Determination of trace silicon in water samples by reverse flow injection spectrophotometry

The determination of silicon in water by reverse flow injection spectrophotometry was developed using ammonium molybdate as color agent and methylaminophenol-sodium sulfite as reducing agent.The optimized technical conditions of flow injection were as follows: sulfuric acid-oxalic acid as reference solution;the sampling loop volume,250 μL;the lengths of reaction coils for mixing sample and carrying out reaction,both 3 m;the flow rate of sample solution,0.85mL/min;the flow rate of reference solution,color agent and reducing agent,all 0.40 mL/min.Under these optimized experimental conditions,a good calibration curve could be obtained with the linear range of 25-1500 μg/L and detection limit of 21.3 μg/L.200 μg/L Si(Ⅳ) standard solution was determined for 16 times,with the RSD of 2.2 %.The recovery of standard addition for actual water sample was 95 %-105 %.