Validation of three new methods for determination of metal emissions using a modified Environmental Protection Agency Method 301.

Three new methods applicable to the determination of hazardous metal concentrations in stationary source emissions were developed and evaluated for use in U.S. Environmental Protection Agency (EPA) compliance applications.

An NMR investigation of the importance of intramolecular hydrogen bonding in determining the conformational equilibrium of ethylene glycol in solution.

Although conformational analysis by NMR of ethylene glycol indicates generally strong preferences for the gauche conformation in solvents ranging from water to chloroform, the bulk of the NMR evidence indicates that intramolecular hydrogen bonding between the hydroxyl groups is unlikely to be a significant factor in determining that preference, except possibly in fairly non-polar solvents. The 'gauche effect' is clearly very important, especially in aqueous solution.

An NMR and quantum mechanical investigation of solvent effects on conformational equilibria of butanedinitrile.

Vicinal proton-proton NMR couplings and ab initio quantum mechanics have been used to investigate solvent effects on conformational equilibria of butanedinitrile. The trans and gauche conformations are about equally favored at room temperature in solvents of low dielectric constant while the equilibrium is essentially the statistical proportions of one-third trans and two-thirds gauche in water with a high dielectric constant. The coupling assignments were confirmed with the aid of stereospecific deuterium-labeled (R,R or S,S)-1,2-dideuteriobutanedinitrile.

An NMR and quantum-mechanical investigation of tetrahydrofuran solvent effects on the conformational equilibria of 1,4-butanedioic acid and its salts.

Vicinal proton-proton NMR couplings have been used to compare the influences of water and tetrahydrofuran (THF) as solvents on the conformational equilibria of 1,4-butanedioic (succinic) acid and its mono- and dianionic salts. An earlier NMR investigation (Lit, E. S.

An NMR investigation of the conformational equilibria of 2-(2'-pyridyl)ethylphosphonic acid in several solvents.

Vicinal proton-proton NMR couplings have been used to investigate whether the position of conformational equilibria is determined by intramolecular N-H hydrogen bonding for 2-(2'-pyridyl)ethylphosphonic acid 1 in its various possible ionization states in water, methanol, ethanol, and dimethyl sulfoxide (DMSO). With 1 in the form of its monoanion and dianion, the trans is favored, with the dianion being more trans than the monoanion for a given solvent, probably as the result of steric effects, possibly enhanced by repulsive electrostatic effects between the negatively charged phosphonic group and the lone pair on the pyridine nitrogen. For 1 and its conjugate acid, the gauche amounts, respectively, to 43% and 45% in water, 66% and 51% in methanol, 66% and 64% in ethanol, and 29% and 49% in DMSO.