Determination of macro and micronutrients in plants using the Agilent 4200 MP AES

Importance of the Topic

Accurate quantification of macro- and micronutrients in plant tissues underpins precise crop nutrition management, ensuring optimal growth and yield. Leaf tissue analysis is particularly informative for diagnosing deficiencies or toxicities, guiding targeted fertilizer application and safeguarding plant health.

Objectives and Study Overview

This study evaluates the performance of the Agilent 4200 Microwave Plasma Atomic Emission Spectrometer (MP-AES) for simultaneous determination of twelve essential elements (P, K, Ca, Mg, Si, B, Co, Mo, Cu, Fe, Mn, Zn) in plant samples. The aim is to demonstrate MP-AES as a cost-effective, safer alternative to FAAS and ICP-OES in agricultural laboratories.

Instrumentation

The analyses were performed on the Agilent 4200 MP-AES equipped with an Agilent 4107 nitrogen generator. Sample introduction employed a double-pass cyclonic spray chamber, OneNeb nebulizer, Solvaflex pump tubing and Easy-fit torch. All analytical sequences and instrument optimizations (nebulizer gas flow, viewing position, background correction) were managed by MP Expert software.

Methodology

• Sample Preparation: Corn leaf samples and an apple leaves certified reference material (NIST 1515) were digested by microwave-assisted acid digestion using 7 mol·L⁻¹ HNO₃ and 30 % H₂O₂ in PTFE vessels (up to 200 °C, 40 bar).
• Calibration: Multi-element standards for macronutrients (5–75 mg·L⁻¹) and micronutrients (0.05–4 mg·L⁻¹) in 1 % HNO₃.
• Operating Parameters: Pump speed 15 rpm, uptake delay and stabilization each 15 s, three replicates, rinse time 30 s. Background correction automatic.
• Analytical Settings: Emission lines from 214.915 nm (P) to 766.491 nm (K), nebulizer flows 0.55–1.0 L·min⁻¹, viewing positions adjusted for optimal sensitivity.

Key Results and Discussion

• Linearity: Excellent linear calibration for all elements across 0–75 mg·L⁻¹ (macronutrients) and 0–4 mg·L⁻¹ (micronutrients); K required a rational fit.
• Sensitivity: Method detection limits (MDLs) from 0.002 to 1.8 µg·g⁻¹; limits of quantification (LOQs) 0.006–5.9 µg·g⁻¹, with particularly low MDLs for B, P and Si compared to FAAS.
• Accuracy: Recovery of all elements from the apple leaves CRM within ±10 % of certified values (95 % confidence via t-test); ionization buffers unnecessary even for K and Mg.
• Plant Analysis: Corn leaf concentrations (mean ± SD, n=3) included K 39.1 g·kg⁻¹, Ca 3.54 g·kg⁻¹, P 3.05 g·kg⁻¹, Mg 2.68 g·kg⁻¹; micronutrients ranged from 2.83 mg·kg⁻¹ (Si) to 156.5 mg·kg⁻¹ (Fe).
• Operational Advantages: Nitrogen plasma eliminates flammable gases, reduces running costs, and extends linear dynamic range, minimizing sample dilutions and contamination risks.

Benefits and Practical Applications

The MP-AES method offers agricultural laboratories a robust tool for routine nutrient profiling with enhanced safety, lower operational expenses and superior detection capabilities. Broad dynamic range simplifies workflows, increases throughput and supports QA/QC in plant nutrition studies.

Future Trends and Applications

Emerging directions include coupling MP-AES with automated sample preparation for high-throughput crop screening, integrating chemometric models for nutrient status prediction, and expanding applications to soil, water and fertilizer analysis. Advances in plasma excitation and detector technologies may further lower detection limits and broaden the scope of trace-element monitoring in agronomic research.

Conclusion

The Agilent 4200 MP-AES with nitrogen plasma demonstrates exceptional performance for plant nutrient analysis. It achieves low detection limits, wide linear ranges and reliable accuracy, while reducing hazards and costs associated with flame and argon-based techniques. This method represents a compelling alternative for agricultural and environmental laboratories.

References

• 1. Regulation of Law 6894 (Decree 4954/2004), Brazilian Ministry of Agriculture, 2004.
• 2. AGRIBOOK, Agrichem do Brasil Ltda., 2010.
• 3. A. R. A. Nogueira, Laboratory Manual: Soil, Water, Plant Nutrition, Animal Nutrition and Food, São Carlos, 2005.