Simultaneous Analyses of Anions and Cations in Nutrient Solution Used for Hydroponic Cultivation and in Its Dilution Water (Source Water) Using the Nexera IC Ion Chromatograph

Significance of the topic

Ion composition control in hydroponic systems is critical for plant health and yield. Routine monitoring that goes beyond bulk parameters such as pH and electrical conductivity (EC) is required to identify imbalances of individual nutrients (anions and cations) that cause poor growth or deficiencies. Ion chromatography (IC) enables simultaneous, quantitative profiling of multiple anions and cations in nutrient solutions and in the source (dilution) water, providing actionable information for fertilization strategy and water-quality assessment.

Objectives and study overview

The study demonstrates simultaneous analysis of five anions (Cl−, NO2−, NO3−, PO43−, SO42−) and five cations (Na+, NH4+, K+, Mg2+, Ca2+) in hydroponic nutrient solution and source tap water using the Nexera IC dual-analysis system. Goals included validating linearity and repeatability, showing a dual-path approach with independently adjustable injection volumes, and illustrating how ion profiles inform nutrient management in hydroponics.

Methodology

Ultrapure-water and tap-water samples were prepared as follows:

• Source water: tap water filtered through a 0.2 µm syringe filter prior to analysis.
• Nutrient solution: commercial liquid fertilizer diluted 500-fold with tap water (as per manufacturer); an aliquot of the prepared nutrient solution was further diluted 10-fold with ultrapure water for analysis (reported concentrations were back-calculated by a conversion factor of 10).

Calibration and quantitation:

• Five-level calibration curves were constructed for each ion; coefficients of determination (r2) were ≥0.999 for all ions, indicating excellent linearity across the tested ranges.
• Sample injection used loop injection (partial-loop mode chosen to allow differing injection volumes adapted to ion concentration ranges).
• Repeatability: peak-area repeatability assessed with six consecutive injections (n=6) showed %RSD typically ≤0.5%.

Used instrumentation

The dual-path Nexera IC system configuration and principal consumables included (key elements summarized):

• Anion path: Shim-pack IC-C4 column (150 mm × 4.6 mm I.D., 7 µm) with guard column; mobile phase 2.5 mmol/L methanesulfonic acid; flow 1.0 mL/min; column temperature 40 °C; typical injection volume 25 µL (partial-loop); conductivity detection.
• Cation path: Shim-pack IC-SA2 column (250 mm × 4.0 mm I.D., 9 µm) with guard; ICDS-Ai suppressor; mobile phase: 1.8 mmol/L sodium carbonate + 1.7 mmol/L sodium hydrogen carbonate; flow 1.0 mL/min; column temperature 30 °C; injection volume 10 µL (partial-loop); conductivity detection.
• System components: two pumps, two column ovens, two injection valves, autosampler, suppressors (ICDS-Ai), conductivity detectors, and degassing unit. Shimadzu PP vials (1.5 mL) and 0.2 µm syringe filters for sample prep were used.

Main results and discussion

Calibration and analytical performance:

• All ten target ions showed linear response with r2 ≥ 0.999 over instrument-appropriate concentration ranges (five calibration levels).
• Partial-loop injection enabled setting different injection volumes for the anion and cation flow paths to accommodate disparate concentration ranges and preserve peak shape.
• Repeatability (n=6) was excellent (peak-area %RSD generally ≤0.5%).

Representative quantitative results (average concentrations, mg/L; n=6; nutrient-solution values reported as equivalent to non-diluted nutrient solution by applying the dilution/conversion factor):

• Tap water: Cl 6.5; NO2 not detected; NO3 3.9; PO4 not detected; SO4 16.2; Na 7.8; NH4 not detected; K 1.5; Mg 4.3; Ca 15.4.
• Nutrient solution: Cl 7.7; NO2 not detected; NO3 437.7; PO4 105.6; SO4 70.3; Na 9.1; NH4 7.4; K 172.2; Mg 21.6; Ca 79.3.

Interpretation:

• Nitrate and potassium dominated the nutrient solution composition, while tap water contributed significant calcium and sulfate (Ca ~15.4 mg/L; SO4 ~16.2 mg/L). These source-water contributions affect initial nutrient balance and should be accounted for when formulating or adjusting fertilizers.
• Nitrite was not detected in the tested samples; however, the method is suitable to monitor nitrite because accumulation can negatively affect plants and may occur depending on source water or system conditions.

Benefits and practical applications

The dual-path IC approach provides several practical advantages for hydroponic nutrient management:

• Simultaneous measurement of anions and cations with consolidated data storage simplifies workflows and reduces analysis time versus separate runs.
• Independent injection-volume control per flow path enables optimization for ions that span wide concentration ranges (e.g., very high NO3− vs. lower Na+), improving quantitative accuracy and peak shapes without sacrificing sensitivity.
• High linearity and repeatability support reliable monitoring for QC, routine nutrient audits, fertilizer design reviews, and decision-making on nutrient replenishment timing.
• Joint analysis of source water and nutrient solution allows attribution of observed ion levels to either the fertilizer or the dilution water, improving fertilization strategies.

Future trends and potential applications

Potential directions that extend the presented approach include:

• Integration of on-line or at-line sampling for near-real-time monitoring of nutrient solution dynamics and automated dosing control.
• Miniaturization and coupling to flow-through sensors for continuous EC/ion-specific monitoring while preserving the selective quantitation offered by IC as a reference method.
• Advanced data analytics and chemometric models to link temporal ion profiles with crop performance, enabling predictive fertilization and early detection of imbalances.
• Method adaptation for broader environmental source waters (surface, groundwater) and incorporation of additional analytes (organic acids, trace anions/cations) relevant to plant health.

Conclusion

The Nexera IC dual-analysis configuration enables robust, simultaneous quantitation of key anions and cations in hydroponic nutrient solutions and source water with high linearity and repeatability. By allowing independent optimization of injection volumes for each flow path, the system handles wide concentration ranges across ion classes, delivering detailed compositional information that EC and pH alone cannot provide. Routine IC-based monitoring supports improved fertilization strategies, source-water assessment, and preventative management in hydroponic cultivation.

Reference

• Hayakawa M. Simultaneous Analyses of Anions and Cations in Nutrient Solution Used for Hydroponic Cultivation and in Its Dilution Water Using the Nexera IC Ion Chromatograph. Shimadzu Application News, First Edition Sep. 2026.