Bisphenol A (BPA) is a chemical that is used to manufacture many daily products which include food container and hygiene products (Petre, 2016). BPA can present in dental application, water bottles, the inside lining of canned products, medical devices and many other daily products. There is a high possibility for human to take in BPA such as through their diet, air, water and dust (Micha?owicz, 2014). Moreover, BPA is best known for its application in producing polycarbonate plastics and epoxy resins which include those in beverage cans and baby bottles. The occasion of using epoxy resins is to avoid corrosion and stay inert (Rogers, n.d).
Bisphenol A or 4, 4′-Isopropylidenediphenol is commonly known as BPA is a white powder with mild odour. BPA with molecular formula of C15H16O2 contain two phenol functional groups. Besides, it has become a difunctional building block of various important plastics and plastics additives (“Bisphenol A,” 2005). BPA is known as one of the the largest quantities chemical in the world (Rasheed, 2014).
BPA is first synthesized from phenol and acetone through condensation process. This process requires a strong acid to act as catalyst such as hydrochloric acid (Neagu, 1998). The figure 2.2 showed the synthesis process of BPA (Negau, 1998). The physical and chemical properties of bisphenol A is listed in table 2.1 (Rasheed, 2014).
There are numerous ways that human can expose to BPA, particularly from food and beverage containers made with BPA. BPA is widely used to coat the surface of cans whereas polycarbonate is used in food containers (Rasheed, 2014). Migration of BPA from metallic cans to human is mainly affected by the storage time and temperature (MUNGUIA-LOPEZ, 2002). Moreover, trace amount of BPA may move from the wall of the cans to the food due to heating process for shipping (Takao et al., 2002). The other possible route of exposure to BPA is through inhalation due to there is detectable amount of BPA in indoor air correlated with dust (Taylor, Welshons ; Saal, 2008). According to the researcher, BPA is present in human’s urine, tissues, breast milk and even follicular fluid (Vandenberg, n.d).
BPA is an endocrine disruptor. BPA can act as antagonist to interfere the reaction of the natural ligand. Children and babies face the greatest danger of the endocrine disruptor due to low resistance in their body. Moreover, BPA can inhibit some enzyme activity which subsequently affects human health (Preethi, 2014). BPA can prohibit the reaction of thyroid hormone which may affect human embryogenesis and neonatal development. This happened when the thyroid hormone binds to BPA and function as an antagonist (Rubin, 2011). Furthermore, BPA is trusted of causing hormone-related problems such as early puberty in girls and also birth defects in human (Chouhan, 2012). A study revealed that BPA level in the urine of normal people is significantly higher than the control group of people towards direct contact with BPA products. Researcher suspected that disruptive role of BPA will contribute to early puberty and premature breast development (Leonardi et al., 2017).
Bisphenol A does not naturally occur in environment. Environmental BPA can be categorized as preconsumer and postconsumer items. Preconsumer source contain materials that used to manufacture BPA-containing products. On the other hand, postconsumer source is corresponds to discharge from municipal wastewater, break down of plastics and leaching from the landfills (Flint et al., 2012). Rivers, lakes and ocean are the major deposition place for BPA. This brings adverse negative impacts to aquatic organisms. From a research study, the researcher claimed that the main route of exposure for the fish is not through their diet, but inhalation through the gills (Kang, Asai, & Katayama, 2007). Hence, it is not astounding that BPA will continuously affect the fish by estrogenic effects. There are also evidence in showing BPA has remarkable effect on antagonistics activity towards endocrine disruptor (Mitsui, Tooi, & Kawahara, 2007).
Matters over BPA’s harmful effects to human health brings the government of Canada become the first throughout the world to classify BPA as harmful and ban it in manufacturing baby’s bottles (“Regulation,” n.d). Besides, European Union legally prohibited sales of BPA-containing baby’s bottles. In 2003, France has banned BPA in children products. France has started to ban BPA on food packaging in 2015. It is stated that the U.S. Food and Drug Administration (FDA) prohibits the use of BPA in manufacturing children and baby’s items in 2012. In addition, infant formula packaging materials is banned from using BPA in 2013 (“Regulations,” 2017). China and Malaysia have joined to the team to ban BPA to protect their citizens (Bardelline, 2011).
There are many methods can be used to extract BPA from environmental water sample.
