HPLC-DAD determination of Metformin in human plasma using derivatization with p-nitrobenzoyl chloride in a biphasic system

LC-MS/MS Method Assay for Simultaneous Determination of the Apixaban and Metformin in Rat Plasma: Assessment of Pharmacokinetic Drug-Drug Interaction Study

A simple, sensitive and accurate LC-MS/MS method was developed and validated for the simultaneous quantification of apixaban (APB) and metformin (MET) in rat plasma using rivaroxaban as internal standard (IS). An Inertsil ODS3 C18 column (150 × 4.6 mm, 5 μm) was used for chromatographic separation with isocratic elution. Multiple reaction monitoring (MRM) using positive-ion ESI mode to monitor ion transitions of m/z 459.8 → 442.8 for APB, m/z 130.2 → 71.2 for MET, m/z 436.8 → 144.9 for IS. The procedure of method validation included selectivity, linearity, precision, accuracy, matrix effect, extraction recovery and stability were conducted according to the guidelines of EMA and FDA. The method was validated over the concentration range of 0.5-250 ng/mL for APB and 8-8000 ng/mL for MET. The intra- and inter-day precision and accuracy of the quality control samples exhibited relative standard deviations (RSD) < 12.5% and the accuracy values ranged from -8.6 to 12.4%. Recovery and matrix effect values variations were all less than 15%. After oral administration APB and MET to rats, the comparison of pharmacokinetic parameters of APB in the single and co-administrated groups showed significant difference in AUC(0-t) from 730.71 ± 121.31 to 573.07 ± 90.13 ng/mL·h, t1/2 from 5.86 ± 3.21 to 4.24 ± 1.15 h and Cmax from113.54 ± 24.04 to 159.42 ± 54.6 ng/mL. The comparison of pharmacokinetic parameters of MET in the single and co-administrated groups showed significant difference in t1/2 from 2.83 ± 1.81 to 3.97 ± 0.57 h and Cmax from 4015.76 ± 873.23 to 3153.6 ± 1012.51 ng/mL. The results indicated that drug-drug interactions (DDI) occurred might be owing to APB affect one or all of OCTs, MATE1, MATE2-K.

Graphene and zeolite as adsorbents in bar-micro-solid phase extraction of pharmaceutical compounds of diverse polarities

A bar micro-solid phase (bar μ-SPE) extraction method using either graphene or zeolite or their mixtures as an adsorbent, coupled with high-performance liquid chromatography (using a C1 column) was developed for the simultaneous determination of pharmaceutical compounds (metformin (MET), buformin (BUF), phenformin (PHEN) and propranolol (PROP)) of diverse polarity (log P from -1.82 to 3.10). Parameters influencing the extraction, such as conditioning solvents, pH of the sample, sample volume, amount of adsorbent, stirring rate, time of extraction, type and volume of desorption solvent and time of desorption were investigated. Under the optimized conditions, the extraction method using graphene (extraction efficiency, % EE, ∼6-15%) resulted in the least amount of extracted drugs. However, the use of zeolite and zeolite/graphene mixtures improves the % EE significantly, i.e. 30% for PHEN and 42% for PROP using zeolite; 22% for MET and 18% for BUF using the adsorbent mixture. Under similar conditions, enrichment factors for these drugs range from 11-15. The validated method was performed for the determination of the drugs that were spiked to urine samples. Good recoveries ranging from 72.8 to 116% were achieved.

Improving sensitivity of antimicrobial drug nitrofurazone detection in food and biological samples based on nanostructured anatase-titania sheathed reduced graphene oxide

In this study, we have prepared anatase titanium (IV) oxide warped reduced graphene oxide nanocomposites (TiO₂-rGO NC) using ultrasonic methodology. The morphology of the TiO₂-rGO NC was studied using FESEM and TEM. In addition, XRD, Raman, thermogravimetric analysis (TGA) and XPS are used to analyze the crystallinity and chemical composition of the TiO₂-rGO NC. We have also investigated the electrochemical behavior of the as-prepared NCs with electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and different pulse voltammetry techniques (DPV). The TiO₂-rGO NC modified electrode shows the lower charge transfer resistance (R _ct ) of 62.87 Ω. Next, the glassy carbon electrode (GCE) was modified with sonochemically prepared TiO₂-rGO NC and used to determine the electrocatalytic reduction of nitrofurazone (NTF). Thus, the proposed sensor established the wider covering range (WCR) of 0.01 to 380 µM and an excellent detection limit of 2.28 nM. Finally, the TiO₂-rGO NC/GCE was applied to determine the NTF in real samples, including crayfish and human blood serum samples, which acquired good found and recovery values.

