Analytical Techniques and Method Validation for the Measurement of Selected Semivolatile and Nonvolatile Organofluorochemicals in Air

Abstract

The widespread use of semi- and nonvolatile organofluorochemicals in industrial facilities, concern about their persistence, and relatively recent advancements in liquid chromatography/mass spectrometry (LC/MS) technology have led to the development of new analytical methods to assess potential worker exposure to airborne organofluorochemicals. Techniques were evaluated for the determination of 19 organofluorochemicals and for total fluorine in ambient air samples. Due to the potential biphasic nature of most of these fluorochemicals when airborne, Occupational Safety and Health Administration (OSHA) versatile sampler (OVS) tubes were used to simultaneously trap fluorochemical particulates and vapors from workplace air. Analytical methods were developed for OVS air samples to quantitatively analyze for total fluorine using oxygen bomb combustion/ion selective electrode and for 17 organofluorochemicals using LC/MS and gas chromatography/mass spectrometry (GC/MS). The experimental design for this validation was based on the National Institute of Occupational Safety and Health (NIOSH) Guidelines for Air Sampling and Analytical Method Development and Evaluation, with some revisions of the experimental design. The study design incorporated experiments to determine analytical recovery and stability, sampler capacity, the effect of some environmental parameters on recoveries, storage stability, limits of detection, precision, and accuracy. Fluorochemical mixtures were spiked onto each OVS tube over a range of 0.06–6 μg for each of 12 compounds analyzed by LC/MS and 0.3–30 μg for 5 compounds analyzed by GC/MS. These ranges allowed reliable quantitation at 0.001–0.1 mg/m³ in general for LC/MS analytes and 0.005–0.5 mg/m³ for GC/MS analytes when 60 L of air are sampled. The organofluorochemical exposure guideline (EG) is currently 0.1 mg/m³ for many analytes, with one exception being ammonium perfluorooctanoate (EG is 0.01 mg/m³). Total fluorine results may be used to determine if the individual compounds quantified provide a suitable mass balance of total airborne organofluorochemicals based on known fluorine content. Improvements in precision and/or recovery as well as some additional testing would be needed to meet all NIOSH validation criteria. This study provided valuable information about the accuracy of this method for organofluorochemical exposure assessment.

Keywords:

• gas chromatography/mass spectrometry
• liquid chromatography/mass spectrometry
• method validation
• organofluorochemicals
• OVS tubes
• total fluorine

Notes

^A Analyte poorly retained on OVS tube. This analytical method is not appropriate for quantitative analysis.

^B Analyte not retained by sampler. Data not reported.

^A Also known as PFOA.

^A n = 6; 480 L airflow at 1 L/min, analytes were spiked as acetone solutions onto particulate filters of the OVS tube.

^B Spiked with 0.6, 6, and 60 μg.

^A 480 L airflow at 1 L/min, 120 μg for total fluorine, 12 μg for target analytes; analytes were spiked as acetone solutions onto particulate filters of the OVS tube.

^B First Section includes particulate filter plus first XAD-4 and PUF sections. Backup Section includes second XAD-4 and PUF sections.

^A 480 L airflow at 1 L/min, 300 μg for total fluorine, 3 μg for target analytes; analytes were spiked as acetone solutions onto particulate filters of the OVS tube.

^A LOD and LOQ calculations are based on a 60-L nominal sample volume.

^B LOQ calculation is LOD times 3.33.

^C Analyte poorly retained on OVS tube. This analytical method is not appropriate for quantitative analysis.