Search results for " analytic"
showing 10 items of 1718 documents
Comparison of surfactant-mediated liquid chromatographic modes with sodium dodecyl sulphate for the analysis of basic drugs
2020
In reversed-phase liquid chromatography (RPLC), basic drugs are positively charged at the usual working pH range and interact with free anionic silanols present in conventional silica-based stationary phases. This translates into stronger retention and tailed and broadened peaks. This problem can be resolved by the addition of reagents to the mobile phase that are adsorbed on the stationary phase, avoiding the access of solutes to silanols. Among these additives, surfactants under micellar conditions have provided good silanol suppressing potency through the technique known as micellar liquid chromatography (MLC). The most common example of this is anionic sodium dodecyl sulphate (SDS). Whe…
A rapid and sensitive method for the control of selected regulated and emerging mycotoxins in beer
2018
A fast method using automated online solid-phase extraction (SPE) coupled to liquid-chromatography/high resolution mass spectrometric (LC-HRMS) detection for the determination of 12 mycotoxins in beer was developed and fully validated according to the performance criteria set in the European Union (EU) guidelines. Mycotoxin detection was achieved by full-scan HRMS with electrospray ionisation in positive ion mode within 13 min. No significant matrix interferences were observed. The lowest limits of detection (LODs) were achieved for emerging mycotoxins (beauvericin and enniatins) and ochratoxin A at levels between 0.01 and 0.02 μg/l, while the overall LODs were in the range of 0.01-0.30 μg…
Determination of antifreeze substances in the airport runoff waters by solid-phase microextraction and gas chromatography–mass spectrometry method
2016
Abstract A new method has been developed for the determination of antifreeze agents such as ethylene glycol (EG), propylene glycol (PG), and diethylene glycol (DEG) in the samples of airport runoff water. The method is based on headspace solid–phase microextraction (HS–SPME) of target analytes, which is coupled with gas chromatography–mass spectrometry (GC–MS). Until now, there was a lack of appropriate methodology for collecting reliable data about the concentration levels of these toxic de/anti-icing substances in the new type of environmental samples such as the airport runoff water. The evaluation of green extraction technique, i.e., HS–SPME resulted in establishing the optimal extracti…
Mycotoxins in cereals and pulses harvested in Latvia by nanoLC-Orbitrap MS
2021
Twenty-seven mycotoxins in unprocessed cereals (n = 110) and pulses (n = 23) harvested in Latvia were analysed by nanoflow liquid chromatography combined with Orbitrap high-resolution mass spectrometry. One or more mycotoxins were found in 99% of the cereals and 78% of the pulses. Deoxynivalenol, zearalenone and T-2 and HT-2 toxins were prevalent in 9 to 86% of the cereals, mostly below their maximum levels as set by the European regulations. Non-regulated type A and B trichothecenes were prevalent in 5 to 87% of the cereals, at concentrations of 0.27–83 µg kg−1 and 1.7–4,781 µg kg−1, respectively. Quantification of emerging mycotoxins was also provided. Enniatins were detected in 94% of th…
Stationary phase modulation in liquid chromatography through the serial coupling of columns: A review
2016
Liquid chromatography with single columns often does not succeed in the analysis of complex samples, in terms of resolution and analysis time. A relatively simple solution to enhance chromatographic resolution is the modulation of the stationary phase through the serial coupling of columns. This can be implemented with any type of column using compatible elution conditions and conventional instruments. This review describes the key features of column coupling and published procedures, where two or more columns were coupled in series to solve separation problems. In all reports, the authors could not resolve their samples with single columns, whereas significant enhancement in chromatographi…
Review: Determination of Vitamin D in Dairy Products by High Performance Liquid Chromatography
2005
This work reviews the methods used for the determination of vitamin D in some dairy products (milk and infant formulas) by high performance liquid chromatography (HPLC). The low vitamin D contents and the presence of interfering compounds require sample treatment and purification of the extract. The advantages and drawbacks of hot and cold saponification, direct extraction and different types of extract purification are also discussed, taking into account the lack of vitamin D stability by heating, exposure to light and oxidation. With respect to chromatographic determination, the mode (normal or reverse phase), type of column (microcolumn or conventional) and detection system (UV, electro…
Gas chromatography-fourier transform infrared spectrometry of fatty acids: New Applications with a direct deposition interface
1998
Infrared spectroscopy is a suitable spectroscopic method to differentiate geometric Z and E isomers of unsaturated compounds. A direct-deposition Fourier transform infrared spectrometer (FTIR), coupled to a gas chromatograph, was used successfully to analyze with a high sensitivity traces of C18:1 fatty acid methyl ester (FAME) isomers. It could also conclusively distinguish between isomers of conjugated diunsaturated FAME. The achievable sensitivity of this direct-deposition device makes possible accurate FAME mixture analyses that are not currently attainable with the more conventional light-pipe interface.
Synthesis and sorptive properties of molecularly imprinted polymer for simultaneous isolation of catecholamines and their metabolites from biological…
2021
Simultaneous quantitative analysis of catecholamines (CAs) and their respective acid metabolites in biological fluids can become a powerful tool for diagnosis and treatment of various diseases. However, selective sample preparation procedure is necessary to isolate the aforementioned analytes from the matrix. Therefore, we propose a synthetic strategy for the preparation of a molecularly imprinted sorbent with binding sites for both CAs and their respective acid metabolites. The synthesis combines noncovalent and semicovalent imprinting methods. Methylenebisacrylamide, 4-vynilbenzyl-N,N,N-trimethylammonium (3,4-dimethoxyphenyl)acetate, and 3-phenylpropylacrylate were used as the cross-linke…
Eucalyptol-based green extraction of brown alga Zonaria tournefortii
2018
Abstract A green extraction method, based on the use of 1,8-cineole (eucalyptol) as biosolvent, has been developed to prepare crude extracts from the brown alga Zonaria tournefortii characterized by chemical composition, particularly dominated by phenolic compounds derived from phloroglucinol. The main advantage of the developed technique are the recovery of eucalyptol, based on multistep liquid-liquid extraction with distilled water, followed by centrifugation and elimination of the aqueous phase, and the complete recycling of biosolvent by steam distillation. A comparative study between the proposed green extract and the conventional extract, prepared by solvent maceration using the mixtu…
Comparison of photodiode array, evaporative light scattering, and single-quadrupole mass spectrometric detection methods for the UPLC analysis of pyr…
2017
ABSTRACTIt is important to analyze pyrolysis liquids to evaluate the yield of valuable products as well as unfavorable by-products. This work focuses on choosing detectors for reversed-phase ultra high-performance liquid chromatography analysis of pyrolysis liquids. The linearity, sensitivity, precision, and recovery of photodiode array (PDA) detector, single-quadrupole mass spectrometer (MS), and evaporative light scattering (ELS) detector were compared for the quantitative determination of several typical compounds found in pyrolysis liquids. PDA and MS detectors were found to be suitable for the quantification of furans and phenol derivatives (furfural, vanillin, syringol), but sugars an…