Ionpac as15

The mudstone encapsulated bone was processed inside a UV sterilized laminar flow hood. The fossil bone fragments and adjacent mudstone were carefully separated and bone surface was scraped off (hereafter referred to as scrapings) with a flame-sterilized autoclaved razor. The cleaned bone with outer surface removed, along with the scrapings and the surrounding mudstone matrix were powdered separately with sterilized mortars and pestles. To determine the water-extractable anions, 0.1 g of each powder fraction was thoroughly mixed with 1 mL Milli-Q H₂O and incubated overnight before measurement. The slurry was centrifuged at 14,000×g for 5 min and the supernatant was then filtered with 0.22 μm filter membrane for ion chromatography analyses. All samples (in triplicate) were analyzed on a Dionex chromatography system equipped with an IC25 Ion Chromatograph, AS40 autosampler, a LC25 chromatography oven and an EG40 eluent generator. Anions were separated using a Dionex IonPac AS15 (3 × 150 mm) analytical column connected to a Dionex IonPac AG15 (3 × 50 mm) guard column. The oven was maintained at 30 °C and the flow rate was set at 0.35 mL/min. The KOH gradient generated by the EG40 eluent generator was as follows: 0–10 min, 5 mM; 10–16 min, gradient from 5 to 40 mM; 16–30 min, isocratic at 40 mM; 30–33, 40 mM to 5 mM; and a final isocratic run (33–40 min) at 5 mM.

The parameters of the ion chromatograph (ICS 3000, Dionex, Sunnyvale, CA, USA) are collected in Table 3. The IC was performed with an anion guard column (Dionex IonPac AG15), an anion separator column (Thermo Scientific, Dionex IonPac AS15 analytical), and pulsed amperometric detection.Table 3

Condition of IC-PAD analysis

Flow rate	1 cm3/min
Eluent	63 mM NaOH
Column temp.	30 °C
Tray temp.	10 °C
Inj. volume	10 mm3, full-loop injection
Electrodes	Reference: pH-Ag/AgCl electrode in AgCl mode
	Working: certified disposable Ag working electrode
Background	3–13 nC
Backpressure	≈110 psi
Noise	<7 psi
Run time	25 min

HPLC was performed on Gilson equipment (305 and 302 pumps) equipped with UV/VIS-151 and γ-ray NaI detectors connected in series and monitored by a GABI Star interface module (Raytest). Columns were for semi-preparative HPLC: Dionex Supelco Discovery C18, 5 μm, 250×10 mm; for analytical HPLC: MN, 150/4.6 Nucleosil 100-5 C18, 150 mm, ID: 4.6 mm and IonPac AS15, Dionex.