Derivatization procedures and their analytical performances for HPLC determination in bioanalysis

Derivatization, or chemical structure modification, is often used in bioanalysis performed by liquid chromatography technique in order to enhance detectability or to improve the chromatographic performance for the target analytes. The derivatization process is discussed according to the analytical procedure used to achieve the reaction between the reagent and the target compounds (containing hydroxyl, thiol, amino, carbonyl and carboxyl as the main functional groups involved in derivatization). Important procedures for derivatization used in bioanalysis are in situ or based on extraction processes (liquid-liquid, solid-phase and related techniques) applied to the biomatrix. In the review, chiral, isotope-labeling, hydrophobicity-tailored and post-column derivatizations are also included, based on representative publications in the literature during the last two decades. Examples of derivatization reagents and brief reaction conditions are included, together with some bioanalytical applications and performances (chromatographic conditions, detection limit, stability and sample biomatrix).

A rapid and efficient removal approach for degradation of metformin in pharmaceutical wastewater using electro-Fenton process; optimization by response surface methodology

Presence of emerging contaminants such as pharmaceutical products in aquatic environments has received high concern due to their undesirable effect on wildlife and human health. Current work deals with developing a treatment model based on the electro- Fenton (EF) process for efficient removal of metformin (MET) from an aqueous medium. The obtained experimental results revealed that over the reaction time of 10 min and solution pH of 3, the maximum removal efficiency of 98.57% is achieved where the value of MET initial concentration, current density, and H₂O₂ dosage is set at 10 mg.L^-1, 6 mA.cm^-2, and 250 μL.L^-1, respectively, which is in satisfactory agreement with the predicted removal efficiency of 98.6% with the desirability of 0.99. The presence of radical scavengers throughout the mineralization of MET under the EF process revealed that the generation of ^•OH radicals, as the main oxidative species, controlled the degradation mechanism. The obtained kinetics data best fitted to the first order kinetic model with the rate constant of 0.4224 min^-1 (R² = 0.9940). The developed treatment process under response surface methodology (RSM) was employed for modeling the obtained experimental data and successfully applied for efficient removal of the MET contaminant from pharmaceutical wastewater as an adequate and cost-effective approach.

Development, Validation and Application of HPLC Method for Metformin in Rabbit Plasma

Objective:

This study was aimed at conducting a pharmacokinetic evaluation of metformin in rabbit plasma samples using rapid and sensitive HPLC method and UV detection.

Methods:

Acetonitrile was used for protein precipitation in the preparation of plasma samples. Reverse phase chromatography technique with silica gel column (250 mm × 4.6 mm, 5 μm) at 30°was used for the separation purpose. Methanol and phosphate buffer (pH 3.2) mixture was used as a mobile phase with flow rate 0.8 ml/min. The wavelength of UV detector was adjusted at 240 nm.

Results:

The calibration curve was linear in a range of 0.1-1 µg/ml with R² = 0.9982. The precision (RSD, %) values were less than 2%, whereas, accuracy of method was higher than 92.37 %. The percentage recovery values ranged between 90.14 % and 94.97 %. LOD and LOQ values were 25 ng/ml and 60 ng/ml, respectively. Cmax and AUC0-t values were found to be 1154.67 ± 243.37 ng/ml and 7281.83 ± 210.84 ng/ml.h, respectively after treating rabbits with a formulation containing 250 mg metformin.

Conclusion:

Based on the above findings, it can be concluded that present method is simple, precise, rapid, accurate and specific and thus, can be efficiently used for the pharmacokinetic study of metformin.

