THE USE OF VACUUM ULTRAVIOLET RADIATION IN THE ANALYSIS OF ORGANIC SPECIES AND RELATED INVESTIGATIONS (INDUCTIVELY-COUPLED PLASMA OPTICAL EMISSION SPECTROMETRY).

Abstract

Inductively-Coupled Plasma Optical Emission Spectrometry (ICP-OES) is evaluated as a method for the selective determination of several non-metals which emit light in the Vacuum Ultraviolet (VUV) region of the spectrum. In this study, emphasis is placed on those elements which are totally unobservable with standard techniques or have very weak lines in the UV-VIS region of the spectrum. The sensitivity and accuracy of the apparatus and methods devised allows the determination of empirical formulas of gas chromatographic effluents. The results of this study indicate that the background emission of the ICP in the VUV is low level and nearly constant over the entire spectral region investigated (125 - 185 nm.). Promising analytical lines for oxygen, nitrogen, chlorine, bromine, and carbon are also observed in this region. A progression of four experimental configurations were constructed, employing a purged optical path and a unique coolant tube design. The last of these configurations has the capability of spatial resolution of individual portions of the discharge so that emission maps and profiles could be constructed. The results of the maps generated indicate that the region of highest emission intensity is always centered in the discharge. However, the vertical position of this region is found to be dependent upon r.f. power and argon flow rates. Detection limits in the low nanogram region are observed for each non-metal. The dynamic range for each element is in excess of 10⁴ and the selectivity ratio versus carbon is above 100 in each case. A method was developed for determining the elemental composition of the effluents of a GC. Using internal standards, the method is independent of the weight of each component eluted thus sampling errors are eliminated. The average relative errors in multielement analysis are 0.89%, 0.75%, 2.1%, 0.55%, and 0.64% for the percent carbon, oxygen, nitrogen, chlorine, and bromine, respectively.