Discrimination of different type of meats using laser induced breakdown spectroscopy and chemometric techniques

Laser-induced breakdown spectroscopy (LIBS) is an analytical technique used for the identification of elements by analysing the emission line spectrum from samples. In this research, the possibility of classification of raw meat species based on emission spectra by using laser induced breakdown spectroscopy (LIBS) and chemometric techniques such as principal component analysis (PCA) and support vector machine (SVM) were implemented. An experimental setup was developed using Q-Switched Nd:YAG laser operating at 1064nm (208mJ per pulse) and a spectrometer connected to a fiber optic in order to collect the atomic emission. Different types of muscle tissues (beef, mutton, pork, fish, and chicken) were prepared as samples for the ablation process and the procedure for pork sample followed a specific guideline. The LIBS experiment was able to detect the elements in the meat samples such as magnesium, iron, calcium, sodium, carbon, nitrogen, and hydrogen. The raw spectra data were preprocessed and grouped into six datasets for PCA and SVM analysis. Standard ratio combination dataset showed the best result of PCA with variance of 99.8% which were later used for SVM classification. In SVM classification, the maximum accuracy of 89.33% was achieved by using a splitting ratio of 70:30 and linear kernel. The results obtained suggest a successful classification on the target tissues with high accuracy. This is valuable for an automatic discrimination in food analysis

Sensitivity improvement in a fiber macrobending refractive index sensor

In this paper, sensitivity improvement in a fiber macrobending refractive index sensor is studied and an improved sensor model is proposed. The sensitivity can be improved by increasing the evanescent field produced by the fiber when it is bent. Theoretically, an increase in bending loss will increase the evanescent field region. The parameters that affect the bending loss are bending radius of the fiber, number of wrapping turns and critical radius of curvature (Rc). From the theoretical analysis results, a refractive index sensor with improved sensitivity is designed by using values from the analysis as a guideline: bending radius = 5.5 mm, number of wrapping turns = 1 - 5 turns and Rc = 5 - 13 mm. The proposed sensor uses a single mode fiber with an NA of 0.2 where the fiber has a bending radius limit of 5 mm. The cladding at the sensing part of the fiber is removed and the sensor probe is U-shape with several numbers of turns. The proposed sensor is expected to provide high sensitivity with a simple sensor configuration

Comparison of single pulse and double simultaneous pulse laser induced breakdown spectroscopy

A simple and cost-effective variant of laser induced breakdown spectroscopy is presented that involves a double simultaneous pulse configuration employing a single laser source. Its performance is compared with conventional single pulse configuration. Double simultaneous pulses were accomplished by splitting a Nd:YAG laser (1064 nm, 6 ns, 360 mJ) beam into two components that were focused on the sample surface to produce two concurrent breakdowns. Experiment was repeated for single pulse and double simultaneous pulses under different ambient pressures. The performance was evaluated on the basis of self-absorption, signal-to-noise ratio (SNR), and relative standard deviation (RSD) of the Mg II doublet (280.2704 nm, 279.553 nm). Optically thin emission lines of better profiles with higher signal-to-noise ratio resulted from double simultaneous pulses. The lowest relative standard deviations obtained by single pulse and double simultaneous pulse configurations were 18.89% and 12.01%, respectively. In fact, double simultaneous pulses have performed better than single pulse in all respects within the studied regime