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PubMed1995

Quantitative chromatographic analysis of inositol phospholipids and related compounds.

The metabolism of phospholipids and the mobilization of second messengers such as inositol-1,4,5-trisphosphate, 1,2-diacylglycerol (DAG) and arachidonic acid (AA) from phospholipids is commonly studied by radiolabelling phospholipids with [3H]myo-inositol or [32P]ATP and measuring the incorporation of radioactivity in different phospholipids or their hydrolysis products. However, for the radiolabelling method to accurately reflect changes in the compound's mass, it is essential that the tissue is labelled to isotopic equilibrium which is difficult to achieve. To circumvent the disadvantages of the radiolabelling method, several analytical procedures have been developed for the mass analysis of phospholipids and inositolphosphates (IPs). Quantitation of the mass or the radiolabelling of phospholipids is a complex multi-step procedure that involves quantitative isolation of phospholipids, fractionation of individual phospholipids and either determination of radioactivity in each component or the measurement of their mass. Phospholipids, DAG and AA are extracted from tissue sample with organic solvents such as chloroform-methanol (2:1) containing HCl or formic acid. The extract is separated by TLC, cartridge-column chromatography or HPLC on a reversed-phase column. Phospholipids are quantitated by measuring inorganic phosphate, absorption at 200 nm or mass spectrometry. Inositol phosphates are extracted with perchloric acid or trichloroacetic acid and separated by ion-exchange cartridge-column or HPLC with an ion-exchange column. IPs are quantitated by measuring inorganic phosphate or by using enzymatic reaction, metal-dye coupling, NMR or mass spectrometry.

Arachidonic Acid↗

PubMed2004

Liquid chromatography-tandem mass spectrometry method for the determination of tranexamic acid in human plasma.

A new method for the determination of tranexamic acid (TA) in human plasma using high performance liquid chromatography with tandem mass spectrometric detection was described. TA and the internal standard, methyldopa, was extracted from a 200 l plasma sample by a one-step deproteination using perchloric acid. Chromatographic separation was performed on an Xtrra MS C18 Column (2.1 mm x 100 mm, 3.5 microm) with the mobile phase consisting of 10% acetonitrile in 2 mM ammonium acetate buffer (pH 3.5) at a flow rate of 0.15 ml/min. The total run time was 5 min for each sample. Detection and quantitation was performed by the mass spectrometer using the multiple reaction monitoring of the precursor-product ion pair m/z 158 --> 95 for TA and m/z 212 --> 166 for methyldopa, respectively. The method was linear over the concentration range of 0.02-10.00 g/ml with lower limit of quantification of 0.02 microg/ml for TA. The intra- and inter-day precision was less than 11% and accuracy ranged -10.88 to 11.35% at the TA concentrations tested. The present method provides a relatively simple and sensitive assay with short turn-around time. The method has been successfully applied to a clinical pharmacokinetic study of TA in 12 healthy subjects.

Calibration↗

PubMed2000

Determination of superabsorbent polyacrylate dust in workplace atmospheres after derivatization with ethanol and using HPLC with pulsed electrochemical detection.

Superabsorbent polyacrylates (SAPs) have been used in the hygiene industry for many years. A derivatization and analytical method was developed for routine analysis of trace levels of SAP dust in workplace atmospheres. In comparison with existing methods, which are based on the sodium content or the ion exchange properties of the polymer, this method is more specific. It has the advantage of not being influenced by any sodium containing contaminants. Air samples are collected on Teflon filters using air monitoring sampling cassettes. The filters are subsequently placed in quartz vials and a reaction mixture containing hydrochloric acid in ethanol is added. The hydrochloric acid-ethanol solution, when heated, converts the carboxylic acid groups on the backbone of the insoluble polyacrylate into ethyl esters. After reaction, the excess of ethanol and hydrochloric acid is completely removed under vacuum. The sample is then treated with aqueous sodium hydroxide at 80 degrees C to release the bound ethanol. The solution is analyzed by HPLC on an anion exclusion stationary phase using dilute perchloric acid as mobile phase. Ethanol is identified and quantified with a pulsed electrochemical detector. Several environmental samples in addition to laboratory spiked samples were successfully analyzed with this technique. Recoveries averaged > 85% for spiked blank filters at levels from 5 to 50 micrograms per filter with relative standard deviations up to 7%. The instrument's limit of detection (LOD) for ethanol was 0.1 mg l-1. The LOD for derivatization and analysis corresponds to 3 micrograms of SAP per filter (assuming an esterification factor of 0.30 microgram of ethanol per microgram of SAP).

