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.
The accuracy of the AOAC official first action ion-pair liquid chromatographic assay for dalapon grasskiller products was studied by comparison with an independent ion-exchange liquid chromatographic method. No statistically significant difference in assay results was seen between the latter method and the AOAC official method for the assay of sodium salt, mixed sodium/magnesium salt, or the free acid forms of dalapon.
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