Separation of tricyclic psychosedative drugs by high-speed ion-pair partition and liquid-solid adsorption chromatography

Effect of ion-pairing reagent hydrophobicity on liquid chromatography and mass spectrometry analysis of oligonucleotides

We performed a systematic study of thirteen alkylamines used as ion-pairing reagents for ion-pair reversed-phase liquid chromatography (IP RP LC) separations of oligonucleotides on a C18 column. We proposed a method to classify the hydrophobicity of alkylamines by their retention in RP LC. The IP reagent hydrophobicity correlated with the retention and resolution of oligonucleotides in the corresponding IP mobile phases. The baseline resolution was achieved up to 30 mer for hydrophilic, or up to 50 mer for hydrophobic IP reagents. Hydrophobic alkylamines permitted useful oligonucleotide separations at relatively low buffer concentrations, such as 5-10 mM alkylamine-acetate IP systems. These buffers were compatible with mass spectrometry detection, however, replacement of acetic acid with hexafluoroisopropanol in the mobile phase improved the MS signal by 2-3 orders of magnitude. Experiments with native and chemically modified oligonucleotides highlighted the mixed-mode nature of IP RP LC. When using hydrophobic IP reagents, the ionic retention mechanism of oligonucleotides is enhanced while hydrophobic retention is diminished.

Capillary electrophoresis for the analysis of antidepressant drugs: A review

Depression is a common mental disorder that may lead to major mental health problems, and antidepressant drugs have been used as a treatment of choice to mitigate symptoms of major depressive disorders by ameliorating the chemical imbalances of neurotransmitters in brain. Since abusing antidepressant drugs such as selective serotonin reuptake inhibitors and tricyclic antidepressant drugs can cause severe adverse effects, continuous toxicological monitoring of the parent compounds as well as their metabolites using numerous analytical methods appears pertinent. Among them, capillary electrophoresis has been popularly utilized since the method has a lot of advantages viz. using small amounts of sample and solvents, ease of operation, and rapid analysis. This review paper brings a survey of more than 30 papers on capillary electrophoresis of antidepressant drugs published approximately from 1999 until 2018. It focuses on the reported capillary electrophoresis techniques and their applications and challenges for determining antidepressant drugs and their metabolites. It is organized according to the commonly used capillary zone electrophoresis method, followed by non-aqueous capillary electrophoresis and micellar electrokinetic chromatography, with details on breakthrough findings. Where available, information is given about the background electrolyte used, detector utilized, and sensitivity obtained.

A validated high performance liquid chromatographic method for analysis of nicotine in pure form and from formulations

A reverse phase HPLC method using C18 column has been developed for the quantitative estimation of nicotine in the bulk material and formulations (extended release and immediate release dosage forms). The method is specific to nicotine (RT approximately 4.64 min, asymmetry approximately 1.75), and can resolve analyte peak from excipient interferences. It is linear (coefficient of variation approximately 0.9993), accurate (average recovery approximately 100%), and passed all the system suitability requirements. Applicability of the method was evaluated in analysis of drug-excipient compatibility samples, commercial dosage form (such as nicotine gum) and two novel in-house formulations.

Gas chromatographic-mass spectrometric assessment of the pharmacokinetics of amineptine and its main metabolite in volunteers with liver impairment

A pharmacokinetic study of amineptine (Survector) and its C5 metabolite, resulting from a beta-oxidation of the heptanoic acid side-chain, was undertaken with ten human volunteers, who received a single 100-mg tablet of amineptine orally. They were affected with liver impairment in order to determine if this situation would alter greatly the pharmacokinetic parameters. The internal standard was the octanoic acid homologue. Analyses were carried out by gas chromatography (GC) and GC-mass spectrometry using TMS ester derivatives. Plasma samples were extracted using a C18 reversed-phase cartridge at pH 4.0. Mass fragmentographic measurements on the plasma samples were performed on the m/z ions (M + H)+ and (base peak)+ using ammonia chemical ionization. The global evaluation of precision was good and the coherence between the two modes of measurements, (base peak)+ and (M + H)+ ions, gave a regression factor r close to unity. For amineptine the total body clearance and mean residence time were accurate and precise with eight volunteers, but only four volunteers showed such coherent data for the slope of the elimination curve, beta, and half-life. However, the beta value, half-life and mean residence time of the C5 metabolite were accurate and precise with seven, eight and ten volunteers, respectively. It is concluded that the drug was still detoxified at normal levels.

