Signal processing algorithm for Schlieren effect correction in flow analysis

Due to the radial refractive index gradients that sometimes develop in flow cells during the travelling of the samples through them, the absorbance re cords obtained in such conditions have a strange shape, particularly at low analyte levels. To correct this phenomenon, called Schlieren effect, a sim ple and reliable signal processing algorithm is described in correlation to the detector characteristics of noise. The algorithm is illustrated in nit rite and nitrate determinations with proflavin from more real samples. It h as a solid theoretical support and involves the subtraction from the sample records of a smoothed signal, acquired by working with a blank solution.