Assignment 2 : Writing an introduction

The Comparative Determination of Gamma-Aminobutyric Acid (GABA) between Ultraviolet and Fluorescence Detection by High-Performance Liquid Chromatography (HPLC)

                                              Kritchapol  Panrod

Stage 1 : Gamma-aminobutyric acid (GABA) is a non-protein amino acid. GABA is a one of the neurotransmission agents which can inhibit over stimulating of the brain and reduce hypertension from the stress (Zhang et al., 2006). Moreover, GABA generally finds in human such as the cortex, hippocampus, hypothalamus, central nervous system (CNS), plants and animals. 

Thus, an analysis of GABA in the quantitation usually use the high-performance liquid chromatography (HPLC) to measure the amount of GABA in unknown sample. HPLC is the technique that can detect an agent in solution by it’s detector (such as ultraviolet light or fluorescence light) which analysts the agent when it passes through the HPLC column and interprets the results in terms of graphs and area under the peak. However, a detection of GABA has a problem when using HPLC because it has a small molecule and does not has fluorescent or ultraviolet absorbance (Shah et al., 2002). Therefore, one of the technique to resolve that problem is the pre-column derivatisation. The pre-column derivatisation will use an agent providing strong ultraviolet (UV) or fluorescent absorbance mixing with the sample before used in HPLC  (Shah et al., 1999) 

             Stage 2 : In UV detection, GABA is analysed by derivatizing agents including phenylisothiocyanate (PITC) (Jarry et al., 1992), 2-hydroxynapthaldehyde (HN) (Khuhawar and Rajper, 2003; Bor et al., 2009; Jannoey et al., 2010 and Hayat et al., 2014), 4-dimethyl-aminoazobenzene-4-sulfonyl chloride (DABSYL-Cl) (Varanyanond et al., 2005), naproxen acyl chloride (NAC) (Hsieh et al., 2006) and 1-fluoro-2,4-dinitrobenzene (FDNB) (Ishikawa et al., 2009). 

            In fluorescence detection, GABA is commonly analysed by a derivatizing agent which is o-phthaladehyde (OPA). OPA reacts with primary amines in the presence of thiol and generates derivatives which are fluorescent (Devall et al., 2007, Zhang et al., 2005, Fekkes et al., 1995 and Sheng et al., 2005). Unfortunately, the deravatives of OPA are not stable especially in the acid solution so they have developed to improve the stability and more sensitivity of derivatives by added naphthalene-2,3-dicarboxaldehyde (NDA) (Clarke et al., 2007), 2-mercaptoethanol (Iwaki and Kitada, 2007) and 3-mercaptopropionic acid (MPA) (Freitas Silva et al., 2009) 

   

            Stage 3 : Many of papers have a single analysis GABA but none of them has not comparative two techniques in one paper.

            Stage 4 & 5 : Thus, this paper will compare between UV detection and fluorescence detection. The sample of UV derivatizing agent is HN, an inexpensive agent and the fluorescence derivatizing agent is OPA because it normally uses in a detection. Therefore, this paper will point out that each of the technique can present the result in quantitation of GABA, retention time, limit of detection and limit of quantitation.