Analysis of tricyclic antidepressant drugs in plasma and serum by chromatographic techniques

A review of methods for the determination of tricyclic antidepressants in plasma or serum, based on the application of chromatographic techniques, is presented. A general discussion of the techniques in terms of their precision, accuracy, sensitivity and selectivity, with respect to parent drug and metabolites, is used to facilitate a comparison of methods. No one technique can be claimed as the method of choice for these drugs, although gas-liquid chromatography with nitrogen selective detection has some strong claims, viz. generally good sensitivity and reproducibility of assays and ready availability of equipment in most laboratories. The ultimate choice of a method for determining tricyclics will be determined more by the clinical application (routine monitoring versus pharmacokinetics) than by other factors.

Determination of cyclobenzaprine in tablets by high-performance liquid chromatography

A convenient high-performance liquid chromatographic method for the quantitative determination of cyclobenzaprine hydrochloride in tablets is described. Samples were dissolved in 0.05 N sulfuric acid and diluted with methanol. The cyclobenzaprine hydrochloride was chromatographed using an octylsilane column and the eluent acetonitrile-0.6% dibasic potassium phosphate aqueous buffer (pH 3.0) (75:25) at a flow rate of 1.5 ml/min. Naphazoline hydrochloride was used as an internal standard. The UV detector response at 254 nm was linear for cyclobenzaprine hydrochloride in the 0.005-0.03 mg/ml range under conditions of the analysis.

GLC method for iminodibenzyl and desipramine impurities in imipramine hydrochloride and its formulated products

A GLC method is described for the determination of iminodibenzyl and desipramine impurities in imipramine hydrochloride and its formulated products. These impurities were extracted from an alkaline solution with a mixture of 30% methylene chloride in hexane for chromatography on a 3% OV-17 GLC column. Iminodibenzyl was determined using anthracene as an internal standard and desipramine was determined (after derivatization) using nortriptyline as an internal standard. Based on spiked excipient mixtures typically used to compound imipramine tablets, recoveries were 93-109% for iminodibenzyl and 93-107% for desipramine at 0.2-0.4% of the labeled claim of imipramine. Minimum detection levels were approximately 0.02% for each impurity, and procedural standards gave coefficients of variation of less than 1% for each impurity. The method was linear in the 0.05-0.5 microgram range and typically gave correlation coefficients greater than or equal to 0.999.

Simultaneous determination of chlorpromazine and levomepromazine in human plasma and urine by high-performance liquid chromatography using electrochemical detection

A rapid, selective and sensitive method for the simultaneous determination of chlorpromazine and levomepromazine in human plasma and urine has been developed using high-performance liquid chromatography with electrochemical detection. The unchanged drugs and internal standard extracted from plasma and urine were separated by reversed-phase high-performance liquid chromatography. The influence of acetonitrile concentration and of the pH of the mobile phase were investigated. The detection limits were 100 pg for chlorpromazine and for levomepromazine. In comparison with three other detection systems this was found to be the most sensitive method. This method was successfully applied to the simultaneous determination of chlorpromazine and levomepromazine in human plasma and urine for pharmacokinetic studies.

Reversed-phase liquid chromatography for the separation of chloropromazine, imipramine and some of their metabolites

Reversed-phase liquid chromatography on a C18 bonded silica with water-alcohol mixtures containing decylamine as the mobile phase was investigated for its applicability to the separation of chlorpromazine, imipramine and their metabolites. The addition of decylamine to the mobile phase was found to be necessary in order to obtain symmetrical peaks. The influence of the decylamine and ethanol concentrations and of the pH of the mobile phase was investigated and these parameters were found to be useful for the adjustment of the retention. The phase system developed was found to be suitable for the required separation. The phase system was applied to the analysis of imipramine and its metabolites, desmethylimipramine and didesmethylimipramine, and desmethylchlorpromazine in human plasma.

Determination of clomipramine or imipramine and their mono-demethylated metabolites in human blood or plasma by high-performance liquid chromatography

A high-performance liquid chromatographic method for the quantitative assay of clomipramine or imipramine and their mono-demethylated metabolites in human blood or plasma is described. After addition of the internal standards, imipramine for clomipramine, desipramine for desmethylclomipramine and conversely, the compounds are extracted from blood or plasma at pH 10 into heptane containing 1% isoamyl alcohol; they are then back-extracted into an acidic aqueous phase and re-extracted at a basic pH into heptane. After evaporation, the residue is dissolved in 300 microliters of mobile phase and 150 microliters is injected. Both drugs and their mono-demethylated metabolites are well separated from the blood or plasma components and the other metabolites on a silica gel column using ethanol--hexane-dichloromethane-diethylamine (30:62:8:5 . 10(-3)) as the mobile phase at a flow-rate of 1.5 ml/min. The limit of sensitivity is 5 ng/ml for clomipramine and imipramine and 10 ng/ml for the corresponding mono-demethylated metabolites. This method has been used to analyse plasma from subjects given therapeutic doses of clomipramine or imipramine.

