Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “PERCHLORIC ACID”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,441 records · Page 80Linked to original sources
PubMed2001

Improvement of ethyl glucuronide determination in human urine and serum samples by solid-phase extraction.

An improved method for the determination of ethyl glucuronide (EtG) in human serum and urine was developed using solid-phase extraction (SPE) and gas chromatography (GC) with mass spectrometric detection (MS). EtG was isolated from serum and urine using aminopropyl SPE columns after deproteination with perchloric acid and hydrochloric acid, respectively. The chromatographic separation was performed on a DB 1701 fused-silica column. At a signal-to-noise ratio of 3:1, a quantification limit of 173 and 560 ng/ml and a detection limit of 37 and 168 ng/ml could be determined for serum and urine, respectively. This indicates high specificity and sensitivity of the described method. The mean absolute recovery was approximately 85%, while intra- and inter-day precision of the assay were all less than 7.5%. The linearity of the calibration curves was satisfying as indicated by correlation coefficients of >0.993. The presented method provides the basis for determination and identification of EtG in human serum and urine samples in a low-concentration range for monitoring alcohol consumption during treatment for alcohol dependence and comorbid alcohol abuse of psychotherapy patients.

Calibration↗
PubMed2001

Simultaneous analysis of homocysteine and methionine in plasma.

The new isocratic cation exchange method separates up to eight different amino thiols. The separated sample components are detected electrochemically using a gold electrode and the integrated pulsed amperometry. The eluent composition is, for example, 0.15 M sodium perchlorate, 0.02 M perchloric acid and 5% acetonitrile. The report describes the optimization of chromatographic parameters such as column diameter and eluent composition. Quantitative performance is discussed for eight different amino thiols using standards. Also presented is a long term quantitative study for homocysteine and methionine in plasma samples. The preparation of plasma samples is simpler than with the previously reported version of the method. Only a reduction step is required, and neither column switching nor derivatization are necessary.

Cation Exchange Resins↗
PubMed2001

Simple and rapid high-performance liquid chromatography method for the determination of ofloxacin concentrations in plasma and urine.

A high-performance liquid chromatographic method for the determination of ofloxacin in human plasma and urine was developed. The method involved deproteinisation of the sample with perchloric acid and analysis of the supernatant using a reversed-phase C18 column and fluorescence detection at an excitation wavelength of 290 nm and an emission wavelength of 460 nm. The assay was linear from 0.5 to 10.0 microg/ml. The relative standard deviation of intra- and inter-day assays was lower than 5%. The average recovery of ofloxacin from plasma was 93%. The method was evaluated in samples from healthy subjects whose drug levels were already measured by microbiological assay.

Anti-Infective Agents↗
PubMed2001

Reversed-phase high-performance liquid chromatography procedure for the simultaneous determination of S-adenosyl-L-methionine and S-adenosyl-L-homocysteine in mouse liver and the effect of methionine on their concentrations.

An improved reversed-phase high-performance liquid chromatography (HPLC) procedure with ultraviolet detection is described for the simultaneous determination of S-adenosyl-L-methionine (SAM) and S-adenosyl-L-homocysteine (SAH) in mouse tissue. The method provides rapid resolution of both compounds in a 25-microl perchloric acid extract of the tissue. The limits of detection in 25-microl injection volumes were 22 and 20 pmol for SAM and SAH, respectively. The limits of quantitation in 25-microl injection volumes were 55 and 50 pmol for SAM and SAH, respectively, with recovery consistently >98%. The assay was validated over linear ranges of 55-11000 pmol for SAM and 50-10000 pmol for SAH. The intra-day precision and accuracy were < or =6.4% relative standard deviation (RSD) and 99.9-100.0% for SAH and < or =6.7% RSD and 100.0-100.1% for SAM. The inter-day precision and accuracy were < or =5.9% RSD and 99.9-100.6% for SAH and < or =7.0% RSD and 99.5-100.1% for SAM. Compared to earlier procedures, the HPLC method demonstrated significantly better separation, detection limit and linear range for SAM and SAH determination. The assay demonstrated applicability to monitoring in mice the time-course of the effect of methionine on SAM and SAH levels in the liver. Administering methionine to mice increased by 10-fold the liver concentration of SAM and SAH within 2 h, which then rapidly decreased to the control levels by 8 h. This indicated that methionine was promptly converted to SAM and then rapidly catabolized into SAH. Thus, the metabolism of methionine to SAM should be considered in the supplementation of methionine to maintain SAM levels in the body.

