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PubMed2006

Determining sulfamonomethoxine and its acetyl/hydroxyl metabolites in chicken plasma under organic solvent-free conditions.

A quantitative technique is described for a sample preparation followed by high performance liquid chromatography method for the simultaneous determination of sulfamonomethoxine and its metabolites, N4-acetyl SMM and 2,6-dihydroxy SMM, in chicken plasma. The average recoveries, analytical total time, and limits of quantitation were >/=80% (relative standard deviations (SD) </=6%), <30 min sample-1 (12 samples in 2 h), and </=0.09 microg ml(-1), respectively. The procedure, performed under 100% aqueous conditions, uses no organic solvents and toxic reagents at all and is, therefore, harmless to the environment and humans.

Animals↗
PubMed1989

Inter-laboratory transfer of HPLC methods: problems and solutions.

As high-performance liquid chromatography (HPLC), the premier analytical technique in the pharmaceutical industry, becomes more ubiquitous, methods are more frequently being transferred from one laboratory to another. This review will discuss sources of failures to reproduce HPLC procedures, ranging from sample handling and preparation, through mobile phase, injector, column, detector and data manipulation problems. Also to be considered will be the precautions that should be taken, when initially developing a method, to obviate future problems. These precautions include using stable, well-defined analytical columns, buffered mobile phases, low wavelengths (or a mass-sensitive detector) and internal tests for accuracy; based on the author's experiences. Since the laboratory that originally developed the procedure has the moral obligation and, perhaps, the regulatory responsibility to "guarantee" that the method will perform successfully elsewhere, a series of increasingly comprehensive steps will be given, based on practice, to be followed by the laboratory that could not reproduce the procedure. Also to be discussed are approaches for treating methods that were initially successful but have slowly deteriorated and now fail, and several examples of procedures that were not reproducible in some other laboratories.

Chromatography, High Pressure Liquid↗
PubMed2001

[Sorbents for solid phase extraction and their use].

Extraction on the solid phase is a rapid, simple, effective, and flexible method of preparation of samples for the analysis proper and it can be used in many areas of analysis (pharmacy, biochemistry, food industry, environmental examination, etc.). Possible use in on-line and automatic systems is also advantageous. A very wide scale of proposed sorbents and the use of their combinations thus make extraction on the solid phase an effective method for the isolation and preconcentration of the analyte from the complex matrix of the sample.

Absorption↗
PubMed1997

Quantitative determination of BMS-186716, a thiol compound, in rat plasma by high-performance liquid chromatography-positive ion electrospray mass spectrometry after hydrolysis of the methyl acrylate adduct by the native esterases.

During method development in support of non-clinical studies in animal models, BMS-186716 was found to be extremely unstable in blood and plasma. Stabilization of the compound was achieved by reacting the compound with methyl acrylate (MA) in blood, from which the plasma was then prepared. While the resulting BMS-186716-MA adduct was found to be stable in dog plasma, and hence it was used as the basis for the method developed for analysis of dog plasma samples, the BMS-186716-MA adduct was found to be unstable in rat plasma as it was readily hydrolyzed to BMS-186716-acrylic acid (AA) by native esterases found in rat plasma. Although the finding of the instability of BMS-186716-MA in rat plasma was not the result of prospective planning, we were able to successfully develop a quantitative bioanalytical method using BMS-186716-AA as the analyte instead of the originally planned BMS-186716-MA analyte. The standard and quality-control (QC) samples were prepared by spiking blank plasma with BMS-186716-MA, and then allowing them to stand at room temperature for 1 h to convert BMS-186716-MA to BMS-186716-AA. After adding the internal standard BMS-188035-AA, each sample was acidified with HCl and then extracted with methyl tert.-butyl ether. The reconstituted extract was injected into a HPLC-electrospray ionization mass spectrometric system for detection by positive ion electrospray ionization. A lower limit of quantitation (LLQ) of 5 ng/ml was achieved, using 0.1 ml plasma and a standard curve range of 5-5000 ng/ml.

Acrylates↗
PubMedDate not supplied

Semiautomatic determination of furanic aldehydes in food and pharmaceutical samples by a stopped-flow injection analysis method.

A kinetic study of the reactions of 5-hydroxymethyl-2-furfuraldehyde and furfural with 2-thiobarbituric acid (TBA) by a stopped-flow flow injection analysis technique has been undertaken. A semiautomatic method for the analytical determination of these furanic aldehydes is proposed on the basis of reaction with TBA. The proposed stopped-flow method was successfully applied to several commercial pharmaceutical preparations and food samples. The procedure is faster than the earlier procedure for determination of these compounds in foods and pharmaceuticals.

Calibration↗
PubMed2000

Polycyclic aromatic hydrocarbons in edible fats and oils: occurrence and analytical methods.