Acrylates↗

PubMed1978

Effect of addition of inorganic acids or alkalis on gelation of polyvinyl alcohol aqueous solution by gamma-ray irradiation.--Color development with iodine--.

Below the critical concentration of polyvinyl alcohol, the effect of inorganic acids or alkalis on gelation of polyvinyl alcohol aqueous solution was investigated by color development with iodine after gamma-ray irradiation. The absorbances of the polyvinyl alcohol-iodine complex decreased remarkably in the presence of nitric or perchloric acid. These acids decompose and form oxygen or hydrogen peroxide which oxidize the polymer and leads to a fading of the color. On addition of sulfuric, phosphoric and hydrochloric acids, the absorbances decrease in the order that agrees with that of the acidity of these acids at the same molarity. In the alkaline solution the absorbances decrease by the addition of sodium hydroxide and aqueous ammonia in the order that agrees with that of the basicity of these alkalis. These results indicate that the gel formation is caused by the radiolysis of water. As a result of chemical analysis, these additives are considered not to be attached to the polymer.

Acids↗

PubMed2004

Simultaneous determination of trans, transmuconic acid and s-phenylmercapturic acid by high pressure liquid chromatography and its application.

The simultaneous determination of urinary trans,trans-muconic acid (t,t-MA) and S-phenylmercapturic acid (S-PMA) was performed by liquid extraction with ethyl acetate and reversed-phase high performance liquid chromatography (RP-HPLC) on a Hypersil-ODS column using the gradient mobile phase of methanol and 0.0012 N perchloric acid and diode array detection at 205 and 264 nm for S-PMA and t,t-MA, respectively. The retention times for t,t-MA and S-PMA were 3.8 and 12.3 minutes, respectively. The recoveries of t,t-MA and S-PMA were > 97%; between-day precisions were all within 8% RSD (100x SD/mean). The method was applied to analyze the urinary t,t-MA and S-PMA of 59 service station attendants exposed to average benzene concentrations in the air of 0.20+/-0.18 ppm. Significant differences in pre-shift and post-shift urinary t,t-MA between smokers and non-smokers were found.

Acetylcysteine↗

PubMed1996

Separation and determination of amino acids, creatinine, bioactive amines and nucleic acid bases by dual-mode gradient ion-pair chromatography.

A simple and fast high-performance liquid chromatography method for the analysis of amino acids and biological bases such as creatinine was developed using a technique termed "dual-mode gradient ion-pair chromatography". A butyl-silica reversed-phase column and water-acetonitrile eluent containing sodium dodecyl sulfate (SDS) and perchloric acid were used for the separation. A concentration gradient of acetonitrile from 15 to 35% provided a good separation of such organic cations. Since change in concentration of acetonitrile causes change in distribution equilibrium of SDS between mobile and stationary phases, a complete regeneration of the column to the initial state is required for the reproducible separations. Completion of the reequilibrium was indicated by a system peak appearing in the UV chromatogram and by conductivity measurements. The formation mechanism of the system peak was revealed. A flow-rate gradient from 1 to 2 ml/min was introduced in addition to the concentration gradient to shorten the cycle time of the chromatography. More than twenty kinds of amino acids, creatine and creatinine were simultaneously separated within 50 min and the cycle time was 80 min including the reequilibration time. A post-column derivatization fluorescence detection system was usable as well as UV detection. This elution system was also useful for the separation of bioactive amines and nucleic acid bases. The developed method was applied to the simultaneous determination of urinary creatinine and diagnostic amino acids due to inherited metabolic disorders.