Animals↗
PubMed2002

Determination of topotecan in human whole blood and unwashed erythrocytes by high-performance liquid chromatography.

A reversed-phase HPLC method for the quantitative determination of total topotecan in human whole blood and unwashed erythrocytes has been developed and validated in terms of sensitivity, specificity, precision and accuracy. Linear calibration curves were constructed in the range of 0.20 to 50.0 ng/ml. The sample pre-treatment for whole blood involved a two-step extraction with methanol and perchloric acid. Prior to extraction, erythrocytes were separated from other blood components by centrifugation in MESED instruments. Separations were achieved on an Inertsil ODS-80A analytical column (150x4.6 mm, 5 microm particle size), eluted at 50 degrees C and a flow-rate of 1.00 ml/min, with a mixture of 100 mM ammonium acetate (pH 6.0)-tetrahydrofuran (94.6:5.4, v/v). Fluorescence detection was performed using excitation and emission wavelengths of 381 and 525 nm, respectively. With the applied method, 80% of topotecan was extracted out of whole blood. The lower limit of quantitation in whole blood was established at 0.20 ng/ml with within-run and between-run precisions, respectively, ranging from 1.7 to 9.3% and 1.5-6.1%, while the accuracy ranged from 100 to 113%. The described method will be used in clinical studies to explore the role of erythrocytes in the overall kinetic behavior of topotecan.

Antineoplastic Agents↗
PubMed1996

Stereoselective determination of apomorphine enantiomers in serum with a cellulose-based high-performance liquid chromatographic chiral column using solid-phase extraction and ultraviolet detection.

A novel and rapid method for the separation and determination of R-(-)- and S-(+)-enantiomers of apomorphine in serum by high-performance liquid chromatography with UV detection is reported. The method involved a solid-phase extraction of the R-(-)- and S-(+)-enantiomers of apomorphine and the internal standard R-(-)-propylnorapomorphine from serum using a C8 Bond-Elut column. The HPLC system consisted of a reversed-phase cellulose-based chiral column (Chiralcel OD-R, 250 x 4.6 mm I.D.) with a mobile phase of 35:65 (v/v) acetonitrile-0.05 M sodium perchlorate (pH 2.0, adjusted with 60-62% perchloric acid) at a flow-rate of 0.5 ml/min with UV detection at 273 nm. The detection and quantitation limits were 10 ng/ml for each enantiomer using 1 ml of serum. Linear calibration curves from 10 to 1000 ng/ml for both R-(-)- and S-(+)-enantiomers show coefficient of determination of more than 0.9995. Precision calculated as %R.S.D. and accuracy calculated as % error were 0.2-4.7 and 3.1-6.9%, respectively, for the R-(-)-enantiomer and 1.3-4.2 and 0.3-6.8%, respectively, for the S-(+)-enantiomer.

Animals↗
PubMed1997

High-performance liquid chromatographic determination of 9-(3-pyridylmethyl)-9-deazaguanine (BCX-34) in biological fluids.

