Triolein impurities

A thin film of oil-like material was visible after 28 d on the exterior surfaces of the SPMD membrane. Analysis of this film indicated that the triolein impurities, oleic acid and methyl oleate, were the major constituents. This external lipid film (Petty et al., 1993) appeared to contain imbibed particulates. Although the film was removed from the SPMDs by solvent rinsing and analyzed separately, some lipid-mediated desorption of particle-associated PCBs and subsequent diffusion into the SPMD may have occurred prior to solvent-removal of the film. This observation suggests the potential for SPMD concentrations to reflect both vapor phase concentrations and to a lesser extent, lipid-extracted particulate-associated residues (see Section 3.9.2.). Unfortunately, concentrations of more chlorinated congeners in particulates collected on GFFs from the NIOSH method were often below quantitation limits, because only a small volume of air was sampled (1 m ) using this active method. 

Fig. 15. Exclusive action of porcine lipase on emulsified esters (146). Ordinates activity in perj cent of maximal activity on triolein emulsion. Abscissas lower axis, substrate amounts expressed in fractions of saturation for the solutions (on the left of the vertical dotted line) or in multiples of saturation for the emulsions (on the right of the line) upper axis, interfacial area expressed in 10 X cm in 100 ml. White circles, impure lipase containing some esterases. Black triangles, purified lipase. The substrate is triacetin on the left and methylbutyrate on the right. 

Figure 2. Variation of the rate of lipase hydrolysis of triacetin and methyl butyrate with the concentration of the substrate. The concentration is expressed as a fraction of the saturation concentration (S) and the hydrolysis rate as a percentage of the rate of triolein hydrolysis under optimal conditions. Key O, impure lipase plus esterolytic activity lipase purified by electrophoresis.

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