Powders are used as received from chemical sources or ground to a finer powder to press into solid pellets. About 10 mg of sample is mixed with about 100 mg of dry spectrophotometric grade polyethylene powder and pressed in a 13 mm die to obtain a 2 mm thick pellet. The pressure used is approximately 200 PSI. Data was collected for sample pellets and polyethylene blanks of the same mass and transmission obtained by ratioing these acquired raw spectra in the usual manner.
The instrument used to collect the data is a modified Nicolet Magna 550 incorporating a silicon-coated mylar beamsplitter and DTGS detector fitted with a polyethylene window. The standard filament source is used and the instrument purged with dried air (water and CO2 removed) for all spectral acquisitions.