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Browsing Chemistry by Subject "Acetaminophen."

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    Metallophthalocyanine-based electrochemical sensors for accurate qualitative and quantitative analysis of emerging pollutants in water resources.
    (2024) Shoba, Siyabonga Blessing.; Booysen, Irvin Noel.; Mambanda, Allen.
    Water is a precious resource and safeguarding it from pollution is paramount to ensure the well-being of both the environment and human health. Emerging contaminants such as pharmaceuticals and heavy metals pose significant threats, necessitating vigilant monitoring and appropriate action. Traditional laboratory-based analytical techniques like Gas Chromatography, ICP-OES and HPLC have been instrumental in quantifying pollutants. However, their high operational costs, maintenance requirements and the need for specialized personnel limit their widespread use, especially in resource-constrained countries. Electrochemical sensors have emerged as a promising solution. They provide real-time, portable and cost-effective options for on-site detection of pollutants in water. Current advancements in electrochemical sensors are centred around achieving selective detection using chemical modifiers, all while maintaining electrocatalytic sensitivity and reproducibility. These sensors can be tailored to target specific contaminants, making them highly efficient tools for monitoring water quality and ensuring the sustainability of this invaluable resource. In the first experimental chapter, a glassy carbon electrode (GCE) was modified by an asymmetric metallophthalocyanine (MPc) complex, A3B-CoPc-flav (where A = flavonyloxy substituent and B = an alkynyloxy substituent/molecular mast). The modification of an electrode was achieved via electrochemical grafting followed by clicked chemistry between the diazonium-functionalized GCE and the a-CoPc-flav3 to afford the GCE|clicked-a-CoPc-flav3. The chemically modified electrodes (CME) were utilized as electrocatalytic detectors for dopamine (DA) under optimized conditions. The response of the GCE|clicked-a-CoPc-flav3 was linear in the concentration range of 2 μM to 14 μM, attaining limits of detection and quantification of 0.311 and 0.942 μM, respectively, and high reproducibility (%RSD of 2.25%, N = 3). Interference studies were conducted, revealing a marginal shift in the DA peak potential in the presence of interfering substances. Despite this shift, the peak current intensity of DA remained largely unaffected, affirming the selectivity and accuracy of the CME. The analytical capabilities of the CME were further assessed using real water samples. The obtained percentage recoveries of (97.1%) of DA by the GCE|clicked-a-CoPc-flav3 and the well-established HPLC-MS method (113%) are both within the acceptable range of 80-120%. In the second experimental chapter, a platinum electrode (Pt) was modified via the electropolymerization of polypyrrole (PPy) after its co-electrodeposition of tetra-[4-((1H benzotriazole)methoxy)phthalocyaninato]cobalt(II) (CoPc-Bzt). The electrodeposition of CoPc-Bzt was performed in 1:1 DMF/acetonitrile containing 1 M tetrabutylammonium hexafluorophosphate (NBu4PF6) electrolyte over 20 cycles using cyclic voltammetry to afford a Pt|PPy/CoPc-Bzt (Bzt = benzotriazole). The resultant CME was prone to fouling by the analyte of interest, mercury(II). Due to fouling the differential pulse anodic stripping voltammetry (DPASV) was used to detect Hg(II) using the Pt|PPy/CoPc-Bzt within 10 μM to 100 μM linear range. The LOD and LOQ were found to be 3.11 and 10.00 μM, respectively. Interference studies illustrated that the detection capabilities of the CME were not affected by the presence of other heavy metal cations. The analytical performances of Pt|PPy/CoPc-Bzt (97.4%) and Inductively coupled plasma – optical emission spectroscopy (ICP-OES) (112.3%) are both within the acceptable range of 80-120%. In the third experimental chapter, the Pb electrocatalytic sensing capability of a gold electrode modified via the adsorption of electrospun nanofibers (ENFs) and Nafion (Nf) as an annealed conductive top-layer was evaluated. The fabricated ENFs comprised of a core polymeric nanocomposite of tetra-4-(3-oxyflavonephthalocyaninato)cobalt(II) (CoPc-flav), the carboxylic acid functionalized multiwalled carbon nanotubes (f-MWCNTs) and polyaniline (PANI) encapsulated in a polyvinyl acetate (PVA) ENFs. The resultant CME, Au|ENFs-1-Nf was not prone to fouling as was found when using the bare and the other constructed CMEs whose signal stabilities were compromised by background electrolyte currents. The Au|ENFs-1-Nf electrode could detect the Pb(II) cations in a reproducible manner (%RSD of 3.92%, N = 3) ranging from 8 to 125 μM, and limits of detection and quantification of 0.51 and 1.55 μM were obtained, respectively. However, the interference studies illustrated that the detection capabilities of the CME are severely compromised by the presence of other heavy metal cations. The analytical performance of the CME rendered a comparable percentage recovery (103%) with that of the ICP-OES (115%). In the fourth experimental chapter, the nanofabrication and characterization of new conductive materials, PANI-CoPc-fur (1) ((PANI = polyaniline and CoPc-fur = tetra-4-(2-furanmethylthiophthalocyaninato)Co(II)) and PANI-CoPc-fur-f-MWCNTs (2) are reported. Subsequently, an electrospun nanofiber (ENF) composite was fabricated where the core comprised of 2 that was encapsulated with a PVA shell. The resultant nanoconjugate, ENFs-2 was adsorbed on a glassy carbon electrode (GCE) followed by the immobilization of a permeable adhesion top layer of Nafion (Nf) to render the chemically modified electrode, GCE|ENFs-2-Nf. The classical physical properties of the electron-mediating layer for the CME synergistically aided in promoting its electrocatalytic activities. Consequently, the CME showed greater anodic and cathodic cyclic voltammetry (CV) peak currents compared to the bare GCE and other modified electrodes, indicating its higher sensitivity to acetaminophen (APAP), an emerging water pollutant of concern. Limits of detection and quantification (LOD and LOQ) values for APAP attained by squarewave voltammetry (SWV) were lower compared to those acquired using other electrochemical techniques. The detection of APAP at the GCE|ENFs-2-Nf attained by squarewave voltammetry (SWV) was linear from 10 to 200 μM of APAP and was reproducible (%RSD of 3.2%, N = 3). The respective calculated LOD and LOQ values of 0.094 and 0.28 μM were lower compared to those acquired using other electrochemical techniques. Analysis of APAP in the presence of commonly associated interferences metronidazole (MTZ) and dopamine (DA) illustrated a significant separation between the SWV peak potentials of APAP and MTZ, whereas there was some degree of overlap between the SWV current responses of APAP and DA. The analytical performance of