Determination of nifedipine in human plasma by flow-injection tandem mass spectrometry

Automation of mass spectrometric detection of analytes and related workflows: A review

The developments in mass spectrometry (MS) in the past few decades reveal the power and versatility of this technology. MS methods are utilized in routine analyses as well as research activities involving a broad range of analytes (elements and molecules) and countless matrices. However, manual MS analysis is gradually becoming a thing of the past. In this article, the available MS automation strategies are critically evaluated. Automation of analytical workflows culminating with MS detection encompasses involvement of automated operations in any of the steps related to sample handling/treatment before MS detection, sample introduction, MS data acquisition, and MS data processing. Automated MS workflows help to overcome the intrinsic limitations of MS methodology regarding reproducibility, throughput, and the expertise required to operate MS instruments. Such workflows often comprise automated off-line and on-line steps such as sampling, extraction, derivatization, and separation. The most common instrumental tools include autosamplers, multi-axis robots, flow injection systems, and lab-on-a-chip. Prototyping customized automated MS systems is a way to introduce non-standard automated features to MS workflows. The review highlights the enabling role of automated MS procedures in various sectors of academic research and industry. Examples include applications of automated MS workflows in bioscience, environmental studies, and exploration of the outer space.

The determination of gemini surfactants used as gene delivery agents in cellular matrix using validated tandem mass spectrometric method

A simple, reliable flow injection analysis (FIA)-tandem mass spectrometric (MS/MS) method was developed for the determination of gemini surfactants, designated as 16-3-16, 16(Py)-S-2-S-(Py)16 and 16-7N(GK)-16, as gene delivery agents in cellular matrix. 16-3-16 is a conventional gemini surfactant bearing two quaternary amines, linked by a 3-carbon spacer region, 16(Py)-S-2-S-(Py)16 contains two pyridinium head groups, while 16-7N(GK)-16 bears a glycine-lysine di-peptide in the space region. The method was fully validated according to USFDA guidelines. It is the first time that FIA-MS/MS method was developed for the quantification of gemini surfactants, belonging to different structural families. The method was superior to existing liquid chromatographic (LC)-MS/MS methods in terms of sensitivity and time of analysis. Positive electrospray ionization (ESI) in the multiple reaction monitoring (MRM) mode were used on a triple quadrupole-linear ion trap (4000 QTRAP^®) instrument. Deuterated internal standards were used to correct for matrix effects and variations in ionization within the ESI source. Isotope dilution standard curves were established in cellular matrix, with a linear range of 10 nM-1000 nM for 16-3-16 and 16(Py)-S-2-S-(Py)16, and 20 nM-2000 nM for 16-7N(GK)-16. The precision, accuracy, recovery and stability were all within the acceptable ranges as per the USFDA guidelines. The method was successfully applied for the quantification of target gemini surfactants in the nuclear fraction of PAM 212 keratinocyte cells treated with nanoparticles, which varied significantly and may explain differences in the observed efficiency and/or toxicity of these gemini surfactants in gene delivery.

Development and validation of fast and simple flow injection analysis-tandem mass spectrometry (FIA-MS/MS) for the determination of metformin in dog serum

A simple, fast and sensitive quantification method for the drug metformin in dog serum was developed using flow injection analysis (FIA)-tandem mass spectrometry (MS/MS). The method was fully validated according to industry standards. It is the first time that FIA-MS/MS for metformin was developed surpassing all existing methods in terms of time of analysis. The quantification method was dependent on the formation of [M+H](+) using electrospray ionization (ESI) and employing multiple reaction monitoring (MRM) using quadrupole-linear ion trap (4000 QTRAP(®)) instrument. A deuterated internal standard (IS) of metformin bearing six deuterium atoms was used to compensate for matrix effects and for variation in ion current within the ESI source. The ion transitions that were monitored were m/z 130.1→m/z 71.0 and m/z 130.1→m/z 60.1 for metformin and m/z 136.0→m/z 77.0 for the internal standard. A linear response (r=0.9966) was established for a range of concentrations of 5-2340 ng/mL. The inter- and intra-day variations were within the acceptable criteria for all quality control samples. The method was successfully applied for measurement of serum metformin concentration in dogs after intravenous injection.

