Journal of Chromatography B (v.878, #32)

Compound Danshen tablets are composed of Panax notoginseng, Salvia miltiorrhiza and Borneol. The tablets are prescribed for treatment of cardiovascular diseases in China. The present study aimed at developing a specific and sensitive LC–MS/MS method to simultaneously determine three bioactive P. notoginseng saponins, i.e., notoginsenoside R1, ginsenoside Rg1 and Rb1, in dogs after a single oral administration of the compound tablets in order to obtain the clinically relevant saponin-related pharmacodynamics of the tablets in patients. The R1, Rg1 and Rb1 were extracted from dog plasma with acetone–methanol (80:20, v/v), separated by reversed phase liquid chromatography and determined by tandem mass spectrometry (LC–MS/MS) with positive electrospray ionization (ESI). The developed method reached lower limit of quantitation (LLOQ) at 0.10 ng/ml for the three saponins. The method was validated in terms of selectivity, matrix effects, linearity, precision and accuracy, and then was applied to a pharmacokinetic study of the three bioactive saponins simultaneously in dogs after a single oral administration of compound Danshen tablets at a clinical equivalent dose. The C max and AUC(0−∞) for R1, Rg1 and Rb1 were 1.91, 3.34 and 28.6 ng/ml, and 7.5, 11.0, and 1712 (h ng/ml), respectively.
Keywords: Compound Danshen tablets; notoginsenoside R1; ginsenoside Rg1; ginsenoside Rb1; LC–MS/MS; Pharmacokinetics;

Disorders in choline metabolism are related to disease conditions. We developed a stable-isotope dilution ultra performance liquid chromatography–mass spectrometry (UPLC–MS/MS) method for the simultaneous quantification of acetylcholine (ACh), betaine, choline, and dimethylglycine (DMG). We used this method to measure concentrations of the analytes in plasma and urine in addition to other biological fluids after a protein precipitation by acetonitrile. The detection limits were between 0.35 nmol/L (for ACh in urine) and 0.34 μmol/L (for betaine in urine). ACh concentrations were not detectable in plasma. Intraassay and interassay coefficient of variation (CVs) were all <10.0% in biological fluids, except for DMG in cerebrospinal fluid (CV = 12.44%). Mean recoveries in urine pool samples were between 99.2% and 103.9%. The urinary excretion of betaine, choline, and DMG was low, with approximately 50.0% higher excretion of choline in females compared to males. Median urinary excretion of ACh were 3.44 and 3.92 μmol/mol creatinine in males and females, respectively (p  = 0.689). Plasma betaine concentrations correlated significantly with urinary excretions of betaine (r  = 0.495, p  = 0.027) and choline (r  = 0.502, p  = 0.024) in females. Plasma choline concentrations correlated significantly with urinary excretion of ACh in males (r  = 0.419, p  = 0.041) and females (r  = 0.621, p  = 0.003). The new method for the simultaneous determination of ACh, betaine, choline, and DMG is sensitive, precise, and fast enough to be used in clinical investigations related to the methylation pathway.
Keywords: Acetylcholine; Choline; Betaine; Dimethylglycine; Homocysteine;

Application of a liquid chromatography/tandem mass spectrometry method to pharmacokinetic study of mangiferin in rats by Yiming Liu; Fuping Xu; Xing Zeng; Liu Yang; Yuanhui Deng; Zhifeng Wu; Yi Feng; Xiong Li (3345-3350).
A simple, rapid and accurate liquid chromatography–electrospray ionization-tandem mass spectrometry method was developed and validated for quantification of mangiferin in rat plasma. After the addition of the internal standard (IS) paracetamol, plasma samples were pretreated by protein precipitation. Chromatographic separation was carried out on a C18 column by isocratic elution with methanol–acetonitrile–1% acetic acid (40:3:57, v/v/v). The detection was performed on a Sciex API 3000 LC/MS/MS with TurboIonSpray ionization (ESI) inlet in the positive ion MRM mode. Good linearity was achieved over the concentration range of 3.01–601 ng/mL. Intra- and inter-day precisions were less than 9.1%, and accuracy ranged from 100.5% to 104.0%. The pharmacokinetic profiles of free mangiferin at three dose levels and mangiferin in Zhimu decoction and Zhimu–Huangbai decoction were studied for the first time in rats by this method. After single intragastric administration of free mangiferin 17.5, 35 and 70 mg/kg, C max and AUC increased but non-proportional to the doses. At the same dose level (35 mg/kg), C max and AUC of mangiferin in two decoctions were significantly higher than the corresponding values of free mangiferin.
Keywords: Mangiferin; LC/MS/MS; Pharmacokinetics; Rat plasma;

