顺序注射在线稀释微量进样技术及其在自动光度法测定水中亚硝酸盐的应用

Sequential Injection-On-line Dilution Micro-sample Introduction Technique and Its Application to Automatic Photometric Determination of Nitrite in Water Samples

以测定环境水样中的亚硝酸盐为例，采用顺序注射技术，提出了一种智能化在线微量进样稀释分析系统（SIA系统）。将测定过程中分光光度计输出的模拟电压信号，反馈至顺序注射仪，判断是否需要稀释。当获得的电压信号值小于305mV（约相当于吸光度值0．8）时，SIA系统进入稀释程序，否则，则进入直接测定程序，两种程序均自动完成。直接测定和稀释测定的线性范围分别为1～50μmol·L^-1和50-500μmol·L^-1NO2^-。分别在N07浓度水平为10，200μmol·L^-1时作精密度试验，测得相对标准偏差（n=11）依次为0．7%和1．0%。该分析系统特别适合于自动分析过程中被测物质浓度变化较大而需要在线稀释的情况。

By applying the sequential injection technique, an automatic intelligent on-line dilution microsample introduction system （SIA system） was proposed. Operation mode and analytical characteristic of this system was studied by its application to the photometric determination of NO2^- in water samples. The analog voltage signal output of the spectrophotometer in the course of measurement were fed back to the sequential injector, to judge whether dilution is needed or not. If the value of voltage is smaller than 305 mV （corresponding to the absorbance value of 0.8）, the SIA system will proceed to the dilution program, otherwise, proceed to the direct determination program, both of which will perform automatically. Linearity ranges of the calibration curves were found ranged from 1 to 50μmol·L^-1 of NO2- without dilution, and from 50 to 500μmol·L^-1 of NO2^- with dilution. Values of RSD＇s （n=11 ） obtained were 0. 7% if （at concentration level of 10μmol·L^-1 ）, and 1.0% （at concentration level of 200 μmol·L^-1）. The SIA system proposed was found to be feasible for automatic analytical process where large variation of concentration of analyte is encountered and on-line dilution is necessary.