flow filtration sample that has not passed through the filter u201c small molecule u201d means a molecule having a molecular weight of less than 2000 daltons in some instances less than 1000 daltons and in still other instances less than 500 daltons or less such molecules include for example heterocyclic compounds carbocyclic compounds sterols amino acids lipids carotenoids and polyunsaturated fatty acids a molecule is u201c solvent available u201d when the molecule is isolated to the point at which it can be dissolved in a solvent or sufficiently dispersed in suspension in the solvent such that it can be detected in the solution or suspension for example a polysaccharide is u201c solvent available u201d when it is sufficiently isolated from other materials such as those with which it is naturally associated such that the polysaccharide can be dissolved or suspended in an aqueous buffer and detected in solution using a dimethylmethylene blue dmmb or phenol sulfuric acid assay in the case of a high molecular weight polysaccharide containing hundreds or thousands of monosaccharides part of the polysaccharide can be u201c solvent available u201d when it is on the outermost layer of a cell wall while other parts of the same polysaccharide molecule are not u201c solvent available u201d because they are buried.