Search results for "liquid chromatography"
showing 10 items of 942 documents
Analytical capabilities of high performance liquid chromatography – Atmospheric pressure photoionization – Orbitrap mass spectrometry (HPLC-APPI-Orbi…
2015
A new analytical method was established and validated for the analysis of 27 brominated flame retardants (BFRs), including so called "emerging" and "novel" BFRs (EBFRs and NBFRs) in fish samples. High performance liquid chromatography (HPLC) coupled to Orbitrap mass spectrometry (Orbitrap-MS) employing atmospheric pressure photoionization (APPI) interface operated in negative mode was used for the identification/quantitation of contaminants. HPLC-Orbitrap-MS analysis provided a fast separation of selected analytes within 14 min, thus demonstrating a high throughput processing of samples. The developed methodology was tested by intralaboratory validation in terms of recovery, repeatability, …
Procedure for automated background correction in flow systems with infrared spectroscopic detection and changing liquid-phase composition
2009
This paper describes a partial least squares (PLS) based automatic procedure to correct for changes in the spectral contribution of the solvent or solvent mixtures from solute spectra recorded in these solvents. The procedure was developed for successful on-line Fourier transform infrared (FT-IR) detection in gradient high-performance liquid chromatography (HPLC) separations. It requires a reference FT-IR data set containing all possible combinations of the expected variation in solvent composition. Furthermore, a spectral region ( A) in these spectra is required where the solvents show absorption but the analytes do not. This is the case for the system ACN:H2O, an often-applied solvent mi…
In-tube solid-phase microextraction-capillary liquid chromatography as a solution for the screening analysis of organophosphorus pesticides in untrea…
2006
This paper describes a method for the selective screening of organophosphorus pesticides in water. In-tube solid-phase microextraction (SPME) in an open capillary column coupled to capillary liquid chromatography (LC) with UV detection has been used to effect preconcentration, separation and detection of the analytes in the same assembly. For in-tube SPME two capillary columns of the same length and different internal diameters and coating thicknesses have been tested and compared, a 30 cm x 0.25 mm I.D., 0.25 micro m thickness coating column, and a 30 cm x 0.1 mm I.D., 0.1 micro m of coating thickness column. In both columns the coating was 95% dimethylpolysiloxane (PDMS)-5% diphenylpolysi…
Validation of a confirmatory method for the determination of macrolides in liver and kidney animal tissues in accordance with the European Union regu…
2006
Abstract This study proposes a simple multiresidue liquid chromatography–diode array detector (LC–DAD) method capable of determining seven macrolide antibiotics in samples of liver and kidney animals at concentrations lower than those allowed by current legislation. Samples were prepared by homogenizing the tissue with EDTA–McIlvaine's buffer and extracted with an Oasis HLB cartridge. The consumption of organic solvent during extraction was minimum. The analytes were detected by LC–DAD and also by liquid chromatography–mass spectrometry with electrospray ionization (LC–(ESI)MS). The method was specific, stable and robust enough for the required purposes. The DAD method was validated in acco…
Column-switching techniques for high-performance liquid chromatography of drugs in biological samples.
1993
In recent years, an increasing number of publications have demonstrated the potential of column-switching techniques for the chromatographic separation, determination and preparative isolation of analytes from biological matrices. Column-switching systems greatly facilitate drug analysis, by on-line sample clean-up and trace enrichment, or by improving the analytical separative process. In this paper, the main applications of column-switching techniques to drug analysis in biological samples, are reviewed.
Environmentally friendly LC for the simultaneous determination of ascorbic acid and its derivatives in skin-whitening cosmetics
2008
Ascorbic acid (AA), also known as vitamin C, is a very popular skin-whitening agent used in cosmetics. However, the use of AA (and also its sodium or magnesium salts) in cosmetic products is limited owing to its labile oxidative properties. In order to avoid its early degradation, different derivatives have been designed, such as ascorbyl phosphate (APH; as magnesium or sodium salts) and ascorbyl palmitate (AP), and more recently the ascorbyl glucoside (AG). Bearing in mind that all these chemicals in skin-whitening cosmetic products must be determined in order to control the efficacy of such products, this paper focuses on developing a wide-ranging LC analytical method able to determine th…
Development and validation of a fast and sensitive chromatographic assay for all-trans-retinol and tocopherols in human serum and plasma using liquid…
2002
A sensitive HPLC assay for all-trans-retinol, alpha-tocopherol, and gamma-tocopherols in human serum and plasma is reported. Sample preparation is performed in one step and involves precipitation of proteins and extraction of lipids with two volumes of an ethanol-chloroform mixture (3:1, v/v) without I.S. addition. After removal of the precipitated protein, 20 microl aliquots of the supernatant (equivalent to 6.7 microl of serum or plasma) were injected into the HPLC system and analyzed using fluorometric detection. RP-HPLC was performed using a C(18) S3 ODS2 column with a methanol-water step gradient (97:3 to 100) at 1.0 ml/min. The quantification limit expressed as nanograms of analyte pe…
Control of propranolol intake by direct chromatographic detection of alpha-naphthoxylactic acid in urine.
2002
A rapid chromatographic procedure with a C18 column, a mobile phase of 0.15 M sodium dodecyl sulfate (SDS)-10% (v/v) 1-propanol at pH 3 (0.01 M phosphate buffer), and fluorimetric detection, is reported for the control of propranolol (PPL) intake in urine samples, which are injected directly without any other treatment than filtration. The peak of PPL was only observed in samples taken a few hours after ingestion of the drug due to its extensive conjugation and metabolisation. The detection of several unconjugated PPL metabolites was therefore considered: desisopropylpropranolol (DIP), propranolol glycol (PPG), alpha-naphthoxylactic acid (NLT) and alpha-naphthoxyacetic acid (NAC). NLT showe…
Micellar liquid chromatography determination of rivaroxaban in plasma and urine. Validation and theoretical aspects.
2019
A Micellar Chromatographic method to determine rivaroxaban in plasma and urine has been developed. The samples were dissolved in the mobile phase (SDS 0.05 M – 1-propanol 12.5%, phosphate buffered at pH 7) and 20 μL directly injected, avoiding the extraction and purification steps. Using a C18 column and running under isocratic mode at 1 mL/min, analyte was eluted without interference from the matrix in <6.0 min. The detection absorbance wavelength was set to 250 nm. The procedure was validated by Food and Drug Administration guidelines in terms of: system suitability, calibration range (0.05–5 mg/L), linearity, sensitivity, robustness, carry-over effect, specificity, accuracy (−11.1 to 4.2…
Generalised H-point standard addition method for the isolation of the analyte signal from the sample signal when coelution of unknown compounds occur…
1999
The generalised H-point standard addition method (GHPSAM) is proposed for isolating the analytical signal of an analyte from the signal of an unknown sample. Samples containing two and three coeluting compounds have been analysed. The accuracy of the predictions depends on the shape of the analyte and interferent spectra but not on the degree of chromatographic overlap. This methodology involves the location of linear intervals for the unknown interference spectrum from the spectrum of the sample. Once the linear interval has been found the selection of three wavelengths within the interval will allow the cancellation of the signal of the unknown interferent. The method has been applied to …