Quantitative HPLC method and pharmacokinetic studies of ergosta‐4,6,8(14),22‐tetraen‐3‐one,a natural product with diuretic activity from Polyporus umbellatus

A simple and specific HPLC method with dual wavelength UV detection for the determination of ergosta‐4,6,8(14),22‐tetraen‐3‐one (ergone) in rat plasma was developed and proved to be efficient. The method used ergosterol as internal standard (IS). Following a single‐step protein precipitation, the analyte and IS were separated on an Inertsil ODS‐3 column with a mobile phase containing methanol–water (99:1, v/v) at a flow rate of 1 mL/min. The analytes were detected by using UV detection at wavelength of 350 (ergone) and 283 (IS) nm, respectively. The calibration curve was linear over the range of 0.1–2.0 µg/mL and the lower limit of quantification was 0.1 µg/mL. The intra‐day and inter‐day precision studies showed good reproducibility with RSD less than 8.5%. The intra‐day and inter‐day accuracy ranged from 95.6 to 104%. Mean extraction recovery was above 95% at the low, medium and high concentrations. The present HPLC‐UV method was simple and reliable. The method described herein had been successfully applied for the pharmacokinetic studies in male SD rats after administration of 20 mg/kg dose of solution of ergone. Copyright © 2010 John Wiley & Sons, Ltd.     

Determination of a novel paclitaxel derivative (NPD‐103) in human plasma by ultra‐performance liquid chromatography–tandem mass spectrometry

A sensitive and specific ultra‐performance liquid chromatography–tandem mass spectrometry (UPLC‐MS‐MS) method for quantification of a newly developed anticancer agent NPD‐103 has been established. An aliquot of human plasma sample (200 µL) was spiked with ¹³C‐labeled paclitaxel (internal standard) and extracted with 1.3 mL of tert‐butyl methyl ether. NPD‐103 was quantitated on a C₁₈ column with methanol–0.1% formic acid (75:25, v/v) as mobile phase using UPLC‐MS‐MS operating in positive electrospray ionization mode with a total run time of 3.0 min. For NPD‐103 at the concentrations of 1.0, 5.0 and 10.0 µg/mL in human plasma, the absolute extraction recoveries were 95.58, 102.43 and 97.77%, respectively. The linear quantification range of the method was 0.1–20.0 µg/mL in human plasma with linear correlation coefficients greater than 0.999. The intra‐ and inter‐day accuracy for NPD‐103 at 1.0, 5.0 and 10.0 µg/mL levels in human plasma fell into the ranges of 95.29–100.00% and 91.04–94.21%, and the intra‐ and inter‐day precisions were in the ranges of 8.96–11.79% and 7.25–10.63%, respectively. This assay is applied to determination of half‐life of NPD‐103 in human plasma. Copyright © 2008 John Wiley & Sons, Ltd.     

Quantification and validation of HPLC‐UV and LC‐MS assays for therapeutic drug monitoring of ertapenem in human plasma

Rapid and simple HPLC‐UV and LC‐MS methods were developed and validated for the quantification of ertapenem (Invanz?) in human plasma. Ertapenem is a unique drug in that current dosing recommendations call for a 1 g dose for normal renal function patients, despite body weight. These assays, which involve a protein precipitation followed by liquid–liquid extraction, allow for fast therapeutic drug monitoring of ertapenem in patients, which is especially useful in special populations. Both methods were sufficient to baseline resolve meropenem (internal standard) and ertapenem, and were validated over 3 days using a six‐point calibration curve (0.5–50 µg/mL). Validation was collected using four different points on the calibrations curve yielding acceptable precision (<15% inter‐day and intra‐day; <20% for lower limit of quantitation, LLOQ) as well as accuracy (<15% inter‐day and intra‐day; <20% for LLOQ). The lower limit of detection (LOD) was determined to be 0.1 and 0.05 µg/mL for the HPLC‐UV and LC‐MS methods, respectively. The developed HPLC‐UV and LC‐MS methods for ertapenem quantification are fast, accurate and reproducible over the calibration range and can be used to determine ertapenem plasma concentrations for monitoring clinical efficacy. Copyright © 2012 John Wiley & Sons, Ltd.     