9-(3-Pyridylmethyl)-9-deazaguanine (BCX-34), a new purine nucleoside phosphorylase inhibitor, has selective immunosuppressive activity with potential therapeutic value in T-cell-mediated disease. We now report a sensitive, specific and reproducible method for measurement of 9-(3-pyridylmethyl)-9-deazaguanine in biological fluids using high-performance liquid chromatography (HPLC). 9-(3-Pyridylmethyl)-9-deazaguanine was extracted from plasma using perchloric acid precipitation followed by passage through Sep-Pak C18 cartridges (average extraction efficiency, 64.6%). Standard curves were linear over the range of interest (28-1120 ng/ml in plasma and 200-4000 ng/ml in urine, r2 > 0.999). Within-day and between-day coefficients of variation were less than 8%. The limit of quantitation was 28 ng/ml in plasma and 200 ng/ml in urine. This HPLC method should be useful in future clinical studies with this drug.

Administration, Oral↗
PubMed1997

Oral platelet aggregation inhibitor Ro 48-3657: determination of the active metabolite and its prodrug in plasma and urine by high-performance liquid chromatography using automated column switching.

A sensitive and highly automated high-performance liquid chromatography (HPLC) column-switching method has been developed for the simultaneous determination of the active metabolite III and its prodrug II, both derivatives of the oral platelet inhibitor Ro 48-3657 (I), in plasma and urine of man and dog. Plasma samples were deproteinated with perchloric acid (0.5 M), while urine samples could be processed directly after dilution with phosphate buffer. The prepared samples were injected onto a pre-column of a HPLC column switching system. Polar plasma or urine components were removed by flushing the precolumn with phosphate buffer (0.1 M, pH 3.5). Retained compounds (including II and III) were backflushed onto the analytical column, separated by gradient elution and detected by means of UV detection at 240 nm. The limit of quantification for both compounds was 1 ng/ml (500 microl of plasma) and 25 ng/ml (50 microl of urine) for plasma and urine, respectively. The practicability of the new method was demonstrated by the analysis of about 6000 plasma and 1300 urine samples from various toxicokinetic studies in dogs and phase 1 studies in man.

Animals↗
PubMed1997

Rapid and sensitive determination of amprolium in chicken plasma by high-performance liquid chromatography with post-column reaction.

A rapid, sensitive and reproducible reversed-phase HPLC assay was developed for the determination of amprolium (APL) in chicken plasma. Protein in plasma sample was precipitated with 0.33 M perchloric acid and supernatant solution was injected into the HPLC system. Following the chromatographic separation of APL and the beclotiamine (I.S.) on a C18 column, the derivatives of APL and I.S. were formed by post-column reaction and detected by fluorescence detection (excitation at 400 nm, emission at 460 nm). The method showed excellent precision, accuracy and speed with a detection limit of 2 ng/ml. The intra- and inter-assay variance of this method were less than 11.2%. This method has been successfully applied to plasma determinations after oral administration of APL to chicken.

Amprolium↗
PubMed1997

Automated determination of levodopa and carbidopa in plasma by high-performance liquid chromatography-electrochemical detection using an on-line flow injection analysis sample pretreatment unit.

An automated analytical procedure is described for the parallel determination of L-3,4-dihydroxyphenylalanine (levodopa, L-dopa, LD) and the analogous hydrazine compound carbidopa (CD) in dog plasma by ion-pair high-performance liquid chromatography with electrochemical detection (HPLC-ED). After deproteinization of the plasma samples with perchloric acid the catecholamines were extracted from the supernatant by adsorption on a small column filled with alumina. The extraction and redissolution were automatically performed in a flow injection analysis unit (FIA) coupled to the HPLC system. The performance of the whole system was tested on dog plasma samples including specimens taken after oral administration of the anti-Parkinsonism drug Duellin, which is a combination tablet of levodopa and carbidopa.

Animals↗
PubMed1997

Simultaneous determination of 5-fluorouracil and its active metabolites in serum and tissue by high-performance liquid chromatography.

