Search results for "performance liquid chromatography"

Serial versus parallel columns using isocratic elution: a comparison of multi-column approaches in mono-dimensional liquid chromatography.

2015

Abstract When a new separation problem is faced with high-performance liquid chromatography (HPLC), the analysis is addressed conventionally with a single column, trying to find out a single experimental condition aimed to resolve all compounds. However, in practice, the system selectivity may be insufficient to achieve full resolution. When a separation fails, the usual practice consists of introducing drastic changes in the chromatographic system (e.g. use of another column, solvent or pH). An alternative solution is taking benefit of the combined separation capability of two or more columns, which can be attained in multiple ways, such as diverse modalities of two-dimensional HPLC, or mo…

Comparison of voltammetric and high performance liquid chromatographic methods for ascorbic acid determination in infant formulas

1995

Abstract Two methods — voltammetric and high performance liquid Chromatographic (HPLC) — useful for determining ascorbic acid in foods, were compared to ascertain which of them could be used for routine determination of ascorbic acid in infant formulas. Both methods were used to assay 10 identical samples of an adapted cow's milk infant formula and 10 samples of soya protein formula. Precision was determined, the variance of each method was measured, and the methods were compared with each other. The variances of the two methods were not statistically different nor was there any significant difference between the results from the two methods. Therefore, it was concluded that both methods ca…

Biocatalytic transformations of chalcones by cyanobacteria – HPLC–MS study

2016

Polish Yellow Sweet Clover (Melilotus officinalis L.) Honey, Chromatographic Fingerprints, and Chemical Markers

2017

A case study of Polish Melilotus officinalis honey was presented for the first time. Gas chromatography–mass spectrometry (GC-MS) (after steam distillation, Soxhlet extraction, ultrasonic solvent extraction, and solid phase extraction (SPE)) and targeted high performance liquid chromatography with a photodiode array detector (HPLC-PAD) were applied to determine the characteristic components of honey. While ubiquitous in most honeys, carbohydrates, terpene derivatives, and phenylacetic acid dominated in the Soxhlet extracts (25.54%) and in the application of SPE (13.04%). In addition, lumichrome (1.85%) was found, and may be considered as a marker of this honey. Due to the presence of these …

Supported liquid membrane extraction with single hollow fiber for the analysis of fluoroquinolones from environmental surface water samples

2010

Abstract In this work, the simple analytical method for the determination of four fluoroquinolone antibiotics: ciprofloxacin, enrofloxacin, norfloxacin and danofloxacin, in environmental surface water samples is described. Sample pretreatment step was performed by the application of a technique based on supported liquid membrane extraction with the configuration of single hollow fiber (HF-SLM). The HPLC system with diode array detection was used for final analysis of studied analytes. Various parameters affecting the extraction efficiency during HF-SLM enrichment, such as type of membrane diluent, pH of donor (sample) and acceptor phases, as well as an enrichment time and salt content of sa…

Enantiomer separation by chiral-phase liquid chromatography of urethane derivatives of natural diacylglycerols previously fractionated by reversed-ph…

1991

Abstract Enantiomers of diacylglycerols such as 3,5-dinitrophenyl isocyanate (urethane) derivatives previously fractionated by reversed-phase high-performance liquid chromatography (HPLC) were separated by HPLC on a chiral phase column [N-( R )-1-(α-naphthyl)ethylamino-carbonyl-( S )-valine chemically bound to γ-aminopropylsilanized silica]. In addition to the separation of commercial monoacid-diacylglycerol isomers, separation of diacid-diacylglycerol isomers obtained from peanut oil and cottonseed oil triacylglycerols by chemical hydrolysis is reported. Hexane-ethylene dichloride-ethanol mixtures were used for elution of the diacylglycerol derivative isomers, which were detected by their …

Analysis and fractionation of natural source diacylglycerols as urethane derivatives by reversed-phase high-performance liquid chromatography

1991

Abstract Reversed-phase high-performance liquid chromatography on a thermostatted octadecylsilyl column was used to separate and fractionate mixtures of diacylglycerols after derivatization with 3,5-dinitrophenyl isocyanate (urethane derivatives). In addition to the separation of commercial diacylglycerol species, the separation of diacylglycerols obtained from peanut oil and cottonseed oil triacylglycerols by chemical hydrolysis is reported. Acetonitrile-acetone mixtures were used for elution of the diacylglycerol urethane derivatives. Unsaturated and saturated derivatives were detected by their refractive indices. They were then collected and their fatty acids analysed as methyl esters by…

Separation of monoacylglycerols by reversed-phase high-performance liquid chromatography

1992

Abstract Reversed-phase high-performance liquid chromatography on a thermostated octadecylsilyl column was used to separate complex mixtures of monoacyglycerols formed by chemical deacylation of natural triacyclycerols. Acetonitrile-water mixtures were used for elution of the underivatized monoacylglycerols and a different refractometer was used for their detection. The order of elution of monoacylglycerols in complex mixtures varies as a function of the chain length, unsaturation, positional isomerism, analysis temperature and eluent water concentration. The peak areas were representative of the amounts of monoacylglycerols detected. The method can be applied to compositional analysis and …

Determination of molecular species of oil triacylglycerols by reversed-phase and chiral-phase high-performance liquid chromatography

1991

A method is described for the determination of molecular species of oil triacylglycerols. The method is based on the analytical separation of the enantiomericsn-1,2-andsn-2,3-diacylglycerols, derived from triacylglycerols, by high-performance liquid-chromatography (HPLC) on a chiral column containing N-(R)-1-(α-naphthyl)ethylaminocarbonyl-(S)-valinecarbonyl-(S)-valine as stationary phase. Model triacyl-glycerol molecules comprising three known fatty acids were isolated from peanut oil and cottonseed oil by a combination of argentation-TLC and reversed-phase HPLC and submitted to partial chemical deacylation. The derivedsn-1,2(2,3)-diacylglycerols were analyzed and fractionated as 3,5-dinitr…

Analysis of LSD in human body fluids and hair samples applying ImmunElute columns.

2000

Immunoaffinity extraction units (LSD ImmunElute) are commercially available for the analysis of lysergic acid diethylamide (LSD) in urine. The ImmunElute resin contains immobilized monoclonal antibodies to LSD. We applied the ImmunElute procedure to serum and also to human hair samples. For hair analysis the samples were first extracted with methanol under sonication. The extracts were then purified using the ImmunElute resin. LSD analysis was carried out with HPLC and fluorescence detection. The immunoaffinity extraction provides highly purified extracts for chromatographic analysis. The limit of detection (signal-to-noise ratio = 3) has been determined to be < 50 pg regardless of which sa…