On-line analytical instrumentation developed at the US Department of Energy's Morgantown Energy Technology Center (DOE/METC) to monitor particle and alkali loading was successfully used on the process stream of a coal gasifier to measure contaminant levels before and after combustion of the coal gas in a turbine-simulator combustor at the General Electric Research Laboratories in Schenectady, New York. A two-color laser transmissometer was designed and built to simultaneously measure particle median size and number density in situ in a highly loaded gas process stream. Four of the instruments successfully monitored particle number density at different locations on the coal gasifier-combustor system. The particle loading measurements ranged from 150 ppM to greater than 1000 ppM. Temporal variations observed in the particle loading data correlated with physical events perturbing the gasifier system. A fiber-optic flame atomic emission spectrometer was designed and built to measure sodium and potassium concentrations in gas samples extracted from the process stream. Two of the instruments and an earlier system built at Ames Laboratory at Iowa State University successfully measured alkali levels before and after the combustor using an extractive probe. The alkali monitors found contaminant levels in the fuel gas lower than values determined from extractive filter samples, the average value being 48 ppB total alkali. The ratio of sodium to potassium was constant across the combustor. 8 refs., 12 figs., 3 tabs.