| Acrylamide（AM）is a by-product formed by the Maillard reaction,which occurs during heat processing of foods rich in carbohydrates at temperatures above 120 oC.In recent years,many reports have revealed that consumption of AM could lead to genotoxic damage,neurotoxic effect,carcinogenic potential,and even gene mutation.Therefore,it is particularly important to monitor and control the content of AM in foods.To date,many analytical methods have been developed to determine the AM amount in foods.Although these traditional detection methods show good performance in terms of accuracy,they generally require complicated sample pre-processing and expensive instrumentation.Fluorescent carbon quantum dots（CDs）are a new kind of excellent optical nanomaterials,with advantages such as environmental friendliness,low toxicity,low cost,simple synthetic routes,and water solubility.Because of these unique properties,CDs have been used as fluorescence probes for detecting food additives and harmful substances.In this study,two fast and simple fluorescence methods based on the CDs and the properties of AM were developed for quantifying AM in bread crust samples.The main research contents and conclusions of this study are as follows:（1）Synthesis and characterization of CDs.Firstly,a safe,rapid and efficient microwave digestion method was used to prepare CDs.Simultaneously,the effects of different molar ratios of carbon to nitrogen sources,reaction temperature,time and power on the synthesis of CDs were explored.And the optimal synthesis conditions were the molar ratio of 1:1.5,reaction temperature of 200 oC,reaction time of 5 min,and reaction power of 600 W.Besides,the CDs with the best fluorescence performance were characterized and analyzed.Results revealed that the CDs with high quantum yield of 78.13%were nearly spherical in shape and well dispersed in water with an average particle diameter about 4 nm.In addition,the CDs showed a strong emission peak at 445 nm when the excitation wavelength was 350 nm.What’s more,functional groups enable current CDs to display eminent water solubility,and the fluorescence intensity of CDs had minimal change with light and storage time,confirming its photo stability and time stability.（2）Rapid detection of AM based on the fluorescent chemical sensor.The detection relied on the distance change between NAS-CDs induced by AM polymerization.The present method showed good stability and reproducibility,and provided a broad linear relationship in the detection system with AM concentrations ranging from 5 10-3 to 1 10-6 M,achieving a low LOD of 9.36 10-7 M.Besides,a novel method for the pretreatment of white bread crust samples was developed based on Qu ECHERS,satisfactory recoveries of 89.44-97.83%,and RSD values of 1.08-2.82%（<5%）for the experimental results in white bread crust samples also indicated the feasibility for monitoring AM contents in baked food.（3）Rapid detection of AM based on the fluorescent bio-sensor.Fluorescent CDs obtained by the optimal synthesis conditions was utilized as fluorescence signal.The single-stranded DNA can attach to the surface of fluorescent CDs and also have high affinity with AM,which lead to the changes of fluorescence intensity.Based on the principle,this method showed good stability and reproducibility,and provided a broad linear relationship in the detection system with AM concentrations ranging from 5 10-3 to 1 10-7 M,achieving a low LOD of 2.41 10-8 M.Besides,a novel method for the pretreatment of white bread crust samples was developed based on Qu ECHERS,satisfactory recoveries of 91.36-98.11%,and RSD values of 1.15-2.30%（<5%）for the experimental results in white bread crust samples also indicated the feasibility for monitoring AM contents in baked food.（4）Summarizition and evaluation of AM standard detection method（LC-MS/MS method）and two fluorescent sensors in current studuy.Compared with LC-MS/MS,two fluorescence methods had wider detection range,shorter detection time and lower cost.Simultaneously,fluorescent bio-sensor had similar LOD and recovery values with LC-MS/MS.In addition,for fluorescent chemical sensor,the time from preparing to detecting need 200 min,while fluorescent bio-sensor just need 90 min.However,the sensitivity of these two methods were inferior to LC-MS/MS. |