This review deals with analytical methods for polycyclic aromatic hydrocarbon (PAH) determination in oils and fats. The data reported in the introduction deal with PAH dietary intake from this group of food and contamination levels recently found by some authors in different vegetable oils, stressing the importance of establishing a method suitable for routine analyses. Traditional sample preparation relies on tedious, time-consuming procedures. They generally consist of an extraction step (liquid-liquid partition, caffeine complexation, saponification) followed by one or more purification procedures (column chromatography, thin-layer chromatography, solid-phase extraction). The analytical determination is usually carried out by HPLC and spectrofluorometric detection, or through high-resolution capillary GC coupled to flame ionisation detection or mass spectrometry. LC is a valid alternative to the traditional sample preparation, and off-line LC-LC allows performing an accurate PAH analysis in less than 2 h. Also supercritical fluid extraction, allowing performing both extraction and clean-up in one combined step, is a promising technique. Hyphenated techniques such as LC-GC and LC-LC-GC seem to be very promising. A completely on-line method for alkylated PAH determination in oils or lipidic extracts contaminated with mineral oil involves a two-dimensional LC-step with intermediate eluent evaporation and GC transfer through a vaporiser/overflow interface.

Chromatography, Gas↗
PubMed2002

A simplified liquid-solid extraction technique for the analyses of pesticide residues in soil samples.

A simplified liquid-solid extraction technique was studied for the analyses of pesticide residues in soil samples. It is a simple, one step sample preparation method based on a relative quantification concept. Linear response curves were obtained for all of the target compounds regardless of their surface adsorption. This observation was explained and modeled to obey Langmuir adsorption Equation. The adsorption of analytes onto the sample surfaces will sacrifice the detection sensitivity. The strategies to reduce the surface adsorption, such as, molecular replacement and selection of solvents, were discussed. The relative quantification and the wide varieties of available solvents would enable the technique to be a useful method for the monitoring and analyses of pesticide residues in soils.

Adsorption↗
PubMed2004

Simple reversed-phase ion-pair liquid chromatography assay for the simultaneous determination of mycophenolic acid and its glucuronide metabolite in human plasma and urine.

A simple and reproducible reversed-phase ion-pair high-performance liquid chromatographic (HPLC) method using isocratic elution with UV absorbance detection is presented for the simultaneous quantitation of mycophenolic acid (MPA) and MPA-glucuronide (MPAG) in human plasma and urine. The sample preparation procedures involved simple protein precipitation for plasma and 10-fold dilution for urine. Each analytical run was completed within 15min, with MPAG and MPA being eluted at 3.8 and 11.4min, respectively. The optimized method showed good performance in terms of specificity, linearity, detection and quantitation limits, precision and accuracy. This assay was demonstrated to be applicable for clinical pharmacokinetic studies.

Buffers↗
PubMed1996

High-pressure liquid chromatographic assay for the determination of thyrotropin-releasing hormone and its common metabolites in a physiological salt solution circulated through the isolated perfused rat lung.

A specific and sensitive assay for TRH (L-pyroglutamyl-L-histidyl-L-proline amide), 3H-TRH (L-proline 3,4-3H(N), histidyl-3-3H(N)), and four possible metabolites of TRH, present in the recirculated perfusate of an isolated perfused rat lung preparation, was developed. Unlike previous methods, the method developed does not require extraction of the analytes from the biological matrix. The crude sample was adjusted to a pH of 3.2 with concentrated trifluoroacetic acid and injected on to a PRP-1 (polystyrene divinylbenzene) column (10 microns, 25 cm x 4.6 mm i.d.). The mobile phase was 10% v/v acetonitrile and 90% v/v 0.75 g l-1 1-hepantanesulfonic acid in 0.004 M trifluoroacetic acid, adjusted to a pH of 2.4 with concentrated NaOH. The flow rate was 0.5 ml min-1 and the analytes were detected by UV absorption at a wavelength of 26 nm and by radiochemical detection utilizing a liquid scintillation counter. The nominal retention times for L-PRO, L-PRO-NH2, TRH, cyclo(HIS-PRO) and TRH-OH were 4.0 +/- 0.9, 10.0 +/- 0.2, 15.5 +/- 0.4, 19.2 +/- 0.5 and 25.3 +/- 0.5 min respectively. The assay performs well in terms of precision and accuracy as indicated by linear regression and intra-assay variability analysis.

Animals↗
PubMed2005

Application of solid-phase microextraction to in vitro skin permeation experiments: example using diethyl phthalate.

