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PubMed2003

Determination of uric acid in human saliva by high-performance liquid chromatography with amperometric electrochemical detection.

The aim of the present study is to establish a highly sensitive method for the determination of uric acid (UA) in human saliva. The monitoring of UA levels in less invasive biological samples such as saliva is suggested for the diagnosis and therapy of gout, hyperuricemia, and the Lesch-Nyhan syndrome, and for detecting such conditions as alcohol dependence, obesity, diabetes, high cholesterol, high blood pressure, kidney disease, and heart disease. Reversed-phase high-performance liquid chromatography with electrochemical detection (HPLC-ED) was employed for the determination of UA obtained by solid-phase extraction from saliva. To quantify UA, we compared the ED efficiencies of an amperometric ED (Ampero-ED) with a single electrode and a coulometric ED (Coulo-ED) with a multiple electrode array. The results showed that the detection limits (S/N=3) were 3 nM for Ampero-ED and 6 nM for Coulo-ED, and the linearity of the calibration curves of 60-6000 nM had correlation coefficients exceeding 0.999. In addition, the total analytical time was 10 min. In the sample preparation of UA in saliva, an Oasis MAX solid-phase cartridge was used. The recoveries of UA spiked at 0.6 and 3 microM in saliva were above 95% with a relative standard deviation (RSD) of less than 15%. Therefore, the present method may be used in the routine and diagnostic determination of UA in human saliva.

Chromatography, High Pressure Liquid↗
PubMed2004

Improved detectability with a polymer-based trapping device in rapid HPLC analysis for ultra-low levels of bisphenol A (BPA) in environmental samples.

A new high-performance liquid chromatography (HPLC) method has been developed to detect ultra-low concentrations of bisphenol-A (BPA) (below 1 ng/L (ppt)) using column switching electrochemical detection (ECD). The results were superior to those obtained from manual pretreatment procedure with membrane stationary phase. BPA is inherently ubiquitous in the environment, including tools and solvents used for its analysis; to obtain meaningful results, therefore, the concentration of the overall BPA contamination must be below the detection limit for BPA using the analytical system. Therefore, purified water for preparing the standard BPA solution must be filtered with a hydrophobic membrane to suppress BPA background levels of contamination. In addition, we investigated methods for effectively preserving environmental water containing BPA. The addition of a small amount of ethylenediaminetetraacetic acid (EDTA) provided good recovery even after overnight storage. By employing these precautionary measures and procedures to reduce BPA contamination from the analytical procedure, we could accurately determine l(-10) ppt of BPA in environmental water samples using a column switching HPLC system.

Benzhydryl Compounds↗
PubMed1988

Determination of cyanide and cyanogenic compounds in biological systems.

A survey of methods for the qualitative and quantitative determination of cyanide and cyanogenic compounds is presented. Particular attention is paid to determination in complex matrices. Chromatographic methods able to separate mixtures of closely related structures, such as glycosides of enantiomeric hydroxynitriles or lipids with slightly differing fatty acid spectra, are included, as are highly selective methods of detection, such as enzymic post-column cleavage combined with electrochemical detection as used in high-performance liquid chromatography. Details of thin-layer chromatography, including methods for detection, are given for both straight-phase and reverse-phase systems. The survey includes simple field methods as well as automated laboratory methods for the determination of 'free', 'bound' and 'total' cyanide, for example in processed food products from Manihot esculenta Cranz. Sources of enzymes are listed and attention is given to problems of sample storage and preparation. References are given to review articles which include data from methods such as ultraviolet, infrared and proton and carbon-13 nuclear magnetic resonance spectroscopies.

Chemistry Techniques, Analytical↗
PubMed1976

Doping control in Japan. An automated extraction procedure for the doping test.

