Simultaneous LC–MS–MS Analysis of Valsartan and Hydrochlorothiazide in Human Plasma

A rapid and specific liquid chromatographic–tandem mass spectrometric method is described for simultaneous analysis of valsartan (VAL) and hydrochlorothiazide (HCTZ) in human plasma. VAL and HCTZ were chromatographed on a C₈ column with 75:15:10 (v/v) acetonitrile–methanol–0.001% aqueous ammonia as mobile phase. VAL and HCTZ were eluted at 0.69 min and 1.22 min, respectively, and, after electrospray ionization (ESI), detected in selected-reaction-monitoring mode. The precursor to product-ion transitions m/z 434.32 → 179.22 and m/z 295.85 → 204.86 were used to quantify VAL and HCTZ, respectively. Recovery by solid-phase extraction was >90% for both analytes and the internal standard. The method was suitable for application to a pharmacokinetic study after oral administration of tablet containing 160 mg VAL and 25 mg HCTZ to 18 healthy volunteers.     

Simultaneous densitometric determination of anthelmintic drug albendazole and its metabolite albendazole sulfoxide by HPTLC in human plasma and pharmaceutical formulations

A new, simple, accurate and precise high‐performance thin‐layer chromatographic method has been developed and validated for simultaneous determination of an anthelmintic drug, albendazole, and its active metabolite albendazole, sulfoxide. Planar chromatographic separation was performed on aluminum‐backed layer of silica gel 60G F₂₅₄ using a mixture of toluene–acetonitrile–glacial acetic acid (7.0:2.9:0.1, v /v/v) as the mobile phase. For quantitation, the separated spots were scanned densitometrically at 225 nm. The retention factors (R _f) obtained under the established conditions were 0.76 ± 0.01 and 0.50 ± 0.01 and the regression plots were linear (r ² ≥ 0.9997) in the concentration ranges 50–350 and 100–700 ng/band for albendazole and albendazole sulfoxide, respectively. The method was validated for linearity, specificity, accuracy (recovery) and precision, repeatability, stability and robustness. The limit of detection and limit of quantitation found were 9.84 and 29.81 ng/band for albendazole and 21.60 and 65.45 ng/band for albendazole sulfoxide, respectively. For plasma samples, solid‐phase extraction of analytes yielded mean extraction recoveries of 87.59 and 87.13% for albendazole and albendazole sulfoxide, respectively. The method was successfully applied for the analysis of albendazole in pharmaceutical formulations with accuracy ≥99.32%.     

Development and validation of a HPLC‐PDA bioanalytical method for the simultaneous estimation of Aliskiren and Amlodipine in human plasma

A simple, unique and selective HPLC‐PDA method was developed and validated for the simultaneous estimation of aliskiren (ALS) and amlodipine (AML) in human plasma. Extraction of the sample was accomplished by protein precipitation. Plasma proteins were precipitated by employing acetonitrile containing hydrochlorothiazide as internal standard. The compounds were analyzed by HPLC by using PDA detector on a Hibar C₁₈ (250 × 4.6 mm) column with a mobile phase comprising acetonitrile and phosphate buffer (pH 4.2 and 25 mm ; 60:40 v/v) with a flow rate of 0.8 mL/min. Different sample pretreatment techniques were evaluated but protein precipitation was found to be satisfactory, offering good recovery values of 97.11–98.45% for ALS and 97.5–99.12% for AML. The within‐day precisions for ALS were 96.66, 99.16 and 99.41% at 90, 240 and 480 ng/mL, respectively, and for AML they were 97.27, 99.54 and 99.31% at 3.3, 8.8 and 17.6 ng/mL, respectively. The between‐day precisions for ALS were 96.66, 99.16 and 99.41% at 90, 240 and 480 ng/mL, respectively and the between‐day precisions for AML were 98.18, 99.20 and 99.40% at 3.3, 8.8 and 17.6 ng/mL, respectively. The limit of quantitation was 30 and 1.0 ng/mL for ALS and AML respectively. Different constituents of plasma proteins did not interfere with the absolute recovery of ALS and AML. Copyright © 2014 John Wiley & Sons, Ltd.     

