Determination of the Mass Extractable in Organic Solvents by Evaporative Light-Scattering Detection

Abstract

An alternative to the gravimetric method for the determination of the mass extracted from particles has been developed based on an evaporative light-scattering detector (ELSD), which requires a much smaller portion of the sample. A liquid chromatograph with an ELSD and without a separating column was used for these studies. Individual standard solutions of aliphatic hydrocarbons with 10 to 26 carbon atoms, polycyclic aromatic hydrocarbons with 2 to 5 rings, and two saturated cyclic hydrocarbons were analyzed by ELSD. Compounds with boiling points over 300°C had very similar responses on the ELSD. However, although the ELSD is reported to respond to mass, regardless of chemical composition, less response was found for more volatile compounds. In addition, gravimetric and ELSD analyses were performed on standard solutions of four different complex mixtures important to occupational and environmental studies: a soluble machining fluid, dichloromethane (DCM) extractions from diesel exhaust particles, DCM extractions from kerosene heater particles, and DCM extractions of semivolatile emissions from kerosene heaters, as collected on XAD resin. The soluble machining fluid and extracts of particles from diesel exhaust and kerosene heater emissions were generally well quantified by the ELSD, which required the extract from less than a milligram of particulate mass. The ELSD was found to be quite sensitive and quantitated samples with less than 20 μg of extracted mass injected. The gravimetric and ELSD determinations of mass were not in good agreement for the kerosene emissions of semivolatile compounds, as collected on XAD. ELSD determination of mass should be useful in measuring the mass that has been extracted by organic solvents from particles when small masses are collected, such as in air pollution studies or personal samples in occupational settings. The technique is not recommended for more volatile compounds.