Teriparatide concentration was measured with an Agilent 1200 HPLC system (Agilent Technologies, Santa Clara, CA, USA) coupled with an UV-detector. A Supleco Biowide C18 column (4.6 mm × 150 mm × 5μm) was employed to determine peptide concentrations from 20 μL injections. The mobile phase consisted of 0.1% trifluoroacetic acid (TFA) in water (mobile phase A) and 0.1% TFA in acetonitrile (mobile phase B). Gradient elution started with 20% B at a flow rate of 1.0 mL/min and was held for 2 min prior to increasing to 60% over the course of 4 min. The % B was then increased to 100% over 0.2 min where it was held for 1 min prior to decreasing back to 20% B. The column temperature was set at 25 °C, and UV absorbance monitored at 210 nm. Sample teriparatide concentrations were determined against a calibration curve (range 5 -100 µg/mL).