Accuracy considerations of portable electrochemeical NOX analyzers

摘要

Two key components contributing to measurement errors of electrochemical analyzers are discussed. These are the sample conditiong system and the elelctrochemeical nitric oxide and nitrogen dioxide sensors. The problems associated with various types of conditioning systems are discussed and some experimental results are presented using analyte spiking methods. Permeation drier based systems are shown to cause the smallest loss of the analyte. Two major problems of the NO and NO2 sensors are examined. The first problem deals with the significant effect of temperature on the sensor and its associated interference rejection filter. The requirement for maintaining sensor and filter temperature below 30 deg. C is demonstrated. The second deals with the saturation and drift considerations caused by over exposure to the gas. The significance of capillar size to minimize drifit for difusion sensors is discussed. Experimental results are presented and discussed with a view to the recently published EPA CTM-022 Method.