Phenols In Real Samples Research Articles

A novel extended gate ISFET design for biosensing application compatible with standard CMOS

This paper describes a novel design of ISFET, which uses a hafnium oxide-coated aluminum pad surface as a floating/extended gate. The design was realized using standard CMOS technology followed by BEOL post treatment. The ISFET was designed to operate in subthreshold mode and has subthreshold slope of 108 mV/dec, pH sensitivity of 55 mV/pH and temporal stability 0.008 mV/min. Based on the ISFET, an enzymatic biosensor for detection of phenols in real samples was demonstrated. The reported design allows to significantly improve the internal characteristics of ISFET, leading to predictable high-performance biosensors formed on a basis of standard CMOS-technology.

Fabrication of Luminescent Microtiterplate Using Terbium Complex for Phenol Screening in Seawater Samples.

Tb(III)-2-aminoterphthalate complex Tb2-(ATPh)3 was synthesized and characterized using FT-IR, thermal analysis and elemental analysis. Tb2(ATPh)3 microtiter plate was fabricated through embedding Tb(III) complex in polyvinyl chloride membrane and used for environmental determination of phenol in sea water samples. The calculated detection (DL), quantification (QL) limits, and binding constant (KD) were 00.63 µmol L- 1, 2.10 µmol L- 1 and 1.32 × 104 mol- 1 L, respectively. The fabricated microtiter plates exhibited high selectivity towards phenol over other hydrocarbon compounds. Furthermore, AGREE metric tool was used to assess the method's green nature as well as its practicability and applicability. These merit outcomes provide that the new method for phenol detection was environmentally benign and safe to humans. The prepared Tb2(ATPh)3 MTP was validated through using gas chromatography for monitoring phenol in Suez Bay water accurately with high precision. The obtained results encouraged using Tb2(ATPh)3 MTP for efficient, fast, selective, and direct screening of phenol in real samples.

The Investigation of Adsorption Behaviors of Nine Ionic Liquid-Immobilized Silicas on Two Phenols in Water and Soil samples

An experimental study on adsorption of phenol and o-cresol using ionic liquid-immobilized silica contained different functional groups was carried out. The effects of various operating parameters such as type of ionic liquid group, different adsorption time and ambient temperatures, different solvents in solid phase extraction (SPE) process and several aqueous ion solutions on adsorption of two phenols had been experimentally investigated. It was found that amino ionic liquid-immobilized silica had the highest adsorption efficiency and stability. The optimized adsorption conditions were 15 min under 35oC. In SPE, the acidity solution such as ethanol-HCl (0.1% vol.) and NaH2PO4 could reduce the adsorption efficiency of sorbents. Finally, the sorbent was applied to determining two phenols in real samples and relative standard deviation (RSD) less than 6.14% showed the high precision.

Preparation and Application of Polyimide Coated Stir Bar for Extraction of Phenols in Environmental Water Samples

Abstract A polyimide coated stir bar for sorptive extraction (SBSE) was prepared by immersion precipitation method and evaluated by using 5 phenols and chlorinated phenols as model samples. The highest extraction efficiency was achieved among all commercial extraction phases of SBSE reported. Experimental parameters including stirring speed, ionic strength, extraction temperature, extraction time, desorption temperature and time were optimized. Under the optimal conditions such as 100 mL of sample, 30% NaCl, extraction time of 30 min, stirring speed of 800 rpm and extraction temperature of 25 °C, the target compounds were recovered by thermal desorption at 300 °C for 4 min. More than two orders of magnitude of linearity were obtained (R ≥ 0.9995). LOQs (S/N = 10) were 0.028–0.123 μg L−1, and RSDs were in the range of 1.6%–9.7%. The polyimide SBSE coupled with gas chromatography-mass spectrometry was applied to the extraction and analysis of phenols in real samples, including tap water, sea water, and waste water. It was found that the polyimide SBSE showed high selectivity towards polar compounds and high thermostability up to 350 °C.

