Self-reporting molecularly imprinted polymer with the covalently immobilized ferrocene redox probe for selective electrochemical sensing of p-synephrine

Article simultaneously imprinting the p-synephrine 1 template and covalently immobilizing a a ferrocene redox probe in a (bis-bithiophene)-based polymer. The resulting molecularly imprinted polymer (MIP) was deposited on the Pt electrode as a thin film to form a redox self-reporting MIP film-based chemosensor

Application of the Impedance Spectroscopy as a New Tool for Studying Biodiesel Fuel Aging Processes

Fatty acid methyl esters (FAME), which are presently the main component of biodiesel fuels, undergo relatively fast oxidation processes. This behavior prevents long term storage of this fuel. From laboratory practices, it transpires that even after a very short period of storage, the oxidative stability of the biodiesel exceeds the values required by European regulations. Therefore, the goal of this work was to devise a parameter (marker) allowing for fast and convenient identification of the chemical stability of biodiesel. Moreover, we were aiming to devise a marker which can also be used for the evaluation of the chemical stability of other hydrocarbon fuels containing biocomponents. To this end, in the presented study, selected biodiesel samples were subjected to controlled aging processes in laboratory conditions at 95 °C and oxygen flow according to the norm. Then, physico-chemical parameters were selected that are critical from the point of view of the fuel practical application. Those included density, refractive index, oxidative stability and resistance to oxidation. The appropriate physico-chemical properties were measured before and after an aging process conducted for various times. Simultaneously, electrochemical impedance spectroscopy (EIS) studies were performed for all the studied samples yielding the electrical parameters of the sample, including resistance, relaxation time and capacitance. Subsequently, a correlation between the results of the EIS studies and the selected critical parameters has been established. The obtained results indicate that the resistance, relaxation time and capacitance of the studied biodiesel fuel increase with aging time. This indicates the formation of long chain compounds with increased polarity. Interestingly, the electrical parameter changes are faster at the early stages of the aging process. This suggests a change of the oxidation mechanism during prolonged aging. The devised methodology of impedimetric biodiesel testing can be proposed as a fast and inexpensive method of fuel chemical stability evaluation, allowing for estimating the useful storage time of biodiesel in real conditions

Extended-gate field-effect transistor (EG-FET) with molecularly imprinted polymer (MIP) film for selective inosine determination

A novelrecognitionunitofchemicalsensorforselectivedeterminationoftheinosine,renaldisfunction biomarker,wasdevisedandprepared.Forthatpurpose,inosine-templatedmolecularlyimprinted polymer (MIP) film wasdepositedonanextended-gate field-effect transistor(EG-FET)signaltransducing unit. TheMIP film waspreparedbyelectrochemicalpolymerizationofbis(bithiophene)derivatives bearing cytosineandboronicacidsubstituents,inthepresenceoftheinosinetemplateandathiophene cross-linker.AfterMIP film deposition,thetemplatewasremoved,andwasconfirmed byUV\u2013visible spectroscopy.Subsequently,the film compositionwascharacterizedbyspectroscopictechniques,andits morphology andthicknessweredeterminedbyAFM.The finally MIP film-coated extended-gate fieldeffect transistor(EG-FET)wasusedforsignaltransduction.Thiscombinationisnotwidelystudiedinthe literature,despitethefactthatitallowsforfacileintegrationofelectrodepositedMIP film withFET transducer. The lineardynamicconcentrationrangeofthechemosensorwas0.5\u201350 \u3bcM withinosinedetect- ability of0.62 \u3bcM. Theobtaineddetectabilitycompareswelltothelevelsoftheinosineinbody fluids which areintherange0\u20132.9 mM forpatientswithdiagnoseddiabeticnephropathy,goutorhyperur- icemia, andcanreach25 mM incertaincases.Theimprintingfactorforinosine,determinedfrompie- zomicrogravimetricexperimentswithuseoftheMIP film-coated quartzcrystalresonator,wasfoundto be 5.5.Higherselectivityforinosinewithrespecttocommoninterferentswasalsoachievedwiththe present molecularlyengineeredsensingelement.Theobtainedanalyticalparametersofthedevised chemosensor allowforitsuseforpracticalsamplemeasurements

Potentiometric chemosensor for neopterin, a cancer biomarker, using an electrochemically synthesized molecularly imprinted polymer as the recognition unit

With an established procedure of molecular imprinting, a synthetic polymer receptor for the neopterin cancer biomarker was devised and used as a recognition unit of a potentiometric chemosensor. For that, bis-bithiophene derivatized with cytosine and bithiophene derivatized with boronic acid were used as functional monomers. The open-circuit potential (OCP) based transduction under flow-injection analysis conditions (FIA) determined neopterin in the concentration range of 0.15-2.5mM with the 22\u3bcM limit of detection (LOD) and 7.01(\ub10.15)mVmM-1 sensitivity indicating its potential suitability in clinical analysis applications. The molecularly imprinted polymer (MIP) film showed an appreciable apparent imprinting factor of ~6. The chemosensor successfully discriminated the interferences including the 6-biopterin and pterin structural analogs of neopterin as well as glucose and creatinine. Moreover, it determined neopterin in synthetic serum samples

Semi-Covalent Imprinting for Selective Protein Sensing at a Femtomolar Concentration Level

Protein imprinting is challenging mainly because of their large molecular size. It is very difficult [...