Acetonitriles↗

PubMed1980

Analysis of isoxazolyl penicillins and their metabolites in body fluids by high-performance liquid chromatography.

A high-performance liquid chromatographic assay method to quantitate the isoxazolyl penicillins, their active metabolites, and their penicilloic acids in serum or urine is described. Separation and analysis is performed using reversed-phase chromatography. Urine samples, after the appropriate dilution, can be assayed directly. Serum samples (0.1 ml) are either extracted with methylene chloride or treated with perchloric acid--methanol. Serum levels as low as 0.4 microgram/ml (extraction procedure) can be assayed accurately.

Chromatography, High Pressure Liquid↗

PubMed1979

Procedure of RNA extraction which does not extract DNA and proteins from nervous tissue cells.

Several schemes of acidic extraction of RNA taken from biochemical or cytochemical literature were compared by means of ultraviolet and visible cytospectrophotometry. Basing on the data obtained an extraction scheme has been recommended which consists in the treatment of nervous tissue sections with 16 per cent perchloric acid at 4 degrees C for 48 h. This extraction has been shown to extract completely cellular RNA without extracting DNA and proteins from the nervous tissue cells. Using this scheme, ultraviolet cytospectrophotometry of neurons and glial cells was performed twice, before and after the selective RNA extraction, which enabled a calculation of RNA concentration by the difference of the absorption values. In mice, after 3 h-swimming, and in cats, after 2-week daily injections of adrenaline, a number of quantitative and qualitative RNA changes were found out in nerve and glial cell of mouse spinal cord and cat sympathetic ganglion with the aid of the recommended scheme of RNA extraction.

Animals↗

PubMed1998

Liquid chromatographic determination of irinotecan and three major metabolites in human plasma, urine and feces.

A new simple reversed-phase high-performance liquid chromatographic method was developed for the determination of irinotecan (CPT-11) and three metabolites in human plasma, urine and feces homogenate. The metabolites of interest were 7-ethyl-10-hydroxycamptothecin (SN-38), its beta-glucuronide derivative (SN-38G) and 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino]carbonyloxycamptothecin (RPR 121056A; also referred to as APC). Sample pretreatment from the various biological matrices involved a rapid protein precipitation with simultaneous solvent extraction of 250-microl aliquots of sample with 500 microl of methanol-5% (w/v) aqueous perchloric acid (1:1, v/v). Separation of the compounds was achieved on an analytical column packed with Hypersil ODS material (100X4.6 mm I.D., 5 microm), and isocratic elution with a mixture of methanol-0.1 M ammonium acetate containing 10 mM tetrabutylammonium sulphate (30:70, v/v), pH 5.3 (hydrochloric acid). The column effluent was monitored at excitation and emission wavelengths of 355 and 515 nm, respectively. Results from a 4-day validation study indicated that this single-run determination allows for simple, simultaneous and rapid quantitation and identification of all analytes with excellent reliability. The described procedure permits the analysis of patient samples, and will be implemented in future studies to investigate the complete metabolic fate and disposition of CPT-11 in cancer patients.

Camptothecin↗

PubMed2005

Validated spectrophotometric and fluorimetric methods for analysis of clozapine in tablets and urine.

