結晶型游離二氧化矽紅外光譜分析法之研究

The Determination of Crystalline Silica Using Fourier Transform Infrared Spectroscopy

石英（quartz）是二氧化矽（silica）中最常見的同素異形體且普遍使用於許多工廠中，因此對於長期暴露於二氧化矽粉塵作業的勞工，則為矽肺症（silicosis）的高危險群。有鑑於此，測定工廠作業環境空間中可呼吸性（respirable）二氧化矽粉塵的濃度，為工業衛生上極重要的工作。本研究除引進NIOSH 7602標準法及傅立葉紅外光譜儀（fourier transform infrared spectroscopy, FTIR）偵測粉塵中石英濃度外，並於文獻中第一次以紅外線光譜儀對石英及其同素異形體方矽石（tridymite）和鱗矽石（cristobalite）混存物的定性及定量分析進行討論。其結果發現雖然石英之繞射峰位置和方矽石及鱗矽石有多處重疊的氣象，然而應用特殊電腦程式則可計算混存物中個別成份的濃度，且其相對偏差值均在15%以內。而石英粉塵粒徑大小與紅外吸收強度之關係則為本實驗發現之另一有趣現象；當石英粉塵粒徑大於2μm以上時，石英之吸收峰強度會隨著粒徑之減少而增強。而當石英粒徑小於2μm以下時，其吸收強度卻會隨著粒徑之減小而變弱。但由於旋風粒徑分離器所採得之粉塵粒徑多在8μm以下，在此情況下本實驗結果顯示石英粉塵粒徑大小對吸光度影響有限。

Exposure to silica dust, which takes place in various types of industries and occupations, may cause silicosis, a chronic fibrosis of the lungs. As a result, it is essential for industrial hygiene to develop a method for tailoring and analyzing the quartz content in the respirable dust. An investigatin of crystalline silica using fourier transform infrared spectroscopy (FTIR) was conducted in this research. It had been found that the caharacteristic peaks of quartz, cristobalite, and tridymite partially appeared at different wavenumbers. For example, a doublet around 799 and 779 cm-1, and a singlet near 695 cm-1 were obtained in the spectroscopy of quartz., while mid-strong peaks near 621 and 796 cm-1 were observed in the spectroscopy of cristobalite. A singlet and shoulder near 789, and 567 cm-1, respectively, were also obtained in the spectroscopy of tridymite. However, the coexistence of the main peaks of quartz, tridymite, and cristobalite at the range around 800 cm-1 may cause difficulties in determining separately the concentrations of quartz, tridymite, and cristobalite in mixtures in previous studies. In this experiment, it has been found that this problem can be resolved by using the program QUANT 32. The effect of particle size variation on absorbance intensity was also examined. When particle size of quartz was greater than 2μm, the absorbance intensity increased with decreasing particle size. However, when particle size of quartz was less than 2μm, the absorbance intensity decreased with decreasing particle size. As a result, identifying the particle size distribution in silica dust is essential for determining the concentration of crystalline silica. For field studies, with the use of cyclone elutriator, only particles with aerodynamic diameters less than 8μm were collected, and hence experiments under this condition, showed the effect of particle size on absorbance intensity was small.