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A series of racemic nine o,o-dialkyl-2-benzyloxycarbonyl-aminoarylmethyl-phosphonate enantiomers has been separated by high performance liquid chromatography on cellulose tri(3,5-dimethyl-phenylcarbamate) and N-(3,5-dinitrobenzoyl) leucine (DNB-leu) chiral stationary phases. The chromatographic parameters, the capacity factor (k), separation factor (α), and the resolution factor (Rs) of all solutes are presented. The influence of the mobile phase composition on the enantioselectivity has been discussed. [ABSTRACT FROM AUTHOR]

Amphotericin B (AmB) is an important antifungal agent available in the clinical practice with the action mechanism related to the inhibition of ergosterol molecule present in the fungal cell wall. Given this, in order to expand AmB knowledge, this review article gathers important information of the AmB physical, chemical, and biological properties. In addition, the main analytical methods for quantifying and determining the AmB were also reported in this review, such as high-performance liquid chromatography (HPLC), liquid chromatography, tandem mass spectrophotometry (LC-MS/MS), immunoenzymatic assay (ELISA), capillary zone electrophoresis (CE) stands out and among others. Based in this review article, the scientific community will have important information to choose the best method for analysis in their scientific or clinical research, providing greater security and reliability in the obtained results. [ABSTRACT FROM AUTHOR]

This work describes three phase dispersive liquid-liquid microextraction based on reverse micelles for the determination of Q-markers of cinnamic acids (caffeic acid, p-hydroxycinnamic acid, ferulic acid, and cinnamic acid) in traditional Chinese medicine followed by high performance liquid chromatography (HPLC) analysis. The variables influencing the procedure were optimized separately. Enrichment factors from 110 to 189, linearities from 1.2 to 960 ng mL−1 with r2 exceeding 0.9943, detection limits from 0.1 to 0.6 ng mL−1, excellent precision with relative standard deviations below 5.6%, and good relative recoveries from 80.0% to 113.3% were achieved. In addition, the mechanism of the procedure was explored by comparison with conventional dispersive liquid-liquid microextraction at the optimum conditions. The results showed that the developed microextraction procedure improved the sensitivity and consumed less organic solvent and is a greener approach. [ABSTRACT FROM AUTHOR]

Neonicotinoids are systemic pesticides used to control harmful insects. These pesticides, which are nerve agents, cause many harmful effects to insects, especially to individual bees, such as damaging memory and reducing queen numbers. Here, we present a review concerning the determination and control of neonicotinoids residues in the agri-food sector, considered of vital importance to maintain food quality and safety. We discuss the different sample treatments and methods of analysis for the screening and quantification of neonicotinoids. Even though high-performance liquid chromatography with ultraviolet detection and mass spectrometry (HPLC-UV and HPLC-MS) are the most widely used analytical methods for the determination of these pesticides, there are alternative spectroscopic methods that can provide valuable information. We have thus carried out a critical discussion of the advantages and disadvantages of the different sample treatments and different techniques that have been developed in the last decade for the quantification of neonicotinoids in samples from the agri-food sector. [ABSTRACT FROM AUTHOR]

A new technique for the rapid detection and analysis of triterpenic compounds in apple extracts using HPLC was developed and validated. The main advantage of this technique is the short duration of the analysis - this makes this technique superior to others currently applied for the routine HPLC analysis of triterpenic compounds. The developed, optimized, and validated technique was used for the evaluation of triterpenic compounds in samples of different cultivars of apples, their peels, and flesh. In total, four triterpenic compounds were isolated and identified. Ursolic acid was the dominant compound in all the tested apple samples. The highest amounts of triterpenic compounds were detected in the peels of the 'Lodel' apple cultivar, and thus apples of this cultivar may be potentially useful for the isolation of individual compounds and the production of functional food and dietary supplements. [ABSTRACT FROM AUTHOR]

