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PubMed1994

Analysis of enloplatin by liquid chromatography and of platinum by atomic absorption spectrometry in various biological fluids.

Analytical methods were developed and validated for the determination of enloplatin (an anticancer agent) in plasma by reversed-phase LC and for platinum (an elemental component of enloplatin) in plasma, plasma ultrafiltrate (PUF) and whole blood by flameless atomic absorption spectrometry (FAAS). The LC procedure involved protein precipitation with dilute perchloric acid. The supernatant was mixed with sodium phosphate buffer and injected into the LC system. A C18 or a cyano column was used, depending on sample matrix, with UV detection at 230 nm. The LC method was linear from 0.50 to 50.0 micrograms ml-1. Inter-day and intra-day precision (RSD%) and accuracy (relative error%) were < +/- 14%. The FAAS procedure utilized a graphite furnace, a hollow cathode platinum (Pt) lamp, and Zeeman background correction. An aliquot of plasma, PUF, or whole blood was mixed with a solution of Triton X-100 and Antifoam-B and injected into the FAAS system. The FAAS method showed goodness of fit from 0.05 to 10.0 micrograms Pt/ml. Inter-day and intra-day precision and accuracy were < +/- 15%. The methods were developed to support pharmacokinetic studies in humans, dogs and rats.

Animals↗
PubMed1995

Determination of ibuprofen in erythrocytes and plasma by high performance liquid chromatography.

A high-performance liquid chromatographic (HPLC) method is described for the determination of ibuprofen in isolated erythrocytes and plasma. Before HPLC analysis ibuprofen was isolated by liquid-liquid extraction from these biological matrices; methylene chloride proved to be the best of the organic solvents tested. For the sample of erythrocytes it was necessary to carry out haemolysis prior to their extraction. HPLC was performed on a C-18 column with a mobile phase of methanol-water (220:100, v/v) acidified with perchloric acid to pH 3. Ultraviolet detection was at 222 nm. This method has been applied to the quantification of ibuprofen in rabbit erythrocytes and plasma for a pharmacokinetics study.

Animals↗
PubMed1996

The impact of column temperature in the high performance liquid chromatographic analysis of topotecan in rat and dog plasma.

A sensitive high performance liquid chromatographic (HPLC) assay has been developed and validated for the quantitation of the novel anticancer agent topotecan and topotecan as its lactone plus carboxylate forms in rat and dog plasma. Linear responses in analyte standard peak areas were observed over the concentration ranges 0.10-10 ng ml-1 using 100 microliters of rat plasma and 0.2-100 ng ml-1 using 100 microliters of dog plasma. Due to the instability of the drug in the biological matrix it was necessary to obtain the plasma fraction within 5 min after blood sampling by centrifugation, immediately followed by protein precipitation with cold methanol (-30 degrees C). For the determination of total drug levels (lactone plus lactone ring-opened form), plasma samples were deproteinated with methanol and subsequently acidified with 2% (v/v) perchloric acid. The samples were analysed by HPLC using a Zorbax SB-C18 Stable Bond column and methanol-0.1 M hexane-1-sulfonic acid in methanol-0.01 M N,N,N'N'-tetramethylethylenediamine in distilled water pH 6.0 (25:10:65, v/v/v) as the mobile phase. The detection was performed fluorimetrically. The analytical column was thermostated at 19-21 degrees C to obtain baseline resolution between an interfering endogenous compound in rat and dog plasma and topotecan. This endogenous peak was absent in human plasma. Variation of chromatography temperature appeared to be a very useful tool in the bioanalysis of topotecan. It allowed optimization of the separation between the endogenous compound and the analyte; different mechanisms of solute interactions are apparently involved in this reversed-phase ion-pair chromatographic system.

Animals↗
PubMed1986

Purification of antigens of mammary tumor of the mouse by gel filtration.

