Spectrophotometric determination of trace gallium with 5'-nitrosalicylfluorone in microemulsion medium

The color reaction of 5'-nitrosalicylfluorone with gallium in the presence of OP microemulsion medium is studied.Experimental results show that in hydrochloric acid at pH2.0 and in the presence of microemulsion(m(OP)∶m(n-butanol)∶m(n-heptane)∶m(water)=5.0∶3.3∶0.8∶90.9),gallium with reagent forms 1∶2 stable purple complex,of which the maximum absorption wavelength is at 524nm.The apparent molar absorptivity is 2.03×105 L·mol-1·cm-1.Beer′s law is obeyed in the range of 0-240 μg/L for gallium.The method has been applied to the determination of gallium in coal with RSDs of 1.4%-2.6% and the determination results are in consistent with those of rhodamine B spectrophotometry.