Evaluation of matrix solid‐phase dispersion extraction for 11 β‐agonists in swine feed by liquid chromatography with electrospray ionization tandem mass spectrometry

A sensitive liquid chromatography with tandem mass spectrometry method was developed for the determination of 11 β‐agonists (clenbuterol, salbutamol, ractopamine, terbutaline, fenoterol, cimaterol, isoxsuprine, mabuterol, mapenterol, clenproperol, and tulobuterol) in swine feed. This rapid, simple, and effective extraction method was based on matrix solid‐phase dispersion. The limit of quantification of clenbuterol, cimaterol, mabuterol, salbutamol, terbutaline, mapenterol, clenproperol, and tulobuterol was 1 μg/kg and that of ractopamine, fenoterol, and isoxsuprine was 2 μg/kg. The recoveries of β‐agonists spiked in swine feeds at a concentration range of 1–8 μg/kg were >83.1% with relative standard deviations <9.3%. This rapid and reliable method can be used to efficiently separate, characterize, and quantify the residues of 11 β‐agonists in swine feeds with advantages of simple pretreatment and environmental friendliness.     

Investigation of ractopamine‐imprinted polymer for dispersive solid‐phase extraction of trace β‐agonists in pig tissues

Ractopamine, as an alternative β‐agonist to clenbuterol, is more and more used as leanness‐enhancing agent in the swine industry. This work presents a new molecularly imprinted polymer (MIP) using ractopamine as template for dispersive solid‐phase extraction of trace ractopamine and the structural related β‐agonists in animal tissues. The binding properties and selectivity of MIP were investigated. High selectivity in polar environment was found, since the extraction capacity of ractopamine with the MIP was 4.5‐fold as much as that with the non‐imprinted polymer in acetonitrile. Cross‐selectivity investigation indicates that the MIP preferentially binds the template and then the structural analogues according to their molecular similarity. Thermodynamic and kinetic investigation was performed to interpret the specific adsorption and molecular recognition of the MIP for ractopamine. Standard free energy, standard enthalpy, and standard entropy were determined. Related information suggested that adsorption of ractopamine onto MIP was an exothermic, spontaneous process. The MIP can be applied as dispersive solid‐phase extraction material for enrichment of ractopamine, isoxsuprine, fenoterol and clenbuterol in complex samples before HPLC analysis. The method revealed detection limits of 0.20–0.90 μg/L, recoveries of 83.8–115.2 and 85.2–110.2% for the spiked pig muscle and pig liver, respectively, with the RSD from 2.5 to 8.8%.     

Developing a novel packed in‐tube solid‐phase extraction method for determination ∆9‐tetrahydrocannabinol in biological samples and cannabis leaves

A novel plate‐like nano‐sorbent based on copper/cobalt/chromium layered double hydroxide was synthesized by a simple coprecipitation method. The synthesized nanoparticels were introduced into a stainless steel cartridge using a dry packing method. Then, the packed cartridge was introduced as a novel on‐line “packed in‐tube” configuration and followed by high performance liquid chromatography for the determination of trace amounts of ^?9‐tetrahydrocannabinol from biological samples and cannabis leaves. The as‐prepared sorbent exhibited long lifetime, good chemical stability, and high anion‐exchange capacity. Several important factors affecting the extraction efficiency, such as extraction and desorption times, pH of the sample solution and flow rates of the sample and eluent solutions, were investigated and optimized. Under optimized conditions, this method showed good linearity for ^?9‐tetrahydrocannabinol in the ranges of 0.09–500, 0.3–500, and 0.4–500 µg/L with coefficients of determination of 0.9999, 0.9991, and 0.9994 in water, serum and plasma samples, respectively. The inter‐ and intra‐assay precisions (n = 3) were respectively in the ranges of 1.8–4.6% and 1.9–4.0% at three concentration levels of 10, 50, and 100 µg/L. The limits of detection were also in the range of 0.02–0.1 µg/L.     

