COMPARISON OF THE EVAPORATIVE LIGHT-SCATTERING DETECTOR (ELSD) AND REFRACTIVE-INDEX DETECTOR (RID) IN LIPID ANALYSIS

The properties of an evaporative light scattering detector (ELSD) and a refractive index detector (RID) in isocratic HPLC analysis of lipids are compared. The effect of molecular structure, especially the unsat uration level, on the detector response is studied using eight differe nt lipid standards. Linearity and sensitivity are compared. Quantitati on of an unknown sample is also performed. The sensitivity of the ELSD was slightly better than that of the RID, the detector limits of trio lein being 30 ng/injection and 50 ng/injection, respectively. The line arity of the ELSD was considered only approximate compared with that o f the RID the response factors of the calibration curves being 0.9554 and 0.9999, respectively. The effect of the molecular structure on the detector response was higher with the RID than with the ELSD. The rel ative standard deviation (SD%) of responses was 23% for the RID and 12 % for the ELSD. The unsaturation level had a greater effect on the det ector response of the RID than on that of the ELSD. This study indicat es that a standard deviation (SD) of at least 13% is to be expected wi th the ELSD and an even higher SD with the RI detector when quantitati ng heterogeneous mixtures or unknown compounds.