真空紫外線による光酸化を用いるクロム（VI）と全クロムのフローインジェクション逐次定量

The photo-oxidation of Cr(III) to Cr(VI) with OH radicals formed under the irradiation of vacuum ultraviolet (VUV) was applied to the successive determination of Cr(VI) and total chromium by FIA. A sample solution containing Cr(III) was introduced into a quartz tube contacted to a VUV lamp radiating the light of 185 nm and 254 nm. Chromium(III) was oxidized to Cr(VI) quantitatively while passing through the quartz tube. The Cr(VI) was converted into a colored species with diphenylcalbazide in a reaction coil and the colored species was detected with an UV detector. For a sample solution containing Cr(III) and Cr(VI), without VUV irradiation, only Cr(VI) was determined. On the other hand, under VUV irradiation the total concentration of chromium, that is Cr(III) plus Cr(VI), was determined. The speciation of Cr(III) and Cr(VI) was easily performed by on/off switching the VUV lamp. Linear calibration was obtained at 0.05 – 1.0 mg dm−3 for both Cr(III) and Cr(VI). More than four samples were analyzed in one hour. This technique was successfully applied to synthesized plating wastewater.