Determination of moxonidine in human plasma by liquid chromatography–electrospray ionisation–mass spectrometry

Mass Spectrometry as a Complementary Approach for Noncovalently Bound Complexes Based on Cyclodextrins

An important and well-designed solution to overcome some of the problems associated with new drugs is provided by the molecular encapsulation of the drugs in the cyclodextrins (CDs) cavity, yielding corresponding inclusion complexes (ICs). These types of non-covalent complexes are of current interest to the pharmaceutical industry, as they improve the solubility, stability and bioavailability of the guest molecules. This review highlights several methods for cyclodextrin ICs preparation and characterization, focusing mostly on the mass spectrometry (MS) studies that have been used for the detection of noncovalent interactions of CDs inclusion complexes and binding selectivity of guest molecules with CDs. Furthermore, the MS investigations of several ICs of the CD with antifungal, antioxidants or fluorescent dyes are presented in greater details, pointing out the difficulties overcome in the analysis of this type of compounds.

Sensitive and rapid LC–ESI-MS method for the determination of trimetazidine in human plasma

A sensitive method, based on liquid chromatography-electrospray ionisation-mass spectrometry (LC-ESI-MS), was developed for the determination of trimetazidine in human plasma. Buflomedil was used as the internal standard (IS). Plasma samples were extracted with a mixture of cyclohexane-diethyl ether (1:1, v/v) and the analytes were chromatographically separated on a phenomenex Luna 5 mu C18 (2) 100A HPLC column with a mobile phase of 10 mM ammonium acetate buffer solution containing 0.1% acetic acid-methanol (45:55, v/v). The electrospray ionization was employed in a single quadrupole mass spectrometer for the analytical determination. The lower limit of quantification (LLOQ) was 0.5 ng/ml for trimetazidine and the measuring ranges were from 0.5 to 200 ng/ml. The intra- and inter-run standard deviation was less than 4.1% and 7.8%, respectively. The method was successfully applied to study the pharmacokinetics of trimetazidine in healthy Chinese volunteers.

Determination of palonosetron in human plasma by liquid chromatography–electrospray ionization-mass spectrometry

A high performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS) method for the determination of palonosetron (PALO) in human plasma using naloxone as the internal standard (IS) was established. After adjustment to a weakly basic pH with saturated sodium bicarbonate, plasma samples were extracted with ethyl acetate and separated on a Hanbon Lichrospher 5-C18 column with a mobile phase of 40 mM ammonium acetate buffer solution containing 0.04% formic acid-methanol (46:54, v/v). PALO was determined with electrospray ionization-mass spectrometry (ESI-MS). HPLC-ESI-MS was performed in the selected-ion monitoring (SIM) mode using target ions at [M+H]+ m/z 297.2 for PALO and [M+H]+ m/z 328.2 for the IS. Calibration curve was linear over the range of 0.02124-10.62 ng/ml. The lower limit of quantification (LLOQ) was 0.02124 ng/ml. The intra- and inter-run variability values were all less than 10.4%. The method has been successfully applied to determine the plasma concentration of PALO in healthy Chinese volunteers.

In vivo pharmacokinetic and metabolism studies of ginsenoside Rd

A high-performance liquid chromatography-electrospray ionisation-tandem mass spectrometry (LC-ESI-MS(n)) method has been developed to determine ginsenoside Rd in human plasma and to identify its metabolites in rat urine. The plasma and urine samples were pretreated by solid phase extraction (SPE) prior to analyses. In this work, gentiopicroside was used as the internal standard. The lower limit of quantification (LLOQ) for Rd in human plasma was 3 ng/ml. The average half-life time in plasma was detected as 19.29 h, when 10 mg of ginsenoside Rd was administrated intravenously to the volunteers. Seven metabolites including three oxygenated, two combined and two hydrolyzed components were identified in rat urine samples by using LC-MS and MS-MS, when ginsenoside Rd administered either orally or intravenously.

Determination of berberine in human plasma by liquid chromatography-electrospray ionization-mass spectrometry

A liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) method for the determination of berberine in human plasma using chlorobenzylidine as the internal standard (IS) has been developed and validated. The plasma samples were prepared by LLE and the analytes were chromatographically separated on a Hanbon Lichrospher 5-C18 HPLC column under gradient elution with a mobile phase consisted of acetonitrile and 10mm ammonium acetate buffer containing 0.1% formic acid. Berberine was determined with electrospray ionisation-mass spectrometry (ESI-MS). LC-ESI-MS was performed in the selected-ion monitoring (SIM) mode using target ions at M(+)m/z 336.1 for berberine and M(+)m/z 464.1 for the IS. Calibration curve was linear over the range of 0.020-3.0 ng/ml. The lower limit of quantification (LLOQ) was 0.020 ng/ml. The intra- and inter-run variability values were less than 6.7 and 7.7%, respectively. The method has been successfully applied to determine the plasma concentration of berberine in healthy Chinese volunteers.

