Simultaneous Quantitative Analysis of Six Cations in Three Biodiesel and Their Feedstock Oils by an Ion-Exchange Chromatography System without Chemical Suppression

This work aimed at detecting and evaluating the contents of six cations {K+, Na+, Ca2+, Mg2+, NH4(+), and [HN(CH2CH2OH)(3)](+)} in waste cooking oil biodieset Jatropha biodiesel, rubber-seed-oil-based biodiesel, and their feedstock oils using ion chromatography without chemical suppression conductivity detection. The analytical system cuts down costs because it is not necessary to use an expensive suppressor module. The mixed solution containing 1.7 mmol L-1 nitric acid, 0.7 mmol L-1 2,6-pyridinedicarbox-ylic acid, and 0.05 mmol L-1 18-crown-6 was used as the eluent. The proposed method uses 1.7 mmol L-1 aqueous nitric add solution and extraction- and heating-assisted separation funnels. The limits of detection (LODs, in mg L-1) were found to be as follows: Na+, 0.001; NH4+, 0.001; K+, 0.002; [HN(CH2CH2OH)(3)](+), 0:005; Ca2+, 0.001; and Mg-2+,Mg- 0.001. The results showed that r values for the correlation coefficients of linear regression equations were greater than 0:995, while:the baseline noise was under 0.005 mu S for all of the analytes. Relative standard deviation (RSD) of the retention time Was observed to be lying within the range of 0.083-0.388%, and that of the peak area was less than or equal to about 3% {except for [HN(CH2CH2OH)(3)](+)}. The observed amounts in waste cooking oil biodiesel, Jatropha biodiesel, and rubber-seect-oil-based biodiesel (in mg kg(-1)) were found to be as follows: Na+, 2.187, 2.798, and 4.320; NH4+, 1.031, 0.792, and 0.667; K+, 0.710, 1.081, and 18.814; Ca2+, 1.962, 5.047, and 1.398; and Mg2+ : 0.399, 0.915, and 更多