Use of an ion-exchange membrane for sample pretreatment of ion chromatography: determination of phosphate ion and sulfate ion in deep subsurface water.
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Anion Exchange Resins↗
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Results for “Sample pretreatment”
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HPLC sample pretreatment and preparation.
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Chromatography, High Pressure Liquid↗
Determination of drugs in blood samples by high performance liquid chromatography using on-line sample pretreatment technique.
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Chromatography, High Pressure Liquid↗
Estradiol-17 beta quantified in serum by isotope dilution-gas chromatography-mass spectrometry: reversed-phase C18 high-performance liquid chromatography compared with immuno-affinity chromatography for sample pretreatment.
Here, isotope dilution-gas chromatography-mass spectometry is used as a reference technique for determining the concentration of estradiol-17 beta in candidate human serum Reference Material. The accuracy of assigned concentrations in biologic materials is not only determined by instrumental performance, it also depends greatly on the selectivity of the procedure for isolating the analyte from the biological matrix, an issue which we consider insufficiently addressed in the literature. We introduced reversed-phase C18 high-performance liquid chromatography as a fractionation procedure in addition to the commonly used solvent extraction and column chromatography on Sephadex LH-20. The validity of this approach as part of a Reference Method for measurement of estradiol-17 beta by isotope dilution-gas chromatography-mass spectrometry was investigated by comparison with immuno-affinity chromatography, which on theoretical grounds is generally considered as highly selective.
Chromatography, Affinity↗
Effect of pretreating samples with boric acid before liquid-chromatographic determination of urinary catecholamines.
Isolation of catecholamines on prepacked gravity-fed ion-exchange columns in conjunction with liquid-chromatographic separation is occasionally subject to disturbances of unknown origin, especially after injection of H3BO3 eluates from the ion-exchange columns onto the chromatography column. Peak spreading, sometimes even peak splitting, has been observed in many laboratories--effects easily confused with those sometimes caused by voided columns or by impurities. To elucidate the origins of these interferences, we performed a combined voltammetric and chromatographic investigation. We show that complexation of the catechol group by borate ions and dissociation of those pH-labile complexes in the course of the chromatographic separation is the cause of those peak distortions. Addition of a small volume of diluted HCI to the borate eluates eliminates such interference and leads to reproducible, easily interpretable chromatographic separations.
Boric Acids↗
Urine organic acid profiling by capillary gas chromatography after a simple sample pretreatment.
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Adult↗
Simultaneous determination of carbamazepine, phenytoin, phenobarbital, primidone and their principal metabolites by high-performance liquid chromatography with photodiode-array detection.
We have established a precise and accurate high-performance liquid chromatographic method for the simultaneous assay of carbamazepine, phenytoin, phenobarbital, primidone and their principal metabolites. This method has been used for the analysis of these drugs and the metabolites in serum, saliva and urine samples. Acetonitrile is used for the deproteinization of serum and saliva samples while solid-phase extraction is utilized for urine sample pretreatment. Samples of 2 microliters are injected onto a 3-microns ODS-Hypersil column (250 mm x 2 mm I.D.) with a column temperature of 40 degrees C. The drugs and metabolites are eluted with a mobile phase containing potassium phosphate buffer-acetonitrile-methanol (110:50:30, v/v/v) at a flow-rate of 0.2 ml/min. Signals are monitored by a photodiode-array detector at a sample wavelength of 200 nm with a bandwidth of 10 nm. These four commonly used antiepileptic drugs and their six metabolites are well separated from one another within 15 min. Within-day coefficients of variation (C.V.) are within 5% in most cases and between-day C.V. are from 2.32 to 4.75%. The recovery rates range from 95.12 to 104.42%. This method has the necessary sensitivity and linearity for routine therapeutic monitoring of both total and free drug levels and may be employed for pharmacokinetics studies of drug interactions and metabolism as well.
Anticonvulsants↗
Aminoalkyl affinity matrices.
