Synchronous fluorescence and absorbance dynamic liquid drop sensor for Cr(vi) determination at the femtomole level

Abstract

A novel synchronous fluorimetric and absorptiometric technique based on dynamic liquid drops coupled with flow injection is described for the determination of chromium(VI) in aqueous solutions. Drops formed continuously at the end of a quartz capillary tube serve as reactor and optical cell. The reaction between chromium(VI) and 3,3',5,5'-tetramethylbenzidine dichloride (TMB-d) results in a significant decrease in fluorescence and transmitted light intensity, proportional to the logarithm of the concentration of chromium(VI). The transmitted light and fluorescence emission are detected in counter and perpendicular positions of the excitation light by a photomultipler tube and photodiode, respectively. In HCl-NaOAc buffer solution (pH 3.29), the sensor has a wide linear calibration range of 2 x 10(-8)-1 x 10(-4) mol l(-1) chromium(VI) with an absolute mass detection limit of 12.88 fmol.

Colorimetric detection of hypochlorite in tap water based on the oxidation of 3,3′,5,5′-tetramethyl benzidine

“…TMB is a type of colourless peroxidase substrate and has been widely employed in the colorimetric detection of various analytes, due to the striking colour difference between TMB and its oxidized form. [16][17][18] Dilute NaClO solution is also colourless. However, on mixing TMB with ClO À at pH 4.0 the mixture readily changes from colourless to blue, due to oxidization of TMB by ClO À .…”

“…The oxidation process involves the formation of a semiquinone imine radical cation, which can reversibly form a blue charge-transfer complex with the parent diamine (Scheme 1). 17,18 The maximum absorption peak of the oxidized TMB solution is centred at around 655 nm. The obvious colour change from colourless to blue is easily recognized by the naked eye (Fig.…”

Recent Development in Optical Chemical Sensors Coupling with Flow Injection Analysis

“…A novel synchronous fluorimetric and absorptiometric technique based on dynamic liquid drops coupled with flow injection is described for the determination of Cr(VI) in aqueous solutions [63]. Drops formed continuously at the end of a quartz capillary tube.…”

Sampling and analysis considerations for the determination of hexavalent chromium in workplace airThis article was prepared by governmental employees of the United States of America and the United Kingdom as part of their official duties, and legally may not be copyrighted in the USA or the UK.

“…Of these separation techniques, IC is undoubtedly the most popular method for routine speciation analysis of environmental and other samples, not only for chromium species but for other metal ions as well. 124 Flow-injection analysis (FIA) methods have been developed, for instance FIA using onstream sample preparation with photometric, 85,86 fluorimetric, 101,102 or electrochemical 115 detection. FIA techniques offer possibilities for field-portable measurement of Cr(VI).…”