A rapid and simple method is described for the preconcentration and discrimination between the organic fraction and the labile fraction of the metals Mn, Cd, Cu, Z, V, Ni, Pb, and Fe from seawater using 8-hydroxyquinoline, which forms neutral complexes with these metals, followed by adsorption on C18 chemically bonded silica gel. The sample flow rate through the C18 column was about 4 ml min. T...

This study was conducted to analyze carotenoids from tomatoes by high-performance liquid chromatography using reversed-phase C18 silica having cross-linked end-capping with diode array and mass spectrometric detection. An efficient gradient elution system was developed to achieve good and reliable separation of both major and minor carotenoids as well as their isomers. Resolution of lycopene, β...

Several isocratic separations for the determination of 20 steroids (STER) in animal feeding water samples (AFWS) from drinking-trough by LC using a mobile phase ACN/H(2)O (35:65 v/v) and different RP columns (Hypersil C18, Gemini C18 (GM), Purospher Star C18, Synergi Max C12, and Synergi Fusion) and UV detection were obtained. The elution order was the same: a first group of corticoids (CC) was...

Pre-column conversion of ammonia and a number of aliphatic amines into phenylthiourea or its derivatives by reaction with phenyl isothiocyanate, followed by HPLC, has been used for their determination in environmental waters. Optimum conversion was found when the reaction was carried out in sodium hydrogencarbonate– carbonate medium at 40 °C for 15 min. Well separated peaks were obtained on a C...

On the basis of the integrable Kaup-Boussinesq version of the shallow water equations, an analytical theory of undular bores is constructed. The problem of the decay of an initial discontinuity is considered.

We have determined routinely administered benzodiazepines and some of their metabolites in clinical samples by using on-line column switching for sample clean-up and reversed-phase high-pressure liquid chromatography (HPLC). The plasma sample is directly injected onto a cyanopropyl (CN) pre-column, washed with buffer, and eluted onto an analytical column (C18, octadecylsilane). Analytical recov...

Vietnam's sea is assessed to be very diverse and rich in seaweed species. It about 1000 different species of seaweed, which more than 800 have been identified, classify into genus, families, classes, phylums, continuously updated from the 1950s present. Previous studies by Vietnamese international scientists shown that lipids contain many valuable active ingredients such as acids C20: 4n-6 (AA)...