Aminoalkyl matrices are used in affinity chromatography of amine oxidases and other proteins with affinity for amino groups. Under appropriate circumstances chromatography on aminoalkyl matrices may yield purification factors around 100 to 1000, and they have been used in affinity purification of many members of the amine oxidase family. Other proteins with affinity for aminoalkyl matrices include thiol ester proteins, lactoferrin, and proteins with lysine-binding kringles (plasminogen, plasminogen activator, apolipoprotein A). The affinity of thiol ester proteins for aminoalkyl matrices is abolished after inactivation of the thiol ester group by reaction with low molecular weight amines including ammonia. Due to this, an ammonium sulphate precipitation step should be included in purification schemes for amine oxidases. The affinity of lactoferrin for aminoalkyl matrices stems from an affinity for the repeating amino groups in glycosaminoglycans, and this explains why lactoferrin requires diamines for efficient elution. The affinity of plasminogen for aminoalkyl groups is exploited in a one-step purification from plasma, and is also utilised in purification schemes for angiostatin, an angiogenesis-inhibiting fragment of plasminogen. Apolipoprotein A is homologous to plasminogen, and also has affinity for aminohexyl columns. The common binding motif for these proteins are lysine-binding kringles. Due to the properties of the amino group itself, aminoalkyl matrices will inevitably also function as anion exchangers, and this must be taken into consideration in the choice of conditions for sample loading, column washing and elution of bound proteins. Depending on the length of the alkyl chain, the matrices also have a potential for hydrophobic interactions. This property has been exploited in the purification of several proteins but must be minimized during affinity chromatography of amine oxidases. In conclusion, aminoalkyl matrices are valuable tools for affinity chromatography of several different proteins, and simple variations of sample pretreatment, sample loading, and column washing and elution conditions allow efficient selective purification of proteins with different affinities for the matrices.
Ammonium Sulfate↗
Evaluation of a novel malathion immunoassay for groundwater and surface water analysis.
Malathion is an organophosphorus insecticide commonly used in crops and indoor applications. Negative effects of malathion on human health and ecosystems are of growing concern. In this work, novel malathion haptens are synthesized to develop an ELISA screening method. The immunoassay is based on a conjugate-coated format and shows a limit of detection of 0.11 ng/mL, an IC50 of 1.58 ng/mL, a dynamic range between 0.23 and 10.94 ng/ mL, and a cross-reactivity of <2% with structurally related compounds. The developed ELISA has been used to quantify malathion in groundwater and surface water samples. The good recoveries achieved and the agreement with those given by the GC-MS reference method indicate the potential of the assay for environmental monitoring of malathion in natural waters without purification or preconcentration steps. The effect of dissolved organic matter (humic acids) on the ELISA was evaluated, resulting in the conclusion that the immunoassay can be successfully performed in surface water samples with a humic acid content up to 10 mg/L, without sample pretreatment. Samples with a high humic acid content can be analyzed through ELISA after solid-phase extraction, eluting with acetone or acetonitrile.
Acetone↗
Association between cigarette smoking and urinary excretion of 1,N2-ethenoguanine measured by isotope dilution liquid chromatography-electrospray ionization/tandem mass spectrometry.
Levels of the promutagenic 1,N2-ethenoguanine (1,N2-epsilonGua), an etheno DNA adduct derived mainly from lipid peroxidation, in experimental animals are associated with risk of cancer formation. Since 1,N2-epsilonGua can be repaired by human glycosylases, it is possible to use it as a biomarker for cancer risk assessment in humans. In the present study, a highly sensitive and specific stable isotope dilution liquid chromatography-electrospray ionization/tandem mass spectrometry (LC-ESI/MS/MS) was developed for accurate quantification of 1,N2-epsilonGua in human urine. The sample pretreatment involved a consecutive strong cation exchange solid-phase extraction (SPE) and reversed phase SPE chromatography. The pretreated sample was analyzed by LC-ESI/MS/MS under multiple reaction monitoring mode (MRM) using a triple quadrupole mass spectrometer. The detection limit of 1,N2-epsilonGua using this LC-ESI/MS/MS assay was 1.0 pg (5.8 fmol) injected on-column. Levels of urine samples collected from healthy volunteers were found to range from 0 to 199 pg/mL, and levels as low as 5.0 pg/mL (29 pM) could be accurately quantified. After adjusting for creatinine levels and body weight, an statistically significant association was observed between urinary levels of 1,N2-epsilonGua and cigarette smoking (p = 0.0006). This highly specific and sensitive assay should be valuable in measuring urinary 1,N2-epsilonGua as a potential noninvasive biomarker for oxidative DNA damage.
Adult↗
Direct introduction of large-volume urine samples into an on-line immunoaffinity sample pretreatment-capillary gas chromatography system.
An immunoaffinity precolumn containing immobilized antibodies raised against the synthetic steroid hormone beta-19-nortestosterone, has been used for the automated sample pretreatment of urine samples containing beta-19-nortestosterone or the related steroids norethindrone and norgestrel. The sample pretreatment system was coupled on-line to a capillary GC. The on-line connection between the immunoaffinity precolumn and the capillary GC was realized with an interface that consisted of a 10 mm X 2 mm i.d. reversed-phase pre-column and a diphenyltetramethyldisilazane-deactivated GC retention gap. After preconcentration on the immunoaffinity precolumn the analytes were eluted and reconcentrated on the reversed-phase precolumn. Subsequently, this precolumn was desorbed with 75 microL of ethyl acetate, which was directly introduced into the retention gap by using partially concurrent solvent evaporation. The system allows the automated pretreatment and GC analysis of 5-25-mL urine samples for the ppt-level determination of 19-norsteroids. The general applicability and potential of on-line immunoaffinity-capillary GC systems are discussed.
