Mineral oils are complex mixtures of straight and branched chain paraffinic, naphthenic and aromatic hydrocarbons refined from petroleum crude oils. Mineral oil with a carbon number of 15 to 25 is categorized as light oil and 25 to 50 as heavy oil. Mineral oil is commonly used in food, cosmetics and pharmaceutical industries especially in skin care products. Mineral oil is used as overlaying agent in polymerase chain reaction (PCR) and electrophoretic techniques to avoid evaporation.