Abstract |
An accurate procedure based on micro-gravimetry has been used for the preparation of volatile, hazardous organic chemicals in a nitrogen matrix in pressurized gas cylinders at analyte concentrations ranging from 10 ppb to 10 ppm, by mole. In this technique, the organics of interest are individually weighed into separate glass capillary tubes using a micro-analytical balance. The tubes are sealed, and subsequently broken in a fixed line connected to an evacuated cylinder. A known weight of pre-analyzed matrix gas (nitrogen) is then used to pressurize the cylinder, and the concentrations of the organics are calculated on a molar basis relative to the number of moles of the matrix gas. A number of these gravimetric primary mixtures have been prepared and analytically intercompared using gas chromatography (GC) with flame-ionization detection (FID). Excellent agreement has been found between analyte concentration values prepared gravimetrically and concentration values determined by analysis. |