Pretreatment-free fast ultraviolet detection of melamine in milk products with a disposable microfluidic device.

A new method for sensitive and fast screening of melamine (MEL) in milk products was developed with a low-cost disposable microfluidic device coupled with ultraviolet (UV) detection. This method avoided the need of sample pretreatment prior to the separation process, thus was simple and green. Due to the advantages of the device and fracture sampling technique, milk sample could be directly sampled through the fracture to achieve baseline separation from amino acids, and proteins in the sample did not interfere with the detection. Using 20mM phosphate running buffer (pH 9.0), a sampling time of 3s at +180V and a separation voltage of +1800V (240V/cm), this method could detect MEL in milk within 75s. At the detection wavelength of 202nm, the linear range for MEL was from 1.0 to 100microgmL(-1) with a detection limit of 0.23microgmL(-1) (S/N=3). The novel protocol had been successfully used to screen MEL in milk samples with recovery more than 82%. The environmentally friendly methodology for pretreatment-free sensitive screening of MEL provided promising applications in monitoring the quality of different foods.