Detection method based on supercritical fluid chromatography and post-column ionic liquid charge complexation

A detection method based on supercritical fluid chromatography (SFC) and post-column dicationic ionic liquid (DIL) charge complexation, which includes the following steps:

• preparing a supramolecular solvent (SUPRAS) by mixing heptanol, tetrahydrofuran, and water;
• performing sample pretreatment to extract samples by the SUPRAS and to obtain a test solution for subsequent analysis, wherein the samples are textiles;
• performing an analysis of perfluorinated compounds (PFCs) in the test solution using SFC separation, post-column DIL-based charge complexation, and electrospray ionization-mass spectrometry (ESI-MS), wherein the DIL is 1,1′-dioctyl-4,4′-bipyridinium dibromide;
• wherein the chromatographic conditions are as follows:
• a DIOL chromatographic column (2.1 mm×100 mm, 1.7 μm) is used, a binary mobile phase is composed of pressurized carbon dioxide (A) paired with 0.1% ammonia in methanol (B), initial conditions are 5% B, and a linear elution gradient is then programmed from 5% B to 20% B within 8.9 min, and held for 0.1 min, at 9.5 min, the gradient is linearly returned to 5% B and maintained for 0.5 min to complete a whole run, a column temperature is set to 40° C., a flow rate is 0.3 mL/min, an automatic back pressure regulator (ABPR) pressure is set to 2000 psi, a sampling volume of 2 μL of the test solution is injected, and a flow rate of a make-up solvent was 0.2 mL/min, wherein the make-up solvent was a mixture of methanol and water at a ratio of 1:1 (v/v);
• after the SFC separation, the DIL is dissolved in the make-up solvent of SFC and introduced post-column but before an ESI source;
• wherein—the PFCs include perfluorododecanoic acid (PFDoDA), perfluoroundecanoic acid (PFUnDA), perluorodecanoic acid (PFDA), perfluorononanoic acid (PFNA), perfluorooctanoate (PFOA), perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHA), perfluoropentanoic acid (PFPA), perfluorooctane sulfonate (PFOS), and perfluorobutane sulfonate (PFBS).