Five spectrophotometric methods and one fluorimetric method have been developed and validated for the analysis of clozapine. The spectrophotometric methods were based on the charge-transfer complexation reaction between clozapine as electron donor and each of iodine as sigma-acceptor or 7,7,8,8-tetracyanoquinondimethane (TCNQ), 2,3-dichloro-5,6-dicyano-1,4-benzo-quinone (DDQ), tetracyanoethane (TCNE), and p-chloranilic acid (pCA) as pi-acceptors. The obtained complexes were measured spectrophotometrically at 365, 843, 460, 414, and 520 nm for iodine, TCNQ, DDQ, TCNE, and pCA, respectively. The fluorimetric method was based on the oxidation of clozapine in the presence of perchloric acid by cerium (IV), and subsequent measuring the fluorescence of the produced cerium (III) fluorimetrically at lambda(excitation) 260 and lambda(emission) 355 nm. Under the optimum assay conditions, Beer's law was obeyed at concentrations ranged from 4-200 microg mL(-1) for the spectrophotometric methods and from 24-250 ng mL(-1) for the fluorimetric method. The limits of detection for the spectrophotometric methods were 1.12, 1.76, 2.22, 0.95, and 13.26 microg mL(-1) for iodine, TCNQ, DDQ, TCNE, and pCA, respectively. The limit of detection for the fluorimetric method was 6.69 ng mL(-1). The proposed methods were successfully applied to the analysis of clozapine in tablets with good recoveries. The fluorimetric method could also be applied to the analysis of clozapine in spiked urine samples. The molar ratios and the reaction mechanisms were investigated.

Antipsychotic Agents↗

PubMed1994

Liquid chromatographic determination of the adenosine receptor agonist CGS 21680 in blood using on-line solid-phase extraction on a phenylboronic acid support and fluorescence detection.

An analytical method is described for the selective determination of A1 or A2 adenosine receptor agonists in blood. By implementing solid-phase extraction using immobilized-phenylboronic acid (PBA) in sample pretreatment, all adenosine derivatives are retained via their intact cis-diol group. On-line desorption of the analytes from the PBA support to the C18 analytical column is performed by injection of a small plug of perchloric acid. Fluorescence and UV detection are employed for the different adenosine derivatives. The method is applied to the determination of 2-[p-(2-carboxyethyl)phenylethylamino]-5'-N- ethylcarboxyamidoadenosine (CGS 21680, I) in blood using fluorescence detection. The only off-line sample handling step is the extraction of blood with ethyl acetate and subsequent evaporation of the extraction solvent. The detection limit of the method was 0.25 ng (signal-to-noise ratio 3:1) and the determination limit for I in blood (pretreatment of 100 microliters) was 5 ng/ml. The method was validated and used to study the pharmacokinetics of I in rats.

Acetates↗

PubMed2002

Gabapentin and vigabatrin increase GABA in the human neocortical slice.

The effects of antiepileptic drugs, gabapentin and vigabatrin, on gamma-aminobutyric acid (GABA) concentrations were studied in human (n=14) and rat (n=6) neocortical slice preparations. In this study, neocortical slices were incubated with gabapentin, vigabatrin or no drugs for 3 h in an oxygenated environment. Proton magnetic resonance spectroscopy (MRS) of perchloric acid (PCA) extracts was used to measure GABA concentrations. Vigabatrin increased cellular GABA concentrations in both human and rat neocortical slices by 62% (P<0.001) and 88% (P<0.03), respectively. Gabapentin significantly increased GABA concentrations by 13% (P<0.02) in human neocortical slices made from tissue resected during epilepsy surgery. However, in the rat neocortical slice exposed to the same conditions as the human tissue, gabapentin did not increase GABA significantly. These results confirm our MRS studies in vivo that gabapentin increases GABA levels in epileptic patients, but has minimal or no effect in a healthy rodent model. Caution must be used in extrapolating negative results obtained in rodent models to the human condition.

Acetates↗

PubMed2004

The effects of lactic acid bacteria inoculants and formic acid on the formation of biogenic amines in grass silages.