Dual separation mode for simultaneous determination of antihypertensive drug combinations by high-performance liquid chromatography

A simple, reproducible and efficient dual separation mode high performance liquid chromatographic (HPLC) method was developed for simultaneous determination of antihypertensive drug combinations including; hydrochlorothiazide (HCTZ), valsartan (VAL), amiloride (AML) and captopril (CAP). The newly developed Platinum™ column, which provides a dual-mode separation with its polar and non-polar sites, was used for rapid separation of these co-administered drugs. Good resolution was obtained when Platinum™ column was used compared with C₁₈ column. Additionally, simple isocratic mode with mobile phase containing methanol and 0.02 mole L⁻¹ phosphate buffer adjusted to pH 3.0 (45:55, v/v) was used for separation. The flow rate was 0.5 mL min⁻¹ and effluent was monitored at 270 nm. All the investigated drugs were completely separated within less than 6 min. The linearity range obtained for the developed HPLC method was 0.5-100 μg mL⁻¹ with detection limits of 0.13-1.2 μg mL⁻¹ for all the studied drugs. The method was validated in accordance with the requirements of ICH guidelines and shown to be suitable for intended applications. The method was successfully used for determination of the studied drugs in pure form and pharmaceutical dosage forms without prior need for separation. The method is valuable for quality control laboratories for simultaneous determination of these co-administered antihypertensive drugs in binary, ternary and quaternary mixtures.     

Facile LC‐UV methods for simultaneous monitoring of ciprofloxacin and rosuvastatin in API,formulations and human serum

An efficient, selective and cost‐effective liquid chromatographic assay was developed and validated for the simultaneous quantification of ciprofloxacin and rosuvastatin in Active Pharmaceutical Ingredients (API), pharmaceutical formulations and in human serum. The chromatographic system consisted of mobile phase methanol–water, 90:10 v/v at pH 3.0 adjusted with o‐phosphoric acid, pumped at 1.0 mL/min through a prepacked Purospher Star C18 (5 µm, 25 × 0.46 cm) column and effluent was monitored at the isosbestic point (255 nm) as well as at the λ_max of individual drugs (243 and 271 nm). The method was validated over a linear concentration range of 0.25–15 µg/mL for ciprofloxacin and 0.33–20 µg/mL for rosuvastatin (r² ≥ 0.999). The ranges of reliable response (limits of detection and quantitation) for ciprofloxacin were 3–15 and 9–45 ng/mL and 17–29 and 52–88 ng/mL, respectively, for rosuvastatin in all API, pharmaceutical formulations and human serum. Analytical recovery from human serum was >98% and relative standard deviation (RSD) was <2. The accuracies were 97.13–102.55 and 97.41–101.31% and precisions in RSD were 0.04–1.90 and 0.02–1.23% for ciprofloxacin and rosuvastatin, respectively. No matrix interferences, ion suppression/enhancement and carry‐over were detected. The total assay run time was less than 5 min. In another study, for optimum performance the detector was programmed for multiwavelength scanning at the absorption maxima of each component. Consequently, the linearity range was improved and limit of detection and quantitation values were down to 1–4 and 4–12 ng/mL for ciprofloxacin and 3–5 and 9–15 ng/mL for rosuvastatin, respectively. The validation parameters fitted ICH guidelines through the isosbestic and individual λ_max approach. The small sample volume and simplicity of preparation make this method suitable for use in human serum samples, pharmaceutical formulations, quality control, drug–drug interaction studies, clinical laboratories, drug research centers and forensic medical centers. Copyright © 2014 John Wiley & Sons, Ltd.     

