Determination of Sulfur in Fertilizers

Importance of the Topic

Sulfur is essential in plant growth supporting protein synthesis enzyme formation and coenzyme function. Reduced sulfur deposition in soils due to stricter emission regulations has increased the need for fertilizer supplementation to correct deficiencies that cause stunted growth chlorosis delayed maturity and yield loss.

Objectives and Overview of the Study

This work presents a validated procedure for quantifying total sulfur in commercial fertilizers. Following AOAC First Action Method 2017.08 it aims to deliver accurate reproducibility and traceability suitable for quality control regulatory compliance and guaranteed value labeling of fertilizer products.

Methodology

The protocol uses high temperature combustion at 1350 °C in an oxygen atmosphere within the LECO S832DR. Sulfur in the sample is converted to sulfur dioxide which passes through a halogen trap assembly to remove interferences before detection. Key steps include instrument blank determination calibration with concentration matched reference materials and replicate sample analysis for drift correction.

Used Instrumentation

• LECO S832DR high temperature combustion sulfur analyzer
• Ceramic crucibles (Part 528-203)
• Combustion catalyst Com-Cat (Part 502-321)
• Halogen trap components including antimony metal scrubbers and F-Cl absorbent

Main Results and Discussion

Analysis of diverse fertilizer matrices covering sulfur concentrations from below 1 up to over 80 percent demonstrates linear calibration across defined concentration ranges with at least five calibration points. Typical replicate precision yielded relative standard deviations below 0.5 percent and results matched expected values for ammonium sulfate elemental sulfur and blended fertilizers, confirming method accuracy and robustness.

Benefits and Practical Applications

This robust combustion technique provides rapid reliable determination of total sulfur for fertilizer blending validation product labeling agronomic recommendation and regulatory reporting. Its high throughput capability and minimal matrix interference support industrial quality assurance and batch release workflows.

Future Trends and Potential Uses

Future developments may include enhanced automation for unattended operation miniaturized combustion modules and integration of alternative detection principles such as infrared or ultraviolet spectroscopy. Coupling with chemometric algorithms could streamline calibration and expand the approach to simultaneous multi-element analysis.

Conclusion

The high temperature combustion method on the LECO S832DR offers a precise accurate and practical solution for total sulfur determination in fertilizers. It meets AOAC performance criteria and ensures consistent product quality agronomic efficacy and regulatory compliance.

Reference

• AOAC First Action Method 2017.08 Total Sulfur in Fertilizer by High Temperature Combustion