Silages were prepared in six laboratory experiments from four direct-cut grassland swards and pure swards of perennial ryegrass and false oat with dry matter contents ranging between 180 and 325 g/kg. Grass was fermented at 22 degrees C and silages were stored at the same temperature for 4 months. Untreated silages (negative control) and silages preserved with 3 g/kg of formic acid (positive control) were compared with silages inoculated with commercial strains of Lactobacillus plantarum, Lactobacillus buchneri and a mixed preparation Microsil. The inoculants were applied at a dose of 5.10(6) CFU/g of grass. Seven biogenic amines were extracted from silages with perchloric acid and determined as N-benzamides by micellar electrokinetic capillary chromatography. Common chemical quality parameters of silages were also determined. Tyramine, cadaverine and putrescine were the amines occurring at the highest concentration. As compared to untreated silages, formic acid was most effective to suppress formation of the main amines. Also the inoculants often decreased amine contents significantly (P < 0.05). The inoculants decreased levels of polyamine spermidine more efficiently than formic acid. Contents of histamine, tryptamine and polyamine spermine were very low, commonly below the detection limits.

Animals↗

PubMed1993

N-acetyl-L-aspartate and acetate 1H NMR signal overlapping under mild acidic pH conditions.

The pH dependence of methyl proton chemical shifts of acetate, acetoacetate, N-acetyl-L-aspartate (NAA), and N-acetyl-L-aspartyl-L-glutamate (NAAG) were studied from pH 3 to pH 9. Only slight shifts of acetoacetate, NAA, and NAAG methyl signals were observed, whereas the acetate signal was largely shifted as a result of the titration of its acidic function. At pH 4.7, acetate and NAA methyl signals overlapped, whereas at more acidic pH, the acetate signal appeared downfield when compared to that of NAA. Results are discussed in terms of spectra misinterpretation risks linked to uncontrolled sample pH, on the one hand, and in terms of pH control and contamination by exogenous acetate during perchloric acid cell extract preparation, on the other.

Acetates↗

PubMed2003

High-performance liquid chromatographic method for determination of amodiaquine, chloroquine and their monodesethyl metabolites in biological samples.

A high-performance liquid chromatographic method for determination of amodiaquine (AQ), desethylamodiaquine (DAQ), chloroquine (CQ) and desethylchloroquine (DCQ) in human whole blood, plasma and urine is reported. 4-(4-Dimethylamino-1-methylbutylamino)-7-chloroquinoline was used as internal standard. The drugs and the internal standard were extracted into di-isopropyl ether as bases and then re-extracted into an acidic aqueous phase with 0.1 M phosphate buffer at pH 4.0 for AQ samples and at pH 2.5 for CQ filter paper samples. A C(18) column was used and the mobile phase consisted of methanol-phosphate buffer (0.1 M, pH 3)-perchloric acid (250: 747.5:2.5, v/v). The absorbance of the drugs was monitored at 333 nm and no endogenous compound interfered at this wavelength. The limit of quantification in whole blood, plasma and urine was 100 nM for AQ and DAQ (sample size 100 microliter) as well as for CQ and DCQ in blood samples dried on filter paper. For 1000 microliter AQ and DAQ samples, the limit of quantification was 10 nM in all three biological fluids. The within-assay and between-assay coefficients of variations were always <10% at the limits of quantification. Plasma should be preferred for the determination of AQ and DAQ since use of whole blood may be associated with stability problems.

Amodiaquine↗

PubMed1994

Thiols of intracellular pathogens. Identification of ovothiol A in Leishmania donovani and structural analysis of a novel thiol from Mycobacterium bovis.

