| Rhodamines (Rhs) are a glass of highly water-soluble (50g L-1) compounds belonging to xanthene family. It has been widely used as colourant in textile industry and foodstuffs. Due to its fluorescent properties, it is often used as a pathological marker or a fluorescent tracer in water courses. The carcinogenicity and toxicity of Rh towards human and animals have been experimentally proved. Therefore, the development of accurate, sensitive, and rapid methods for detecting Rh is crucial for human food safety. In this paper, based on optimization of cloud point extraction, trace amount of Rhs in real samples has been determined by spectrographic technique coupled with partial least squares regression and second-order calibration method.(1) Mixed micelle-mediated extraction for simultaneous trace determination of rhodamine B (RhB) and rhodamine6G (Rh6G) by UV-vis spectrophotometry coupled with the partial least squares regressionA modified cloud point extraction (CPE) method, which utilized a combination of the nonionic surfactant, Triton X-114, and the anionic surfactant, sodium dodecyl benzene sulfonate (SDBS), as the extractant, was used to preconcentrate RhB and Rh6G from sample solutions. The extraction conditions, such as pH, surfactants consumption, equilibration time and effect of the ionic strength (co-existing ions) on the CPE were investigated and optimized using a single-factor method followed by a L9(34) orthogonal array design (OAD). The maximum absorption wavelengths for RhB and Rh6G were558and533nm, respectively; linearity was obeyed in the range of3.4-550and4.0-500ng mL-1with detection limits of1.2and1.8ng mL-1, and the root mean square errors of prediction (RMSEP) were9.166and11.699ng mL-1, respectively. The proposed method has been successfully applied to simultaneously determine trace amount of RhB and Rh6G in real samples with the recoveries of86.8-111.8%. (2) Determination of Rhodamine B in food samples using chemometrics-assisted excitation-emission matrix fluorescence (EEMF) after rapidly synergistic cloud point extractionA novel method applying excitation-emission matrix fluorescence spectroscopy (EEMF) coupled with second-order calibration method for determination of rhodamine B (RhB) in food samples was developed. Rapidly synergistic cloud point extraction (RS-CPE) was firstly used to pre-concentrate trace amount of RhB. After a simple data preprocessing which returned to zeros part of the first-order Rayleigh scattering, the second-order calibration method based on the parallel factor (PARAFAC) analysis and alternating trilinear decomposition (ATLD) algorithm was used to deal with EEMF data. Via the introduced "second-order advantage", accurate concentration of the analytes of interest could be obtained even in the presence of unknown interferences. The results demonstrated that the three-dimensional EEMF with second-order calibration method is a powerful tool for the detection of trace amount of RhB in Paprika, and medlar samples, and could be applied to more complex matrices. |
