摘要:

The trace analysis of biological fluids or tissues for toxicologically active compounds has traditionally been frustrated by a combination of very complex, dirty samples and relatively non-selective detection methods. The use of capillary GC columns together with highly selective detectors, such as the mass spectrometer (MS), has provided us with very sensitive and specific methods of trace organic analysis. Gas chromatography-microwave induced plasma (GC-MIP) emission spectroscopy has long been used for the trace analysis of both nonmetals and metal derivatives. Unfortunately, GC-MIP methods have rarely been applied to the trace analysis of compounds derived from biological matrices, despite the obvious fact that it should provide significant opportunities and advantages when compared with almost all other conventional, inexpensive GC detectors (FID, ECD, PID, AFID, etc.). We have now developed and applied GC-MIP based trace analytical methods, in combination with n-butyl boronate ester derivatization, for catechol, 3-methylcatechol, and 4-methylcatechol, two of which are present in a number of human urine extracts. We describe the final GC-MIP conditions for the analysis of standards and real samples, as well as a comparison of the qualitative and quantitative results vs trimethylsilylation and GC-FID analyses of these same samples.

ISSN:0003-2719    

DOI:10.1080/00032718208064428

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

When a solution containing a single reactant is subjected to kinetic analysis with a reagent giving rise to a pseudo-first-order reaction, non-linear regression analysis of the concentrationtime data yields a random scatter of the residuals around the best fit to the pseudo-first-order equation. If the same equation is used when a second reactant is also present, systematic errors arise and yield a deviation plot having a characteristic shape. If the amplitude of that plot is substantially larger than the random error of measurement, the presence of the reactant can be detected, and its concentration can then be evaluated by non-linear regression onto the equation that takes its presence into account. The amplitude passes through a maximum as the relative concentration of the second reactant increases, or as the ratio of the rate constants increases. For any given ratio of concentrations, detection of the second reactant is impossible unless the ratio of the rate constants lies within a certain range, which will be governed by the data-acquisition schedule employed. For the particular schedule assumed here, examination of these dependences shows, for example, that it should be possible to detect the second reactant if its concentration is 2.5 per cent of that of the first reactant and if the ratio of the rate constants is between 7.1 and 21.7.

ISSN:0003-2719    

DOI:10.1080/00032718208064429

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The synergic extraction of Ca, Sr, and Ba ions from aqueous solutions into cyclohexane or benzene containing 1- pheny 1 - 3 - methyl - 4 - stearoylpyrazol - 5 - one (HPMSP) and TOPO has been studied. Quantitative extraction (log D>2) was attained at pH>5.4 for Ca, pH>6.5 for Sr, and pH>7.3 for Ba when cyclohexane containing 0.05 M HPMSP and 0.01 M TOPO was used, and the corresoponding values for benzene were 6.5, 7.8, and 8.4. Extracted species were M(PMSP)2(TOPO)3(M=Ca, Sr, Ba) for cyclohexane and Ca(PMSP)2(TOPO)3and Sr (or Ba) (PMSP)2(TOPO)2for benzene.

ISSN:0003-2719    

DOI:10.1080/00032718208064430

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Volatile organic compounds in polystyrene food containers and polystyrene cups were determined using direct headspace sampling with gas chromatographic and gas chromatographic/mass spectrometric analysis. Compounds which were detected in polystyrene food containers and cups included 2-methy 1-2-propen-1-ol, ethylbenzene, styrene, β-methylstyrene, and trimethy 1- and tetramethylbenzenes. Individual concentrations of these impurities in the polymeric materials were estimated as 5 to 270 μg/g. Several impurities including styrene were extracted into water at 88 to 93°C within 2 to 3 minutes upon contact. VAriations in aqueous concentrations of styrene as a function of time in contact with polystyrene cups are reported here. Maximum concentrations of styrene in hot water were 35 μg/L after 15 to 20 minutes of contact of water with cups.

ISSN:0003-2719    

DOI:10.1080/00032718208064431

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The hydrolysis of nicotinamide in alkaline solutions was studied. An ammonia gas-sensing electrode was used to follow the formation of ammonia. A technique making use of simulated reactions has been developed to calibrate the electrode under dynamic conditions overcoming problems arising because of the relatively slow response of the sensor. A general expression has been derived for the pseudo first-order rate constant valid over the concentration range 0.005 to 0.10 M nicotinamide, 0.1 to 0.5 M hydroxide and the temperature range 22° to 31° C, under constant ionic strength (0.5 M NaOH + NaC1O4).

ISSN:0003-2719    

DOI:10.1080/00032718208064432

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The analysis of nitrite-nitrate mixtures by indirect titration with ascorbic acid performed before and after passage through a reducing Cd column is proposed and discussed with particular reference to experimental conditions, calculation scheme and concentration ranges.

ISSN:0003-2719    

DOI:10.1080/00032718208064433

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

ISSN:0003-2719    

DOI:10.1080/00032718208064427

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor