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PubMed2005

Development and validation of a selective and robust LC-MS/MS method for quantifying amlodipine in human plasma.

A liquid chromatographic-tandem mass spectrometric method (LC-MS/MS) for quantifying amlodipine in human plasma was developed and validated. Sample preparation was based on liquid-liquid extraction using NaOH and a mixture of ethyl acetate/hexane (80/20; v/v). Chromatography was performed on a C-18 analytical column and the retention times were 1.9 and 3.0 min for amlodipine and nimodipine (internal standard), respectively. The ionization was optimized using ESI(+) and enhanced selectivity was achieved using tandem mass spectrometric analysis via two MRM functions, 409 --> 238 and 418 --> 343 for amlodipine and nimodipine. The calibration curve ranged from 0.2 to 20.0 ng/mL. The inter-day precision and accuracy and the relative standard deviation (RSD) were <15%. The analyte was shown to be stable over the time-scale of the whole procedure. The robustness of the method was demonstrated by the good reproducibility of the results obtained during the analysis of clinical samples.

Amlodipine↗
PubMed1980

Review of the 4-hexylresorcinol procedure for acrolein analysis.

The purpose of this paper is to present laboratory results showing major problems with the 4-hexylresorcinol method used for acrolein analysis. A discrepancy in the analytical procedure described by ASTM and NIOSH gives rise to underestimation of acrolein levels based on the length of time the mixed reagents have been prepared prior to sampling. Underestimations by as much as 35% may occur due to the problems in the existing methodologies.

Acrolein↗
PubMed1999

Systematic toxicological analysis procedures for acidic drugs and/or metabolites relevant to clinical and forensic toxicology and/or doping control.

This paper reviews systematic toxicological analysis (STA) procedures for acidic drugs and/or metabolites relevant to clinical and forensic toxicology or doping control using gas chromatography, gas chromatography-mass spectrometry, liquid chromatography, thin-layer chromatography and capillary electrophoresis. Papers from 1992 to 1998 have been taken into consideration. Screening procedures in biosamples (whole blood, plasma, serum, urine, vitreous humor, brain, liver or hair) of humans or animals (horse, or rat) are included for the following drug classes: angiotensin-converting enzyme (ACE) inhibitors and angiotensin II (AT-II) blockers, anticoagulants of the 4-hydroxy coumarin type, barbiturates, dihydropyridine calcium channel blockers (calcium antagonists), diuretics, hypoglycemic sulfonylureas and non-steroidal anti-inflammatory drugs (NSAIDs). Methods for confirmation of preliminary results obtained by screening procedures using immunoassay or chromatographic techniques are also included. Furthermore, procedures for the simultaneous detection of several drug classes are reviewed. The toxicological question to be answered and the consequences for the choice of an adequate method, the sample preparation and the chromatography itself are discussed. The basic information about the biosample assayed, work-up, separation column, mobile phase or separation buffer, detection mode and validation data of each procedure is summarized in 16 tables. They are arranged according to the drug class and the analytical method. Examples of typical applications are presented. Finally, STA procedures are reviewed and described allowing simultaneous screening for different (acidic) drug classes.

Chromatography↗
PubMed2006

[Simultaneous determination of ephedrine and chlorpheniramine in human plasma by a highly sensitive liquid chromatography-tandem mass spectrometric method].

