ORIGINAL PAPER Quality control of gasohol using a micro-unit for membraneless gas diffusion Sasithorn Muncharoen & Jirayu Sitanurak & Warawut Tiyapongpattana & Nathawut Choengchan & Nuanlaor Ratanawimarnwong & Shoji Motomizu & Prapin Wilairat & Duangjai Nacapricha Received: 28 January 2008 / Accepted: 21 April 2008 / Published online: 17 May 2008 # Springer-Verlag 2008 Abstract This work describes the development of a new spectrophotometric flow technique suitable for monitor- ing of ethanol content in gasohol fuel. Membraneless gas-diffusion (MBL-GD) was applied with one-step aqueous extraction of gasohol (1:2 gasohol/water). Seg- ments of aqueous extract and color developing reagent were allowed to flow into two separate channels in the MBL-GD device. Inside the device, ethanol vapor can diffuse across a small headspace between the two channels (donor and acceptor). Introduction of an air- segment behind the zone of acceptor reagent to stop dispersion of the colored zone greatly improves the rapidity of analysis using this MBL-GD technique. Two methods were developed for quality control of gasohol by measuring ethanol content. Method I is suitable for direct calibration of E5 and E10. Method II is recommended for E20. These methods have high accuracy with good precision (% RSD: 1 to 4.9, n =45) and have a sample throughput of 26 samples per hour. E10 samples were compared with analysis using a standard GC method. Keywords Membraneless gas diffusion . Flow-based . Ethanol . Gasohol Introduction Gasohol is a mixture of gasoline and ethanol with purity from 99.0 to 99.5% (v/v). Ethanol is added to gasoline to supplement use of the fossil fuel. This type of alcohol- blended fuel has long been used in some countries such as in, Brazil, USA and Sweden. Gasohol was initiated in Thailand as one of the King’ s projects in the substitution energy program. Seventeen years later, after the beginning of the project, gasohol became available commercially at petrol stations throughout Thailand from 2002. Ethanol is blended with gasoline at different percentages designated by an E-number which gives the percentage in Microchim Acta (2009) 164:203–210 DOI 10.1007/s00604-008-0058-6 S. Muncharoen : J. Sitanurak : W. Tiyapongpattana : N. Choengchan : N. Ratanawimarnwong : P. Wilairat : D. Nacapricha (*) Flow Innovation-Research for Science and Technology Laboratories (FIRST Labs), Bangkok, Thailand e-mail: dnacapricha@gmail.com S. Muncharoen : J. Sitanurak : W. Tiyapongpattana : P. Wilairat : D. Nacapricha Department of Chemistry, Faculty of Science, Mahidol University, Rama 6 Road, Bangkok 10400, Thailand N. Choengchan Department of Chemistry, Faculty of Science, King Mongkut’ s Institute of Technology Ladkrabang, Chalong Krung Road, Bangkok 10520, Thailand N. Ratanawimarnwong Department of Chemistry, Faculty of Science, Srinakharinwirot University, Sukhumvit 23, Bangkok 10110, Thailand S. Motomizu Department of Chemistry, Faculty of Science, Okayama University, 3-1-1 Tsushimanaka, Okayama 700-8530, Japan