摘要:

Quantification of total N-nitroso compounds (NOC) in urine and gastric juice is achieved by combining photolytic denitrosation with thermal energy analysis. The minimum mass detection limit of the technique is about 10 pmole No. Urine samples with NOC concentration as low as 200 nmolL−1can be analyzed with a precision of approximately 5-10%. The minimum concentration detection limit for gastric juice samples is about 1 μmolL−1. Except for nitrite, no interference is observed from nitrogenous compounds present in urine and gastric juice. The nitrite interference is effectively eliminated with sulphamic acid.

ISSN:1073-9149    

DOI:10.1080/10739149308543759

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

We describe our development of resonance ionization mass spectrometry (RIMS) using continuous-wave lasers toward the measurement of isotopic ratios important in geochemistry and geochronology. Specifically, we compare the precision and accuracy of230Th/232Th isotopic ratios measured by cw RIMS using both broad-band and narrow-band lasers. We also discuss the effectiveness of frequency-stabilizing techniques,i.e., external frequency locking of a broad-band dye laser and computer-controlled frequency centering of a narrow-band Ti:sapphire laser.

ISSN:1073-9149    

DOI:10.1080/10739149308543760

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The development of instrumentation permitting the generation of continuous linear- and various curve-shaped solvent-gradients in micellar electrokinetic capillary chromatography (MECC) is described. The coefficients of variation in retention time of test solutes are generally less than 2%. Gradients with unusual shapes are shown to facilitate rapid separations in MECC. Predictions of solute retention using a previously reported model are found to correlate-well with the experimentally obtained retention times of test solutes separated by MECC using solvent-gradients. Preliminary results indicate the possibility of using this analytical methodology, with a modified simplex procedure, for the optimization of solvent-gradient MECC separations.

ISSN:1073-9149    

DOI:10.1080/10739149308543761

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The relative concentration error of a simple “Beer's law” spectrophotometric instrument is easily and quantitatively modeled with the use of a simulation program and custom-programmed optical and electronic component blocks. The simulation data are in excellent agreement with published results.

ISSN:1073-9149    

DOI:10.1080/10739149308543762

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

An alternative method for the determination of mercury (Hg) in solid samples is presented in this article. Gaseous Hg is evolved when a solid sample is heated above 500°C in the presence of oxygen. The evolved Hg is collected on silver wool and is analyzed using cold vapor methods. We have found greater than 95% Hg recovery with various sediment and ash standards.

ISSN:1073-9149    

DOI:10.1080/10739149308543763

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:1073-9149    

DOI:10.1080/10739149308543764

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor