SummaryEnsemble or signal averaging has been used to increase detection limits in gas chromatography.The sample is injected several times into a gas chromatograph and the chromatominicomputer-based chromatography data system to add together a series of chromatograms resulting from replicate injections of a sample solution.grams generated are summed. The resulting chromatogram is improved signal-to-noise ratio. Use of the technique enables reliable quantitation, the time invested being used to convert an unacceptable signal-to-noise ratio into useful data. A discus-The signal averaging was performed with a utility program techniques to reduce digitization noise by increasing amplifier gain or use of frequency-based filters were not used. provided with a commercial data t;ystem, Other smoothing sion and some applications of the technique are described.
SummaryThe use of 10 %, 1 %, and 0.1 % ammonia in helium as carrier gas was investigated as a means of improving poor chromatographic peak shape often associated with low level determinations of amine compounds using thin film capillary columns. The 1 % ammonia in helium was found suitable for improving the peak shape of sterically unhindered amine compounds, such as urethane and certain aliphatic primary amines, during gas chromatographic analysis on thin film columns. There was a negligible effect on the peak tailing arising on thick film columns. The 0.1 % ammonia in helium was suitable, but not as efficient as the 1 % ammonia in helium, in eliminating the peak tailing associated with low level analysis of amine compounds. The signal-to-noise (NN) ratio improved from < 1 using helium carrier gas to 20-25 (for certain test amine compounds) using 1 % ammonia in carrier gas. The 10 70 ammonia in helium carrier gas had an effect on the chromatographic performance similar to that of the 1 % ammonia in helium, but the baseline level was very high and this mixture was not used in further studies.
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