Recommended modifications to the spectrophotometric determination of molybdenum as Fe[MoO(SCN)5]

The classical method for the determination of molybdenum in plant material by the formation of an iron-molybdenum- thiocyanate complex, which is extracted with alcohols, ethers and carbon tetrachloride from a dilute acid solution, is basically very suitable for the detection of molybdenum at levels below 1 mg kg−1. While routine use indicated that the spectrophotometric detection could not be faulted, it was nevertheless observed that stable emulsions frequently formed after the second extraction, which resulted in an extract unsuitable for the detection of molybdenum. The method of extraction was modified by changing extraction times and volumes of reactants and by the use of funnels fitted with greaseless teflon stopcocks, with good results. The complex or mode of detection was left unchanged.