This study was designed to isolate the biologically active components from a perchloric acid (PCA) extract of mammary tumor virus (MTV)-induced mouse mammary tumors (AMMT) previously shown to be capable of inducing DNA synthesis in spleen cells of mice presensitized by inoculation of viable syngeneic mammary tumor cells. AMMT (450 mg) was eluted fom an Ultrogel AcA54 column with separation range of 5-70K in a buffer containing Tris-sodium chloride and EDTA. Two fractions were separated with estimated molecular weights of 68-70K (AMMT I) and 35-40K (AMMT II). AMMT I and AMMT II exhibited DNA synthetic activity 78-fold and 35-fold, respectively, greater than AMMT. The feasibility of further purification of AMMT I by isoelectric focusing was also demonstrated. These components provide the opportunity for further investigation into the molecular basis of tumor-host relationship in this animal model.

Animals↗
PubMed1992

MDA, oxypurines, and nucleosides relate to reperfusion in short-term incomplete cerebral ischemia in the rat.

Short-term incomplete cerebral ischemia (5 min) was induced in the rat by the bilateral clamping of the common carotid arteries. Reperfusion was obtained by removing carotid clamping and was carried out for the following 10 min. Animals were sacrificed either at the end of ischemia or reperfusion. Controls were represented by a group of sham-operated rats. Peripheral venous blood samples were withdrawn from the femoral vein from rats subjected to cerebral reperfusion 5 min before ischemia, at the end of ischemia, and 10 min after reperfusion. Neutralized perchloric acid extracts of brain tissue were analyzed by a highly sensitive high-performance liquid chromatography (HPLC) method for the direct determination of malondialdehyde, oxypurines, nucleosides, nicotinic coenzymes, and high-energy phosphates. In addition, plasma concentrations of malondialdehyde, hypoxanthine, xanthine, inosine, uric acid, and adenosine were determined by the same HPLC technique. Incomplete cerebral ischemia induced the appearance of a significant amount (8.05 nmol/g w.w.; SD = 2.82) of cerebral malondialdehyde (which was undetectable in control animals) and a decrease of ascorbic acid. A further 6.6-fold increase of malondialdehyde (53.30 nmol/g w.w.; SD = 17.77) and a 18.5% decrease of ascorbic acid occurred after 10 min of reperfusion. Plasma malondialdehyde, which was present in minimal amount before ischemia (0.050 mumol/L; SD = 0.015), significantly increased after 5 min of ischemia (0.277 mumol/L; SD = 0.056) and was strikingly augmented after 10 min of reperfusion (0.682 mumol/L; SD = 0.094). A similar trend was observed for xanthine, uric acid, inosine, and adenosine, while hypoxanthine reached its maximal concentration after 5 min of incomplete ischemia, being significantly decreased after reperfusion. From the data obtained, it can be concluded that tissue concentrations of malondialdehyde and ascorbic acid, and plasma levels of malondialdehyde, oxypurines, and nucleosides, reflect both the oxygen radical-mediated tissue injury and the depression of energy metabolism, thus representing early biochemical markers of short-term incomplete brain ischemia and reperfusion in the rat. In particular, these results suggest the possibility of using the variation of malondialdehyde, oxypurines, and nucleosides in peripheral blood as a potential biochemical indicator of reperfusion damage occurring to postischemic tissues.

Adenine Nucleotides↗
PubMed1989

Age-specific methylation of high-mobility-group proteins of the rat liver and its modulation by spermine and sodium butyrate.

Liver slices from young (20 weeks) and old (117 weeks) rats were incubated with [methyl-14C]methionine in the absence or presence of spermine or sodium butyrate. The high-mobility-group (HMG) non-histone proteins were extracted from the liver with perchloric acid and separated by acid-urea polyacrylamide slab gel electrophoresis. Methylation of HMG proteins decreased drastically in old rats. Whereas spermine inhibited the methylation of total HMG proteins in young rats, it had no effect in old age. On the contrary, sodium butyrate did not change the incorporation of methyl groups into total HMG proteins of young rats, but inhibited that of old rats. Particularly, the incorporation of [14C]methyl groups into HMG 2 was enhanced but into other HMGs it was reduced by both effectors in young and old age. Such discrepancies in the methylation of HMG proteins and their differential modulation by spermine and butyrate might affect the higher-order organization of chromatin and consequently destabilize the expression of genes during aging.