Determination of amitriptyline-N-oxide, amitriptyline and nortriptyline in serum and plasma by high-performance liquid chromatography

A method for the determination of amitriptyline-N-oxide, amitriptyline and nortriptyline in serum and plasma has been developed. After extraction from serum or plasma the drugs were analysed by high-performance liquid chromatography. The detection limit was 10 ng/ml (2 ml serum or plasma actually used). The coefficient of variation for all three compounds was below 10%. Amitriptyline-N-oxide was found in rat plasma after an oral dose (10 mg/kg) of amitriptyline-N-oxide.

Simultaneous high-performance liquid chromatographic determination of chlordiazepoxide and amitriptyline hydrochloride in two-component tablet formulations

A rapid, precise, and accurate high-performance liquid chromatographic procedure is presented for the stimultaneous determination of amitriptyline hydrochloride and chlordiazepoxide in two-component tablet formulations. The impurities and decomposition products of both components were separated, making the determination specific for amitriptyline hydrochloride and chlordiazepoxide. The method was used for the assay, content uniformity, and dissolution testing of dosage forms containing 5--30 mg of chlordiazepoxide and 12.5--75 mg of amitriptyline.

Separation of drugs by high-performance liquid chromatography with porous polymer resins

The separation of cold drugs and neuroleptics by high-performance liquid chromatogarphy with the porous polymer resin DVB-MCL-O (or 11-30-0), which is a styrene-divinylbenzene-methyl methacrylate copolymer substituted with hydroxymethyl groups, was studied. This copolymer was compared with the commercial porous polymers Hitachi gel 3011, 3011-0 and 3030. A very small theoretical plate height was obtained by using DVB-MCL-O and methanol-ammonia solution (99:1) as the stationary and mobile phases, respectively. This combination was found to be the most suitable for the rapid separation of condensed aromatic ring compounds.

Ion-pair liquid chromatography of steady-state plasma levels of chlorimipramine and demethylchlorimipramine

A method for the determination of chlorimipramine and its metabolite demethylchlorimipramine in the plasma of depressed patients during treatment is described. The method involves extraction of the parent drug, its metabolite and the internal standard from plasma, back-extraction into an acidic aqueous phase and re-extraction into a small volume of organic phase. Separation and quantitation are carried out by ion-pair partition chromatography with UV detection. Accurate determination if possible down to levels of 30 and 60 nmole per liter of plasma for chlorimipramine and the metabolite, respectively, when 1 ml of plasma is used. The coefficient of variation is 7.3% or less at different levels for chlorimipramine and demethylchlorimipramine. Plasma levels of the parent drug and the metabolite measured by this liquid chromatographic method and by a gas chromatographic procedure with electron-capture detection were in good agreement (r = 0.98). The steady-state plasma level of the metabolite was always higher than that of the parent drug in the 34 depressed patients investigated. The mean ratio between the metabolite and the parent drug was 2.7 +/- 1.1 (S.D.) Large inter-individual differences in the levels of the two compounds in patients receiving similar doses were found.

Determination of amitriptyline and some of its metabolites in blood by high-pressure liquid chromatography

Conditions for the determination of amitriptyline and some of its metabolites in serum on a reversed-phase material (C-8) by high-pressure liquid chromatography with UV detection at 254 nm were systematically investigated. The separation of tricyclic antidepressants is best carried out on a phase system consisting of C-8 bonded-phase material as the stationary phase and water--methanol--dichloromethane--propylamine as the mobile phase. The precision and detection limit of the method and the extraction efficiency were established. A chromatogram of a serum extract from a patient treated with amitriptyline is shown. Serum levels of amitriptyline and its four main metabolites (nortriptyline, desmethylnortriptyline, trans-10-hydroxy-amitriptyline and trans-10-hydroxy-nortriptyline) in a patient receiving 150 mg of amitriptyline daily, are reported.

Column liquid chromatography of tricyclic antidepressants

A column liquid chromatographic system for the analysis of tricyclic antidepressants in serum is described. A high separation efficiency can be obtained with a mixture of ethyl acetate, n-hexane and methylamine as eluent on a silica gel column. The retention is easily regulated by varying the concentration of n-hexane, the modifier methylamine and the water content of the ethyl acetate. Examples are given of separation of test mixtures of tricyclic antidepressants and of some of these drugs in serum. UV detection permits determinations down to the 10-ng level in serum.

