在1.8×10-2mol·L-1硫酸介质中,于30 ℃加热160 s时,草酸根对重铬酸钾、碘化钾和罗丹明6G之间的褪色反应具有显著的催化作用。结合流动注射技术,提出了一种催化光度法测定痕量草酸根的方法。草酸根的线性范围为0.10~1.20 mg·L-1,检出限(3s/k)为0.03 mg·L-1,进样频率18次·h-1。对0.30及0.80 mg·L-1 草酸根标准溶液进行平行测定,其相对标准偏差(n=11)分别为2.7%和1.6%。该方法用于菠菜、尿液中草酸根含量的测定,并以此样品为基体进行回收试验,测得回收率在93.3%~96.7%之间。

In 1.8×10-2mol·L-1 H2SO4 medium and heated at 30 ℃ for 160 s, the color-fading reaction among K2Cr2O7, KI and rhodamine 6G was significantly catalyzed by oxalate. By applying flow-injection technique, a FI-catalytic photometric method for determination of trace amount of oxalate was proposed. Linearity range was kept in the range of 0.10-1.20 mg·L-1, and limit of detection (3s/k) found was 0.03 mg·L-1, when the sampling frequency was 18 times per hour. Precision of the method was tested by addition of standard oxalate solutions with concentration of 0.30 and 0.80 mg·L-1 for 11 determinations, giving values of RSD′s 2.7% and 1.6% respectively. The proposed method was applied to the analysis of samples of spinach and urine, and using these samples as matrixes, recovery was tested by the standard addition method. Values of recovery found were in the range of 93.3%-96.7%.