Aging↗
PubMed1994

Synthesis of 2-[18F]fluoro-2-deoxy-L-glucose and positron emission tomography studies in monkeys.

2-[18F]Fluoro-2-deoxy-L-glucose was synthesized from its trifluoromethanesulfonyl precursor. The precursor was prepared by selective acetylation and triflation of L-mannose. L-Mannose was first treated with acetic anhydride in the presence of a catalytic amount of perchloric acid and then reacted with phosphorus tribromide followed by aqueous sodium acetate to produce pure 1,3,4,6-tetra-O-acetyl-a-L-mannopyranose in 32% yield. This compound was treated with trifluoromethanesulfonic anhydride and pyridine in methylene chloride to form 1,3,4,6-tetra-O-acetyl-O-tritrifluoromethanesulfonyl-a-L-mannopyra nose in 77% yield. Nucleophilic substitution of the triflate with 18F-in the presence of Kryptofix 2,2,2 followed by acid hydrolysis produced 2-[18F]fluoro-2-deoxy-L-glucose with a radiochemical yield of 20-30% (EOS) within 90 min. Biodistribution studies in rats and PET imaging in Rhesus monkeys demonstrated that this sugar analog distributes in the extracellular space of most organs but is excluded from the CNS.

Animals↗
PubMed1990

Isolation and quantitation of ubiquitin from rat brain.

A fast and sensitive method for the isolation and quantitation of cytoplasmic ubiquitin from brain by reversed-phase high-performance liquid chromatography is described. Cytosol from brain tissue was obtained by differential centrifugation and, after perchloric acid treatment, the sample was concentrated and ubiquitin was quantitatively isolated by means of a single chromatographic run. The amino acid composition, molecular weight, and primary structure of the pure protein were identified. The addition of monoiodinated 125I-ubiquitin to the sample as an internal standard indicated high native ubiquitin recovery. Statistical analysis carried out on different preparations and standardization of the chromatographic system indicated both the accuracy and the reproducibility of the method.

Amino Acid Sequence↗
PubMed2005

Intracellular nucleotide and nucleotide sugar contents of cultured CHO cells determined by a fast, sensitive, and high-resolution ion-pair RP-HPLC.

Analysis of intracellular nucleotide and nucleotide sugar contents is essential in studying protein glycosylation of mammalian cells. Nucleotides and nucleotide sugars are the donor substrates of glycosyltransferases, and nucleotides are involved in cellular energy metabolism and its regulation. A sensitive and reproducible ion-pair reverse-phase high-performance liquid chromatography (RP-HPLC) method has been developed, allowing the direct and simultaneous detection and quantification of some essential nucleotides and nucleotide sugars. After a perchloric acid extraction, 13 molecules (8 nucleotides and 5 nucleotide sugars) were separated, including activated sugars such as UDP-glucose, UDP-galactose, GDP-mannose, UDP-N-acetylglucosamine, and UDP-N-acetylgalactosamine. To validate the analytical parameters, the reproducibility, linearity of calibration curves, detection limits, and recovery were evaluated for standard mixtures and cell extracts. The developed method is capable of resolving picomolar quantities of nucleotides and nucleotide sugars in a single chromatographic run. The HPLC method was then applied to quantify intracellular levels of nucleotides and nucleotide sugars of Chinese hamster ovary (CHO) cells cultivated in a bioreactor batch process. Evolutions of the titers of nucleotides and nucleotide sugars during the batch process are discussed.

Animals↗
PubMed2004

Determination of thiodiglycol, a mustard gas hydrolysis product by gas chromatography-mass spectrometry after tert-butyldimethylsilylation.

