Rapid robust separation of hydroxyproline and proline

Selective Analysis of Secondary Amino Acids in Gelatin Using Pulsed Electrochemical Detection

A method was developed for selective analysis of the secondary amino acids proline and 4-hydroxyproline from gelatin hydrolysates using anion-exchange high-performance liquid chromatography followed by integrated pulsed amperometric detection (HPLC-IPAD). An extraction scheme was implemented prior to HPLC-IPAD analysis to isolate the secondary amino acids by the removal of primary amino acids through derivatization with o-phthalaldehyde followed by solid-phase extraction with C18 packed columns. The use of the IPAD technique eliminated the need for a second derivatization step to detect secondary amino acids. The removal of interfering primary amino acids prior to chromatographic analysis allowed the use of isocratic mobile-phase conditions to achieve effective and efficient separation of the amino acids. This led to a more precise and accurate quantitation of their content in gelatin hydrolysates. Detection limits approach 10 parts per billion ( approximately 2 pmol/injection) with a chromatographic analysis time under 8 min. The ratios of secondary amino acids, in addition to their abundances, were used to distinguish gelatin manufactured from bovine, porcine, and fish raw material sources.

Determination of free and total proline and hydroxyproline in plasma and tissue samples by gas chromatography with flame photometric detection

A selective and sensitive method for the determination of free and total proline (Pro) and 4-hydroxyproline (Hyp) by gas chromatography (GC) was developed. For free Pro and Hyp analysis, plasma and tissue homogenate were extracted with methanol. For total Pro and Hyp analysis, these samples were hydrolysed in 6 M HCl. After removal of primary amino compounds by the reaction with o-phthaldialdehyde, Pro and Hyp in methanol extract and acid hydrolysate were converted into their N-dimethylthiophosphoryl methyl ester derivatives and then determined by GC with flame photometric detection using a DB-5 capillary column. This method was successfully applied to small samples without prior clean-up, and Pro and Hyp in these samples could be analysed without any influence from coexisting substances. Overall recoveries of Pro and Hyp added to plasma and tissue samples were 92-106%. The analytical results of free and total Pro and Hyp in human plasma and mouse tissue samples are presented.