硅酸盐在酸性介质中与钼酸铵反应生成硅钼黄,硅钼黄还原为硅钼蓝后,可被Hlb小柱定量萃取。在此基础上,建立了流动注射-固相萃取-分光光度(fI-SPE-VIS)测定水中痕量硅酸盐的新方法。反应生成的硅钼蓝经Hlb小柱萃取后,用水清洗去除杂质,nAOH溶液洗脱,分光光度法检测。实验对各参数进行了优化,优化后的参数为:洗脱剂浓度0.01MOl/l;试样上柱流速28.0Ml/MIn;洗脱流速3.5Ml/MIn;反应温度45℃;硅钼黄与硅钼蓝反应时间均为5MIn;钼酸铵混合溶液、草酸溶液、抗坏血酸溶液的用量分别为3.5,3.5和1.75Ml。本方法具有良好的重现性和灵敏度,测定含硅9.33μg/l的硅酸盐水样7次,rSd值为1.8%;选取不同的试样富集时间,可将定量分析的线性范围扩展为0.47~117μg/l;检出限0.18μg/l;回收率为96.8%~105%。可满足特殊工业用水中痕量硅检测的需要。The silicomolybdenum can be extracted by solid phase extraction technique on HLB column.Combining with sequential-injection analysis technique,a novel method for the determination of trace silicate in freshwater has been established.The silicomolybdenum blue was enriched by HLB column,and pure water was used to clean the column,then the silicomolybdenum blue was eluted by NaOH solution and detected by spectrophotometer.The optimized experimental parameters were as follows:the concentration of the eluent was 0.01 mol/L;the extracting and eluting flow rate was 28.0 and 3.5 mL/min,respectively;the reaction temperature was 45 ℃;the reaction time for both molybdosilicic heteropoly acid and silicomolybdenum blue was 5 min;the volumes of the ammonium molybdate,oxalic acid and ascorbic acid solution were 3.5,3.5 and1.75 mL,respectively.The proposed method showed the advantages of high sensitivity and reproducibility,for a water sample containing 9.33 μg/L Si,the RSD was found to be 1.8%(n=7).The linear range,with different calibration curves,was 0.47-117 μg/L.The detection limit was 0.18 μg/L,and the recovery was in the range of 96.8%-105%.厦门大学2007年度“凌峰计划”资助项
