رسائل ماجيستير
English
2016
Development of UV Pulsed Laser Induced Breakdown using Spectroscopy (LIBS) for Assessment of Toxic elements and Plasma Parameters in Food Products
حبيب الله يوسف بابانجيري, محمد أشرف جندال
كلية العلوم-جامعة الملك فهد للبترول والمعادن · السعودية
In this study, we assembled a highly sensitive Laser Induced breakdown spectrometer for the detection of nutritional and toxic elements in commercially available food products which are often consumed by the population around the world and most especially in the kingdom of Saudi Arabia. Some of the toxic element are highly carcinogenic and life threatening even at low concentrations causing dangerous diseases. In light of this, there is an increase in demand to device a suitable and effective technique to detect and quantify the level of nutritional and toxic elements in them. Laser Induced Breakdown spectroscopy (LIBS) were used for spectroscopic analysis of tea, cigarette, smokers & non-smoker’s teeth, and date fruit. The LIBS sensitivity was improved by finding the LIBS signal intensity dependence on time delay and laser fluence under ambient conditions. Plasma parameters such as electron temperature Te and electron number density Ne were estimated for the different samples using Boltzmann plot and Stark broadening profile respectively. With the aid of estimated plasma parameters we were able to validate if our plasma was in local thermodynamic equilibrium (LTE). For tea analysis, LIBS spectra for six brands of tea samples in the wavelength range of 200-900 nm region was recorded and all elements present in Tea were identified as well their spectral transition assignment was also conducted. Prior to determination of concentration, calibration curves were drawn for each element using standard samples prepared in known concentration in the tea matrix. The concentrations of iron, chromium, potassium and bromine detected in all tea samples were between 378-656, 96-124, 1421-6785 and 99-1476 ppm, respectively. To further confirm the accuracy of our LIBS results, we determined the concentration of each element present in tea samples by using standard analytical technique like ICP-MS. The concentrations detected with our LIBS system are in excellent agreement with ICP-MS results. In order to achieve the high sensitivity required for the determination of trace amounts of fluoride in cigarettes and eventually the best limit of detection, the experimental parameters (influence of incident laser energy on libs signal intensity and time response of plasma emission) were optimized. In addition, the plasma parameters like electron temperature and electron density were evaluated using Boltzman’s plot for cigarettes tobacco for the first time. Along with the detection of flourine, other trace metals like Ba, Ca, Ni, Cu and Na were also detected in cigarettes. The concentration of fluorine in different cigarettes tobacco samples was 234 ppm, 317ppm, 341 ppm and 360 ppm respectively, which is considered to be much higher than the safe permissible limits. As for the detection of toxic elements in smokers and non-smokers’s teeth, LIBS was assembled and optimized to detect the level of toxic elements such as lead, cadmium and arsenic present in the roots of extracted teeth of smokers and nonsmokers. The Pb, Cd and As concentrations in smoker group were 34 - 55, 0.33 - 0.51 and 0.91-1.5 ppm respectively, compared to the same for non-smoker group, which was 23 - 29, 0.26 – 0. 31, and 0.64 - 11 ppm range and 0.17- 0.31, 0.01- 0.05 and 0.05 -0.09 ppm range for control group. In order to substantiate the LIBS results standard Inductively Coupled Plasma (ICP) was carried out and found to be in good agreement with LIBS data.