In order to observe the biodistribution of 5-fluorouracil (5-FU) and its main metabolites in different kinds of tissue (tumor, liver, kidney, spleen, mucosa, lungs, heart, peritoneum, pancreas) and serum according to various novel application forms, a simple and rapid method for the simultaneous determination of 5-FU and its active metabolites 5-fluorouridine (5-FUrd) and 5-fluoro-2'-deoxyuridine (5-FdUrd) has been established. Proteins in serum and tissue samples were precipitated by perchloric acid after addition of the internal standard 5-bromouracil. The compounds were separated using an ODS Hypersil (5 microm) column and detected by UV absorbance (254 nm). Specificity, linearity, reproducibility, intermediate precision and accuracy of the method were established. The lower limit of quantitation (LOQ) for the compounds in serum and various tissue samples was determined. Data on the recovery of the compounds and the internal standard are provided.

Animals↗
PubMed1998

Simultaneous detection of reduced and oxidized glutathione in tissues and mitochondria by capillary electrophoresis.

We have developed a rapid and precise method for glutathione quantitation by capillary electrophoresis, that allows a low amount of both redox forms to be measured. Small fragments of rat heart or liver tissues (20 mg wet weight) and the corresponding mitochondria (1 mg protein) were homogenized in 1% perchloric acid and the acid-soluble phase ultrafiltered by centrifugation with a microconcentrator (Mr cut-off 3000 Da). The analysis was performed at a constant temperature (28 degrees C) using a Beckman P/ACE System 2100, equipped with a UV absorbance detector set to 200 nm. The limit of quantitation in heart tissue was 1.8 microM for GSH and 1.2 microM for GSSG. Myocardial concentrations of GSH and GSSG were 8.1 +/- 2.6 and 0.45 +/- 0.15 (nmol/mg protein +/- S.D.), respectively. The ratio of GSH to GSSG was 17.8 +/- 1.3 for heart tissue, whereas it was much higher (>100) in the mitochondria. An oxidative stress decreased the myocardial tissue GSH/GSSG ratio, indicating that the CE analysis of both glutathione forms is also a useful method to study biological redox modification.

Animals↗
PubMed1998

Colorimetric determination of hydroxyurea in human serum using high-performance liquid chromatography.

A high-performance liquid chromatography assay for hydroxyurea in human serum was developed based on a commercial colorimetric assay kit for urea (Sigma Diagnostics). Serum (0.5 ml), spiked with methylurea as an internal standard, was treated with 70% perchloric acid. Supernatant (0.2 ml) was combined with 0.7 ml of BUN acid reagent and 0.6 ml of BUN color reagent. The resulting colored reactant (100 microl) was analyzed on a 300 x 3.9 mm Bondclone 10 C18 column coupled with a UV-Vis detector, at 449 nm. The mobile phase was 13% acetonitrile in water. Retention times of colored derivatives of hydroxyurea and methylurea were 6.5 and 12.2 min, respectively. The log-log calibration curve was linear from 0.0065 to 1.31 mM. Average accuracy was 99.9+/-4.0% and the intra- and inter-day error of assay did not exceed 11%.

Chromatography, High Pressure Liquid↗
PubMed1997

High-performance liquid chromatographic determination of N-alpha-acetyl-L-carnosine in equine plasma.

N-alpha-Acetyl-L-carnosine (NAcCAR) in perchloric acid extracts of equine plasma was assayed by high-performance liquid chromatography on a 3 microns Hypersil ODS (150 x 4.6 mm I.D.) column eluted with 5 mM phosphoric acid-1 mM triethylamine, pH 2.58. NAcCAR was isolated by solid-phase extraction on Isolute PRS (propylsulphonyl) columns. The HPLC mean retention time for NAcCAR was 5.9 +/- 0.2 min. The recovery from plasma by solid-phase extraction was 93.9-99.7% and lower limit of detection in plasma was 0.18 microM. The normal NAcCAR concentration in equine plasma was 2.4 +/- 0.3 microM. The method was applied to the determination of plasma concentrations following oral and intravenous NAcCAR administration.

Animals↗
PubMed1998

Simple high-performance liquid chromatographic method for the determination of metformin in human plasma.

