relative response factor agilent micro gc

In Riverside, approximately 300 compounds were tracked during two four-week periods in the summer and fall of 2005 (Williams et al., in preparation). In addition, hourly resolution for oxygenated compounds associated with secondary aerosol formation provided insights into atmospheric processes important to their formation. Through factor analysis, six different source profiles were identified including anthropogenic and biogenic components. In Nova Scotia, TAG tracked relative, hourly concentrations of 37 organic compounds over a period of three weeks. 2007), and more recently at an urban site in Riverside, California ( SOAR 2005). The TAG system was initially deployed at a remote site in Nova Scotia ( Williams et al. Like all GC based methods, the TAG instrument is currently restricted to non- to low-polar compounds that elute without derivatization. Thermal desorption of filter based aerosol samples is gaining wider acceptance because of the reduced sample size and handling requirements and has been shown to provide equivalent results to standard liquid extraction techniques for many compound classes (e.g., Hays and Lavrich 2007, and citations therein). Called the Thermal desorption Aerosol Gas chromatograph, or TAG, this automated system has been used to follow the relative, hourly concentrations of dozens to hundreds of ambient organic compounds over periods of several weeks at a time. By coupling traditional gas chromatography–mass spectrometry (GC/MS) with in-situ aerosol collection and thermal desorption, this method aims to bridge this gap between compound specific information obtained from off-line filter analyses and the high-time resolution offered by particle beam mass spectrometry methods. (2006) introduced a new method to provide hourly, in-situ speciation of organic compounds in atmospheric aerosols. However, because of the complexity of organic aerosols, these instruments do not provide the molecular level composition data needed to both identify sources and to better understand the atmospheric formation and transformation pathways for organic particulate matter ( Molina et al. The continuous, detailed characterization provided by these instruments has led to their widespread use in atmospheric research studies.

These offer high time resolution not available from filter methods, as well as size selection and single particle composition. In the last decade, several types of particle beam mass spectrometry instruments such as the AMS ( Jayne et al. Yet filter-based methods are constrained by generally poor time resolution and limited continuity. Even though only a fraction of the total organic mass can be identified at the molecular level, those identified provide important insights regarding the origins of carbonaceous aerosols ( Mazurek 2002). A subset of compound classes, alkanes and PAHs, are used to illustrate the method and provide a means of reducing an 11-day period of data collected in Riverside, CA during the fall of 2005.įor many years, the composition of atmospheric particulate organic matter has been characterized through GC/MS analyses of filter samples. The accuracy of this in-situ calibration approach is assessed through comparisons of TAG analyzed reference filter punches to published NIST assay values. Auxiliary standards extend the range of compounds calibrated through use of relative response factors. Injection response data for the tracking standard is also used to measure instrument precision and limits of quantitation. A routinely injected tracking standard suite of compounds generates a time-dependent correction of detector drift through the course of a measurement study that accounts for the bulk of the change in response of the TAG instrument. Two classes of injection standards, instrument tracking and auxiliary, provide the means to calibrate the instrument in the field for a wide range of compounds. A new collection and thermal desorption cell was developed that incorporates an injection port for in-situ calibrations with liquid standard mixtures.

This paper presents a method for the in-field calibration of this instrument, with the objective of providing quantitative concentrations for a large suite of low polarity organic compounds. The Thermal desorption Aerosol Gas chromatograph (TAG) is a recently developed instrument for the in-situ, hourly measurement of speciated organic compounds in atmospheric aerosols.

Relative response factor agilent micro gc