Bioequivalence of nifedipine softgel and capsule in healthy Chinese volunteers by liquid chromatography-mass spectrometry

The study aimed to compare and evaluate the bioequivalence of Calcigard-10 softgel and Adalat 10 capsule in healthy Chinese volunteers in a randomized, two-way cross over study design with a washout period of 7 days. A sensitive and reproducible electro-spray ionization liquid chromatography-mass spectrometry (ESI-LCMS) assay was developed and validated to determine nifedipine in human plasma using nitrendipine as internal standard. Nifedipine and nitrendipine were extracted from plasma using liquid-liquid extraction with methylene chloride as extraction solvent. The separation was performed by a Diamonsil ODS column (150 x 4.6 mm, 5 microm). The mobile phase was consisted of acetonitrile-5 mM ammonium acetate (52:48, v/v), delivered at flow rate of 1 mL/min. The 90% confidence intervals for the ratio values of logarithmic transformed Cmax and AUC were calculated to evaluate the bioequivalence of two preparations. The values of Cmax (92.3-112.7%), AUC0-t (84.5-95.1%) and AUC0-inf (84.4-95.5%) are within the interval criterion of 70-143% for Cmax and 80-125% for AUC. The Calcigard-10 softgel and Adalat 10 capsule are bioequivalent.

Identification of Photoproducts of Hexahydroquinoline Derivatives by GC-EI-MS and HPLC-ESI-MS

Photoproducts of hexahydroquinoline derivatives have been analyzed with gas chromatography electro ionization-mass spectrometry (GC-EI-MS) and high performance chromatography electrospray ionization-mass spectrometry (HPLC-ESI-MS). The study was performed on four HHQ derivatives: 2,6,6-trimethyl-3-carbomethoxy-5-oxo-4-(R-phenyl)-1,4,5,6,7,8-hexahydroquinoline; R=2'-Me, 3'-Me, 2'-MeO, and 3'-MeO. The photochemical degradation of each of the HHQ derivatives led to the appearance of one product. The photoproducts were identified as the corresponding tetrahydroquinoline analogues, which were formed by dehydrogenation of dihydropyridine moiety. In GC-mass spectra, the most frequent way of fragmentation was elimination of CH3* or CH3O* radical of the ester group. In the photoproducts substituted at 2'-position of the phenyl ring, elimination of isobutene (C4H8) was observed. In the photoproducts with 3'-position substituents, elimination of COOCH3* radical was noted.

Effect of subacute methyl parathion administration on the pharmacokinetics and pharmacodynamics of nifedipine in rats

Families living in agricultural areas may submitted to repeated exposure of methyl parathion (MP) that has been widely used as an agricultural insecticide. MP inhibits cytochrome P450 enzymes and has the potential to alter pharmacokinetic profiles of therapeutic agents that are metabolized in the liver. The aim of the present study is to investigate the possibility that the increased pharmacokinetic and pharmacodynamic effects of nifedipine is due to the inhibition of the metabolism after repeated administration of low doses of MP in rats. Male rats received commercial formulation of diluted MP (1/100 LD(50) or 1/25 LD(50), n=6) or tap water (control, n=5) via gastric gavage (0.5ml) for 14 days. On the 15th day, the carotid artery and jugular vein were cannulated for measurement of cardiovascular parameters and blood sampling, respectively. Nifedipine was administered 3mg/kg via the cannula inserted in the duodenum of the rat. Subacute MP administration did not change pharmacokinetic AUC((0-240)), C(max), t(max), t(1/2)) and pharmacodynamic (mean arterial pressures and heart rates) parameters of nifedipine. These findings provide evidence that repeated exposure of low doses of commercial MP did not affect the elimination of nifedipine which might be due to the lack of inhibition of CYP3A in rats.

Development of an HPLC method for the determination of nifedipine in human plasma by solid-phase extraction

Nifedipine, a dihydropyridine calcium channel antagonist, is widely used in the treatment of hypertension and other cardiovascular disorders. A selective, sensitive and accurate high-performance liquid chromatographic method has been developed, validated and applied for determination of nifedipine in human plasma samples. A series of studies were conducted in order to investigate the effects of mobile phase composition, buffer concentration, mobile phase pH and concentration of organic modifiers, and to develop a convenient and easy-to-use method for quantitative analysis of nifedipine. The method involves solid-phase extraction on C18 cartridges. The chromatographic separation was accomplished on a Lichrocart Lichrospher 60 RP selectB column with a mobile phase composed of 0.020 mol/L KH2PO4 (pH 4.8) and acetonitrile (42:58, v/v). UV detection was set at 240 nm. The calibration curve was linear in the concentration range of 5.0-200.0 ng/mL for nifedipine in plasma and the limit of quantification was 5.0 ng/mL.

