Malathion was estimated indirectly by spectrophotometry. The N-bromosuccinimide (NBS) was used to gradually oxidise malathion [6,18]. Excess NBS, when reacted with rhodamine B, decrease its absorbance for which maxi- mum absorbance was at 550 nm [18]. The decrease in the absorbance is directly proportional to the amount of NBS. From these values, reacted NBS and in turn amounts of malathion were calculated. Beer’s law was obeyed in the concentration range of 0.1 - 1.0 μg•mL–1 [6,18]. All the measurement of malathion have Instrumental RSD < 0.5% whereas the method RSD is