Two‐phase and three‐phase liquid‐phase microextraction of hydrochlorothiazide and triamterene in urine samples

This paper reports the applicability of two‐phase and three‐phase hollow fiber based liquid‐phase microextraction (HF‐LPME) for the extraction of hydrochlorothiazide (HYD) and triamterene (TRM) from human urine. The HYD in two‐phase HF‐LPME is extracted from 24 mL of the aqueous sample into an organic phase with microliter volume located inside the pores and lumen of a polypropylene hollow fiber as acceptor phase, but the TRM in three‐phase HF‐LPME is extracted from aqueous donor phase to organic phase and then back‐extracted to the aqueous acceptor phase, which can be directly injected into HPLC for analysis. Under optimized conditions preconcentration factors of HYD and TRM were obtained as 128 and 239, respectively. The calibration curves were linear (R² ≥ 0.995) in the concentration range of 1.0–100 µg/L for HYD and 2.0–100 µg/L for TRM. The limits of detection for HYD and TRM were 0.5 µg/L. The intra‐day and inter‐day RSD based on four replicates were obtained as ≤5.8 and ≤9.3%, respectively. The methods were successfully applied for determining the concentration of the drugs in urine samples. Copyright © 2015 John Wiley & Sons, Ltd.     

Simultaneous determination of β2‐agonists in human urine by fast‐gas chromatography/mass spectrometry: method validation and clinical application

A fast screening protocol was developed and validated for the simultaneous determination of 15 β₂‐agonists in human urine (bambuterol, cimbuterol, clenbuterol, fenoterol, formoterol, isoproterenol, mapenterol, metaproterenol, procaterol, ractopamine, ritodrine, salbutamol, salmeterol, terbutaline, tulobuterol). The overall sample processing includes deconjugation with enzyme hydrolysis, liquid–liquid extraction, followed by derivatization of the extract and detection of β₂‐agonists trimethylsilyl‐derivatives by fast‐gas chromatography/electron impact–mass spectrometry (fast‐GC/EI‐MS). Sample extraction and derivatization were optimized with the purpose of improving recoveries and reaction yields for a variety of analytes with different structures simultaneously, while keeping the procedure simple and reliable. Validation parameters were determined for each analyte under investigation, including selectivity, linearity, intra‐ and inter‐assay precision, extraction recoveries and signal to noise ratio (S/N) at the lowest calibration level. Fast‐GC/MS sequences, based on the use of short columns, high carrier‐gas velocity and fast temperature ramping, allow considerable reduction of the analysis time (7 min), while maintaining adequate chromatographic resolution. The overall GC cycle time was less than 9 min, allowing a processing rate of 6 samples/h. High MS‐sampling rate, using a benchtop quadrupole mass analyzer, resulted in accurate peak shape definition under both scan and selected ion monitoring modes, and high sensitivity in the latter mode. The method was successfully tested on real samples arising from clinical treatments. Copyright © 2009 John Wiley & Sons, Ltd.     

Combined derivatization and high‐performance liquid chromatography with fluorescence and ultraviolet detection for simultaneous analysis of octreotide and gabexate mesylate metabolite in human pancreatic juice samples

