Comparative equilibration and online technique for determination of non-exchangeable hydrogen of keratins for use in animal migration studies

Stable hydrogen-isotope ratios (δD) of keratin provide a novel means for tracking geographical movements of birds and other species. Here we describe a rapid, low cost, analytical approach to facilitate online continuous-flow isotope-ratio mass spectrometry (CF-IRMS) δD analyses of keratins (120-160 samples per day) through the use of calibrated keratin working standards and "comparative equilibration" to correct for the effects of moisture on exchangeable hydrogen. It is anticipated that this analytical approach and CF-IRMS will greatly aid in providing cost effective and directly comparable δD results on keratins and feathers among various laboratories and researchers involved in animal migration studies.