AIM: To develop and validate a liquid chromatography-tandem mass spectrometric (LC/MS/MS) method for the simultaneous quantification of ephedrine and chlorpheniramine in human plasma after oral administration of a compound preparation. METHODS: The analytes and the internal standard, diphenhydramine, were isolated from plasma by protein precipitation with methanol, then chromatographied on a Zorbax SB-C18 column (150 mm x 4.6 mm ID) using a mobile phase consisted of methanol-water-formic acid (80: 20: 0.5, v/v), at a flow rate of 0.5 mL x min(-1). A tandem mass spectrometer equipped with electrospray ionization source was used as detector and was operated in the positive ion mode. Selected reaction monitoring (SRM) using the precursor to produce ion combinations of m/z 166-->115, m/z 275-->230 and m/z 256-->167 were used to quantify ephedrine, chlorpheniramine and the internal standard, respectively. Results The linear concentration ranges of the calibration curves for ephedrine and chlorpheniramine were 0.50 - 200 microg x L(-1) and 0.050 - 20.0 microg x L(-1), respectively. The lower limits of quantification were 0. 50 microg x L(-1) for ephedrine and 0.050 microg x L(-1) for chlorpheniramine, individually. The intra- and inter-day relative standard deviation (RSD) across three validation runs over the entire concentration range was less than 9.3% for both ephedrine and chlorpheniramine. The inter-day accuracy (RE) was within +/- 3.4% for the analytes. Each sample was chromatographied within 3.3 min. The method was successfully used in pharmacokinetics study of ephedrine and chlorpheniramine in human plasma after oral administration of a compound preparation containing 5 mg ephedrine hydrochloride, 1 mg chlorpheniramine maleate, 50 mg phenytoin, 12.5 mg theophylline, 12.5 mg theobromine and 7.5 mg caffeine. No interaction among the six components was observed on their pharmacokinetic parameters. CONCLUSION: The method was proved to be highly sensitive, selective, and suitable for pharmacokinetics investigations of different compound preparations containing low dosage of both ephedrine and chlorpheniramine.

Administration, Oral↗
PubMed2004

Simultaneous analysis of gamma-hydroxybutyric acid and its precursors in urine using liquid chromatography-tandem mass spectrometry.

We have developed a rapid method that enables the simultaneous analysis of gamma-hydroxybutyrate (GHB) and its precursors, i.e. gamma-butyrolactone (GBL) and 1,4-butanediol (1,4-BD) in urine. The method comprised a simple dilution of the urine sample, followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Chromatographic separation was achieved using an Atlantis dC18 column, eluted with a mixture of formic acid and methanol. The method was linear from 1-80 mg/L for GHB and 1,4-BD and from 1-50 mg/L for GBL. The limit of quantification was 1 mg/L for all analytes. The procedure, which has a total analysis time (including sample preparation) of less than 12 min, was fully validated and applied to the analysis of 182 authentic urine samples; the results were correlated with a previously published GC-MS procedure and revealed a low prevalence of GHB-positive samples. Since no commercial immunoassay is available for the routine screening of GHB, this simple and rapid method should prove useful to meet the current increased demand for the measurement of GHB and its precursors.

Chromatography, High Pressure Liquid↗
PubMed2006

Application of microbore HPLC in combination with tandem MS for the quantification of rosuvastatin in human plasma.

The potential of microbore high-performance liquid chromatography (HPLC) in combination with tandem mass spectrometry (MS/MS) for the sensitive detection of rosuvastatin (Crestor) in human plasma was investigated. Three microbore HPLC columns with internal diameters (i.d.) of 0.5, 1.0 and 2.0 mm were evaluated for column efficiency and mass sensitivity, and compared to a conventional 4.6 mm i.d. column. The 2.0 and 1.0 mm i.d. columns performed very well while the 0.5 mm i.d. column was slightly less efficient, this is probably due to a lower packing density. Good results with respect to gains in mass sensitivity compared to the conventional analytical column were achieved with the 2.0 and 1.0 mm columns. Thus, the 2.0 mm i.d. column had an improved signal-to-noise (S/N) ratio of 16 whilst the 1.0 mm i.d. column had an improved S/N ratio of greater than 70. Experiments with the 1.0 mm i.d. HPLC column were performed to determine the robustness of the microbore method for human plasma extracts after sample preparation using solid-phase extraction (SPE). A number of problems were encountered with extracts including high backgrounds, the blocking of the column and a rapid deterioration in column performance. The blocking of the column by particulates was solved by off-line filtration of the sample extracts. Peak tailing of the analytes and high background, both of which were due to endogenous interferences in the extracts, were eliminated using gradient elution. Using these approaches over 500 injections of plasma extracts were achieved without significant deterioration in assay performance. Quantities of rosuvastatin of 0.3 pg on-column could be detected and cross-validation experiments demonstrated that the conventional and the microbore HPLC-MS/MS methods provided similar information on the concentration of rosuvastatin but with greatly reduced sample consumption using the microbore method.