Leishmania donovani, the causative agent of visceral leishmaniases, is an intracellular pathogen which proliferates within the host macrophages. Analysis of the thiol composition of L. donovani by means of the thiol-specific reagent, 7-diethylamino-3-(4'-maleimidylphenyl)-4-methylcoumarin, indicated that this organism produces substantial amounts of ovothiol A. This observation was further substantiated by HPLC of extracts of L. donovani after derivatization with bromobimane. L. donovani extracts contained a thiol, the bimane derivative of which had identical retention time and fluorescence quenching to a thiol from Crithidia fasciculata, which had previously been identified as ovothiol A. By comparison, the intracellular bacterial pathogen, Mycobacterium bovis, contained only one major low-molecular-mass thiol, which was assigned the trivial name mycothiol. The structure of the bimane derivative of mycothiol was solved by a combination of one- and two-dimensional 1H and 13C NMR spectroscopy. Spatial relationships in the molecule were further refined by NOE experiments and allowed identification of mycothiol as 1-D-myo-inositol-2-(N-acetyl-L-cysteinyl)amino-2-deoxy-alpha-D-glucopyra noside. This assignment was confirmed by positive-ion fast-atom-bombardment mass spectrometry which gave m/z = 677.6 Da and a sodiated species at 699.6 Da. Analysis of the dansylated hydrolysis products of performic-acid-oxidized mycothiol indicated the presence of 0.85 mol glucosamine and 1.02 mol cysteic acid/mol sulfhydryl groups. Crude extracts of M. bovis contained an enzyme which catalysed the NAD(P)H2-dependent reduction of mycothiol disulfide to the free thiol. Analysis of perchloric acid extracts of Mycobacterium tuberculosis H37RV indicated the presence of a thiol which comigrated with mycothiol, both as the free thiol and as the 7-diethylamino-3-(4'-maleimidylphenyl)-4-methylcoumarin and bimane derivatives, on reverse-phase HPLC. The significance of these findings in terms of the evasion of the host defense mechanisms by leishmania parasites and mycobacteria is considered.

Animals↗

PubMed2000

Ion-pairing high-performance liquid chromatographic method for the detection of N-acetylaspartate and N-acetylglutamate in cerebral tissue extracts.

An ion-pairing high-performance liquid chromatographic method for the determination of N-acetylaspartate and N-acetylglutamate using a C-18 column and a UV detection at 210 nm wavelength, by means of a diode array detector, is presented. A buffer containing 2.8 mM tetrabutylammonium hydroxide, 25 mM KH(2)PO(4), 1.25% methanol, pH 7. 00, is utilized for the isocratic separation of these N-acetylated amino acids, at a flow rate of 1 ml/min and a column temperature of 23 degrees C. The suitability of this chromatographic separation (without additional chromatographic steps prior to HPLC assay) to monitor variations both of N-acetylaspartate and of N-acetylglutamate in perchloric acid brain extracts from rats subjected to the impact acceleration model of diffuse brain injury is also reported. According to the data presented, this HPLC method allows the separation of the two N-acetylated amino acids considered from the many possible interfering compounds, commonly present in extracts of cerebral tissue, which have high extinction coefficients at 210 nm wavelength. Values of N-acetylaspartate and N-acetylglutamate determined by this method showed that cerebral trauma negatively affects both compounds, according to the severity of trauma itself.

Animals↗

PubMed2005

Determination of aliphatic aldehydes by liquid chromatography with pulsed amperometric detection.

An electrochemical detection method for short-chain saturated and unsaturated aliphatic aldehydes separated by liquid chromatography in moderately acidic medium is described. A triple-step waveform of the potentials applied to the polycrystalline platinum electrode, is proposed for sensitive detection of aliphatic aldehydes in flowing streams avoiding tedious pre- or post-column derivatization and/or cleanup procedures. The influences of the perchloric acid concentration and dissolved oxygen in the mobile phase, on the amperometric and chromatographic performance were evaluated and considered in terms of sensitivity and selectivity. Under the optimised experimental conditions (i.e., deoxygenated 50mM HClO4) the proposed analytical method allowed detection limits between 0.2 microM for acrolein and 2.5 microM for valeraldehyde. Regression analysis of calibration data indicates that responses for all investigated compounds are linear over about 2 orders of magnitude above the LOD, with correlation coefficients >0.990. The method was successfully applied to the determination of formaldehyde, acetaldehyde, propionaldehyde and acrolein in real matrices such as spiked water and red wines with good mean recoveries (81-97%).

Aldehydes↗