摘要:

A method for the simultaneous determination of Mn, Co, Zn and Ni which combines Ion-chromatography and a post column reaction with xylenol orange is described. Using 0.07 M oxalic acid (pH adjusted to 5.5 with lithium hydroxide) as eluent, Mn, Co, Zn and Ni were first separated on a 4x250mm IonpacCS-5 column having both sulphonic acid and Alkyl quaternary ammonia functional groups and then transferred to a post-column reaction coil, where the elements react with xylenol orange. The coloured complexes formed were spectrophotometrically measured at 570 nm. The procedure has been successfully applied for the determination of Co, Zn and Ni in Al-bronze.

ISSN:0003-2719    

DOI:10.1080/00032719908542996

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

High-speed capillary electrochromatography was developed on both short and long packed columns with 2 μm non-porous ODS as the stationary phase. Factors that affect the analysis time of samples, such as voltage, electrolyte concentration, pH and organic modifier concentration in the mobile phase, were studied systematically. Fast analysis of aromatic compounds within 13 seconds was realized with column efficiency of 573,000 plates/m and a R.S.D.% of the retention times of all components in 8 consecutive injections below 1.0%, which demonstrated the high efficiency and high reproducibility of such a technique. In addition, DNPH derived aldehydes and ketones in both standards and environmental samples were separated with high speed.

ISSN:0003-2719    

DOI:10.1080/00032719908542997

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Nonlinear standard addition method was studied for determination of DMS in beer with a laboratory-assembled headspace gas chromatographic system with flame photometric detector. The sample concentration and the detector response exponent can be obtained simultaneously without preparation of the blank sample, and the reliability of the results can be evaluated by the self-integrity of the data. The method introduced here is easier to carry out and more cost-effective.

ISSN:0003-2719    

DOI:10.1080/00032719908542998

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Waxy (essentially amylose-free) maize starch was chemically modified to varying degrees by treatment with succinic anhydride, and the degree of substitution was determined by a standard wet chemistry method. FT-Raman spectra of the modified starches were obtained, and indicated a characteristic ∼1730 cm−1C=O stretch Raman band whose intensity was dependent on the degree of succinylation. The ratio of intensity of the ∼1730 cm−1band to a ∼940 cm−1C-C stretch Raman band (used as an internal standard) was plotted against the degree of succinylation determined by titration, and a linear fit was obtained with a correlation of 0.998. Hence FT-Raman spectroscopy represents a rapid non-destructive method to determine the degree of succinylation of modified waxy maize starch, and should be suitable for use with succinylated starches of any amylose content.

ISSN:0003-2719    

DOI:10.1080/00032719908542999

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor