Laser-induced breakdown spectroscopy and inductively coupled plasma-mass spectrometry for determination of Cr in soils from Brits District, South Africa

A A Ambushe,A Du Plessis,R I Mccrindle

doi:10.4314/bcse.v29i3.3

Abstract

Laser-induced breakdown spectroscopy (LIBS) is an emerging analytical technique, which can be used to perform elemental analysis of any material, irrespective of its physical state. In this study, the LIBS technique has been applied for quantification of total Cr in soil samples collected from polluted areas of Brits, North West Province, South Africa. A Q-switched neodymium-yttrium aluminium garnet (Nd-YAG) laser (10 Hz, λ = 1064 nm) was employed for generation of a laser-induced plasma on the surface of the soil sample. The atomic emission lines were recorded using an Andor Shamrock SR-303i spectrometer, fitted with an intensified charge-coupled device (ICCD) camera. Detailed investigation of experimental parameters such as gate delay time, gate width and laser pulse energy was conducted. Soil samples were dried, finely ground, sieved and thereafter pelletized before LIBS analysis. Calibration curve for the quantification of Cr was constructed using certified reference materials of soils and sediments. The concentrations of Cr in soil samples varied from 111 to 3180 mg/kg. In order to test the validity of the LIBS results, inductively coupled plasma-mass spectrometry (ICP-MS) was also employed for determination of Cr. The results obtained using LIBS were found to be in good agreement with those of ICP-MS. KEY WORDS : Chromium, Direct determination, Soil, LIBS, ICP-MS Bull. Chem. Soc. Ethiop. 2015 , 29(3), 357-366. DOI: http://dx.doi.org/10.4314/bcse.v29i3.3

Highlights

Pollution of soils by heavy metals such as Cr is a major public concern
The number of samples is limited in this work, the current study provides an alternative technique for detection of chromium from a complex soil matrix without the need to digest soil samples compared to inductively coupled plasma-mass spectrometry (ICP-MS)
The concentrations of Cr in soil samples estimated by Laser-induced breakdown spectroscopy (LIBS) agreed with the concentrations found with an ICP-MS

Summary

Introduction

Pollution of soils by heavy metals such as Cr is a major public concern. In particular, the contamination of agricultural soils with heavy metals results in accumulation of toxic metals in food crops. The contamination of soil with Cr could be due to industrial processes such as electroplating, tanning, manufacture of pigments and chemicals, mud from oil drilling, textile dying, steel, paint and fertilizer production as well as wood preservation [3,4,5,6]. During such industrial activities, Cr compounds are introduced into the soil and can result in significant adverse biological and ecological effects [7]. The contamination of soil by Cr has become a great threat for humans and animals

Objectives

Conclusion