Determination of Polycyclic Aromatic Hydrocarbons in Biodiesel Exhaust from Jatropha curcas and Chlorella variabilis by Gas Chromatography with Flame Ionization Detection

Application of high-performance liquid chromatography in determining saturates and aromatic hydrocarbons along with polars/additives in automotive finished and used lubricating oils

Lubricating oils help an internal combustion engine function effectively by reducing friction and wear on the engine's moving parts. They typically consist of petroleum-derived base oil and various additives to achieve the desired characteristics in automotive engine oils. Determination of aromatics and polar additives in the finished and used lubricating oils is not possible with existing methods hence their development is significant from the perspectives of environment and reuse/re-refining of used lubricating oils. This study reports the development of a new HPLC method to determine additives in the finished lubricating oils and/or polars in the used engine oils. The proposed method is simple, fast (runtime of 13 min), does not require sample pre-treatment, and exhibits high precision and superior limits of detection and quantification. The method demonstrated good linear response ranging from 0.1 to 30 mass for total aromatics and 0.1 to 20 % for additives. The method validation was carried out by analyzing brand-new commercial two and four-wheeler lubricants with used automotive lubricants. Based on the proposed method, the aromatics and additives concentration ranges in the studied finished lubricants were estimated between 0.20-1.70 % (mass) and 0.20-3.50 % (mass), respectively. Similarly, for used lubricants, the aromatics and additives were estimated to be 1.00-6.10 % and 0.60-2.40 % (mass), respectively.

Determination of biodiesel and used cooking oil in automotive diesel/green diesel fuels through high-performance liquid chromatography

This study reports a simple and convenient analytical method for the simultaneous determination of biodiesel and vegetable oils or used cooking oils in petrodiesel and green diesel (hydrotreated vegetable oils or paraffinic diesel). The approach is based on normal-phase high-performance liquid chromatography with refractive index detection. It employed silica stationary phase, n-hexane mobile phase with isopropanol modifier to achieve optimum separation between hydrocarbons (petrodiesel or green diesel), fatty acid methyl esters (biodiesel) and triglycerides (vegetable oils and used cooking oil). In addition to determining vegetable oils or used cooking oils as adulterants in diesel, this method is also proposed as a better alternative to the standard method ASTM D7371, which is currently recommended for determining fatty acid methyl esters in petrodiesel. The method development involved screening of various stationary and mobile phases, with and without modifiers, to achieve acceptable chromatographic resolutions between analytes. Under the optimized method conditions, silica column, and n-hexane containing 0.6% isopropanol as the mobile phase provided the best results. The real-world scenario was simulated for the method validation carried out by fortifying Jatropha seed oil, soybean oil, and used cooking oil in the biodiesel blended petrodiesel and green diesel. Measurement of all analytes was accompanied by high precision, low limit of detection/quantification and linear response range of 0.05 to 50% for biodiesel, and 0.05 to 30% for vegetable oils. The proposed method is simple, fast (runtime 7 min), and does not require sample pre-treatment and backflushing.