Determination of unsulphonated quinoline yellow in soft drinks by solid-phase spectrophotometry

A spectrophotometric method for determination of quinoline yellow spirit soluble (QYSS) in the presence of sulphonated quinoline yellow water soluble (QYWS) in soft drinks at trace levels is reported. The method is based on the fixation of QYSS on C-18 silica gel, followed by measurement of its absorbance at λ = 418 nm in the solid phase after being packed in a 1-mm cell. The applicable concentration range was 1.5–15.0 ng/ml, the detection limit 0.4ng/ml and the relative standard deviation 5.2%. The method was applied satisfactorily to the determination of this compound in samples of commercial soft drinks.