Method development and validation for melamine and its derivatives in rice concentrates by liquid chromatography. Application to animal feed samples.

An isocratic LC method for the determination of melamine and its degradation products (ammelide, ammeline, and cyanuric acid), used to increase the apparent protein content of rice protein concentrate, has been developed. Method development involved optimization of different RP columns, aqueous mobile phases, pH, phosphate concentration, and temperature. The optimum separation of these compounds was achieved using a Luna CN column (30 degrees C), 5 mmol L(-1) sodium phosphate (pH 5.

Sample preparation for the determination of steroids (corticoids and anabolics) in feed using LC.

An improved sample preparation procedure for the determination of 17 steroids (corticoids (CC) and androgenic anabolic steroids (AAS)), used potentially as growth promoters, in feed samples has been developed. This procedure is based on two reported LC-UV methods. The improved procedure includes a leaching process using ACN, saponification, and SPE using polymeric cartridges.

GC-MS method development and validation for anabolic steroids in feed samples.

A GC-MS method for the determination of AAS used as growth promoting agents using SIM in piglet feed samples has been developed and validated, using testosterone as internal standard. The formation of volatile steroid derivatives was carried out by derivatization with N-methyl-N-(trimethylsilyl)trifluoroacetamide. The optimum separation was achieved using a Zebron ZB-5 column under a gradient temperature elution, allowing the separation of steroids in 18 min.

Quantitative screening for steroids in animal feeding water using reversed phase LC with gradient elution.

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 early eluted, a second group of CC and anabolics (AAS) exhibited intermediate retention, and a third group constituted by AAS was strongly retained. To improve the separation performances of the isocratic separations an ACN gradient elution optimization was carried out for each column.

Method development validation for corticoids in animal feed samples by liquid chromatography using a monolithic column.

A LC method for corticosteroids (CC) determination in poultry feed using a Chromolith column and UV detection has been developed and validated. The method development involved the optimization of different hydro-organic mobile phases using methanol or ACN as organic modifiers, flow rate, and temperature. The optimum separation was achieved at 40 degrees C using ACN/water (21:79 v/v) as mobile phase and 3 mL/min flow rate, allowing the separation to baseline of four out of seven CC in about 10 min.