Determination of available micronutrients in DTPA extracted soils using the Agilent 4210 MP-AES

Importance of the Topic

Assessing available micronutrients in agricultural soils is essential for optimizing plant health and crop yields. Micronutrient deficiencies or toxicities can limit productivity and affect food safety. Reliable measurement of trace elements such as copper, iron, manganese and zinc ensures informed soil management and sustainable agricultural practices.

Study Objectives and Overview

This application note evaluates the performance of the Agilent 4210 MP-AES for quantifying Cu, Fe, Mn and Zn in DTPA-extracted soils. The goal is to demonstrate that microwave plasma atomic emission spectroscopy provides a cost-effective, safe and accurate alternative to FAAS and ICP-OES in routine soil micronutrient analysis.

Instrumentation Used

• Agilent 4210 MP-AES with integrated humidifier accessory
• SPS 4 autosampler
• OneNeb Series 2 nebulizer
• Double-pass glass cyclonic spray chamber
• Easy-fit torch
• Wavelength settings: Cu 324.754 nm, Fe 259.940 nm, Mn 257.610 nm, Zn 213.857 nm

Methodology

DTPA extraction solution was prepared by dissolving 1.97 g DTPA, 1.47 g CaCl₂·2H₂O and 13.3 mL TEA in water, adjusting to pH 7.3 and diluting to 1 L. Ten grams of dried, ground soil were shaken with 20 mL extractant for 120 minutes and filtered. Calibration standards (0.5–5 µg/mL for Cu and Zn; 5–50 µg/mL for Mn; 25–100 µg/mL for Fe) were prepared in the same matrix. Instrument parameters included a nebulizer flow of 0.75 L/min, pump rate 15 rpm, read time 3 s, stabilization 10 s and rinse 20 s.

Main Results and Discussion

Calibration curves for all elements exhibited coefficients ≥0.999 with <10% error at each point. Method detection limits ranged from 0.03 mg/kg (Fe, Mn) to 0.06 mg/kg (Cu). Spike recoveries (90–92%) at multiple levels confirmed accuracy. Long-term stability over 3 hours showed precision better than 2% RSD for all analytes, demonstrating robust performance under continuous operation.

Method Benefits and Practical Applications

• Eliminates flammable gases by using nitrogen-based plasma, reducing cost and safety risks
• High matrix tolerance supports analysis of complex soil extracts
• Multi-element capability accelerates throughput
• Low detection limits and wide calibration range improve sensitivity
• Automated software and plug-and-play hardware simplify routine use

Future Trends and Opportunities

Integration of MP-AES with automated soil testing workflows can enhance field-to-lab analytics. Coupling with data management platforms and machine-learning models may enable predictive soil health monitoring. Portable plasma systems could bring rapid micronutrient profiling to on-site agricultural assessments.

Conclusion

The Agilent 4210 MP-AES method delivers high accuracy, stability and safety for DTPA soil micronutrient analysis. Its low operating cost and robust performance make it an attractive alternative to traditional FAAS and ICP-OES techniques.

Reference

• Kulikov E. Determination of available micronutrients in DTPA extracted soils using the Agilent 4210 MP-AES. Agilent Technologies Application Note. Publication 5991-7250EN, 2016.