Electrocatalytic Determination of Hydrazine and Phenol Using a Carbon Paste Electrode Modified with Ionic Liquids and Magnetic Core‐shell Fe3O4@SiO2/MWCNT Nanocomposite

AbstractA carbon paste electrode was modified with 2‐(4‐Oxo‐3‐phenyl‐3,4‐dihydroquinazolinyl)‐N′‐phenyl‐hydrazinecarbothioamide, magnetic coreshell Fe3O4@SiO2/MWCNT nanocomposite and ionic liquid (n‐hexyl‐3‐methylimidazolium hexafluoro phosphate). The electro‐oxidation of hydrazine at the surface of the modified electrode was studied using electrochemical approaches. This modified electrode offers a considerable improvement in voltammetric sensitivity toward hydrazine, compared to the bare electrode. Square wave voltammetry (SWV) exhibits a linear dynamic range from 7.0×10−8 to 5.0×10−4 M and a detection limit of 40.0 nM for hydrazine. The diffusion coefficient and kinetic parameters (such as electron transfer coefficient and the heterogeneous rate constant) for hydrazine oxidation were also determined. The prepared modified electrode exhibits a very good resolution between the voltammetric peaks of hydrazine and phenol that makes it suitable for the detection of hydrazine in the presence of phenol in real samples.

Fenton reaction-triggered colorimetric detection of phenols in water samples using unmodified gold nanoparticles

This work demonstrates a rapid and sensitive colorimetric detection of phenols by using single-stranded DNA (ssDNA)-regulated gold nanoparticles (AuNPs) as indicators. AuNPs can be stabilized in the presence of ssDNA through electrostatic repulsion, which prevents the salt-induced aggregation of AuNPs in solution. However, hydroxyl radicals (OH) generated by the Fenton reaction can cleave the ssDNA on the nanoparticle surface into mono- or oligonucleotide fragments, disrupting AuNPs stability. Phenolic compounds are known to be capable of being degraded or oxidized by OH produced by Fenton reaction. Thus, phenols can effectively scavenge OH to avoid ssDNA cleavage, protecting AuNPs from salt-induced aggregation. The ability of phenols to scavenge OH provides a quantitative basis for phenol sensing. In this study, catechol and hydroquinone were selected as analytes and detected using the proposed ssDNA–AuNPs colorimetric probe. The detection sensitivities of the colorimetric sensor are 0.2–7.0μM for catechol and 2.7–19μM for hydroquinone. The proposed bioassay eliminates tedious sample pretreatment and offers favorable sensitivity and selectivity for targets in the presence of other investigated metal ions and organic molecules. The detection limits are 0.11μM for catechol and 1.6μM for hydroquinone, with relative standard deviations of 3.7% for catechol and 4.8% for hydroquinone. The recovery rate of catechol in real water samples ranges from 95% to 116%, confirming the application potential of the method to measure phenols in real samples.

Electrochemical determination of sulfite and phenol using a carbon paste electrode modified with ionic liquids and graphene nanosheets: Application to determination of sulfite and phenol in real samples

Benzoylferrocene was used to construct a modified-graphene paste electrode. Also, hydrophilic ionic liquid (n-hexyl-3-methylimidazolium hexafluoro phosphate) was used as a binder to prepare the modified electrode. The electro-oxidation of sulfite at the surface of the modified electrode was studied using electrochemical approaches. This modified electrode offers a considerable improvement in voltammetric sensitivity toward sulfite, compared to the bare electrode. Square wave voltammetry (SWV) exhibits a linear dynamic range from 5.0×10−8 to 2.5×10−4 M and a detection limit of 20.0nM for sulfite. The diffusion coefficient and kinetic parameters (such as electron transfer coefficient and the heterogeneous rate constant) for sulfite oxidation were also determined. The prepared modified electrode exhibits a very good resolution between the voltammetric peaks of sulfite and phenol that makes it suitable for the detection of sulfite in the presence of phenol in real samples.

A reduced graphene oxide based biosensor for high-sensitive detection of phenols in water samples

Laccase (Lac) from Rhus vernificera was covalently immobilized onto 1-aminopyrene (1-AP) functionalized reduced graphene oxides (rGOs)-modified glassy carbon electrode by encapsulation with chitosan. The biosensor was characterized with respect to the optimum pH and polarized potentials for the determination of phenols, and its response time, sensitivity, linear range, detection limit, and stability. Hydroquinone and catechol were selected as the analytes and detected based on the direct electron transfer behavior of Lac and its enzymatic oxidation of analyte. The sensitivities of the electrode were 14.16, 15.79μAmM−1 with linear ranges of 3–2000, 15–700μM for hydroquinone and catechol, respectively. The detection limits (S/N=3) were 2 and 7μM for hydroquinone and catechol, respectively with a fast response time (t95%) of less than 5s. Moreover, the immobilized Lac showed high affinity to hydroquinone and catechol with Kmapp values of 5 and 0.3mM, respectively. As a consequence, the biosensor demonstrated suitable stability (ca. 7 days; over 300 determinations) and good repeatability with a relative standard deviation of 3.96%. The recovery study of hydroquinone in real water samples gave values from 82.7%±10% to 105.9%±8%, confirming its application potential in the measurement of phenols in real samples.

