Ammonium, magnesium and calcium in liquid fertilizer

Significance of the topic

Accurate quantification of key nutrient cations in liquid fertilizers is essential for product quality control, optimal plant nutrition and environmental protection. The ability to rapidly determine ammonium, potassium, magnesium and calcium content supports precise formulation and regulatory compliance.

Objectives and study overview

This application note describes a cation chromatography method with direct conductivity detection for simultaneous determination of ammonium, potassium, magnesium and calcium in a commercial liquid fertilizer. The aim is to establish a fast, reliable, and low-maintenance analytical workflow.

Methodology and instrumentation

• Sample preparation: Dilution of liquid fertilizer at a ratio of 1 : 1000, no digestion required.
• Column: Metrosep C2 – 100 (6.1010.210).
• Eluent: 2.5 mmol/L nitric acid.
• Flow rate: 1.0 mL/min.
• Injection volume: 10 µL.
• Detection: Direct suppressed conductivity detection.

Main results and discussion

• Sodium was below the quantification limit and did not interfere with other cations.
• Excellent baseline separation of ammonium, potassium, magnesium and calcium within an 11-minute runtime.
• Quantified concentrations as weight percent: NH4–N 3.49%, K+ 3.42%, Mg2+ 0.81%, Ca2+ 0.13%.
• Chromatographic performance demonstrated high reproducibility and resolution suitable for routine analysis.

Benefits and practical applications

• Minimal sample handling with a simple dilution step speeds up workflow.
• Direct conductivity detection avoids reagent consumption associated with post-column derivatization.
• Method is robust and well suited for quality control in fertilizer production and research laboratories.

Future trends and possibilities

• Integration with automated sampling and inline monitoring to enable real‐time fertilizer quality control.
• Coupling cation chromatography with mass spectrometry for enhanced selectivity and detection of trace elements.
• Development of compact, field‐deployable IC systems for on‐site analysis at production facilities.

Conclusion

The described cation chromatography method provides a fast, precise and low-maintenance approach for determining essential nutrient cations in liquid fertilizers, fulfilling industrial QC requirements and supporting optimized fertilizer formulations.

References

• IC Application Note S-207: Determination of anions in liquid fertilizer.