Validated high-performance thin-layer chromatographic method for quantification of gallic acid and ellagic acid in fruits of Terminalia chebula,Phyllanthus emblica,and Quercus infectoria

A simple and rapid high-performance thin-layer chromatographic method for quantification of gallic acid and ellagic acid in dried fruits of Terminalia chebula, Phyllanthus emblica, and Quercus infectoria has been developed. The chromatographic development was carried out on precoated silica gel 60 F₂₅₄ plates in a mixture of toluene:ethyl acetate:chloroform:formic acid (4:8:1:3 v/v/v/v). The plate was scanned densitometrically at a wavelength of 280 nm. The retention factor value of gallic acid and ellagic acid was found to be 0.63 ± 0.2 and 0.53 ± 0.1, respectively. The developed method was validated in terms of linearity, precision, accuracy, sensitivity, robustness, specificity and stability as per the international conference of harmonization guidelines. The method showed good linear relationship over a range of 100–600 ng/band (gallic acid) and 100–500 ng/band (ellagic acid) with a regression coefficient (r²) of 0.997 (gallic acid) and 0.996 (ellagic acid). The method showed high accuracy (99.65%–100.85%). The percentage relative standard deviation of intra-day and inter-day precision studies was not more than 2%. The method is highly robust and has displayed high specificity. The developed method is new, simple, and accurate and can be successfully employed in routine analysis of raw materials and formulations containing gallic acid and ellagic acid.     

Simultaneous determination of atorvastatin,amlodipine, ramipril and benazepril in human plasma by LC‐MS/MS and its application to a human pharmacokinetic study

A rapid, simple, sensitive and specific LC‐MS/MS method has been developed and validated for the simultaneous estimation of atorvastatin (ATO), amlodipine (AML), ramipril (RAM) and benazepril (BEN) using nevirapine as an internal standard (IS). The API‐4000 LC‐MS/MS was operated under the multiple‐reaction monitoring mode using electrospray ionization. Analytes and IS were extracted from plasma by simple liquid–liquid extraction technique using ethyl acetate. The reconstituted samples were chromatographed on C₁₈ column by pumping 0.1% formic acid–acetonitrile (15:85, v/v) at a flow rate of 1 mL/min. A detailed validation of the method was performed as per the FDA guidelines and the standard curves were found to be linear in the range of 0.26–210 ng/mL for ATO; 0.05–20.5 ng/mL for AML; 0.25–208 ng/mL for RAM and 0.74–607 ng/mL for BEN with mean correlation coefficient of ≥0.99 for each analyte. The intra‐day and inter‐day precision and accuracy results were well with in the acceptable limits. A run time of 2.5 min for each sample made it possible to analyze more than 400 human plasma samples per day. The developed assay method was successfully applied to a pharmacokinetic study in human male volunteers. Copyright © 2010 John Wiley & Sons, Ltd.     

Two selective HPTLC methods for determination of some angiotensin II receptor antagonists in tablets and biological fluids

Two simple, selective, precise and highly sensitive high‐performance thin‐layer chromatography (HPTLC) methods have been developed and validated for analysis of five angiotensin II receptor antagonists, namely losartan, irbesartan valsartan, candesartan and olmesartan, which are widely used in clinical practice. HPTLC of the drugs was performed on pre‐coated silica gel HPTLC plates 60 F₂₅₄ by development using a mobile phase composed of chloroform–acetone–glacial acetic acid (7.8:1.5:0.7m v/v/v), which was suitable for all of the studied drugs. The first method depended on utilizing reflectance/fluorescence mode for detection while the second method depended on using 2,3,5,6‐tetrachloro‐1,4‐benzoquinone as spraying reagent for the first time to form orange spots scanned at 460 nm. A good linear relationship was obtained over the concentration ranges of 1.2–60 and 360–3000 ng/band while detection and quantification limits were in the ranges of 0.07–0.43, 45.2–140.49 and 0.21–1.29, 137.05–425.74 ng/band for reflectance/fluorescence and reflectance/absorbance methods respectively. The developed methods were applied successfully for their determination in tablets and spiked human plasma for reflectance/fluorescence method with good accuracy and precision, and so can be applied in the pharmacokinetic and bioavailability studies.     

