DIRECT POWDER INTRODUCTION ICP-AES WITH A PHOTODIODE ARRAY SPECTROMETER - A POWDER SAMPLER BASED ON LINEAR MOTION OF THE POWDER TOWARDS AN UPTAKE CAPILLARY

A device for the direct introduction of a powder into a plasma for atomic emission or mass spectrometry is described and the feasibility of quantitative emission measurement of analytes in weighed portions of powder sample is evaluated. A narrow tube containing sample powder is translated smoothly toward the opening of a capillary tube into which a gas is flowing. The powder is entrained uniformly into the flowing gas and thus transported into a concentric chamber wherein the aerosol is further combined with a second carrier gas. The aerosol is transported to the plasma in a gas chromatographic flexible fused silica capillary of 500-mu-m diameter. The device delivers uniform flows of powder at sampler gas flows between 75 and 150 cm3/min. Geological materials were delivered with highest flow uniformity at the maximum linear translation rate of the sample vial. Low sample flow rates will require narrow sample vials. The emission of Fe and Si were not linearly related to flow rate (above 10 mg/min) of geological material NIM-P. The emission of Cu and Co were linearly related to flow rate. The carry-over of NIM-P to the next sample was 1.1%, taken relative to the NIM-P emission, and the carry-over was not detectable in subsequent samples. It was unnecessary to clean sample vials between samples. Quantitative determination of analytes by total integrated emission of weighed samples appears to be feasible. Replicate measurements (without internal standard compensation), of 2 sets of 5 weighed samples of NIM-P, both yielded emission intensity standard deviation below 5%.