Calculating Relative Correction Factors for Quantitative Analysis with HILIC-HPLC-ELSD Method: Eight Fructooligosaccharides of Morinda Officinalis as a Case Study

Objective. Because the response of evaporating light scattering detector (ELSD) being in a nonlinear mode, there is no consensus on the method of calculating its relative correction factors (RCF), which limits the application of the quantitative analysis for multi-components by a single marker (QAMS) with LC-ELSD. Methods. Using eight fructooligosaccharides of Morinda officinalis as a case study, the nystose (GF3) as a single standard was adopted to develop a QAMS method to simultaneously determine the other seven fructooligosaccharides with HILIC-HPLC-ELSD method. Six calculation methods of RCF were investigated to select the most reasonable method. The relative error of content between the QAMS and the external standard method (ESM) obtained from 30 batches of samples was used as an indicator to evaluate the six methods. Finally, a chemometrics analysis was performed to find the differential components among MO and its three processing products. Results. It was first reported that only one calculation method was scientific for calculating RCF for the LC-ELSD method. The RCFs of GF3 to the other seven fructooligosaccharides (GF1-GF8) were obtained as 0.86, 0.91, 0.93, 1.05, 1.15, 1.12, and 1.18, respectively. The QAMS of eight fructooligosaccharides of Morinda officinalis was validated with good linearity (R-2 > 0.9998) and accepted the accuracy of 95-105% (RSD < 1.81%) based on nystose. Finally, Morinda officinalis and its three processed products were distinguished and could be differed based on the content of the eight fructooligosaccharides. Conclusion. The scientific calculation method of RCF would be of great significance for developing the QAMS method in Pharmacopoeia when performing the LC-ELSD method.

Automated summary

In this study, a QAMS method was developed using HILIC-HPLC-ELSD to determine the seven fructooligosaccharides of Morinda officinalis. A scientific calculation method for RCF in LC-ELSD method was identified. The QAMS method showed good linearity and accuracy for the determination of fructooligosaccharides. Furthermore, the content of the fructooligosaccharides could differentiate Morinda officinalis and its processed products.