Horse racing in Japan consists of two systems, the National (10 racecourses) and the Regional public racing (32 racecourses) having about 2,500 racing meetings in total per year. Urine or saliva samples for dope testing are collected by the officials from thw winner, second and third, and transported to the laboratory in a frozen state. In 1975, 76, 117 samples were analyzed by this laboratory. The laboratory provides the following four methods of analysis, which are variously combined by request. (1) Method for detection of drugs extracted by chloroform from alkalinized sample. (2) Methods for detection of camphor and its derivatives. (3) Method for detection of barbiturates. (4) Method for detection of ethanol. These methods consist of screening, mainly by thin layer chromatography and confirmatory tests using ultra violet spectrophotometry, gas chromatography and mass spectrometry combined with gas chromatography. In the screening test of doping drugs, alkalinized samples are extracted with chloroform. In order to automate the extraction procedure, the authors contrived a new automatic extractor. They also devised a means of pH adjustment of horse urine by using buffer solution and an efficient mechanism of evaporation of organic solvent. Analytical data obtained by the automatic extractor are presented in this paper. In 1972, we started research work to automate the extraction procedure in method (1) above, and the Automatic Extractor has been in use in routine work since last July. One hundred and twnety samples per hour are extracted automatically by three automatic extractors. The analytical data using this apparatus is presented below.

Animals↗
PubMed2004

Quantitative determination of MK-0767, a dual alpha/gamma peroxisome proliferator-activated receptor (PPAR) agonist, in human plasma by liquid chromatography-tandem mass spectrometry.

5-[2,4-Dioxothiazolidin-5-yl)methyl]-2-methoxy-N-[[(4-trifluoromethyl)-phenyl]methyl]benzamide (I, MK-0767 or KRP-297, Fig. 1), is a dual alpha/gamma peroxisome proliferator-activated receptor (PPAR) agonist. A LC-MS/MS method for the determination of I in human plasma has been successfully developed, validated and applied to clinical programs. The analyte and internal standard (II) are extracted from 0.05 mL plasma via solid phase extraction (SPE). HPLC is used for the separation of I and II from possible co-extracted endogenous and other compounds. Detection is by MS/MS in multiple reaction monitoring (MRM) mode using a TurboIonSpray probe. The whole sample preparation is automated by using a Packard Multiprobe liquid handling system. The linear range is 4-2000 ng/mL in plasma. Recoveries were 71.1% and 69.4% for I and II, respectively. The method exhibited good linearity, reproducibility and sensitivity, selectivity and robustness when used for the analysis of clinical samples.

Calibration↗
PubMedDate not supplied

Determination of pesticides in composite dietary samples by gas chromatography/mass spectrometry in the selected ion monitoring mode by using a temperature-programmable large volume injector with preseparation column.

Use of a temperature-programmable preseparation column in the gas chromatographic (GC) injection port permits determination of a wide range of semi-volatile pesticides including organochlorines, organophosphates, triazines, and anilines in fatty composite dietary samples while reducing sample preparation time and solvent consumption. Dietary samples are mixed with diatomaceous earth and are Soxhlet-extracted with an azeotropic solution of hexane and acetone. Sample preparation uses liquid-liquid partitioning over diatomaceous earth followed by normal phase chromatography over partially deactivated alumina. The final cleanup step occurs in a preseparation column in the GC injector, which is able to perform splitless transfer of the analytes to the analytical column and purge 99% of the high molecular weight residue. Detection is performed by GC/mass spectrometry (MS) in the selected ion monitoring mode. Method detection limits were at or below 2 ng/g for 24 of 35 pesticides studied, with recovery between 70 and 125% for 27 pesticides in samples fortified at 10 ng/g. Recovery was not dependent on fat content when measured in laboratory fortified samples containing 1, 5, and 10% fat by weight. Precision over multiple injections was acceptable, with a relative standard deviation of 2.6-15% for 25 analytes.

Aluminum Oxide↗
PubMed1988

Determination of manganese in biological materials by electrothermal atomic absorption spectrometry: a review.

