Quenched phosphorescence as alternative detection mode in the chiral separation of methotrexate by electrokinetic chromatography

Quenched phosphorescence was used, for the first time, as detection mode in the chiral separation of methotrexate (MTX) enantiomers by electrokinetic chromatography. The detection is based on dynamic quenching of the strong emission of the phosphorophore 1-bromo-4-naphthalene sulfonic acid (BrNS) by MTX under deoxygenated conditions. The use of a background electrolyte with 3 mg/mL 2-hydroxypropyl-β-cyclodextrin and 20% MeOH in 25 mM phosphate buffer (pH 7.0) and an applied voltage of 30 kV allowed the separation of l-MTX and its enantiomeric impurity d-MTX with sufficient resolution. In the presence of 1 mM BrNS, a detection limit of 3.2 × 10−7 M was achieved, about an order of magnitude better than published techniques based on UV absorption. The potential of the method was demonstrated with a degradation study and an enantiomeric purity assessment of l-MTX. Furthermore, l-MTX was determined in a cell culture extract as a proof-of-principle experiment to show the applicability of the method to biological samples

Design optimization and test of the novel FeTu ‘compander’, utilising organic fluids within a closed cycle for HVACR applications

Abstract HVACR performance is influenced by the efficiency of the compression and expansion process. The ability to operate oil-free; with non-toxic, inert, natural working fluids such as air or CO2 holds high environmental value. This paper presents data of the FeTu™ compander operating in a closed cycle, for means of heating and cooling. A novel system, where compression and expansion is a continuous and simultaneous process; inherently regenerating energy to assist the compression process by expanding within a positive displacement chamber. This study documents the oil-free performance with organic working fluids pertaining to HVACR applications. Commercial 1D modelling software; GTSuite (GTS) is used to optimise cooling capacity (Q) and Coefficient of Performance (CoP). Different volume ratios (VR), pre-charge pressures, temperature inputs (ΔT) and running speeds are analysed. A multi-faceted test rig is built to compare and validate all performance data against the GTS fluid model which, once calibrated, can then be used with a high degree of certainty in predicting the performance of other applications and ΔTs. Increasing the system pre-charge pressure has a proportional impact on capacity, so this phenomenon is tested to consider the conflicting impacts of higher pressure against increased viscosity, with respect to volumetric efficiency. The CoP of the system ranges from 1 to 5 across typical HVACR ΔTs. Low VR offers highest CoP but lowest Q, so the optimal trade-off is explored. The strengths &amp; weaknesses are then comparatively documented against incumbent vapour cycle systems.</jats:p

The roticulating concept air compressor: experimental and numerical investigation

Abstract This paper documents the first prototype tests of the FeTu bare-shaft oil-free air compressor, conducted over a one-year study at the University of Bath, with funding support from Innovate UK. Giving feasibility to the concept and to provide an initial indicator of its performance, in terms of pressure capability, isentropic efficiency and specific power demand as an oil-free air compressor. A range of 6 units in total were validated on a continuous flow test-rig, with variations on internal sealing, internal clearance, and Non-Return Valve (NRV) settings, to assess their impact on volumetric efficiency, in pursuit of an optimal design. Tests covered a speed range of 100 rpm-1500 rpm and reached discharge pressures up to 6 barg, results indicated that the compressor can maintain a 50% torque-based efficiency between a pressure ratio (PR) of 1.5 to 2.8. Tests reveal low compressed gas temperature of 125ºC at 2.8PR, which gave rise to a high isentropic efficiency of over 80%, therefore specific power was adopted as the main Key Performance Indicator (KPI).</jats:p