LIBS—An efficient approach for the determination of Cr in industrial wastewater Nilesh K. Rai, A.K. Rai ∗ Laser Spectroscopy Research Laboratory, Department of Physics, University of Allahabad, Allahabad 211002, India Abstract In the present paper, LIB spectra of different water samples having varying concentration of Cr (certified reference material, CRM) have been recorded by using liquid jet (fabricated in our laboratory) configuration. Calibration curves for different atomic lines of Cr are compared and it is found that calibration curve for Cr II (283.5 nm) atomic line is the best in terms of the Limit of detection (LOD) which is found to be 30 ppm. This calibration curve has been used for quantification of Cr in wastewater collected from Cr-electroplating industry where the concentration of Cr is found to be 1500 ppm. Its removal can be planned by biological system, which is in progress. Keywords: Cr; Hazardous metal; Jet; LIBS; Liquid 1. Introduction An unfortunate consequence of industrialization and indus- trial production is the generation and release of toxic waste which pollute our environment. The electroplating industry is one of major contributors for polluting the water and soil with poisonous elements like Pb, Cr, Cd, etc. The waste water from different type of electroplating industries such as Ni- electroplating, Cr-electroplating, Cu-electroplating, etc. were found very rich in the corresponding elements. Thus, the environmental challenges for the electroplating industry are associated with wastewater generation contaminated with toxic metals such as Ni, Cr, etc. and hence there is a great demand for the development of an analytical tool which could determine the heavy metal content in waste water accurately and rapidly, with- out any sample preparation. Also, the removal of such hazardous metal from wastewater is vital to make it eco-friendly. Abbreviations: CCD, charge couple device; CRM, certified reference mate- rial; Cr, chromium; LIBS, laser-induced breakdown spectroscopy; LOD, limit of detection; LTSD, lens to sample distance. ∗ Corresponding author. Tel.: +91 532 2460993. E-mail addresses: nileshkrai162@yahoo.com (N.K. Rai), awadheshkrai@rediffmail.com (A.K. Rai). In recent years, laser-induced breakdown spectroscopy (LIBS) is emerging as an important tool for the monitoring of trace pollutants in environment (liquid, soil, etc.) [1,2]. The principle of LIBS is based on the spectral analysis of radiation emanating from micro-plasma generated by focus- ing a high power pulsed laser beam on to surface of the sample. The characteristic emission from plasma provides fin- gerprint of constituents of target material. LIBS technique is unique in the sense that it requires no sample preparation and its capability of remote and in situ analysis of material in any phase (solid, liquid or gas) [3–8]. This is in sharp con- trast with conventional analytical techniques that require time consuming sample preparation and can be employed only in laboratory. Laser produced plasma of solid and liquid mate- rials are also of much interest, especially in the field of laser diagnostic, thin film growth, and trace element analysis [9–12]. The present work is motivated by the need for reliable Cr monitoring during the treatment of wastewater from different industries. A home made liquid jet has been chosen to record laser-induced breakdown (LIB) spectra with greater sensitivity. Calibration curves have been drawn for different Cr lines, by recording the LIB spectra of water with varying concentration of Cr and the best calibration curve has been used for quantification of Cr present in wastewater collected from the Cr-electroplating