A simple and sensitive method based on the combination of derivatization and high‐performance liquid chromatography with ultraviolet and fluorimetric detection was developed for the simultaneous determination of octreotide and gabexate mesylate metabolite in human pancreatic juice samples. Parameters of the derivatization procedure affecting extraction efficiency were optimized. The developed method was validated according to the International Conference on Harmonization guidelines. The calibration curves were linear over a range of 0.1–15 µg/mL for octreotide and 0.20‐15 µg/mL for gabexate mesylate metabolite. Derivatized products of octreotide and gabexate mesylate metabolite were separated on a Luna C₁₈ column (4.6 × 250 mm; 5 µm particle size) using a gradient with a run time of 36 min, without further purification. The limits of detection were 0.025 and 0.05, respectively, for octreotide and gabexate mesylate metabolite. This paper reports the validation of a quantitative high performance liquid chromatography–photodiode array–fluorescence (HPLC‐PDA‐FL) method for the simultaneous analysis of octreotide and gabexate mesylate metabolite in pancreatic juice by protein precipitation using zinc sulfate–methanol–acetonitrile containing the derivatizing reagent, 4‐fluoro‐7‐nitro‐[2,1,3]‐benzoxadiazole (NBD‐F). Derivatized products of octreotide and gabexate mesylate metabolite were separated on a Luna C₁₈ column (4.6 × 250 mm; 5 µm particle size) using a gradient with a run time of 36 min, without further purification. The method was validated over the concentration ranges 0.1–15 and 0.2–15 µg/mL for octreotide and gabexate mesylate metabolite, respectively, in human pancreatic juice. Biphalin and methyl‐p‐hydroxybenzoate were used as the internal standards. This method was successfully utilized to support clinical studies in humans. The results from assay validations show that the method is selective, sensitive and robust. The limit of quantification of the method was 0.1 µg/mL for octreotide and 0.2 µg/mL for gabexate mesylate metabolite, and matrix matched standard curves showed a good linearity up to 15 µg/mL. In the entire analytical range the intra‐ and inter‐day precision (RSD%) values were respectively ≤5.9% and ≤3.1% for octreotide and ≤2.0% and ≤3.9% for gabexate mesylate metabolite. For both analytes the intra‐ and inter‐day accuracy (bias) values ranged respectively from ?6.8 to –2.5% and from ?4.6 to ?5.7%. This method utilizes derivatization with NBD‐F and provides adequate sensitivity for both drugs. Copyright © 2014 John Wiley & Sons, Ltd.     

Qualitative and quantitative analysis of THC, 11‐hydroxy‐THC and 11‐nor‐9‐carboxy‐THC in whole blood by ultra‐performance liquid chromatography/tandem mass spectrometry

A qualitative and quantitative analytical method was developed for the simultaneous determination of Δ⁹‐tetrahydrocannabinol (THC), 11‐hydroxy‐Δ⁹‐tetrahydrocannabinol (11‐OH‐THC) and l1‐nor‐9‐carboxy‐Δ⁹‐tetrahydrocannabinol (THC‐COOH) in whole blood. The samples were prepared by solid‐phase extraction followed by ultra‐performance liquid chromatography/tandem mass spectrometry (UPLC/MS/MS) analysis using positive ion electrospray ionization and multiple reaction monitoring. The chromatographic separation was performed with an Acquity UPLC® HSS T3 (50 × 2.1 mm i.d., 1.8 µm) reversed‐phase column using a methanol/2 mM ammonium formate (formic acid 0.1%) gradient in a total run time of 9.5 min. MS/MS detection was achieved with two precursor‐product ion transitions per substance. The method was fully validated, including selectivity and capacity of identification, according to the identification criteria (two transitions per substance, signal‐to‐noise ratio, relative retention time and ion ratio) without the presence of interferences, limit of detection (0.2 µg/L for THC and 0.5 µg/L for 11‐OH‐THC and THC‐COOH), limit of quantitation (0.5 µg/L for all cannabinoids), recovery (53–115%), carryover, matrix effect (34‐43%), linearity (0.5‐100 µg/L), intra‐assay precision (CV < 10% for the relative peak area ratios and <0.1% for the relative retention time), inter‐assay accuracy (mean relative error <10%) and precision (CV <11%). The method has already been successfully used in proficiency tests and subsequently applied to authentic samples in routine forensic analysis. Copyright © 2011 John Wiley & Sons, Ltd.     