Sensitive and simple liquid chromatographic method with ultraviolet detection for the determination of nifedipine in canine plasma

An isocratic high-performance liquid chromatographic method with detection at 240 nm was developed, optimized and validated for the determination of nifedipine in canine plasma. Liquid-liquid extraction was used as the sample preparation technique. Carbamazepine was used as internal standard. A Hypersil BDS RP-C18 column (250 mm x 4.6 mm, 5 microm) was equilibrated with a mobile phase composed of water and methanol, 45:55 (v/v). Its flow rate was 1 ml min(-1). The elution time for nifedipine and carbamazepine was approximately 12 and 8 min, respectively. Calibration curves of nifedipine in plasma were linear in the concentration range of 1-200 ng ml(-1). Limits of detection and quantification in plasma were 0.5 and 1.5 ng ml(-1), respectively. Recovery was greater than 98%. Intra- and inter-day relative standard deviation for nifedipine in plasma was less than 8.5 and 10%, respectively. This method was applied to the determination of nifedipine plasma levels after administration of commercially available soft gelatine capsules to dogs.

Gas chromatography-mass spectrometry identification of photoproducts of hexahydroquinoline derivatives: potential calcium channel antagonists

Photodegradation products of hexahydroquinoline derivatives (HHQ) have been analysed with gas chromatography-mass spectrometry (GC-MS). The photodegradation was carried out under the conditions recommended in the first version of the document issued by the International Conference on Harmonization (ICH), currently in force in the studies of photochemical stability of drugs and therapeutic substances. The study was performed on the compounds having two chlorine atoms at different positions of the phenyl ring. Photodegradation of dichlorophenyl derivatives of HHQ resulted in formation of one or three photoproducts. The main product of their decomposition was aromatic compound formed as a result of dehydrogenation of the dihydropyridine ring. The most often observed fragmentation pathway of the photoproducts formed was elimination of methyl and methoxy radicals from the ester groups. The fragmentation of the photoproducts containing one chlorine atom at the ortho-position of the phenyl ring occurred through elimination of chlorine radical.

Quantitative Determination of the Calcium Channel Antagonists Amlodipine, Lercanidipine, Nitrendipine, Felodipine, and Lacidipine in Human Plasma Using Liquid Chromatography-Tandem Mass Spectrometry

A sensitive and specific liquid chromatography-tandem mass spectrometric method has been developed and validated for the quantification of the five 1,4-dihydropyridine calcium channel antagonists amlodipine, lercanidipine, nitrendipine, felodipine, and lacidipine in human plasma. Sample preparation involved solid-phase extraction on RP-C18 cartridges with good recovery for all the compounds. Sample analysis was performed on a Luna RP-C18 analytical column (15 mm x 2 mm ID, 3.0 microm) with a Sciex API 365 triple quadrupole mass spectrometer with turboionspray source and multiple reaction monitoring. The method is sensitive with a limit of detection below 1 ng/mL for each drug in plasma, with good linearity (r(2) > 0.998), over the therapeutic concentration range (1 to 40 ng/mL). All the validation data, such as accuracy, precision, and interday repeatability, were within the required limits. The method can be used for pharmacokinetic studies and therapeutic drug monitoring of the compounds in humans.

Determination of benidipine in human plasma using liquid chromatography–tandem mass spectrometry

We developed a method for determining benidipine, a dihydropyridine analogue calcium-channel blocker, in plasma using liquid chromatography-tandem mass spectrometry (LC-MS-MS). Benidipine and benidipine-d5, an internal standard, were extracted from plasma using diethyl ether in the presence of 5M NaOH. After drying the organic layer, the residue was reconstituted in acetonitrile and injected onto a reversed-phase C18 column. The isocratic mobile phase (acetonitrile-5mM ammonium acetate, 90:10, v/v) was eluted at 0.2 ml/min. The ion transitions monitored in multiple reaction-monitoring mode were m/z 506-174 for benidipine and m/z 511-179 for the internal standard. The coefficient of variation of the assay precision was less than 13%, and the accuracy exceeded 92%, except at the limit of quantification, 0.05 ng/ml with 1ml of plasma, when it was 85%. This method was used to measure the benidipine concentration in plasma from healthy subjects after a single 4-mg oral dose of benidipine. This method is a very simple, sensitive, and accurate way to determine the plasma benidipine concentration.

