Extraction of steroids from urine with C18 solid-phase extraction cartridges results in an extract containing impurities. If, during the extraction of hydrolyzed urine, an amino (NH2) column is placed in series with the C18 column, then one obtains a sample that is sufficiently clean for gas-chromatographic analysis. Analytical recovery of dehydroepiandrosterone from urine is considerably decre...

The gas chromatography-flame ionization detector equipped with a higher polarity column (i.e., SP-2560) has often been used for the quantification of trans-fatty acids in food. In particular, AOCS Ce 1h-05, the official method of the American Oil Chemists' Society (AOCS), is a highly effective method to separate the isomers of trans-fatty acids. In this study, the resolution behavior and the re...

The character of a brass musical instrument is primarily dependent on its bore profile. Many historic brass instruments are so constructed that substantial parts of the air column are inaccessible to direct measurement. This paper discusses the factors involved and reports recent advances in the use of pulse reflectometry for bore reconstruction, in particular compensation for losses and allowa...

Recent changes in environmental regulatory paradigms, such as EPA’s performance-based measurement systems (PBMS), are lowering method compliance barriers for laboratories working under the Resource Conservation and Recovery Act (RCRA). One of the stated goals of PBMS is to educate the regulators and the regulated community on the inherent and intended flexibility of SW-846 methods. Operating un...

isolated five known iridoids glycosides (scrophuloside a, harpagoside b, 5-hydroxyloganin, 8-o-acetylharpagide and 6-o-methyl,1-glucopyranosyl catalpol ),one phenyl ethanoid glycoside (verbascoside) and a phenyl ethanol amine (2-(4-chlorobenzyl amino) ethanol ) compound from the methanolic extract of aerial parts of scrophularia oxysepala using by high performance liquid chromatography based on...

A highly sensitive analytical procedure is described for determining thiodiglycol in groundwater. Samples are initially fortified with 3,3'-thiodipropanol (surrogate), then both species are extracted using sequential solid-phase extraction with both C18 and Ambersorb 572 columns. The C18 column, which removes extraneous groundwater components, is discarded; the Ambersorb 572 column is dried tho...

CHEMISTRY General methods. All solvents and reagents were purchased from commercial sources and used without further purification. The compounds were spotted on silica TLC plates (Merck, Si 60 , F254), visualized under UV-light at 254 nm or iodine over silica. Purification of the compounds for biological tests was performed on a Waters 2767 system equipped with a photodiode array and an ESI mas...

Six compounds were analyzed through isocratic elution to demonstrate the effect of several instrument, method, and sample variables on column performance. A very efficient Agilent InfinityLab Poroshell 120 EC-C18, 2.1 × 50 mm, 1.9 μm column capable of generating nearly 14,000 plates was used in this work. The impact on column performance of system capillaries, detector flow cells, data collecti...

Polar metabolites of the arginine biosynthetic pathway are poorly retained in reversed phase C18 chromatography. Hydrophilic interaction chromatography (HILIC) is an option for separating polar metabolites such as amino acids. However, compared to RP chromatography, peaks in HILIC separations are often broader and column re-equilibration requires a longer time. To enable metabolic profiling of ...

A simple and rapid analytical method was established for detection of anabolic agents, zeranol and alpha-trenbolone and beta-trenbolone residues in cattle muscle and liver. This method consisted of aqueous acetonitrile extraction and successive solid-phase extraction with a tandem connected octadecyl (C18)-aminopropyl (NH2) cartridge, followed by on-line clean-up using multidimensional HPLC wit...