Determination of trans,trans‐muconic acid in workers' urine through ultra‐performance liquid chromatography coupled to tandem mass spectrometry

A novel method for the biological monitoring of benzene‐exposed workers has been developed through ultra‐performance liquid chromatography coupled to tandem mass spectrometry. The method uses trans,trans‐muconic acid in urine as the benzene‐exposure biomarker. The method was developed using a triple quadrupole mass spectrometer with enough sensitivity to facilitate diluting and injecting the urine samples directly, rather than performing a solid‐phase extraction procedure as is common in the available protocols. Moreover, compared with a conventional high‐pressure liquid chromatography system, the separation power provided by the ultra‐performance liquid chromatography system allows a 10‐fold reduction in run time. The method was adjusted to a dynamic range of between 198.9 and 4916.7 µg/L to cover the biological exposure index of trans,trans‐muconic acid in urine. Also, the method demonstrated intra‐day and inter‐day precision at 98%, and accuracy within an acceptable range of 101 ± 8%. The method has been used to quantify various types of urine samples, such as workers' urine and inter‐laboratory proficiency tests. Depending on the sample, the quantified levels ranged from less than the limit of quantitation to 3836.7 µg/L. No levels exceeding the calibration range were detected in the urine of workers, and the reported concentrations in urine for the proficiency tests were, as expected, based on known values. Moreover, the new method using sample dilution and faster chromatographic run was more effective, facilitating fast communication of results, as needed, to decision‐makers. Copyright © 2012 John Wiley & Sons, Ltd.     

Rapid analysis of three β‐agonist residues in food of animal origin by automated on‐line solid‐phase extraction coupled to liquid chromatography and tandem mass spectrometry

An automated online solid‐phase extraction with liquid chromatography and tandem mass spectrometry method was developed and validated for the detection of clenbuterol, salbutamol, and ractopamine in food of animal origin. The samples from the food matrix were pretreated with an online solid‐phase extraction cartridge by Oasis MCX for <5 min after acid hydrolysis for 30 min. The peak focusing mode was used to elute the target compounds directly onto a C₁₈ column. Chromatographic separation was achieved under gradient conditions using a mobile phase composed of acetonitrile/0.1% formic acid in aqueous solution. Each analyte was detected in two multiple reaction monitoring transitions via an electrospray ionization source in a positive mode. The relative standard deviations ranged from 2.6 to 10.5%, and recovery was between 76.7 and 107.2% at all quality control levels. The limits of quantification of three β‐agonists were in the range of 0.024–0.29 μg/kg in pork, sausage, and milk powder, respectively. This newly developed method offers high sensitivity and minimum sample pretreatment for the high‐throughput analysis of β‐agonist residues.     

A validated HPLC‐PDA method for identification and quantification of two bioactive alkaloids,ephedrine and cryptolepine,in different Sida species

A simple, rapid, accurate and reproducible reverse‐phase HPLC method has been developed for the identification and quantification of two alkaloids ephedrine and cryptolepine in different extracts of Sida species using photodiode array detection. Baseline separation of the two alkaloids was achieved on a Waters RP‐18 X‐terra column (250 × 4.6 mm, 5 µm) using a solvent system consisting of a mixture of water containing 0.1% Trifluoroacetic acid (TFA) and acetonitrile in a gradient elution mode with detection at 210 and 280 nm for ephedrine and cryptolepine, respectively. The calibration curves were linear in a concentration range of 10–250 µg/mL for both the alkaloids with correlation coefficient values >0.99. The limits of detection and quantification for ephedrine and cryptolepine were 5 and 10 µg/mL and 2.5 and 5 µg/mL, respectively. Relative standard deviation values for intra‐day and inter‐day precision were 1.22 and 1.04% for ephedrine and 1.71 and 2.06% for cryptolepine, respectively. Analytical recovery ranged from 92.46 to 103.95%. The developed HPLC method was applied to identify and quantify ephedrine and cryptolepine in different extracts of Sida species. Copyright © 2013 John Wiley & Sons, Ltd.     