A simple high-performance liquid chromatographic method using ultraviolet detection was developed for the determination of metformin in human plasma. The method entailed direct injection of the plasma sample after deproteination using perchloric acid. The mobile phase comprised 0.01 M potassium dihydrogen orthophosphate (pH 3.5) and acetonitrile (60:40, v/v). Analyses were run at a flow-rate of 1.0 ml/min with the detector operating at a detection wavelength of 234 nm. The method is specific and sensitive, with a quantification limit of approximately 60 ng/ml and a detection limit of 15 ng/ml at a signal-to-noise ratio of 3:1. The mean absolute recovery value was about 97%, while the within-day and between-day coefficient of variation and percent error values of the assay method were all less than 8%. The calibration curve was linear over a concentration range of 62.5-4000 ng/ml.

Adult↗
PubMed1999

Simultaneous determination of fentanyl and midazolam using high-performance liquid chromatography with ultraviolet detection.

When measuring fentanyl and midazolam simultaneously in the same plasma sample with standard high-performance liquid chromatography-ultraviolet (HPLC-UV) detection, overlap of the fentanyl peak by the midazolam peak occurs, which makes fentanyl determination impossible. We tested the hypothesis that by acidifying the methanol mobile phase with 0.02% perchloric acid, 70%, it would be possible to separate both peaks. The UV detector was set at 200 nm. Calibration curves for fentanyl (range 0-2000 pg/ml) and midazolam (range 0-400 ng/ml) were linear (r>0.99). The detection limits were 200 pg/ml (fentanyl) and 10 ng/ml (midazolam). Precision and accuracy for intra- and inter-assay variability as well as in-line validation with quality control samples (QCS) were acceptable (<15 and 20%, respectively), except for fentanyl QCS of 200 pg/ml (17.8% precision). Although less sensitive than gas chromatography-mass spectrometry (GC-MS), reliable measurements of fentanyl, simultaneously with midazolam, can be performed with this HPLC-UV system.

Adjuvants, Anesthesia↗
PubMed1999

Development and validation of a bioanalytical assay for (E)-5-(2-bromovinyl)-2'deoxyuridine in plasma by capillary zone electrophoresis.

A capillary zone electrophoretic method for the quantification of (E)-5-(2-bromovinyl)-2'-deoxyuridine in plasma has been developed and validated. Separation was performed with a 25 mmol/l borate buffer, pH 9.0, after an initial rinsing step with sodium hydroxide. The rinsing step was necessary for reproducible analyses of aqueous samples and plasma extracts obtained by C18 solid-phase extraction after deproteination with perchloric acid. No interferences with plasma compounds were observed. The calibration graph was linear over the range of 30 to 3000 ng/ml using 5-fluorouracil as external standard. The limit of quantification was 24 ng/ml. The CZE method is fast, reproducible, linear and is therefore a good alternative for the already established HPLC methods.

Antiviral Agents↗
PubMed1999

Automated high-performance liquid chromatographic method with precolumn reduction for the determination of ubiquinol and ubiquinone in human plasma.

We developed a gradient HPLC method with automated precolumn reduction for direct electrochemical detection of ubiquinol-10 (CoQ10H2) and total coenzyme Q10 (TQ10) in human plasma. The concentration of ubiquinone-10 (CoQ10) was calculated by subtraction of CoQ10H2 from TQ10. Preparation of reducing agent and precolumn reduction was performed by a programmable auto-injector. The two mobile phases used were: A, 100% of methanol containing 50 mM sodium perchlorate and 10 mM perchloric acid; and B, a mixture of ethanol and tert.-butanol (80:20, v/v). Sample preparation was simply a deproteinisation process with 10-fold ethanol. A good linear relationship was obtained for CoQ10H2 concentration from 0.1 to 3 micromol/l. The detection limit was 2.5 nmol/l with an injection volume of 20 microl. The analytical recovery and reproduciblity were generally >90%. To validate the method, 18 freshly collected plasma samples of normal healthy subjects were analysed. The mean ratio of CoQ10H2/CoQ10 was 93:7. The proposed method is sensitive, reliable and can be used for clinical investigation.

Automation↗