Nonextractive spectrofluorimetric determination of aluminium in real, environmental and biological samples using chromotropic acid.

An ultra-sensitive and highly selective nonextractive fluorimetric method is presented for the rapid determination of aluminium at nano-trace levels using chromotropic acid as a fluorimetric reagent [lambda(ex) = 360 nm and lambda(em) = 390 nm] in the pH range of 4.1-4.7. The fluorescence intensity of the metal chelate (2:3 complex) reaches a constant value within 1/2 hr and remains unchanged for over 48 hr. The fluorescence intensity aluminium concentration calibration curve is collinear between 1 and 300 ng/ml of Al. A constant fluorescence intensity is obtained over a wide range (1:50-1:1500) of Al:reagent molar concentrations. Large excesses of over 60 cations, anions and complexing agents (like tartrate, oxalate, phosphate, thio-urea, SCN(-), etc.) do not interfere in the Al determination. The developed method was successfully used in assaying aluminium in several standard reference materials (Al-bronze, brass, stainless steel) as well as in some environmental and biological samples. The method is very precise and accurate (S.D = +/-0.001 on 10 ng/ml; 11 determinations).