Sulfaquinoxaline [KLH]

In this study, two novel fluorescence quenching immune chromatographic strips (FQICS) were developed to detect sulfaquinoxaline (SQX) in foods of animal origin. These proposed FQICSs were based on fluorescence resonance energy transfer (FRET) from fluorescence donors (quantum dots or upconversion nanoparticles) to fluorescence acceptors (colloidal gold nanoparticles). Compared with traditional colloidal gold-based immune chromatographic strips (ICS), these FQICSs showed positive correlation between the fluorescent signals and the targets, and allowed user to get test results from weak fluorescent signals. The visual detection limits of these two FQICSs were both 1 ng mL(-1) in standard solution and 8 mg kg(-1) in samples, while the visual detection limit of the colloidal gold-based ICS was 10 ng mL(-1) in standard solution and 80 mg kg(-1) in samples. Besides, the results we obtained by the use of FQICS showed high agreement with those obtained by the use of commercial ELISA kits, indicating the good accuracy of these strips. As a conclusion, these proposed FQICS based on quantum dots and upconversion nanoparticles can be applied in sensitive, rapid and on-site detection of SQX in foods of animal origin. (C) 2017 Elsevier B.V. All rights reserved.

A rapid and sensitive immunochromatographic assay (ICA) based on competitive format was developed and validated for simultaneous detection of sulfamethazine (SM2), sulfadiazine (SDZ), and sulfaquinoxaline (SQX) in chicken breast muscle and egg samples. For this purpose, three monoclonal antibodies raised against those three sulfonamides were conjugated to colloidal gold particles and applied to the conjugate pads of the test strip. The competitors of the sulfonamides (SM2/SDZ/SQX-bovine serum albumin conjugates) were immobilized onto a nitrocellulose membrane at three detection zones to form T-1, T-2, and T-3, respectively. With this method, the cutoff values for the three test lines were achieved at 80 mu g/kg, which is lower than the maximum residue levels (MRLs) established for sulfonamides. The recoveries in negative samples spiked at concentrations of 10, 50, and 100 mu g/kg ranged from 75% to 82% for egg samples and from 78% to 81% for chicken samples. The method was compared with the HPLC method by testing 180 eggs and chicken breast samples from local markets, and an agreement rate of 99.7% was obtained between the two methods.