High-Resolution Gas Chromatography and High-Resolution Gas ChromatographyMass Spectrometry Study of the Volatile Fraction Obtained from High-Inertinite Brazilian Coal by Supercritical Fluid Extraction Livia Mari Assis,  Fernando Mauro Lanc ¸ as Uni  ersity of Sao Paulo, Institute of Chemistry at Sao Carlos, P.O. Box 780, 13560-970, ˜ ˜ Sao Carlos, SP, Brazil ˜ Received 20 July 1998; accepted 12 February 1999 Abstract: This work presents the results of a study involving a high-inertinite coal Ž . from Amando Simoes Mine, located in Parana state Brazil . The organic matter ˜ ´ Ž . was extracted in a supercritical fluid static mode apparatus using toluene as the extraction fluid in the presence of hydrogen. The variables were studied using a 2 3 Ž factorial design two levels for three variables: temperature, reaction time, and . pressure with three center points. The liquid coal extracts obtained were fraction- Ž . ated by preparative liquid chromatography into eight fractions PLC-8 by using an adequate series of eluents. Each eluted fraction was collected and quantified by gravimetry. The relative fraction yields were used to calculate the influence of the variables and their interaction in the factorial design. All hydrocarbon-rich frac- Ž . tions were analyzed by high-resolution gas chromatography HRGC -fluid ioniza- Ž . tion detection and HRGC-mass selective detection MSD . The characterization of chemical classes of interest in the collected fractions was carried out using HRGC-MSD in the extracted ion mode. This approach allowed fine monitoring of compounds of interest by their characteristic mz values and was a fast and very selective setup for detection of specific compounds in a very complex matrix.  1999 John Wiley & Sons, Inc. J Micro Sep 11: 501  512, 1999 ( ) Key words: superficial fluid extraction SFE ; factorial design; capillary gas chroma- tography-mass spectrometry INTRODUCTION Ž . Supercritical fluid extraction SFE is an impor- tant alternative to conventional methods, such as Soxhlet extraction, for removing organic compounds from coal and other solid environmental matrices. Nevertheless, one of the main obstacles which pre- vents the fast acceptance of this new extraction technology is the difficulty of optimization condi- tions for SFE since small variations in the sample matrix composition often require substantial adjust-  ments in the extraction parameters 1 . *Permanent address: Federal Center of Technology Ed- ucation at Parana, Department of Chemistry and Biology, ´ Curitiba, PR, Brazil Correspondence to: F.M. Lanc ¸ as Contract grant sponsors: CAPES; CNPq Considering the complexity of the coal extrac- tion process, statistical approaches have been used for the simultaneous determination of various ana-  lytical SFE parameters in this work 2 . All variables and their contribution to the extraction were investi- gated by chemometrics process tools, such as facto- Ž . rial design analysis FDA . FDA is classified as a method for simultaneous evaluation of variables in a process. It also allows one to know if a variable promotes a positive or a negative effect in the overall yield of a process. FDA can also evaluate if the variables are independent or if they interact among themselves. Moreover, the factorial design can be used not only to find out optimal conditions but also to get the surface of  responses for the system studied 3 . Analysis of coal extracts by chromatographic techniques can be made directly without prior frac- Ž. Ž . J. Microcolumn Separations , 11 7 501 512 1999  1999 John Wiley & Sons, Inc. 501 CCC 1040-768599070501-12