Enantioselective determination of cetirizine in human plasma by normal-phase liquid chromatography–atmospheric pressure chemical ionization–tandem mass spectrometry by Seung Woo Kang; Hae Jong Jang; Victor S. Moore; Ji-Young Park; Kyoung-Ah Kim; Jeong-Rok Youm; Sang Beom Han (3351-3357).
A highly sensitive and enantioselective method has been developed and validated for the determination of levocetirizine [(R)-cetirizine] in human plasma by normal-phase liquid chromatography coupled to tandem mass spectrometry with an atmospheric pressure chemical ionization (APCI) interface in the positive ion mode. Enantioselective separation was achieved on a CHIRALPAK AD-H column using an isocratic mobile phase consisting of a mixture of n-hexane, ethyl alcohol, diethylamine, and acetic acid (60:40:0.1:0.1, v/v/v/v). Levocetirizine-D8 was used as an internal standard (IS). Levocetirizine and the IS were detected by multiple-reaction monitoring (MRM). Mass transitions of analyte and IS were m/z 389.2 → 201.1 and 397.2 → 201.1, respectively. Under optimized analytical conditions, a baseline separation of two enantiomers and IS was obtained in less than 11 min. Samples were prepared by a simple two-step extraction by protein precipitation using acetonitrile followed by liquid–liquid extraction with a n-hexane–dichloromethane mixture (50:50, v/v). The standard curve for levocetirizine was linear (r 2  > 0.995) in the concentration range 0.5–300 ng/mL. Recovery was between 97.0 and 102.2% at low, medium, and high concentration. The limit of quantification (LOQ) was 0.5 ng/mL. Other method validation parameters, such as precision, accuracy, and stability, were very satisfactory. Finally, the proposed method was successfully applied to the study of enantioselective oral pharmacokinetics of levocetirizine in healthy Korean volunteers.
Keywords: Levocetirizine; Enantioselective; Normal-phase liquid chromatography; Tandem mass spectrometry; Pharmacokinetic study;

A method for the simultaneous determination of pregnenolone and 17α-hydroxypregnenolone by high-performance liquid chromatography with an immobilized cholesterol oxidation enzyme reactor was developed. Pregnenolone and 17α-hydroxypregnenolone were converted to progesterone and 17α-hydroxyprogesterone, respectively, by the immobilized enzyme packed into the reactor column, and could thus be monitored by UV absorption at 240 nm. The calibration curves for pregnenolone and 17α-hydroxypregnenolone were linear in the range of 0.4–10 and 0.3–10 μg/ml with a correlation coefficient of 0.9993 and 0.9998, respectively. The detection limit at a signal-to-noise ratio of 3 was 0.12 and 0.08 μg/ml for pregnenolone and 17α-hydroxypregnenolone, respectively. The conversion rate of pregnenolone to progesterone and 17α-hydroxypregnenolone to 17α-hydroxyprogesterone was 90.6% and 99.3%, respectively. Intra-day and inter-day precision (in terms of percentage coefficient of variation) were less than 9.3%, with accuracy greater than 94.8%. This method was successfully applied to the simultaneous determination of pregnenolone and 17α-hydroxypregnenolone secreted into the culture medium of bovine adrenal fasciculata cells and of both analytes produced within the cells.
Keywords: Immobilized enzyme reactor; Cholesterol oxidation; Progesterone; 17α-Hydroxypregnenolone; Pre-column; Semi-micro high-performance liquid chromatography;

