Non-extraction batchwise and FIA determination of cationic and nonionic surfactants using Cu(II)–chromazurol S–surfactant complexes

Batchwise and FIA determinations have been developed for cationic and nonionic surfactants, based on the formation of ternary Cu(II)–chromazurol S–surfactant compounds. Optimum reaction conditions have been found (pH 8.0, λ=590 and 630 nm, respectively). For the batchwise measurement, the molar absorption coefficient values ε590=5.1–5.7×104 l mol−1 cm−1 for cationic surfactants, ε630=0.7–1.5×104 l mol−1 cm−1 for nonionic surfactants. A factorial design has been carried out to determine the optimum flow conditions. Calibration curves were constructed and statistically evaluated for both the batchwise and FIA determination. For example, the linear concentration ranges for batch determination of the cationic surfactant cetyltrimethylammonium bromide and nonionic surfactant Marlophen NP 10 are 0–15 μg ml−1 (R=0.9996, R.S.D.=6.62–0.64%) and 13–53 μg ml−1 (R=0.9993, R.S.D.=4.48–1.40%), respectively; the respective detection limits are 0.02 and 4.0 μg ml−1. For FIA determination of the same surfactants, the linear concentration ranges are 0–13 μg ml−1 (R=0.9995, R.S.D.=4.44–0.49%) and 66–397 μg ml−1 (R=0.9994, R.S.D.=8.92–1.12%), respectively, detection limits are 0.08 and 38 μg ml−1, respectively.