Cavity enhanced liquid-phase stopped-flow kinetics

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 αmin(t), was 1.35 × 10−5 cm−1 Hz−1/2. 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

Cavity Enhanced Immunoassay Measurements in Microtiter Plates using BBCEAS

We report on the first detailed use of broadband cavity enhanced absorption spectroscopy (BBCEAS) as a detection system for immunoassay. A vertical R ≥ 0.99 optical cavity was integrated with a motorised XY stage, which functioned as a receptacle for 96 well microtiter plates. The custom built cavity enhanced microplate reader was used to make measurements on a commercially available osteocalcin sandwich ELISA kit. A 30 fold increase in path length was obtained with a minimum detectable change in the absorption coefficient, αmin(t), of 5.3 × 10-5 cm-1 Hz-1/2. This corresponded to a 39 fold increase in the sensitivity of measurement when directly compared to measurements in a conventional microplate reader. Separate measurements of a standard STREP-HRP colorimetric reaction in microtiter plates of differing optical quality produced an increase in sensitivity of up to 115 fold compared to a conventional microplate reader. The sensitivity of the developed setup compared favorably with previous liquid-phase cavity enhanced studies and approaches the sensitivity of typical fluorometric ELISAs. It could benefit any biochemical test which uses single pass absorption as a detection method, through either the label free detection of biologically important molecules at lower concentrations or the reduction in the amount of expensive biochemicals needed for a particular test, leading to cheaper tests

CFD study of filtration process in moulded filters within a vacuum pump

Air/Oil filtration through filters is commonly utilised in the vacuum industry where oil lubricated pumps are used across a number of different applications such as food and packaging, industrial, pharmaceutical, R&D, forming and drying. The air/oil filters are crucial in the reduction of exhaust emissions, which, when suspended as fine particulate matter can cause great harm to the environment, climate, equipment life and public health. However, the behaviour of flow through the filters is not fully understood and much of the design and development work is based on historical know-how and experimental studies. Computational Fluid Dynamics (CFD) is a powerful tool to understand the flow characteristics and droplet trajectory through the filters which is challenging through experimental techniques. In this study, a CFD model is developed by using the commercial ANSYS FLUENT code. Oil droplets from the pump entering the filter are treated as a discrete phase. Euler-Lagrangian frame is used to characterise the multiphase flow, K-Ɛ as a turbulence model, Rosin-Rammler distribution of oil droplets, User Defined Functions (UDF) are written for droplet injection, distribution and deposition. Various methodologies and tests were developed to obtain the required data to feed into the model and validate the data predicted by the computational model. The obtained computational data agrees well with the experimental data