Concentrations of Monocyclic Aromatics Hydrocarbons: Benzene, toluene, ethylbenzene, and xylene (BETX) in gasoline samples distributed in Uyo, Niger Delta, Nigeria

Benzene, toluene (methylbenzene), ethylbenzene, and xylene (dimethylbenzene) (BTEX) are volatile organic compounds added to unleaded gasoline to increase octane number, adjust Reid vapor pressures (RVP), British Thermal Unit (BTU) and as anti-knocking agents. BTEX cause several environmental and harmful human health problems. Uyo metropolis is one of the most urbanized cities in Niger Delta impacted by activities of artisanal or illegal oil refining in the Niger Delta Creeks. Also, Nigeria imports most of her petroleum products as a result of inoperability of local refineries. There is therefore need for independent periodic quality check on the petroleum products supplied in the area. Hence the aim of this study was to determine the concentrations of BTEX in some gasoline samples distributed in Uyo and compare the concentrations with regional and international standards in respect to human health, environmental concerns and engine efficiency. Gasoline samples from ten (10) different gasoline filling stations were randomly sampled and analyzed for BTEX using Gas Chromatography Flame-Ionization Detection GC-FID through direct injection. The highest and lowest concentrations of benzene were 188.116 mg/L (0.020% by volume) and 44.063 mg/L (0.004 % by volume). The highest and lowest concentrations of toluene were 148.839 mg/L (0.015% by volume) and 2.835 mg/L (<0.001 %). The highest concentrations of ethylbenzene 165.257 mg/L (0.020 %), m, p –Xylene 1264.797 mg/L (0.120 %) and o-Xylene 8.089 mg/L (< 0.001 %) were also recorded. The levels of BTEX in gasoline samples analyzed were within permissible limits (1 % by volume of benzene) and 42 % by volume of toluene, ethylbenzene and xylene, as recommended by EURO 5 and the African Refiners Association (ARAI 5). There is a need for periodic quality evaluation of gasoline and other petroleum products circulated in the study area.