Molecularly imprinted stir bar sorptive extraction coupled with high-performance liquid chromatography for trace analysis of naphthalene sulfonates in seawater

In this paper, a novel molecularly imprinted polymer coated stir bar has been used to selectively extract naphthalene sulfonates (NSs) directly from seawater sample. 1-Naphthalene sulfonic acid (1-NS) was used as template molecule. The effects of different parameters were optimized on the extraction efficiency and the optimum conditions were established as: the absorption and desorption times were fixed, respectively, at 10 and 15 min, stirring speed was 700 rpm, pH was adjusted to 4.1, amount of NaCl was 1 mol L−1 and extraction process was performed at a temperature of 50 °C. The linear ranges were 2–250 µg L−1 for 3,6-NDS-1-OH (1-naphthol-3,6-disulfonic acid), 4–250 µg L−1 for 2-NS (2-naphthalene sulfonate) and 3–250 µg L−1 for 1-NS. The detection limits were within the range of 0.32–0.95 µg L−1. Under optimum conditions, the detection limits of the NSs were 0.84, 0.95 and 0.32 µg L−1 with the enrichment factor of 117-, 41- and 77-fold for 2-NS, 1-NS, and 6-NDS-1-OH, respectively. The repeatability of the method was satisfactory (0.53 ≤ RSD ≤6.0 %, n = 10). The method has been successfully applied for the analysis of trace amounts of three naphthalene sulfonates in seawater of Chabahar Bay.