Multiwalled carbon nanotubes–poly(vinyl alcohol) composite cryogel used in microcolumn liquid chromatography to separate various herbicides†
A simple liquid chromatographic system that consisted of a Teflon tube filled with a MWCNTs–PVA composite cryogel microcolumn connected to an on-column UV-visible detector was developed. The system was applied to the simultaneous determination of atrazine, diuron and 2,4-(dichlorophenoxy)acetic acid (2,4-D) in water samples. Using optimum conditions, the system provided a linear range from 1.0 μg L−1 to 1.50 mg L−1 for atrazine and diuron and 2.0 μg L−1 to 2.00 mg L−1 for 2,4-D. The limits of detection were 0.75 μg L−1 for atrazine and diuron and 1.00 μg L−1 for 2,4-D. A good microcolumn-to-microcolumn reproducibility with a relative standard deviation (RSD) of 1.4–2.3% and a good precision with % RSD of 1.09, 0.95 and 1.56 for peak areas of atrazine, diuron and 2,4-D were obtained. The developed method provided good chromatographic performance, with the values of plate number (N ≥ 2000), the peak asymmetry factor (As ≤ 1.0), resolution (Rs ≥ 5.6) and capacity factor (3.3 ≤ k′ ≤ 14) all within the acceptable ranges. This simple liquid chromatographic system, with a 10 cm long microcolumn, without a high pressure pump, was successfully applied to the simultaneous determination of atrazine, diuron and 2,4-D in water samples. This developed method could be easily applied to the separation of other compounds.