Fat-soluble vitamins play a pivotal role in the progression of atherosclerosis and the development of cardiovascular disease. Therefore, plasma monitoring of their concentrations may be useful in the diagnosis of these disorders as well as in the process of treatment. The study aimed to develop and validate an HPLC-MS/MS method for determination of retinol, α-tocopherol, 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3 in plasma of patients with cardiovascular disease. The analytes were separated on an HPLC Kinetex F5 column via gradient elution with water and methanol, both containing 0.1% (v/v) formic acid. Detection of the analytes was performed on a triple-quadrupole MS with multiple reaction monitoring via electrospray ionization. The analytes were isolated from plasma samples with liquid-liquid extraction using hexane. Linearity of the analyte calibration curves was confirmed in the ranges 0.02-2 μg/mL for retinol, 0.5-20 μg/mL for α-tocopherol, 5-100 ng/mL for 25-hydroxyvitamin D2 and 2-100 ng/mL for 25-hydroxyvitamin D3. Intra- and inter-assay precision and accuracy of the method were satisfactory. Short- and long-term stabilities of the analytes were determined. The HPLC-MS/MS method was applied for the determination of the above fat-soluble vitamin concentrations in patient plasma as potential markers of the cardiovascular disease progression.

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Background: Atorvastatin (AT) belongs to cholesterol-lowering agents, commonly used in patients with an increased risk of cardiovascular disease. The drug, as well as its hydroxyl metabolites, exhibit pharmacological activity, and their plasma levels may be helpful in the assessment of the therapeutic effectiveness. Objective: Development and validation of a fast and reproducible RP-HPLC method with UV detection for the simultaneous determination of atorvastatin and its active metabolites, para-hydroxy-atorvastatin (p-OH-AT) and ortho-hydroxy-atorvastatin (o-OH-AT) in human plasma. Methods: Optimal conditions of chromatographic separation of the analytes, as well as rosuvastatin, chosen as an internal standard, were studied. The absorbance of the compounds was measured at λ=248 nm. Validation of the method was performed. The usefulness of the method was confirmed for determination of the analytes in plasma of patients treated with the drug. Results: Total peak separation was achieved at LiChrospher 100 RP-18 column with a mobile phase composed of methanol and water (1:1,v:v) and a flow rate of 1.2 ml/min. The method was linear in the ranges of 0.025 - 1.0 μg/ml for AT, o-OH-AT and p-OH-AT. Intra- and inter-assay precision expressed as relative standard deviation was ≤13% for AT, ≤12% for p-OH-AT and ≤11% for o-OH-AT. Intraand inter-day accuracy of the method, expressed as a relative error, was ≤15%. Conclusion: The elaborated HPLC method is specific, repeatable, reproducible, adequately accurate and precise and fulfills the validation requirements for the bioanalytical method. The method was successfully applied for analysis of atorvastatin and its o-hydroxy metabolite in plasma of patients treated with the drug.