Bubble profile analysis tensiometer

Using the drop and bubble profile analysis tensiometer PAT-1 (SINTERFACE Technologies, Berlin, Germany) it is possible to perform dilational rheology studies of surfactant solutions at low frequencies. 

Here we report on an adsorption and surface rheology study with /i-lacto-globulin (jS-LG) and /J-casein (jS-CS) at the water/air interface using essentially a newly designed profile analysis tensiometer that allows us to investigate adsorption processes at the surface of drops as well as bubbles. The differences in the interfacial behaviour of the two proteins is discussed. 

Figure 3 contains dynamic data for ff-LG received by three methods the maximum bubble pressure method in the time range 0.001 s to 100 s, the drop volume method for times in the range 5 s to 500 s, and the profile analysis tensiometer PAT l in the time range from 10 s up to several hours. 

The graph in Fig. 41 shows the dynamic surface tensions of a mixtured solution of CioDMPO and C14DMPO measured with the maximum bubble pressure method BPAl (O) and profile analysis tensiometer PATl ( ). The theoretical curves shown were calculated due to the adsorption kinetics model for surfactant mixtures discussed above (Miller et al. 2003). 

The fundamentals of drop and bubble shape analysis have been discussed in detail above. In the next section examples are given to demonstrate the various applications of the profile analysis tensiometer. Besides dynamic surface and interfacial tensions, results are shown for trapezoidal and sinusoidal relaxation experiments from which the dilational elasticity can be derived. The experiments selected are not only for model surfactants of high chemical purity but also for technical surfactants for which effective data can be deduced. 

Automated Droplet Tensiometer. Surface tension and surface dilational moduli were measured by an automated droplet tensiometer (ADT) (IT concept, France) as a function of ageing time of the droplet.22 Surface tension was determined by drop shape analysis of a gas bubble formed in a cuvette containing the protein solution. The bubble was illuminated by a uniform light source and its profile imaged and digitised by a CCD camera and a computer. The profile was used to calculate the surface tension using Laplace s equation. The... 

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