Search results for "Derivatization"

Determination of ketosteroid hormones in meat by liquid chromatography tandem mass spectrometry and derivatization chemistry.

2015

A method for the determination and quantification of ketosteroid hormones in meat by mass spectrometry, based on the derivatization of the carbonyl moiety of steroids by O-methylhydroxylamine, is presented. The quantitative assay is performed by means of multiple-reaction-monitoring (MRM) scan mode and using the corresponding labelled species, obtained by reaction with d 3-methoxylamine, as internal standard. The accuracy of the method was established by evaluating artificially spiked samples, obtaining values in the range 90-110%. Recovery tests were performed on blank matrix samples spiked with non-natural steroids including trenbolone and melengestrol acetate. The latter experiment revea…

Derivatization of amphetamine and methamphetamine with 1,2-naphthoquinone 4-sulfonic acid into solid-phase extraction cartridges. Determination of am…

1997

The derivatization of amphetamine and methamphetamine with 1,2-naphthoquinone-4-sulfonate (NQS) into solid-phase extraction cartridges (C 18 ) is described. Optimum conditions were the use of carbonate–hydrogencarbonate buffer of pH 10, a 10 min reaction time at 25 °C and an NQS concentration of 9.6 × 10 - 3 M. The accuracy and the precision of the method were tested. The results obtained with the proposed liquid–solid procedure were compared with those obtained with a traditional liquid–liquid extraction with hexane–ethyl acetate. The procedure was used to measure amphetamine in pharmaceutical and urine samples

Influence of sample preparation on analytical results: drug analysis [GC/MS] on hair snippets versus hair powder using various extraction methods

1997

The comparison of aqueous extraction methods and hair extraction by organic solvents performed on hair powder as well as on hair snippets of the same sample revealed different qualities of the procedures. Qualitative and quantitative results by the same derivatization step and GC/MS detection demonstrated, that the risk of missing a drug substance is higher using hair snippets than after drug extraction on pulverised hair. Drug recovery for opiates, cocaine and benzoylecgonine from hair was found to be best in aqueous solvents or in methanol extracts. The results are discussed under the aspects of solid-phase extraction, the hair sample representing an inhomogenous material. The localisatio…

Development of a polydimethylsiloxane–thymol/nitroprusside composite based sensor involving thymol derivatization for ammonium monitoring in water sa…

2014

This report describes a polydimethylsiloxane (PDMS)-thymol/nitroprusside delivery composite sensor for direct monitoring of ammonium in environmental water samples. The sensor is based on a PDMS support that contains the Berthelot's reaction reagents. To prepare the PDMS-thymol/nitroprusside composite discs, thymol and nitroprusside have been encapsulated in the PDMS matrix, forming a reagent release support which significantly simplifies the analytical measurements, since it avoids the need to prepare derivatizing reagents and sample handling is reduced to the sampling step. When, the PDMS-thymol/nitroprusside composite was introduced in water samples spontaneous release of the chromophore…

Footprint of carbonyl compounds in hand scent by in-tube solid-phase microextraction coupled to nano-liquid chromatography/diode array detection

2019

Abstract In the present work, the footprint of carbonyl compounds in hand scent was achieved by a miniaturized method consisting of sampling with cotton gauze, extraction and derivatization using 2,4-dinitrophenylhydrazine (DNPH) and preconcentration, separation and detection by in-tube solid-phase microextraction (IT-SPME) coupled to nano-liquid chromatography/Uv–vis diode array detection. The coupling IT-SPME-nanoLC-DAD was solved by using a two-valve system: the first valve for loading the sample and the second one to perform IT-SPME. To this aim, a nanoparticle-based capillary column was employed. Firstly, the transfer time from the load loop to the NP-based capillary column in the IT-S…

Occurrence and daily intake of ochratoxin A of organic and non-organic rice and rice products

2005

Abstract Ochratoxin A (OTA) was extracted from 84 rice samples and rice products by using accelerated solvent extraction (ASE) and analysed with liquid chromatography coupled with fluorescence detection. Samples were collected from rice cultivars, local markets and supermarkets; 64 were of non-organic and 20 of organic production. 7.8% of non-organic samples had OTA levels from 4.3 to 27.3 μg/kg and in 30% of organic samples was detected the presence of this mycotoxin varying from 1.0 to 7.1 μg/kg. OTA presence was confirmed by methyl-ester derivatization. Rice and rice products labelled with denomination of origin (DO) were not detected OTA due to the fact that its production has implement…

Levels of ochratoxin A in wheat and maize bread from the central zone of Portugal.

2007

Ochratoxigenic fungi are natural contaminants of cereal and the produced toxins are harmful to humans and animals. Ochratoxin A (OTA) is among the most important mycotoxins, and the International Agency for Research on Cancer (IARC) classifies it as possibly carcinogenic to humans (group 2B). A total of 61 samples of bread from the central zone of Portugal were analysed for OTA by liquid chromatography (LC) with fluorescence detection (FD). For confirmation two procedures were applied, methyl ester derivatization with boron trifluoride-methanol and liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI/MS/MS). As far as we know, this is the first report where on-line…

Comparison of Different Analytical Methods for Determination of Type B Trichothecenes in Wheat and Ochratoxin A in Beer

2008

Building a Functionalizable, Potent Chemiluminescent Agent: A Rational Design Study on 6,8-Substituted Luminol Derivatives.

2021

Luminol is a prominent chemiluminescent (CL) agent, finding applications across numerous fields, including forensics, immunoassays, and imaging. Different substitution patterns on the aromatic ring can enhance or decrease its CL efficiency. We herein report a systematic study on the synthesis and photophysics of all possible 6,8-disubstituted luminol derivatives bearing H, Ph, and/or Me substituents. Their CL responses are monitored at three pH values (8, 10, and 12), thus revealing the architecture with the optimum CL efficiency. The most efficient pattern is used for the synthesis of a strongly CL luminol derivative, bearing a functional group for further, straightforward derivatization. …

Determination of fatty alcohol ethoxylates by derivatisation with maleic anhydride followed by liquid chromatography with UV-vis detection.

2007

The esterification of fatty alcohol ethoxylates (FAEs) by melting with maleic anhydride has been studied in the presence of urea. The reaction rate and yield of non-ethoxylated and ethoxylated alcohols increase largely when grinded urea is suspended in the reaction medium, a 100% yield being achieved at 80 degrees C in 15 min. The procedure is tolerant to the presence of large amounts of water. The UV-vis response factors of the derivatives of individual FAE oligomers vary little with the number of carbon atoms in the alkyl chain, n, and the number of ethylene oxide units, m. Derivatised samples of industrial FAE mixtures, cleaning products and river and sea waters were chromatographed on a…