Quantitation of Meclizine Dihydrochloride in Serum by Reversed Phase Ion Pair High Performance Liquid Chromatography

Abstract

A specific and sensitive HPLC method has been developed for the assay of meclizine dihydrochloride in dog serum using an internal standard technique with a single step extraction. The extracts are injected into a reversed phase ion pair HPLC system using a solvent containing camphorsulfonate as paring anion. The detection limit is 5 ng/ml and the range of linearity is 5–250 ng/ml. The method has been used to quantitate meclizine dihydrochloride levels in bioavailability and pharmacokinetic studies in dogs.     

Ion-Paired Liquid Chromatographic Method for the Analysis of Pyridostigmine in Plasma

Abstract

A high performance Liquid chromatographic (HPLC) procedure for the analysis of pyridostigmine in plasma has been developed. Only 0.5 ml of plasma is required for the analysis. The clean-up procedure involves a protein precipitation step and a column elution step prior to separation by HPLC. The assay is quite sensitive with a detection limit of 1.37 ng/ml for pyridostigmine in plasma. Variability of results ranged from 3 to 14% on evaluations of assay precision. Accuracy of results, evaluated using blind samples in the range of 0–50 ng/ml, differed between 6 and 12% from blind sample values. Stability was also determined for pyridostigmine in plasma at ?20°C and ?80°C. The results showed no degradation for pyridostigmine at ?80°C for up to four months. In a preliminary study with one human volunteer, the drug could be detected up to 12 hours following oral syrup solution doses of between 0.4 and 0.9 mg/kg. This assay is suitable for pharmacokinetic studies involving pyridostigmine in human subjects.     

Separation and Quantitation of Urinary Phthalates by HPLC

Abstract

A method was developed for the separation and quantitation of plasticizers and their metabolites from human urine using HPLC, Urine was diluted with an equal volume of water and extracted at pH 2.0 with diethyl ether, The extract was dried, the solvent vacuum stripped, and the residue dissolved in methanol for injection into the chromatograph. A C₁₈ reverse phase column containing 10 μ particles was used for the analysis. Ionic suppression, 0.5% acetic acid in water, at pH 3.0 was used to resolve the acidic components. A step gradient of acetonitri1e:water (containing acetic acid) was used to elute the polar metabolites as well as the non-polar plasticizers. Mass spectrometry was used t o identify the compounds in the HPLC fractions. From the HPLC fractions of the urine extract collected, phthalic acid, MEHP, DEHP and normal urinary constituents (e.g., hippuric and benzoic acid derivatives) were identified     

Liquid Chromatographic Method for Determination of Free and Niosome‐Entrapped Nimodipine in Mouse Plasma and Different Tissues

Abstract

A rapid HPLC method for the quantification of nimodipine in mouse plasma and tissues has been developed in this study, with simple procedure of sample preparation by one‐step protein precipitation. The results of HPLC analysis indicated that linear calibration curves were obtained over the concentration range 0.10–10.00 µg/ml for plasma, 0.10–20.00 µg/g for heart, liver, spleen, kidneys, and brain, and 1.00–200.00 µg/g for lung, respectively. The desirable precision and accuracy were achieved, both intraday and interday for plasma and tissue homogenates. Thus, this newly developed procedure was successfully applicable for determination of nimodipine in mouse plasma and tissues following intravenous administration of free and novel niosome‐entrapped nimodipine.     

Liquid Chromatographic Analysis of Pentobarbital

Abstract

A method is described for a one step acetonitrile precipitation of serum or plasma and subsequent analysis of pentobarbital by reverse phase HPLC. The results of using two internal standards, N,N-Diethyl-m-toluamide and 5-(p-Methylphenyl)-5-phenylhydantoin are compared. Internal standard is added to serum (as little as 25 μL) and vortex-mixed with acetonitrile followed by centrifugation. An aliquote of the supernatant is analyzed on a C18 reverse phase column eluted with metanol/0.05 M (NH₄)₂HPO₄, pH 8/water (55/20/25, v/v/v). The effluent is monitored at 220 nm.     

Single Step Purification of a Synthetic Peptide Fragment of Neurofilaments by Preparative High Performance Liquid Chromatography

Abstract

It was recently shown that fragment Lys-Ser-Pro-Val (1,2) is the major site in vivo neurofilament phosforilation. A suitable method for the preparation of this peptide was therefore studied paying particular attention to the purification step. Even thought solubility of this peptide in methyl t-butil ether does not allow the standard purification. It is possible achieve a good separation in a single step by HPLC, after a simple extraction with acidic water.     

Extraction of Anthracyclines from Biological Fluids for HPLC Evaluation

Abstract

A new technique for the extraction of anthracyclines and their metabolites from plasma or serum is described, which gives suitable extracts for HPLC analysis of these drugs in patients. This technique consists in a very rapid chromatographic step on the bonded silica contained in small open columns (C-18 Sep-Paks, Waters Associates). This extraction gives quantitative recoveries of all the anthracyclines and metabolites that have been tested; 0.2 to 3 ml of plasma can be processed, with concentrations up to 5,000 ng/ml. The advantages of this technique over classical techniques using an organic extraction with a partition between two phases are: speed, simplicity, efficacy, reproducibility and similarity of recoveries for various anthracyclines.     

