作業環境空氣中六價鉻與三價鉻之定量分析

Quantitative Determination of Cr(VI) and Cr(III) from Air Samples in Workplace

本研究採用自動化分離技術－離子對逆相高效能液相層析（Ion-pair reverse phase HPLC）與高選擇性偵測技術－石墨爐原子吸收光譜（GFAAS）的結合，以進行六價鉻與三價鉻的定量分析。其目的在於降低由於複雜分析程序而產生的人為失誤與作業環境中其他物質所產生分析上的干擾。實驗中以逆相LC-8作為高效能液相層析的分析管柱，動相沖提液則由實驗發現以2.34％Acetonitrile/ 0.033M TBAOH/pH=6的水溶液可獲得良好的分離效果。在此分離系統中三價鉻與EDTA螯合形成帶負一價的錯離子，而六價鉻則以帶負二價的鉻酸根離子存在。這些待測物種與動相中的TBA+離子形成離子對。在0.7ml/min的沖提液流率條件下，三價鉻與六價鉻的滯留時間（retention time）分別為5.5與7.8分鐘：而自分析管柱流出之沖提液則以分液收集器（fraction collector）收集再利用石墨爐原子吸收光譜儀做定量分析。三價鉻與六價鉻的石墨爐原子吸收光譜分析偵測之檢量線線性迴歸係數分別為0.9990與0.9997而偵測極限分別為11.9與14.2pg。在15天的樣品穩定測試中，樣品分析回收率均高於85％且變異係數均小於6％。

The combination of ion-pair reverse-phase high performance liquid chromatography and graphite furnace atomic absorption spectrometry was used in the separation and quantitation of hexavalent chromium and trivalent chromium from air samples in workplace. The main focuses of this study are to develop automatic separation and specific detection techniques to reduce interference from complex matrix of air samples from Taiwan factories and to avoid human errors due to complicated pretreatment procedures in the reference methods. An RPLC-8 column was used as the analytical column and the mobile phase with 2.34% acetonitrile/0.033M TBAOH, pH 6 aqueous solution was found with optimal separation performance. In this separation system, trivalent chromium was treated with EDTA to form a [CrEDTA] complex and hexavalent chromium was in the form of Cr042-, these analytes formed ion pairs with TBA+ ion during elusion process in the separation column. At 0.7 ml/min eluent flow rate, the retention times for trivalent chromium and hexavalent chromium were found to be 5.5 and 7.8 min, respectively. The eluent was then collected by a fraction collector and transferred to the GFAAS for quantitation. The coefficients of correlation for trivalent chromium and hexavalent chromium were 0.9990 and 0.9997, respectively and their detection limits were 11.9 and 14.2 pg, respectively. For 15 days consecutive sample storage stability test, the recovery was above 85% and coefficient of variance was less than 6%.