EPA Method 25 Gas Chromatography for determining of NMTH

Detection Target

Determination of total non-methane hydrocarbons content

Introduction

Non-methane hydrocarbons (NMHC) are a core component of environmental air and industrial exhaust gas monitoring systems. Their detection aims to accurately quantify and continuously monitor the total amount of all gaseous hydrocarbon organic compounds except methane (CH₄). These compounds (such as olefins, aromatics, and alkanes) are not only key precursors of photochemical pollution—reacting with nitrogen oxides under sunlight to produce ozone (O₃) and fine particulate matter (PM_2.5)—but also indicators of characteristic pollutant emissions in many industries.

At the environmental management level, NMHC monitoring data directly impacts air quality assessment, pollution source analysis, and the development of regional atmospheric complex pollution control strategies. In the industrial sector, it is widely used in process emission control, exhaust gas treatment facility performance evaluation, and environmental compliance audits in industries such as petrochemicals, painting and printing, and semiconductor manufacturing. Currently, gas chromatography (such as the US EPA Method 25) and its combination with flame ionization detection are widely used internationally to achieve high-sensitivity detection from ppb to ppm levels. Gas chromatography for determining NMHC has also become an important technical foundation.

Overview

This solution conforms to the US EPA Method 25- DETERMINATION OF TOTAL GASEOUS NONMETHANE ORGANIC EMISSIONS AS CARBON. The organic content of the sample tank fraction is measured by injecting a portion of the sample into a gas chromatographic column to separate the NMO from carbon monoxide (CO), CO₂, and CH₄; the NMO are oxidized to CO₂, reduced to CH₄, and measured by an FID.

Apparatus

HKL-25 Gas Chromatograph for Non-Methane Total Hydrocarbons

Configuration