LC-ESI-MS method for the determination of bisoprolol in human plasma

A sensitive liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) method has been developed and validated for the determination of bisoprolol in human plasma, using metoprolol as internal standard (I.S.). After alkalization with sodium hydroxide, the samples were extracted with ethyl acetate and separated by HPLC on a ZORBAX SB-C18 column with a mobile phase of 10 mM ammonium acetate buffer containing 0.1% formic acid-methanol (32:68, v/v) at a flow rate of 1 ml/min. The chromatographic separation was achieved in less than 5 min. The linearity was established over the concentration range of 0.05-120 ng/ml. The intra- and inter-run standard deviation was less than 3.8 and 7.5%, respectively. The method had been successfully applied to study the relative bioavailability of bisoprolol fumarate tablets in healthy Chinese volunteers. The pharmacokinetic parameters of the reference and test tablets have been compared.

Sensitive and convenient method for the quantification of clonidine in serum of pediatric patients using liquid chromatography/tandem mass spectrometry

An improved and easy to use liquid chromatography/tandem mass spectrometric (LC/MS/MS) method in human serum was developed for the quantification of clonidine (CLD), an alpha2-/alpha1-adrenoceptor agonist, used for analgo-sedation and the therapy of opioid withdrawal in pediatric patients. Sample preparation consisted of precipitation of serum proteins by adding acetonitrile and centrifugation of the sample subsequently. [(2)H4]Clonidine (CLD4) served as internal standard. Chromatographic separation of the supernatant was achieved using a 100mmx3mm, 5microm Thermo Electron BetaBasic C4 column with isocratic flow and elution consisting of 0.1% formic acid/acetonitrile (85/15, v/v) and a flow-rate of 350microl/min resulting in a column pressure of 280-420kPa. LC/MS/MS detection was performed by using a triple-stage quadrupole mass spectrometer (TSQ Quantum, Thermo Electron) working in selected reaction monitoring mode with positive electrospray ionization. The analyte was quantified in a single run within 5min. Linearity was demonstrated over the expected concentration range 0.15-50microg/l CLD. The lower limit of quantification (LLOQ) and the limit of detection were 0.1microg/l and 0.01microg/l, respectively. None of the drugs used concomitantly during analgesic therapy interfered in the assay in vitro. Intra-day precision expressed as RSD was 9.6% or less for CLD, while inter-day result was 10.0% or less for CLD. Intra-day and inter-day accuracy was within +/-4.9% and +/-1.8%, respectively. The method was validated according to the international guidelines of the International Conference on Harmonisation (ICH) and the US Food and Drugs Administration (FDA). The described method is suitable to analyse serum samples with very small volumes and sets the stage for pharmacokinetic studies in pediatric studies.

On-line coupling of dynamic microwave-assisted extraction with high-performance liquid chromatography for determination of andrographolide and dehydroandrographolide in Andrographis paniculata Nees

A novel technique based on dynamic microwave-assisted extraction (DMAE) coupled on-line with high-performance liquid chromatography (HPLC) through a flow injection interface has been developed for determination of andrographolide and dehydroandrographolide in Andrographis paniculata Nees. A TM(010) microwave resonance cavity built in the laboratory was applied to concentrating the microwave energy. An extraction vessel was placed in microwave irradiation zone. The extraction was performed in a recirculating system. When a number of extraction cycles were completed, the fractional extract (20muL) was driven to the analytical column by 65% aqueous methanol and was measured by diode array detector (DAD) at 225nm. The optimized extraction conditions are follows: extraction solvent 60% aqueous methanol; microwave forward power 80W; extraction time 6min; extraction solvent flow-rate 1.0mLmin(-1). The detection and quantification limits obtained are 0.5 and 1.7microgmL(-1) for andrographolide and 0.6 and 1.9microgmL(-1) for dehydroandrographolide, respectively. The within-day and between-day precision (RSD) are 2.1% and 3.7% for andrographolide and 1.7% and 4.1% for dehydroandrographolide, respectively. Mean recoveries for andrographolide and dehydroandrographolide are 97.7% and 98.7%, respectively. Compared with ultrasonic extraction used in the Chinese pharmacopoeia, the proposed method was demonstrated to obtain higher extraction yield in a shorter time. In addition, only small quantities of solvent (5mL) and sample (10mg) were required.