Determination of Chloride in Crude Oils using an Agilent 8900 ICP-QQQ

Significance of Topic

Chloride in crude oil can induce corrosion and fouling in refinery equipment. Maintaining chloride levels below 1 mg/L is essential for safe and efficient distillation and to extend equipment lifespan.

Objectives and Study Overview

This work aimed to establish a rapid and accurate method for determining chloride in crude oils by direct dilution in an o-xylene based diluent using an Agilent 8900 ICP-QQQ. The method was validated with a NIST fuel oil reference material and compared against Instrumental Neutron Activation Analysis (INAA).

Methodology and Instrumentation

• Sample Preparation: Crude oils diluted 1:5 or 1:10 in a diluent of 90% o-xylene and 10% mineral oil modifier with dispersant and internal standards (Sc and Y at 0.1 mg/kg).
• Calibration: Organic chloride standards in the range 1–1000 mg/kg; blank runs with diluent and modifier.
• ICP-QQQ Conditions: Agilent 8900 with platinum cones, concentric glass nebulizer, quartz spray chamber and torch; H2 cell gas for mass-shift of 35Cl to 37Cl as ClH2+; RF power 1500 W, nebulizer flow 0.4 L/min, H2 flow 4.6 mL/min.
• Interference Control: MS/MS mode to remove 16O18O H and 34S H polyatomic overlaps.
• Comparison Technique: INAA performed by an external facility.

Main Results and Discussion

• Analytical Performance: Detection limit of 0.01 mg/kg, LOQ of 0.04 mg/kg and background equivalent concentration of 0.24 mg/kg for 35Cl.
• SRM Recovery: 99% at 1:5 dilution and 107% at 1:10 dilution versus the 45 mg/kg reference.
• Crude Oil Analysis: Twelve samples with sulfur 0.38–2.01 wt% and H/C ratios 1.68–1.88 yielded chloride levels between 6 and 50 mg/kg.
• INAA Comparison: Agreement from 89% to 134%, with sample heterogeneity and incomplete dissolution cited for discrepancies.

Benefits and Practical Applications

• Fast, sensitive chloride determination in complex petroleum matrices.
• Effective interference removal using H2 mass-shift in MS/MS mode.
• Direct dilution reduces acid consumption and simplifies sample handling.
• Applicable for routine QA/QC and corrosion monitoring in refineries.

Future Trends and Opportunities

• Extension to other halogens and trace elements in petroleum by ICP-QQQ.
• Automated dilution and flow injection for higher sample throughput.
• Integration with multivariate analysis for crude oil fingerprinting and source tracking.
• Development of portable or miniaturized triple-quadrupole ICP systems for field analysis.

Conclusion

The Agilent 8900 ICP-QQQ method with H2 mass-shift enables accurate, low-level chloride measurement in crude oils via direct dilution. The approach delivers high recoveries, low detection limits, and robust interference control, supporting refinery quality control and corrosion risk assessment.

References

1. Nelson J, Poirier L, Lopez-Linares F. Determination of Chloride in Crude Oils by Direct Dilution using Inductively Coupled Plasma Tandem Mass Spectrometry (ICP-MS/MS). J Anal At Spectrom. 2019; DOI 10.1039/C9JA00096H.
2. ASTM D8110-17. Standard Test Method for Elemental Analysis of Distillate Products by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). ASTM Int. 2017.
3. Agilent Technologies. Handbook of ICP-QQQ Applications using the Agilent 8800 and 8900. Publication 5991-2802EN.
4. Sugiyama N. Trace level analysis of sulfur, phosphorus, silicon and chlorine in NMP using the Agilent 8800 Triple Quadrupole ICP-MS. Agilent 5991-2303EN.
5. Nakano K. Ultra low-level determination of phosphorus, sulfur, silicon, and chlorine using the Agilent 8900 ICP-QQQ. Agilent 5991-6852EN.
6. Doyle A, Saavedra A, Tristao MLB, Nele M, Aucelio RQ. Direct chlorine determination in crude oils by energy dispersive X-ray fluorescence spectrometry: An improved method based on a proper strategy for sample homogenization and calibration with inorganic standards. Spectrochim Acta B. 2011;66:368–372.