Combining full spectrum read-out and innovative automation capabilities for the robust and fast analysis of major and trace elements in fertilizers using ICP-OES

Importance of the topic

Fertilizer analysis is essential to verify the presence of key macro- and micronutrients and to identify potentially harmful elements that can accumulate in the food chain. Regulatory frameworks such as EU Regulation 2019/1009 set strict limits for inorganic contaminants in fertilizers. High-throughput, accurate and robust analytical methods are required in testing laboratories to meet these requirements and cope with seasonal variations in sample load.

Goals and study overview

This study demonstrates the capabilities of the Thermo Scientific iCAP PRO XP ICP-OES Duo paired with the iSC-65 Autosampler for a rapid and reliable multielement analysis of solid and liquid fertilizers. The main objectives were:

• To develop a single-mode ICP-OES method that measures major and trace elements in less than 40 seconds per sample.
• To validate sensitivity, accuracy, linearity and robustness against EU Regulation 2019/1009 limits.
• To compare performance with a standard reference material and real fertilizer samples.

Methodology and instrumental setup

Samples (commercial solid and liquid fertilizers and NIST SRM 695) were mineralized by closed‐vessel microwave digestion in HNO₃/HCl. Analysis was carried out on the iCAP PRO XP ICP-OES Duo in radial intelligent Full Range (iFR) mode covering 167–852 nm in a single exposure. The iSC-65 Autosampler employed the Step Ahead feature to overlap probe rinse with data acquisition, reducing cycle time.

Instrumental setup

• ICP-OES: iCAP PRO XP Duo, radial iFR mode, 5 s exposure, 3 replicates
• Autosampler: iSC-65 with Step Ahead timing (36 s per sample including uptake, acquisition, wash)
• Sample introduction: glass cyclonic spray chamber, concentric nebulizer, EMT glass torch, quartz 2.0 mm injector
• Gas flows: nebulizer 0.65 L/min, auxiliary 0.50 L/min, coolant 12.5 L/min
• RF power 1 150 W, pump speed 45 rpm data/125 rpm fast uptake
• Internal standard: Sc at 10 mg/kg added online

Main results and discussion

Linearity across trace (0.01–5 mg/L) and major element ranges (up to 1 500 mg/L) yielded R²>0.999. Instrument detection limits (ID​L) translated to method LOQs below regulatory thresholds (µg/kg levels with dilution factor 100).

Accuracy assessed by recovery in SRM 695 (n=3) ranged from 86.7% to 101.4%. Spike recoveries at regulatory limits in a simulated matrix were 90.4%–106.7%.

Robustness was demonstrated by continuous analysis of over 500 samples in 5.6 hours with internal standard recoveries of 86–110% and QC checks within 80–120%.

Analysis of real fertilizer samples showed major constituents (K, Ca, Na, S) at percent levels and trace contaminants (Cr, Cd) below permitted limits.

Benefits and practical applications

• High throughput: 36 s sample cycle without additional sampling valves, improving daily productivity.
• Regulatory compliance: achieves required LOQs for As, Cd, Cr, Hg, Ni, Pb under EU standards.
• Simplified operation: single-mode radial iFR acquisition avoids mode switching and reduces analysis time by over 50%.
• Cost efficiency: no need for discrete sampling valves or dual-mode configurations.

Future trends and applications

The single-mode, full-spectrum ICP-OES approach can be extended to soil, plant and wastewater analysis. Further integration with ICP-MS systems and advanced autosampler automation will enhance sensitivity for ultra-trace determinations and streamline laboratory workflows.

Conclusion

The combined iCAP PRO XP ICP-OES Duo and iSC-65 Autosampler method delivers a rapid, robust and accurate multielement analysis of fertilizers. Continuous operation with high recovery and low detection limits meets stringent regulatory requirements while maximizing laboratory efficiency.

References

1. Regulation (EU) 2019/1009 of the European Parliament and of the Council of 5 June 2019 laying down rules on the making available on the market of EU fertilizing products.
2. Analyte Guru blog post: How to increase your elemental analysis lab’s productivity—fast, Thermo Fisher Scientific.