空氣中六價鉻及三價鉻 分析方法研究

Abstract

自1797年法國化學家發現鉻，開啟了鉻在工業上使用的歷史序幕。其廣泛的運用在各大工業中，也因此鉻的職業暴露所造成的危害為人所注目。而自然界中主要以三價鉻及六價鉻的形式存在，三價鉻為人體必須微量元素但六價鉻卻為已確定人類致癌物，在此對人體健康危害差距極大的情況下，將三價鉻及六價鉻分開檢測確是必要的。 假以美國職業安全衛生署(OSHA)預定在2005年將容許濃度降低一百倍為0.001 mg/m3，我國勞工委員會(CLA)也考慮降低容許濃度。當法規標準降低前，經考量其是否足夠信度、感度之量測方法，在整體職業衛生上是很重要的一環。目前傳統分析方法中常用的是光譜分析法，容易受到環境中常見陽離子的光譜干擾而高估環境暴露，因此NIOSH METHOD 7703中提出使用強陰離子交換樹脂固相萃取的方式將此干擾降低，可獲致較佳的分析結果。經本文作者簡化方法後，NIOSH METHOD 7703方法之偵測極限可達0.0022 μg/mL，可適用的樣品濃度範圍為0.11~6.67 μg/mL，相當於以流速2 mL/min採樣八小時之濃度為0.11~6.95 mg/m3。且本方法仍可確實將三價鉻陽離子分離出，僅六價鉻(CrO42-)進行分析定量。 又為繼續提高靈敏度，本研究也使用超音波震盪/陰離子交換管柱的高效能液相層析/感應耦合電漿質譜法將三價鉻及六價鉻分離，並且將偵測範圍降低至μg/L。利用碰撞氣體控制質譜分析上的干擾以提供敏感度、準確度較高的方法。在使用氦氣碰撞模式下有最佳的偵測極限，三價鉻與六價鉻分別為0.21 μg/L與0.26 μg/L，檢量線濃度為1~100 μg/L。在濾紙標準添加法中，以1 M NaOH浸泡過之PVDF濾紙同時添加三價鉻及六價鉻，在每個樣品含量低於250 ng時，兩者回收率分別可達88%及103%。顯示以此濾紙同時採集三價鉻及六價鉻效果遠較PVC及MCE濾紙佳。

Since 1797, L. N. Vauquelin discovered chromium. It was used in industries until now. Chromium is used widly in industries. AS a result, the occupational exposure to chromium frequently occurs in work place. Trivalent chromium and hexavalent chromium are the predominant chromium species in the natural environment. Trivalent chromium is known to be an essential trace element, on the other hand, haxavalent chromium is determined as a carcinogenic substance. Due to the difference in the human health effect between trivalent and hexavalent chromium . It is obvious that speciation is necessary. Occupational Safety and Health Administration (USA, OSHA) will decrease hexavalent chromium PEL-TWA from 0.1 mg/m3 to 0.001mg/m3 in workplace air. And Council Labor Affiar in Taiwan (CLA) considers to follow this step.Before decresing the regulation level, we should consider that is analyse method sensitivity enough? It’s the important part of occupational health. The UV/VIS of traditional speciation methods is usually be influenced by the cations in workplace air, and results in over estimation of occupational exposure assessment. The NIOSH METHOD 7703 uses strong anion exchange-solid phase extract cartridges to control cation confounding to get a better result.After the modification of NIOSH METHOD 7703, MDL is 0.0022 μg/mL and adaptable sample concentration range is 0.11~6.67 μg/mL. Just equal to field concentraction grange 0.11~6.95 mg/m3 of sampling for 8 hours at 2 mL/min flow rate. This method can also separate trivalent chromium from CrO42- clearly. In addition, UE/HPLC/ICP-MS equipped with anion exchange column to speciate Cr(III) and Cr(VI) in the μg/L level. H2 and He were used as collision gas in the ICP-MS detection to reduce the interference of multiatomic ions for Cr-52 ion monitoring. The results indicated that the He mode provided better reduction of multiatomic ion interference, where the calibration curve is between 1 to 100 μg/L. Trivalent chromium and hexavalent chromium’s detection limits are 0.21 μg/L and 0.26 μg/L. In filter spike test, we spiked Cr(III) and Cr(VI) on PVDF filters that were soaking in 1 M NaOH at the same time. As each sample contains below 250 ng, both of Cr(III) and Cr(VI) recovery can reach to 88% and 103%. The result indicated PVDF filter is better than PVC and MCE filter.