Trace chloride in wax fraction of crude oil distillation applying Metrohm Combustion IC

Significance of the topic

The wax fraction obtained from crude oil distillation serves as a source for paraffin wax and high‐performance lubricating oils. Controlling trace chloride levels in these products is essential to prevent corrosion, maintain product stability, and meet industry quality standards.

Objectives and study overview

This application note demonstrates a reliable approach to measure trace chloride in wax fractions through inline combustion combined with ion chromatography. Although sulfur determination was not the primary focus, the setup also enables sulfur quantification when needed.

Methodology

Samples were analyzed using a combustion ion chromatography workflow with flame sensor detection and intelligent Partial Loop Injection Technique (MiPT). Inline matrix elimination simplifies sample preparation by combusting the hydrocarbon matrix at high temperature and absorbing combustion products in aqueous solution. Chromatographic separation employs a carbonate/hydroxide eluent with sequential suppression.

Used instrumentation

• Metrohm 930 Compact IC Flex with Combustion Module (oven and ABD)
• IC Conductivity Detector
• MSM Rotor A for sample introduction
• 920 Absorber Module
• Autosampler MMS 5000 with solid sampling kit
• Columns: Metrosep A Supp 16, A Supp 16 Guard, and A PCC 1 HC

Main results and discussion

Trace chloride was determined in three replicate measurements, yielding an average concentration of 0.57 mg/kg with a relative standard deviation of 9.8 percent. Sulfur remained below the quantification limit under the chosen conditions. The precision and sensitivity demonstrated that the combustion IC approach is well suited for low-level halogen analysis in complex hydrocarbon matrices.

Benefits and practical applications

• High sensitivity for chloride detection at sub‐milligram per kilogram levels
• Minimal sample preparation through direct combustion and inline absorption
• Capability to measure additional elements such as sulfur without hardware changes
• Improved laboratory workflow and reduced risk of contamination

Future trends and potential applications

Advances in sensor technology and automation will further streamline trace halogen analysis. Potential developments include multi‐element detection in a single run, real‐time process monitoring in refineries, and expanded applications in environmental analysis of chlorinated pollutants.

Conclusion

Combustion ion chromatography provides a robust, precise, and sensitive method for monitoring trace chloride in wax fractions from crude oil distillation. Integration of sample combustion with IC detection ensures reliable quality control for paraffin wax and lubricating oil production.

References

• IC Application Note CIC–014, Metrohm