Chromatography, High Pressure Liquid↗
PubMed2006

Liquid chromatographic/tandem mass spectrometric method for the quantitation of tranilast in human plasma.

An analytical method for the determination of tranilast in human plasma using tramadol as the internal standard has been developed based on liquid chromatography/tandem mass spectrometry. Sample preparation involved protein precipitation with methanol. Separation by reversed-phase high-performance liquid chromatography using methanol/10 mM ammonium acetate (70: 30, v/v) as mobile phase was complete in a run time of 2.4 min. Detection on a Q TRAP system used multiple reaction monitoring. The method was linear in the range 0.06-20 microg/mL with intra- and inter-day precisions (as relative standard deviation) of 2.2-2.6% and 2.3-2.9%, respectively. Accuracy (as relative error) was <-2.5%. The method was applied in a pharmacokinetic study in healthy volunteers treated with a single 80 mg oral dose of tranilast.

Administration, Oral↗
PubMed2002

Speciation of nitrogen - [N(3-)] and [N(2)(2-)] - in binary compounds.

The nitrogen content of the binary compounds SrN = Sr(4)[N](2)[N(2)], Sr[N(2)], and Ba[N(2)] (prepared by high-pressure syntheses) was determined analytically by using the carrier gas hot extraction method. For handling of the air- and moisture-sensitive samples, a transfer chamber was constructed to protect the compounds against decomposition before being analyzed. Additionally, it was necessary to develop a method allowing controlled and variable heating of the electrode furnace to get analytical results with high precision and accuracy. By means of a suitable temperature program it was possible not only to verify the existence but also to quantify the two different nitrogen species ([N(3-)] and [N(2)(2-)]), and thus confirm the results of recent neutron diffraction studies.

Journal Article↗
PubMed2005

Study on the stability of noradrenaline and on the determination of its acidity constants.

Noradrenaline is a catecholamine which has been largely recognised to play a very important role in biological systems. In view of the neurotransmitter's alleged importance, this work aimed at showing the influence of time on its spectral behaviour using different analytical methods and determining its acidity constants through spectrophotometric titration and by the so-called point-by-point analysis, where the samples are freshly prepared for each pH value investigated at the instant required. Because the catecholamines are light-sensitive and likely to react with the oxygen in the surrounding air, both methods used preclude its incidence onto the samples being analysed under the presence of a nitrogen atmosphere maintained over the solutions. The constants obtained through point-by-point analysis were log beta1 = 30.71+/-0.16, log beta2 = 22.00+/-0.15 and log beta3 = 11.69+/-0.16.

Acids↗
PubMed1999

Development and validation of a reversed-phase liquid chromatographic method for analysis of estradiol valerate and medroxyprogesterone acetate in a tablet formulation.

A simple and accurate liquid chromatographic method was developed for estimation of estradiol valerate and medroxyprogesterone acetate in pharmaceuticals. Drugs were chromatographed on a reverse phase C18 column, using a mixture (30:70) of ammonium nitrate buffer and acetonitrile and eluants monitored at a wavelength of 280 nm. Solution concentrations were measured on a weight basis to avoid the use of an internal standard. The method was statistically validated for its linearity, accuracy, precision and selectivity. Due to its simplicity and accuracy, the authors believe that the method may be used for routine quality control analysis. It does not require any specific sample preparation except the use of a column guard before the analytical column and suitable prefilter attached to the syringe prior to injection.

Calibration↗
PubMed1979

The quantitative analysis of 1-alpha-acetylmethadol and its principal metabolites in biological specimens by gas chromatography-chemical ionization-multiple ion monitoring mass spectrometry.