Quantification of astaxanthin in salmons by chemiluminescence and absorption after TLC separation

Astaxanthin is a keto-carotenoid, belongs to the chemical class of terpenes and is a yellow lipid soluble compound. The compound is present in marine animals like salmons and crustacean. Its colour is due to conjugated double bonds and these double bonds are responsible for its antioxidant effect. Its antioxidant activity is ten times stronger than other carotenoids and nearly 500 fold stronger than vitamin-E. We present a new thin layer chromatography (TLC) method to measure astaxanthin on TLC-plates (Merck, 1.05554) in the visible absorption range as well as by using chemiluminescence. For separation a solvent mixture of cyclohexane and acetone (10?+?2.4, v/v) was used. The RF-value of astaxanthin is 0.14.The limit of detection in vis-absorption is 64?ng / band and the limit of quantification is 92?ng/band. In chemiluminescence the values are 90?ng / band and 115?ng/band. The method offers two independently working measurement modes on a single plate which increase the accuracy of the quantification.     

RP-HPLC Method for the Simultaneous Estimation of Eight Cardiovascular Drugs

The present study describes a convenient method for the separation and simultaneous determination of eight drugs used in cardiovascular diseases, viz., atenolol (ATN), lisinopril (LISI), hydrochlorothiazide (HCTZ), enalapril maleate (ENA), amlodipine besylate (AMLO), losartan potassium (LOSA), valsartan (VAL) and atorvastatin calcium (ATOR) in pharmaceutical formulations. A ZORBAX Rx-C8 column (250 × 4.6 mm, 5 μm particle size) was used with mobile phase consisting of acetonitrile, 10 mM dipotassium hydrogen phosphate buffer (pH 2.2 adjusted with orthophosphoric acid) using a gradient program and quantitative evaluation was performed at 210 nm with a flow rate of 1.0 mL min^?1. Suitability of this method for the quantitative determination of the drugs was proved by validation in accordance with International Conference on Harmonization guidelines. The method is selective, precise, robust, accurate and can be used for routine analysis of 15 combination pharmaceutical formulations in quality control.     

Development and validation of a generic liquid chromatographic method for the simultaneous determination of five commonly used antimalarial drugs: Application to pharmaceutical formulations and human plasma

A simple, sensitive, and rapid liquid chromatographic method was developed and validated using diode array detection for the determination of five commonly used antimalarial drugs in pharmaceutical formulations and in human plasma. Chromatographic separation of antimalarial drugs and internal standard (ibuprofen) was achieved on a C₁₈ column with a mobile phase composed of 10 mM dipotassium orthophosphate at pH 3.0, methanol, and acetonitrile in a ratio of 20:38:42 v/v, at a flow rate of 1 mL/min. The analytes were monitored at 220 nm and separated in ?10 min. The method was validated for linearity, accuracy, precision, limit of quantification, and robustness. Both intra‐ and interday precisions (in terms of %RSD) were lower than 3% and accuracy ranged from 98.1 to 104.5%. Extraction recoveries were ≥96% in plasma. The limits of quantitation for artemether, lumefantrine, pyrimethamine, sulfadoxine, and mefloquine were 0.3, 0.03, 0.06, 0.15, and 0.15 μg/mL in human plasma. Stability under various conditions was also investigated. The method was successfully applied for quantification of antimalarial drugs in marketed formulations and in spiked human plasma. The method can be employed for routine QC purposes and in pharmacokinetic investigations.     

Simultaneous determination of losartan and hydrochlorothiazide in combined dosage forms by first-derivative spectroscopy and high-performance thin-layer chromatography.