The great diversity of methods for measuring manganese in biological materials (serum, plasma, whole blood, urine, spinal fluid, and hair) reflects the difficulty in measuring extremely small quantities of this element. Detailed examination of these methods demonstrates that the one most used is flameless atomic absorption spectrometry. In this review we report the different instrument settings for wavelength, slit width, protection gases, graphite furnaces, type of background correction, amounts measured, and thermal programs. We give detailed recommendations by various authors for collecting samples. A thorough description of the preliminary steps and the handling of the specimen samples is also included: direct determination with or without dilution, addition of a matrix modifier or determination after ashing, with or without chelation-extraction steps. The preparation of the standards, procedures used, analytical criteria (accuracy, precision, specificity, detection limit, linearity), problems (interferences, matrix effects), and reference values and their physiological variations are also described. We give a consensus of recommendations concerning the choice of a method.

Female↗
PubMed2005

Determination of cocaine and benzoylecgonine by direct injection of human urine into a column-switching liquid chromatography system with diode-array detection.

A method for the determination of cocaine (COC) and benzoylecgonine (BZE) in human urine using a column-switching liquid chromatography system is reported. A homemade precolumn (20 mm x 4.6 mm i.d.) dry-packed with Alltech ODS-C18 (35-750 microm) was employed as an extraction precolumn in order to extract and concentrate the COC and BZE from the human urine sample. The analytes were continuously transferred to the analytical column (Spherisorb-C8, 250 mm x 4.6 mm i.d.; dp = 5 microm) by means of the switching arrangement in the backflush mode. Detection was carried out at 235 nm in a UV-diode array detector. The validation of the method revealed analytes quantitative recoveries (96-102%) at three concentrations in the range from 0.25 to 4.00 and from 0.5 to 12.0 microg/mL for COC and BZE, respectively. These values demonstrate the excellent extraction efficiency of the precolumn. The detection limits for COC and BZE at a signal-to-noise ratio of 3 were 0.08 and 0.15 microg/mL when a sample volume of 50 microL was injected. The overlap of sample preparation, analysis and recondition of the precolumn increases the sample throughput to four samples per hour. The proposed method has been applied to the determination of COC and BZE in human urine samples from 73 suspecting drug addicts. Urine concentrations of 1.0-118.10 microg of BZE/mL and 0.1-41.0 microg of COC/mL were found.

Chromatography, Liquid↗
PubMed2001

Associations between coping and survival time of adult leukemia patients receiving allogeneic bone marrow transplantation: results of a prospective study.

BACKGROUND: To investigate associations between coping strategies and length of survival in a sample of 52 adult leukemia patients receiving allogeneic bone marrow transplantation (BMT). METHODS: 52 adult patients, diagnosed with acute (AML) and chronic myeloid leukemia (CML) admitted for allogeneic BMT to a university hospital BMT unit in preparation for a transplantation of genotypically matched HLA donor marrow, were interviewed immediately after informed consent and prior to preparatory treatment for transplantation. Semistructured interviews were conducted and recorded for analysis to assess coping styles and were evaluated by a new content analytic coping measure [Ulm Coping Manual (UCM)]. Patients were a random sample of all eligible patients on the BMT unit between May 1990 and May 1994. RESULTS: Complete audiotaped interviews were rated by blind raters, employing a newly developed content analysis for the identification of patients' coping strategies. Multivariate analysis using a Cox model revealed three pretransplant variables that demonstrated a statistically significant influence on 5-year survival: Stage of Disease at transplant (P < .012), Distraction (P < .007), and Fighting Spirit as coping modalities (P < .013). CONCLUSIONS: The results of this prospective study document the impact of certain psychological variables, notably coping style on survival with BMT. This suggests the necessity of utilizing psychosocial interventions to address stress and anxiety in patients awaiting transplantation in order to reduce anxieties and to employ more effective coping techniques to deal more appropriately with their situation and to enhance Fighting Spirit. The effects on survival of such psychosocial interventions need to be tested in a randomized controlled study.

Acute Disease↗
PubMed2026

Mitigating pH-induced instability in deruxtecan-based ADCs: an onboard-mixing icIEF approach for robust charge heterogeneity characterization.

