Detection of Nutrition and Toxic Elements in Dry Milk Powders Available in Pakistan Using Laser Induced Breakdown Spectroscopy

Abstract

In this work, qualitative as well as the quantitative study of nutritional and trace toxic metals in various dry milk powders (local and branded) available in Pakistan was accomplished by calibration free-laser induced breakdown spectroscopy (CF-LIBS). To analyze the optical emission spectra, a pulsed Nd-YAG laser was utilized to produce micro-plasma on the surface of samples. The emitted light was acquired with a dedicated spectrometer for subsequent analysis and quantification of the species in the target. Ca, K, Mg, Na, P, Zn, Al, and S were identified as nutritional elements, while Cd, Cr, Cu Mn, and Ni as heavy metals. Our LIBS system was optimized by parametric dependence study. The average plasma temperatures were estimated using Boltzmann plot method for all types of milk powder between 8000 and 95,000 K. The electron number density was determined from the Stark broadened line profile of balmer hydrogen line (H-alpha) between 1.12 × 1017 cm−3 and 1.61 × 1017 cm−3. The emission lines used in CF-LIBS were characterized for the effect due to phenomenon of self-absorption but were found insignificant. Furthermore, the concentrations determined using CF-LIBS were compared to the abundance of identical (duplicate) dry milk powder samples obtained using a standard analytical tool like inductively coupled plasma-optical emission spectroscopy. Both the results were in outstanding harmony. Our study showed that LIBS is a powerful and rapid approach to quantify the chemical concentrations of food products.