A method for determining thiodiglycol (TDG), a mustard gas hydrolysis product in water, serum and urine samples using gas chromatography-mass spectrometry (GC-MS) after tert-butyldimethylsilylation (TBDMS) is described. Quantitation of TDG was performed by measuring the respective peak area on the extracted ion chromatogram of m/z 293, using an internal standard, the TDG homologue, thiodipropanol, peak area of which was measured as m/z 321. The presence of salts in the sample solution not only suppressed the loss of TDG by vaporization during the evaporation of water, but also facilitated the rate of production of di-silylated derivative, bis(tert-butyldimethylsilyoxylethyl)sulfide (TDG-(TBDMS)2). Under the pretreatment conditions used, in which 0.5 ml of water sample supplemented with 100 microM potassium chloride was evaporated to dryness under reduced pressure, followed by reaction with N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide at 60 degrees C for 1 h, TDG-(TBDMS)2 was reproducibly detected with about a 55% recovery and a limit of detection (LOD, scan mode, S/N = 3) of 5.4 ng/ml. TDG was also determined by GC-MS from a 0.5 ml serum sample (after perchloric acid deproteinization) and from a 0.1 ml urine sample, after TBDMS derivatization. The LOD was determined to be 7.0 and 110 ng/ml for serum and urine, respectively.

Gas Chromatography-Mass Spectrometry↗
PubMed2005

Optimizing the integrated pulsed amperometric multicycle step waveform for the determination of tetracyclines.

A method of modified integrated pulsed amperometric detection with multicycle step waveform (Multi-IPAD) following high-performance liquid chromatography (HPLC) was applied for the determination of tetracyclines (TCs) including dimethyltetracycline (DMTC), oxytetracycline (OTC) and tetracycline (TC). The key advantages of the Multi-IPAD are the abilities to enhance sensitivity and reproducibility and the ability to keep working electrode clean through the use of a high-frequent waveform alteration in integration step and the use of a cleaning potential, which is quite different from conventional three-step potential waveform. The analyses were carried out using the mobile phase of acetonitrile-water mixture solution (10:90, v/v) containing 1% perchloric acid on a C(18) column at a flow rate of 0.21 mL/min. The IPAD waveform parameters were optimized to maximize the signal-to-noise ratio (S/N) and successfully applied for the sensitive detection of TCs. The detection limits (S/N=3, 20 microL injected) were 0.07 mg/L for DMTC, 0.08 mg/L for OTC and 0.05 mg/L for TC. The peak height relative standard deviations (RSDs) of every compound for replicate injection (n=15) determined were below 4.6%.

Chromatography, High Pressure Liquid↗
PubMed2006

Improved method for the determination of biogenic amines and polyamines in vegetable products by ion-pair high-performance liquid chromatography.

Here, we report on the optimisation and validation of a liquid chromatographic method for the determination of 12 biologically active amines from vegetal food products in a single 40-min run. The suitability of the method was checked in five vegetal products of distinct matrix: spinach (leaves), hazelnut (high protein and fat content), banana, potato (high starch content), and milk chocolate (processed). Sample preparation consisted of a 0.6 M perchloric acid extraction from a minced homogeneous aliquot. For samples with high starch content, a previous mild hydrolytic treatment was required to prevent gel formation. The range of linearity was from 0.1 to 10 mg/l, except for serotonin and spermine (from 0.5 to 10 mg/l), and the correlation coefficient was higher than 0.997 (P < 0.001) for all standard curves. The detection limits and the determination limit were below 0.07 and 0.2 mg/l, respectively, except for spermine, which was 0.14 and 0.4 mg/l. The precision of the method was satisfactory; the relative standard deviation obtained for each amine in each product was acceptable according to Horwitz. Recovery was between 77 and 110% for all amines, irrespective of the product.

Biogenic Amines↗
PubMed2004

Spectrophotometric method for the determination of verapamil hydrochloride in pharmaceutical formulations using N-bromosuccinimide as oxidant.

