Sodium cyclamate is commonly used as a food additive in the production of cakes, preserved fruits, beverages and other food products because of its high sweetness (sodium cyclamate is 30⁓80 times sweeter than sucrose), low calories and low price[1−3]. In GB 2760 − 2014, the national food safety standard for the use of food additives in China clearly stipulated the dosage (0.65-8.0g/kg) of sodium cyclamate in Fig. 1.
Figure 1 Maximum usage of cyclamate in various foods specified in the Fourth National
The scientific committee for food of the European Union stipulated that human acceptable daily intake value of sodium cyclamate was 7mg/(kg bw). The use of excessive range and limit of sodium cyclamate can damage the microfilaments and microtubules of osteoblasts, inhibit bone cells activity, the expression of bone morphogenetic protein-2, and even damage to the structure of DNA.
Various techniques including gas chromatography[1, 7], liquid chromatography, liquid chromatography-mass spectrometry and so on[10–12] have been established for the detection of sodium cyclamate. However, new methods with low detection cost, high sensitivity, and short response time are always being established.
Carbon quantum dots (CQDs) are a new kind of nanomaterials, which is to use natural resources or waste materials (papaya, watermelon, tomato, aloe vera, peach and et al.)as carbon sources in order to reduce the environmental pollution[13–18]. Coffee is a beverage made from roasted and ground coffee beans. As one of the three largest beverages in the world, coffee is consumed around 9 million tons globally each year. During the production or use of coffee, a lot of coffee-grounds are often produced. Coffee-grounds are rich in carbon sources and nitrogen sources, so it can be used as a high-quality carbon source for the production of CQDs. Up to now, CQDs prepared from the coffee-grounds for the sodium cyclamate detection has been scarcely reported.
In this work, coffee-grounds as carbon source to synthesize CQDs by one-step hydrothermal method could detect sodium cyclamate in food with high efficiency and environment friendly. In the concentration range of 2.8 ~ 56 µmol/L, sodium cyclamate was linear with the CQDs of coffee-grounds, and the detection limit was 3.16 µmol/L.