The high melting point in this study might be associated with the high content of imino acids (Pro and Hyp) (Kasankala et al., 2007).
For imino acids, gelatin had proline and hydroxyproline of 127 and 99 residues/1,000 residues, respectively.
A linear response up to 2 mmol/L has been demonstrated as well as a 10-fold increase in sensitivity compared with ninhydrin methods (11), with even greater sensitivity and higher linear responses for non-a-amino acids such as imino acids and (3-amino acids.
In conclusion, the advantages of the PITC HPLC method, such as high resolution, speed, and sensitivity for quantifying of imino acids, sulfur, and [beta]-amino acids, make it suitable for urine amino acid analysis, and its reliability and feasibility for clinical use has been demonstrated.