Ionpac as18 column

Batch
experiment samples (solids and aqueous) were analyzed both on-site
and at the University of Illinois Urbana–Champaign (UIUC).
Hand-held probes were used to measure pH (Orion 3-Star portable pH
meter; Thermo Scientific), temperature, DO (Orion RDO dissolved oxygen
probe; Thermo Scientific), and ammonium concentrations (ProDSS multiparameter
digital water quality meter; YSI); each sensor was calibrated immediately
prior to use in the bench-scale experiments. Solids storage and analyses
for TSS and VSS were performed as in Bradley et al.^{21 (link),22 (link),31 (link)−33} Briefly, sample TSS
was determined by filtration through 0.7 μm glass fiber filters
(Whatman GF/F). After filtration, the filters were heated at 105 °C
for 1 h and desiccated for 30 min prior to weighing. VSS was determined
by combusting samples for 20 min at 550 °C.
Samples for
phosphate, nitrate, and nitrite were immediately filtered through
0.22 μm filters and frozen. After storage, aqueous samples were
thawed and refiltered prior to analysis via ion chromatography (Dionex
ICS-2100 ion chromatograph, Dionex IonPac AS18 column; Section S2 and Figures S3–S5 for calibration
curves). The MRL for phosphate was determined to be 0.027 mg-P·L^–1 and the MRL range was 0.022 to 0.037 mg-P·L^–1 (Section S2 and Table S3).

Mineral soil layers from each core were air-dried for determination of nutrient concentrations and pH. To measure pH, we placed 5 g of soil in a 50 ml centrifuge tube with 25 ml of 0.01 M CaCl₂ and shook the mixture for 30 minutes. We let the mixture settle for two hours before using a Mettler Toledo Orion Dual Star to determine pH [20 (link)]. Soil cation and anions were determined by the method described by Quevauviller [21 ]. For this method, 2.5 g of soil into a centrifuge tube with 25 mL Milli-Q water and shaken for 3 hours at 15 rpm using a rotary shaker. Samples were then centrifuged at 5000 g for 10 minutes and subsequently filtered with a 0.45 μm filter. Afterwards, samples were analyzed for anions (Dionex IonPac AS18 column) and cations (Dionex IonPac CS12A column) with ion chromatography with a DionexICS-2000 using Chromeleon7 software in the Department of Soil Science of the University of Saskatchewan, Saskatoon, Saskatchewan, Canada.