Estimation of limit of detection (lod), limit of quantification (loq) and machine standardization by gas chromatography

Abstract

Abstract : An experiment was conducted in the pesticide and environmental toxicology laboratory of Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU) in 2014 to establish Limit of detection (LOD) and limit of quantification (LOQ) along with machine standardization for method validation in chemical analysis by gas chromatography. This work compares three methods based on the International Conference of Harmonization (1CH) and EURACHEM guidelines, namely, signal-to-noisc, blank determination, and linear regression, to estimate the LOD and LOQ for volatile organic compounds (VOCs) by experimental methodology using gas chromatography. Five VOCs, i.e. toluene, ethylbenzene, iso-propylbenzene,7i-propylbenzene and vinylbenzene, were chosen for the experimental study. The results indicated that the estimated LODs and LOQs were not equivalent and varied by a factor of five to six for both LOD and LOQ for different tested methods. After conditioning of the GC machine, the baseline of chromatogram was set ‘O’ position by generating straight line horizontally. The peak of DDT was produced at 12.34 minute. The retention time was same for all standard concentration. Moreover, the percent deviation of peak area was not varied more than 5%, Thus it could be remarked that the machine was standardized. It is therefore essential to have a clearly described procedure for estimating the LOD and LOQ during method validation to allow inter-laboratory comparisons.