A rapid, simple and sensitive validated visible spectrophotometric method has been described for the assay of verapamil hydrochloride either in pure form or in pharmaceutical formulations. The method involves the oxidation of the verapamil hydrochloride with N-bromosuccinimide in perchloric acid medium at room temperature, leading to the formation of a yellow colored product, which absorbs maximally at 415 nm. Under the optimized experimental conditions, the color is stable up to 45 min and Beer's law is obeyed in the concentration range of 10.0-200.0 microg ml(-1) with molar absorptivity and Sandell's sensitivity of 2.55 x 10(3) l mol(-1) cm(-1) and 0.192 microg cm(-2) per 0.001 absorbance unit, respectively. The method has been successfully applied to the determination of the drug in commercial dosage forms. Statistical comparison of the results with those of a reference method by means of point and interval hypothesis shows excellent agreement and indicates no significant difference in accuracy and precision. Results of analyses were optimized and validated statistically and through recovery studies. The experimental true bias of all samples is smaller than +/-2%.

Bromosuccinimide↗
PubMedDate not supplied

Simple fluorimetric method for determination of certain antiviral drugs via their oxidation with cerium (IV).

A simple and sensitive fluorimetric method for determination of antiviral drugs: ribavirin, acyclovir, and amantadine hydrochloride has been developed. The method was based on the oxidation of these drugs by cerium(IV) in presence of perchloric acid and subsequent monitoring the fluorescence of the induced cerium(III) at lambdaexcitation 255 and lambdaemission 355 nm. Different variables affecting the reaction conditions such as the concentrations of cerium(IV), type and concentration of acid medium, reaction time, temperature, and the diluting solvents were carefully studied and optimized. Under the optimum conditions, linear relationships with good correlation coefficients (0.9978-0.9996) were found between the relative fluorescence intensity and the concentrations of the investigated drugs in the range of 50-1400 ng ml-1. The assay limits of detection and quantitation were 20-49, and 62-160 ng ml-1, respectively. The precision of the method was satisfactory; the values of relative standard deviations did not exceed 1.58%. No interference could be observed from the excipients commonly present in dosage forms. The proposed method was successfully applied to the analysis of the investigated drugs in pure and pharmaceutical dosage forms with good accuracy and precision; the recovery percentages ranged from 99.2 to 101.2+/-0.48-1.30%. The results obtained by the proposed fluorimetric method were comparable with those obtained by the official method stated in the United States Pharmacopoeia.

Acyclovir↗
PubMed2006

New validated method for piracetam HPLC determination in human plasma.

The new method for HPLC determination of piracetam in human plasma was developed and validated by a new approach. The simple determination by UV detection was performed on supernatant, obtained from plasma, after proteins precipitation with perchloric acid. The chromatographic separation of piracetam under a gradient elution was achieved at room temperature with a RP-18 LiChroSpher 100 column and aqueous mobile phase containing acetonitrile and methanol. The quantitative determination of piracetam was performed at 200 nm with a lower limit of quantification LLQ=2 microg/ml. For this limit, the calculated values of the coefficient of variation and difference between mean and the nominal concentration are CV%=9.7 and bias%=0.9 for the intra-day assay, and CV%=19.1 and bias%=-7.45 for the between-days assay. For precision, the range was CV%=1.8/11.6 in the intra-day and between-days assay, and for accuracy, the range was bias%=2.3/14.9 in the intra-day and between-days assay. In addition, the stability of piracetam in different conditions was verified. Piracetam proved to be stable in plasma during 4 weeks at -20 degrees C and for 36 h at 20 degrees C in the supernatant after protein precipitation. The new proposed method was used for a bioequivalence study of two medicines containing 800 mg piracetam.

Acetonitriles↗
PubMed2003

High-performance liquid chromatographic assay of metabolites of thioguanine and mercaptopurine in capillary blood.

