Crude Oil Testing

Machado, Eduarda Q., et al. Microchemical Journal (2025): 112988.

Trace metal analysis in crude oil is essential for monitoring contamination, refining efficiency, and catalyst poisoning. This study demonstrates a minimalist approach using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) with filter paper as a solid support for determining nickel (Ni) and vanadium (V) in crude oil samples.

Aliquots (4 µL) of aqueous standards and crude oil samples were deposited on filter paper and dried at 37 °C, eliminating the need for extensive sample preparation. Three calibration curves (0.5–30 mg/kg) were evaluated using oil-based and aqueous standards, with or without 13C internal standard normalization. The best accuracy was achieved with an aqueous calibration curve without normalization, aligning well with traditional microwave digestion and ICP-MS methods.

The optimized ablation conditions included a 110 µm spot size, 110 µm/s scan speed, and 60% laser intensity, while ICP-MS parameters used 1.2 L/min nebulizer gas, 1.6 L/min auxiliary gas, and 1200 W plasma power. The results were within the 80–120% accuracy range, demonstrating method reliability.

This cost-effective and rapid approach offers an alternative to conventional digestion techniques, reducing reagent use and analysis time. The developed LA-ICP-MS method ensures accurate detection of Ni and V in crude oil, supporting environmental monitoring, quality control, and regulatory compliance in petroleum industries.

Mandlate, Jaime S., et al. Analytica Chimica Acta 1273 (2023): 341536.

The accurate determination of chlorine (Cl) and sulfur (S) in crude oil is critical for refining efficiency, environmental compliance, and corrosion prevention. A novel microwave-induced combustion in disposable vessels (MIC-DV) method was developed for rapid and safe digestion of crude oil, followed by ICP-OES analysis.

In this approach, crude oil samples were pipetted onto filter paper disks and ignited using NH₄NO₃ within disposable polypropylene vessels. The combustion occurred under atmospheric pressure in a domestic microwave oven, ensuring operator safety. The digested products were absorbed in 2.5 mL ultrapure water, allowing for direct elemental analysis.

Key optimizations included sample mass (up to 10 mg per cycle), absorbing solution composition, and multiple combustion cycles (up to five cycles, reaching a total of 50 mg per sample). The method demonstrated high accuracy, with recovery rates of 99–101% for Cl and 95–97% for S. The limits of quantification (LOQ) for Cl and S were 73 and 50 µg/g, respectively, enabling precise trace-level detection.

Validated according to Eurachem Guide recommendations, MIC-DV offers a fast, cost-effective, and environmentally friendly alternative to conventional digestion methods. The ability to process multiple samples with minimal reagent consumption makes this approach highly beneficial for petroleum laboratories engaged in crude oil quality control and regulatory compliance.

Silva, Felipe A., et al. Talanta 257 (2023): 124297.

The quantitative determination of sodium (Na), potassium (K), calcium (Ca), and magnesium (Mg) in crude oil is essential for assessing refining efficiency and preventing equipment corrosion. A novel miniaturized liquid-liquid extraction (LLE) method, followed by flame atomic absorption spectrometry (FAAS), was developed for rapid and efficient elemental analysis.

Key experimental parameters—including extraction solution composition, sample mass (2.5 g), heating (80°C for 10 min), stirring (60 s), and centrifugation (10 min)—were optimized to achieve maximum analyte recovery. The addition of a chemical demulsifier (50 mg L^-1 in toluene) ensured efficient phase separation. The method demonstrated excellent accuracy, with results statistically equivalent to high-pressure microwave-assisted digestion (reference method) and relative standard deviations below 6%.

The limits of quantification (LOQs) for Na, K, Ca, and Mg were 1.2, 1.5, 5.0, and 0.50 µg/g, respectively, meeting industrial requirements for trace metal detection. Notably, the miniaturized LLE approach reduced reagent consumption by 40 times, enhancing environmental sustainability. Additionally, up to 10 samples could be processed per hour, offering a high-throughput and cost-effective alternative to conventional methods.

This low-cost, simplified sample preparation method eliminates the need for expensive instrumentation such as microwave digestion systems, making it ideal for routine crude oil quality control in industrial and research laboratories.