Search results for "liquid"

Liquid chromatography–mass spectrometry as a tool for wastewater-based epidemiology: Assessing new psychoactive substances and other human biomarkers

2017

Wastewater-based epidemiology (WBE) started to develop significantly in the last 8 years due, in part, to the advance of liquid chromatography–mass spectrometry (LC–MS). Its initial objective ― to estimate the consumption of illicit drugs ― has been expanded to new psychoactive substances (NPS) and other human biomarkers of health, lifestyle and disease. The purpose of this review is to introduce recent methods and outstanding challenges in the application of LC–MS to these new targets, including target, suspect and non-target screening and, outline the workflows developed for discovering metabolites of NPS and biomarkers. Further, we discuss a number of specific methodological challenges t…

Follow up: palmitic acid ester of tetrahydrocannabinol (THC) and palmitic acid diester of 11-hydroxy-THC – unsuccessful search for additional THC met…

2020

Abstract Objectives In a previous investigation we searched for the occurrence of palmitic acid ester compounds of delta9-tetrahydrocannabinol (THC) and its primary metabolite 11-hydroxy-delta9-THC (11-OH-THC) in human body fluids and tissues (THC palmitic acid monoester [THC-Pal] and 11-OH-THC palmitic acid diester [11-OH-THC-DiPal]). As those esters could not be detected in various human body fluids (e.g. blood) or tissues (e.g. adipose tissue) we extended the investigation analyzing adipose tissue samples of mice previously given synthetic THC or a cannabis extract. Methods In total, 48 adipose tissue samples previously tested positive for THC by means of a liquid chromatographic triple …

High-performance liquid chromatographic determination of furfural compounds in infant formulas during full shelf-life

2005

Abstract In order to evaluate the extent of the Maillard reaction in adapted and follow-up infant formulas (IF), a study was made of the evolution of furfural compound (2-furaldehyde, 5-hydroxymethyl-2-furfuraldehyde, 2-furylmethylketone and 5-methyl-2-furaldehyde) in these products, along with their relation to available lysine during the shelf-life period (two years at 20 and 37 °C). Total and free furfural contents were measured by RP-HPLC and UV detection, heating or not the sample in boiling water to free the furfurals bound to proteins and the furfurals formed from precursors. Only 2-furylmethylketone and 5-hydroxymethyl-2-furfuraldehyde were detected. Adapted and follow-up IF showed …

Classification of extra virgin olive oils according to their genetic variety using linear discriminant analysis of sterol profiles established by ult…

2011

Abstract A method to classify extra virgin olive oils (EVOOs) according to their genetic variety using sterol profiles obtained by ultra-performance liquid chromatography (UPLC) with atmospheric pressure chemical ionization mass spectrometry (APCI-MS) detection has been developed. The optimal separation conditions were obtained using a gradient acetonitrile/water (0.01% acetic acid) at a flow rate of 0.8 mL min − 1 and 10 °C. Linear discriminant analysis (LDA) models were constructed with the 11 UPLC-APCI-MS sterol peaks taken from the selective ion recording mode chromatograms. Ratios of the peak areas selected by pairs were used as predictors. With the sequential application of two LDA mo…

Characteristics of Optimization in Individual HPLC Modes: Sections 2.2– 2.5

2008

Simultaneous Determination of Pyridoxine and Riboflavin in Energy Drinks by High-Performance Liquid Chromatography with Fluorescence Detection

2015

Energy drinks, as familiar consumer products, have been widely used in laboratory courses to help promote student interest, as well as to connect lecture concepts with laboratory work. Energy drinks contain B vitamins: pyridoxine (vitamin B6) and riboflavin (vitamin B2) of which amounts are high enough to be of concern. In this work, a fast and inexpensive high-performance liquid chromatography (HPLC) coupled with fluorescence detection method for determining pyridoxine and riboflavin simultaneously in energy drinks is developed. It takes advantage of the native fluorescence of B vitamins and provides high selectivity and sensitivity with low background noise. The method is suitable for und…

Development of a new multi-analyte assay for the simultaneous detection of opioids in serum and other body fluids using liquid chromatography-tandem …

2015

Abstract A liquid chromatography–tandem mass spectrometry method using electrospray ionization in positive ionization mode was developed for the simultaneous detection of multiple opioid-type drugs in plasma. The presented assay allows the quantitative determination of alfentanil, buprenorphine, codeine, desomorphine, dextromethorphan, dextrorphan, dihydrocodeine, dihydromorphine, ethylmorphine, fentanyl, hydrocodone, hydromorphone, methadone, morphine, naloxone, naltrexone, oxycodone, oxymorphone, pentazocine, pethidine, pholcodine, piritramide, remifentanil, sufentanil, and tramadol as well as the metabolites 6-monoacetylmorphine, bisnortilidine, morphine-3-glucuronide, morphine-6-glucuro…

Determination of phenoxy acid herbicides in drinking waters by HPLC and solid phase extraction

1998

Abstract An HPLC procedure for determining phenoxy acid herbicides in waters is described. A LichroSpher RP select B octadecyl-silane analytical column and spectrophotometric detection at 230 nm were used. Adequate retention was achieved with a mobile phase containing MeOH/phosphate buffer 10−2 M pH 2.5/PnOH (50/42/8, v/v). The herbicides were isolated from water samples by using a single solid phase extraction procedure with C18 solid-phase columns. An enrichment factor of 500 is achieved. The coefficients of variation of the method were generally lower than 2.7% at 0.4 μg L−1 herbicide concentration levels. Recoveries ranged between 93 and 118%. The results obtained indicate that the prop…

Identification of acetyl-T-2 toxin, a trichothecene, in moldy rice by HPLC and FDMS

1982

Determination of major human cytochrome P450s activities in 96-well plates using liquid chromatography tandem mass spectrometry.

2007

At the early stage of drug discovery, thousands of new chemical entities (NCEs) may be screened before a single candidate can be identified for development. Evaluation of the effect of NCEs on human CYP450 enzyme activities is a key issue in pharmaceutical development as it may explain inter-subject variability, drug-drug interactions, non-linear pharmacokinetics and toxic effects. A liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method has been developed for the fast and routine analysis of major human CYP450s enzyme activities (CYP1A2, CYP2A6, CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP3A4) in primary hepatocyte cell cultures. The high sensitivity and selectivity of mass …