Search results for "high-performance liquid chromatography"

Comparison of several methods used for the determination of cephalosporins. Analysis of cephalexin in pharmaceutical samples

2002

The precision of UV absorbance of intact and acid degraded cephalosporins, ninhydrin, high performance liquid chromatography and iodometric methods used for analysis of cefoxitin, cefotaxime, cephazolin and cephalexin were compared. To obtain the calibration graphs the analytical signal used were: absorbance, first derivative absorbance, second derivative absorbance and H-point Standard Additions Method by using absorbance values at two selected wavelengths as analytical signal. These methods and calibration graphs were also used for the determination of cephalexin in pharmaceutical samples.

Determination of pharmaceutical residues in wastewater using high performance liquid chromatography coupled to quadrupole-Orbitrap mass spectrometry

2016

Abstract A multi-class method for the determination of 24 emerging pharmaceutical residues has been developed and validated. The method is based on solid-phase extraction of wastewater samples using Strata-X cartridges followed by high performance liquid chromatography coupled to hybrid quadrupole − Orbitrap high resolution mass spectrometry (HPLC-Q-Orbitrap-HRMS). A single-laboratory validation procedure showed satisfactory analytical performance. The analysis of 21 samples collected at the wastewater treatment plant in Riga revealed the occurrence of 20 compounds of different therapeutic classes. The highest concentration was found for the central nervous system stimulator caffeine − up t…

Reversed Phase Liquid Chromatography

2015

On-line high-pressure extraction-high-performance liquid chromatography

1983

Abstract A coupling unit is described that allows on-line operation of a high-pressure extraction apparatus with a high-performance liquid chromatograph. The unit consists of two high-pressure sample-injection valves, connected in series. The first valve operates as a switching valve to the loop and controls the release of pressure along a packed microbore column. Two short, packed microbore columns are positioned between the first and second valve, sampling the extracted compounds over a desired period and simultaneously operating as sample loop for the second valve; the latter is the injector for the high-performance liquid chromatographic column. The unit was tested by continuous extract…

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 …