Quantitative Analysis of Busulfan in Human Plasma by LC-MS–MS

High-performance liquid chromatography with tandem mass spectrometry has been used for rapid, specific, and sensitive analysis of busulfan in human plasma. Busulfan-d₈ was used as internal standard. Analysis was performed on a C₁₈ column (50 mm × 2.1 mm, 3.5-µm particles) with water–methanol 80:20 (v/v) as mobile phase at a flow-rate of 0.30 mL min⁻¹. Detection was by tandem triple–quadrupole mass spectrometry with turbo ion-spray ionization. Linear calibration plots were obtained over the concentration range 1.096–1,096 ng mL⁻¹. The assay is ideally suited to monitoring of busulfan and determination of its pharmacokinetic data.

     

Quantitative Analysis of Busulfan in Human Plasma by LC-MS–MS

High-performance liquid chromatography with tandem mass spectrometry has been used for rapid, specific, and sensitive analysis of busulfan in human plasma. Busulfan-d₈ was used as internal standard. Analysis was performed on a C₁₈ column (50 mm × 2.1 mm, 3.5-µm particles) with water–methanol 80:20 (v/v) as mobile phase at a flow-rate of 0.30 mL min^?1. Detection was by tandem triple–quadrupole mass spectrometry with turbo ion-spray ionization. Linear calibration plots were obtained over the concentration range 1.096–1,096 ng mL^?1. The assay is ideally suited to monitoring of busulfan and determination of its pharmacokinetic data.     

The use of online heart‐cutting high‐performance liquid chromatography coupled with linear ion trap mass spectrometry in the identification of impurities in vidarabine monophosphate

It is difficult to identify unknown impurities in nucleotide analogues by mass spectrometry because mass‐spectrometry‐incompatible mobile phases need to be used to separate the major ingredient from impurities. In this study, vidarabine monophosphate was selected, and unknown impurities were identified by online heart‐cutting two‐dimensional high‐performance liquid chromatography and linear ion trap mass spectrometry. The one‐dimensional reversed‐phase column was filled with a mobile phase containing nonvolatile salt. In two‐dimensional high‐performance liquid chromatography, we used an Acclaim Q1 column with volatile salt, and the detection wavelength was 260 nm. The mass spectrum was scanned in positive‐ and negative‐ion mode. The online heart‐cutting and online demineralization technique ensured that the mobile phase was compatible with mass spectrometry; seven impurities were identified by MS² and MS³ fragments. The mass fragmentation patterns of these impurities were investigated. The two isomers were semiprepared and complemented by nuclear magnetic resonance. The results were further compared with those of normal‐phase high‐performance liquid chromatography with mass spectrometry. The online heart‐cutting two‐dimensional high‐performance liquid chromatography with mass spectrometry was superior in identifying more impurities. The method solves the problem of incompatibility between the mobile phase and mass spectrometry, so it is suitable for identifying unknown impurities. This method may also be used for investigating impurities in other nucleotide analogues.     

HPLC column-switching technique for sample preparation and fluorescence determination of propranolol in urine using fused-core columns in both dimensions

A new and fast high-performance liquid chromatography (HPLC) column-switching method using fused-core columns in both dimensions for sample preconcentration and determination of propranolol in human urine has been developed. On-line sample pretreatment and propranolol preconcentration were performed on an Ascentis Express RP-C-18 guard column (5?×?4.6 mm), particle size, 2.7 μm, with mobile phase acetonitrile/water (5:95, v/v) at a flow rate of 2.0 mL min^?1 and at a temperature of 50 °C. Valve switch from pretreatment column to analytical column was set at 4.0 min in a back-flush mode. Separation of propranolol from other endogenous urine compounds was achieved on the fused-core column Ascentis Express RP-Amide (100?×?4.6 mm), particle size, 2.7 μm, with mobile phase acetonitrile/water solution of 0.5 % triethylamine, pH adjusted to 4.5 by means of glacial acetic acid (25:75, v/v), at a flow rate of 1.0 mL min^?1 and at a temperature of 50 °C. Fluorescence excitation/emission detection wavelengths were set at 229/338 nm. A volume of 1,500 μL of filtered urine sample solution was injected directly into the column-switching HPLC system. The total analysis time including on-line sample pretreatment was less than 8 min. The experimentally determined limit of detection of the method was found to be 0.015 ng mL^?1.

