Cavity enhanced liquid-phase stopped-flow kinetics

Abstract

The first application of liquid-phase broadband cavity enhanced spectroscopy (BBCEAS) to the measurement of stopped-flow kinetics is reported. The stopped-flow technique is widely used for the study of the kinetics of fast liquid-phase reactions down to millisecond timescales. UV-visible absorption spectroscopy is commonly used as the detection method. Increased sensitivity can potentially allow reactions which are too fast to be measured, to be studied by slowing down the reaction rate through the use of lower concentration of reactants. A simple low cost BBCEAS experimental setup was coupled to a commercial stopped-flow instrument. Comparative standard absorption measurements were also made using a UV-visible double-beam spectrometer as the detector. Measurements were made on the reaction of potassium ferricyanide with sodium ascorbate under pseudo-first order conditions at pH 8 and pH 9.2 A cavity enhancement factor (CEF) of 78 at 434 nm was obtained whilst the minimum detectable change in the absorption coefficient α(t), was 1.35 × 10 cm Hz. The kinetic data at pH 9.2 was too fast to be measured using conventional spectroscopy, whilst the BBCEAS measurements allowed 30 fold lower concentration of reactants to be used which slowed down the reaction rate enough to allow the rate constant to be determined. The BBCEAS results showed a 58 fold improvement in sensitivity over the conventional measurements and also compared favourably with the relatively few previous liquid-phase cavity enhanced kinetic studies which have been performed using significantly more complex and expensive experimental setups.

Spectral Behaviour of the low concentrations of Coumarin 334 with Broadband Cavity Enhanced Absorption Spectroscopy

“…After that, the cavity enhanced factor values were calculated using the relationship in Eq. 2 below 13 :…”

“…Generally, BBCEAS set up consists of light source, optical cavity contains two high reflectivity dielectric mirrors and a detector with high resolution, which is used to record the absorption spectra. These techniques depend on the use of the optical cavity to improve the interaction of the light with matter by increasing the path length between two high reflectivity dielectric mirrors to increase the sensitivity measurements of the absorption spectra 12,13 . Optical cavity technique applies to HPLC detection 14 , it allows to record the absorption spectrum of the analyte over a wide range of wavelengths.…”

Flow Chemistry in Contemporary Chemical Sciences: A Real Variety of Its Applications

“…The sensitivity of kinetic absorption measurements in ultraviolet (UV)-visible wavelengths can be enhanced by the use of optical cavity-based techniques. The reported low-cost experimental set-up providing broadband cavity enhancement of sensitivity by coupling to commercial stopped-flow instruments allows obtaining even 78-fold enhancement for the measurements at 434 nm, which was employed in the investigation of the kinetics of a potassium ferricyanide reaction with sodium ascorbate [66].…”

Developments in Transduction, Connectivity and AI/Machine Learning for Point-of-Care Testing

“…A 39-fold increase in sensitivity has been demonstrated for a 96 well microtiter plate commercially available osteocalcin ELISA and a 115-fold increase in sensitivity for a commonly used ELISA colorimetric reaction of streptavidin-horseradish peroxidase (STREP-HRP) with Tetramethylbenzidine (TMB) [32]. CEAS has also been demonstrated for stopped flow kinetics [33].…”