In both cases the dynamic equilibrium will be established by purging interior of the tubular membrane by a gas of known composition.Discontinuous (isochoric) methodAt time t = 0 (start of pressure measurement) the tubular membrane will be closed at its ends by valves.We assume that superposition holds for the permeation of the different gas components (index ��k��) of a multi-component system (e.g., soil air). Applying Dalton’s law the resulting isochoric pressure change inside the tube isdpdt=��k=1ndpkdt=gPspa��k=1nfks(��ka?�æ�ki),(2)where fks = Pk/Ps is the perm-selectivity coefficient (defined with regard to a component k = s of the purging gas) and the geometrical properties of the tubular sensor are combined to the geometry factor g [1/m2]g=1V02��?Lln(Ra/Ri).
(3)Recording the time-dependent pressure curve for t > 0 and approximating the discrete readings by a polynomial Fp = ��p ap ? tp the pressure change is determined by the limiting valuea1=dpdt=dFpdt|t��0,(4)where the dynamic equilibrium was still valid.Continuous (isobaric) methodSteady state is continuously conserved by purging the tubular membrane. In analogy to Equation (2) the volume change near the dynamic equilibrium isdVdt=��k=1ndVkdt=V0p0dpdt.(5)The diffusive gas flow through the membrane can be measured in terms of the change of the purging gas flow dV/dt = Qout �C Qin [m3/s] between the inlet (Qin) and the outlet (Qout) of the tubular me
Electrogenerated chemiluminescence (also called electrochemiluminescence and abbreviated ECL) involves the generation of species at electrode surfaces that then undergo electron-transfer reactions to form excited states that emit light [1].
Since the first detailed ECL studies by Kuwana, Hercules and Bard et al. in the mid-1960s [2-4], the ECL technique has become a very powerful analytical tool and has been widely used in the areas of, for example, immunoassay, food and water testing, and biowarfare agent detection. ECL detector has also been successfully exploited as a detector in flow injection analysis, high-performance liquid chromatography, capillary electrophoresis, and micro total analysis. Some excellent reviews focused on mechanism, type and its application of ECL were presented from 2004 to 2008 [1, 5-10].
Biosensors are defined as analytical devices incorporating a biological material, a biologically derived material or a biomimic Brefeldin_A intimately associated with or integrated within a physicochemical transducer or transducing microsystem, which may be optical, electrochemical, thermometric, piezoelectric, magnetic or micromechanical detector [11]. The ECL detection technique has many distinct advantages over other detection techniques [12]. For example, compared with the fluorescence technique, the ECL technique does not involve a light source and, hence, the attendant problems of scattered light and luminescent impurities.