A capillary electrophoresis–tandem mass spectrometry method with a multisegment injection and an in-capillary field-enhanced sample stacking for determination of therapeutic peptide triptorelin in pharmaceutical and biological matrices was developed. The CE separation conditions were optimized in order to obtain maximal separation efficiency, analytical signal intensity and stability, and minimal adsorption of the analyzed peptide onto the capillary wall (1 M formic acid – HFo, pH 1.88). The implementation of the field-enhanced sample injection into CE improved the value of limit of detection 50 times while the multisegment injection increased the sample throughput three times in comparison to a conventional CE approach. The proposed method was characterized by favorable performance parameters, such as linearity (r2 ≥ 0.99), limit of detection (5 ng mL−1 in water matrix, 25 ng mL−1 in plasma matrix), precision (relative standard deviation, 1.5–9.4% for intraday and 2.3–11.9% for interday reproducibility), or accuracy (relative errors in the range of 80–109%). The FDA-validated method was successfully applied to the analysis of triptorelin in the commercial drug Diphereline® 0.1 mg (powder for injection) and in spiked human plasma samples. Favorable performance parameters along with proven application potentialities indicate the usefulness of the proposed method for its routine use in drug quality control laboratories and for clinical analysis, such as determination of triptorelin levels in plasma (for pharmacokinetic study).
A simple analytical approach based on capillary zone electrophoresis with ultraviolet detection and repeated sample injection strategy (applied in a hydrodynamically closed separation system for the first time) was developed for the determination of ibuprofen (IBU) in commercially available pharmaceutical preparations. The proposed method was characterized by significantly increased sample throughput and favorable validation parameters, highly demanded in routine quality control laboratories. The limit of detection was predicted at the concentration level of 0.31 µg/mL. Intra-day precision expressed as the relative standard deviation of IBU concentration ranged from 1.9 to 5.6%, and corresponding intra-day accuracy expressed as the relative error was in the interval of 87.1–106.5%. Inter-day precision was in the range of 2.6–15.0%, and inter-day accuracy was 94.9–102.7%. The developed method was able to quantify IBU in complex pharmaceutical matrices represented by commercially available tablets and oral suspension. The determined contents of IBU in the tested dosage forms were in good agreement with the manufacturer’s declaration. The analytical performance of the developed method was evaluated according to the innovative RGB Additive Color Model strategy. It was demonstrated that the proposed method is characterized by very good analytical performance parameters, safety and eco-friendliness, and practical effectiveness.
The effects of organic modifiers—alcohols (methanol, isopropanol), acetonitrile, and tetrahydrofuran—and β-cyclodextrins in capillary zone electrophoresis were investigated using a test mixture containing five biogenic amines important from the human health point of view—serotonin, dopamine, adrenaline, noradrenaline, and tyramine—and two B vitamins—thiamine and pyridoxine. The simultaneous addition of tetrahydrofuran and isopropanol was found to improve the resolution of determined analytes and enable effective separation of analytes with very similar electromigration characteristics migrating as one peak (dopamine and serotonin). The developed and optimised separation method based on capillary zone electrophoresis and ultraviolet detection was capable to achieve detection limits at the concentration level in the range of 0.15 to 1.25 μg/mL−1. The developed method was also characterised by other favourable validation parameters, such as linearity (r
2 > 0.99), accuracy (82.9–117.8% for the intraday measurements, and 87.6–119.2% for the interday measurements), and precision (intraday relative standard deviation in the range of 0.4–15.5%, interday relative standard deviation in the range of 0.9–18.3%). The method was finally applied to investigate the stability of the analytes in model water matrix samples under various storage conditions.
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