Losartan (LST) is the first orally active nonpeptide angiotensin-II receptor antagonist with an improved safety and tolerability profile. It is prescribed alone or in combination with hydrochlorothiazide (HCTZ) for the treatment of moderate-to-severe hypertension. This paper describes the development of 2 methods that use different techniques, first-derivative spectroscopy and high-performance thin-layer chromatography (HPTLC), to determine LST and HCTZ in the presence of each other. LST and HCTZ in combined preparations were quantitated by using the first-derivative responses at 271.6 nm for LST and 335.0 nm for HCTZ in spectra of their solutions in water. The linearity ranges are 30-70 microg/mL for LST and 7.5-17.5 microg/mL for HCTZ with correlation coefficients of 0.9998 and 0.9997, respectively. In the HPTLC method, a mobile phase of chloroform-methanol-acetone-formic acid (7.5 + 1.5 + 0.5 + 0.03, v/v) and a prewashed Silica Gel G60 F254 TLC plate as the stationary phase were used to resolve LST and HCTZ in a mixture. Two well-separated and sharp peaks for LST and HCTZ were obtained at Rf values of 0.61+/-0.02 and 0.41+/-0.02, respectively. LST and HCTZ were quantitated at 254.0 nm. The linearity ranges obtained for the HPTLC method are 400-1200 and 100-300 ng/spot with corresponding correlation coefficients of 0.9944 and 0.9979, for LST and HCTZ, respectively. Both methods were validated, and the results were compared statistically. They were found to be accurate, specific, and reproducible. The methods were successfully applied to the estimation of LST and HCTZ in combined tablet formulations.     

Validation of a capillary electrophoresis method for the simultaneous determination of amlodipine besylate and valsartan in pharmaceuticals and human plasma

A rapid, simple, and sensitive capillary electrophoresis (CE) method was developed and validated for the simultaneous determination of amlodipine (AML) and valsartan (VAL) in pharmaceuticals and human plasma using a UV photodiode array detector. Electrophoretic conditions were optimized to improve separation, sensitivity, and rapidity. The optimal conditions were 25 mM phosphate buffer at pH 8.0, injection time 10.0 s, voltage 25 kV, and column temperature 25 degrees C, with detection at 214 nm. The method was found to be linear in the range of 1.0-35 and 1.0-350 mg/L, with weighted regression 0.9999 and 0.9994, for AML and VAL, respectively. Validation of the method showed acceptable intraday and interday accuracy (85.5-95.3%) and precision (RSD 1.64-4.2%) in pharmaceutical formulation and human plasma analysis. The sensitivity of the method was enhanced by both optimization of the CE procedure and preconcentration performed by liquid-liquid extraction. The LOD for both AML and VAL was 0.03 mg/L, which allows analysis at the level of the drugs possibly found in human plasma. Therefore, the proposed method is suitable for QC in pharmaceutical laboratories and therapeutic drug monitoring in clinical laboratories.     

HPLC�CDAD Analysis of Hydrochlorothiazide and Irbesartan in Hypertensive Patients on Fixed-Dose Combination Therapy

Hydrochlorothiazide (HCTZ) and the angiotensin II type 1 receptor antagonist (ARB) irbesartan (IRBE) are well-known antihypertensive drugs, frequently administered as a low-dose combination in a single pill. In this work, a simple, sensitive, and selective high-performance liquid chromatographic (HPLC) method with diode-array detection was developed for simultaneous determination of HCTZ and IRBE levels in the plasma of hypertensive patients given a fixed combination of 12.5 mg HCTZ and 300 mg IRBE. Compounds were extracted from acidified plasma samples with 3 mL ethyl acetate, and eluted at 6 and 19 min from a C₄ column by elution with an acetonitrile?Cphosphate buffer (pH 3.6) mobile-phase gradient at a flow rate of 1 mL min^?1. The assay was linear over the ranges 2.5?C500 and 20?C4,000 ng mL^?1 for HCTZ and IRBE, respectively. Overall intra-assay and inter-assay variation were within acceptance limits. Limits of quantification were 2.5 and 20 ng mL^?1 for HCTZ and IRBE, respectively. Plasma samples remained stable for 12 h at room temperature, through three thaw?Cfreeze cycles, and for 2 and 7 months at ?20 °C. In hypertensive patients, residual concentrations were 22.3 ± 6.0 and 241.8 ± 39.0 ng mL^?1 for HCTZ and IRBE, respectively. There was no interference from other co-administered drugs. Despite the different physicochemical properties of HCTZ and IRBE, our method enables accurate measurement of both drugs for assessment of compliance by patients treated by fixed-dose combination therapy with HCTZ?CIRBE.     