Quantification of Clarithromycin in Human Plasma by UPLC-MS-MS

A selective, rapid and sensitive ultra performance liquid chromatography tandem mass spectrometry method was developed for the quantitative determination and pharmacokinetic study of clarithromycin in human plasma. The analyte was extracted from human plasma under alkaline condition with diethyl ether. Separation was performed on an ACQUITY UPLC BEH C₁₈ column (50 mm × 2.1 mm i.d., 1.7 μm) with gradient elution at a flow-rate of 0.30 mL min^?1. The mobile phase was 50 mM ammonium acetate (pH 6.8) and acetonitrile. The detection was performed on a triple-quadruple tandem mass spectrometer by multiple reaction monitoring (MRM) mode via electrospray ionization. Linear calibration curves were obtained in the concentration range of 1–3,000 ng mL^?1, with a lower limit of quantification (LLOQ) of 1 ng mL^?1. The intra- and inter-day precision (RSD) values were below 10% and accuracy (RE) ranged from ?7.2 to 6.1% at all QC levels. The method was utilized to support clinical pharmacokinetic study in healthy volunteers following oral administration of clarithromycin extended release tablets.     

Chemometrically Assisted Development and Validation of LC for Simultaneous Determination of Carbamazepine and Its Impurities Iminostilbene and Iminodibenzyl in Solid Dosage Form

A chemometrical approach was applied to develop a reversed-phase liquid chromatographic method for simultaneous determination of carbamazepine and its impurities iminostilbene and iminodibenzyl in solid dosage form. According to contemporary literature, no method was developed for simultaneous determination of carbamazepine and these impurities by chemometrical approach. The fractional factorial design was used for selection of variables significantly influencing the chromatographic separation of the investigated substances. The investigated variables were: temperature of the column, the percentage of organic modifier, the acetate buffer concentration and pH of water phase. The first three variables were proved to be significant and were optimized by face centered, central composite design. Investigation was performed using C18 XBridge Shield analytical column (50 mm × 4.6 mm i.d., particle size 3.5 µm). The optimal conditions for the separation were established with the mobile phase composition of methanol–10 mM acetate buffer (pH adjusted to 2.21 with glacial acetic acid) (50:50, v/v) at a flow rate of 1.5 mL min^?1, 25 °C column temperature and detection at 260 nm. Total analysis time was shortened to about 8 min. Finally, the method was successfully validated and subsequently applied to the analysis of commercially available carbamazepine tablets.     

Comparison of Two Stability-Indicating Chromatographic Methods for the Determination of Mirabegron in Presence of Its Degradation Product

Mirabegron is a novel β₃-adrenoceptor agonist containing an amide group. It was subjected to stress conditions of acidic and alkaline hydrolyses. The hydrolytic degradation product was isolated and its structure was confirmed using mass and IR spectrometry. Two stability-indicating chromatographic methods have been proposed for the determination of mirabegron. TLC method was applied using silica gel as stationary phase and chloroform–methanol–ammonia (9.0:1.0:0.1 by volume) as the mobile phase, and chromatograms were scanned at 250 nm. Accurate determination of the drug was achieved over the concentration range of 2–12 μg per band. In addition, an isocratic HPLC method was developed on Agilent C18 column (150 mm × 4.5 mm I.D., particle size 5 µm) using ethanol-phosphate buffer pH 2.5 (30:70, by volume) as a mobile phase with flow rate of 1 mL min^?1.The intact drug was detected at 250 nm with running time less than 5 min. Mirabegron was determined accurately in a concentration range of 1–25 µg mL^?1. The proposed chromatographic methods were applied successfully for the assay of mirabegron in pharmaceutical dosage form and both methods were validated as per the International Conference on Harmonization guidelines and statistically compared with a reported gradient HPLC method.     

