Analyzing Trace Substances Existed In Mixture By Two-Dimensional Correlation Fluorescence Spectrometry

Fluorescence spectrum is an effective method for the detection of trace fluorescent substances.However,in practical situations,the following problems will be encountered: In many cases,however,the characteristic peak of one solute(denoted as A)overlap severely with the characteristic peak of another solute(B).Moreover,the content of B is overwhelmingly larger than that of A.Consequently,identification of the A from the spectrum of a single solution sample is almost impossible since the characteristic signal of A is completely masked by the signal of B.The spectral behavior of many fluorescent compounds observes the Kasha's rule,that is to say,a series of fluorescent emission spectra of a sample solution can be obtained using excited light of different wavelengths.theoretically:When a and b coexist,the fluorescence emission spectrum is the linear sum of the fluorescence emission spectra of the two fluorescence substances.The relative contributions of a and b to the total spectrum are different when the sample is irradiated with excitation light of different wavelengths.The relative contributions of A and B to the total spectrum are different,and there should be differences in fluorescence spectral peak types.For many systems,B is extremely low,As a result,the fluorescence emission spectra obtained under different excitation wavelengths are not significantly different in the spectrum.This makes it a great challenge to detect B in the strong background of A.Two-dimensional correlation spectroscopy(2D-COS),provides a feasible way to address the problem.By applying external perturbation to the sample and combining the method of matrix calculation,the subtle signal differences and changes that are difficult to be observed in the spectrum can be reflected in the two-dimensional asynchronous correlation spectrum.In this experiment,the luminescence spectra of a series of fluorescence substances were detected,and two fluorescence substances in accordance with Kasha rule,namely Eosin Y and Bromocresol green,were screened.Because the emission spectra of the two fluorescence substances have a large overlap.The emission spectra of Eosin Y were obtained by changing the excitation wavelength.Matlab program was used to conduct two-dimensional asynchronous correlation processing for these spectral data.It is found that there is no obvious cross peak in the two-dimensional asynchronous spectrum.Similar results were observed in the presence of Bromocresolgreen alone,this indicates that there is no cross peak in solution if only a single substance exists.Different from the above situation,when bromocresol green was added to eosin Y solution,a cross peak appeared on the two-dimensional fluorescence emission spectrum of the mixed system.This cross-peak exists even at low concentrations of Bromocresol green(39.4 nmol/L).The experimental results demonstrate the approach is feasible in real world.