Metrosep a supp 5 150 4

The ISO 10304–1 method¹² was used to quantify the concentration of NO₃⁻ and Cl⁻, including homogeneity and stability measurements. Specifically, an ion chromatograph (IC) (850 Professional, Metrohm, Switzerland) with a conductivity detector and polyvinyl alcohol/quaternary ammonium column (Metrosep A Supp 5-150/4.0, Metrohm, Switzerland) was used. Details about operating conditions used in the IC system are shown in Supplementary Table S3. Standard reference materials—SRM 3185 and SRM 3182—provided metrological traceability to these measurements.
The ISO 10523 method¹⁰ was used to perform the pH measurements, including homogeneity and stability measurements. Calibration of pH meter and uncertainty estimation were performed using a bracketing procedure as recommended by the IUPAC^{19 (link)}. All measurements were carried out at (25 ± 1) °C. A pH meter (781 pH/Ion digital, Metrohm, Switzerland) with automatic temperature compensation (ATC), an automatic stirring system (801, Metrohm, Switzerland) and a glass electrode with a Pt-1000 temperature sensor (Unitrode, Metrohm, Switzerland) were used to measure pH. The certified buffer solutions mentioned above provided metrological traceability.

To quantify cell growth, the optical density of each sample was measured at 680 nm using a UV-visible spectrophotometer (UV-1800; Shimadzu, Japan). Cell counts were performed using an optical microscope (DM2500; Leica, Switzerland) with a hemocytometer.
After the Cs removal experiments, the supernatant was filtered through a PVDF membrane filter (0.2 μm), and the amount of non-radioactive Cs⁺ remaining in the filtrate was quantified using inductively coupled plasma-mass spectrometry (ICP-MS; ELAN DRC II, Perkin-Elmer). Thus, the cellular uptake of Cs⁺ was determined by measuring the change in Cs⁺ concentration of the growth medium. The levels of K⁺ and Na⁺ were determined by ion chromatography (883 Basic IC plus; Metrohm AG, Switzerland) using an anionic column (Metrosep A Supp 5–150/4.0; Metrohm AG, Switzerland). The ¹³⁷Cs concentration was determined using γ-spectrometry (Canberra, Genie 2000).

A combustion ion chromatography (CIC) was used to analyze the EOF content in the samples. The instrument consisted of a combustion module (Analytik Jena, Germany), a 920 Absorber Module, and a 930 Compact IC Flex ion chromatograph (Metrohm, Switzerland). The ion exchange column was a Metrosep A Supp 5 – 150/4.0 (Metrohm, Switzerland), and the eluent was an isocratic elution using a carbonate buffer (64 mmol/L sodium carbonate and 20 mmol/L sodium bicarbonate, Sigma-Aldrich®, St. Louis, USA). Details of the instrumental analysis are provided in the ESM.