Chromatography, Affinity↗
Analysis of Ecteinascidin 743, a new potent marine-derived anticancer drug, in human plasma by high-performance liquid chromatography in combination with solid-phase extraction.
A reversed-phase high-performance liquid chromatographic method has been developed and validated for the quantification of the novel anticancer drug Ecteinascidin 743 in human plasma. The sample pretreatment of the plasma samples involved a solid-phase extraction (SPE) on cyano columns. Propyl-p-hydroxybenzoate was added after the sample pretreatment to correct for variability in injection volumes. The separation was performed on a Zorbax SB-C18 column (75x4.6 mm I.D., particle size 3.5 microm) with acetonitrile-25 mM phosphate buffer, pH 5.0 (70:30, v/v) as the mobile phase. The flow-rate was 1.0 ml/min and the eluent was monitored at 210 nm. The accuracies and precisions of the assay fall within +/-15% for all quality control samples and within +/-20% for the lower limit of quantitation, which was 1.0 ng/ml using 500 microl of plasma. The overall recovery of the sample pretreatment procedure for Ecteinascidin 743 was 87.0+/-5.9%. The drug was found to be stable in human plasma at -30 degrees C for at least 2 months. At room temperature Ecteinascidin 743 was stable in human plasma for 5 h at most.
Animals↗
Determination of clenbuterol in bovine liver by combining matrix solid-phase dispersion and molecular imprinted solid-phase extraction followed by liquid chromatography/electrospray ion trap multiple-stage mass spectrometry.
Matrix solid-phase dispersion (MSPD) is a new sample pretreatment for solid samples. This technique greatly simplifies sample pretreatment but, nonetheless, the extracts often still require an extra cleanup step that is both laborious and time-consuming. The potential of combining MSPD with molecularly imprinted solid-phase extraction (MISPE) was investigated in this study. Liver samples were ground in a mortar with C18 sorbent and the homogenized mixture packed into an SPE cartridge and placed on top of a MISPE cartridge. Subsequently, clenbuterol was eluted from the MSPD cartridge onto the MISPE cartridge using acetonitrile containing 1% acetic acid. The ability of the molecularly imprinted polymer to selectively adsorb analyte in acetonitrile was exploited for re-extracting clenbuterol directly from this acetonitrile extract via the double cartridge tandem system. The analyte was eluted from the MISPE cartridge using acidified methanol. A clear eluate was obtained, which was subsequently evaporated, redissolved, and analyzed by HPLC electrochemical detection (ECD) or ion trap mass spectrometry (LC/IT-MS). The MISPE cartridge used in this study was imprinted using bromoclenbuterol, a structural analogue of clenbuterol, as the template. These MISPE cartridges showed excellent stability. The complete extraction procedure was rapid, and recoveries exceeded 90% for the target analyte. The method detection limit for the LC/IT-MS procedure was < 0.1 microg/kg. This method, therefore, satisfies the stringent requirements of European Union regulation EEC 2377/90.
Adrenergic beta-Agonists↗
Determination of alpha-fetoprotein in human serum by a quartz crystal microbalance-based immunosensor.
BACKGROUND: Increased alpha-fetoprotein (AFP) in adult plasma is considered an early indication of hepatocellular carcinoma and teratoblastoma. The aim of this study was to develop a rapid method to measure AFP in human serum by use of a direct immunosensor based on a quartz crystal microbalance (QCM). METHODS: A self-assembled monolayer prepared by the cystamine method was applied to immobilize anti-AFP monoclonal antibodies on the gold surface of a quartz crystal. The frequency shifts of the QCM were measured and related to AFP concentrations. The piazoimmunosensor used no labeled reagent and no pretreatment of samples. RESULTS: Ten cycles of measurements could be performed on the gold surface of the same crystal regenerated with a solution of glycine-HCl. A linear relationship existed between the frequency shifts (Hz) and the log values of AFP concentrations from 0.1 to 100 microg/L in buffer and human serum. When used for 15 days, the frequency shifts were all >95% of those on the response at the first day. The regression equation was y = 1.03x - 0.06 (S(y/x) = 3.92; r = 0.9987) for this QCM method and RIA in 29 clinical human serum samples. CONCLUSIONS: The QCM sensor can measure AFP in buffer and human serum and offers advantages of high specificity, reusability, low detection limit, no label or sample pretreatment, and low sample requirement. The assay format of the immunosensor was more rapid and simpler than conventional methods.
Antibodies, Monoclonal↗
Blood pressure responsiveness to obstructive events during sleep after chronic CPAP.
