Detection of trace amount of arsenic in groundwater by laser-induced breakdown spectroscopy and adsorption

•Arsenic in water at 1 ppm level was detected by a combination of LIBS and adsorption by ZnO.•This is hitherto known the lowest detection limit of arsenic in water by LIBS, though at the expense of speed of detection.•A combination of adsorption by ZnO and pre-boiling lowered the detection limit even below 100 ppb.•Pure ZnO and charcoal are better adsorbent of arsenic compound in water than natural absorbent like tea leaves, bamboo slice.•Pure ZnO is a better adsorbent of arsenic in water than charcoal.

LIBS technique coupled with adsorption has been applied for the efficient detection of arsenic in liquid. Several adsorbents like tea leaves, bamboo slice, charcoal and zinc oxide have been used to enable sensitive detection of arsenic presence in water using LIBS. Among these, zinc oxide and charcoal show the better results. The detection limits for arsenic in water were 1 ppm and 8 ppm, respectively, when ZnO and charcoal were used as adsorbents of arsenic. To date, the determination of 1 ppm of As in water is the lowest concentration of detected arsenic in water by the LIBS technique. The detection limit of As was lowered to even less than 100 ppb by a combination of LIBS technique, adsorption by ZnO and concentration enhancement technique. Using the combination of these three techniques the ultimate concentration of arsenic was found to be 0.083 ppm (83 ppb) for arsenic polluted water collected from a tube-well of Farajikandi union (longitude 90.64°, latitude 23.338° north) of Matlab Upozila of Chandpur district in Bangladesh. This result compares fairly well with the finding of arsenic concentration of 0.078 ppm in the sample by the AAS technique at the Bangladesh Council of Scientific and Industrial Research (BCSIR) lab. Such a low detection limit (1 ppm) of trace elements in liquid matrix has significantly enhanced the scope of LIBS as an analytical tool.