Accurate charge variant analysis of antibody-drug conjugates (ADCs) is essential for understanding product heterogeneity and ensuring quality control. However, Deruxtecan (DXd)-based ADCs present a unique analytical challenge due to the intrinsic instability of the payload, where the lactone ring readily undergoes hydrolysis under alkaline conditions, resulting in time-dependent shifts in charge distribution during imaged capillary isoelectric focusing (icIEF). In this study, we describe the development of an onboard-mixing icIEF method designed to minimize pH-induced degradation during sample preparation. By separating ADC samples from carrier ampholytes (CAs) prior to injection and enabling real-time mixing within the instrument, this approach effectively suppresses premature lactone ring opening and stabilizes charge variant profiles. Comparative studies between conventional premixing and onboard-mixing approach demonstrated that the latter significantly enhances reproducibility, particularly for acidic variants that are highly sensitive to structural conversion. Comprehensive method validation confirmed excellent precision, linearity, and sensitivity, with consistent performance across run-to-run and intra-day analyses. The results underscore the importance of controlling microenvironmental pH exposure in the analysis of chemically instable ADCs. The proposed onboard-mixing strategy provides a robust and efficient solution for icIEF-based characterization, reducing analytical artifacts while simplifying method development. This approach is broadly applicable to ADCs and other biotherapeutics containing pH-sensitive functional groups.

Hydrogen-Ion Concentration↗
PubMed1985

Measurement of vitamin E in serum and plasma by high performance liquid chromatography with electrochemical detection.

A deficiency of vitamin E has been associated with a wide variety of pathological conditions, many of them involving neonates. Previously published methods for the quantitation of vitamin E require large sample volumes as well as extensive extraction and concentration procedures. The present work describes a method for the quantitation of vitamin E in small volumes (less than or equal to 50 microliters) of serum or plasma without the need for extraction or concentration of the sample. With further optimization, even smaller volumes (less than or equal to 10 microliters) can be employed. Sample preparation consisted of precipitation of plasma proteins with absolute ethanol. After centrifugation, a small volume (10 to 50 microliters) of the supernatant was injected directly onto the high performance liquid chromatography (HPLC) column. A dual channel electrochemical detector was used for quantitation of the vitamin E. Pooled serum or plasma was used to determine within-day (8.43 +/- 0.19 mg/L) and between-day (8.49 +/- 0.34 mg/L) precision. Analytical recovery of added vitamin E (4-16 mg/L) averaged 102 +/- 7.0%. No interfering peaks were observed. Linearity was demonstrated over 0.5 to 800 ng. Vitamin E acetate is not detected by this method. HPLC with electrochemical detection is a highly sensitive and specific method for the quantitation of vitamin E in plasma or serum. This procedure is rapid and simple, and can be performed with very small sample volumes.

Chromatography, High Pressure Liquid↗
PubMed1989

Specific routine determination of 3'-azido-3'-deoxythymidine (AZT) in plasma by partly automated liquid chromatography.

A simple isocratic HPLC method for determining azidothymidine (AZT) in serum and plasma of patients has been developed. The novel, specific, two-step, solid-phase extraction approach used for sample preparation gives a nearly quantitative recovery (95.3%) of AZT from the blood plasma matrix and requires only minimal handling of infectious clinical samples. Automatic "on-line" injection is achieved with an AASP system by switching a small cartridge, which retains the extracted analyte, into the HPLC stream. The overall HPLC procedure shows satisfying reproducibility with low standard deviation (CV: 2.1%). Because of the low detection limit (about 10 ng) and the possibility of concentrating AZT quantitatively in as much as 5 mL of plasma or serum, the method can be used in routine monitoring of AZT as well as in pharmacokinetic studies. Nevertheless, before establishing therapeutic drug monitoring for AZT, it still must be determined at what time after the last AZT dose blood specimens should be drawn for correct therapeutic interpretation of the concentration of AZT measured in blood.

Acquired Immunodeficiency Syndrome↗
PubMed2006

Sequential analysis of multiple analytes using a surface plasmon resonance (SPR) biosensor.

