C in Lycium chinense by inductively coupled plasma atomic emission spectrometry

目的建立电感耦合等离子体发射光谱法(inductivelycoupledplasmaatomicemissionspectrometry,ICP-AES)测定枸杞中的维生素C (vitamin C, VC)的方法。方法枸杞样品用2%柠檬酸匀浆提取,经离心分离后,取1.00mL上清液,加入1mL硫酸铜标准溶液,1mL2%硫氰酸铵溶液,0.5mL盐酸-醋酸钠缓冲液,0.5 mL饱和氯化钾溶液充分混和,摇匀,反应10 min后用高速离心机10000 r/min离心5 min,分离后用ICP分别测定沉淀和溶液中的铜,从而求出VC的含量。结果沉淀法和溶液法测定Vc在0~100mg/L范围内呈良好的线性关系,线性相关系数r2≥0.999,相对标准偏差(relativestandarddeviation,RSD)为3.3%和2.3%(n=7),加标回收率均高于85.0%(n=5)。沉淀法检出限为0.4 mg/100 g,定量限为1.6 mg/100 g;溶液法检出限为0.2 mg/100 g,定量限为0.8 mg/100 g。结论此方法具有精密度高、稳定性好、回收率高,不受样品颜色干扰等特点,有较好的应用前景。

Objective To establish a method for the determination of vitamin C in Lycium chinense by inductively coupled plasma atomic emission spectrometry(ICP-AES). Methods The sample was extracted with 2% citric acid homogenate. After centrifugation, 1.00 mL of supernatant was taken with 1 mL copper sulfate standard solution, 1 mL 2% ammonium thiocyanate solution, 0.5 mL hydrochloric acid sodium acetate buffer solution and 0.5 mL hydrochloric acid sodium acetate buffer solution added. The saturated potassium chloride solution was fully mixed, shaken and reacted for 10 min, then centrifuged with a high-speed centrifuge at 10000 r/min for 5 min. After separation, the copper in the precipitate and solution was determined by ICP, so as to obtain the content of VC. Results There was a good linear relationship in the range of 0-100 mg/L in determination of vitamin by precipitation method and solution method. The linear correlation coefficient r2≥0.999, and the relative standard deviation(RSD) were 3.3% and 2.3%(n=7). The average recovery were all higher than 85.0%(n=5);the detection limit of precipitation method was 0.4 mg/100 g, and the limit of quantification was 1.6 mg/100 g;the detection limit of solution method was 0.2 mg/100 g, and the limit of quantitation was 0.8 mg/100 g. Conclusion This method has the characteristics of high precision, good stability, high recovery rate, not affected by the colors of the sample, which has a good application prospect.