Assay of Ursodeoxycholic Acid and Related Impurities in Pharmaceutical Preparations by HPLC with Evaporative Light Scattering Detector

Development of HPLC-CAD method for simultaneous quantification of nine related substances in ursodeoxycholic acid and identification of two unknown impurities by HPLC-Q-TOF-MS

Ursodeoxycholic acid has gained increasing attention due to its recent discovery of the preventive effect on SARS-CoV-2 infection. Ursodeoxycholic acid has been included in various pharmacopoeias as an old drug, and the latest European Pharmacopoeia lists nine potential related substances (impurities A~I). However, existing methods in pharmacopoeias and literature can only quantify up to five of these impurities simultaneously, and the sensitivity is inadequate, as the impurities are isomers or cholic acid analogues lacking chromophores. Herein, a novel gradient RP-HPLC method coupled to charged aerosol detection (CAD) was developed and validated for the simultaneous separation and quantification of the nine impurities in ursodeoxycholic acid. The method proved sensitive and allowed the quantification of the impurities as low as 0.02%. Relative correction factors of the nine impurities were all within the range of 0.8~1.2 in the gradient mode by optimizing chromatographic conditions and CAD parameters. In addition, this RP-HPLC method is fully compatible with LC-MS due to the volatile additives and high percentage of the organic phase, which can be directly used for the identification of impurities. The newly developed HPLC-CAD method was successfully applied to commercial bulk drug samples, and two unknown impurities were identified by HPLC-Q-TOF-MS. The effect of CAD parameters on the linearity and correction factors was also discussed in this study. Overall, the established HPLC-CAD method can improve the methods in current pharmacopoeias and literature and contributes to understanding the impurity profile for process improvement.

Analysis of mannitol in pharmaceutical formulations using hydrophilic interaction liquid chromatography with evaporative light-scattering detection

This study demonstrates the use of hydrophilic interaction liquid chromatography (HILIC) for the separation of both active and inactive ingredients in pharmaceuticals from a single injection. Excipients commonly used in parenteral formulations were separated using a gradient method employing increasing aqueous composition. An evaporative light-scattering detector (ELSD) provided direct detection of inactive excipients and inorganic salts lacking UV chromophores. Analyses of Gemzar parenteral formulations using optimized isocratic HILIC-ELSD method conditions were performed based on retention time screening from the gradient assay. All of the components were efficiently separated using a TSK-Gel Amide 80 column including gemcitabine, mannitol, and sodium cation demonstrating the qualitative capability of the technique. The method was thoroughly validated for mannitol content to access the quantitative potential of the technique. Validation parameters included linearity, accuracy, specificity, solution stability, repeatability, and intermediate precision. Overall, the method described in this report proved to be very robust and represents a novel technique to conveniently separate and detect the active and inactive components in pharmaceuticals both quickly and accurately.

Evaluation of a monolithic silica column operated in the hydrophilic interaction chromatography mode with evaporative light scattering detection for the separation and detection of counter-ions

In this work a monolithic silica column operated in the hydrophilic interaction chromatography (HILIC) mode in conjunction with an evaporative light scattering detector (ELSD) was investigated. Lithium, sodium and potassium were used as the test counter-ions for this evaluation. Chromatographic properties of this column operated in the HILIC mode were determined by varying key mobile phase parameters, such as pH, flow rate, buffer strength, acid and organic modifier. As organic content was increased from 60 to 90% acetonitrile, retention time increased on average by a factor of seven for the test cations listed above. Buffer concentration and pH were also observed to have an effect, although not as significant as the HILIC effect that was observed by changing organic content. Flow rates up to 5 mL/min were utilized to perform counter-ion separations in less than 3 min. After examining the changes in retention, resolution, and peak shape an optimized method was established and then further evaluated for linearity, reproducibility, and limit of detection (LOD) for sodium. Linearity was acceptable with an R2 value of 0.999 across the working-standard range and a LOD of 0.1 microg/mL was calculated. The reproducibility on the counter-ion determination from pharmaceutical sodium salts was 1.6% R.S.D. on average, and the accuracy of the counter-ion prediction was approximately 3% from theory when salt content was corrected for potency.

An overview of the recent trends in development of HPLC methods for determination of impurities in drugs

An extensive survey of the literature published in various analytical and pharmaceutical chemistry related journals has been conducted and the high-performance liquid chromatography (HPLC) methods which were developed and used for determination of process-related impurities in drugs have been reviewed. This review covers the time period from 1995 to 2001 during which around 450 analytical methods including all types of chromatographic and hyphenated techniques were reported. HPLC with UV detection was found to be the technique of choice for many workers and more than 200 methods were developed using LC-UV alone. A critical analysis of the reported data has been carried out and the present state-of-art of HPLC for determination of impurities of analgesic, antibiotic, anti-viral, anti-hypertensive, anti-depressant, gastro-intestinal and anti-neoplastic agents has been discussed.

Determination of ursodeoxycholic acid in pharmaceutical preparations by capillary electrophoresis with indirect UV detection

A simple and rapid capillary electrophoretic method, with indirect UV detection, for the quantification of ursodeoxycholic acid (UDCA) in pharmaceutical preparations was developed in this study. Sodium p-hydroxy benzoate was used as background electrolyte (BGE) (5 mM, pH 8.0) and visualization agent. Separation was carried out on a fused-silica capillary (50 microm x 72 cm) at a potential of 25 kV under ambient temperature and detected at 250 nm. Glycocholic acid was used as internal standard for quantification. Both run-to-run repeatability and day-to-day reproducibility of migration time were below 0.1% relative standard deviation (R.S.D.). Repeatability and reproducibility of relative peak height were 3.3 and 3.8% R.S.D., respectively. Accuracy was tested by spiking two pharmaceutical tablets with standards and the recoveries were 101.9+/-9.87 and 99.6+/-9.60% (n=3), respectively. Linearity of relative peak height was tested in the range 20-100 microg/ml. Limit of detection (LOD) was 3 microg/ml. The method could be used to assay UDCA raw materials and formulation products.

Separation and quantitation of bile acids using an isocratic solvent system for high performance liquid chromatography coupled to an evaporative light scattering detector

We developed a quantitative method for the analysis of bile acids using a high performance liquid chromatograph coupled to an evaporative light scattering detector. An isocratic solvent system was used to resolve in a single run conjugated and unconjugated bile acid species relevant in human and rodent physiology. The detection of various bile acids was linear over a range of 0.08 to 10 nmol of injected molecules. The developed system is a convenient and cost-effective method for the routine analysis of a wide variety of bile acids.