STANDARDIZATION OF HPLC MEASUREMENTS OF PYRIDINIUM CROSS-LINKS

Measurement of the total amount of the two crosslinks, pyridinoline an d deoxypyridinoline, can be made simultaneously by high pressure liqui d chromatography preceded by an acidic hydrolysis of the sample and an extraction on cellulose columns. To compensate for the losses and var iation in the extraction procedure and increase precision and accuracy a suitable internal standard should be used. A simple procedure to is olate a compound to be used as an internal standard is discussed. With this compound a total, long term coefficient of variation of 7% and 5 % for the two crosslinks is achieved. The present inter-laboratory var iation reflected by the big differences in reference intervals is prob ably due to the presence of several different ways to purify and quant ify crosslinks to be used as calibrators. Recently the molar absorptiv ity for both pyridinoline and deoxypyridinoline in the ultra violet ra nge has been defined. This may be the first step towards the creation of a primary international reference material.