Novel LC-MS/MS method for analysis of metformin and canagliflozin in human plasma: application to a pharmacokinetic study

Highly sensitive and selective liquid chromatography/tandem mass spectrometry (LC-MS/MS) method was developed and validated for the simultaneous estimation of the recently approved oral hypoglycemic mixture; metformin (MET) and canagliflozin (CFZ) in human plasma using propranolol HCl (PPL) and tadalafil (TDF) as internal standards (IS), respectively. Analytes were extracted using protein precipitation induced by acetonitrile then liquid-liquid extraction was performed using ethyl acetate. Reversed phase HPLC was carried out using C18 analytical column (50 mm × 4.6 mm i.d., 5 µm) with a simple isocratic mobile phase composed of 0.1% formic acid and acetonitrile (60:40, v/v). Detection was performed on a triple quadrupole mass spectrometer employing electrospray ionization technique, operating in multiple reaction monitoring (MRM), with the transitions of m/z 130.2 → 60.1, m/z 462.3 → 191.0, m/z 260.2 → 183.0 and m/z 390.2 → 268.2 for MET, CFZ, PPL and TDF, respectively, in the positive ion mode. The analysis was carried out within 5 min over a linear concentration range of 50-5000 ng/mL for MET and 10-1000 ng/mL for CFZ. The method was validated in accordance with the FDA guidelines for bioanalytical method. All obtained recoveries were higher than 90.0% while the accuracy was in the range of 88.14-113.05% and the relative standard deviation was below 10.0% for all investigated drugs by the proposed method. The achieved promising results has allowed for the successful application of the developed LC-MS/MS method to a pharmacokinetic study of the target drugs after their oral administration to Egyptian healthy volunteers. The pharmacokinetic study was accomplished after the agreement of the ethics committee.

Validation of RP-HPLC method and stress degradation for the combination of metformin HCl, atorvastatin calcium and glimepiride: application to nanoparticles

A stability-indicating high-performance liquid chromatography (HPLC) procedure was developed for the determination of metformin HCl (MTH), atorvastatin calcium (AC) and glimepiride (GP) in combination and their main degradation products. The separation and quantization were achieved on a 5-µm Qualisil gold, C18 column (4.6 mm × 250 mm). The mobile phase selected was phosphate buffer (pH 2.9)-organic phase in proportion of 70:30. Organic phase consisted of methanol-acetonitrile (90:10) at a flow rate of 1 mL/min and detection of analytes was carried out at 230 nm. The method exhibited good linearity over the range of 10-60 µg/mL for MTH, 2-20 µg/mL for AC and 5-30 µg/mL for GP. Square of the correlation coefficients was found to be >0.999. Various stress degradation studies were carried out in combination as per International Conference of Harmonization (ICH) guidelines for 4 h. The recovery and precision were determined in terms of intraday and interday precisions and expressed as relative standard deviations. These were <1 and <2%, respectively. Finally, the applicability of the method was evaluated in nanoparticle analysis of MTH, AC and GP as well as in stability studies of nanoformulation.

Monitoring metformin in cardiac patients exposed to contrast media using ultra-high-performance liquid chromatography tandem mass-spectrometry

BACKGROUND

There is no evidence that the use of contrast media (CM) in diabetic patients with serum creatinine <130 μmole/L leads to metformin accumulation and subsequent lactic acidosis. Therefore, the objective of this investigation was to monitor cardiac patients for the effects of CM on their metformin plasma concentration and serum creatinine clearance (ClCr).

METHODS

Metformin plasma concentrations were measured by a new, fully validated specific, precise, and accurate ultra-high-performance liquid chromatography tandem mass-spectrometric assay. The detection was performed using positive electrospray ionization in the multiple reaction monitoring mode. Fifty patients with serum creatinine levels <130 μmole/L were monitored for the effect of CM exposure on metformin concentration and ClCr. Pharmacokinetic parameters were calculated in 8 of these patients, and metformin accumulation was monitored in 10 patients before and after their exposure to CM.

RESULTS

Linear response (r ≥ 0.998) was observed over the range of 5-2000 ng/mL of metformin, with the lower limit of quantification of 2.3 ng/mL. The intraday and interday precision (relative standard deviation) values were <13%, and the accuracy (relative error) was <-10% for metformin concentrations. The assay was sensitive to follow the pharmacokinetics of metformin in humans during a dosing interval after an oral dose at steady state. Metformin pharmacokinetic parameters were estimated in 8 patients exposed to CM. The mean C(max) of 1.9 ± 0.6 mg/L was attained at 4.1 ± 1.9 hours. There was no evidence of any drug accumulation or altered elimination due to the exposure to CM in the current population. ClCr showed no significant difference (P > 0.05) before (92.8 ± 11.3 mL/min) and after 48 hours (90.5 ± 10.5 mL/min) of exposure to CM.

