Simultaneous determination of enantiomers of structurally related anticholinergic analogs in human serum by liquid chromatography-electrospray ionization mass spectrometry with on-line sample cleanup

Green spectrophotometric and spectrofluorimetric determination of biperiden hydrochloride using erythrosine B sensing probe

Erythrosine B (EB) is a food colorant antiviral xanthene dye that has many applications as a color additive in pharmaceuticals and cosmetics. Its use as a sensor for spectrofluorimetric and spectrophotometric analysis of amine-based pharmaceuticals renders many advantages because of its availability, low cost, rapid labeling, and high sensitivity. Herein, two fast and sensitive spectrofluorimetric and spectrophotometric methods were established for the estimation of the anti-Parkinson drug, biperiden (BIP) hydrochloride (HCl), in its raw material and tablet forms. The proposed methods depended on the interaction between the phenolic group of EB and the tertiary amino group of the studied analyte to form an ion-pair complex at pH 4 using the Britton Robinson buffer. The spectrofluorimetric method is based on the measurement of the quenching power of BIP HCl on the fluorescence intensity of EB at λex/em = 527.0/550.9 nm. This method was rectilinear over the concentration range of 0.1-1.0 μg/mL with a limit of detection (LOD) = 0.017 μg/mL and a limit of quantification (LOQ) = 0.05 μg/mL. Meanwhile, the colorimetric method involved monitoring the absorbance of the formed ion-pair complex at 555 nm, showing a linearity range of 0.4-5.0 μg/mL with LOD = 0.106 μg/mL and LOQ = 0.322 μg/mL. The proposed methods were assessed for the greenness, indicating the greenness of the developed methods.

A novel method for the therapeutic drug monitoring of biperiden in plasma by GC-MS using salt-assisted liquid-liquid microextraction

Biperiden is an anticholinergic agent with central effects. It is used in Parkinson's syndromes and in the treatment of extrapyramidal symptoms that occur with the use of various agents (neuroleptics, antipsychotics). It causes anticholinergic syndrome in high doses. For this reason, therapeutic drug monitoring of biperiden is important. This study, it was aimed to develop a validated GC-MS method for the therapeutic monitoring of biperiden in human plasma. Biperiden and internal standard biperiden-d5 were extracted from plasma using the salt-assisted liquid-liquid extraction method. The method was validated according to the European Medicines Agency (EMA), Bioanalytical method validation guidelines. The lower limit of quantification of the developed method was chosen as 0.5 ng/mL. The calibration curve of biperiden for the method was validated between 0.5 and 15 ng/mL, showing correlation coefficients >0.99. In addition, the developed method was used for the therapeutic drug monitoring of biperiden in real patient plasma.

A Novel Reduced Graphene Oxide Modified Carbon Paste Electrode for Potentiometric Determination of Trihexyphenidyl Hydrochloride in Pharmaceutical and Biological Matrices

A novel promising carbon paste electrode with excellent potentiometric properties was prepared for the analysis of trihexyphenidyl hydrochloride (THP), the acetylcholine receptor and an anticholinergic drug in real samples. It contains 10.2% trihexyphenidy-tetraphenylborate ionic pair as the electroactive material, with the addition of 3.9% reduced graphene oxide and 0.3% of anionic additive into the paste, which consists of 45.0% dibutylphthalate as the solvent mediator and 40.6% graphite. Under the optimized experimental conditions, the electrode showed a Nernstian slope of 58.9 ± 0.2 mV/decade with a regression coefficient of 0.9992. It exhibited high selectivity and reproducibility as well as a fast and linear dynamic response range from 4.0 × 10⁻⁷ to 1.0 × 10⁻² M. The electrode remained usable for up to 19 days. Analytical applications showed excellent recoveries ranging from 96.8 to 101.7%, LOD was 2.5 × 10⁻⁷ M. The electrode was successfully used for THP analysis of pharmaceutical and biological samples.

Flow injection determination of benzhexol based on its sensitizing effect on the chemiluminescent reaction of Ce(IV)-sulfite

In this paper, a novel chemiluminescent (CL) method for the determination of benzhexol has been developed by combining the flow injection technique and its sensitizing effect on the weak CL reaction between sulfite and acidic cerium(IV). A mechanism for the CL reaction has been proposed on the basis of CL spectra. Under the optimized conditions, the proposed method allows the measurement of benzhexol hydrochloride over the range 0.1-10 microg/mL with a correlation coefficient of 0.9992 (n = 8), a detection limit of 0.02 microg/mL (3sigma), and a relative standard deviation for 2.0 microg/mL benzhexol (n = 11) of 1.65%. The utility of this method was demonstrated by determining benzhexol hydrochloride in tablets.

Development and validation of a stability-indicating high performance liquid chromatographic (HPLC) assay for biperiden in bulk form and pharmaceutical dosage forms

Current compendial (USP) methods of assay for the analysis of biperiden in bulk form and pharmaceutical dosage forms involve the use of titrimetric and spectrophotometric procedures, respectively. These are non-selective and non-stability-indicating techniques. In this work, a stability-indicating high performance liquid chromatographic assay procedure has been developed and validated for biperiden. The liquid chromatographic separation was achieved isocratically on a symmetry C8 column (150 mm x 3.9 mm i.d., 5 microm particle size) using a mobile phase containing methanol-buffer (50:50, v/v, pH 2.50) at a flow rate of 1 ml/min and UV detection at 205 nm. The buffer was composed of sodium dihydrogen phosphate (50 mM) and 1-heptanesulfonic acid sodium salt (5 mM). The method was linear over the concentration range of 0.5-25 microg/ml (r=0.9998) with a limit of detection and quantitation 0.03 and 0.1 microg/ml, respectively. The method has the requisite accuracy, selectivity, sensitivity and precision to assay biperiden in bulk form and pharmaceutical dosage forms. Degradation products resulting from the stress studies did not interfere with the detection of biperiden and the assay is thus stability-indicating.

Determination of the enantiomeric composition of a new insulin sensitizer in plasma samples from non-clinical and clinical investigations using chiral HPLC with electrospray tandem mass spectrometric detection

Two drug assays were developed and applied to assess the enantiomeric composition of an insulin sensitizer drug in plasma after administration of its racemate to man, and in human and animal plasma and serum samples generated after in vitro experiments. The sample preparation for the assays consisted either of protein precipitation and column-switching, or liquid-liquid extraction and direct injection. Subsequently, both assays employed chiral HPLC coupled to atmospheric pressure ionization mass spectrometry. An interconversion of the racemate to a mixture enriched with the (+)-enantiomer could be confirmed for all species and biological matrices. The individual enantiomers could be quantified in the concentration range 0.5-500 ng/ml, starting with a 100-microl plasma aliquot. Inter- and intra-assay precision and accuracy were in the range 0.1-7.9 and 88.8-106.0%, respectively. Run times of 5 min for a single sample allows the analysis of more than 200 samples overnight.

Liquid separation techniques coupled with mass spectrometry for chiral analysis of pharmaceuticals compounds and their metabolites in biological fluids

Determination of the chiral composition of drugs is nowadays a key step in order to determine purity, activity, bioavailability, biodegradation, etc., of pharmaceuticals. In this article, works published for the last 5 years on the analysis of chiral drugs by liquid separation techniques coupled with mass spectrometry are reviewed. Namely, chiral analysis of pharmaceuticals including, e.g., antiinflammatories, antihypertensives, relaxants, etc., by liquid chromatography-mass spectrometry and capillary electrophoresis-mass spectrometry are included. The importance and interest of the analysis of the enantiomers of the active compound and its metabolites in different biological fluids (plasma, urine, cerebrospinal fluid, etc.) are also discussed.

Development of a screening method for the most commonly abused anticholinergic drugs in Jordan; trihexyphenidyl, procyclidine and biperiden

A sensitive and rapid method for the simultaneous determination of three commonly abused anticholinergic drugs in Jordan; trihexyphenidyl, procyclidine, and biperiden in plasma and urine has been developed using solid phase extraction and GC-MS. Linearity was established from therapeutic to fatal concentrations of the three drugs; 5-300 ng/ml in plasma, with correlation coefficient r(2) > or = 0.9978 and 10-800 ng/ml in urine r(2) > or = 0.9993. Recoveries were in the range of 86-92% and intra-day and inter-day relative standard deviations (n = 6) were in the range of 6.6-10.3% for the three drugs at three different concentrations in plasma and urine. The base peak m/z 98 for trihexyphenidyl, m/z 84 for procyclidine, and m/z 98 and 218 for biperiden, and m/z 339 for papaverine (internal standard) were monitored at selective ion monitoring; their retention times were 8.10, 8.67 and 8.92 min, respectively, and 14.79 min for the internal standard with analysis time of 16.75 min. The limit of detection of 0.5 ng/ml was attained for trihexyphenidyl and procyclidine, while for biperiden 2.0 and 1.0 ng/ml in spiked plasma and urine, respectively. This method has been applied to forensic and authentic samples taken from abuser and patients using these drugs. The method will offer the clinicians and the legal authority the right diagnosis regarding the anticholinergic involved in any case of abuse with less than 1 h per sample (plasma or urine) from the time of receiving.

Restricted access materials and large particle supports for on-line sample preparation: an attractive approach for biological fluids analysis

An analytical process generally involves four main steps: (1) sample preparation; (2) analytical separation; (3) detection; and (4) data handling. In the bioanalytical field, sample preparation is often considered as the time-limiting step. Indeed, the extraction techniques commonly used for biological matrices such as liquid-liquid extraction (LLE) and solid-phase extraction (SPE) are achieved in the off-line mode. In order to perform a high throughput analysis, efforts have been engaged in developing a faster sample purification process. Among different strategies, the introduction of special extraction sorbents, such as the restricted access media (RAM) and large particle supports (LPS), allowing the direct and repetitive injection of complex biological matrices, represents a very attractive approach. Integrated in a liquid chromatography (LC) system, these extraction supports lead to the automation, simplification and speeding up of the sample preparation process. In this paper, RAM and LPS are reviewed and particular attention is given to commercially available supports. Applications of these extraction supports, are presented in single column and column-switching configurations, for the direct analysis of compounds in various biological fluids.

