Near-UV molar absorptivities of acetone, alachlor, metolachlor, diazinon and dichlorvos in aqueous solution

An experimental set-up consisting of two parallel absorption cells coupled to a CCD detector was used to determine absolute values of molar absorptivity coefficients ɛ of acetone and of several pesticides (alachlor, metolachlor, diazinon and dichlorvos) in water. The absorption spectra were measured using a deuterium lamp over the wavelength range of 240–320 nm at room temperature (298 ± 2 K). ance were also measured at 253.7 nm using an Hg-lamp in different concentrations range depending on the studied compound. The absolute values of molar absorptivity coefficients at this wavelength were determined according to the Beer–Lambert law: ɛ = 13.9 ± 1.0 for acetone, ɛ = 466 ± 41 for alachlor, ɛ = 615 ± 63 for metolachlor, ɛ = 3558 ± 323 for diazinon, ɛ = 5.5 ± 0.5 for dichlorvos (in units of M−1 cm−1). The quoted errors correspond to 2σ obtained from the least square fit analysis and the estimated systematic error of 5% due to the uncertainties in aqueous concentrations. For all the studied compounds, the absorbances measured were lower than two and did not exhibit any deviation from the Beer–Lambertʹs law.