Search results for "liquid chromatography"
showing 10 items of 942 documents
Comparison of green sample preparation techniques in the analysis of pyrethrins and pyrethroids in baby food by liquid chromatography–tandem mass spe…
2017
A new selective and sensitive liquid chromatography triple quadrupole mass spectrometry method was developed for simultaneous analysis of natural pyrethrins and synthetic pyrethroids residues in baby food. In this study, two sample preparation methods based on ultrasound-assisted dispersive liquid–liquid microextraction (UA-DLLME) and salting-out assisted liquid–liquid extraction (SALLE) were optimized, and then, compared regarding the performance criteria. Appropriate linearity in solvent and matrix-based calibrations, and suitable recoveries (75–120%) and precision (RSD values ≤ 16%) were achieved for selected analytes by any of the sample preparation procedures. Both methods provided the…
Solid-phase microextraction-liquid chromatography-mass spectrometry applied to the analysis of insecticides in honey
2007
An approach based on solid-phase microextraction-liquid chromatography-mass spectrometry (SPME-LC-MS) has been developed for determining 12 insecticides (bromophos ethyl, chlorpyrifos methyl, chlorpyrifos ethyl, diazinon, fenoxycarb, fonofos, phenthoate, phosalone, pirimiphos methyl, profenofos, pyrazophos, and temephos) in honey. The influence of several parameters on the efficiency of the SPME was systematically investigated. Under optimal conditions, the procedure provided excellent linearity (>0.990), detection and quantification limits (between 0.001 and 0.1 microg g(-1) and between 0.005 and 0.5 microg g(-1), respectively), and precision (<19% at the quantification limits and from 6 t…
Determination and separation of diarylheptanoids from alder growing in Latvia
2015
The composition of diarylhepatnoids fraction isolated from bark of two alder species (grey alder and black alder) was studied. The efficiency of three extraction methods used for isolation of diarylhepatnoids from alder bark was compared. Two diarylhepatnoids: 1,7-bis-(3,4-dihydroxyphenyl)-heptan- 3-one-5-O-β-D-xylopyronoside (oregonin) and 1,7-bis-(3,4-dihydroxyphenyl)-3-hydroxyheptane-5-O-β-D- xylopyranoside were isolated from the bark of grey alder. The phenolic components of the extracts were analyzed by high-performance liquid chromatography (HPLC). Quantitative determination of oregonin was performed using an internal standard method. The results obtained show that alder barks are ric…
Mass spectrometry applications
2012
The history of proteomics dates back to the discovery of two-dimensional gels in the 1970s, which provided the first feasible way of displaying hundreds or thousands of proteins on a single gel. Despite mass spectrometry being restricted for a long time to small and thermostable compounds, the development in the late 1980s of two techniques for the routine and general formation of molecular ions of intact biomolecules changed this situation and mass spectrometry has become an indispensable tool for proteomics research. The aim of this chapter is to review the major types of MS instruments used in proteomics analysis and to discuss strategies for the analysis of whole proteins and peptides o…
Effect of ionization and the nature of the mobile phase in quantitative structure-retention relationship studies.
2005
Abstract The octanol–water distribution constant, commonly called partition coefficient, Po/w, is a parameter often retained as a measure of the hydrophobicity of a molecule. log Po/w, for a given molecule, can be conveniently evaluated constructing correlation lines between standard retention factor logarithms (log k) in reversed-phase liquid chromatography (RPLC) and standard log Po/w values. Many compounds of pharmaceutical interest can be quite hydrophobic and have, simultaneously, basic nitrogen atoms or acidic sulfur containing groups in their structure. This renders them ionizable. The hydrophobicity of the molecular drug form (Po/w value) is completely different from its ionic form …
Effect of sodium dodecyl sulphate and Brij-35 on the analysis of sulphonamides in physiological samples using direct injection and acetonitrile gradi…
2016
Micellar liquid chromatography (MLC) is a reversed-phase (RP) mode, which often does not require gradient elution, since the peaks of mixtures of compounds within a large range of polarities appear more evenly distributed in the chromatograms of isocratic elution, giving rise to a “gradient effect”. However, the use of a gradient of organic solvent may still be convenient to shorten the total analysis time. This work compares the separation of 15 sulphonamides using conventional hydro-organic RPLC and MLC with the surfactants sodium dodecyl sulphate (SDS) and Brij-35, and both isocratic and gradient elution with acetonitrile. The observed behaviour is rationalized attending to the interacti…
Quality control of pharmaceuticals containing non-steroidal anti-inflammatory drugs by micellar liquid chromatography
2002
A liquid chromatographic procedure is described for the determination of acemetacin, diclofenac, indomethacin, ketoprofen, nabumetone, naproxen, piketoprofen, and tolmentin in pharmaceutical preparations. The compounds were separated on a Kromasil C18 analytical column, with a guard column of similar characteristics; the mobile phase was 0.06 M cetyltrimethylammonium bromide, at pH 7, containing 10% 1-butanol. At a flow rate of 1 mL min−1 the elution time of the most retained compound was 23 min. Limits of detection were between 0.01 μ g mL−1 for diclofenac and 0.2 μ g mL−1 for naproxen. The proposed method enables the determination of non-steroidal anti-inflammatory drugs in pharmaceutical…
Comparison between sodium dodecylsulphate and cetyltrimethylammonium bromide as mobile phases in the micellar liquid chromatography determination of …
2004
The retention behaviour of non-steroidal anti-inflammatory drugs (NSAIDs) using micellar mobile phases of sodium dodecylsulphate (SDS) is studied and compared with that observed with micellar mobile phases of cetyltrimethylammonium bromide (CTAB). A liquid chromatographic procedure for the determination of acemetacin, diclofenac, indomethacin, ketoprofen, naproxen and tolmetin in pharmaceutical preparations is described. The proposed system uses a Kromasil C18 analytical column and a solution of 0.15 M SDS at pH 3 with 10% 1-propanol as mobile phase. Under these conditions, the studied NSAIDs elute between 6 and 10 min at a 1 mL min(-1) flow rate. Limits of detection (LOD) are lower than 0.…
On the Retention of Diuretics in Micellar Liquid Chromatography and Their Site of Action Within the Nephron
1993
Abstract The therapeutical action of diuretics has been attributed to their hydrophobic character, among other properties. Therapeutical and physiological classifications of diuretics are correlated. The site of action of high efficacay diuretics is the loop of Henle, that of intermediate efficacy diuretics is the distal tubule and that of low efficacy diuretics is the proximal and distal tubules, and the collecting duct. Partition coefficients between water and micelles offer a scale for hydrophobicity, which leads to a further correlation between retention in Micellar Liquid Chromatography (MLC), with a sodium dodecyl sulphate mobile phase and an ODS-C18 column, and the sites of action wi…
Quantitative determination of octylphenol, nonylphenol, alkylphenol ethoxylates and alcohol ethoxylates by pressurized liquid extraction and liquid c…
2007
6 páginas, 1 figura, 2 tablas.