The application of automated solid-phase microextraction (SPME) as a sample preparation technique for in vitro studies of skin permeation is described, using diethyl phthalate (DEP) as an example. In vitro diffusion cell experiments and skin-vehicle partition coefficient determinations require quantitative analysis of low-level analytes in aqueous samples. SPME is an ideal candidate for sample preparation for subsequent gas chromatographic analysis, offering numerous advantages over other methods. SPME conditions were optimized and the automated method was found to exhibit adequate sensitivity and good precision (relative standard deviation=3%). Abdominal skin (dermatomed at 350 microm) from male hairless guinea pigs (n=6) was used to measure DEP skin permeation parameters. In vitro methods were employed to determine permeability coefficient (k(p)), time lag (tau) and skin-buffer partition coefficient (K(SB)) for 2 mM DEP in HEPES buffered Hanks Balanced Salt Solution. Measurements (mean+/-standard deviations) are: k(p), 0.021+/-0.012 cm/h; tau, 0.67+/-0.18 h; K(SB), 4.74+/-0.68. The skin may be a significant route for the uptake of DEP.

Animals↗
PubMed1998

Use of paraffin wax film in MALDI-TOF analysis of DNA.

Poor detection limits and strong salt effects are two of the main problems encountered in the matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometric analysis of DNA. This work demonstrates that a probe tip with a paraffin wax film (Parafilm) surface improves the MALDI performance in DNA analysis compared to the commonly used metal surface. First, the use of Parafilm increases the detection sensitivity. It was found that the detection limit achieved with Parafilm was 5 times better than that obtained using stainless steel for a 85mer. More importantly, the Parafilm method could improve detection of larger DNA components in the presence of a large excess of a smaller DNA component or in a DNA mixture. This feature is important to analyses of PCR and sequencing products. Second, we found that the use of Parafilm increased the salt tolerance limits for the 17-, 41-, and 85mers studied in this work and that the salt effect was less sensitive to the DNA size. Third, this method offers other analytical benefits, including producing a more homogeneous coverage of matrix/DNA, adding no extra cost and time to sample preparation, and eliminating the commonly required step for cleaning the probe after analysis. In this paper, we will also present our perspectives on why the use of Parafilm can improve the MALDI-TOF performance in DNA analysis.

DNA↗
PubMed1986

Biological monitoring for heavy metals: practical concerns.

Some of the practical concerns associated with performing routine analyses of heavy metals (cadmium, lead, mercury, and arsenic) in various biological matrices are the selection of the biological matrix for monitoring, the sample collection, sample storage and shipment, and sample preparation and analysis. Other factors that affect the quality of the analytical values include contamination of sampling materials, blood drawing procedures, methods of obtaining urine samples, sample homogeneity, instrument calibration and performance, and laboratory quality control programs. A total system quality control approach is necessary to obtain accurate analyses of metals in biological samples, just as it is in all analytical situations.

Arsenic↗
PubMed2005

41Ca and accelerator mass spectrometry to monitor calcium metabolism in end stage renal disease patients.

BACKGROUND: Monitoring bone resorption with measurements of bone density and biochemical markers is indirect. We hypothesized that bone resorption can be studied directly by serial measurements of the ratio (41)Ca/Ca in serum after in vivo labeling of calcium pools with (41)Ca. We report the preparation of an intravenous (41)Ca dose suitable for humans, an analytical method for determining (41)Ca/Ca isotope ratios in biological samples, and studies in human volunteers. METHODS: (41)Ca was formulated and aliquoted into individual vials, and to the extent possible, the (41)Ca doses were tested according to US Pharmacopeia (USP) guidelines. A 10 nCi dose of (41)Ca was administered intravenously to 4 end stage renal disease (ESRD) patients on hemodialysis and 4 healthy control individuals. Distribution kinetics were determined over 168 days. Calcium was isolated with 3 precipitation steps and a cation-exchange column, and (41)Ca/Ca ratios in serum were then measured by accelerator mass spectrometry. RESULTS: The dosing solution was chemically and radiologically pure, contained <0.1 endotoxin unit/mL, and passed USP sterility tests. Quantification of (41)Ca/Ca ratios was linear from 6 x 10(-14) to 9.1 x 10(-10). The run-to-run imprecision (as CV) of the method was 4% at 4.6 x 10(-11) and 6% at 9.1 x 10(-10). The area under the curve of (41)Ca in the central compartment vs time was significantly less for ESRD patients than for controls (P < 0.005). CONCLUSIONS: Isotope ratios spanning 5 orders of magnitude can be measured by accelerator mass spectrometry with excellent precision in the range observed in samples collected from patients who have received 10 nCi of (41)Ca. The (41)Ca at this dose caused no adverse effects in 8 volunteers. This is the first report of the use of (41)Ca to monitor differences in bone turnover between healthy individuals and ESRD patients.

Bone and Bones↗
PubMed2001

Investigation of atrazine metabolism in river sediment by high-performance liquid chromatography/mass spectrometry.