Determination of Bisphenol A and its chlorinated derivatives in placental tissue samples by liquid chromatography–tandem mass spectrometry by I. Jiménez-Díaz; A. Zafra-Gómez; O. Ballesteros; N. Navea; A. Navalón; M.F. Fernández; N. Olea; J.L. Vílchez (3363-3369).
The group of compounds commonly called endocrine disruptors covers a wide range of synthetic and natural substances able to alter the normal hormone function of wildlife and humans, consequently causing adverse health effects. Bisphenol A (BPA) and its chlorinated derivatives are some of these compounds. In this work, we propose a new liquid chromatography–tandem mass spectrometry (LC–MS/MS) method to determine these compounds in human placental tissue samples. The method involves an extraction phase of the extracts from the samples using ethyl acetate, followed by a clean-up phase by centrifugation prior to their quantification by LC–MS/MS using an atmospheric pressure chemical ionization (APCI) interface in the negative mode. Deuterated Bisphenol A (BPA-d16) was used as internal standard. Found detection limits (DL) ranged from 0.2 to 0.6 ng g−1 and quantification limits (QL) from 0.5 to 2.0 ng g−1 for Bisphenol A and its chlorinated derivatives, while inter- and intra-day variability was under 8.1%. The method was validated using standard addition calibration and a spike recovery assay. Recovery rates for spiked samples ranged from 97% to 105%. This method was satisfactorily applied to the determination of BPA and its chlorinated derivatives in 49 placental tissue samples collected from women who live in the province of Granada (Spain).
Keywords: Bisphenol A; Bisphenol A chlorinated derivatives; Liquid chromatography–tandem mass spectrometry (LC–MS/MS); Placental tissue analysis;

HPLC–MS/MS shotgun proteomic research of deer antlers with multiparallel protein extraction methods by Liang Gao; Dingyin Tao; Yichu Shan; Zhen Liang; Lihua Zhang; Yushu Huo; Yukui Zhang (3370-3374).
Deer antlers mature rapidly in 60 days, and subsequently shed in 5 days with rapid ossification. During this procedure, the function of deer antlers changes significantly. Therefore, the profiling of antler proteome is helpful to discover important growing and shedding regulation proteins, which might be of great significance for studying development and regeneration. In this study, a parallel protein extraction strategy was developed to extract proteins from antlers of red deer with five different lysis solutions, followed by shotgun proteomic analysis by microflow reversed-phase liquid chromatography/electrospray ionization/tandem mass spectrometry (μRPLC–ESI-MS/MS) with a 30 cm-long serially coupled microcolumn. Our experimental results showed that the identified proteins extracted by five kinds of lysis solution were complementary to each other. In total, 416 unique proteins were identified, with relative molecular masses from 2000 to 600,000, and isoelectric points from 3.84 to 11.57. All these results demonstrate that the combination of parallel protein extraction strategy and μRPLC–ESI-MS/MS analysis with serially coupled long microcolumns might be of great significance for comprehensive proteomic research of deer antler.
Keywords: Deer antler; μRPLC–ESI-MS/MS; Parallel protein extraction; Shotgun proteomic research; Serially coupled microcolumn;

The individual flavonoid component, scutellarin, scutellarein, luteolin and apigenin, in Scutellaria barbata plant was isolated based on the macro porous adsorbent with high adsorption selectivity. These adsorbents were synthesized based on the copolymerization of methyl acrylate and divinylbenzene (MA-co-DVB). So the polarity and the adsorption affinity of these adsorbents can be adjusted through changing MA content in the adsorbents. And then the ability of the adsorbent with different MA contents for isolation of these four individual flavonoid was also investigated. Adsorbents M2 and M4, with MA content of 25% and 45%, respectively, demonstrated the best separation ability. Complete separation of the four flavone compounds was achieved in a continuous process based on combination of adsorbents with different polarities (M2 and M4). Gradient elution using adsorbent M4 separated the four flavonoids into three fractions, which were determined to contain scutellarin, scutellarein and a mixture of luteolin and apigenin. The latter was separated completely by adsorbent M2 subsequently. All four compounds were obtained at high resolution and high recovery yield (96.7%, 94.1%, 95.8% and 93.8%, respectively), suggesting the efficiency of sequentially combined columns with different segregation patterns.
Keywords: Separation; Flavonoid; Scutellaria barbata; Polymeric adsorbent;