Simultaneous Determination of Ramipril and Its Active Metabolite Ramiprilat in Human Plasma by LC–MS–MS

A selective, rapid and sensitive liquid chromatography tandem mass spectrometry method has been developed for the simultaneous determination of ramipril and ramiprilat in human plasma using enalapril as the internal standard via one-step extraction with ethyl acetate under acidic condition. The analysis was carried out on a Diamonsil C₁₈ column (150 mm × 4.6 mm i.d., 5 μm) with a mobile phase consisting of 1% formic acid-acetonitrile (25:75, v/v) at a constant flow rate of 0.5 mL min^?1. The detection was performed on a triple-quadruple tandem mass spectrometer by selective reaction monitoring mode via electrospray ionization. Linear calibration curves of ramipril and ramiprilat were obtained in the concentration range of 0.107–107.0 and 0.262–105.0 ng mL^?1, respectively. The intra- and inter-day precision (RSD) values were below 8.2 and 4.8% for ramipril, 10.4 and 12.3% for ramiprilat, and accuracy (RE) were within ±5.5 and ±3.2%, respectively at all QC levels. The method was utilized to support clinical pharmacokinetic studies in healthy volunteers following oral administration of ramipril tablets.     

Validated Chromatographic Methods for the Determination of Process Related Toxic Impurities in Pantoprazole Sodium

A GC–MS method for the simultaneous determination of two process related toxic impurities viz. 2-(chloromethyl)-3,4-dimethoxypyridine hydrochloride (CDP) and dimethyl sulfate (DMS) and RP-LC for the routine determination of CDP in pantoprazole sodium (PPS) are presented. In GC–MS, a temperature gradient program was performed on a capillary DB-624 column (60 m × 0.32 mm × 1.8 μm). LC analysis of CDP was done on a Novaflex C18 (250 × 4.6 mm, 5 μm) column using mobile phase containing buffer (0.02 M potassium dihydrogen phosphate and 0.0025 M di potassium hydrogen phosphate) and acetonitrile in 46:54 v/v ratio. The flow rate was 1.0 mL min^?1 and the elution was monitored at 220 nm. Both methods were validated as per International Conference on Harmonization (ICH) guidelines. GC–MS is able to quantitate up to 3.0 ppm of CDP and DMS whereas with RP-LC up to 9.0 ppm of CDP could be quantitated.     

Simultaneous Determination of Diclofenac Sodium and Rabeprazole Sodium in Bulk and Pharmaceutical Dosage Form by LC

A simple, selective, rapid, precise and accurate reverse phase high pressure liquid chromatographic method has been developed for the simultaneous estimation of diclofenac sodium and rabeprazole sodium from pharmaceutical formulations. The method was developed using a HiQ SiL C18 (250 mm × 4.6 mm i.d.) column with a mobile phase consisting of methanol:water, (80:20 v/v), at a flow rate of 1.25 mL min⁻¹. Detection was carried out at 284 nm. Indapamide was used as an internal standard. The developed method was validated for linearity, accuracy, precision, limit of detection and limit of quantitation. The proposed method can be used for the estimation of these drugs in combined dosage forms.

     

Characterization of Nineteen Impurities in Roxithromycin by HPLC/TOF and Ion Trap Mass Spectrometry

Nineteen impurities in roxithromycin drug substance made in China were separated and identified by HPLC–MSⁿ (TOF and TRAP) for the further improvement of official monographs in Pharmacopoeias. The fragmentation patterns and structural assignment of these impurities were studied. The column was Shim VP-ODS (250 × 4.6 mm, 5 μm). The mobile phase was 10 m mol L⁻¹ ammonium acetate and 0.1 % formic acid aqueous solution-acetonitrile (62.5:37.5). In positive mode, full scan LC–MS was first performed to obtain the m/z value of the protonated molecules and formulas of all detected peaks on Agilent 6538Q TOF high resolution mass spectrometer. LC–MS-MS and LC–MS-MS–MS were then carried out on the compounds of interest on AB SCIEX 4000 Q TRAP™ composite triple quadrupole/linear ion trap tandem mass spectrometer. The complete fragmentation patterns of nineteen impurities were studied and used to obtain information about the structures of these impurities. The structures of nineteen impurities in roxithromycin drug substance were deduced based on the HPLC–MSⁿ data, in which nine impurities were novel impurities.

     

SPE and LC–ESI–MS for Quantitative Analysis of Mitiglinide in Human Plasma in a Bioequivalence Study

Liquid chromatography–electrospray ionization mass spectrometry has been used for rapid, selective, and sensitive quantitative analysis of mitiglinide in human plasma. Sample pretreatment involved solid-phase extraction from plasma with gliclazide as internal standard. Separation was performed on a C₁₈ column (150 × 2.0 mm) with 71:29 (v/v) acetonitrile–water (containing 0.1% formic acid and 0.2 mmol L^?1 ammonium acetate) as mobile phase at a flow rate of 0.2 mL min^?1. The method was validated then successfully applied to a clinical bioequivalence study of mitiglinide in 20 healthy volunteers after oral administration.     

