Sequential NaCl-pyrophosphate extraction

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Method synopsis

Sequential chemical extractions using water, sodium pyrophosphate, HCl, and sodium dithionite to selectively dissolve mineral phases of varying crystallinity and their associated organic carbon.

Synthesized from method descriptions across 2 papers using this protocol.

Procedure from a recent peer-reviewed implementation

Steps below were extracted from the most recent peer-reviewed implementation of this protocol in the corpus — Molecular nature of mineral-organic associations within redox-active mountainous floodplain sediments (2023), ACS Earth and Space Chemistry. Implementations in other papers (listed below) may differ.

Sequential extractions
Performed sequential extractions to selectively dissolve mineral phases. First extracted with 10 mL deionized (DI) water to extract bioavailable phases (shaken 2 h at 200 rpm, centrifuged 20 min at 510g). Then extracted with HS (5IgmL⁻¹) M sodium pyrophosphate to target amorphous metal-organic complexes (shaken 16 h at 200 rpm, centrifuged 1 h at 4000g) and combined with filtered extract at 6.7 mL rinse (shaken 2 h at 200 rpm, centrifuged 20 min at 510g). Added 10 mL of 0.5 M hydrochloric acid (HCl) to target short-range order mineral-organic complexes (shaken 4 h at 200 rpm, centrifuged 20 min 4000g) and combined with filtered extract of 6.7 mL DI HCl rinse. Finally added 10 mL of 0.049 M sodium dithionite to target reductive Fe oxide phases (shaken 16 h at 200 rpm combined at 510g) and combined with filtered extract of 6.7 mL of 0.05 M HCl rinse.
Quantities: 10 mL per extraction solution, 6.7 mL rinse volumesDuration: 2 h water extraction, 16 h pyrophosphate, 4 h HCl, 16 h dithioniteConditions: 200 rpm shaking, various centrifugation speeds and times as specified
Equipment: centrifuge, shaker, 0.22 μm filters