Biosensors Based on Poly(vinylimidazole) Microparticles

AbstractThe use of poly(vinylimidazole) microparticles as immobilization system of the enzymes used as biological material in the fabrication of glucose and catechol biosensors is proposed. Biosensors analytical properties were studied using different working media: aqueous buffer solution and solvents with different hydrophobicity such as dioxane (lgP=−1.1), acetonitrile (lgP=−0.33), ethanol (lgP=−0.24), chloroform (lgP=2.0) and hexane (lgP=3.5) as well as different mixtures of acetonitrile/aqueous buffer solution. Sensitivity, detection limit, linear range and response time were reported for both biosensors in both media. The performance of the biosensors in the analysis of glucose and phenols in real samples was successful.

Highly sensitive amperometric biosensor based on a biocompatible calcium phosphate cement

Brushite is a biocompatible calcium phosphate mineral with properties of solid electrolyte. In this study we take advantage of this characteristic to develop an enzymatic amperometric biosensor based on brushite cement. The biosensor was prepared by immobilizing tyrosinase (PPO) on a brushite cement layer which was subsequently cross-linked with glutaraldehyde (GA) on the surface of a glassy carbon electrode. The system was optimized for the detection of phenolic compounds in both aqueous and non-aqueous solutions. Several variables involved in the enzyme immobilization method such as glutaraldehyde cross-linking time, PPO/brushite ratio and thickness of the brushite film were investigated. Furthermore, the effects of the pH, temperature and applied potential on the biosensor performance were also optimized. On the other hand, the biosensor analytical properties were studied in presence of different organic solvents: dioxane, acetonitrile and ethanol. In both, phosphate buffer solution (PBS) and acetonitrile/PBS solution, the biosensor exhibits a rapid response (12s); a wide linear range (0.001–3μM and 0.007–2μM respectively); low detection limit (1 and 2nM respectively); and high sensitivity (46.6 and 28.6AM−1cm−2 respectively). The performance of the biosensor in the analysis of phenols in real samples was successful.

Effect of DNA on the Peroxidase Based Biosensor for Phenol Determination in Waste Waters

The influence of different additives, like bovine serum albumin (BSA), polyethylenimine (PEI) and DNA, on the sensitivity and operational stability of a phenol biosensor based on peroxidase immobilized on silica-titanium and mixed in carbon was studied. The best results were found with electrodes containing DNA in the paste, although with BSA better results were obtained, compared to the electrode without additives. The response of biosensor incorporating DNA decayed ca. 50 % after 3 to 4 days of use, but it then remained constant for 25 days of daily use, when stored in a phosphate buffer solution under refrigeration between experiments. Original performance was recovered by simply substituting the used paste for a new portion of stock paste. The high sensitivity for phenol due to the immobilization of peroxidase on silica-titanium and the increase of stability of the biosensor provided by DNA addition were essential for the successful determination of phenol in real samples, with an average of 104.8 % recovery.

Continuous membrane extraction of phenols from crude oils followed by high-performance liquid chromatographic determination with electrochemical detection

On-line coupling of devices for non-chromatographic separation to chromatographic analysis systems affords a substantial improvement in the handling of organic samples whose physicochemical characteristics hinder their treatment. Here we report for the first time a simple and rapid automatic method for the determination of phenols in crude oil using high-performance liquid chromatography with electrochemical detection. The method involves minimum sample handling. Before the chromatographic process, phenols are separated from the matrix with a silicone membrane in a device coupled directly to the chromatographic system. The separation process across the membrane and later transfer of the analytes separated from the matrix to the chromatographic system are controlled automatically. The proposed procedure has been used successfully for the determination of phenols in real samples of crude oil without the need for complicated pretreatment steps.