Simultaneous chiral analyses of multiple analytes: case studies, implications and method development considerations

The field of chiral separations had a modest beginning some two decades ago. However, due to rapid technological advancement coupled with simultaneous availability of innovative chiral stationary phases and novel chiral derivatization agents, the field of chiral separations has now totally outpaced many other separation fields. Keeping pace with rapid changes in the field of chiral separations, investigators continue to add stereoselective pharmacokinetic, pharmacodynamic, pharmacologic and toxicological data of new and/or marketed racemic compounds to the literature. Examination of the evolution of chiral separations suggests that in the beginning many investigators attempted to separate and quantify a single pair of enantiomers, adopting either direct (separation made on a chiral stationary phase) or indirect (separation made following precolumn conversion of enantiomers to corresponding diastereomers) approaches. However, more recent trends in chiral separations suggest that investigators are attempting to separate and quantify multiple pairs of enantiomers with available technologies. Added to this, some interesting trends have been observed in many of the recently reported chiral applications, including preferences regarding internal standard selection, mobile phase contents and composition, sorting out issues with mass spectrometric detection, determination of elution order, analytical manipulations of metabolite(s) without reference standards and addressing some specificity-related issues. This review mainly focuses on chiral separations involving multiple chiral analytes and attempts to justify the need for such chiral separations involving multiple analytes. In this context, several cases studies are described on the utility and applicability of such chiral separations under discrete headings to provide an account to the readership on the implications of such tasks. The topics of case studies covered in this review include: (a) therapy markers--differentiation from drug abuse and/or applicability in forensics; (b) role in pharmacogenetic/polymorphic evaluation; (c) monitoring and understanding the role of parent and active metabolite(s) in clinical and preclinical investigations; (d) exploration on the pharmacokinetic utility of an active chiral metabolite vis-a-vis the racemic parent moiety; (e) understanding the chirality play in delineating peculiar toxic effects; (f) exploration of chiral inversion phenomenon, and understanding the role of stereoselective metabolism. For the further benefit of readership, some select examples (n = 19) of the separation of multiple chiral analytes with appropriate information on chromatography, detection system, validation parameters and applicable conclusion are also provided. Finally, the review covers some useful considerations for method development involving multiple chiral analytes.

Automated LC-MS Method for the Fast Stereoselective Determination of Methadone in Plasma

Methadone (MTD) is a chiral drug widely used for the treatment of opioid dependence for which a rapid analytical method for the determination of each enantiomer would be advantageous. In order to improve method sensitivity and to automate the entire analytical process, a column-switching configuration has been developed. An online extraction system coupled to a cellulose-based chiral stationary phase (CSP), namely Chiralcel OJ-R, was used and detection was performed by mass spectrometry. Fifty microl of plasma were injected into the liquid chromatography-mass spectrometry (LC-MS) system after addition of acetonitrile (ACN) containing methadone deuterated D9 (MTD-D9) (internal standard) and centrifugation. For the rapid extraction step, a large particle size support was selected. A baseline separation of MTD enantiomers was obtained in less than 12 min. Trueness and precision were evaluated with control samples at 500 ng/ml of (R,S)-methadone. Trueness values were 106.6% and 103.0% for (R)-MTD and (S)-MTD, respectively, with a coefficient of variation inferior to 2.5% for both compounds. Finally, a good concordance was found using this method for analysis of plasma samples from patients in maintenance treatment as compared to a previously described HPLC-UV method after liquid-liquid extraction.

Use of online-dual-column extraction in conjunction with chiral liquid chromatography tandem mass spectrometry for determination of terbutaline enantiomers in human plasma

An online sample extraction chiral bioanalytical method was developed and validated for the quantification of terbutaline, a beta2-selective adrenoceptor agonist, spiked into human plasma by using two extraction columns and a chiral stationary phase (CSP) in conjunction with liquid chromatography tandem mass spectrometry (LC-MS/MS). In this method, two Oasis HLB extraction columns were used in parallel for plasma sample purification and a Chirobiotic T CSP was used for enantiomeric separation. Atmospheric pressure chemical ionization MS/MS was employed in multiple reaction monitoring mode for the detection and quantification. Subsequent to the addition of an internal standard solution, the plasma samples were directly injected onto the system for extraction and analysis. This method allowed the use of one of the extraction columns for purification while the other was being equilibrated. Hence, the time required for reconditioning the extraction columns did not contribute to the total analysis time per sample, which resulted in a shorter run time and higher throughput. A lower limit of quantification of 1.0 ng/mL was achieved using only 50 microliter of human plasma. The method was validated with a dynamic range of 1.0-200 ng/mL. The intra- and interday precision was no more than 11% CV and the assay accuracy was between 94-106%.