Trace Analysis by Microbore HPLC

Abstract

The potential and problems of trace analysis by microbore HPLC with on-column concentration and the benefits of additional column-switching in several modes are discussed.

An example of the performance of an on-column concentration column-switching microbore HPLC system is shown.     

High-Performance Liquid Chromatographic Determination of Trace Quantities of Azinphos Methyl and Azinphos Methyl Oxon in Various Water Sources by Direct Injection and Trace Enrichment

Abstract

A high-performance liquid chromatographic (HPLC) method is described for the determination of trace amounts of the organophosphate insecticide, azinphos methyl and its degradation product, azinphos methyl oxon, by direct injection and by trace enrichment. The compounds were analyzed on a uBondapak C₁₈ column with UY detection at 224 nm. The mobile phase for the analysis was acetonitrile-water (50:50) at a flow rate of 1.3 ml/min. Ten minutes were required for the chromatographic analysis. Water from three sources, public water supply, stream, and ocean was analyzed for azinphos methyl and azinphos methyl oxon at concentrations as low as 11.9 and 11.3 ppb, respectively, without a clean-up, concentration or derivatization step. Azinphos methyl was quantitated at 0.29 ppb and azinphos methly oxon at 0.29 ppb by employing a concentration step involving a C₁₈ Sep-Pak cartridge. The coefficients of variation for all determinations ranged from 0.77 to 9.06%. Peak heights were used for quanti-tation. Several other pesticides have been shown not to interfere with the analysis of either compound.     

The Use of HPLC/Thermospray Ms for the Confirmation of Aflatoxins in Peanuts

Abstract

An HPLC/Thermospray MS method is described for the determination of aflatoxins B₁, B₂, G₁ and G₂ in peanut extracts. Samples are extracted and prepared for analysis using an SPE method. The final determination utilizes reversed phase HPLC with a thermospray MS detector. The use of the MS allowed for unequivocal identification of aflatoxins in the extracts.     

Analysis of Tetracycline,Oxytetracycline and Chlortetracycline in Plasma Extracts by Electrospray Tandem Mass-Spectrometry and by Liquid Chromatography

Abstract

Pure standards of tetracyclines (tetracycline, oxytetracycline and chlortetracycline) have been analyzed on a triple quadrupole mass spectrometer with Atmospheric Pressure Chemical Ionization (APCI) and Electrospray Ionization (ESI). ESI appeared to be considerably more sensitive than APCI. Collisional activation of the MH⁺ ions gave fragment ions at m/z values equal to MH⁺ - 35 which corresponds to loss of both H₂O and NH₃. The collisionally induced loss of 35 from MH⁺ was used in developing a mass spectrometric method based on loop injection and selected reaction monitoring (SRM) as the final analytical step. The method was tested on extracts from fortified plasma and the measurements from the MS-MS analysis were compared with results from High Performance Liquid Chromatography (HPLC) analysis of the same samples. The fortified plasma (from pig) samples were purified by chelate affinity chromatography (amberlite XAD columns). After filtration and evaporation of the solvent the redissolved residues were analyzed by HPLC and by MS-MS with ESI. The HPLC eluates (gradient of 0.01 M aqueous oxalic acid and CH₃CN) were monitored at 356 and 369 nm. The signal to noise ratio in the analyses of extracts from plasma fortified to 20 ppb suggests a detection limit for the MS-MS method below 10 ppb of tetracylines in plasma.     

A New Method for the HPLC Analysis of Pt(II) in Urine

Abstract

An analytical method has been developed to measure Pt(II) in urine via derivatization and UV or HPLC analysis. A measured quantity of urine is heated briefly with diethyl ammonium diethyl-dithiocarbamate, and the resulting Pt(Et₂NCS₂)₂ is extracted into a measured volume of chloroform. Concentrations of Pt(II) are determined by UV absorption at 346 nm or by reverse phase HPLC analysis. The detection limit for Pt(II) as its dithiocarbamate is ～ 1 ng by HPLC; the concentration limit for HPLC analysis by direct extraction was ～ 25 ng/ml. Chromatographic response was linearly related to Pt(II) concentration over the range 100-4, 000 ng/ml; dilution of more concentrated samples has extended this range to at least 30, 000 ng/ml. This method has been applied to the analysis of Pt(II) in the urine of patients who have received cis-dichlorodiamniineplatinum(II) (CDDP) chemotherapy.     

Chromatography of Trichothecene Mycotoxins

Abstract

Trichothecene mycotoxins occur in agricultural commodities and can cause problems from feed refusal to death in animals. This paper describes chromatographic methods for selective analysis for trichothecene mycotoxins. These methods include gas chromatography (GC), thin layer chromatography (TLC), and high pressure liquid chromatography (HPLC). The trichothecene analysis methods by GC and TLC are shown to have a greater sensitivity than in HPLC for the underivatized mycotoxins.     

