Determination of anionic surfactants using direct potentiomerty in municipal wastrwater

Uspoređena su tri potenciometrijska senzora (bazirana na tetraoktadecilamonijevom tetrafenilboratu, višestjenčanim ugljikovim nanocjevčicama (MWCNT) funkcionaliziranim sulfatnom skupinom i cetilpiridinijevim ionom te dimetildioktadecilamonijevom tetrafenilboratu (DDA-TPB) s dodatkom ugljikovih nanočestica kao senzorskim materijalom) kako bi se odabrao najpogodniji za određivanje anionskih tenzida u komunalnim otpadnim vodama. Izabran je potenciometrijski senzor koji se bazira na ionskom paru DDA-TPB kao elektroaktivnoj komponenti i o-nitrofeniloktileteru (o-NPOE) kao plastifikatoru, uz dodatak ugljikovih nanočestica. Određivanje anionskih tenzida u komunalnim otpadnim vodama provedeno je koristeći tri različite metode: potenciometrijska titracija, direktna potenciometrija i standardna spektrofotometrijska metilensko plavo (MBAS) metoda. Pri potenciometrijskim titracijama korištena je standardna otopina cetilpiridinijeva klorida (CPC), c = 4·\( 10^{-3} \) mol/L kao titrans, te metoda standardnog dodatka koja je dala zadovoljavajuće rezultate u otopinama uzoraka komunalnih otpadnih voda. Natrijev dodecilsulfat (NaDS), c = 4·\( 10^{-3} \) mol/L korišten je kao standardni dodatak. Tijekom određivanja odzivnih karakteristika senzor je pokazao sub-Nernstovski odziv (55,70 mV ± 0,10 po dekadi) u rasponu koncentracija od 2,0·\( 10^{-6} \) mol/L do 2,0·\( 10^{-3} \) mol/L za NaDS. Ciljana metoda korištenja DDA-TPB senzora za određivanje anionskih tenzida u uzorcima otpadnih voda bila je direktna potenciometrija, pri čemu su uzorci određivani u natrijevom sulfatu (\( {Na_{2}}SO_{4} \) ), c = 1·\( 10^{-2} \) mol/L. Uzorci su određeni i metodom direktne potenciometrije uz standardni dodatak, prilikom čega je kao standardni dodatak korišten NaDS na tri nivoa koncentracija. MBAS metoda je korištena za usporedbu rezultata s onima dobivenima potenciometrijskim titracijama i direktnom potenciometrijom sa i bez standardnog dodatka pri čemu je direktna potenciometija bez standardnog dodatka dala bolje rezultate.Three potentiometric sensors (based on tetraoctadecylammonium-tetraphenylborate, multi-walled carbon nanotubes (MWCNT) functionalized with sulfate group and cetylpyridinium ion and dimethyldioctadecylammonium-tetraphenylborate (DDA-TPB) with addition of carbon nanoparticles, as sensing material) were compared to select the most suitable one for the determination of anionic surfactants in municipal wastewater. Potentiometric sensor based on the DDA-TPB ion pair as an electroactive material and o-nitrophenyloctylether (o-NPOE) as the plasticizer with addition of carbon nanoparticles was selected. Determination of anionic surfactants in municipal wastewater was carried out using three different methods: potentiometric titration, direct potentiometry and standard spectrophotometric method Methylene Blue Active Substances (MBAS). Standard solution of cetylpyridinium chloride (CPC) at concentration of c = 4·\( 10^{-3} \) mol/L used as titrant and standard addition method, which obtained satisfying results in industrial wastewater samples, were used in potentiometric titrations. Sodium dodecylsulfate (NaDS) at concentration of c = 4·\( 10^{-3} \) mol/L was used as standard addition. The sensor exhibited a sub-Nernstian response (55,70 ± 0,10 mV/decade of activity) over the range of 2,0·\( 10^{-6} \) mol/L do 2,0·\( 10^{-3} \) mol/L for NaDS. The targeted method of using DDA-TPB sensor for determination of anionic surfactants in municipal wastewater samples was direct potentiometry with samples being determined in sodium sulfate (\( {Na_{2}}SO_{4} \) ), c = 1·\( 10^{-2} \) mol/L. Samples were also determined using direct potentiometric method with a standard addition, where NaDS was used as added standard at three concentration levels. The MBAS method was used as control for comparison of the results with those obtained using potentiometric titrations and direct potentiometry with and without added standard where direct potentiometry without the standard addition yielded better results