光化学还原-硅钼蓝分光光度法测定硅的研究

Determination of Silicon by Photochemical Reduction-Silicon-Molybdenum Blue Spectrophotometry

用紫外可见分光光度计,气相色谱仪,光化学反应箱和反应皿,以及阳光、铟灯、荧光高压汞灯、紫外灯等光源,研究了β硅钼黄-乙醇溶液体系的光化学还原反应,并建立了光化学还原-硅钼蓝分光光度测硅法。研究表明,发生该反应的光的有效波长<460nm;乙酸、丙酮、苯酚等不能,而其他水溶性的醇、醛、羧酸、醚、酯存在能导致该反应的发生;在0.8—2mol/L盐酸或0.4—1mol/L硫酸或1—3mol/L高氯酸、0.32%—0.48%的钼酸铵、4%—10%的乙醇中,≤8mg/L SiO_2的/β硅钼黄溶液光照10min就能定量还原成硅钼蓝;还原产物稳定,最大吸收波长为810nm,ε_(800)=2.7×10~4L·mol^(-1)·cm^(-1);分析微量二氧化硅S≤0.012%、RSD≤1.3%。初步探讨,乙醇与硅钼黄形成了电子给予体-接受体配合物(DAC),光照反应后有乙酸产生。

The photochemical reduction reaction of β silicon-molybdenum yellow-alcohol solution system was studied by ultraviolet spectrophotometer,gas chromatograph,photochemical reaction box and dish with sunlight,indium lamp, fluorescent high pressure mercury lamp and ultraviolet lamp as light source. A photochemical reduction-silicon-molybdenum blue speetrophotometric method for determining silicon was established. The study showed that the effective wavelength of light in this reaction was 〈 460nm. Acetic acid, acetone and phenol could not lead to the occurrence of this reaction,but the presence of other soluble alcohols, aldehydes, carboxylic acids,ethers and esters could induce the reaction. With addition of 0.8-2 mol/L hydrochloric acid or 0.4--1mol/L sulfuric acid or 1--3mol/L perchloric acid, 0. 32%-0. 48% ammonium molybdate and 4%-10% alcohol, β silicon-molybdenum yellow solution containing ≤ 8mg/L SiO2 could be reduced to stable silicon-molybdenum blue when irradiated by light for 10min （max. absorbed wavelength = 810nm, ε800 = 2.7 × 10 4 L ·mol-1·cm-1）. The analysis indicated trace silicon dioxide S≤0. 012 % and RSD≤1. 3%. Primary investigation revealed that alcohol and silicon-molybdem yellow formed electron donor-acceptor complex （DAC） and gcneraled acetic acid after light irradiation.