Comparison of coal tars by l.c.-m.s.

The application of l.c.-m.s., using both quadrupole and magnetic sector mass spectrometers, to the analysis of aromatic fractions of hydropyrolysis tars and a Gray-King tar, is described. The results are compared with those obtained by g.c.-m.s. and probe mass spectrometric methods such as field desorption, desorption chemical ionization and low ionizing voltage probe. The molecular weight range observed by l.c.-m.s. is much greater than that observed by g.c.-m.s. and is similar to those observed by probe methods. The proportion of the aromatic fractions eluted from the NH₂-bonded silica column by hexane is not known, but some polar molecules are retained and can be eluted by increasing solvent polarity. The results indicate the presence of extensive homologous series of aliphatics and aromatics with carbon numbers exceeding C₅₀. The extent of alkylation decreases with increasing severity of the method used to prepare the tar.     

N.m.r. of solid biopolymers

The dynamical behaviour of four solid polypeptides (α-chymotrypsin, insulin, lysozyme, ribonuclease A) has been investigated by proton magnetic relaxation. The interpretation was supplemented by measurements on the constituent amino acids, and on dipeptides, tripeptides and homopolypeptides. The following motions were identified and characterized: methyl group reorientation, segmental motion, sidechain motion, proline ring puckering, reorientation of water molecules in the structure. Slow motions were investigated through measurements of the dipolar relaxation time T_ID.     

中国洗涤用品工业协会赴美国考察报告

应美国洗涤剂协会(SDA)的邀请,经中国轻工业联合会批准,中国洗涤用品工业协会组团,于2002年5月13日至27日对美国进行行业考察.     

Second interim report of the A.O.A.C.-A.O.C.S. Crude Fiber Liaison Committee

Conclusions The results obtained in this collaborative study show that none of the methods tested offer sufficient advantages in precision and accuracy to warrant selection as an official method to the exclusion of other methods studied. Also the precision of all methods tested show these methods to be inadequate for checking crude fiber specification limits set up by the N.S.P.A. on soybean oil meal. This statement would also apply to any other product where specification limits on crude fiber are narrower than the precision shown in Table VI. Ease and speed for manipulation are also an important criterion for choosing an official method. A poll of committee members showed no definite preference for any one method studied; every method received the support of two or more of the committee members. The Liaison Committee is still hopeful that a method can be devised that will give a precision in line with trade specifications and practices. The committee will continue to work toward the development of such a method.     

M.A.L.D.I.-T.O.F. mass spectrometry characterization of 4-alkyl substituted phenol-formaldehyde novalac type resins

Two methods of synthesis for 4-alkyl substituted phenol-formaldehyde resins are described. A common method for synthesis of novolac type phenol-formaldehyde resin uses sulfuric acid catalyst in the presence of xylene for azeotropic removal of water of reaction. By the use of M.A.L.D.I.-T.O.F. mass spectrometry we have demonstrated that m-xylene is incorporated into these polymers. Polymers free of impurities are best prepared using a cation exchange resin as catalyst in the presence of a less reactive solvent, e.g. chlorobenzene, or in the absence of solvents. © 1997 Elsevier Science Ltd.