High-performance liquid chromatographic determination of perphenazine and amitriptyline hydrochloride in two-component tablet formulations

A rapid, precise, and accurate high-performance liquid chromatographic procedure is presented for the simultaneous determination of perphenazine and amitriptyline hydrochloride in two-component tablet formulations. An aliquot of a methanolic extract of the tablet, containing trifluoperazine hydrochloride as an internal standard, is chromatographed on a nitrile bonded phase microparticulate column using a 0.005 M ammonium acetate-methanol (20:80) mobile phase. Quantitation is by peak area. The relative standard deviations for the procedure are 0.34 and 0.54% for the simultaneous determination of perphenazine and amitriptyline, respectively. Eight commercial tablet formulations were analyzed and found to contain 96.5-101.5 and 96.5-103.3% of the labeled amounts of perphenazine and amitriptyline hydrochloride, respectively.

Separation of catecholamines and their metabolites by adsorption, ion-pair and soap chromatography

The separation of catecholamines and their metabolites has been carried out by high-performance liquid chromatography using three systems: liquid-solid adsorption, ion-pair partition, and soap chromatography. In the last newly developed technique a reversed-phase packing is used in conjunction with an aqueous organic eluent containing a detergent. The detergent is chosen so that its ion can form ion-pairs with ions of the solutes. Soap chromatography proved the best technique in terms of column efficiency (giving 3000-5000 plates in 125 mm), resolution and sensitivity of detection. Noradrenaline, adrenaline and dopamine, their 3-O-methyl derivatives, L-3,4-dihydroxyphenylalanine, homovanillic acid and other related compounds could be separated in less than 10 min at the 10-50-ng level on columns whose plate heights were in the range of 20-40 mum. The dependence of retention on the concentration of organic modifier and on detergent concentration for three anionic detergents is reported. The method is applied to the direct analysis of urine and the potential of the method for such analyses, especially of pathological urines is demonstrated. Soap chromatography is likely to enlarge the scope of application of high-performance liquid chromatography to biochemical analysis. It is a powerful method for the separation of ionizable compounds which could replace conventional ion-exchange chromatography.

Bioanalysis of picomole amounts of acetylcholine by ion-pair partition chromatography applied to rat sciatic nerve

A method for determination of acetylcholine in small, discrete biological objects by use of ion-pair technique has been developed. Acetylcholine is extracted as an ion pair with 3,5-di-t-butyl-2-hydroxybenzenesulphonate and separated from co-extracted components by ion-pair partition chromatography with picrate as the counter ion and porous cellulose as support. The quantitative evaluation is made from the acetylcholine peak in the chromatogram obtained by ultraviolet detection. Acetylcholine has been analysed in 1 cm large pieces of rat sciatic nerve containing about 60 pmol (10 ng). The overall recovery of the method is 100 +/- 10% at the 120 pmol level of acetylcholine in a sample.

High-performance ion-pair partition chromatography of sulfa drugs. Study and optimization of chemical parameters

High-performance ion-pair partition chromatography is shown to be a versatile, efficient method for separating sulfonamides. For a group of fourteen sulfa drugs varying widely in pKA and hydrophobicity, the effect of mobile phase composition, counterion composition, pH, and ionic strength on their ion-pair partition chromatographic separation using tetrabutylammonium as the counterion and n-butanol-n-heptane as the mobile phase is shown. Wide variation in k' and a is possible by changing these parameters. Silica columns coated with buffered aqueous solutions of tetrabutylammonium sulfate resulted in efficiencies of 4000-6000 theoretical plates per 25 cm. These columns are stable for long periods of time, and can be stripped and re-used in the adsorption mode with little or no loss in efficiency. Several chromatograms are presented in order to illustrate the performance of ion-pair partition chromatography.

Separation of tetracyclines by high-speed liquid chromatography

The separation of tetracycline and its four commoninpurities has been studied by high-speed liquid chromatography. A preliminary study of the effectiveness of ion-exchange, adsorption, liquid-liquid partition and reversed-phase ion-pair chromatography indicated that only the last method showed promise. By developing special hydrocarbon-bonded stationary phases a rapid and complete resolution of all five tetracyclines has been obtained within 10 min. Plate heights using a derivatised 18-mum partisil are in the range 0.15-0.3 mm. The method can be used to quantify the impurities in tetracycline at around the 1% level.