Simultaneous Analysis of Cimetidine and Ranitidine in Human Plasma by HPLC

Abstract

A rapid method for the simultaneous quantitation of the H₂-receptor antagonist drugs cimetidine and ranitidine in human plasma by isocratic ion-pair reverse-phase HPLC is described. The method involves a simple organic extraction step of the alkalinized plasma containing added internal standard followed by back extraction of the extract with dilute acetic acid and subsequent analysis of the aqueous acidic phase on a reverse-phase (C18) column. The eluting solvent was acetonitrile-water (20:80 v/v) containing 0.005 mole/litre octanesulphonic acid and was monitored at 229 nm. The run time for the assay was 12.5 minutes, with a detection limit for cimetidine of 50 ng/m1/(0.2 μmole/1) and that for ranitidine was 20 ng/ml (0.06 umole/1).     

A Study On Air Pollution by Asphalt Fumes

Abstract

A TLC/HPLC procedure for the determination of polycyclic aromatic hydrocarbons (PAH), occuring in asphalt fumes (adsorbed on particular matter), is described. The method is based on extraction of asphalt fume particles, collected on glass fibre filters, using CCK₄. Following a clean up step by the aid of a TLC procedure on Al₂ O₃ thinlayer plates, using a mixture of cyclohexane/acetone/ether as the mobile phase. Under UV-light, occuring PAH are indicated as fluorescent spots. A separation of the collected PAH into individual components and their identification is performed by the aid of a HPLC procedure. Futher-more, an approach was made to verify the separated PAH by their fluorescence spectra and their mass spectra.     

Liquid Chromatographic Analysis of Ciprofloxacin and Ciprofloxacin Metabolites in Body Fluids

Abstract

An isocratic HPLC assay procedure for analysis of ciprofloxacin and three metabolites was developed. The procedure requires only dilution of bile, saliva, and urine samples prior to reverse-phase chromatography on a polystyrene-divinylbenzene (PSDVB) column; analysis of serum samples requires a cleanup step on a PSDVB cartridge prior to chromatography. The dependence of chromatographic efficiency on flow rate and temperature was investigated and the accuracy, precision, selectivity, and sensitivity of the procedure were evaluated. The developed procedure was also compared to a modified version of a published ciprofloxacin procedure that requires an octadecyl-silane (ODS) column for chromatographic separation. Similar efficiency, precision, and accuracy were observed with both procedures and both were used for analysis of clinical samples. However, the procedures were used for different purposes. The PSDVB procedure, because of more favorable column selectivity, was used to assay ciprofloxacin and its metabolites in bile, urine and saliva samples. The ODS procedure, because of a simpler serum preparation step, was used t o assay ciprofloxacin in serum samples.     

Application of Thin Layer,Ion Exchange and High Performance Liquid Chromatography to Separate Pharmacologically Active Components of an African Arrow Poison of Plant Origin

Abstract

We have applied thin layer chromatography (TLC), ion exchange chromatography (IEC) and, high performance liquid chromatography (HPLC) to separate and identify the pharmacologically active components of an african arrow poison of plant origin. On the basis of Rf values obtained from TLC, the active components of the toxin are unlike d-tubocurarine, atropine and, scopolamine. Dowex 1 × 2 IEC of 630 mg of crude toxin on a 2.5″ × 33″ column with step gradient elution (NaCl, 0.1 - 1. OM and NaOH, 0.1M) led to the identification of three distinct peaks. When the components of each of the three peaks were subjected to HPLC, the results confirmed the homogeneity of each of the isolated peaks except for the third peak which was a doublet.     

HPLC Separation of Tautomeric Compounds of 4-Aminoisoxazolyl-1,2-naphthoquinones. II

Abstract

HPLC separations and quantitative analysis are described for a mixture of 4-aminoisoxazolyl-1,2-naph-thoquinone isomers. This assay is simple, rapid and stability indicating because the precursors and isomerization products can be monitored simultaneously. The results obtained are in agreement with those obtained by UV spectroscopy.     

Simplified Approach to HPLC Precolumn Fluorescent Labeling of Carbohydrates: N-(2-Pyridinyl)-glycosylamnes

Abstract

Reducing sugars were fluorescently labeled by condensation with 2-aminopyridine. The reaction was quantitative and the product was sufficiently stable so that a subsequent reduction step (as in reductive amination) proved unnecessary. The products have been characterized as N-(2-pyridinyl)-glycosylamines. Oligosaccharides labeled in this manner exhibit important analytical characteristics. They: a) are stable under both HPLC separation and prolonged storage; b) have improved chromatographic resolution; c) regenerate original material by weak acid hydrolysis.     

Anti-Hormonal Agents. V. HPLC of Anordrin

Abstract

Procedures are described for the reverse phase HPLC analysis of the contraceptive A-nor steroid Anordrin, including the separation of its alpha- and beta-isomers, present in formulated tablets (Chinese Vacation pill).