Economical irregular silica as an effective dispersive solid-phase extraction sorbent for the quantification of calcitriol in soft capsules

• Published in: Journal of pharmaceutical and biomedical analysis 2021-09, Vol.203, p.114227-114227, Article 114227
• Main Authors: Song, Huilin, Wang, Xingchen, Hou, Siyu, Zhang, Yuqi, Luo, Xi, Li, Tengfei, Ji, Shunli
• Format: Article
• Language: English
• Subjects: Calcitriol; Dispersive solid-phase; HPLC-UV; Silica; Soft capsules
• ISSN: 0731-7085; 1873-264X
• DOI: 10.1016/j.jpba.2021.114227

[Display omitted] •Low-cost irregular silica without any chemical modification was used as an effective DSPE sorbent.•The interference of oily matrix on detection could be mostly removed after pretreatment with DSPE.•The whole pretreatment method was simple, time-saving and economical.•The proposed method was proved to be reliable for the content control of calcitriol soft capsules. Calcitriol is an active product of vitamin D produced by the liver and kidney hydroxylase metabolism with strong physiological activity. It is the preferred form of medicine for patients with insufficient bone mineralization due to chronic kidney disease. Calcitriol soft capsule is one of the common preparation forms, the main drug content of which is very low (1.55 μg g−1), and the pharmaceutical excipients interfere greatly, especially the oily matrix medium-chain triglycerides. Therefore, removing the interference of oily matrix is ​​the main challenge in the content determination. At present, the commonly used sample purification method for the determination of calcitriol in soft capsules is liquid-liquid extraction, but it usually consumes a lot of toxic organic solvents and it is costly. The adoption of SPE purification method, on the one hand, requires specific experimental equipment, and on the other hand, the organic solvent used in the experiment may cause the dissolution of SPE column tube materials, which will interfere with the subsequent detection. Herein, in order to achieve a cost-effective and reliable determination of calcitriol soft capsule content, we developed a dispersive solid-phase (DSPE) extraction method that directly uses irregular silica as sorbent, which is followed by high-performance liquid chromatography equipped with a UV detector(HPLC-UV)analysis. Selective retention of calcitriol is achieved by the polar interaction between calcitriol and silica, what’s more, sufficient contact between washing solvent and sorbent can be guaranteed. Therefore, after pretreatment with DSPE, the interference of oily matrix on detection can be mostly removed and then improve the accuracy of the method compared to the SPE method. Under the optimal conditions of DSPE, calcitriol showed a good linear relationship in the range of 0.15−2.99 μg g−1, the R2 was 0.997. Satisfactory recoveries ranging from 101.1%–102.0% for calcitriol were achieved in the oily matrix at the levels of 0.75, 1.50 and 2.24 μg g−1. And the intra-day and inter-day RSD were less than 2.5 % and 3