![\"Analysis](\"https:\/\/scioninstruments.com\/wp-content\/uploads\/2024\/01\/8500-3-300x249.png\")
<\/p>\nMineral oil hydrocarbons are typically found in water, foods and soils. These hydrocarbons can be extracted using a variety of solvents, with the most popular being hexane and petroleum ether. As concentrations can be very low, sample enrichment is often required. However, SCION instruments developed a method that simply uses a Large Volume Injection (LVI) technique to simplify sample pre-treatment whilst dramatically increasing throughput.<\/p>\n
The Hydrocarbon Index (HOI) is the total amount of compounds which can be extracted from water samples using a non-polar solvent. The solvent must have a boiling point between 39\u2103 and 69\u2103, thus replacing the use of halogenated solvents. Halogenated solvents and high concentrations of polar substances can interfere with the determination of the HOI. In addition, the compounds must not absorb on Florisil and must elute between n- decane and n-tetracontane. The method is suitable for HOI determinations in concentrations above 0.1mg\/L in water samples.<\/p>\n
This application note describes the highly efficient analysis of mineral oil hydrocarbons in water using the SCION 8500 GC equipped with a Programmable Temperature Vaporiser (PTV). The system is very well suited to the DIN-EN-ISO 9377 method and it can be visualized in Figure 1.<\/p>\n
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Figure 1. SCION Instruments 8500 GC<\/span><\/p>\n Five calibration standards were prepared in hexane at various concentrations; 0.2mg\/mL, 0.4mg\/mL, 0.6mg\/mL, 0.8mg\/mL and 1.0mg\/mL. A blank sample was also prepared.<\/p>\n A reference sample containing mineral oil hydrocarbons was obtained from the National Institute for Public Health and the Environment (RIVM). The test sample contained alkanes for HOI analysis. All samples were prepared by dissolving the alkanes in hexane.<\/p>\n Table 1 details the analytical parameters used throughout this application.<\/p>\n Table 1. <\/sub><\/strong>Instrumentation operating conditions<\/sub><\/p>\n 0.45min OFF 100<\/p>\n 3.00min ON 150<\/td>\n<\/tr>\n The sample was introduced in the PTV at a temperature that equals the boiling point of the solvent. Initially, the split was open allowing much of the solvent to evaporate from the vent. After 0.17 minutes, the split vent closed and the temperature increased. This allowed the evaporation and injection of the sample onto the column. Figure 2 shows a chromatogram from a calibration standard.<\/p>\n System suitability was checked via the C10 \/ C20 and C40 \/ C20 peak areas, with twenty injections of a low level calibration standard. The acceptable limits are defined as a peak are ratio between 0.8 and 1.2. Figure 3 shows the repeatability of both specifications.<\/p>\n The high ratios obtained from the repeatability testing show a high recovery of the sample components and minimal discrimination. The high recovery was obtained from the specialised mineral oil liner which was optimised for longer retention of the sample components; this allows more of the solvent to be vented off and not introduced to the analytical column. With system suitability passing specification, the RIVM reference sample was analysed, as shown in Figure 4.<\/p>\n The reference sample was also subjected to repeatability testing (n=8), as shown in Table 2. Figure 5 details the repeatability of the hydrocarbon ratios.<\/p>\n Table 2. <\/sub><\/strong>Repeatability of RIVM sample with hydrocarbon ratio (n=8) C10\/C20<\/strong><\/td>\n C20\/C40<\/strong><\/td>\n <\/p>\nExperimental<\/h2>\n
\n\n
\n Conditions<\/strong><\/td>\n <\/td>\n<\/tr>\n \n PTV<\/td>\n 70\u00b5L, 45\u00b0C (0.45min), 200\u00b0C\/min to 350\u00b0C (8 min)<\/td>\n<\/tr>\n \n PTV Split<\/td>\n Initial ON 75<\/p>\n \n Liner<\/td>\n SCION Mineral Oil Liner<\/td>\n<\/tr>\n \n Column<\/td>\n \u00a0Mineral Oil 15m x 0.32mm x 0.15\u00b5m<\/td>\n<\/tr>\n \n Oven<\/td>\n \u00a035\u00b0C (4 min), 60\u00b0C\/min to 150\u00b0C, 50\u00b0C\/min to 250\u00b0C, 30\u00b0C\/min to 350\u00b0C (1.50 min)<\/td>\n<\/tr>\n \n FID<\/td>\n \u00a0350\u00b0C<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Results<\/h2>\n
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\nFigure 2<\/sup><\/strong>. Chromatogram of a calibration standard<\/sup><\/p>\n![\"\"](\"https:\/\/scioninstruments.com\/wp-content\/uploads\/2020\/12\/Figure-3.-Repeatability.png\")
\nFigure 3<\/sup><\/strong>. Repeatability data on C10\/C20 and C40\/C20 (n=20)<\/sup><\/p>\n![\"\"](\"https:\/\/scioninstruments.com\/wp-content\/uploads\/2020\/12\/Figure-4.-Chromatogram-RIVM-747x429-1.png\")
\nFigure 4<\/sup><\/strong>. Chromatogram of RIVM reference standard<\/sup><\/p>\n
\n<\/sub><\/p>\n\n\n
\n Run<\/strong><\/td>\n Area<\/strong><\/p>\n Area<\/strong><\/p>\n HC Ratio<\/strong><\/td>\n<\/tr>\n \n 1<\/td>\n 1201944<\/td>\n 1860482<\/td>\n 1.55<\/td>\n<\/tr>\n \n 2<\/td>\n 1208160<\/td>\n 1867571<\/td>\n 1.55<\/td>\n<\/tr>\n \n 3<\/td>\n 1205740<\/td>\n 1846199<\/td>\n 1.53<\/td>\n<\/tr>\n \n 4<\/td>\n 1212651<\/td>\n 1826599<\/td>\n 1.51<\/td>\n<\/tr>\n \n 5<\/td>\n 1194517<\/td>\n 1850616<\/td>\n 1.55<\/td>\n<\/tr>\n \n 6<\/td>\n 1190457<\/td>\n 1854374<\/td>\n 1.56<\/td>\n<\/tr>\n \n 7<\/td>\n 1189986<\/td>\n 1851458<\/td>\n 1.56<\/td>\n<\/tr>\n \n 8<\/td>\n 1193781<\/td>\n 1852083<\/td>\n 1.55<\/td>\n<\/tr>\n \n Average<\/td>\n 1199654<\/td>\n 1851173<\/td>\n 1.55<\/td>\n<\/tr>\n \n St. Dev<\/td>\n 8640<\/td>\n 11926<\/td>\n 0.017<\/td>\n<\/tr>\n \n RSD (%)<\/strong><\/td>\n 0.72<\/strong><\/td>\n 0.64<\/strong><\/td>\n 1.11<\/strong><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
![\"\"](\"https:\/\/scioninstruments.com\/wp-content\/uploads\/2020\/12\/Figure-5.-hydrocarbon-ratio.png\")