Efficient extraction of two different sulfonamide antibiotics from lipstick by magnetic solid-phase extraction based on c-MMWCNT@CDs/Fe3O4.

Some illegal businesses often add antibiotics such as sulfonamides to expand the functional range of lipstick. However, the abuse of antibiotics will lead to serious adverse reactions and increase the drug resistance of bacteria. To ensure the safety of lipstick, it is necessary to monitor the antibiotic content, which urgently needs to develop an efficient and highly sensitive analytical method. In this study, a magnetic solid-phase extraction (MSPE) method was developed using a composite adsorbent based on carboxylated multi-walled carbon nanotubes (c-MMWCNT) and carbon dots (CDs) for sample pretreatment. A magnetic dispersive solid-phase extraction coupled with high-performance liquid chromatography method was established using silanized serine‑modified carbon dots (Sil-Ser-OCDs) as the sorbent for the determination of sulfapyridine (SPY) and sulfamethazine (SMT). Key extraction parameters including adsorbent dosage, extraction time, and pH were optimized using response surface methodology. The optimal extraction conditions were determined to be an adsorbent dosage of 72 mg, extraction time of 4.5 min, and pH 6.0. Under the optimal conditions, the recoveries of SPY and SMT were in the range of 88.0%-93.4%, and the RSD values of intra-day and inter-day precision were under 4.2% and 5.4%, respectively, indicating that the approach has excellent accuracy and precision.