Barbara Żuromska-Witek

A universal HPLC method with diode array detection was developed for the separation and determination of the lactone and acid forms of monacolin K in the presence of other active ingredients (vitamins B₁, B₆, B₁₂, and folic acid) found in selected dietary supplements. The method also enables the quantitative determination of citrinin in monacolin K. Chromatographic separation was performed on an ACE 5 C18-PFP column (250 × 4.6 mm) thermostated at 25 °C. The mobile phase consisted of 0.005 M phosphate buffer (pH 2.60) and acetonitrile under linear gradient elution conditions. Detection was carried out spectrophotometrically at 230 nm for monacolin K and 325 nm for citrinin. The total run time was 28 min. The method was validated and met the acceptance criteria for specificity, linearity, sensitivity, accuracy, and precision. Linearity was achieved over a broad concentration range: 12.48–37.44 μg·mL⁻¹ for MK and 3.48–5.22 μg·mL⁻¹ for CTN. The method is sufficiently sensitive, with LOD and LOQ values of 0.91–2.85 μg·mL⁻¹ and 2.18–3.48 μg·mL⁻¹ for MK and CTN, respectively. Good precision (RSD < 0.70%) and intermediate precision (RSD < 1.33%) were observed. The accuracy of the method, expressed as percentage recovery at three concentration levels, ranged from 98.73% to 100.64%. The analysis revealed that the monacolin K content in randomly selected dietary supplements did not comply with the manufacturer’s declaration in any case.

A new universal HPLC-DAD method has been developed for the separation and simultaneous determination of thirteen active pharmaceutical ingredients (APIs): ramipril, lisinopril, enalapril; atenolol, metoprolol; losartan, candesartan; rosuvastatin, atorvastatin, simvastatin; amlodipine; hydrochlorothiazide, acetylsalicylic acid in polypills used in the treatment of hypertension. The chromatographic analysis of the APIs was performed on an ACE-5 C18-PFP column (250 mm × 4.6 mm, 5 μm) with 0.01 M phosphate buffer (pH = 2.50) and acetonitrile in gradient elution as the mobile phase at a flow rate 1.0 mL min⁻¹. UV detection was performed at 230 nm. The analysis time was 35 min. The elaborated method meets the acceptance criteria for specificity, linearity, sensitivity, accuracy, and precision for all examined substances. The linearity range was observed in a wide concentration range, whereas the determination coefficients (R²) for the linear model were greater than 0.990. The sensitivity of the method was good with the LOD and LOQ values ranged from 0.0009 to 0.0923 mg mL⁻¹ and from 0.0027 to 0.2794 mg mL⁻¹, respectively. The proposed method showed good precision with RSD less than 1.91% and the accuracy expressed as percent recovery was from 95.20% to 104.62%. The proposed HPLC-DAD method was successfully applied to determine APIs in prepared model mixtures corresponding to the commercially available polypill tablets. The obtained results of the measured contents were with good accuracy (95.84–103.92%) and high precision (RSD < 0.95%) indicating the applicability of the proposed method for the simultaneous determination of the polypill components. Therefore, the method can be an effective tool in the quality control of polypills.

The new RP-HPLC-DAD method for the determination of ciprofloxacin and pefloxacin, next to their degradation products after the oxidation reaction with 4,4′-azobis(4-cyanopentanoic acid) (ACVA) was developed. The method was validated according to the guidelines of the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH) and meets the acceptance criteria. The experimental data indicate that the course of the oxidation process depends on the type of fluoroquinolone (FQ), the incubation time and temperature. The performed kinetic evaluation allowed us to state that the oxidation of FQs proceeds according to the second-order kinetics. The degradation products of the FQs were identified using the UHPLC-MS/MS method and their structures were proposed. The results obtained by the TLC-direct bioautography technique allowed us to state that the main ciprofloxacin and pefloxacin oxidation products probably retained antibacterial activity against Escherichia coli.

The oxidation of lomefloxacin (LOM) and balofloxacin (BAL) under the influence of azo initiator of radical reactions of 4,4′-azobis(4-cyanopentanoic acid) (ACVA) and H₂O₂ was examined. Oxidation using H₂O₂ was performed at room temperature while using ACVA at temperatures: 40, 50, 60 °C. Additionally, the oxidation process of BAL under the influence of KMnO₄ in an acidic medium was investigated. New stability-indicating HPLC methods were developed in order to evaluate the oxidation process. Chromatographic analysis was carried out using the Kinetex 5u XB—C18 100A column, Phenomenex (Torrance, CA, USA) (250 × 4.6 mm, 5 μm particle size, core shell type). The chromatographic separation was achieved while using isocratic elution and a mobile phase with the composition of 0.05 M phosphate buffer (pH = 3.20 adjusted with o-phosphoric acid) and acetonitrile (87:13 v/v for LOM; 80:20 v/v for BAL). The column was maintained at 30 °C. The methods were validated according to the ICH guidelines, and it was found that they met the acceptance criteria. An oxidation process followed kinetics of the second order reaction. The most probable structures of LOM and BAL degradation products formed were assigned by the UHPLC/MS/MS method.

Vitamin K is a group of lipophilic molecules. Forms of vitamin K play an essential role in the activation of specific proteins involved in blood clotting cascade or bone metabolism. Another molecule belonging to the fat-soluble vitamins group that also plays an important role in calcium metabolism is vitamin D₃. The dietary supplements containing vitamins K and D₃ are one of the most frequently consumed by patients. The objective of this work was to develop a simple, fast and sensitive thin-layer chromatography (TLC)-densitometric procedure for the simultaneous quantitative analysis of vitamins K and D₃ in pharmaceutical products and dietary supplements. The analysis of vitamins was performed on the silica gel RP-18 F₂₅₄s plates with methanol-ethanol-isopropanol in a volume ratio of 15:1:4 as a mobile phase. The densitometric measurements were made at 254 nm. The method was validated by checking the specificity, linearity, precision, recovery, limit of detection, limit of quantification and robustness in accordance with International Conference on Harmonization (ICH) guidelines. The method was shown to be specific, accurate (recoveries were from 95.78 to 104.96%), linear over the tested range (correlation coefficient, exceeding 0.99), and precise (precision and intermediate precision RSD below 2.70% for all analytes). The satisfactory results of the validation of the method indicate that it can be used in the quality control of dietary supplements and pharmaceutical products containing vitamins K and D₃.

Ciprofloxacin (CIP), moxifloxacin (MOX), norfloxacin (NOR) and ofloxacin (OFL), are the antibacterial synthetic drugs, belonging to the fluoroquinolones group. Fluoroquinolones are compounds susceptible to photodegradation process, which may lead to reduction of their antibacterial activity and to induce phototoxicity as a side effect. This paper describes a simple, sensitive UPLC-MS/MS method for the determination of CIP, MOX, NOR and OFL in the presence of photodegradation products.