一种检测低浓度化学需氧量的双波长光谱方法

提出了一种基于双波长光谱法快速测定低污染水样的化学需氧量(COD)的方法.结果表明:对低COD样品采用440和560 nm双波长的测定方法可有效地提高可靠性和检测灵敏性.该法的灵敏度(即定量检测下限)为8.6 mg·L-1;在低COD范围标样(≤100mg·L-1)的准确性对比测定相对标准误差在2%～15%的范围内.另外,该方法不需要用标准样品进行校正,可以通过光谱法检测消解液中重铬酸根的消耗直接计算出样品的COD值,使实验步骤得到了进一步的简化.

A dual-wavelength spectroscopic method for the low chemical oxygen demand determination

The present paper reports a dual wavelength spectroscopic method for the determination of chemical oxygen demand (COD) of low content samples, based on the absorption measurement at 440 and 560 nm. Since the absorptivities of Cr3+ at these two wavelengths are the same, a net absorption from dichromate ions can be determined by subtracting the absorption at 560 nm (only contributed by Cr3+) from the absorption at 440 nm The results showed that the detection limit of quantification is 8.6 mg x L(-1) and the relative standard deviations are in the 2%-15% range for the low COD standard samples (< or = 100 mg x L(-1)) in this proposed method. Further more, the method does not require calibration based on the standard samples. The present method is simple, reliable, and accurate; it is suitable for the application in a mass testing for low COD samples.