Sains Malaysiana 39(2)(2010): 175–179

Colourimetric Determination of Features of an Air Sampling Technique Optimal for Detection of Surfactants

 (Penentuan Keadaan Optimum Teknik Pensampelan Udara bagi Pengesanan Surfaktan Secara Kolorimetri)

NUR HAZIMAH ABDUL HALIM¹, NORFAZRIN MOHD HANIF¹,

MOHAMED ROZALI OTHMAN¹ & MOHD TALIB LATIF*^{, 2}

¹School of Chemical Sciences & Food Technology

Faculty of Science & Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia

²School of Environmental and Natural Resource Sciences

Faculty of Science & Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia

Received: 28 April 2009 / Accepted: 3 August 2009

ABSTRACT

Surfactants in the atmosphere may act as cloud condensation nuclei, with a potentially negative impact on the global climate. Therefore, accurate determination of surfactants is crucial in order to investigate the possible effects of surfactants on the atmosphere. The aim of this study was to identify the optimum sampling method for measuring the maximum quantity of surfactants present in ambient air. Air samples were collected using a range of air sampling pumps that were made to vary in terms of flow rate, storage period, type of absorbing solution and the characteristics of the impinger tube. Samples obtained were analysed by colourimetry for anionic and cationic surfactants as methylene blue-active substances (MBAS) and disulphine blue-active substances (DBAS), respectively. Absorbance was measured at 650 nm for MBAS and 628 nm for DBAS using UV-visible spectrophotometer. We found that the optimum sampling method consisted of an absorbent solution (deionised water, buffer solution and methylene blue/disulphine blue solution) with the flow rate of 1.0 L/min. The concentration of surfactants in all sampling methods remained constant regardless of the storage period (1 day and 4 days), indicating that surfactants in the absorbing solution are quite stable. Covering the impinger tube was shown to influence the amount of both anionic and cationic surfactants detected.

Keywords: Ambient air; anionic and cationic surfactants; colourimetry

                                                               ABSTRAK       

Surfaktan di atmosfera berpotensi untuk bertindak sebagai nukleus kondensasi awan yang berupaya memberi kesan negatif terhadap iklim global. Kaedah yang tepat bagi penentuan surfaktan adalah penting bagi mengkaji pelbagai kesan surfaktan terhadap atmosfera. Kajian ini bertujuan mengkaji dan membangunkan satu kaedah pensampelan optimum yang berpotensi dalam menyerap kandungan maksimum surfaktan yang hadir di udara. Pensampelan udara dijalankan dengan menggunakan pam udara yang berbeza daripada segi kadar aliran, tempoh penyimpanan, jenis larutan penyerap dan keadaan tiub penyerap. Sampel yang diperoleh kemudiaanya dianalisis secara kaedah kolorimetri sebagai sebatian aktif metilena biru (MBAS) bagi surfaktan anionik dan sebagai sebatian aktif disulfina biru (DBAS) bagi surfaktan kationik. Serapan analit seterusnya diukur dengan menggunakan spektrometer ultra lembayung boleh nampak pada panjang gelombang 650 nm bagi MBAS dan 628 nm bagi DBAS. Hasil kajian menunjukkan bahawa keadaan yang optimum bagi pensampelan surfaktan adalah dengan menggunakan campuran larutan penyerap (air nyahion, larutan penimbal dan larutan metilena biru/disulfina biru) pada kadar alir 1.0 L/min. Kepekatan surfaktan didapati malar bagi tempoh penyimpanan 1 hari dan 4 hari, menunjukkan sukfaktan di dalam larutan penyerap adalah agak stabil. Penutupan tiub penyerap didapati mampu mempengaruhi kepekatan kedua-dua surfaktan yang ditentukan.

Kata kunci: Kaedah kolorimetri; surfaktan anionik dan kationik; udara persekitaran

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*Corresponding author; email: talib@ukm.my