Microbial degradation processes play an important role in chemical water clearance taking place in river sediments. Bacteria remove not only easily degradable organic species, but various xenobiotics as well, producing clear and xenobiotic free water for bank-filtered wells. Atrazine is a widely used herbicide, and it is one of the most common xenobiotics present in Danube water. In this study the pathway and kinetics of atrazine metabolism of sedimental microbiota were studied. Samples were collected from river sediment and from pure microbial growth cultures. An analytical scheme including sample preparation, chromatography and mass spectrometry was developed and optimised. Solid-phase extraction (SPE) was found to be satisfactory for sample preparation. For qualitative analysis of samples both reversed-phase and normal-phase high-performance liquid chromatography/mass spectrometry (HPLC/MS) methods were developed and used. Selectivity, detection limits and accuracy of the two methods were compared. Using this analytical scheme, the full atrazine metabolism of the organism Comamonas acidovorans was explored. Altogether, 12 metabolites were identified from the original compound to the urea end product. Detection limits in the range of 50 ng L(-1)-1 microg L(-1) were obtained for different metabolites.

Atrazine↗
PubMed2005

Analysis of omeprazole, midazolam and hydroxy-metabolites in plasma using liquid chromatography coupled to tandem mass spectrometry.

A method has been developed and validated for the quantitation of midazolam, alphahydroxy-midazolam, omeprazole, and hydroxyomeprazole from one 250 microL sample of human plasma using high performance liquid chromatography coupled to tandem mass spectrometry. The method was validated for a daily working range of 0.400-100 ng/mL, with limits of detection between 2 and 15 pg/mL. The inter-assay variation was less than 15% for all analytes at four control concentrations and the samples were stable for three freeze-thaw cycles under the analysis conditions and 24 h in the post-preparative analysis matrix. This method was used to analyze samples in support of clinical studies probing the activity of the cytochrome P-450 enzyme system.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed2000

Evaluation of ursodeoxycholic acid bioavailability from immediate- and sustained-release preparations using gas chromatography-mass spectrometry and high-performance liquid chromatography.

An improved procedure is presented for the determination of ursodeoxycholic acid (CAS 128-13-2, UDCA) in human plasma and bile after oral administration of UDCA-containing dosage forms. The plasma samples after solid-phase extraction with silica-based C18- and strong anion exchange cartridges were assayed by gas chromatography-mass spectrometry (GC-MS) using selected-ion monitoring. The hexafluoroisopropyl trifluoroacetate ester derivative of UDCA was selected for GC analysis since it is easily and rapidly prepared by a one-step reaction. Biliary UDCA levels were determined by a rapid and simple high-performance liquid chromatographic (HPLC) method with on-line sample purification. This analytical protocol was used to investigate the pharmacokinetic of a new sustained-release capsule of UDCA in comparison with a reference immediate-release preparation after single oral administration. Statistical evaluation of the area under the plasma concentration-time curves indicated that two formulations are equivalent with regard to the amount of drug absorbed. However, pharmacokinetic data showed that with the sustained-release preparation a significantly delayed mean peak plasma level was reached compared with the reference preparation. Moreover, the immediate- and extended-release capsules were found to achieve a comparable degree of biliary enrichment with UDCA.

Adult↗
PubMed2000

Laboratory database to manage electrophoresis and chromatography separations and the associated samples.

A database was developed to store, organize, and retrieve the data associated with electrophoresis and chromatography separations. It allows laboratories to store extensive data on separation techniques (analytical and preparative). The data for gel electrophoresis includes gel composition, staining methods, electric fields, analysis, and samples loaded. The database stores data on chromatography conditions, the samples used, and the fractions collected. The data structure of this database was designed to maintain the link between samples (including fractions) from chromatography separations and their analysis by gel electrophoresis. The database will allow laboratories to organize and maintain a large amount of separation and sample data in a uniform data environment. It will facilitate the retrieval of the separation history of important samples and the separation conditions used.

Chromatography↗
PubMed2000

A RIA combined with SPE for the determination of a dual D2-receptor and beta2-adrenoceptor agonist, AR-C68397XX, in human plasma.

A radioimmunoassay has been developed for the determination of AR-C68397XX, a dual D2-receptor and beta2-adrenoceptor agonist, in human plasma. The method incorporates solid phase sample extraction and is suitable for the determination of the analyte at pg ml(-1) concentrations. The antiserum was raised in Suffolk cross sheep following primary and booster immunisations with an immunogen prepared by conjugating a carboxyphenylmethyl derivative of AR-C68397XX, to bovine serum albumin. The radioligand was prepared by the 125I-labelled iodination of a derivative of AR-C68397XX. The solid phase extraction procedure, using octadecyl sorbent, was introduced to remove matrix interferences in the plasma and to enhance method sensitivity. The calibration range is 20-500 pg ml(-1), using 0.5 ml of undiluted human plasma sample.

Adrenergic beta-2 Receptor Agonists↗