# A Review: Sample Preparation and Chromatographic Technologies for Detection of Aflatoxins in Foods
## 3 Chromatography
### Capillary Electrophoresis  
As an electrokinetic separation technique, capillary electrophoresis is performed in submillimeter diameter capillaries or micro- and nanofluidic channels filled with a buffer solution. In an electric field, charged analytes and matrix components in the buffer would migrate with different rates depending on their charges and sizes, hence being separated. Benefits of CE include good separation efficiency (separation achieved within 1 min), ease in the instrument setup and operation and small sample and buffer volumes (nL ranges). Flexible separation conditions can be optimized by changing buffer additives. Conventional capillary zone electrophoresis CZE and micellar electrokinetic capillary chromatography (MECC) are the two major techniques that have been evaluated for aflatoxin analysis [301; 302]. Advances in microfabrication techniques developed in the semiconductor industry enable the miniaturization of CE on microchips [303]. Since the 2000s, there has been increasing attention to capillary CE chip-based mycotoxin analysis. Coupled with modern MS, these CE chips could lead to innovative applications for aflatoxin analysis [304].  
[PERSON] and [PERSON] [305] used MECC to separate 10 mycotoxins, including aflatoxin B1, B2, G1 and G2 but the study focused on separation capacity of the system and how to normalize retention times of target analytes with no quantitative data provided. [PERSON] et al. [306] carefully evaluated the key parameters (e.g., internal diameters of capillaries, viscosity and compositions of mobile buffer and fluorescence properties for aflat in various solvents) that could affect micellar electrokinetic capillary chromatography for aflatoxin analysis. The separation of aflatoxin B1, B2, G1 and G2 was achieved within 30 s using a capillary column (40 cm L x 25 mm ID) and detected using an on-column laser-based fluorescence detection. The limits of detection are 1000 ppb and extensive SPE cleanup was performed prior to the injection of corn sample extracts. Sensitivity of the method, however, is insufficient to detect aflat at or below the target U.S. regulatory limit of 20 ppb. In a later study, [PERSON] and [PERSON] [307] achieved a much lower limit of detection (0.5 ppb) of aflatoxin B1 in corn by CE and FLD. Average recoveries of aflatoxin B1 spiked at 1-50 ppb are around 85%. Due to the very low on-column mass of CE and fluorescence interference from the CE buffer or matrix components, these studies suggest the need of more specific and sensitive detection technologies.  
[PERSON] et al. [308] used integrated plastic microfluidic devices with ESI-MS to separate and detect aflat. In the study, an in-house microfabricated affinity dialysis and concentration system was developed. Specific detection of aflatoxin B\({}_{1}\) was achieved by optimizing the molar binding ratios of aflatoxin B\({}_{1}\) antibody to each aflatoxin and a flow rate around 100 nL/min. The study shows potential of miniaturization of CE but follow-up studies are needed to demonstrate its applicability in foods for aflatoxin analysis. Furthermore, when CE is coupled with MS, cost and complexity of the system is no less than that of LC-MS. Between a well-established technique (LC-MS) and an analytical technique with certain potentials (CE-MS) for aflatoxin analysis, preference is most commonly given to LC-MS-based technologies. It is expected that CE especially CE microchips will remain as a research-oriented technique in the near future.