Toward rapid silica analysis of CPDM samples: Deposition of recovered dust and analysis by FTIR

The ongoing resurgence of severe Coal Workers' Pneumoconiosis in the US has been linked to overexposure to respirable crystalline silica (RCS, which is predominantly present as quartz and regulated as such). Capabilities that enable more frequent RCS monitoring are highly sought. Recent developments include field-based quartz analysis of traditional filter samples-collected on polyvinyl chloride (PVC) filters-using portable Fourier Transform Infrared spectroscopy (FTIR). However, most respirable dust samples in US coal mines are collected with a continuous personal dust monitor (CPDM) that enables real-time tracking of total respirable dust mass concentration. FTIR cannot directly analyze the collected dust sample due to the materials and construction of the sampling substrate. To address this issue, a simple three-step method was envisioned wherein the dust could be recovered into a suspension, redeposited onto a PVC filter using a syringe filter apparatus, and then analyzed by FTIR. The current study was conducted to develop the redeposition and analysis steps. It specifically considers the issues of the PVC filter size and deposition pattern yielded by typical filtration apparatuses and the FTIR scanning locations to establish a model that predicts quartz mass from the spectral data. Of the options tested here, the following combination was found to be optimal: 25-mm PVC filter with dust deposition using an inline syringe filter holder (which yields a "wheel and spoke" pattern), and FTIR analysis at four center-offset locations (90° apart, 8-mm from the center) from which the spectral data were averaged. Under these conditions, the predicted quartz mass on filters with respirable dust deposited from one of two geologic source materials (i.e., representing real coal mine silica sources) was observed to have a standard error of 0.011 mg (11 µg) for samples with an expected quartz mass of less than 0.150 mg (which equated to a total sample mass of less than about 1.5 mg). For samples with higher expected quartz masses, standard error increased, suggesting that dust deposition becomes less uniform with increasing total sample mass.

Lowering reporting limit values for respirable crystalline silica analysis by X-ray diffraction in preparation of the 0.025 mg/m3 occupational exposure limit

Internationally, respirable crystalline silica (RCS) occupational exposure limits (OELs) are being reassessed and, in some jurisdictions, lowered, putting pressure on the capabilities of the analytical techniques used to achieve robust analyses and reliable detection limits. In preparation of a lower OEL, options for lowering the limit of detection (LoD) for RCS analysis have been assessed. Using a Direct-on-Filter X-Ray Diffraction (XRD) analysis under reduced scan speeds in combination with low-noise RCS sampling filters, an LoD of 0.25 µg/filter and a limit of quantification (LoQ) of 0.82 µg/filter can be achieved. Both limits would translate in an LoD of 0.24 µg/m3 and LoQ of 0.78 µg/m3 when sampling respirable dust for 8 h at 2.2 L/min, providing a technical solution to monitor exposures at the proposed OEL of 0.025 mg/m3 (25 µg /m3) and below, with general sampling conditions as typically applied in Australia. This is the first report showing that the OEL of 0.025 mg/m3 (25 µg /m3) is measurable by one of the standardized, direct-on-filter XRD methods.

Oral Bioavailability Enhancement of Poorly Soluble Drug by Amorphous Solid Dispersion Using Sucrose Acetate Isobutyrate

The focus of the present work was to develop amorphous solid dispersion (ASD) formulation of aprepitant (APT) using sucrose acetate isobutyrate (SAIB) excipient, evaluate for physicochemical attributes, stability, and bioavailability, and compared with hydroxypropyl methylcellulose (HPMC) based formulation. Various formulations of APT were prepared by solvent evaporation method and characterized for physiochemical and in-vivo performance attributes such as dissolution, drug phase, stability, and bioavailability. X-ray powder diffraction indicated crystalline drug conversion into amorphous phase. Dissolution varied as a function of drug:SAIB:excipient proportion. The dissolution was more than 80% in the optimized formulation (F10) and comparable to HPMC based formulation (F13). Stability of F10 and F13 formulations stored at 25 C/60% and 40°C/75% RH for three months were comparable. Both ASD formulations (F10 and F13) were bioequivalent as indicated by the pharmacokinetic parameters Cmax and AUC0-∞. Cmax and AUC0-∞ of F10 and F13 formulations were 2.52 ± 0.39, and 2.74 ± 0.32 μg/ml, and 26.59 ± 0.39, and 24.79 ± 6.02 μg/ml.h, respectively. Furthermore, the bioavailability of ASD formulation was more than twofold of the formulation containing crystalline phase of the drug. In conclusion, stability and oral bioavailability of SAIB based ASD formulation is comparable to HPMC-based formulation of poorly soluble drugs.