Analytical Sciences

A Simple and Rapid Method Based on Anti-aggregation of Silver Nanoparticles for Detection of Poly(diallyldimethylammonium chloride) in Tap Water

Wichaya TRISARANAKUL,*1 Apiwat CHOMPOOSOR,*2 Weerakanya MANEEPRAKORN,*3 Duangjai NACAPRICHA,*4 Nathawut CHOENGCHAN,*1 and Saowapak TEERASONG*1

*1 Department of Chemistry and Applied Analytical Chemistry Research Unit, Faculty of Science, King Mongkut’s Institute of Technology Ladkrabang, Bangkok 10520, Thailand
*2 Department of Chemistry, Faculty of Science, Ramkhamhaeng University, Bangkok 10240, Thailand
*3 National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), Pathumthani 12120, Thailand
*4 Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand

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⁻¹ with a detection limit of 0.7 mg L⁻¹. 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%.

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