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Author: search.filters.author.Chompoosor, ApiwatSubject: search.filters.subject.Tap water

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    Gold nanorods enhanced resonance Rayleigh scattering for detection of Hg2+ by in-situ mixing with single-stranded DNA
    (2018-02-01)
    Ngernpimai, Sawinee
    ;
    Matulakun, Piyaporn
    ;
    Teerasong, Saowapak
    ;
    Puangmali, Theerapong
    ;
    Kopwitthaya, Atcha
    A resonance Rayleigh scattering (RRS) method for determination of Hg<sup>2+</sup> concentration using positively charged gold nanorods (GNRs) and thymine-rich single-stranded DNA (ssDNA) was developed. Hg<sup>2+</sup> can induce a conformation change of ssDNA from a random coil to a hairpin structure via thymine–Hg<sup>2+</sup>–thymine coordination. Hairpin shaped DNA possesses a high density of negative charges, therefore it caused in a drastic aggregation of GNRs. This resulted in an enhancement of RRS intensity. In this work, a change in RRS intensity proportional to the concentration of Hg<sup>2+</sup> was monitored by spectrofluorometer at excitation and RRS wavelengths of 550 nm (λ<inf>ex</inf> = λ<inf>RRS</inf>). This method offered a detection limit of 0.23 nM, which is lower than the maximum mercury contaminant level specified by the US Environmental Protection Agency. Good precision of analysis was obtained (3.1% relative standard deviation). Furthermore, the method was simple, involving in-situ mixing and sensing in a one-pot solution. Detection was accomplished in 5 min. This makes the method advantageous in terms of convenience and rapidity of analysis. The developed method was successfully applied for detection of Hg<sup>2+</sup> in tap water samples. Recoveries were found in range of 100.6–119.0%.
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    A simple and rapid method based on anti-aggregation of silver nanoparticles for detection of poly(diallyldimethylammonium chloride) in tap water
    (2016-01-01)
    Trisaranakul, Wichaya
    ;
    Chompoosor, Apiwat
    ;
    Maneeprakorn, Weerakanya
    ;
    Nacapricha, Duangjai
    ;
    Choengchan, Nathawut
    A simple and rapid method was developed for the detection of poly(diallyldimethylammonium chloride) (PDADMAC) using citrate-capped silver nanoparticles (AgNPs). Detection was based on anti-aggregation of AgNPs in phosphate buffer caused by PDADMAC. Due to its positive charges, PDADMAC was adsorbed onto AgNPs via electrostatic interaction with citrate, which resulted in the charges at the particle surfaces to become positive and caused repulsion among particles. Furthermore, long-chain PDADMAC provided steric hindrance. These two effects promoted the dispersion of AgNPs in the phosphate buffer. A change in the state of dispersion influenced the surface plasmon resonance (SPR) of AgNPs. Therefore, in this work, the concentration of PDADMAC was determined by monitoring changes in absorbance (at 396 nm) caused by SPR of AgNPs. Under optimal conditions, the calibration was linear over the range of 1 to 100 mg L<sup>-1</sup> with a detection limit of 0.7 mg L<sup>-1</sup>. Satisfactory precision was obtained (RSD = 2.8%). This method was successfully applied to the determination of PDADMAC in tap water samples. The recoveries ranged from 86.0 - 107.5%.