CONCLUSIONS

Our data suggest that the recommendation to withhold metformin in diabetic patients during CM exposure could be revised to withholding the drug only in patients with moderate to severe renal dysfunction.

HPLC-UV determination of metformin in human plasma for application in pharmacokinetics and bioequivalence studies

In this study, a simple, rapid and sensitive HPLC method with UV detection is described for determination of metformin in plasma samples from bioequivalence assays. Sample preparation was accomplished through protein precipitation with acetonitrile and chromatographic separation was performed on a reversed-phase phenyl column at 40 degrees C. Mobile phase consisted of a mixture of phosphate buffer and acetonitrile at flow rate of 1.0 ml/min. Wavelength was set at 236 nm. The method was applied to a bioequivalence study of two drug products containing metformin, and allowed determination of metformin at low concentrations with a higher throughput than previously described methods.

Direct determination of metformin in urine by adsorptive catalytic square-wave voltammetry

A new adsorptive catalytic voltammetric method for voltammetric determination of metformin based on the catalytic hydrogen evolution reaction at a hanging mercury drop electrode was developed. The electrode reaction was analyzed under conditions of linear sweep voltammetry (LSV), differential pulse voltammetry (DPV) and Osteryoung-type square-wave voltammetry (SWV). The peak current depends on pH of the medium, concentration and chemical composition of the buffer solution, and instrumental parameters. The optimal conditions for quantitative determination were obtained in an acetate buffer at pH 4.7. The voltammetric procedure was characterized with respect to the repeatability, precision and the recovery. The detection and quantification limits were found to be 1.8 x 10(-8) and 5.9 x 10(-8) mol l(-1) for SWV, 3.2 x 10(-8) and 1.0 x 10(-7) mol l(-1) for DPV, and 7.7 x 10(-8) and 2.5 x 10(-7) mol l(-1) for LSV, respectively. The SW voltammetric method, as the most sensitive one, was applied for determination of metformin in human urine. The voltammetric method has been validated by using HPLC with UV detection.

Simultaneous assay of metformin and glibenclamide in human plasma based on extraction-less sample preparation procedure and LC/(APCI)MS

Separation of metformin and glibenclamide was achieved within a single chromatographic run on a Zorbax CN column, under isocratic conditions, using acetonitrile and aqueous component (0.01 moles/L ammonium acetate adjusted at pH 3.5 with acetic acid) in volumetric ratio 1/1. Plasma sample preparation is based on protein precipitation by means of organic solvent addition. 1,3,5-Triazine-2,4,6-triamine (IS1) was used as internal standard for metformin, while gliquidone (IS2) played the same role for glibenclamide. Detection was performed with an ion trap mass analyzer, using atmospheric pressure chemical ionization (APCI). A single MS stage was used for detection of metformin and IS1, by extracting ion chromatograms corresponding to molecular ions. MS/MS detection in the SRM mode was used for glibenclamide (m/z transition from 494 to 369 Da) and IS2 (m/z transition from 528 to 403 Da). The method produces linear responses up to 2000 ng/mL for metformin and 400 ng/mL for glibenclamide, respectively. Low limits of quantification were found in the 40 ng/mL range for metformin and at the 4 ng/mL level for glibenclamide. Precision was characterized by relative standard deviations (RSD%) below 9%. The analytical method was successfully applied to a single dose, open-label, randomized, two-period, two-sequence, crossover bioequivalence study of two commercially available anti-diabetic combinations containing 400 mg metformin and 2.5 mg of glibenclamide per coated tablet.

Dried blood spot liquid chromatography assay for therapeutic drug monitoring of metformin

The use of blood spot collection cards is a simple way to obtain specimens for analysis of drugs for the purpose of therapeutic drug monitoring, assessing adherence to medications and preventing toxicity in routine clinical setting. We describe the development and validation of a microanalytical technique for the determination of metformin from dried blood spots. The method is based on reversed phase high-performance liquid chromatography with ultraviolet detection. Drug recovery in the developed method was found to be more than 84%. The limits of detection and quantification were calculated to be to be 90 and 150 ng/ml, respectively. The intraday and interday precision (measured by CV%) was always less than 9%. The accuracy (measured by relative error, %) was always less than 12%. Stability analysis showed that metformin is stable for at least 2 months when stored at -70 degrees C. The small volume of blood required (10 microL), combined with the simplicity of the analytical technique makes this a useful procedure for monitoring metformin concentrations in routine clinical settings. The method is currently being applied to the analysis of blood spots taken from diabetic patients to assess adherence to medications and relationship between metformin level and metabolic control of diabetes.

Biowaiver extension potential to BCS Class III high solubility-low permeability drugs: bridging evidence for metformin immediate-release tablet

The biopharmaceutics classification system (BCS) allows biowaiver for rapid dissolving immediate-release (IR) products of Class I drugs (high solubility and high permeability). The possibility of extending biowaivers to Class III high solubility and low permeability drugs is currently under scrutiny. In vivo bioequivalence data of different formulations of Class III drugs would support such an extension. The objective of this work was to demonstrate the bioequivalence of two marketed IR tablet products of a Class III drug, metformin hydrochloride, that are rapidly dissolving and have similar in vitro dissolution profiles. The effect of race on the systemic exposure of metformin was also explored. A randomized, open-label, two-period crossover study was conducted in 12 healthy Chinese male volunteers. Each subject received a single-dose of 500 mg of each product after an overnight fasting. The plasma concentrations of metformin were followed for 24 h. No significant formulation effect was found for the bioequivalence metrics: areas under concentration-time curve (AUC0-t, AUC0-infinity) and maximal concentration (Cmax). The 90% confidence intervals for the ratio of means were found within the acceptance range of 80-125% for the log-transformed data. Based on these results, it was concluded that the two IR products are bioequivalent. The pharmacokinetic parameters of metformin in Chinese for both products were similar and were in good agreement with those reported for metformin IR tablets in other ethnic populations. This study serves as an example for supporting biowaiver for BCS Class III drugs.

Development and validation for high selective quantitative determination of metformin in human plasma by cation exchanging with normal-phase LC/MS/MS

An assay based on cation exchange solid-phase extraction and liquid chromatography-tandem mass spectrometry (LC/MS/MS) has been developed for the quantitative determination of metformin in human plasma. The analytical method consists of cation exchange solid-phase extraction (VersaPlate CBA) without any further evaporation/dissolution steps and cation exchange-based HPLC separation (Capcell Pak SCX column) with a normal-phase gradient system followed by semi-micro LC/MS/MS in positive ion selected reaction monitoring mode using electrospray ionization. The method exhibited excellent performance in terms of selectivity, robustness, short run time (7 min/sample) and simplicity of sample preparation. The calibration range was 10-1000 ng/ml with 0.2 ml of plasma. Intra- and inter-day mean accuracies were within the ranges of 100.3-105.0% and 101.2-105.3%, respectively. Intra- and inter-day precisions were within the ranges of 0.8-1.9% and 1.5-8.6%, respectively. Mean absolute recovery was 67.0% for metformin. No apparent loss of metformin after extraction was observed in an autosampler at 10 degrees C for 24 h. Dilution of metformin by blank human plasma up to 20-fold was tested and revealed no impact on the results of determination. Furthermore, the method exhibited high selectivity, since no effect on metformin analysis was observed on comparison of samples with or without nateglinide and other agents in plasma. Results obtained with the method were also comparable to a published LC-UV method on cross-validation. This method can be applied to various clinical pharmacokinetic studies of metformin.

