摘要:

A new method for determinating diaminopimelic acid (DAPA) from rumen fluid was developed. The concentration of DAPA is used as an indicator for the estimation of protein content of bacterial origin. Due to the performic acid oxidation preceding hydrolysis of proteins, the neighbouring amino acids do not interfere in the determination of DAPA. As a result, even trace concentrations of DAPA may be accurately determined. Since, following the performic acid oxidation the sample does not contain methionine, the buffers developed for rapid determination of methionine may be used to advantage. As a result of this, DAPA may be determined by ion exchange coílumn chromatography in ca. 18 minutes. Following the development of the analytical method, it was applied to the determination of DAPA in the rumen fluid and the bacterial proteins prepared from the rumen fluid of cattle, goats and sheep. Based on the results, a method for evaluation of protein content of bacterial origin, based on the DAPA content, was derived.

ISSN:0003-2719    

DOI:10.1080/00032719508000024

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Simple approaches aimed at enhancing both the sensitivity (by improving the mass transfer both from the liquid to the gas phase and through the membrane) and the precision of pervaporation processes are proposed. A conventional method based on formation of ethylene blue was used for the determination of sulfide after pervaporation. The use of a 280-cm waste tubing instead of the usual 20–30 cm length dramatically improved the sensitivity [slope of the calibration curve from 0.015 to 0.154 AU/(μg/mL of sulfide) for the sample injection mode, with detection limits from 0.68 to 0.07 μg/mL; and from 0.018 to 0.088 AU/(μg/mL) for the continuous sample introduction mode, with detection limits from 0.42 to 0.07 μg/mL], and the precision (r.s.d. % from 5.46 to 2.86 for the sample injection mode, and from 7.03 to 1.61 for the continuous sample introduction mode). Halting the flow during 5 min enhanced both the sensitivity [slope 0.123 vs 0.015 AU/(μg/mL)], and the precision (r.s.d. % 1.61 vs 7.03) but was detrimental to the sampling frequency.

ISSN:0003-2719    

DOI:10.1080/00032719508000025

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The weighted least squares method using 1/x2as a weighting factor is described and compared with conventional ordinary and weighted least squares and robust regression. Applications of these different methods to the relevant data sets demonstrates that the performance of the procedure discussed in this paper exceeds that of ordinary least squares method and equals, and often exceeds, that of weighted or robust methods.

ISSN:0003-2719    

DOI:10.1080/00032719508000026

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper deals with the optimal conditions for the detection of15N determined using a four-factor experimental design from [213C-1.315N] caffeine measured with an atomic emission detector (AED) coupled to gas chromatography (GC). Owing to the capability of a photodiodes array, AED can simultaneously detect several elements using their specific emission lines within a wavelength range of 50 nm. So, the emissions of15N and14N are simultaneously detected at 420.17 nm and 421.46 nm respectively.

ISSN:0003-2719    

DOI:10.1080/00032719508000027

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0003-2719    

DOI:10.1080/00032719508000028

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0003-2719    

DOI:10.1080/00032719508000029

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0003-2719    

DOI:10.1080/00032719508000013

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor