Sensitivity factors molecular weight

This means that drag diffusivity across membranes is sensitive to molecular weight, since molecular volume is determined by a number of factors, including the molecular weight of the molecule. Therefore, in general, large molecules will diffuse at a slower rate than small molecules. 

The solubility of hydrocarbon liquids from the same chemical family diminishes as the molecular weight increases. This effect is particularly sensitive thus in the paraffin series, the solubility expressed in mole fraction is divided by a factor of about five when the number of carbon atoms is increased by one. The result is that heavy paraffin solubilities are extremely small. The polynuclear aromatics have high solubilities in water which makes it difficult to eliminate them by steam stripping. 

Bacteria produce chromosomady and R-plasmid (resistance factor) mediated P-lactamases. The plasmid-mediated enzymes can cross interspecific and intergeneric boundaries. This transfer of resistance via plasmid transfer between strains and even species has enhanced the problems of P-lactam antibiotic resistance. Many species previously controded by P-lactam antibiotics are now resistant. The chromosomal P-lactamases are species specific, but can be broadly classified by substrate profile, sensitivity to inhibitors, analytical isoelectric focusing, immunological studies, and molecular weight deterrnination. Individual enzymes may inactivate primarily penicillins, cephalosporins, or both, and the substrate specificity predeterrnines the antibiotic resistance of the producing strain. Some P-lactamases are produced only in the presence of the P-lactam antibiotic (inducible) and others are produced continuously (constitutive). 

Chian et al. [69] point out that the Bellar and Iichtenberg [65] procedure of gas stripping followed by adsorption onto a suitable medium and subsequent thermal desorption onto a gas chromatograph-mass spectrometer is not very successful for trace determinations of volatile polar organic compounds such as the low molecular weight alcohols, ketones, and aldehydes. To achieve their required sensitivity of parts per billion, Chian et al. [69] carried out a simple distillation of several hundred ml of sample to produce a few ml of distillate. This achieved a concentration factor of between 10 and 100. The headspace gas injection-gas chromatographic method was then applied to the concentrate obtained by distillation. 

Note that all the desired properties depend directly or Indirectly on the ratio A/n and therefore, on the relative response factors and signal to noise ratios of the spectrophotometer and the differential refractometer. In general, spectrophotometers are more sensitive than differential refractometers, therefore, the ratio A/n at the tails of the chromatogram, that is, the refractometer signal will be zero while there still be a signal from the spectrophotometer. In addition, equations 9 and 10 are hyperbolic functions of the concentration. Thus, as the concentration decreases the apparent values of Mw and [n] will increase, increasing the uncertainty in the estimates of the molecular weights and the intrinsic viscosities (see Appendix I and references 26-29). In the limit when A/n - (or n/A 0), the polymer... 

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