Sensitivity of the methylbenzenes and chlorobenzenes retention index to column temperature, stationary phase polarity, and number and chemical nature of substituents

• Published in: Journal of Chromatography A 2004-09, Vol.1048 (2), p.223-232
• Main Authors: Pérez-Parajón, Juan M., Santiuste, José M., Takács, Jószef M.
• Format: Article
• Language: English
• Subjects: Analysis; Analytical biochemistry: general aspects, technics, instrumentation; Analytical chemistry; Analytical, structural and metabolic biochemistry; Benzene Derivatives - analysis; Biological and medical sciences; Chemistry; Chlorine - chemistry; Chlorobenzenes; Chlorobenzenes - analysis; Chromatographic methods and physical methods associated with chromatography; Chromatography, Gas - methods; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Gas chromatographic methods; General pharmacology; HP-5 and ZB-WAX; Medical sciences; Methanol - chemistry; Methylbenzenes; Pharmacology. Drug treatments; Polyethylene Glycols - chemistry; Reproducibility of Results; Retention index increments; Retention index temperature effect; Sensitivity and Specificity; Siloxanes - chemistry; Stationary phase effect; Substituent effect; Temperature; Time
• ISSN: 0021-9673
• DOI: 10.1016/j.chroma.2004.07.028

Retention indices of methylbenzenes and chlorobenzenes on two fused silica capillary columns, HP-5 (diphenylsiloxane 5% diphenyldimethylsiloxane) and ZB-WAX (polyethylene glycol), have been calculated at various isothermal temperatures and compared with literature data. The retention index temperature effect was studied for each solute, finding greater retention index the higher the column temperature. A comparison between the straight line fit and the fit to the recently proposed equation I = A + B/ T + C ln T was carried out. The effect of the stationary phase polarity on the retention index was checked. In general, a greater retention index was found for the more polar stationary phase. The retention indices of the chlorobenzenes are greater than the retention indices of the methylbenzenes, irrespective of the stationary phase and the column temperature. In addition, the influence of the methyl/chlorine substitution on the benzene molecule was investigated at each temperature. The retention indices increased as the number of substituents (methyl/chlorine) increased. The retention index increments of methyl and chloro derivatives are also discussed, which permits to compare the effect of both, methyl or chlorine, chemical functions, for a fixed substituent number in the benzene molecule.