Weakley Andrew Todd, Miller Arthur L, Griffiths Peter R, Bayman Sean J
Department of Chemical and Materials Engineering, University of Idaho, PO Box 441021, Moscow, ID, 83844-1021, USA,
Anal Bioanal Chem. 2014 Jul;406(19):4715-24. doi: 10.1007/s00216-014-7856-y. Epub 2014 May 16.
The feasibility of measuring airborne crystalline silica (α-quartz) in noncoal mine dusts using a direct-on-filter method of analysis is demonstrated. Respirable α-quartz was quantified by applying a partial least squares (PLS) regression to the infrared transmission spectra of mine-dust samples deposited on porous polymeric filters. This direct-on-filter method deviates from the current regulatory determination of respirable α-quartz by refraining from ashing the sampling filter and redepositing the analyte prior to quantification using either infrared spectrometry for coal mines or x-ray diffraction (XRD) from noncoal mines. Since XRD is not field portable, this study evaluated the efficacy of Fourier transform infrared spectrometry for silica determination in noncoal mine dusts. PLS regressions were performed using select regions of the spectra from nonashed samples with important wavenumbers selected using a novel modification to the Monte Carlo unimportant variable elimination procedure. Wavenumber selection helped to improve PLS prediction, reduce the number of required PLS factors, and identify additional silica bands distinct from those currently used in regulatory enforcement. PLS regression appeared robust against the influence of residual filter and extraneous mineral absorptions while outperforming ordinary least squares calibration. These results support the quantification of respirable silica in noncoal mines using field-portable infrared spectrometers.
本文证明了采用直接滤膜分析法测定非煤矿粉尘中空气传播的结晶二氧化硅（α-石英）的可行性。通过对沉积在多孔聚合物滤膜上的矿尘样品的红外透射光谱应用偏最小二乘法（PLS）回归，对可吸入α-石英进行定量分析。这种直接滤膜法与目前对可吸入α-石英的监管测定方法不同，它无需对采样滤膜进行灰化处理，也无需在使用煤矿用红外光谱法或非煤矿用X射线衍射（XRD）法定量分析之前重新沉积分析物。由于XRD仪器不便于现场携带，本研究评估了傅里叶变换红外光谱法在测定非煤矿粉尘中二氧化硅方面的有效性。使用经过改进的蒙特卡洛非重要变量消除程序选择重要波数，对未灰化样品光谱的选定区域进行PLS回归分析。波数选择有助于提高PLS预测能力，减少所需PLS因子的数量，并识别出与当前监管执法中使用的波段不同的其他二氧化硅波段。PLS回归在抵抗残留滤膜和外来矿物吸收的影响方面表现稳健，同时优于普通最小二乘法校准。这些结果支持使用现场便携式红外光谱仪对非煤矿中的可吸入二氧化硅进行定量分析。
