Search results for "CHROMATOGRAPHY"

Stability of 11-Nor-Δ9-carboxy-tetrahydrocannabinol Glucuronide in Plasma and Urine Assessed by Liquid Chromatography-Tandem Mass Spectrometry

2002

Abstract Background: Unconjugated 11-nor-Δ9-carboxy-tetrahydrocannabinol (THCCOOH) in blood and urine has been proposed as a valuable marker, but the glucuronide (THCCOOglu) is present in considerably higher concentrations than the parent drug. Acyl glucuronides have been shown to be potentially reactive conjugates, which may affect the in vitro metabolite pattern. Methods: Extraction procedures and a liquid chromatography-tandem mass spectrometry assay were developed and validated to investigate the stability of THCCOOglu in urine and plasma. Plasma and urine samples with added THCCOOglu were stored at −20, 4, 20, and 40 °C up to 10 days. Results: The glucuronide was stable at −20 °C in bo…

Rapid determination of ibotenic acid and muscimol in human urine

2014

Reply to: On the importance of the use of proper approaches for comparison of analytical methods for serum nitrate and evaluation of reference concen…

2009

Micro-determination of DNA in biological materials by gas-chromatographic and isotope dilution analysis of thymine content

1970

Large-Scale Synthesis of Mammalian Gonadoliberin without protection of side-chain functions

1991

A simple, Large-scale preparation of mammalian gonadoliberin was elaborated using classical solution methods without protecting side-chain functions. At the final stage, a hexapeptide segment was condensed with the corresponding tetrapeptide and the obtained decapeptide was purified by a single chromatographic procedure on silica gel. The total efficiency of the whole synthesis and the purity of the product amounted to 34% and 98.3%, respectively.

1-Bromopropane and 2-bromopropane - Determination of 1-bromopropane and 2-bromopropane in urine by dynamic headspace GC/MS [Biomonitoring Methods, 20…

2019

Quartz-capillary gas chromatography of chlorinated phenols and catechols

1983

The gas chromatography of all chlorinated phenols and catechols on a non-polar SE-30 quartz-capillary column has been studied. The relative retention times of the individual components are given and the elution order is discussed. All of the chlorophenols and chlorocatechols can be separated under appropriate operating conditions but simultaneous determination of all the compounds studied resulted in overlapping peaks. Theortho-effect in catechols is stronger than that in phenols. A different order of elution for the compounds studied to that of the corresponding acetate esters is found. Generally, longer retention times for the latter are observed.

Extraction Chromatographic Behavior of Rf, Zr, and Hf in HCl Solution with Styrenedivinylbenzene Copolymer Resin Modified by TOPO (trioctylphosphine …

2010

It is of great interest to study chemical properties of the transactinide elements with atomic numbers (Z) ≥ 104. One of the most important subjects is to establish the position of the elements at the extreme end of the periodic table. To this end we perform studies of chemical properties of these transactinides and compare them with those of their lighter homologues and with the ones expected from extrapolations in the periodic table. So far, chromatographic studies of the transactinides have provided experimental proof of placing rutherfordium (Rf, Z = 104) through hassium (Hs, Z = 108) into groups 4 to 8, respectively. 1-10 Quite recently, copernicium (Cn, Z = 112) has been shown to be a…

FIA-Fluorimetric assembly for the determination of noradrenaline hydrochloride by a solid-phase reactor with immobilized hexacyanoferrate(III)

1997

An FIA assembly provided with immobilized hexacyanoferrate(III) is proposed for the fluorimetric determination of noradrenaline hydrochloride. The oxidative reagent is immobilized by means of a strong anion-exchange resin. The FIA manifold is very simple and the calibration graph is linear over the range 0.5–75mgl−1 noradrenaline hydrochloride with an r.s.d of 0.88% (17 replicates) and a sample throughput of 84h−1. Foreign compounds such as NaCl, sucrose, lactose and sodium sulfate caused no significant errors. The procedure is applied to the determination of noradrenaline in a medicinal formulation.

Determination of aminoglycoside and macrolide antibiotics in meat by pressurized liquid extraction and LC-ESI-MS

2010

A simple method for the simultaneous determination of dihydrostreptomycin, spectinomycin, spiramycin, streptomycin, tilmicosin, and tylosin in meat has been developed using pressurized liquid extraction and LC-triple quadrupole MS (LC-ESI-MS/MS). The pressurized liquid extraction operational parameters were optimized and no protein precipitating and fat removing steps were required. A gradient HPLC separation was developed with ion-pair mobile phases consisting of aqueous 1 mM heptafluorobutyric acid water and methanol. Protonated molecules were used as precursor ions for CID. Data acquisition under MS/MS was achieved by applying multiple reaction monitoring of three fragment ion transition…