Search results for "liquid chromatography"
showing 10 items of 942 documents
Biomonitoring of glyphosate and AMPA in the urine of Spanish lactating mothers
2021
The objectives of this study were to evaluate the urinary levels of Glyphosate (Gly) and its metabolite aminomethylphosphonic acid (AMPA) in Spanish breastfeeding mothers (n = 97), to identify the main predictors of exposure and to perform a risk assessment. Urine samples were analyzed using a method based on solid phase extraction and liquid chromatography tandem mass spectrometry (LC-MS/MS) determination. The developed method showed limits of quantification of 0.1 μg/L for both analytes. The detection frequencies (DFs) were 54% for Gly and 60% for AMPA, with geometric means (GMs) of 0.12 μg/L and 0.14 μg/L, respectively. In the statistical analysis, no relationship was found between the u…
Stability of nitroaromatic specialty explosives in reversed-phase liquid chromatographic systems
2008
Abstract In this study, the stability of 2,4-dinitroanisole, 2,2′,4,4′,6,6′-hexanitrodiphenylsulfide, 2,3,4,6-tetranitroaniline, 2,4,6-trinitroaniline, 2,4,6-trinitroanisole, and 2,4,6-trinitrochlorobenzene in liquid chromatographic systems was studied under different solvent/eluent conditions. Stock solutions of the explosives were prepared in acetonitrile and diluted with acetone/water, acetonitrile/water, or methanol/water mixtures. Within 48 h, these working solutions were repeatedly injected onto a silica column and eluted with acetonitrile/water or methanol/water mobile phases. Under all conditions, 2,4-dinitroanisole was stable, whereas 2,4,6-trinitroaniline was stable only in the me…
Determination of mono-, di- and trinitronaphthalenes in soil samples contaminated by explosives.
2004
We investigated the extraction of eight mono-, di- and trinitronaphthalenes from soil samples by ultrasonic, respectively, soxhlet extraction. Sonication was the more convenient procedure with a usually higher repeatability than the soxhlet method. All extracts were analysed by high-performance liquid chromatography with diode array detection. These methods were used to determine the concentration of nitronaphthalenes in five soil samples polluted by explosives. The most abundant contaminants were 1,5- and 1,8-dinitronaphthalene as well as 1,3,5-, 1,3,8- and 1,4,5-trinitronaphthalene. In all samples the sum of trinitronaphthalenes exceeded the sum of mono- and dinitronaphthalenes. It is rec…
Oxidation of diclofenac in the presence of iron(II) octacarboxyphthalocyanine
2021
Abstract This paper presents the results of the research on the influence of catalytic activity of iron(II) octacarboxyphthalocyanines (FePcOC) on the transformation of diclofenac (DCF) which is the most popular anti-inflammatory analgesic. Diclofenac poses a serious threat to the natural environment. The paper demonstrates that diclofenac, in the presence a monomeric form of iron octacarboxyphthalocyanine and hydroxyl radicals (HO•) (from H2O2), undergoes a transformation into diclofenac-2,5-iminoquinone (DCF-2,5-IQ), causing distinct changes in the UV–Vis absorption spectrum. In the presence of iron octacarboxyphthalocyanine and H2O2, the previously colourless diclofenac solution becomes …
Measurement of pollution levels of N-nitroso compounds of health concern in water using ultra-performance liquid chromatography–tandem mass spectrome…
2017
International audience; This paper reports the development of a highly sensitive analytical method combining solid-phase extraction (SPE) with ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UHPLC–MS/MS), for the monitoring of ultra-trace levels of N-nitrosamines in water samples. Under optimized analytical conditions, chromatographic separation was performed in 3 min, in isocratic mode, using an Acquity UHPLC C18 column and a mobile phase consisting of acetonitrile, water, and formic acid (60:40:0.1, v/v/v) at a flow rate of 0.4 mL min−1. Electrospray ionization tandem interface was employed prior to mass spectrometric detection. Good linearity (R2 ≥ 0.9…
Monitoring WWTP performance using size-exclusion chromatography with simultaneous UV and fluorescence detection to track recalcitrant wastewater frac…
2018
Abstract A trial monitoring of a typical full-scale municipal WWTP in Central Finland was aimed to explore applicability of high performance liquid chromatography – size exclusion chromatography (HPSEC) with simultaneous UV and fluorescence detection as a tool for advanced routine monitoring of wastewater treatment. High, intermediate, and low molecular weight (MW) fractions of untreated wastewater (influent) and treated wastewater (secondary effluent) were characterized in terms of UV absorbance at 254 nm (UVA254) and specific fluorescence representing tyrosine-like, tryptophan-like, and humic/fulvic-like compounds. The activated sludge treatment removed 97 ± 1% of BOD, 93 ± 2% of COD, 71 …
Photo-induced fluorescence of magnesium derivatives of tetracycline antibiotics in wastewater samples
2009
Abstract An analytical strategy, for the determination of tetracyclines (TCs), based on a HPLC system coupled with a photo-reactor followed by post-column derivatization was developed. Higher fluorescence emission after coupling the resulting photo-fragments with magnesium ions was observed for the determination of minocycline (MC), epitetracycline (ETC), tetracycline (TC) and doxycycline (DC). The manifold included a HPLC system with a photo-reactor (PTFE tubing helically coiled around a low-pressure mercury lamp), a mixing T-piece and a fluorescence detector. The derivatization reagent was delivered at 0.5 mL min −1 by a pump. After HPLC separation using a gradient system with a mobile ph…
OVERVIEW OF ANALYTICAL PROCEDURES FOR FATTY AND RESIN ACIDS IN THE PAPERMAKING PROCESS
2012
This review describes the role of wood extractives, especially fatty and resin acids, in papermaking, as well as the importance of their removal from process waters. One of the main aims is also to illustrate versatile analysis methods for this purpose and highlight recent developments in corresponding applications. Most of the current methods require time-consuming and laborious sample pretreatment procedures prior to gas chromatography coupled either with flame ionization or mass selective detection. However, some faster, even online techniques with minimum sample pretreatment, are also available, mainly including high performance liquid chromatography coupled with mass spectrometry. The …
Analysis of Trace Pharmaceuticals and Related Compounds in Municipal Wastewaters by Preconcentration, Chromatography, Derivatization, and Separation …
2014
A significant portion of pharmaceuticals and other organic chemicals consumed by people and animals are released into municipal wastewater treatment plants. Most of them are degraded during the wastewater treatment processes, but some of them degrade only partially and may be widely transported and dispersed into the aquatic environment. This is why efficient and fast analytical methods are needed for detection of organic compounds in wastewaters at trace levels. Because wastewaters often consist of complex matrices and high-molecular mass materials, e.g., lignocellulosic biomass, which may bring challenges to the sample preparation procedures, efficient pre-concentration methods such as so…
Analysis of enantiomers giving partially overlapped peaks by using different treatments of the chromatographic ultraviolet signals: quantification of…
2001
Abstract Different strategies for the quantification of partially coeluting optical isomers have been investigated. The methods tested are based on the use of different features as the analytical UV signals: peak heights, perpendicular drop areas, first and second derivatives of the chromatograms, peak areas obtained by deconvolution of the overlapped peaks with data fitting optimization, and a multivariate model (principal component regression, PCR). The amphetamine-derivative drug pseudoephedrine was selected as a model compound. For chromatography, LiChrospher 100 RP 18 and a mobile-phase consisting of methanol and a solution of carboxymethyl-β-cyclodextrin (the chiral selector) were use…