The main metabolites of the cytotoxic drugs thioguanine (6TG) and mercaptopurine (6MP) can be measured conveniently in red blood cells (RBC). Isolation of RBC, however, is laborious and requires some milliliters of blood. This HPLC assay allows measurements of thiopurine metabolites in very small blood samples obtained from the finger-tip. The metabolites, derivatives of 6TG and methylmercaptopurine (6MeMP), were extracted and hydrolized with perchloric acid to liberate the corresponding base. 6MeMP is completely transformed under these conditions to 4-amino-5-(methylthio)carbonyl imidazole. The chromatographic separation of 6TG and this imidazole was performed in a single run under isocratic conditions within 10 min using a 70 mm column. The quantification limit was 0.5 nmol/ml for 6TG and 3 nmol/ml blood for 6MeMP. The accuracy was 83% for 6TG (CV=3%) over the concentration range of 0.5-20 nmol/ml blood and 102% (CV=4%) for 6MeMP over the range of 3-150 nmol/ml blood. The intra-assay CV ranged from 5.4 to 7.4% for 6TG and from 6.2 to 10.6% for 6MeMP. The inter-assay CV was 7.5 and 9.5% in a pooled blood sample. The levels in RBC in whole blood were nearly coincident with those obtained in separated RBC, isolation of RBC therefore is not necessary for these measurements, if the drugs are given per os in the day before blood sampling. The concentration of 6MeMP nucleotides is more dependent on the given 6MP dose than the concentration of 6TG nucleotides. Intraindividual variations were small at unchanged drug doses, interindividual metabolite concentrations were highly variable.

Adolescent↗
PubMed2003

Microdialysis for the determination of acetaldehyde and ethanol concentrations in the striatum of freely moving rats.

The subject of the present paper is the simultaneous determination of ethanol (EtOH) and acetaldehyde (AcH) concentrations in the striatum of freely moving rats using an in vivo microdialysis followed by head-space gas chromatography (GC). Major operation conditions of GC were as follows: column, injector and detector temperatures 90, 110 and 200 degrees C, respectively; Supelcowax wide bore capillary column (60 m length, 0.53 mm i.d., 2 microm film thickness); carrier gas, nitrogen; flow rate, 20 ml/min. The recovery of EtOH and AcH at a concentration 40 mM and 250 microM, respectively, by microdialysis showed a maximum of 83.8+/-12.2 and 51.2+/-6.5%, respectively, at a flow rate of 0.8 microl/min. A good linear calibration curve in the concentration range of 5-50 mM for EtOH (r=0.998), and 10-250 microM for AcH (r=0.988) was observed. Microdialysates were collected for 10 min each after insertion of probe into the striatum. Rats were treated with cyanamide (100mg/kg, a potent aldehyde dehydrogenase inhibitor) and 60 min later with EtOH (1g/kg) intraperitoneally. A 10 min sample was about 8 microl. This volume was mixed with 40 microl of 0.002% t-butanol as an internal standard in 0.6N perchloric acid, and then analyzed by head-space GC method. The peak EtOH and AcH concentrations in the striatal dialysates reached maximum at 30 min, and then gradually decreased. This method represents a reasonable tool to quantify in vivo both AcH and EtOH levels simultaneously in rat brain.

Acetaldehyde↗
PubMed2004

Albendazole sulphoxide concentrations in plasma of endemic normals from a lymphatic filariasis endemic region using liquid chromatography.

A simple and sensitive reversed-phase isocratic HPLC method for the determination of albendazole and its metabolites has been developed. The mobile phase consisting of acetonitrile-water-perchloric acid (70%) (30:110:0.06 (v/v/v)) was pumped at a flow rate of 0.80 ml/min on a 5 microm, reverse phase, Discovery RPamide C16 column with UV detection at 290 nm. The calibration graphs were linear in the range of 0.05- 1 microg/ml for albendazole, albendazole sulphoxide and albendazole sulphone. The limit of quantification was 50 ng/ml for albendazole, 25 ng/ml for albendazole sulphoxide and 30 ng/ml for albendazole sulphone. The within-day and day-to-day coefficient of variation averaged 4.98 and 6.95% for albendazole, 3.83 and 6.83% for albendazole sulphoxide and 3.44 and 5.51% for albendazole sulphone, respectively. The mean extraction recoveries of albendazole, albendazole sulphoxide and albendazole sulphone were 79.25, 93.03 and 88.78%, respectively. The method was applied to determine the plasma levels of albendazole sulphoxide in endemic normals administered with albendazole during pharmacokinetic studies.

Adult↗