Determination of nifedipine in human plasma by solid-phase extraction and high-performance liquid chromatography: validation and application to pharmacokinetic studies

Nifedipine, a dihydropyridine calcium channel antagonist, is widely used in the treatment of hypertension and other cardiovascular disorders. A simple, rapid, sensitive, precise and accurate HPLC method, using solid-phase extraction, for the quantitation of nifedipine in human plasma was developed and validated. The calibration graphs were linear in the 5-400 ng/ml concentration range (r>0.999). Recovery for nifedipine was greater than 93.9% and for internal standard nitrendipine was 96.1%. Intra-day and inter-day precision ranged from 1.4 to 4.2 and 3.9 to 5.6%, respectively. Intra-day and inter-day accuracy was ranged from 94.5 to 98.0 and 93.1 to 98.0%, respectively. The method was not interfered with by other plasma components and was applied for the determination of nifedipine in pharmacokinetic study after single oral administration of 10 mg nifedipine to 18 healthy male subjects.

Cathodic adsorptive stripping square-wave voltammetric determination of nifedipine drug in bulk, pharmaceutical formulation and human serum

Nifedipine is a calcium-channel antagonist drug used in the management of angina pectoris and hypertension through inhibition of calcium influx. A fully validated sensitive cathodic adsorptive stripping square-wave voltammetry procedure was optimized for the determination of the drug at trace levels. The procedure was based on the reduction of the nitrophenyl group after the interfacial accumulation of the drug onto a hanging mercury drop electrode in Britton-Robinson buffer of pH 11.0. The optimal conditions of the procedure were found to be: accumulation potential=-0.9 V vs. Ag/AgCl/KCl(s)), accumulation time=30 s, scan increment=10 mV, pulse amplitude=50 mV and frequency=120 Hz. Under these conditions, a well-defined peak was obtained; its peak current showed a linear dependence on drug concentration in the range of 2x10(-9)-2x10(-7) mol L(-1) bulk nifedipine. The mean recoveries based on eight replicate measurements for 1x10(-8) and 5x10(-8) mol L(-1) bulk nifedipine solutions were 98.46+/-0.86% and 98.23+/-0.92%, respectively. A detection limit of 3.42x10(-10) mol L(-1) bulk nifedipine was achieved. The procedure was successfully applied for assay of the drug in tablets and spiked human serum with mean recoveries of 101.95+/-1.42% and 98.70+/-0.63%, respectively. The limit of detection of the drug in spiked human serum was found to be 3.90x10(-10) mol L(-1).

Identification of photodegradation products of nilvadipine using GC-MS

Nilvadipine (NV) photodegradation products have been analysed with gas chromatography-mass spectrometry (GC-MS). The photodegradation was carried out in the conditions recommended in the first version of the document issued by the International Conference on Harmonization (ICH), currently in force in the studies of photochemical stability of drugs and therapeutic substances. Methanol solutions of NV were irradiated with a high-pressure UV lamp - type HBO 200. The maximum intensity at the wavelength lambda = 365 nm was achieved by applying the interference filter and Wood's filter. Using the Reinecke salt as a chemical actinometer, apparent quantum yields of photodegradation were obtained, which after extrapolation to the zero time of irradiation gave the actual quantum yield ((phi = 7.58 x 10(-5). The structure of three nilvadipine photodegradation products was established, after mass spectra analysis of compounds registered during GC-MS carried out of irradiated nilvadipine solutions. The quantitative results of GC-MS analyses enabled to determination of the kinetic parameters of NV photodegradation, calculated from the dependence In c =f(t). Quantitatively the process was described with the calculated rate constant of decomposition (k), decomposition time of 50% of the compound (t0.5) and decomposition time of 10% of the compound (t0.1). The exposure of nilvadipine to UV light was found to lead to aromatization of the DHP ring and elimination of the HCN molecule.

Quantitation of nifedipine in human plasma by on-line solid-phase extraction and high-performance liquid chromatography

An analytical methodology for nifedipine quantitation in plasma by on-line solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) is described. The SPE cartridges contain C2 and the analytes nifedipine and nitrendipine (internal standard) are separated on a C18 column with a mobile phase consisting of acetonitrile-13 mM phosphate buffer pH 7 (65:35, v/v) followed by UV detection at 338 nm. Validation of the method demonstrated good recoveries (>90%), sensitivity (limit of quantification, 2 ng/ml), based on a 500 microl sample volume, accuracy and precision (<5.5% in concentrations greater than the limit of quantitation). This methodology has been used for bioequivalence studies.