The bulb ofLycoris radiataas a traditional folk medicine is well known for its biological activities and has been used for the treatment of many diseases. The major chemical ingredients of this herb are alkaloids including lycoramine, galantamine, and so on. In order to further articulate the pharmacological activities of the herb, relatively purified alkaloids are needed. Therefore, a rapid and efficient method for the isolation and purification of these alkaloids from the bulb of Lycoris radiata is of great interest. We herein report a new technique pH-zone-refining counter-current chromatography (CCC) combined with preparative high-performance liquid chromatography (HPLC) for the isolation and purification of these active ingredients. Although the conventional high-speed HSCCC method for the successful separation of the alkaloids fromLycoris radiatahas been reported, only two alkaloids are obtained. In the present study, seven alkaloids all with a purity of over 95% are successfully separated using this combinative technique. And the sample loading capacity is increased by 150-fold compared with that mentioned in the literature. Therefore, the combinative application of pH-zone-refining CCC and preparative HPLC is a rapid and efficient method for the separation and purification of natural compounds. [ABSTRACT FROM AUTHOR]

Hippophae rhamnoidesL., a fruit which is rich in natural chemical ingredients, has become an important raw material of health food, medicine, and cosmetics. In the present work, a method using 2-(5-benzoacridine)ethyl-p-toluenesulfonate as pre-column derivatization reagent with high sensitivity, selectivity, and short separation time was developed to analyze triterpenic acids (TTAs) inH. rhamnoidesL. by HPLC with fluorescence detection and simultaneously confirmed by post-column atmospheric pressure chemical ionization-mass spectrometry. The method was validated by linearity, limits of detection (LODs) and lower limits of quantification (LLOQs), precision, and accuracy. Good linear correlations were observed for all TTAs with correlation coefficients greater than 0.9996. LODs and LLOQs were in the range of 1.71–2.14 and 7.45–8.23 ng mL−1, respectively. The method was successfully employed to analyze TTAs inH. rhamnoidesL. from various origins in the Qinghai–Tibetan plateau with trace amount of samples within 15 min. A systemic mapping of the TTAs inH. rhamnoidesL. of different origins was established. The results indicated thatH. rhamnoidesL. is rich in TTAs, especially in oleanolic and ursolic acids, and the content of TTAs varies across origins. This work will support the research on pharmaceutical applications ofH. rhamnoidesL. and provide information for quality control. [ABSTRACT FROM PUBLISHER]

Molecular mechanics (MM) and molecular dynamics (MD) were used to study the π–π interaction between polynuclear aromatic hydrocarbon (PAH) and pyrene bonded silica phase. There was a good correlation coefficient (r = 0.9330, P = 2.4 × 10−4) between the logarithmic retention time (ln Tr) of PAHs and −ΔG. However, there was no linearity between the retention time of substituted benzene or naphthalene compounds on pyrene bonded silica stationary phase and ΔG. Quantitative structure–retention relationship (QSRR) had been used to study the relationship of retention time and microstructure. However, by using QSRR for the substituted benzene or naphthalene derivatives, we obtained good correlation coefficient between retention time and microstructures (r2 = 0.962, F-test = 104.198). The MM, MD, and QSAR are very useful methods to study the π–π interaction in chromatography. [ABSTRACT FROM AUTHOR]

The objective of this study was to establish a hand-saving method to measure phenylmercapturic acid (PMA) and to examine urinary PMA as a marker of occupational exposure to benzene at levels less than 1 ppm. A simple HPLC method was developed to analyse PMA by monitoring absorption at 195 nm of the effiuent from an ODS-3 column with acetonitrile-methanol-perchloric acid-water as a mobile phase. The detection limit of the method was 0.2 μg l[sup -1] with sufficient reproducibility. The method was applied to end-of-shift urine samples from 70 gasoline station attendants exposed to up to 107 ppb benzene, and 20 non-exposed controls of both sexes. Time-weighted average (TWA) exposure to benzene was measured by diffusive sampling. A regression analysis was applied to examine the quantitative relationship between the intensity of exposure to benzene and PMA in the end-of-shift urine samples. Multiple regression analysis showed no effects of age, sex, smoking and co-exposure to toluene and xylenes on urinary PMA. There was a linear relationship between TWA benzene exposure and urinary PMA (r=0.60-0.67, P<0.01). Background PMA in urine of the non-exposed controls was low and scattering of PMA around the regression line was narrow so that those with 20 ppb benzene exposure can be separated from the non-exposed by urinalysis for PMA. Thus, urinary PMA is sensitive enough for biological exposure monitoring of those exposed to less than 1 ppm benzene. [ABSTRACT FROM AUTHOR]