Considerations on the determination of the limit of detection and the limit of quantification in one-dimensional and comprehensive two-dimensional gas chromatography

• Novel procedure for the estimation of standard deviation in chromatographic methods.
• Comparison of LOD and LOQ data estimated by standard deviation of the blank in 1D-GC and GC×GC.
• Dependence of LOD and LOQ values on a distribution pattern of modulated peaks in GC×GC.
• Simulation of chromatograms at the determination of LOD and LOQ in 1D-GC and GC×GC methods.

Methods based on the blank signal as proposed by IUPAC procedure and on the signal to noise ratio (S/N) as listed in the ISO-11843-1 norm for determination of the limit of detection (LOD) and quantitation (LOQ) in one-dimensional capillary gas chromatography (1D-GC) and comprehensive two-dimensional capillary gas chromatography (CG×GC) are described in detail and compared for both techniques. Flame ionization detection was applied and variables were the data acquisition frequency and, for CG×GC, also the modulation time. It has been stated that LOD and LOQ estimated according to IUPAC might be successfully used for 1D-GC–FID method. Moreover, LOD and LOQ decrease with decrease of data acquisition frequency (DAF). For GC×GC–FID, estimation of LOD by IUPAC gave poor reproducibility of results while for LOQ reproducibility was acceptable (within ±10% rel.). The LOD and LOQ determined by the S/N concept both for 1D-GC–FID and GC×GC–FID methods are ca. three times higher than those values estimated by the standard deviation of the blank. Since the distribution pattern of modulated peaks for any analyte separated by GC×GC is random and cannot be predicted, LOQ and LOD may vary within 30% for 3 s modulation time. Concerning sensitivity, 1D-GC–FID at 2 Hz and of GC×GC–FID at 50 Hz shows a ca. 5 times enhancement of sensitivity in the modulated signal output.