The aim of this study was to investigate whether chronic continuous positive airway pressure (CPAP) affects blood pressure (BP) responsiveness to obstructive events occurring on the first night of CPAP withdrawal in obstructive sleep apnoea (OSA) after chronic treatment. Thirteen male subjects with severe OSA underwent nocturnal polysomnography with beat-by-beat BP monitoring before treatment and after 4.9 +/- 3.4 months of home CPAP (mean daily use 5.1 +/- 1.7 h). Variations in oxyhaemoglobin saturation (deltaSa,O2), systolic (deltaPs), and diastolic (deltaPd) BP within nonrapid eye movement apnoeas and hypopnoeas were measured on a sample of pre- and post-treatment events. In addition, a pretreatment sample was selected for deltaSa,O2 to match post-treatment events. The higher the mean deltaSa,O2 was in the full pretreatment sample, the more deltaSa,O2, deltaPs and deltaPd were attenuated after treatment. Mean deltaPs decreased from 47.3 +/- 8.5 in the full pretreatment sample to 42.2 +/- 6.9 in the selected pretreatment sample, to 31.5 +/- 5.9 mmHg in the post-treatment sample. The post-treatment value differed significantly from both the pretreatment values. The corresponding values for mean deltaPd were 27.0 +/- 3.5, 24.0 +/- 3.1 and 19.6 +/- 3.7 mmHg, with all values differing significantly from each other. Chronic continuous positive airway pressure is followed by a decrease in apnoea/ hypopnoea-related blood pressure swings, possibly secondary to both reduced severity of event-related hypoxaemia and decreased responsiveness to obstructive events secondary to chronic prevention of nocturnal intermittent hypoxaemia.
Adult↗
Measurements using gas chromatography with coelution and dual-isotope atomic emission detection.
Dual-isotope measurements by gas chromatography (GC)-atomic emission detection (AED) may enhance results for quantitative analyses. Adding a known amount of an isotopically labelled form of target analytes in each sample can compensate for irreproducibilities or uncertainties associated with sample pretreatments and sample loading. Similarly, fluctuations in AED temperatures, flows and interferants can be compensated via the added labelled forms if each target analyte and its isotopically labelled form coelute. Under these conditions they are subject to identical excitation environments and are measured from the same viewed volumes. Consequently, improved quantitative results may be attained by coelution in GC-AED methods which mimic isotope dilution.
Gas Chromatography-Mass Spectrometry↗
Bio-analysis of docetaxel and hydroxylated metabolites in human plasma by high-performance liquid chromatography and automated solid-phase extraction.
A semi-automated reversed-phase high-performance liquid chromatography (HPLC) method has been developed and validated for the quantification of the novel anticancer drug docetaxel in human plasma. The chromatographic system also separated putative hydroxylated metabolites. A limited validation was performed for the assay of the metabolites while these reference compounds were not available in large quantities. The sample pretreatment of the plasma samples involves a solid-phase extraction (SPE) on Cyano end-capped columns. 2'-Methylpaclitaxel was used as internal standard. An APEX-octyl column (150 x 4.6 mm I.D.; particle size 5 microns) was used with acetonitrile-0.02 M ammonium acetate buffer pH 5 mixture as the mobile phase. UV detection was performed at 227 nm. In patient samples hydroxylated docetaxel metabolites were detected and quantified by using the docetaxel calibration curve. The accuracies and precisions of the assay fall within +/- 15% for all quality control samples and within +/- 20% for the lower limit of quantitation, which was 10 ng/ml using 1.00 ml of sample for both the parent drug and its metabolites. The overall recovery of the sample pretreatment procedure for docetaxel was 78.0% +/- 5.8% anc 84.8% +/- 3.1% for the internal standard 2'-methylpaclitaxel. Docetaxel was found to be stable in human plasma at -30 degrees C for at least 6 months. At ambient temperature docetaxel was stable for at most 15 h in human plasma.
Antineoplastic Agents, Phytogenic↗
Determination of iron, cobalt, copper, zinc, rubidium, molybdenum, and cesium in human serum by inductively coupled plasma mass spectrometry.
A method was developed for the determination of seven trace elements (Fe, Co, Cu, Zn, Rb, Mo, and Cs) in human serum by inductively coupled plasma mass spectrometry (ICP-MS). Sample preparation was kept as limited as possible. As the only sample pretreatment serum samples were diluted with nitric acid and indium was added as an internal standard. The results for iron, cobalt, copper, and zinc were corrected for interferences from polyatomic ions by using a blank solution containing the same concentration of sodium, sulfur, chlorine, and calcium as human serum. For copper and zinc the corrections are small, whereas for iron and cobalt they are important. No interferences occur for the considered isotopes of rubidium, molybdenum, and cesium. In order to test the accuracy and precision of the analytical technique, a "second-generation biological reference material (human serum)" was analyzed. The results obtained by ICP-MS for the seven elements considered showed good agreement with the certified values.
Humans↗