Study On Ultra-sensitive Laser Induced Fluorescence Detector

Laser induced fluorescence detection is one of the most sensitive detection methods in trace detection and has important applications in many fields.At the same time,the laser induced fluorescence detector is applied to some more complex environments,which enhanced the requirement for the volume and sensitivity of detectors.This work is to build and evaluate an orthogonal laser induced fluorescence detection device.At the same time,based on the previous research of the group,a small,low-cost confocal laser-induced fluorescence detection device was optimized and evaluated to achieve the standard of trace detection in such indicators as sensitivity and stability.Both detectors take laser as the light source,photoelectric amplifier as the detector,capillary as the detection cell,and flow injection as the way to evaluate the overall performance of the instrument,and obtain a high sensitivity.The research results are mainly as follows:A laser induced fluorescence detector based on orthogonal structure was built,and the capillary was used as the detection cell to optimize the inner and outer diameters of the excited fiber and the collecting fiber.And the distance between the excitation and collection of the fiber and the capillary flow cell.It is also compared whether adding a ball lens between the excitation fiber and the flow pool can effectively improve the sensitivity of the instrument.By means of flow injection,the detection limit of the instrument was measured and the sensitivity level of the instrument was reached.Based on the team work before,this work optimized and evaluated a confocal structure of laser induced fluorescence detector,the parameters of the optical element is optimized in instrument,optimize content respectively: the dive current of laser diode,the magnification and the working distance of the objective,the combination excitation and emission filter,and added a spherical dichroic reflector design,the diameter of aperture was optimized.Comparing the photoelectric amplifier with photomultiplier tubes under the same conditions in this device,made the influence of the signal to noise ratio in the device.Finally,evaluated the sensitivity and linear response of the optimized detector by flow injection,and a high level of detection sensitivity was obtained in the field.To sum up,the work content of this project is to build an orthogonal laser-induced fluorescence detector with the advantages of simple structure and small volume,and to optimize and evaluate a confocal laser-induced fluorescence detector.At the same time,a good detection SNR was obtained.