1-alpha-acetylmethadol (LAAM) is a new drug under development for the treatment of heroin dependence. A new analytical method applicable to the accurate biodispositional study of the drug and its metabolities is described and critically discussed in this report. The procedure involves sample preparation and direct organic solvent extraction using eta-butyl chloride, amide derivatization by molecular rearrangement, and gas chromatography-chemical ionization mass spectrometry-selected ion monitoring, with methane as the carrier and ammonia as reagent gases. Deuterated (d3 stable isotopes of LAAM and its metabolites are used as internal standards. The method is free from qualitative interferences and has quantitative sensitivity to 5 ng/ml for 2.0 ml samples with 10-15% accuracy and precision in the range 5-100 ng/ml; and 2-5% at concentrations up to 750 ng/ml. Specimens of plasma, whole blood, urine, bile, brain, liver, and other visceral samples have been successfully analyzed, as well as in vitro preparations such as hepatic microsomes. By appropriate data processing, the method lends itself to routine analysis and high volume work; even manually the method is capable of at least 50 samples per week. A simplified procedure for the analysis of LAAM and its metabolites in urine only is also presented and discuet up and use the methods.

Bile↗
PubMed1974

Rapid method for detection and enumeration of fecal coliforms in fresh chicken.

A rapid method for enumerating fecal coliforms in foods was developed employing an agar pour-plate medium. After 7 h of incubation at 41.5 +/- 0.05 C, this medium effectively allows the growth of fecal coliforms only. This rapid method was compared with the Association of Official Analytical Chemists multiple-tube dilution method for Escherichia coli, by using 21 samples of fresh, cut-up chicken and a surface rinsing procedure for sample preparation. Verification of picked colonies was carried out in EC broth using parallel incubation temperatures of 45.5 and 44.5 +/- 0.05 C. Verifications for these temperatures averaged 79 and 98%, respectively. All positively verified isolates were E. coli types I and II, as were the negatives. Geometric means for the verified 7-h plate count were within 12% of the standard means for both EC broth incubation temperatures.

Animals↗
PubMed1989

[Simultaneous qualitative and quantitative analysis of mixtures by multivariate spectrophotometry].

By the use of stepwise regression method in conjunction with the theory of figures of merit for the multicomponent spectrophotometry, mixtures with known scope of possibly present species can be simultaneously analyzed qualitatively and quantitatively. There is no need for the analysis to acquire the spectral data matrix from a series of mixture samples with varied concentration as for the case of target transformation factor analysis. Analytical results can be obtained from the spectral data vector of just one assayed sample. The method has been testified by analyzing synthetic mixtures and pharmaceutical preparations with satisfactory results.

Amino Acids↗
PubMed2006

Three-layer matrix/sample preparation method for MALDI MS analysis of low nanomolar protein samples.

A robust and sensitive sample preparation method is presented for matrix-assisted laser desorption ionization (MALDI) mass spectrometric analysis of low nanomolar concentrations of proteins containing high amounts of common salts and buffers. This method involves the production of densely packed sub-micrometer matrix crystals by depositing a matrix solution on top of a matrix seed-layer prepared on a MALDI target. A sub-microliter aliquot of analyte solution is then directly added to the top of the matrix crystals to form a thin-layer. alpha-Cyano-4-hydroxycinnamic acid (4-HCCA) is used as matrix and demonstrated to give better performance than other commonly used matrices, such as 2,5-dihydroxybenzoic acid (DHB), 2-(4-hydroxy-phenylazo) benzoic acid (HABA), or sinapinic acid. This three-layer method is shown to be superior to the other MALDI sample preparation methods, particularly for handling low nanomolar protein solutions containing salts and buffers.

Animals↗
PubMed2006

Determination of ganciclovir in different matrices from solid organ transplanted patients treated with a wide range of concomitant drugs.

The aim of the present study was to develop a time-efficient chromatographic method for the analysis of therapeutic concentrations of ganciclovir (GCV) in plasma, urine as well as dialysate (from continuous renal replacement therapy) from solid organ transplant recipient treated with either GCV or its prodrug valganciclovir (VGCV) in combination with a wide variety of other concomitant drugs. Sample preparation was performed by reversed phase solid phase extraction and was followed by separation of the analytes on a reversed phase column using isocratic elution with a mobile phase consisting of acetonitrile-a counter ion (50 mM 1-heptanesulfonic acid) in an aqueous sodium dihydrogen phosphate buffer (pH 2.1; 10 mM) (10:90 v/v) and a fluorescence detector. Validation of the method showed linearity within the concentration range of 0.1-40 microg/mL for plasma and 0.1-120 microg/mL for urine and dialysate (R(2)>0.99, n> or =5). Accuracy and precision (evaluated at 0.1, 5 and 40 microg/mL) were both satisfactory. The LLOQ was determined to be 0.1 microg/mL. The method was successfully applied on clinical samples from renal transplant recipients treated with VGCV in combination with a variety of usually used concomitant drugs for solid organ transplant recipients.

