High sensitivity thermal lens microscopy: Cr-VI trace detection in water

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPIn this work, a low detection limit for hexavalent chromium in water of parts per trillions (21 ng/L) was achieved using a micro -spatial thermal lens spectroscopy setup with coaxial counter -propagating pump and probe laser beams and an integrated passive optical Fabry-Perot resonator, aided with a well -established diphenyl carbazide colorimetric method. Cr-VI concentrations in the range of mu g/L, i.e. well -below the toxicity thresholds in humans and animals (26 and 190 mg/L respectively) and below those delimited by international regulations for drink water (similar to 0.05-0.5 mg/L), have been obtained by measurements in bottled and tap water samples. The developed thermal lens microscope is also capable to detect Cr-VI directly in potassium dichromate solutions using pump beam wavelengths within the very low optical absorption region in the visible part of the spectrum, i.e., without the use of any calorimetric method.170260265CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPSem informaçãoSem informaçãoThis work was supported by Research Grants SIP-IPN 2014006, 20150390, 20160144 and CONACyT 2015-02-1042 and 264093. H. Cabrera gratefully acknowledges ICTP TRIL as well as the Associateship Programs. A. M. M. acknowledges the support of the Brazilian Agencies CNPq and FAPESP. The support of COFAA-IPN by the SIBE and BEIFI programs is also acknowledged