Cary ftir spectrometer

To assess the quality of the collagen, all extracts were analysed via EA-IRMS to obtain elemental (C%, N%, C:N) and stable isotopic data (δ¹³C and δ¹⁵N). Collagen (ca. 400 μg) was weighed into tin cups using a microbalance and measured on a ThermoFinnigan Flash EA coupled to a Thermo Delta plus XP isotope ratio mass spectrometer (IRMS). Stable carbon isotope ratios were expressed relative to VPDB (Vienna PeeDee Belemnite) and stable nitrogen isotope ratios were measured relative to AIR (atmospheric N₂), using the delta notation (δ) in parts per thousand (‰). Repeated analysis of both internal and international standards indicates an analytical error of 0.2‰ (1σ) for δ¹³C and δ¹⁵N. Where sufficient material was available, collagen (ca. 300 μg) was homogenized and mixed with ∼40 mg of IR grade KBr powder in an agate mortar and pestle, pressed into a pellet using a manual hydraulic press (Wasserman) and analysed with an Agilent Technologies Cary FTIR Spectrometer with a DTGS detector. Spectra were recorded in transmission mode at 4 cm⁻¹ resolution with averaging of 34 scans between 4000 and 400 cm⁻¹ using Resolution Pro software (Agilent Technologies). The spectra were evaluated and compared to library spectra of well-preserved collagen and bone to look for evidence of incomplete demineralisation, degraded collagen or the presence of any exogenous material in the extracts.

For the collagen extracts from Experiment B, ca. 0.3 mg collagen was homogenised and mixed with ∼40 mg of IR grade KBr powder in an agate mortar and pestle, pressed into a pellet using a manual hydraulic press (Wasserman) and analysed with an Agilent Technologies Cary FTIR Spectrometer with a DTGS detector. Spectra were recorded in transmission mode at 4 cm⁻¹ resolution with averaging of 34 scans between 4000 and 400 cm⁻¹ using Resolution Pro software (Agilent Technologies). The spectra were analysed and compared to library spectra of well-preserved collagen and bone.