An ultrasound-assisted magnetic solid phase microextraction procedure was developed for separation and enrichment of trace levels of patent blue V in different syrups, waters and artificial sweat samples prior to its determination by UV-Vis spectrophotometry. Three mg magnetic multiwalled carbon nanotube (mMWCNT) was used as solid phase. Several variables affecting microextraction efficiency such as sample volume, pH, matrix effect, volume and type of eluent, sample volume were investigated and optimized. The developed SPME method presents a limit of detection (LOD, N = 10) of 3,5 mu gL(-1), analyte recoveries were 98-100%, pre concentration factor of 250 and a relative standard deviation (RSD, %, N = 10) of 1,5% under the optimum conditions. The proposed procedure for determination of patent blue V in different environments samples is precise, accurate, very simple, practical, fast, easy to apply and economical.