Highly sensitive determination of Schisandrin and Schisandrin B in plasma of rats after administration of Wurenchun (Fructus Schisandrae Chinensis Extracts) preparations by LC‐ESI‐MS/MS

A sensitive and specific method based on liquid chromatography‐tandem mass spectrometry using electrospray ionization (LC‐ESI‐MS/MS) has been developed for the determination of Schisandrin and Schisandrin B in rat plasma. A 100 μL plasma sample was extracted by methyl tert‐butyl ether after spiking the samples with nimodipine (internal standard) and performed on an XTerra®MS‐C₁₈ column (150 mm × 2.1 mm, 3.5 μm) with the mobile phase of acetonitrile–water–formic acid (80:20:0.2, v/v) at a flow rate of 0.2 mL/min in a run time of 8.5 min. The lower limit of quantification of the method was 40 ng/mL for Schisandrin and 20 ng/mL for Schisandrin B. The method showed reproducibility with intra‐day and inter‐day precision of less than 13.8% RSD, as well as accuracy, with inter‐ and intra‐assay accuracies between 93.5 and 107.2%. Finally, the LC‐ESI‐MS/MS method was successfully applied to study the pharmacokinetics of Schisandrin and Schisandrin B in rats after administration of Wurenchun commercial formulations to rats. Copyright © 2009 John Wiley & Sons, Ltd.     

Development and validation of UPLC‐MS/MS method for determination of domperidone in human plasma and its pharmacokinetic application

A sensitive, rapid and selective ultra‐performance liquid chromatography–tandem mass spectrometric (UPLC‐MS/MS) method was developed for the determination and pharmacokinetic study of domperidone in human plasma. Diphenhydramine was used as the internal standard. Plasma sample pretreatment involved a one‐step liquid–liquid extraction with a mixture of diethyl ether–dichloromethane (3:2, v/v). The analysis was carried out on an Acquity UPLC^TM BEH C₁₈ column. The mobile phase consisted of methanol–water containing 10 mmol/L ammonium acetate and 0.5% (v/v) formic acid (60:40, v/v). The detection was performed on a triple quadrupole tandem mass spectrometer in multiple reaction monitoring mode via electrospray ionizationsource with positive mode. Each plasma sample was chromatographed within 2.1 min. The standard curves for domperidone were linear (r² ≥ 0.99) over the concentration range of 0.030–31.5 ng/mL with a lower limit of quantification of 0.030 ng/mL. The intra‐ and inter‐day precision (relative standard deviation) values were not higher than 13% and accuracy (relative error) was from ?7.6 to 1.2% at three quality control levels. The method herein described was superior to previous methods and was successfully applied to the pharmacokinetic study of domperidone in healthy Chinese volunteers after oral administration. Copyright © 2012 John Wiley & Sons, Ltd.     

Determination of docetaxel in rat plasma and its application in the comparative pharmacokinetics of Taxotere and SID530, a novel docetaxel formulation with hydroxypropyl‐β‐cyclodextrin

In this study, a sensitive, simple and reliable method for the quantification of docetaxel in rat plasma was developed and validated using liquid chromatography–tandem mass spectrometry (LC‐MS/MS). The plasma samples were prepared by protein precipitation, and paclitaxel was used as an internal standard (IS). Chromatographic separation was achieved using a Gemini C₁₈ column (2.0 × 150 mm, 5 µm) with a mobile phase consisting of 0.1% formic acid–acetonitrile (30:70, v/v). The precursor–product ion pairs used for multiple reaction monitoring were m/z 808.5 → 527.5 (docetaxel) and m/z 854.2 → 286.5 (IS, paclitaxel). A calibration curve for docetaxel was constructed over the range 1–1000 ng/mL. The developed method was specific, precise and accurate, and no matrix effect was observed. The validated method was applied in a comparative pharmacokinetic study in which two docetaxel formulations, SID530, a new parenteral formulation of docetaxel with hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD), and Taxotere, were administered to rats at a dose of 5 mg/kg. For SID530 and Taxotere, the mean C₀ values were 1494 and 1818 ng/mL, respectively, and the AUC_last values were 837 and 755 h ng/mL, respectively. These two formulations did not show any statistical differences with regard to the pharmacokinetic parameters, thus establishing that the SID530 and Taxotere products are pharmacokinetically comparable in male rats. Copyright © 2012 John Wiley & Sons, Ltd.     