Liquid-liquid extraction (LLE) is most commonly used extraction method to extract analyte from water sample. LLE use the principal of different solubility in two different solvents usually water and organic solvent to separate analytes from interested sample (Peake, 2016). The sample is commonly dissolves in ethyl acetate, chloroform or dichloromethane. This may due to adequate sensitivity of result provided from this method. However, LLE can cause a change in actual concentration of the analyte in the sample (Liao & Kannan, 2012).
Solid phase extraction (SPE) is commonly used to replace liquid-liquid extraction (LLE). This is due to SPE has numerous advantages including low consumption of organic solvents, easy to operate and high recovery (Zhao et al., 2009). The principle of SPE is to increase the concentration of targeted analytes in aqueous phase which having very low concentration. Solid phase is used to absorb the target analytes then a small volume of solvent such as methanol and acetone is used to desorb the analytes (Cunningham, 2014).
Solid phase microextraction (SPME) can extract the target analyte onto a solid support (Razaee, Yamini & Faraji, 2009). This method is simple, rapid and portable. This is follow by introduction of different geometries of SPME such as fiber, stir bar, membrane, magnetic nanoparticles and thin film microextraction (Piri-Moghadam, Ahmadi & Pawliszyn, 2016). Stir bar sorptive extracation (SBSE) is one of the green microextration. SBSE is used due to its simplicity, selectivity and sensitive especially in detecting BPA. In addition, SBSE is mainly coupled with high performance liquid chromatography (HPLC) (Lin et al., 2010). On the other hand, a fiber-packed needle extraction is developed and it has higher efficiency than classical sample preparation methods such as LLE and SPE (Ogawa et al., 2009).
Liquid-phase microextraction (LPME) is an organic-free extraction and it is known as alternative green microextraction. LPME is mainly used to extract analytes from volatile and semivolatile ionisable sample. Moreover, LPME is very efficient method and affordable technique (Zhang, Su & Lee, 2005). There are mainly three categories of LPME such as single-drop liquid-phase microextraction (SD-LPME), hollow fibre liquid-phase microextraction (HF-LPME) and dispersive liquid-liquid microextraction (DLLME). SD-LPME is an unstable method and sample may be lost because this extraction method is based on a hanging drop (Liu & Dasgupta, 1996). Next, HF-LPME is introduced by Pedersen-Bjergaard and Rasmussen by using the principle of using polypropylene hollow fibers as membrane (Pedersen-Bjergaard & Rasmussen, 1999).Dispersive liquid-liquid extraction (DLLE) is a microextraction technique introduced to compensate for the high usage of organic solvent in classical extraction technique (Hong et al., 2017). DDLE has several advantages include environmental-friendly sample preparation, fast, inexpensive, easy to operate and high recoveries (Rezaee, Ya mini & Faraji, 2010). After that, dispersive liquid-liquid phase microextraction based on solidification of floating organic (DDLME-SFO) is developed to replace DLLE by using less toxic solvents which can solidify at low temperature for easy sample extract (Hong et al., 2017). In addition, DDLME-SFO is a time dependent method due to its non-exhaustive properties.
Trace amount of bisphenol A (BPA) can be determine by high sensitivity, selectivity instrument.
Reversed-phase C18 column is commonly used to detect trace amount of BPA. Reversed phase is when a non-polar stationary phase is used simultaneously with a polar mobile phase (Driskell, 2003).
Emission and excitation wavelength are important factors to increase the sensitivity of instrument. BPA shows optimal excitation in 230nm. In addition, 305nm is the highest peak for emission wavelength (Xiong et al., 2017). The fluorescence spectra are show in figure 2.3 (Ballesteros-Gómez, Rubio & Pérez-Bendito, 2009).
HPLC-MS need injection of large amount of sample. Hence, this will subsequently affect the cartridges and decrease the sensitivity of mass spectroscopy (Li & Franke, 2015). Mass spectrometry is always used due to it can provide fast and accurate result in a short of time. Furthermore, MS can detect even the sample is at low concentration (Battal et al., 2014). Therefore, it is frequently as a coupled method to determine BPA in sample.
GC needs derivatization step compared to LC, but this make it more selective and sensitive (Jurek & Leitner, 2017). Derivatization makes the target analytes more selective and sensitive by improving its volatility and thermal stability (Jeannot et al., 2002). Separation and detection for BPA uses GC in order to be improved.