Fast liquid chromatographic-tandem mass spectrometric (LC–MS–MS) determination of metformin in plasma samples

Liquid chromatographic-tandem mass spectrometric (LC-MS-MS) methods for the determination of metformin in plasma from different species are presented. The first method employed a YMC cyano 2mm x 50 mm, 3 microm analytical column. For minimum sample preparation direct injection of samples after protein precipitation was performed. The polar column used with highly organic mobile phases provided a normal phase retention mechanism. The elution conditions were optimized to obtain reproducible peak areas and good peak shape. A step gradient from 100% acetonitrile to acetonitrile-water 80:20 (v/v) containing 10mM ammonium acetate and 1% acetic acid was applied, leading to a sample-to-sample cycle time of 2 min. In a second method, a column-switching LC-MS-MS assay for on-line trapping was developed. The analyte and internal standard were trapped on a YMC cyano 2 mm x 10 mm, 5 microm column using acetonitrile-methanol 95:5 (v/v). Elution was performed isocratically in back-flush mode on to the analytical column (YMC cyano 2 mm x 50 mm, 3 microm) using 10 mM ammonium acetate in acetonitrile-water 80:20 (v/v) with 1% formic acid. With this approach, the signal-to-noise ratio was improved and the run time could be shortened to 1 min. Calibration samples were prepared in the matrix to be assayed in the range of 10-10,000 ng/ml. Quality control (QC) samples were prepared at 40, 400 and 4000 ng/ml and interspersed with the unknown study samples in the assays. Deviations for precision and accuracy were less than 20% for the lower limit of quantification (LLOQ) and low QC sample and less than 15% for other calibrators and QCs.

Determination of metformin in plasma using a new ion pair solid phase extraction technique and ion pair liquid chromatography

This article describes the development of the first ion pair solid phase extraction technique (IPSPE), which has been applied to the extraction of metformin from plasma samples. In addition an ion pair chromatographic method was developed for the specific HPLC determination of metformin. Several extraction and HPLC methods have been described previously for metformin, however, most of them did not solve the problems associated with the high polarity of this drug. Drug recovery in the developed method was found to be more than 98%. The limit of detection and limit of quantification was 3 and 5 ng/ml, respectively. The intraday and interday precision (measured by coefficient of variation, CV%) was always less than 9%. The accuracy (measured by relative error, R.E.%) was always less than 6.9%. Stability analysis showed that metformin is stable for at least 3 months when stored at -70 degrees C. The method has been applied to 150 patient samples as part of a medication adherence study.

Determination of metformin in human plasma by high-performance liquid chromatography with spectrophotometric detection

A simple, selective, sensitive and precise high-performance liquid chromatographic plasma assay for the hypoglycemic agent metformin is described. Acidified samples of plasma were deproteinated with acetonitrile, washed with dichloromethane and the resulting supernatant injected. Chromatography was performed at 40 degrees C by pumping a mobile phase of acetonitrile (250 ml) in pH 7, 0.03 M diammonium hydrogen phosphate buffer (750 ml) at a flow-rate of 1 ml/min through a silica column. Metformin and the internal standard (atenolol) were detected at 240 nm and were eluted 7.8 and 6.8 min, respectively, after injection. No endogenous substances were found to interfere. Calibration curves were linear (r>0.999) from 10 to 2000 ng/ml. The absolute recovery of both metformin and atenolol was greater than 76%. The detection limit and limit of quantitation were 2.5 and 10 ng/ml, respectively. The intra- and inter-day precision (C.V.) was 12%, or less, and the accuracy was within 6.2% of the nominal concentration. This method is suitable for clinical investigation and monitoring metformin concentration.

Determination of cycloserine in human plasma by high-performance liquid chromatography with fluorescence detection, using derivatization with p-benzoquinone

A new method for determining cycloserine in plasma samples is described. This method is based on the derivatization of cycloserine with p-benzoquinone, a reaction that takes place at the same time as the process of plasma deproteinization due to the presence of ethanol as solvent in the solution of the derivatization reagent. Four derivatives are obtained from this reaction. The main derivative is well correlated with the cycloserine concentration. The ratio between the volumes of the plasma sample and the reagent solution is 1:2 for a p-benzoquinone concentration of 1000 microg/mL. Elution from a C18 column was isocratic, using a mobile phase containing (v/v) 85% aqueous 0.1% formic acid solution, and 15% (v/v) of a mixture of methanol and acetonitrile (1:1), with a flow-rate of 1 mL/min, at 25 degrees C. Determinations by fluorescence detection were achieved with excitation at 381 nm and emission at 450 nm, with a detection limit of 10 ng/mL for an injection volume of 5 microL. This method was validated and applied to the determination of cycloserine in blood plasma samples of several healthy volunteers.