Dataset: Programmable Flow Injection (pFI) Silicate Vertical Profile Data from R/V Investigator IN2023_V04 in the Southern Ocean during June 2023 (pFI-SI-LOV project)

Unfiltered seawater samples were collected from the Niskin bottles in acid-washed plastic tubes. The stored samples were immediately analyzed for silicate in triplicate using the pFI assay protocol outlined in Hatta et al. (2021). One key modification was adjusting the holding coils’ temperatures to 25ºC instead of the originally specified 50ºC. In tandem with this temperature change, the stop flow time in the flow cell was extended to 60 seconds to ensure the absorbance of the silicomolybdenum blue at 810 and 660 nm product reached a steady state. 

We used a miniSIA-2 instrument (miniSIA2, GlobalFIA, Fox Island, USA) equipped with a 8-port LOV unit and a 20 cm flow cell furnished with a Tungsten Halogen light source and UV-VIS spectrophotometer (Ocean Insight, USA) and a 14 position auto sampler (GlobalFIA, USA). The entire system was controlled with FloZF software (v 5.2, GlobalFIA). The system was calibrated using silicate working standards prepared in low nutrient seawater (LNSW, (0-119 µmol L-1 Si)).