Determination of Trace Cr(VI) with Diphenylcarbazide by μFIA–Thermal Lens Microscopy

Abstract

The optimum reaction parameters for the interaction of hexavalent chromium [Cr(VI)] with diphenylcarbazide in microfluidic chips (μFIA) with thermal-lens microscopic detection were selected. The characteristic feature of the applied flow scheme is the injection of the reagent into the stream containing the test metal, which enables in-field and real-time monitoring of Cr(VI) simply by flowing the sample continuously through the microchip. The limit of detection of Cr(VI) under the selected conditions (signal generating wavelength, 514.5 nm; excitation power, 100 mW; detection position, 10 cm downstream from the mixing zone of the microchip; flow rate 10 μL min -1 ; injection volume, 1.4 μL) is 15 ng mL -1 (2.9 × 10 -7 mol L -1 ). The linear range is 40 ng mL -1 -10 μg mL -1 with a relative standard deviation no higher than 10% in the concentration range 0.1-1 μg mL -1 . The online monitoring by this scheme provides the possibility of up to 360 analyses per hour.

Thermal lensing: outside of the lasing medium

“…For instance, Liu and Franko [68] reformulated the TL theory by taking into account the divergence of the HL beam at the sample, which is inevitably nontrivial in strong focusing cases, as in microfluidic TLM setups. Next, the same setup, as used by them [68] to check their theory, was used by Gorkova et al [69] to present the possibility of determination of trace concentrations of chromium(VI) using a micro-flow-injection analysis-TLM measurement procedure. In such setup, the sample volume is limited and it is injected into a carrier stream that flows through the micro-channel of the measurement chip.…”

Improvement in the Chromium(VI)-Diphenylcarbazide Determination Using Cloud Point Microextraction; Speciation of Chromium at Low Levels in Water Samples

“…In recent years, this methodology has been used for the extraction of various Cr 6+ complexes, measuring the final concentration of the metal in the condensed phase by means of an atomic [ 26 , 27 , 28 , 29 , 30 , 31 ] or molecular techniques [ 11 , 16 , 26 , 32 , 33 , 34 ].…”

From Protohypericin to Hypericin: Photoconversion Analysis Using a Time-Resolved Thermal Lens Technique

“…[31][32][33][34] The method can also be used to study thermal and optical properties of polymers and glasses, [35][36][37][38][39][40] in addition to the pharmacological and biological applications and determination of heavy metals. [41][42][43][44][45] There have been several reviews on TL applications in the literature. [46][47][48][49][50] In this work, we use the high sensitivity and remote measurement characteristics of the time-resolved TL technique to investigate the photoconversion of pHyp to Hyp.…”