An optical genosensor based on Schiff base complex (Zn2+ salphen) DNA label and acrylic microspheres (AMs) as polymer support of the capturing DNA probe (cpDNA) was developed for dengue virus serotype 2 (DEN-2) detection via reflectance spectrophotometric method. The solid-state optical DNA biosensor showed high selectivity and specificity up to one-base mismatch in the target DNA sequence owing to the salphen chemical structure that is rich in localized electrons, and allowed π-π stacking interaction between stacked base pairs of double-stranded DNA (dsDNA). The reflectometric DNA microsensor demonstrated a broad linear detection range towards DEN-2 DNA from 1 × 10-15 M to 1 × 10-3 M with a low limit of detection (LOD) obtained at 1.21 × 10-16 M. The DNA biosensor gave reproducible optical response with a satisfactory relative standard deviation (RSD) at 3.1%, (n = 3), and the reflectance response was stable even after four regeneration cycles of the DNA biosensor. The optical genosensor was proven comparable with standard reverse transcription polymerase chain reaction (RT-PCR) in detecting DEN-2 genome acquired from clinical samples of serum, urine and saliva of dengue virus infected patients under informed consent. The developed reflectometric DNA biosensor is advantageous in offering an early DEN-2 diagnosis, when fever symptom started to manifest in patient.
The technique of Fourier transform infrared spectroscopy is widely used to generate spectral data for use in the detection of food contaminants. Monochloropropanediol (MCPD) is a refining process-induced contaminant that is found in palm-based fats and oils. In this study, a chemometric approach was used to evaluate the relationship between the FTIR spectra and the total MCPD content of a palm-based cooking oil. A total of 156 samples were used to develop partial least squares regression (PLSR), artificial neural network (nnet), average artificial neural network (avNNET), random forest (RF) and cubist models. In addition, a consensus approach was used to generate fusion result consisted from all the model mentioned above. All the models were evaluated based on validation performed using training and testing datasets. In addition, the box plot of coefficient of determination (R2), root mean square error (RMSE), slopes and intercepts by 100 times randomization was also compared. Evaluation of performance based on the testing R2 and RMSE suggested that the cubist model predicted total MCPD content with the highest accuracy, followed by the RF, avNNET, nnet and PLSR models. The overfitting tendency was assessed based on differences in R2 and RMSE in the training and testing calibrations. The observations showed that the cubist and avNNET models possessed a certain degree of overfitting. However, the accuracy of these models in predicting the total MCPD content was high. Results of the consensus model showed that it slightly improved the accuracy of prediction as well as significantly reduced its uncertainty. The important variables derived from the cubist and RF models suggested that the wavenumbers corresponding to the MCPDs originated from the -CH=CH2 or CH=CH (990-900 cm-1) and C-Cl stretch (800-700 cm-1) regions of the FTIR spectrum data. In short, chemometrics in combination with FTIR analysis especially for the consensus model represent a potential and flexible technique for estimating the total MCPD content of refined vegetable oils.
The non-ionic silicone surfactant (OFX 0309) has been applied in cloud point extraction for the extraction of triazine herbicides in food samples. Evidence has shown that the non-ionic silicone surfactant demonstrated a good performance as an extractor toward triazine herbicides. In this present study, OFX 0309 surfactant was combined with activated charcoal (AC) due to their valuable properties. Activated charcoal modified with non-ionic silicone surfactant coated with magnetic nanoparticles (AC-OFX MNPs) was synthesized and characterized by FT-IR, VSM, SEM, TEM and BET. This novel material was applied as a magnetic adsorbent for the pre-concentration and separation of triazine herbicides due to hydrophobic interaction between polysiloxane polyether of OFX 0309 surfactant and triazine herbicides. Under optimal conditions, the proposed magnetic solid phase extraction method using AC-OFX MNPs adsorbent was applied to extract triazine herbicides from selected milk and rice samples using high performance liquid chromatography coupled with diode array detector. The validation method revealed a good linearity (1 - 500 μg L-1) with the coefficient of determination (R2) in the range of 0.992-0.998 for the samples. The limits of detection (LOD) of the developed method were 0.04 - 0.05 µg L-1 (milk sample) and 0.02 - 0.05 µg L-1 (rice sample). The limits of quantification (LOQ) were 0.134 - 0.176 µg L-1 (milk sample) and 0.075 - 0.159 µg L-1 (rice sample). The recoveries of the triazine compounds ranged from 81% to 109% in spiked milk samples and from 81% to 111% in spiked rice samples, with relative standard deviations (RSD) values lower than 13.5% and 12.1% for milk and rice samples, respectively. To the best of our knowledge, this is the first study that have investigated the use of magnetic nanoparticles coated activated charcoal modified with OFX 0309 surfactant for pretreatment of triazine herbicides in food samples analysis for simultaneous separation of organic pollutants.
