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Archive for July, 2003

Diffusive Sampling for Ambient Air and Other Low Level Applications

Saturday, July 26th, 2003

Diffusive Sampling for Ambient Air and Other Low Level ApplicationsDiffusive sampling has been a popular approach for the evaluation of workplace exposures to airborne contaminants, such as volatile organic compounds (VOCs) for some time. Typically, these “badge-type” samplers (e.g., 3M, SKC) have been used to evaluate exposures in the high part per billion (ppb) to part per million (ppm) range over an 8-hour period. A popular option, these samplers are easy to use, small in size and don’t require a sampling pump.

This approach involves the passive collection of an analyte on a solid sorbent via adsorption or chemical reaction. The sampling rate (e.g., diffusive uptake rate) is a function of the diffusive coefficient, which is compound and sorbent specific, and the geometry of the sampler used. Other factors that affect performance include temperature, pressure, humidity, air velocity and transient changes in contaminant concentrations. Samples are chemically desorbed and analyzed by gas chromatography with flame ionization detection (GC/FID) or by other appropriate instrumentation.

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Ultra-trace Metals Determinations using Reductive Precipitation and ICP-MS

Saturday, July 26th, 2003

Ultra-trace-Metals-Determinations-using-Reductive-Precipitation-and-ICP-MSColumbia Analytical Services’ Kelso laboratory has continued the development of analytical techniques for pre-concentration and chemical separation of trace metals in saline aqueous samples using reductive precipitation followed by inductively coupled plasma-mass spectroscopy (ICP-MS). This technique replaces conventional techniques for the analysis of trace metals in complex aqueous matrices such as sea water where matrix problems prevent the ability to achieve desired low levels of detection. Detection limits for various metals of interest using these techniques are displayed in the table to the right. Details of this procedure were presented at the recent National Environmental Monitoring Conference (NEMC) held July 21-24 in Arlington, Virginia. The full abstract follows.

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