Determination of Macrolides in Water Using Solid-Phase Extraction and Supercritical Fluid Chromatography-Tandem Mass Spectrometry.

Macrolides are a group of compounds used to treat bacterial infections in humans and animals. Their widespread use results in the contamination of the water environment, which, on the one hand, has a detrimental effect on aquatic organisms and, on the other hand, can lead to the emergence of resistant strains of microorganisms. All of the above determines the need for monitoring of these compounds in the environment, particularly, in water objects.

Entropy driven separation of xylene isomers on graphitic carbon adsorbents.

Separation of xylene isomers remains one of the most important and challenging applications of adsorption-based separations in petrochemical industry. Despite the sustainable success of zeolite-based separations a search for efficient adsorbents selective for xylenes, especially para-xylene, is constantly ongoing. In this work, a potentially scalable chromatographic separation of all three xylenes was achieved on graphitic carbon sorbents, including a self-packed sorbent based on an oligo-graphene.

Rapid determination of phthalates in paper products by supercritical fluid chromatography/tandem mass spectrometry.

Phthalic acid esters are widely used as components of industrial and consumer products including paper and cardboard packaging materials in contact with food or human skin. Being endocrine-disrupting chemicals, phthalic acid esters have a negative effect on human health and must be controlled in pulp and paper products. In the present study, supercritical fluid chromatography-tandem mass spectrometry in combination with pressurized liquid extraction was proposed for phthalic acid esters determination in such objects.

Rapid Simultaneous Quantification of 1-Formyl-2,2-Dimethylhydrazine and Dimethylurea Isomers in Environmental Samples by Supercritical Fluid Chromatography-Tandem Mass Spectrometry.

When released to the environment, the rocket fuel unsymmetrical dimethylhydrazine (UDMH) undergoes oxidative transformations, resulting in the formation of an extremely large number of nitrogen-containing transformation products, including isomeric compounds which are difficult to discriminate by common chromatography techniques. In the present work, supercritical fluid chromatography-tandem mass spectrometry (SFC-MS/MS) was proposed for resolving the problem of fast separation and simultaneous quantification of 1-formyl-2,2-dimethylhydrazine (FADMH) as one of the major UDMH transformation products, and its isomers-1,1-dimethylurea (UDMU) and 1,2-dimethylurea (SDMU). 2-Ethylpyridine stationary phase provided baseline separation of analytes in 1.

Supercritical Fluid Chromatography-Tandem Mass Spectrometry for Rapid Quantification of Pentacyclic Triterpenoids in Plant Extracts.

Pentacyclic triterpenoids (PCTs) are a widely distributed class of plant secondary metabolites. These compounds have high bioactive properties, primarily antitumor and antioxidant activity. In this study, a method was developed for the quantitative analysis of pentacyclic triterpenoids in plants using supercritical fluid chromatography-tandem mass spectrometry (SFC-MS/MS).

Some aspects of additives effects on retention in supercritical fluid chromatography studied by linear free energy relationships method.

This work is dedicated to the investigation of additives effects on retention mechanisms in supercritical fluid chromatography. Additives are compounds which are added to the mobile phase in small quantities and greatly affect retention factors, peak shape, separation selectivity and other chromatographic parameters. Linear free energy relationship (LFER) method with an expanded set of descriptors including the ones taking ionic interactions into account was used to probe the effect of four types of additive: trifluoroacetic acid, diethylamine, ammonium acetate and water - on retention on four polar stationary phase bearing different functional groups: bare silica, cyano, 2-ethylpyridine and zwitter-ionic sulfobetaine.

Screening and semi-quantitative determination of pentacyclic triterpenoids in plants by liquid chromatography-tandem mass spectrometry in precursor ion scan mode.

Introduction: Pentacyclic triterpenoids (PCTs) are secondary plant metabolites. They are of exceptional interest as biologically active substances and raw materials for a wide range of medications. Thus, the development of a methodology for rapid screening of PCTs in plant biomass is an important task.

Evaluation of temperature and pressure effects on retention in supercritical fluid chromatography on polar stationary phases.

Four polar stationary phases (ethylene-bridged hybrid silica, cyanopropyl, 2-ethylpyridine, and zwitterionic sulfobetaine) have been characterized in supercritical fluid chromatography (SFC) by linear free energy relationships (LFER) method with an extended set of Abraham's descriptors. Temperature (25-55 °C) and pressure (110-180 bar) effects on analyte retention, separation selectivity and LFER-coefficients of chromatographic systems have been studied using the 89 test compounds of various chemical classes and carbon dioxide - methanol (9:1 v/v) binary solvent as a mobile phase. It was found that for the selected stationary phases temperature and pressure had only moderate effects on selectivity.

A case of Z/E-isomers elution order inversion caused by cosolvent percentage change in supercritical fluid chromatography.

A case of elution order inversion caused by cosolvent percentage change in supercritical fluid chromatography was observed and investigated in some detail. Z- and E-isomers of phenylisobutylketone oxime experience an elution order reversal on most columns if the mobile phase consists of CO and alcohol. At lower percentages of alcohol Z-oxime is retained less, somewhere at 2-5% coelution occurs and at larger cosolvent volume elution order reverses - Z-oxime is eluted later than E-oxime.