A sequential analysis method for the analysis of two analytes was developed using a surface plasmon resonance (SPR) biosensor. A sample with both analytes was introduced into the single sensing region and then each analyte was analyzed sequentially. Two detection models were devised for the samples with the following composition: (1) one target analyte resulting in a sensor response without any label and the other analyte with only additional label, (2) both target analytes requiring additional labels for detection. A standard curve for each model was prepared and applied for sequential analysis of anti-bovine serum albumin (anti-BSA) antibodies and horseradish peroxidase (HRP). The errors of the sequential analysis of Models 1 and 2 were found to be less than 6%, and this method was therefore acceptable for application. No cross-reaction arising from non-specific binding among the participating antigens and antibodies was shown to occur in Models 1 and 2. For optimization of the analyte binding capacity of immunoaffinity (IA), the concentration ratio of the molecular recognition element at the immobilization step was adjusted. Subsequently, from the measurement of the maximum sensor response (R(max)), optimization of the analyte binding capacity could be made. Using Model 2, the feasibility of sequential analysis was demonstrated by detecting levels of human chorionic gonadotropin (hCG) and human albumin (hA) in healthy human urine, since both proteins are known to be related to abortion and preterm delivery during early pregnancy.

Albumins↗
PubMed2000

Quantification of etheno-DNA adducts using liquid chromatography, on-line sample processing, and electrospray tandem mass spectrometry.

Etheno-DNA adducts are promutagenic lesions present in normal animal and human tissues that are believed to be important in the etiology of cancer related to diet and lifestyle. A method has been developed for the quantification of trace levels of etheno-DNA adducts using on-line sample preparation coupled with liquid chromatography and electrospray tandem mass spectrometry. The use of automated solid-phase extraction and stable labeled internal standards permitted the robust determination of ethenodeoxyadenosine contained in crude DNA hydrolysates from untreated rodent and human tissues at levels on the order of one adduct in 10(8) normal nucleotides from 100 microg of DNA. Inherent analyte response and matrix interference made sensitivity for simultaneous determination of ethenodeoxycytidine approximately 5-fold lower. The method was applied to the analysis of liver DNA from untreated and urethane-treated B6C3F1 mice, untreated rat liver, human placenta, and several commercial DNA preparations. Some sources of potential artifactual formation of etheno-DNA adducts were investigated.

Animals↗
PubMed1979

Isotachophoresis of CSF proteins in gel tubes especially gammaglobulins. An analytical and preparative technique for high-separation of CSF proteins.

An isotachophoretic method using polyacrylamide gel (PAG-ITP) in a simple disc electrophoretic equipment with plastic tubes containing the gels, was elaborated and especially designed for studying the gammaglobulins in CSF and serum from control subjects and patients with neurological disorders, especially known or probable MS. The device and the ITP system used, including leading and terminating electrolytes and spacer substances, dividing the gammaglobulins in a reproducible way, are described. No cooling of the gel tubes was needed. The sample volumes varied between 5--500 microliters, and the separation time was 1.5--3.0 h. CSF from patients with verified or probable MS revealed characteristic, increased low-mobility gammaglobulin fractions. Using other ITP systems, such as other spacer compositions, the anodic proteins can also be studied in more detail. PAG-ITP in gel tubes is a simple and inexpensive technique which can be used for both analytical and preparative procedures for biological material such as CSF, serum and extractions from nervous tissues.

Cerebrospinal Fluid Proteins↗
PubMed1996

Simultaneous determination of coumarin, 7-hydroxycoumarin and 7-hydroxycoumarin glucuronide in human serum and plasma by high-performance liquid chromatography.

