Particulate matter (PM) emitted from engines is currently measured by the filter weight method. The filter weight method passes diluted emission gases through a filter collecting the PM, and post test weighs the mass of the collected PM on a precision balance. However, this method is time consuming, and with decreasing PM emission volumes, improvements in accuracy were needed. So the MEXA-1370PM was developed, to measure soluble organic fraction (SOF), soot, sulfate and total PM by vaporizing, thermally decomposing and gasifying (through redox reaction) the PM collected on a filter. The MEXA-1370PM allows easy measurement of collected PM mass, and shows good correlation with the PM weighing results of the precision balance. On the other hand, regarding the separation performance of SOF and soot, dispersion of the detection ratio increased for PM volume of 0.5 mg and under. To prevent the main cause, the mixing of O2 during SOF measurement, the device composition and criteria were improved; SOF and soot were accurately separated up to 0.2 mg.
Recently, after-treatment techniques for diesel engine emission reduction have made remarkable progress. Owing to new techniques such as the diesel particulate filter (DPF), the total amount of particulate matter (PM) collected on filter is rapidly reducing. Conventionally, PM amounts from engine exhaust gas were measured by the weighing method using precision balances (1) . However, measurement of low PM samples was difficult, troublesome and time consuming. In addition, the component separation measurement of SOF and soot that requires Soxhlet extraction, making the process even more cumbersome. As an alternative, in 2001, HORIBA released the MEXA-1370PM analyzer, which utilized the vaporization/ thermal decomposition/ oxidation-reduction method (hereinafter, 'vaporization method')(1) - (3). The MEXA-1370PM can quickly and easily measure separated components of PM.