Novel method for the rapid and specific extraction of multiple β2‐agonist residues in food by tailor‐made Monolith‐MIPs extraction disks and detection by gas chromatography with mass spectrometry

A quick and specific pretreatment method based on a series of extraction clean‐up disks, consisting of molecularly imprinted polymer monoliths and C₁₈ adsorbent, was developed for the specific enrichment of salbutamol and clenbuterol residues in food. The molecularly imprinted monolithic polymer disk was synthesized using salbutamol as a template through a one‐step synthesis process. It can simultaneously and specifically recognize salbutamol and clenbuterol. The monolithic polymer disk and series of C₁₈ disks were assembled with a syringe to form a set of tailor‐made devices for the extraction of target molecules. In a single run, salbutamol and clenbuterol can be specifically extracted, cleaned, and eluted by methanol/acetic acid/H₂O. The target molecules, after a silylation derivatization reaction were detected by gas chromatography‐mass spectrometry. The parameters including solvent desorption, sample pH, and the cycles of reloading were investigated and discussed. Under the optimized extraction and clean‐up conditions, the limits of detection and quantitation were determined as 0.018–0.022 and 0.042–0.049 ng/g for salbutamol and clenbuterol, respectively. The assay described was convenient, rapid, and specific; thereby potentially efficient in the high‐throughput analysis of β₂‐agonists residues in real food samples.     

A reliable method of liquid chromatography for the quantification of acetaminophen and identification of its toxic metabolite N-acetyl-p-benzoquinoneimine for application in pediatric studies

The aim of the present study was to develop a simple, selective and reliable method to quantify acetaminophen and its toxic metabolite N‐acetyl‐p‐benzoquinoneimine (NAPQI) for pediatric studies using 100 µL plasma samples, by reverse‐phase HPLC and UV detection. The assay was performed using a C₁₈ column and an isocratic elution with water–methanol–formic acid (70:30:0.15; v/v/v) as mobile phase. Linearity of the method was assayed in the range of 1–30 µg/mL for acetaminophen and 10–200 µg/mL for NAPQI, with a correlation coefficient r = 0.999 for both compounds, and inter‐ and intra‐day coefficients of variation of less than 13%. Several commonly co‐administered drugs were analyzed for selectivity and no interference with the determinations was observed. The detection and quantification limits for acetaminophen and NAPQI were 0.1 and 1 µg/mL, and 0.1 and 10 µg/mL respectively. The present method can be used to monitor acetaminophen levels using 100 µL plasma samples, which may be helpful when very small samples need to be analyzed, as in pharmacokinetics determination or drug monitoring in plasma in children. This assay is also able to detect the NAPQI for drug monitoring in patients diagnosed with acetaminophen intoxication. Copyright © 2010 John Wiley & Sons, Ltd.     

Development and validation of an ultra‐performance liquid chromatography method for simultaneous analysis of 20 antihistaminics in dietary supplements

The purpose of this study was to develop and validate an ultra‐performance liquid chromatography method for simultaneous analysis of 20 antihistamines (illegal additives) in dietary supplements. The limits of detection and quantitation of the method ranged from 1.5 to 2.5 µg/mL and from 20.0 to 50.0 µg/mL, respectively. The determination coefficient was >0.999, precisions were 0.2–5.1% (intra‐day) and 0.1–8.8% (inter‐day), and accuracies were 84.5–111.2% (intra‐day) and 91.9–112.0% (inter‐day). The mean recoveries of 20 targeted compounds from dietary supplements ranged from 75.4 to 119.3%. The relative standard deviations were <6.6% and complied with established international guidelines. The relative standard deviation of stability was <0.8%. Fifty‐two commercially available dietary supplements were evaluated using this method, and were found to have none of the 20 antihistamines in significant abundance. Copyright © 2014 John Wiley & Sons, Ltd.     

