Analysis of Liquid Fertilizer by ICPE-9820

Significance of the Topic

Liquid fertilizers supply essential nutrients beyond the primary N–P–K components, including micronutrients that directly influence crop health and yield. Accurate quantification of water-soluble metallic elements is critical for quality control, regulatory compliance and optimization of fertilizer formulations. Inductively coupled plasma atomic emission spectrometry (ICP-AES) offers high sensitivity and multi-element capability, making it a preferred technique for comprehensive fertilizer analysis.

Study Overview

This application note describes the simultaneous determination of eleven water-soluble elements in commercial liquid fertilizers using a Shimadzu ICPE-9820 ICP-AES. Analytical protocols follow the Food and Agricultural Materials Inspection Center (FAMIC) Testing Methods for Fertilizers. The aim was to establish reliable measurement conditions, suppress interferences, and demonstrate method performance across a wide concentration range.

Methodology and Instrumentation

Sample Preparation:

• Weighed 1 g of liquid fertilizer, diluted to 100 mL with ultrapure water, and filtered.
• Aliquot of the filtrate was spiked with yttrium internal standard and HCl, then diluted to 100 mL.

Instrument and Measurement Conditions:

• Instrument: Shimadzu ICPE-9820 simultaneous ICP-AES
• RF power: 1.2 kW; plasma gas: 10 L/min; auxiliary gas: 0.6 L/min; carrier gas: 0.7 L/min
• Nebulizer: standard; spray chamber: cyclone; torch: mini-torch
• Observation modes: axial (AX) for low-concentration elements, radial (RD) for high concentrations

Calibration and Interference Study:
Calibration curves for potassium in axial and radial views revealed self-absorption and ionization suppression in AX mode at high concentrations. Radial observation avoided these interferences, maintaining linearity. A mixed AX/RD approach enabled simultaneous analysis over four orders of magnitude without changing dilution factors.

Main Results and Discussion

Quantitative Results:
Eleven elements (B, Ca, Co, Cu, Fe, K, Mg, Mn, Mo, P, Zn) were measured in four fertilizer formulations. Concentrations ranged from sub-mg/L to tens of mg/L. Limits of quantitation met FAMIC requirements.

Method Validation:

• Dilution tests for high-content samples and spike-recovery tests for low-content samples yielded recoveries between 90 % and 110 %.
• No significant matrix interference observed when combining AX and RD observations.

The combined observation strategy provided robust, high-throughput multi-element analysis without sample pre-dilution adjustments.

Practical Benefits

Implementing this ICP-AES method streamlines fertilizer analysis by:

• Reducing analysis time via simultaneous multi-element detection.
• Ensuring compliance with official testing methods.
• Minimizing re-measurement by covering broad concentration ranges in a single run.

Quality control laboratories and fertilizer manufacturers can adopt this workflow to increase productivity and data reliability.

Future Trends and Potential Applications

Advances likely include integration of automated sample preparation, real-time interference correction algorithms, and coupling with chemometric data analysis for rapid fingerprinting of fertilizer batches. Emerging low-flow plasma sources and miniaturized ICP systems may enable on-site fertilizer monitoring. Further improvements in detection limits and matrix tolerance will expand analysis to trace contaminants and novel bio-stimulant components.

Conclusion

The Shimadzu ICPE-9820 enables reliable, simultaneous determination of water-soluble macro- and micronutrients in liquid fertilizers. By leveraging axial and radial observation modes, the method delivers linear calibration, robust interference suppression, and validated accuracy across a broad concentration spectrum. This approach enhances throughput and supports compliance with FAMIC standards.

Reference

1. Food and Agricultural Materials Inspection Center. Testing Methods for Fertilizers, 2019.
2. Aoyama K. Simultaneous Determination of Water-Soluble Principal Ingredients in Liquid Fertilizer using ICP-OES. FAMIC Research Report No. 8, 2015.