Simultaneous Determination of Diclofenac Sodium and Rabeprazole Sodium in Bulk and Pharmaceutical Dosage Form by LC

A simple, selective, rapid, precise and accurate reverse phase high pressure liquid chromatographic method has been developed for the simultaneous estimation of diclofenac sodium and rabeprazole sodium from pharmaceutical formulations. The method was developed using a HiQ SiL C18 (250 mm × 4.6 mm i.d.) column with a mobile phase consisting of methanol:water, (80:20 v/v), at a flow rate of 1.25 mL min^?1. Detection was carried out at 284 nm. Indapamide was used as an internal standard. The developed method was validated for linearity, accuracy, precision, limit of detection and limit of quantitation. The proposed method can be used for the estimation of these drugs in combined dosage forms.     

Characterization of Nineteen Impurities in Roxithromycin by HPLC/TOF and Ion Trap Mass Spectrometry

Nineteen impurities in roxithromycin drug substance made in China were separated and identified by HPLC–MSⁿ (TOF and TRAP) for the further improvement of official monographs in Pharmacopoeias. The fragmentation patterns and structural assignment of these impurities were studied. The column was Shim VP-ODS (250 × 4.6 mm, 5 μm). The mobile phase was 10 m mol L^?1 ammonium acetate and 0.1 % formic acid aqueous solution-acetonitrile (62.5:37.5). In positive mode, full scan LC–MS was first performed to obtain the m/z value of the protonated molecules and formulas of all detected peaks on Agilent 6538Q TOF high resolution mass spectrometer. LC–MS-MS and LC–MS-MS–MS were then carried out on the compounds of interest on AB SCIEX 4000 Q TRAP? composite triple quadrupole/linear ion trap tandem mass spectrometer. The complete fragmentation patterns of nineteen impurities were studied and used to obtain information about the structures of these impurities. The structures of nineteen impurities in roxithromycin drug substance were deduced based on the HPLC–MSⁿ data, in which nine impurities were novel impurities.     

On-Line Concentration Methods for Analysis of Fat-Soluble Vitamins by MEKC

A fast, selective and sensitive reversed phase liquid chromatographic method employing a C-18 column has been developed and validated for simultaneous analysis of four impurities of duloxetine hydrochloride, an antidepressant drug, viz., (S)-N,N-dimethyl-3-hydroxy-(2-thienyl)-propanamine, phenolic impurity, 1-napthol and duloxetine succinamide. Good separations were achieved by a gradient elution with mobile phase consisting of a mixture of phosphate buffer 14 mM containing 0.1% of sodium octanesulfonate, pH 3.0, at a flow rate of 0.8 mL min^?1. The detection was at 220 nm. The method was validated for precision, linearity and accuracy. Finally, the developed method was used to quantify the impurities during stability sample analysis of duloxetine hydrochloride drug products.     

Rapid Determination of Cichoric Acid by Argentation Complex Chromatography and Study on Related Mechanisms of Coordination Simultaneously Used in Rapid Determination of Salvianolic Acid B

Cichoric acid is a water-soluble phenolic acid in Echinacea purpurea and has a high medicinal value. A rapid and novel argentation complex liquid chromatography method has been developed and validated for determination of cichoric acid in E. purpurea extract. The determination of cichoric acid was carried out on a Restek Pinnacle 11 C18 column (250 mm × 4.6 mm, 5 μm), using acetonitrile-deionized water (38:62, v/v, with 6 mmol L^?1 AgNO₃ and 0.8% acetic acid) as the mobile phase at a flow rate of 1.0 mL min^?1 within 10 min. The wavelength was set at 326 nm. It improved the effect of determination by adding AgNO₃ in the mobile phase while cichoric acid coordinated with Ag⁺. The mechanism of coordination between cichoric acid and Ag⁺ has been studied by Fourier transform infrared spectroscopy, electrospray ionization mass spectrometry. The mechanism which improved the effect of determination of cichoric acid is analyzed and applied in the rapid determination of salvianolic acid B (Sal B) in Danshen extract solution which has been stored for half a year. The possible structures of the complex and complex ratio are all provided in this article. The experiments have facilitated the study of cichoric acid–Ag⁺ and Sal B–Ag⁺ complex and provide a theoretical basis for industrialized extraction of cichoric acid and Sal B in the future.     