the GCE|ENFs-2-Nf rendered a comparable percentage recovery (103.8%) with that of liquid chromatography–mass spectrometry (LC–MS) (106%). Iqoqa. Amanzi awumthombo oyigugu futhi ukuwavikela ekungcoleni kubaluleke kakhulu ukuze kuqinisekiswe inhlalakahle yakho kokubili imvelo nempilo yabantu. Ukungcola okuvelayo okufana nemithi kanye nezinsimbi ezisindayo kubangela izinkinga ezinkulu, okudinga kuqashelwe kakhulu kanye nesinyathelo esifanele. Izindlela ezijwayelekile zokuhlaziya ezenziwa ezindaweni zokuhlaziya, ezifana nokuhlaziya igesi, i-ICP-OES ne-HPLC zibe nesandla ekulinganiseni izinto ezingcolisayo. Nokho, izindleko zokusebenza eziphezulu, izidingo zokunakekela kanye nesidingo sabasebenzi abakhethekile kunciphisa ukusetshenziswa kwazo ngokusabalele, ikakhulukazi emazweni anezinsizakusebenza ezigqozayo. Ukusebenzisa imishini ekwazi ukuhlonza ingozi kwaletha isixazululo esithembisayo. Imishini lena yaletha isixazululo sangempela, esiphathekayo futhi akubizi kakhulu ukutholwa kokungcola emanzini. Ukuthuthuka kwemishini yesimanje ekwazi ukuhlonza ingozi isebenzisa amakhemikhali ukukwazi ukuhlonza ingozi, ngenkathi kudingeka ukuthi kwayona inakekelwe ukuze ihlale iphilile. Le mishini ingenziwa ngendlela efanele ukuze ikwazi ukubhekana ngqo nokungcola okuthile, okungenza ibe amathuluzi asebenza kahle kakhulu ukuqapha izinga lamanzi nokuqinisekisa ukusimama kwalo mthombo wempilo obaluleke kangaka. Esigabeni sokuqala sokuhlola, iglassy carbon electrode (GCE) yashintshwa nge-asymmetric metallophthalocyanine (MPc), A3B-CoPc-flav (lapho A = iflavonyloxy substituent kanye no-B = i-alkynyloxy substituent/mast molecular). Ukuguqulwa kwe-electrode kwenziwa esifundweni sogesi kubhekwa ukuhleleka kwezakhi phakathi kwediazonium-functionalized GCE kanye ne-a-CoPc-flav3 ukuze kusetshenziswe i-GCE|clicked-a-CoPc-flav3. Ama-electrode ashintshwe amakhemikhali (CME) asetshenziswa njengezihlonzi zogesi zedopamine (DA) ngaphansi kwezimo ezithuthukisiwe. Impendulo ye-GCE|clicked-a-CoPc-flav3 yayiqondile ebangeni lika-2 μM kuya ku-14 μM, ifinyelela imikhawulo yokuhlonza kanye nomthamo we-0.311 kanye no-0.942 µM, ngokulandelanayo, kanye nokuphindaphindeka okuphezulu (%RSD ka-2.25%), N = 3). Izifundo ngemishini ekwazi ukuhlonza inkinga, zaveza ukuguquguquka okuncane kwamandla aphezulu e-DA ebukhoneni bezinto eziphazamisayo. Naphezu kwalolu shintsho, ukuqina kwamanje okuphezulu kwe-DA kusalokhu kungathinteki, okuqinisekisa ukukhetha kanye nokunemba kwe-CME. Amakhono okuhlaziya e-CME abuye ahlolwa kusetshenziswa amasampula angempela amanzi. Amaphesenti atholakele (97.1%) e-DA nge-GCE|clicked-a-CoPc-flav3 kanye nendlela esungulwe kahle ye-HPLC-MS (113%) kokubili kungaphakathi kwebanga elamukelekayo lika-80-120%. Esigabeni sesibili sokuhlola, i-electrode yeplathinamu (Pt) yashintshwa ngemishini yepolypyrrole (PPy) ngemva kokuhlanganiswa kwayo kwetetra--[4-(1H-benzotriazole)(imethoxy)iphthalocyaninato]icobalt(II) (CoPc- Bzt). Imishini ye-CoPc-Bzt yenziwe ngo-1:1 DMF/acetonitrile equkethe oku-1 M kwetetrabutylammonium hexafluorophosphate (NBu4PF6) yemishini engaphezu kwemijikelezo engama-20 kusetshenziswa indlela ebhaka amakhemikhali, ivoltammetry ayizindilingana ukuze kutholakale i-Pt|PPy/CoPc-Bzt (Bzle = benzotriazo). Umphumela we-CME wawuncike kokuhlolwayo, imekhyuli (II). Ngenxa yokonakala yokunyakaza okwehlukile kwe-anodic stripping voltammetry (DPASV) yasetshenziswa ukuze kutholwe i-Hg(II) kusetshenziswa i-Pt|PPy/CoPc-Bzt ngaphakathi kobubanzi bomugqa obuyi-10 µM ukuya e-100 