JOURNAL OF CHEMICAL METROLOGY, vol.10, no.1, pp.1-11, 2016 (ESCI)
The objective of this work is to apply and compare qNMR and HPLC-UV techniques as useful quality control tools for quantitative measurements of Coenzyme Q(10) in dietary supplement capsules, for which two types of dietary supplement capsules were analysed, containing 100 and 200 mg of Coenzyme Q(10). Both techniques were properly validated in terms of linearity, LOD, LOQ and trueness precision (repeatability and intermediate precision). The uncertainty of the techniques was evaluated according to per EURACHEM / CITAC Guide CG 4 (3th edition), Quantifying Uncertainty in Analytical Measurement. The HPLC-UV and qNMR methods were linear in the ranges of 10.0 - 1000.0 mu g mL(-1) and 2.2 - 30.3 mg mL(-1) for Coenzyme Q(10), respectively, and demonstrated very good linearity performance with regression coefficients (R2) above >= 0.99. Using qNMR method, LOD and LOQ were found to be 0.48 and 1.47 mg per 0.7 ml, respectively. The LOD and LOQ values of HPLC-UV were found to be 0.025 and 0.083 mu g mL(-1), respectively. Intra and inter batch accuracies for HPLC-UV, as a deviation between nominal and measured values, ranged from -0.3 to 7.1% and from -0.9 to 6.3%, respectively. The accuracy for qNMR was assessed using one concentration level with 6 different samples. Comparison of the measurements of the capsul samples indicated that the both methods were appropriate for the determination of Coenzyme Q(10) in pharmaceutical quality control (QC), although the qNMR as a primary measurement method was found to be more convenient especially in the method development phase. The advantages of qNMR were its environmental friendliness due to the low solvent consumption, selectivity and short sample preparation time. By using the qNMR technique there is no need to concern in terms of carry over problems.