A rapid and simple RP‐HPLC method for quantification of kirenol in rat plasma after oral administration and its application to pharmacokinetic study

A rapid and simple reverse‐phase high‐performance liquid chromatography (RP‐HPLC) was developed and validated for the quantification of kirenol in rat plasma after oral administration. Kirenol and darutoside (internal standard, IS) were extracted from rat plasma using Cleanert™ C₁₈ solid‐phase extraction (SPE) cartridge. Analysis of the extraction was performed on a Thermo ODS‐2 Hypersil C₁₈ reversed‐phase column with a gradient eluent composed of acetonitrile and 0.1% phosphoric acid. The flow rate was 1.0 mL/min and the detection wavelength was set at 215 nm. The calibration curve was linear over the range of 9.756–133.333 µg/mL (r² = 0.9991) in rat plasma. The lower limits of detection and quantification were 2.857 and 9.756 µg/mL, respectively. The intra‐ and inter‐day precisions (relative standard deviation, RSD) were between 2.24 and 4.46%, with accuracies ranging from 91.80 to 102.74%. The extraction recovery ranged from 98.16 to 107.62% with RSD less than 4.81%. Stability studies showed that kirenol was stable in preparation and analytical process. The present method was successfully applied to the pharmacokinetic study of kirenol in male Sprague–Dawley rats after oral administration at a dose of 50 mg/kg. Copyright © 2010 John Wiley & Sons, Ltd.     

A simple and sensitive HPLC-UV method for the determination of ponicidin in rat plasma and its application in a pharmacokinetic study

A simple, rapid, selective and sensitive HPLC‐UV method has been developed and validated for the determination of ponicidin in rat plasma. The analyte was extracted from rat plasma by liquid–liquid extraction with ethyl acetate as the extraction solvent. The LC separation was performed on a Zorbax Eclipse XDB C₁₈ analytical column (150 × 4.6 mm i.d., 5 µm) with an isocratic mobile phase consisting of methanol–water–phosphoric acid (45:55:0.01, v/v/v) at a flow rate of 1.0 mL/min. There was a good linearity over the range of 0.1–25 µg/mL (r = 0.9995) with a weighted (1/C²) least square method. The lower limit of quantification was proved to be 0.1 µg/mL. The accuracy was within ±10.0% in terms of relative error and the intra‐ and inter‐day precisions were less than 9.1% in terms of relative standard deviation. After validation, the method was successfully applied to characterize the pharmacokinetics of ponicidin in rats. Copyright © 2010 John Wiley & Sons, Ltd.     

Pharmacokinetic and tissue distribution of paclitaxel in rabbits assayed by LC‐UV after intravenous administration of its novel liposomal formulation

A simple, rapid and sensitive LC‐UV method was developed and validated for the determination of paclitaxel (PTX) in rabbit plasma and tissues. A 2 mL aliquot of acetonitrile and 10 μL ammonium acetate (pH 5.0, 6 m ) as extraction agents were used to markedly increase the extraction recoveries and greatly reduce the endogenous substances. The separation was achieved on a C₁₈ column at 30 °C using an acetonitrile–ammonium acetate buffer (pH 5.0, 0.02 m ; 55:45, v/v) at a flow rate of 1.0 mL/min; UV detection was used at 227 nm. Good linearity was obtained between 0.025 and 10,000 µg/mL for plasma and between 0.025–200,000 µg/g for tissue samples (r > 0.999). The limit of detection was 6 ng/mL in plasma, 8 ng/g in heart and 12.5 ng/g in other tissues. The limit of quantitation was 25 ng/mL in plasma and heart, 125 ng/g in other tissues. The intra‐ and inter‐day assays of precision and accuracy for all bio‐samples ranged from 1.38 to 9.60% and from 83.6 to 114.5%, respectively. The extraction recoveries ranged from 70.1 to 109.5%. Samples were stable during three freeze–thaw cycles or stored in a freezer at ?20 °C for 30 days. The assay method was successfully applied to a study of the pharmacokinetics and tissue distribution of novel PTX lung targeting liposomes. Copyright © 2013 John Wiley & Sons, Ltd.