Development of a novel naphthoic acid ionic liquid and its application in “no-organic solvent microextraction” for determination of triclosan and methyltriclosan in human fluids and the method optimization by central composite design

Abstract In traditional ionic liquids (ILs)-based microextraction, the hydrophobic and hydrophilic ILs are often used as extractant and disperser, respectively. However, the functional effects of ILs are not utilized in microextraction procedures. Herein, we introduced 1-naphthoic acid into imidazolium ring to synthesize a novel ionic liquid 1-butyl-3-methylimidazolium naphthoic acid salt ([C 4 MIM][NPA]), and its structure was characterized by IR, 1 H NMR and MS. On the basis of its acidic property and lower solubility than common [C n MIM][BF 4 ], it was used as a mixing dispersive solvent with [C 4 MIM][BF 4 ] in “functionalized ionic liquid-based no organic solvent microextraction (FIL-NOSM)”. Utilization of [C 4 MIM][NPA] in FIL-NOSM procedures has two obvious advantages: (1) it promoted the non-polar environment, increased volume of the sedimented phase, and thus could enhance the extraction recoveries of triclosan (TCS) and methyltriclosan (MTCS) by more than 10%; and (2) because of the acidic property, it can act as a pH modifier, avoiding extra pH adjustment step. By combining single factor optimization and central composite design, the main factors in the FIL-NOSM method were optimized. Under the optimal conditions, the relative recoveries of TCS and MTCS reached up to 98.60–106.09%, and the LODs of them were as low as 0.12–0.15 µg L −1 in plasma and urine samples. In total, this [C 4 MIM][NPA]-based FIL-NOSM method provided high extraction efficiency, and required less pretreatment time and unutilized any organic solvent. To the best of our knowledge, this is the first application of [C 4 mim][NPA]-based microextraction method for the simultaneous quantification of trace TCS and MTCS in human fluids.