µM. I-LOD ne-LOQ kutholwe kuku-3.11 kanye ne-10.00 µM, ngokulandelanayo. Ucwaningo lokungenelela lubonise ukuthi amandla okwenziwa e-CME awazange athintwe ukuba khona kwamanye amamolekhyuli ensimbi esindayo. Ukuhlaziya ukusebenza kwe-Pt|PPy/CoPc-Bzt (97.4%) kanye neplasma ehlanganiswe emachotsheni – nge-optical emission spectroscopy (ICP-OES) (112.3%) kokubili kungaphakathi kwebanga elamukelekayo lama-80-120 amaphesenti. Esigabeni sesithathu sokuhlola, ikhono le-Pb yemishini ekwazi ukuhlonza ingozi ye-electrode yegolide elungiswe ngokufaka i-electrospun nanofibers (ENFs) kanye neNafion (Nf) njengesendlalelo esiphezulu esisebenzayo iye yahlolwa. Ama-ENF akhiwe ahlanganisa ipolymeric nanocomposite eyinhloko yetetra-4-(3-oxyflavonephthalocyaninato)icobalt(II) (CoPc-flav), isimuncwane sekhabhoni esisebenza ngemultiwalled carbon nanotubes (f-MWCNTs) kanye nepolyaniline (PANI) efakwe kwipolyvinyl i-acetate (PVA) ENFs. Umphumela we-CME, Au|ENFs-1-Nf awuzange uthembakale njengoba kwatholakala lapho kusetshenziswa ama-CME angenalutho namanye akhiwe ukuqina kokuhlonza kuye kwaphazanyiswa amaza imishini engemuva. Imishini ehlonza inkinga ye-Au|ENFs-1-Nf i-Pb(II) ngendlela ekwazi ukukhiqizwa kabusha (%RSD ka-3.92%, N = 3) kusukela kokuyi-8 kuye e-125 µM, kanye nemikhawulo yokutholwa nokulinganisa okuyi-0.51 noku-1.55 µM zatholwa, ngokulandelana. Kodwa-ke, izifundo zokungenelela zibonise ukuthi amandla okuzakhela e-CME asengozini enkulu ngokuba khona kwamanye amamolekhyuli ensimbi esindayo. Ukusebenza kokuhlaziya kwe-CME kuveze amaphesenti aqhathaniswayo (103%) nalokhu kwe-ICP-OES (115%). Esigabeni sesine sokuhlola, inanofabrication kanye nokuhlukaniswa kwezinto ezintsha zokuqhuba, i-PANI-CoPc-fur (1) ((PANI = polyaniline ne-CoPc-fur = tetra-4-(2-furanmethylthiophthalocyaninato)Co(II)) kanye ne-PANI- I-CoPc-fur-f-MWCNTs (2) ibikwa ngokulandelayo, inhlanganisela ye-electrospun nanofiber (ENF) yakhiwe lapho ingqikithi ehlanganisa i-2 ehlanganiswe negobolondo le-PVA, i-ENFs-2 yakhangiswa ngengilazi icarbon electrode (GCE) okulandelwa ukuvalwa kongqimba oluphezulu olunamathelayo lwe-Nafion (Nf) ukuze kunikezwe i-electrode eguquliwe ngamakhemikhali, i-GCE|ENFs-2-Nf amandla ekukhuthazeni imisebenzi yayo yemishini. Ngenxa yalokho, i-CME ibonise ukuphakama okukhulu kwe-anodic necathodic cyclic voltammetry (CV) uma kuqhathaniswa ne-GCE engenalutho namanye ama-electrode ashintshiwe, okubonisa ukuzwela kwayo okuphezulu kwe-acetaminophen (APAP), ukungcola kwamanzi okuvela ukukhathazeka. Imikhawulo yokutholwa nokulinganisa (i-LOD ne-LOQ) amanani e-APAP atholwe ngesquarewave voltammetry (SWV) ibiphansi uma iqhathaniswa naleyo etholwe kusetshenziswa amanye amasu imishini yamakhemikhali. Ukutholwa kwe-APAP ku-GCE|ENFs-2-Nf etholwe ngesquarewave voltammetry (SWV) bekuwumugqa osuka e-10 ukuya ema-200 µM ye-APAP futhi ibikwazi ukukhiqizwa kabusha (%RSD yoku-3.2%, N = 3). Amanani alandelanayo abaliwe e-LOD nawe-LOQ ayi-0.094 kanye nayi-0.28 µM abephansi uma kuqhathaniswa nalawo atholwe kusetshenziswa ezinye izindlela zemishini yamakhemikhali. Ukuhlaziywa kwe-APAP phambi kokuphazamiseka okuvame ukuhlotshaniswa nemetronidazole (MTZ) kanye nedopamine (DA) kubonise ukwehlukana okukhulu phakathi kwamandla aphezulu e-SWV e-APAP kanye ne-MTZ, kuyilapho kube khona izinga elithile lokushayisana phakathi kwezimpendulo zamanje ze-SWV ze-APAP ne-DA. Ukusebenza kokuhlaziya kwe-GCE|ENFs-2-Nf kuveze amaphesenti aqhathaniswayo (103.8%) nalokho kweliquid chromatography–mass spectrometry (LC–MS) (106%).