Quantitative analysis of hydrocarbons in gasolines by capillary gas—liquid chromatography

Univariate analytical calibration methods and procedures. A review

An original focus on univariate calibration as an experimental process of quantitative analysis is presented. A novel classification system is introduced against the background of the present situation concerning nomenclature of calibration methods. Namely, it has been revealed that four methods well-known in analytical chemistry: the conventional method, the internal standard method, the indirect method and the dilution method, can be split into those carried out in both the interpolative and the extrapolative mode. It is then shown that the basic procedures of all these methods can be modified including different approaches, such as matrix-matched technique, spiking the sample with a reactant, bracketing calibration, and others. For the first time (as compared to monographies dealing with univariate calibration) it is reviewed how the methods are mixed and integrated with one another thereby creating new calibration strategies of extended capabilities in terms of enhanced resistance to the interference and non-linear effects - as the main sources of systematic calibration errors. As additional novelty, rationally possible combinations of the calibration methods - not met hitherto in the literature - have been predicted. Finally, some general rules relating to calibration are formulated and the main calibration problems that still need to be solved are displayed.

Volatile organic compounds in the blood of persons in Kuwait during the oil fires

Between March and November of 1991, approximately 9000 workers from 43 different countries battled the burning oil wells in Kuwait. To document the exposure of persons in Kuwait during the oil well fires to volatile organic compounds (VOCs), we obtained samples of blood from 14 U.S. personnel in Kuwait City in May of 1991 (group I) and 40 American firefighters working in the oil fields in October of 1991 (group II). Concentrations of VOCs in group I and group II were compared with those of a random sample of 114 persons in the United States (reference group). The median concentrations of VOCs in group I were equal to or lower than those in the reference group. We found significant differences between the median concentrations of several VOCs in group II and the reference group. Median levels of ethylbenzene were about 10 times higher among group II than among the reference group (0.53 microgram/l vs 0.052 microgram/l). Median levels of benzene, m-/p-xylene, o-xylene, styrene, and toluene among group II were more than double those of the reference group. Although firefighters had higher median concentrations of VOCs than the reference group, those American personnel in Kuwait not involved in fighting the oil fires had concentrations of VOCs comparable to those in the reference group. Blood VOC measurements indicate a significant increase in exposure to VOCs in firefighters, but do not demonstrate this in personnel in Kuwait City.

Computerized capillary gas chromatographic analysis of hydrocarbon mixtures in workplace air

The quantitative composition of white spirit vapours in workplace air may differ considerably from the solvent being used, although all components are the same. By calculating the hygienic effect from the threshold limit value (NGV) of each component, a more reliable estimate is obtained of the occupational hazard than by using the NGV for white spirit. In this method the analyses were performed by on-column injection onto a temperature-programmed capillary column. Retention indices based on n-paraffins and isooctane were calculated using spline functions. Index tables were established for different hydrocarbon mixtures. The validity of the retention indices was found to be satisfactory, depending on the stability of the column and the possibility of optimizing the indices when replacing one column by another of the same type and dimensions. Comparisons were made with alternative methods for determining the concentration of white spirit vapours in air samples. A polar column was used to check the total content of aromatics.