This report describes and compares different strategies to deactivate (endcap) epoxide groups and azide groups on bio-chromatographic support surfaces, before and after ligand attachment. Adsorbents possessing epoxide groups were deactivated using acidic hydrolysis or were endcapped with 2-mercaptoethanol or 2-ethanolamine. The influence of surface-bound 2-ethanolamine was demonstrated for the triazine-type affinity adsorbent B14-2LP-FractoAIMs-1, which was tested in combination with the weak anion exchange material 3-aminoquinuclidine-FractoAIMs-3 (AQ-FA3). Azide groups were modified with 2-propargylalcohol using Click-Chemistry. Besides the conventional one-pot Click reaction, an alternative approach was introduced. This optimized Click protocol was employed (i) for the preparation of the weak anion exchange material AdQ-triazole-Fractogel (AdQ-TRZ-FG) and (ii) for the endcapping of residual azide groups with 3-propargyl alcohol. Using the new Click reaction protocol the ligand immobilization rate was doubled from 250 to 500 μmol/g dry adsorbent. Furthermore, the modified support surface was proven to be inert towards the binding of immunoglobulin G (IgG) as well as feed impurities. A thorough evaluation of modified surfaces and adsorbents was performed with dynamic binding experiments using cell culture supernatant containing monoclonal human immunoglobulin G (h-IgG-1). Besides SDS-Page, a recently introduced Protein A – size exclusion HPLC method (PSEC-HPLC) was used to visualize the feed impurity composition and the IgG content of all collected sample fractions in simple PSEC-Plots. A surprising outcome of this study was the irreversible binding of IgG to azide modified surfaces. It was found that organic azide compounds, e.g. 1-azide-3-(2-propen-1-yloxy)-2-propanol (AGE-N3) promote antibody aggregation to a slightly higher extent than the inorganic sodium azide. The possibility that the Hofmeister Series of salt anions may be applicable to predict the properties of the corresponding organic compounds is discussed.
Keywords: Epoxide; Azide; Click reaction; Protein A; Size exclusion; Antibody purification; Protein aggregation; B14-ligand; Cell culture;

Urine is one of the most attractive analyte used for clinical diagnosis. NSCLC (non-small cell lung carcinoma), which includes adenocarcinoma, squamous cell carcinoma and large-cell carcinoma, is a leading cause of cancer-related deaths. In the present study, urinary proteomes of normal individuals and NSCLC patients were compared using 1D SDS-PAGE. From the distinctly differentially expressed bands in SDS-PAGE gel, 40 proteins were identified by chip-HPLC-MS/MS, including five proteins relevant to NSCLC. One of the selected proteins, alpha-1-antichymotrypsin (AACT), was further validated in urine by western blot and in lung tissue by immunohistochemistry staining. Higher expression level of AACT in NSCLC patients was observed by western blot when compared with normal urine samples. Significantly, the NSCLC tumor tissue (18 out of 20 cases, 90%) showed a significantly higher expression level of AACT compared to adjacent non-tumor lung tissue (3 out of 20 cases, 15%). These results establish AACT as a potential biomarker for objective and non-invasive diagnosis of NSCLC in urine and the other four NSCLC-related proteins were also listed.
Keywords: Biomarker; Lung cancer; One-dimensional gel electrophoresis; Proteome; Urine;

An ultra performance liquid chromatography–tandem MS assay for tamoxifen metabolites profiling in plasma: First evidence of 4′-hydroxylated metabolites in breast cancer patients by E. Dahmane; T. Mercier; B. Zanolari; S. Cruchon; N. Guignard; T. Buclin; S. Leyvraz; K. Zaman; C. Csajka; L.A. Decosterd (3402-3414).
There is increasing evidence that the clinical efficacy of tamoxifen, the first and most widely used targeted therapy for estrogen-sensitive breast cancer, depends on the formation of the active metabolites 4-hydroxy-tamoxifen and 4-hydroxy-N-desmethyl-tamoxifen (endoxifen). Large inter-individual variability in endoxifen plasma concentrations has been observed and related both to genetic and environmental (i.e. drug-induced) factors altering CYP450s metabolizing enzymes activity. In this context, we have developed an ultra performance liquid chromatography–tandem mass spectrometry method (UPLC–MS/MS) requiring 100 μL of plasma for the quantification of tamoxifen and three of its major metabolites in breast cancer patients. Plasma is purified by a combination of protein precipitation, evaporation at room temperature under nitrogen, and reconstitution in methanol/20 mM ammonium formate 1:1 (v/v), adjusted to pH 2.9 with formic acid. Reverse-phase chromatographic separation of tamoxifen, N-desmethyl-tamoxifen, 4-hydroxy-tamoxifen and 4-hydroxy-N-desmethyl-tamoxifen is performed within 13 min using elution with a gradient of 10 mM ammonium formate and acetonitrile, both containing 0.1% formic acid. Analytes quantification, using matrix-matched calibration samples spiked with their respective deuterated internal standards, is performed by electrospray ionization–triple quadrupole mass spectrometry using selected reaction monitoring detection in the positive mode. The method was validated according to FDA recommendations, including assessment of relative matrix effects variability, as well as tamoxifen and metabolites short-term stability in plasma and whole blood. The method is precise (inter-day CV%: 2.5–7.8%), accurate (−1.4 to +5.8%) and sensitive (lower limits of quantification comprised between 0.4 and 2.0 ng/mL). Application of this method to patients’ samples has made possible the identification of two further metabolites, 4′-hydroxy-tamoxifen and 4′-hydroxy-N-desmethyl-tamoxifen, described for the first time in breast cancer patients. This UPLC–MS/MS assay is currently applied for monitoring plasma levels of tamoxifen and its metabolites in breast cancer patients within the frame of a clinical trial aiming to assess the impact of dose increase on tamoxifen and endoxifen exposure.
Keywords: Ultra performance liquid chromatography; Tandem mass spectrometry; Tamoxifen; N-Desmethyl-tamoxifen; 4-Hydroxy-tamoxifen; 4-Hydroxy-N-desmethyl-tamoxifen (endoxifen); 4′-Hydroxy-tamoxifen; 4′-Hydroxy-N-desmethyl-tamoxifen; Breast cancer;

Determination of sodium nifurstyrenate and nitrovin residues in edible food by liquid chromatography–tandem mass spectrometry after ultrasound-assisted extraction by Yanfei Tao; Huan Yu; Dongmei Chen; Zhao-Ying Liu; Ding Yang; Yuanhu Pan; Yulian Wang; Lingli Huang; Zonghui Yuan (3415-3420).
A specific and sensitive method based on liquid chromatography–tandem mass spectrometry (LC–MS/MS) has been developed for the determination of nitrovin and sodium nifurstyrenate residues in muscle and liver of swine and chicken and in muscle of fish. Sample preparation procedure includes ultrasound-assisted extraction with acetonitrile, defatting with n-hexane and final clean-up with solid phase extraction (SPE) on Oasis HLB cartridges. The analytes were detected in multiple reaction monitoring (MRM) under negative scan mode acquiring two diagnostic product ions for sodium nifurstyrenate and under positive mode for nitrovin. The averaged decision limits (CCα; α 1%) ranged 0.09–0.26 μg/kg while the detection capability (CCβ; β 5%) was 0.33–0.97 μg/kg in the tissues. Reasonable recoveries (71–110%) spiked in muscle and liver showed excellent relative standard deviation (RSD). The validated method was simple, rapid, sensitive, and complied with the regulations for the determination of nitrovin and sodium nifurstyrenate residues in food matrices.
Keywords: Sodium nifurstyrenate; Nitrovin; Liquid chromatography–tandem mass spectrometry; Residues analysis; Ultrasound-assisted extraction;

In this work, a rapid and selective method was successfully developed using the magnetic molecularly imprinted polymer (MMIP) as sorbent for the extraction of β-lactam antibiotics (BLAs) from milk samples. The MMIP has been prepared using penicillin V potassium (PENV) as template molecule, methacrylic acid as functional monomer, ethylene glycol dimethacrylate as crosslinking agent and Fe3O4 magnetite as magnetic component. The experimental results showed that the MMIP had high affinity and selectivity toward PENV and other structurally related BLAs. The extraction process was carried out in a single step by mixing the extraction solvent, MMIPs and milk samples under ultrasonic action. When the extraction was completed, the MMIPs adsorbing the analytes were separated from the sample matrix by an external magnet. The analytes eluted from the MMIP were analyzed by liquid chromatography–tandem mass spectrometry. For achieving optimal preconcentration and reducing non-specific interactions, various parameters affecting the extraction efficiency such as extraction mode, extraction solvent, the amount of MMIPs, extraction time, washing solution and eluting solution were comprehensively evaluated. Under the optimal conditions, the detection limits of BLAs are in the range of 1.6–2.8 ng mL−1. The relative standard deviations of intra- and inter-day ranging from 3.2% to 8.3% and from 3.6% to 9.8% are obtained, respectively. The method was applied to determine BLAs including PENV, amoxicillin and oxacillin in five milk samples from different provenances. The recoveries of BLAs in these samples from 71.6% to 90.7% are obtained.
Keywords: Magnetic molecularly imprinted polymer; β-Lactam antibiotics; Milk; Liquid chromatography–tandem mass spectrometry;

Pharmacokinetic applicability of a validated liquid chromatography tandem mass spectroscopy method for orally administered curcumin loaded solid lipid nanoparticles to rats by Vandita Kakkar; Sukhjeet Singh; Dinesh Singla; Sudhir Sahwney; Anurag Singh Chauhan; Gangandeep Singh; Indu Pal Kaur (3427-3431).
A simple and sensitive validated LC–MS/MS analytical method was used for determination of curcumin in rat plasma, using nimesulide as internal standard. Analyses were performed on an Agilent LC–MS/MS system using a Chromolith rod™ and isocratic elution with acetonitrile:10 mM ammonium acetate buffer (pH 3.5) (80:20, v/v) at a flow rate of 0.8 ml/min with a total run time of 3 min and an overall recovery of 77.15%. A triple quadrupole mass spectrometer, equipped with an electrospray ionization interface, operated in the negative mode was used. Calibration curve in plasma spiked with varying concentration of curcumin were linear over the concentration range of 10–2000 ng/ml with determination coefficient >0.99. The lower limit of quantification was 10 ng/ml. Intra and inter-day variability's (RSD) for extraction of curcumin from plasma were less than 10% and 15% respectively and accuracy was 102.43–108.5%. Multiple reaction monitoring was used to monitor the transition for curcumin (m/z; 367/217 [M−H]) and IS (m/z; 307/229). The method was applied for determining curcumin concentration in plasma after peroral administration of 50 mg/kg of free curcumin (C-S) or curcumin loaded solid lipid nanoparticles (C-SLNs) to rats. Results established selectivity and suitability of the method for pharmacokinetic studies of curcumin from C-SLNs.
Keywords: Curcumin; LC–MS/MS; Liquid liquid extraction (LLE); Solid lipid nanoparticles (SLNs); Plasma;

Felbamate (2-phenyl-1,3-propanediol dicarbamate) is a second generation antiepileptic drug used to treat seizures refractory to other antiepileptic drugs. With approximately 3500 new patients exposed annually, several important pharmacologic interaction questions remain unanswered necessitating the need for rapid and accurate methods of felbamate analysis in biological matrices. To this end, a rapid liquid chromatography tandem mass spectrometry (LC–MS/MS) method was developed for the measurement of felbamate in mouse plasma and tissues and human plasma. Plasma (100 μL) and tissues homogenates (100 μL of 100 mg/mL) were spiked with internal standard (carisoprodol) prior to protein precipitation with acetonitrile. Samples were chromatographed on a XBridge Phenyl, 2.5 μm, 4.6 mm × 50 mm column with quantitation by internal standard reference monitoring of the ion transitions m/z 239 → 117 for felbamate and m/z 261 → 176 for carisoprodol. Calibration curves were linear from 2.5 to 500 ng/mL in mouse or human plasma and 25–5000 pg/mg in tissue homogenates. Recoveries were greater than 97% for plasma and homogenates with accuracies >92% in any of the mouse matrices and >88% in human plasma. Comparable accuracies and precision were found with and without the use of the internal standard in preparation of the calibration curves and suggest that the internal standard may not be required.
Keywords: Felbamate; LC–MS/MS; Human plasma; Antiepileptic drug; Liquid chromatography tandem mass spectrometry;

A specific, sensitive and widely applicable high performance liquid chromatography with ultraviolet detection (HPLC-UV) method for the determination of moxifloxacin in human plasma was developed and validated in this study. The method involved a single step of liquid–liquid extraction with dichloromethane and the extraction yields more than 80% were achieved. The separation was performed on a common Kromasil C8 column with an isocratic mobile phase. The total time was within 10 min per run. The calibration curve for moxifloxacin was linear in the concentration range of 0.05–5.0 μg/ml with correlation coefficient of 0.9997. The developed method was validated with excellent specificity, sensitivity, accuracy, precision and stability. Using this developed method, the pharmacokinetics of moxifloxacin in healthy Chinese volunteers was studied.
Keywords: Moxifloxacin; HPLC-UV; Validation; Pharmacokinetics;