Calculation of the measurement uncertainty of BTEX VOC groups in stack gas sampling

To ensure low uncertainty in the measurements of BTEX parameters, which are one of the VOC groups in stack gas, BTEX parameters are analyzed by GC-MS after the pretreatment of activated carbon and solvent desorption in practice. In this study, the ISO GUM method was used for uncertainty budget. Estimated budget were calculated as Type A and B errors. Repeatablity, Intermediate Precision and Recovery studies were performed on Type A error results. In type B error, the measurement results from use of methanol and carbon disulfid, from the VOC Mix standard, from internal standard, from the micropipette, from the effect of temperature are taken in to account. At the end of study, the uncertainty components for benzene were determined as 24% intermediate precision, 23% calibration, 23% sampling, 11% repeatability, 8% mixed standard, 7% recovery and 4% others, respectively. The uncertainty components for toluene were determined as 23% sampling, 23% intermediate precision, 21% calibration, 10% repeatability, 8% mixed standard, 11% recovery and 4% others, respectively. The uncertainty components for ethyl benzene were determined as 25% sampling, 23% intermediate precision 23% calibration, 9% repeatability, 9% mixed standard, 7% recovery and 4% others, respectively. The uncertainty components for m-p xylene were determined as 25% sampling, 22% calibration, 23% intermediate precision, 9% mix standard, 9% repeatability, 8% recovery and 4% others, respectively. The uncertainty components for o-xylene were determined as 25% sampling, 24% calibration, 23% intermediate precision, 8% mix standard, 8% repeatability, 8% recovery and 4% others, respectively. As a result of studies conducted for the uncertainty components of the BTEX parameter, which are volatile organic compound (VOC) groups, the k=2 95% confidence range was calculated as ± 3.046 in the Benzene parameter, ± 2.955 in Toluene, ± 2.831 in Ethylbenzene and m, ± 2.823 in p-Xylene, ± 2.873 in o-Xylene for 10.00 ppm concentration.