Acids HPLC analysis

Recently, Peace and Gilani [229] reviewed chromatographic determination of amino acids. HPLC analysis of free amino acids can be a powerful tool in the control of food authenticity. Cotte et al. [230] demonstrated that HPLC analysis of free amino acids, followed by statistical processing of... 

Chlorination of Individual Amino Acids. HPLC analysis of an extract of chlorinated humic acids indicated that the chlorination products compose a highly complex mixture of organic material. Thus, the task of identification of mutagenic products of chlorination would not be simplified by the use of the humic acid model. In contrast, the amino acid model of production of mutagenic compounds can be readily simplified by the use of individual compounds as precursors. 

Homogenates of lymphocytes were preincubated at either 15 or 30°C for 10 minutes before the reaction was started, by addition of 3-hydroxykynure-nine to a final concentration of 1 mM. When the assay was performed at 30°C, the presence of 4 pM pyridoxal-5 -phosphate was needed to obtain a linear reaction. The reaction was terminated after 5 minutes by the addition of 150 piL of 10% trichloroacetic acid. HPLC analysis was carried out on 30 / L of the supernate obtained after centrifugation. 

Sequencing of Romalea PDF was straight forward, and it also proved to be an octadecapeptide (40). The Romalea peptide differs from Acheta PDF at a single position, the former having Leu-14 in place of Val-14. In these peptides the presence of Asp-Ala bond, positions 17-18, permitted the cleavage of the C-terminal residue by heating in dilute acid. HPLC analysis of the derivatized cleaved product enabled the identification of the C-terminus as Ala-amide. 

Most papers dealing with phenolic acid HPLC analysis in herbs describe only simple liquid extraction without the hydrolysis step. Acetone, methanol, or alcoholic-water or acetone-water mixtures are applied. Very rarely, pure water is used as the extraction solvent. " It was found that the extraction recoveries for water extracts are often lower in comparison to alcoholic-water mixtures, especially when the simultaneous separation of polar and less polar phenolic acids has been performed. Sometimes, the control of pH can improve the recovery. If necessary, n-hexane, chloroform, diethyl ether, benzene-acetone, petroleum ether, or other less polar solvents are recommended for removing interfering compounds. The extraction is usually performed by refluxing the samples for a specific time in a Soxhlet apparatus, with simple mechanical or magnetic stirring of the sample with the extraction solvent, or by plant sample maceration. The application of an ultrasonic bath for the liquid extraction has also become popular in recent years. The hydrolysis steps have also been recommended for medicinal species preparation, especially when other phenolic compounds are also analyzed simultaneously with phenolic acids in herbs. 

Figure 6. Membrane assisted condensation of amino acids. HPLC analysis (at 289 nm) of the products of the oligomerization of NCA-Trp assisted by POPC liposomes. There are several products (for reaction conditions and other details see ref. 21). It is important to notice the difference between the liposome-assisted oligomerization (A) and the control experiment, in the absence of liposomes (B). In this second case, the highest product has a oligomerization degree n = 7 in the case of liposomes we reach n = 29, although in minimal amounts.

Amino Acids HPLC Analysis Advanced Techniques... 

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