A simple and automated HPLC method for determination of total hydroxyproline in urine. Comparison with excretion of pyridinolines

Chromatography and atomic absorption spectrometry for the assessment of heavy metal distribution among amino acids used in parenteral nutrition formulations-studies with cadmium and lead

The distribution of Cd (II) and Pb (II) among amino acids in parenteral nutrition formulations was investigated by coupling ion-chromatography (HPLC/IC) and electrothermal atomic absorption spectrometry. The methodology was based on ion-exchange separation and fluorimetric amino acid detection after post-column derivatization. Cd (II) and Pb (II) were assayed in 500-µL fractions of the column effluent. The distribution of Cd (II) and Pb (II) in alanine (Ala), aspartic acid (Asp), glutamic acid (Glu), glycine (Gly), histidine (His), methionine (Met), phenylalanine (Phe), serine (Ser), and threonine (Thr) were analyzed by monitoring changes in the concentration of free amino acids by HPLC/IC. The results indicated that Cd (II) and Pb (II) were distributed according to the following trend: Gly-Cd > Gly-Pb > Ala-Cd > Ala-Pb > His-Cd ∼ His-Pb > Thr-Cd > Thr-Pb > Phe-Cd ∼ Phe-Pb ∼ Asp-Cd ∼ Asp-Pb ∼ Met-Cd ∼ Met-Pb ∼ Glu-Cd ∼ Glu-Pb > Ser-Cd ∼ Ser-Pb. The effects of amino acid concentration and stability constants of amino acid-metal complexes are discussed.

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.

Response of several markers of bone collagen degradation to calcium supplementation in postmenopausal women with low calcium intake

We investigated the response of bone-specific resorption markers in fasting urine samples from postmenopausal women with low daily dietary calcium (Ca) intake (<800 mg/day) who received either Ca supplementation (1200 mg/day, n = 18) or placebo (n = 14) for 2 months. We measured urinary hydroxyproline, total pyridinoline, and deoxypyridinoline by HPLC, and free deoxypyridinoline (i-F-Dpd) and N- and C-telopeptide fragments of type I collagen (NTX and CTX) by immunoassays. Before supplementation, the urine concentrations of bone resorption markers in the 32 subjects were not statistically different from those measured in 21 subjects with daily dietary Ca intake >800 mg/day. In contrast to the placebo group, Ca supplementation decreased all collagen-related degradation markers except i-F-Dpd as early as the first month. The magnitude of response after 2 months of Ca supplementation, expressed as mean percentage of decrease from baseline values or as individual Z scores, was greatest for the telopeptide assays. Furthermore, the percentage of change assessed at 2 months was greater than the within-person biological variability (CV) assessed in the placebo-treated women for NTX and CTX, whereas for the other markers the percentage of change was very close of the within-person CVs. We conclude that cross-linked telopeptide fragments of type I collagen most sensitively reflect the change in bone resorption after Ca supplementation.