Direct quantitative analysis of respirable cristobalite on filter by infrared spectrophotometry

A direct on-filter method in infrared spectrophotometry was investigated for the quantitative analysis of respirable cristobalite. A polypropylene membrane filter was employed for this analysis, because the membrane filter has high transparency and no interference peak in the spectral range to be used (750-250 cm-1). Linear relation between the sample weight and peak height (absorbance) for three specific peaks at 620, 385 and 300 cm-1 of cristobalite were confirmed over the range from 45 to 1,000 micrograms/cm2 for 620 cm-1 peak and 45-2,380 micrograms/cm2 for 385 and 300 cm-1 peaks. The variation of absorbance with the difference of particle size was smaller in filter sample than in potassium bromide pellet sample. As a conclusion, this direct on-filter method can be used for quantitative analysis of cristobalite in airborne dust in working environment.