Antiviral Agents↗
PubMed2006

Selective sample preparation with bioaffinity columns prepared by the sol-gel method.

Bioaffinity materials prepared by entrapping highly selective bioligands in the pores of a sol-gel glass offer unique advantages for the clean-up of complex sample matrices. The inclusion of sol-gel bioaffinity columns frequently allows the efficient elimination of interfering matrix components and enrichment of analytes in a simple step. After introducing the basic principles the paper reviews the methods for the production of protein-doped sol-gel materials and discusses the characteristics of sol-gel affinity columns by comparing their stability, selectivity, binding capacity and reusability. The potential of sample clean-up with sol-gel affinity columns is demonstrated giving applications in environmental, food and clinical analysis.

Chromatography, Affinity↗
PubMed2001

A validated liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry method for quantitation of cocaine and benzoylecgonine in human plasma.

In order to support studies on various medication protocols for the treatment of cocaine abuse, an accurate, precise, and sensitive (2.5 to 750 ng/mL) liquid chromatography-tandem mass spectrometry assay was developed to determine cocaine and benzoylecgonine in human plasma. Cocaine-d3 and benzoylecgonine-d3 were added as internal standards and samples were subjected to solid-phase extraction. Cocaine recovery was 94.4% and benzoylecgonine was 80.3% at 2.5 ng/mL. The selected reaction monitoring of parent ions at m/z 304 and 290 resulted in strong fragments at m/z 182 and 168 for cocaine and benzoylecgonine, respectively. The method was fully validated. The mean measured concentration at the 2.5 ng/mL, the lower limit of quantitation, was within 10.8% of the target and the precision determined at the low (5 ng/mL), medium (50 ng/mL), and high (650 ng/mL) quality controls ranged from 0.9 to 6.2 %CV. Cocaine and benzoylecgonine concentrations in plasma treated with 1% NaF showed changes of less than 10% when maintained at room temperature for up to 7 h and no significant changes when subjected to three freeze-thaw cycles. The concentrations of cocaine and benzoylecgonine remained stable in plasma samples stored at -20 degrees C for up to 11 months. Methanolic stock solutions of both analytes are stable, staying within 2% of the freshly prepared stock solutions, when stored at -20 degrees C for up to 235 days. Both extracted analytes reconstituted in methanolic solutions are stable for up to seven days whether stored at -20 degrees C or at room temperature on the autosampler. The method is rugged, rapid, and robust and has been applied to the batch analysis of more than 700 samples during pharmacokinetic profiling to assess potential interactions between intravenous (i.v.) cocaine challenge and treament medications. Results from three of these subjects receiving 40 mg (i.v.) cocaine demonstrate the utility of the method.

Adolescent↗
PubMed2006

Applicability of capillary electrophoresis to the analysis of trace rare earth elements in geological samples.

This study developed a methodology to analyze trace rare earth elements (REEs) in geological materials by capillary electrophoresis (CE). Changed from dilute HNO3 into a water medium by heating, REE ions are detectable at approximately 2 ng mL(-1). In the presence of coexisting elements from geological samples, REE separations were carried out. After sample fusion with Na2O2 and interference separation with ammonium pyrrolidinedithiocarbamate chelate, REE analytes were coprecipitated with Mg(OH)2 at pH 8.5, and then prepared into a water medium for CE determination. Using the standard addition method, this protocol was validated by analyses with better than 5% precision. This method was applied to geological materials; the REE results are in consistence with their certified values. With electrokinetic injection, internal standard (IS) selected among lanthanides is a prerequisite of high-quality REE data. An approach was proposed to derive the IS content for further correcting its contribution from unknown samples.

Journal Article↗