Research And Application Of Laser-induced Breakdown Spectroscopy For Human Hair Analysis

Hair is one of the most ideal biomarkers for monitoring human health and environmental risks through the determination of elements.Traditional element detection methods have problems such as complex sample preparation and time-consuming detection.In recent years,laser-induced breakdown spectroscopy(LIBS)has received extensive interests in the biomedical field due to its advantages such as simple pretreatment,rapid detection,minimal damage,and simultaneous analysis of multi-element.However,LIBS has the problem of low sensitivity and accuracy in the direct detection of hair due to the matrix effect and lack of standard sample.Therefore,two rapid analysis methods,the ultrasonic-assisted alkali dissolution method combined with LIBS(UAAD-LIBS)and the calibration-free LIBS(CFLIBS)assisted with the standard reference line method were proposed to qualify trace elements and macro elements accurately.The main achievements and innovations are as follows:(1)A simple and low-cost method of UAAD-LIBS was proposed to improve the low detection sensitivity of trace elements in hair using LIBS.The quantitative effect of Zn and Cu elements in hair which was dissolved in three reagents(strong alkali,strong acid,and deionized water)were analyzed by using ultrasonic-assisted dissolution combined with solid-liquid-solid transformation method for sample preparation.The UAAD-LIBS method had the best quantitative effect,and the limits of detection(Lo Ds)for determining Zn and Cu elements could reach to 0.3517 ?g/g and 0.0146 ?g/g,respectively.Furthermore,the relative errors of Zn and Cu between UAAD-LIBS and ICP-OES for three actual samples were less than 7.6% and 4.9%.These results show that UAAD-LIBS is an effective detection method which has high detection sensitivity and accuracy.(2)Due to the lack of matching standard samples during directly detecting macro elements in hair,CF-LIBS was applied to the quantitative analysis of hair without standard samples.Furthermore,only few spectral lines of elements could be observed in hair,making it challenging to calculate the macro elements directly by CF-LIBS.Therefore,CF-LIBS assisted with the standard reference line method was used to quantify the content ratio of Ca/Na and Mg/Na in hair.And this method was further applied to fingernails for verification.The results showed that the relative errors between the quantitative results of CF-LIBS and ICP-OES were less than 10% in hair and nails,which verified the accuracy of this method.(3)Studies have shown that the rapid detection of blood by LIBS technology could achieve the initial diagnosis of cancer.Based on the previous research,the feasibility of LIBS for hair detection in the preliminary identification of nasopharyngeal carcinoma was explored.For the hair spectra of nasopharyngeal carcinoma and healthy volunteers collected by the autofocus system,the classification accuracy of PCA-KNN and PCA-SVM were92.75% and 93.20%,respectively.The results indicate that the detection result of LIBS for human hair can provide reference for primary screening of disease.In summary,UAAD-LIBS and CF-LIBS assisted with the standard reference line method were proposed to quantify the content of trace elements and constant elements in hair,which improved the sensitivity and accuracy of the quantitative analysis.And LIBS for hair analysis was applied to the identification of nasopharyngeal cancer,indicating that the application of LIBS for disease diagnosis was feasible.