Halogens in palm oil production applying Metrohm Combustion IC

Significance of the topic

Palm oil is one of the most widely used vegetable oils in food, cosmetics and biodiesel production. Monitoring halogen and sulfur levels ensures product safety, regulatory compliance and minimal corrosive by-products during processing.

Objectives and study overview

This study evaluates a robust workflow to quantify chlorine and sulfur in crude, washed and fully refined palm oil by combustion ion chromatography (Combustion IC). The goal is to demonstrate method precision, sensitivity and suitability for quality control in palm oil processing.

Methodology and instrumentation

The approach couples high-temperature combustion with ion chromatography using flame sensor technology and intelligent Partial Loop Injection Technique (MiPT) with inline matrix elimination. Oil samples are directly introduced into a combustion module where halogens and sulfur species are converted to ionic forms and captured in a hydrogen peroxide absorber solution. An IC system equipped with sequential suppression and conductivity detection separates and quantifies the target ions.

Instrumentation used

• 930 Compact IC Flex with Oven/SeS/PP/Deg module
• IC Conductivity Detector
• MSM Rotor A and Adapter sleeve for Suppressor Vario
• 920 Absorber Module
• Combustion Module (oven and ABD)
• Autosampler MMS 5000 with solid sampling kit

Analytical parameters

• Eluent: 3.2 mmol/L sodium carbonate, 1.0 mmol/L sodium hydrogen carbonate
• Suppressor regenerant: 100 mmol/L sulfuric acid
• Absorber solution: 100 mg/L hydrogen peroxide
• Flow rate: 0.7 mL/min; Injection volume: 100 µL (MiPT); Column temperature: 30 °C; Total run time: 18 min
• Combustion gases: Argon 100 mL/min, Oxygen 300 mL/min; Oven temperature: 1050 °C; Post-combustion time: 120 s

Main results and discussion

Chlorine and sulfur concentrations decrease progressively with refining stages:

• Crude palm oil: Cl 7.5 mg/kg, S 4.1 mg/kg
• Washed palm oil: Cl 3.1 mg/kg, S 2.7 mg/kg
• Fully refined palm oil: Cl 1.8 mg/kg, S 1.5 mg/kg

Nitrite and nitrate were below quantification limits. The data confirm that standard refining reduces halogen and sulfur impurities effectively. The high combustion temperature and efficient absorber system yield stable baselines and reproducible peaks.

Practical benefits and applications

The described Combustion IC protocol offers:

• Minimal sample preparation and direct solid/liquid sampling
• High sensitivity for trace-level halogens and sulfur
• Automated workflow suitable for routine quality control
• Reduced matrix interference via inline elimination

It supports compliance with food safety regulations and optimizes refining processes.

Future trends and applications

Advances may include coupling combustion IC with mass spectrometric detection for speciation of halogenated organics, further miniaturization of sampling modules, and development of greener absorbents. Expanding the method to other edible oils, biodiesel feedstocks and environmental samples will broaden its impact.

Conclusion

Combustion ion chromatography provides a reliable and automatable solution for quantifying chlorine and sulfur in palm oil. The method demonstrates excellent sensitivity, accuracy and throughput across different refining stages, making it a valuable tool for quality assurance and process optimization.

Reference

Metrohm Application Note CIC–019: Halogens in palm oil production applying Metrohm Combustion IC.