Compounds which are only semi-volatile or which are heat sensitive are best analyzed by High Performance Liquid Chromatography (HPLC).
HPLC is similar to GC but uses a liquid carrier instead of an inert gas. While GC analysis often operates at high temperatures, HPLC is done at room temperature, but at high pressures. The detectors used for HPLC are the ultraviolet detector and the fluorescent detector. Therefore, in order to be analyzed by HPLC, a compound must be fluorescent or able to absorb UV light. Some compounds can be derivatized to accomplish this. An example of this type of analysis is isocyanates.
A typical HPLC analysis is for isocyanates. Isocyanates are collected open-faced on the orange filter. We have two different filters used to collect isocyanates. One is for Methylene Diphenyl Diisocyanate (MDI). The second is for other isocyanates. If you need to collect MDI and other isocyanates together, call the lab for instructions.
In the lab the filters are extracted with acetronitrile and DMSO and an aliquot is injected onto a C-18 reverse phase column and eluted off with an ammonium acetate buffer and acetronitrile.
The lab is able to perform a scan for many isocyanates on each sample.
If sampling for isocyanates in spray painting or other operations where aerosol isocyanates are present, field desorbtion is required. Limit the sampling to fifteen (15) minutes and immediately transfer the filter to the vial of desorbtion solution.
These are a pyridyl piperazine coated fiberglass filters. The isocyanates react with the pyridyl piperazine to form stable urea derivatives.
Other HPLC Analyses
Other substanced analyzed by HPLC are phenols, polyaromatic hydrocarbons (PAHs), aldehydes, various pesticides and many others.
Because HPLC analysis is very specific, it is important that you specify which compounds you may expect to find in a sample.