A HPLC method was developed for the determination of the metabolites of coumarin and 7-hydroxycoumarin in plasma and serum. Separation was based on gradient elution of 7-hydroxycoumarin glucuronide, 7-hydroxycoumarin, coumarin and finally 4-hydroxycoumarin (which is used as an internal standard). Standards, prepared in plasma or serum, and samples were treated with trichloroacetic acid, mixed and centrifuged. The supernatant was removed and analyzed by reversed-phase high-performance liquid chromatography on a C18 column. The limit of detection was 50 ng/ml for 7-hydroxycoumarin and 200 ng/ml for coumarin and 7-hydroxycoumarin glucuronide. The linear range was 0.5-100 micrograms/ml for each of the analytes. The percentage relative standard deviation about the mean measured concentrations were all below 10%. There was no statistical difference between the standard curves prepared in plasma or serum. The method developed was applied to the determination of each of the three compounds in serum, after the administration of 7-hydroxycoumarin, and in plasma after the administration of coumarin. The concentrations of total 7-hydroxycoumarin in the serum samples were also determined by another HPLC method and the results were compared. There was no statistical difference between the results determined.

Chromatography, High Pressure Liquid↗
PubMed1997

An isotope-dilution gas chromatography-mass spectrometry method for trace analysis of xylene metabolites in tissues.

A gas chromatography-mass spectrometry (GC-MS) method using isotope dilution was developed to measure trace levels of xylene metabolites in brain tissues. The primary metabolites of xylene are dimethylphenol (DMP), methylbenzyl alcohol (MBA), toluic acid (TA), and methylhippuric acid (MHA). The internal standard was a mixture of deuterated DMP-d3, TA-d7, and MHA-d7. DMP-d3 was commercially available and was used as the internal standard for both DMP and MBA. TA-d7 and MHA-d7 were biosynthesized by administering xylene-d10 to rats and collecting their urine. Based on the noise peaks in 10 blank samples, the on-column limits of quantitation (mean +10 SD of noise peaks) were approximately 305, 1220, 545, and 386 pg for DMP, MBA, TA, and MHA, respectively. Analyte detection and recovery tests from brain tissues of control rats were conducted by spiking the tissues with 32 nmol/g of each analyte, together with the deuterated metabolites. The tissues were homogenized, extracted with ethyl acetate, and derivatized by trimethylsilylation. One microliter of the sample was injected into the GC-MS. The recoveries of the analytes were 104 +/- 8%, 80 +/- 9%, 93 +/- 10%, and 92 +/- 11% (mean +/- SD, n = 7) for DMP, MBA, TA, and MHA, respectively. The tissue preparation efficiency, which was indicated by absolute recoveries of internal standards, was approximately 33% for DMP, MBA, and TA and approximately 80% for MHA. No metabolites were detected in untreated control tissues. This simple and sensitive method to simultaneously detect major xylene metabolites in brain tissues could also be used for the analysis of blood and urine samples from workers to monitor p-xylene exposure.

Animals↗
PubMed2005

Separation of proteins with a molecular mass difference of 2 kDa utilizing preparative double-inverted gradient polyacrylamide gel electrophoresis under nonreducing conditions: application to the isolation of 24 kDa human growth hormone.

A method for separating proteins with a molecular mass difference of 2 kDa using SDS-PAGE under nonreducing conditions is presented. A sample mixture containing several human growth hormone (hGH) isoforms was initially separated on a weak anion-exchange column. Fractions rich in 24 kDa hGH as determined by analytical SDS-PAGE were pooled and further separated by cation-exchange chromatography. The fractions pooled from the cation-exchange chromatography contained two hGH isoforms with a 2 kDa molecular mass difference according to SDS-PAGE analysis, 22 and 24 kDa hGH. The 22 and 24 kDa hGH were separated using continuous-elution preparative double-inverted gradient PAGE (PDG-PAGE) under nonreducing conditions. The preparative electrophoresis gel was composed of three stacked tubular polyacrylamide matrices, a 4% stacking gel, a 13-18% linear gradient gel, and a 15-10% linear inverted gradient gel. Fractions containing purified 24 kDa hGH were pooled and Western blot analysis displayed immunoreactivity to antihGH antibodies. PDG-PAGE provides researchers with an electrophoretic technique to preparatively purify proteins under nonreducing conditions with molecular mass differences of 2 kDa.

Chromatography↗