Sulfonic acid-functionalized covalent organic framework@Ti3C2Tx as efficient solid-phase microextraction blade coating for the extraction of monoamine neurotransmitters in rat serum samples

Herein, a sulfonic-functionalized covalent organic framework@Ti₃C₂T_x nanocomposite (SO₃HCOF@Ti₃C₂T_x) was synthesized and employed as solid phase microextraction (SPME) coating for isolation and extraction of monoamine neurotransmitters (MNTs) from rat serum samples. The resultant composite can combine the characteristics of hydrophilic Ti₃C₂T_x and SO₃HCOF, which endow it has multiple adsorption sites and can provide multiple interactions such as cation exchange, hydrogen bonding and π-π with the target MNTs. The synthesized SO₃HCOF@Ti₃C₂T_x SPME blades have excellent protein exclusion capability, ensuring high adsorption efficiency for MNTs. Under the optimized conditions, the proposed SO₃HCOF@Ti₃C₂T_x blades-based SPME-HPLC method exhibited good linearities (r²≥0.9963), low limits of detection (0.015–0.030 ng mL^-1) and low matrix effect (0.83 %-17.36 %). The recoveries of MNTs in the rat serum were in range of 90.3 %-118.3 %, with RSDs <10.8 %. The SPME-HPLC method was successfully applied for the analysis of 4 MNTs in the serum of depression model rats. This work not only details the development of a multi-functional composite, but it also presents an effective strategy for the determination of trace MNTs in serum sample.