Quantitation of poly(diallyldimethylammonium chloride) by complexation with Acid Orange 7 dye

Abstract

The anionic dye Acid Orange 7 (AO7) was applied for quantitative determination of poly(di-allyldimethylammonium chloride) (PDDA) in aqueous solutions. The PDDA polymer forms colloidal complexes with the AO7 dye resulting in spectral changes. Increase in the polymer concentration up to 0.10 mmol(mer)/dm3 leads to decrease in absorbance at wavelengths in the range between 450 and 500 nm. The obtained calibration dependences between absorbance and concentration fulfill linear equation with quite small variance (s2 = 1.56 · 10-2). The proposed method of PDDA quantitation requires weak acidic medium (pH = 3.5 - 6.5) and low values of ionic strength (I ≈ 20 mM).