A new HPTLC densitometric method for analysis of swertiamarin in Enicostemma littorale and commercial formulations

A high-performance thin layer chromatographic densitometric method for the analysis of swertiamarin in 60% methanolic extract of Enicostemma littorale and commercial formulations has been developed and validated in this study. Swertiamarin was separated on aluminium-backed silica gel 60 F??? plates using ethyl acetate : methanol : water (77 : 15 : 8)% v/v as the mobile phase. This system was found to give a compact spot of swertiamarin at R(f) value 0.36 ± 0.01. The limit of detection and limit of quantification were found to be 31.25 and 103.12 ng spot?1, respectively. The proposed method was employed with a high degree of precision and accuracy for the estimation of swertiamarin in methanolic extract of Enicostemma littorale and in commercial formulations.     

Liquid chromatographic method for the simultaneous determination of captopril,piroxicam, and amlodipine in bulk drug,pharmaceutical formulation,and human serum by programming the detector

A highly sensitive LC method with UV detection has been developed for the simultaneous determination of coadministered drugs captopril, piroxicam, and amlodipine in bulk drug, pharmaceutical formulations, and human serum at the isosbestic point (235 nm) and at individual λ_max (220, 255, and 238 nm, respectively) by programming the detector with time to match the individual analyte's chromophore, which enhanced the sensitivity with linear range. The assay involved an isocratic elution of analytes on a Bondapak C₁₈ (10 μm, 25 × 0.46 cm) column at ambient temperature using a mobile phase of methanol/water 80:20 at pH 2.9 and a flow rate of 1.0 mL/min. Linearity was found to be 0.25–25, 0.10–6.0, and 0.20–13.0 μg/mL with correlation coefficient >0.998 and detection limits of 7.39, 3.90, and 9.38 ng/mL, respectively, whereas calibration curves for wavelength‐programmed analysis were 0.10–6.0, 0.04–2.56, and 0.10–10.0 μg/mL with correlation coefficient >0.998 and detection limits of 5.79, 2.68, and 3.87 ng/mL, respectively. All the validated parameters were in the acceptable range. The recovery of drugs was 99.32–100.39 and 98.65–101.96% in pharmaceutical formulation and human serum, respectively, at the isosbestic point and at individual λ_max. This method is applicable for the analysis of drugs in bulk drug, tablets, serum, and in clinical samples without interference of excipients or endogenous serum components.     

A validated LC‐MS/MS assay for the quantitative determination of curdione in rabbit plasma and its application to a pharmacokinetic study after administration of zedoary turmeric oil and bioavailability of the oil

A selective and sensitive liquid chromatography tandem mass spectrometry method was developed for the first time for the identification and quantification of curdione in rabbit plasma after vaginal drug administration and intravenous administration of zedoary turmeric oil (ZTO) solution (10 mg/kg). The analysis was performed on a triple‐quadrupole tandem mass spectrometer with multiple reaction monitoring mode via electrospray ionization source in positive ionization mode. After mixing with internal standard diazepam, plasma samples were extracted with ethyl ether–acetic ether (1:1, v/v). Chromatographic separation was carried out on a C₁₈ column with gradient elution using a mixture of water and acetonitrile (both containing 0.1% formic acid) as mobile phases. Linearity ranged over 1.06–106 and 10.6–530 ng/mL (r ≥ 0.995) with the lower limit of quantfication 1.06 ng/mL. The intra‐ and inter‐day precision relative standard deviation values were <12% and the accuracy relative error was from ?10.6 to ?6.1% at all quality control sample levels. The method was applied to a study of the pharmacokinetics of curdione after vaginal drug administration and intravenous administration of ZTO. Copyright © 2014 John Wiley & Sons, Ltd.