Spectrophotometric determination of total rare earths in steel with arsenazo III in the presence of sodium dodecylsulfonate

Influences of five surfactants like hexadecyltrimethylammonium bromide(CTMAB),sodium dodecylsulfonate(SDS),Tween-80,polyvinyl alcohol(PVA),emulson OP on the color reaction of rare earths,arsenazoⅢ and alcohol were studied.Results showed that only SDS had an effect of enhancing sensitivity.In the HAc-NaAc medium at pH 2.8 and in the presence of SDS,rare earth formed a stable colored complex with arsenazo Ⅲ,the maximum absorption wavelength of the reagent and complex were at 540nm,and 655nm,respectively.The apparent molar absorptivity e was 9.5×104L·mol-1·cm-1.Beer's law was obeyed in the range of 0 to 50 μg/25 mL.Proposed method has been directly applied to determine total rare earths in low-alloyed steel with the RSD of 0.37%-1.6%.The determination results are in good agreement with the certified values.