| Abstract | Organske tvari koje smanjuju površinsku napetost tekućina između dviju faza koje se međusobno ne miješaju se nazivaju tenzidi. Svaki tenzid je po svojoj strukturi amfifilni spoj što znači da se molekula sastoji od hidrofilnog i hidrofobnog dijela. Hidrofilni dio molekule tenzida koji se ujedno zove i glava sadrži polarne funkcionalne skupine koje mogu sadržavati različite naboje. S obzirom na naboj koji se nalazi na hidrofilnoj glavi tenzide možemo podijeliti u četiri kategorije: anionski, kationski, neionski i amfoterni. Hidrofobni dio svakog tenzida se sastoji od dugačkog alifatskog ugljikovodičnog lanca koji može biti ravni, razgranati ili aromatski. Hidrofilna glava anionskog tenzida otpušta negativno nabijene površinski aktivne ione prilikom disocijacije u vodenim otopinama. Analize tenzida se često izvode pomoću potenciometrijskih metoda koje se temelje na određivanju koncentracije tenzida mjerenjem elektrokemijskog potencijala sustava koji se sastoji od dviju vrsta elektroda, indikatorske i referentne.
Kao indikatorska elektroda tijekom eksperimenta korištena je tenzidno-selektivna elektroda koja sadrži tekuću membranu u koju je ugrađen senzorski materijal s višestjenčanim ugljikovim nanocjevčicama i tetrafenilboratom (MWCNT-TPB). Odziv MWCNT-TPB senzora na anionski tenzid natrijev dodecil sulfat (NaDDS) mjeren je metodom direktne potenciometrije u ultračistoj vodi i otopinama različitih smetajućih iona (interferenata) koncetracije 1·\(10^{-2} \) mol/\(dm^{3}\). Interferirajući ioni korišteni u eksperimentu su: klorid, jodid, fluorid, karbonat, hidrogenkarbonat, nitrat, nitrit, sulfat, sulfamat, benzoat, EDTA, ksilensulfonat, borat, hidrogenfosfat, fosfat, toluensulfonat, acetat, citrat i dodecilbenzensulfonat. Na temelju provedenih mjerenja izračunati su koeficijenti potenciometrijske selektivnosti MWCNT-TPB senzora za navedene anione. |
| Abstract (english) | Organic substances that reduce the surface tension of liquids between two phases that do not mix with each other are called surfactants. Each surfactant is an amphiphilic compound in its structure, which means that the molecule consists of a hydrophilic and a hydrophobic part. The hydrophilic part of the surfactant molecule, which is also called the head, contains polar functional groups that can contain different charges. Given the charge found on the hydrophilic head, surfactants can be divided into four categories: anionic, cationic, nonionic, and amphoteric. The hydrophobic part of each surfactant consists of a long aliphatic hydrocarbon chain which may be straight, branched or aromatic. The hydrophilic head of the anionic surfactant releases negatively charged surfactant ions during dissociation in aqueous solutions. Surfactant analyzes are often performed using potentiometric methods based on the determination of surfactant concentration by measuring the electrochemical potential of a system consisting of two types of electrodes, indicator and reference.
As an indicator electrode during the experiment, a surfactant-selective electrode was used containing a liquid membrane in which a sensor material with multiwall carbon nanotubes and tetraphenylborate (MWCNT-TPB) was embedded. The response of the MWCNT-TPB sensor to the anionic surfactant sodium dodecyl sulfate (NaDDS) was measured by direct potentiometry in ultrapure water and solutions of various interfering ions (interferences) with a concentration of 1·\(10^{-2} \) mol/\(dm^{3}\). Interfering ions used in the experiment are: chloride, iodide, fluoride, carbonate, bicarbonate, nitrate, nitrite, sulfate, sulfamate, benzoate, EDTA, xylene sulfonate, borate, hydrogen phosphate, phosphate, toluenesulfonate, acetate, citrate and dodecylbenzene sulfonate. Based on the performed measurements, the potentiometric selectivity coefficients of MWCNT-TPB sensor for these anions were calculated. |
