ISSN:0935-6304    

DOI:10.1002/jhrc.1240010502

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240010503

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240010504

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractTwo new acyltetramic acids related to streptolydigin have been isolated from fermentations of Streptomyces lydicus. The principal members of this complex were resolved by TLC on silica gel. However, the methods of detection, permanganate spray or bioautography, were not suitable for both crude fermentation broths and purified extracts. Gas chromatography is unsuitable for the detection of either underivatized or silylated streptolydigins. High performance liquid chromatography (HPLC) particularly on triethylaminoethyl cellulose is rapid and sensitive and is the method of choice for the analysis of both crude and purified samples. Using high performance liquid chromatography, two components were detected in the complex, which are not observed using any of the other chromatographic procedures.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240010505

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractEquations describing gradient elution in TLC, with a mobile phase of a constant composition in each step, have been derived. These equations are useful for calculating retention volumes from isocratic TLC data. Equations originally derived for gradient HPLC were adapted for TLC. The validity of the equations has been experimentally verified. The satisfactory agreement between experiment and theory for binary mobile phase composed of methyl ethyl ketone and n‐heptane suggests that TLC can be used as a pilot technique for gradient HPL

ISSN:0935-6304    

DOI:10.1002/jhrc.1240010506

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe error propagation is given for routine analysis by in situ evaluation in TLC using the methods with internal or external standard. The internal standard method will need four different measurements of peak height or area, while the external standard method uses only two measurements. Therefore in the latter case the error of the spotting volume will cause errors in the determined concentration. By error propagation it can be shown, that the internal standard method gives better results, if the error in measuring peak height or area is less than the error of the spotting volume.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240010507

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractA thorough survey of the past and current available literature shows that the diffusion of the solvents toluene, ethylbenzene, ortho‐, meta‐, and para‐xylenes in polypropylene has not been studied so far, although such studies find practical applications in various industrial problems. Diffusitives and the activation energies of the above mentioned solvents in polypropylene were determined in the temperature range of 45–120°C by gas chromatography. The values obtained in this communication compare fairly with those determined by conventional techniques for analogous systems, confirming the reliability of the gas chromatography as a powerful tool for diffusion measurement and the authenticity of the data presente

ISSN:0935-6304    

DOI:10.1002/jhrc.1240010508

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractA definition for an absolute retention index is given. This index is independent of whether the process is isothermal or temperature programmed. The relation between this index and Kovats's index is discussed. General equations are derived for the retention times of homologous series, from which the position of the air peak or missing members can be determined. Methods used in the literature for air peak determination are improved and extended to other cases of interest. The retention index in temperature programmed chromatography is reexamined in the light of recent publications on temperature programming.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240010509

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractDuring one year continuous use of on‐column injection, the typical advantages described in our first report have fully been confirmed. In addition the analysis of large sample volumes has proved promising. Only minor modifications have been applied to the on‐column injector device. Broad evidence has been gathered showing that full separation efficiency of the capillary columns after on‐column injection is attained only when cold trapping or the solvent effect, as band shortening mechanisms, are working‐ While, under the conditions of on‐column injection, cold trapping is less efficient than with other injection techniques, the opposite holds true for the solvent effect. Compared with splitless injection, the danger of excessive solvent condensation on the column is increased. A working rule is presented for establishing the optimal chromatographic conditions for handling large sample volumes while ensuring full separation efficiency yet avoiding harm to t

ISSN:0935-6304    

DOI:10.1002/jhrc.1240010510

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractA method is described for the simultaneous quantitative determination of monoamines and related compounds from urine and brain tissue samples in the pg‐range, using a GC/MF instrument LKB‐2091 provided with a multiple ion detection (MID) system and capillary columns. The simultaneous detection of “fingerprints” with fourteen and more compounds during one single GC run was achieved after the intoduction of “time gates” for the detection of the different characteristic masses. Several modifications to the LKB equipment permitted exact reproducibility of retention times, which is essential for the use of “time gates”. The detection of “fingerprints” with these acidic, basic and alcoholic substances was achieved by the extraction of the dried biological samples wit

ISSN:0935-6304    

DOI:10.1002/jhrc.1240010511

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY