Analysis of naphtha using the Thermo Scientific iCAP PRO XP Radial ICP-OES

Importance of the Topic

Trace element determination in naphtha is vital for the petrochemical industry. Impurities such as arsenic or sulfur compounds can poison cracking catalysts, reduce process efficiency and increase operational costs. Reliable quantification of trace metals ensures product quality, protects equipment and supports regulatory compliance.

Objectives and Study Overview

This study evaluates a direct analysis approach for volatile organic solvents using the Thermo Scientific iCAP PRO XP Radial ICP-OES coupled with a Peltier-cooled spray chamber. Key aims include:

• Demonstrating stable plasma operation with high-volatility samples.
• Achieving accurate quantification of trace elements at single‐digit μg·kg⁻¹ detection limits.
• Assessing method precision, recovery and robustness in a naphtha matrix.

Methodology

Samples and standards were prepared by diluting multi‐element oil standards and single‐element spikes in heavy naphtha. Calibration covered low and high concentration levels (1–5 mg·kg⁻¹) with blanks and spiked blanks. Method development involved:

• Setting the IsoMist spray chamber to –10 °C to suppress volatility and lower solvent load on plasma.
• Optimizing auxiliary and nebulizer gas flows while monitoring plasma shape with the Plasma TV feature.
• Selecting analytical wavelengths and background correction points via Qtegra ISDS software to minimize spectral interferences.

Used Instrumentation

The following equipment and settings were employed:

• Thermo Scientific iCAP PRO XP Radial ICP-OES with radial viewing mode.
• Glass Expansion IsoMist Peltier-cooled spray chamber set to –10 °C.
• Concentric glass nebulizer, pump speed 40 rpm, auxiliary gas 1.50 L·min⁻¹, nebulizer gas 0.45 L·min⁻¹, coolant gas 12 L·min⁻¹.
• RF power 1150 W, radial viewing height 10 mm, exposure time 10 s.

Main Results and Discussion

The method delivered excellent accuracy and precision in a challenging organic matrix:

• Spike recoveries for 24 elements fell within ±3 % of true values.
• Replicate precision (RSD) was below 0.7 % for most elements; boron showed higher variability due to matrix effects.
• Method detection limits ranged from 0.5 to 54 μg·kg⁻¹, depending on element and solvent purity.
• No significant plasma instabilities or excessive background emissions were observed under optimized conditions.

Benefits and Practical Applications

This approach offers several advantages for routine quality control and research:

• Direct analysis of volatile solvents without complex digestion or dilution.
• Reduced argon consumption due to full‐spectrum single‐run measurements.
• Fast method development aided by real‐time plasma imaging.
• High throughput with reliable quantification at trace levels.

Future Trends and Applications

Advancements and emerging uses may include:

• Integration with automated sample handling for inline refinery monitoring.
• Extension to other high‐volatility matrices such as biofuels and hydrocarbon blends.
• Implementation of machine‐learning algorithms for spectral deconvolution and drift correction.
• Development of even lower temperature spray chambers or hybrid desolvation systems to push detection limits further.

Conclusion

The Thermo Scientific iCAP PRO XP Radial ICP-OES paired with a Peltier-cooled spray chamber enables robust, accurate and precise trace element analysis in naphtha. By controlling volatility and optimizing plasma viewing, this method achieves single‐digit μg·kg⁻¹ detection limits, stable operation and high sample throughput, meeting the demands of petrochemical quality assurance.