Analysis of DTPA Extracted Soils per Chinese Standard HJ 804-2016

Significance of the Topic

The accurate assessment of bioavailable nutrients and trace metals in soil is critical for crop management, environmental monitoring and pollution control. The DTPA extraction method isolates the fraction of elements that can be taken up by plants, providing insight into soil fertility and potential toxic metal exposure.

Objectives and Study Overview

This work evaluates the performance of the Agilent 5800 Vertical Dual View ICP-OES system for determining eight bioavailable elements (Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn) in DTPA-extracted soils according to Chinese National Standard HJ 804-2016. The study aims to streamline method development, ensure data quality and demonstrate long-term analytical stability.

Methodology and Instrumentation

The procedure follows the HJ 804 protocol:

• Dry and sieve soil through a 2 mm mesh
• Weigh 10 g of soil and add 20 mL of DTPA extraction solution (1 g/L DTPA, 2 g/L CaCl₂·2H₂O, 10 g/L TEA, pH adjusted to 7.3)
• Shake for 2 h and centrifuge for 10 min
• Filter the supernatant for analysis

Instrumentation

The analysis employed an Agilent 5800 VDV ICP-OES equipped with:

• SeaSpray nebulizer and double-pass cyclonic spray chamber
• Demountable DV 1.8 mm injector torch
• Advanced Valve System AVS 6 switching valve
• SPS 4 autosampler for automated sample delivery
• ICP Expert software featuring IntelliQuant, IntelliQuant Screening and Fitted Background Correction

Main Results and Discussion

Key performance metrics:

• Calibration linearity exceeded 0.99995 with RSE ≤ 5 %
• Method detection limits ranged from 0.28 to 4.17 µg/kg in the soil sample
• Low-level spike recoveries in the blank DTPA solution were between 93 % and 107 %
• Soil spike recoveries fell within ± 10 % for all elements
• Long-term stability over six hours (210 samples plus 22 QC) showed QC recoveries within ± 10 % and RSD < 3.5 %
• IntelliQuant Screening wavelengths matched the regulated lines and semiquantitative results agreed within ± 25 % of the full quantitative analysis

Benefits and Practical Applications

The combined workflow offers:

• Rapid method development with automatic wavelength selection
• Reduced sample remeasurements and increased confidence using smart software tools
• High sample throughput with minimal downtime thanks to AVS 6 and autosampler integration
• Accurate trace-level detection and robust matrix correction via Fitted Background Correction

Future Trends and Opportunities

Potential advancements include:

• Expansion of semiquantitative screening to more elements for broader sample characterization
• Integration of machine learning algorithms to predict interferences in complex matrices
• Development of automated calibration routines and remote instrument monitoring
• Application of portable ICP-OES systems for field-based soil analysis

Conclusion

The Agilent 5800 VDV ICP-OES with AVS 6 and advanced software tools delivers reliable, high-throughput analysis of eight bioavailable soil elements per Chinese Standard HJ 804-2016. The platform’s accuracy, stability and smart features make it well suited for routine environmental and agricultural laboratories.

Reference

1. Soil Determination of bioavailable form of eight elements Extraction with buffered DTPA solution Inductively coupled plasma optical emission spectrometry HJ 804 The Standardization Administration of the People’s Republic of China 2016
2. Agilent IntelliQuant Software Agilent publication 5994-1516EN
3. Agilent IntelliQuant Screening Agilent publication 5994-1518EN
4. Technical Overview Fitted Background Correction FBC Fast accurate and fully automated background correction Agilent publication 5991-4836EN