Comparison of Full Factorial Design,Central Composite Design,and Box-Behnken Design in Chromatographic Method Development for the Determination of Fluconazole and Its Impurities

This paper presents the development and optimization of a liquid chromatographic method for the determination of fluconazole and its impurities by experimental design methodology. Four experimental design types were applied: two-level full factorial design, central composite design, Box-Behnken design, and three-level full factorial design. The advantages and drawbacks of each design are described and detailed statistical evaluation of mathematical models was performed. The central composite design and three-level full factorial design created significantly better models comparing to the other methods. As the central composite design requires a smaller number of experiments, its models were used for theoretical examination of experimental space. Multiobjective optimization aiming to achieve maximal separation of all investigated substances and minimal analysis duration was performed by a grid point search. The defined optimal separation was achieved on a C₁₈ (125 mm × 4 mm, 5 µm particle size) column with a mobile phase consisting of acetonitrile and water (5 mM ammonium formate) (15:85, v/v); a column temperature of 25°C; a flow rate of 1.2 mL min^?1; and a detection wavelength of 260 nm.     

UPLC-ESI-MS-MS Determination of Three β2-Agonists in Pork

The chromatographic behaviour of bupropion hydrochloride, a basic drug of pK _a 7.9, has been investigated under reversed-phase ion-pairing conditions and the results were used to develop a method for analysis of bupropion hydrochloride in pharmaceuticals. Chromatographic separation of bupropion hydrochloride and carbamazepine (used as internal standard) was performed on a C₈ column (150 mm × 4.6 mm i.d., 3.5-μm particle), with 40:10:50 (v/v) methanol–acetonitrile–phosphate buffer (20 mm, pH 3.0), containing 10 mm 1-heptane sulfonic acid sodium salt (1-HSA), as optimum mobile phase at a flow rate of 1.0 mL min^?1. UV detection was at 254 nm. The fully validated method enables reproducible and selective analysis of bupropion hydrochloride in pharmaceuticals.     

UPLC for the Determination of Clopidogrel in Dog Plasma by Tandem Quadrupole MS: Application to a Pharmacokinetic Study

A rapid, sensitive and specific ultra performance liquid chromatography-electrospray ionization tandem quadrupole mass spectrometry method was developed and validated for the determination of clopidogrel in dog plasma. Plasma samples were deproteinized with acetonitrile and separated on a Waters BEH C18 column (1.7 μm, 50 mm × 2.1 mm id.) with isocratic elution at a flow-rate of 0.2 mL min^?1 and mobile phase consisting of acetonitrile and water (containing 0.15% formic acid) (75:25, v/v). The single run analysis was as shorter as 2 min. Electrospray ionization in positive ion mode and multiple reaction monitoring were used for the quantification of clopidogrel with monitored transitions m/z 322 → 212 for clopidogrel and m/z 324 → 217 for internal standard (gliclazide). The intra- and inter-day precisions (RSD%) were less than 6.32 and 7.03%, and accuracy (RE%) between ?9.12 and 9.65% (n = 6). The extraction recovery of clopidogrel was 96.7%. The developed method was successfully applied to the pharmacokinetic study of clopidogrel tablets in dogs following oral administration at a single dose of 75 mg.     

Determination of Toosendanin Extracted from Traditional Chinese Medicine: the Fruit of Melia azedarach LC–FD Detection

A rapid and selective reversed-phase liquid chromatography with fluorescence detection was developed and validated for the determination of toosendanin in the fruit of Melia azedarach. After extraction, the extracts were analysed at 25 °C using Eclipse XDB-C18 column (4.6 mm × 150 mm; 5 μm) and a mobile phase consisting of methanol–water at a flow rate of 1.0 mL min^?1. Detection wavelength was set at λ_Ex = 230 nm, λ_Em = 320 nm. The linearity, accuracy, and precision of the method were good, and the method can be successfully used to investigate the level of toosendanin component in herb samples with satisfactory results.