Different extraction procedures were evaluated to assess their potential for measuring volatile organic compounds (VOCs) from raw rubber materials. Four headspace sampling techniques (SHS, DHS, HS-SPME and µ-CTE) were studied. Each method was firstly optimised to ensure their reliability in performance. Passive sampling was also compared as a rapid identification of background VOCs. 352 VOCs were identified, 71 from passive sampling and 281 from active headspace sampling, with 62 not previously reported (hexanenitrile, octanone, decanal, indole, aniline, anisole, alpha-pinene as well as pentanol and butanol). The volatiles belonged to a broad range of chemical classes (ketones, aldehydes, aromatics, acids, alkanes, alcohol and cyclic) with their thermal effects (lower boiling points) greatly affecting their abundance at a higher temperature. Micro-chamber (µ-CTE) was found to be the most suitability for routine assessments due to its operational efficiency (rapidity, simplicity and repeatability), identifying 115 compounds from both temperatures (30 °C and 60 °C). Whereas, HS-SPME a widely applied headspace technique, only identified 75 compounds and DHS identified 74 VOCs and SHS only 17 VOCs. Regardless of the extraction technique, the highest extraction efficiency corresponded to aromatics and acids, and the lowest compound extraction were aldehyde and hydrocarbon. The interaction between techniques and temperature for all chemical groups were evaluated using two-way ANOVA (p-value is 0.000197) explaining the highly significant interactions between factors.
The development of free and total cholesterol nanobiosensors based on a single step electrochemical integration of gold nanoparticles (AuNPs), cholesterol oxidase (COx), cholesterol esterase (CE) and a mediator with polypyrrole (PPy) films is described. The incorporation of the various components in the PPy films was confirmed by chronopotentiometry, cyclic voltammetry (CV), scanning electron microscopy, energy dispersive X-ray analysis (SEM-EDX), and Fourier transformed infrared (FTIR) spectroscopy. The free cholesterol, PPy-NO3--Fe(CN)64--AuNPs-COx, nanobiosensor achieved a minimum detectable concentration of 5 μM, a linear concentration range of 5-25 μM and a sensitivity of 1.6 µA cm-2 µM-1 in 0.05 M phosphate buffer (pH 7.00). For the total cholesterol, PPy-NO3--Fe(CN)64--AuNPs-COx-CE, nanobiosensor which also involved the co-incorporation of cholesterol esterase (CE) with the other components, the achieved performances include a minimum detectable total cholesterol concentration of 25 μM, a broader linear concentration range of 25-170 μM and a lower sensitivity of 0.1 µA µM-1 cm-2. Owing to its high selectivity, the presence of common interferants did not affect the total cholesterol measurement with the PPy-NO3--Fe(CN)64--AuNPs-COx-CE nanobiosensor. Both nanobiosensors were successfully used for direct and indirect determination of total cholesterol in human blood serum samples.
Persimmon (Diospyros kaki L.) is one of the most important fruits that has been consumed for its medicinal properties due to the presence of some active metabolites, particularly polyphenols and carotenoids. Previously described methods, including HPLC, were limited in the determination of metabolites in different persimmon varieties. The present study shows the evaluation and the differences among persimmon polar and non-polar extracts by 1H NMR-based metabolomics approach. The hierarchical clustering analysis (HCA) based on score values of principal component analysis (PCA) model was used to analyze the important compounds in investigated fruits. The 1H NMR spectrum of persimmon chloroform (CDCl3) extracts showed different types of compounds as compared to polar methanol-water (CD3OD-D2O) ones. Persimmons growing in Israel were clustered different from those growing in Korea with the abundance of phenolic compounds (gallic, caffeic and protocathecuic acids), carotenoids (β-cryptoxanthin, lutein, and zeaxanthin), amino acids (alanine), maltose, uridine, and fatty acids (myristic and palmitoleic acids). Glucose, choline and formic acid were more prominent in persimmon growing in Korea. In CD3OD-D2O and CDCl3 persimmon extracts, 43 metabolites were identified. The metabolic differences were shown as well on the results of bioactivities and antioxidant capacities determined by ABTS, FRAP, CUPRAC and DPPH assays. The presented methods can be widely used for quantitation of multiple compounds in many plant and biological samples especially in vegetables and fruits.
In this study, a simple sample preparation method was developed for the determination of tri-and hexavalent chromium in water samples. It utilizes a pre-heated customized glass tube (CGT), to supply the heat energy required for the reaction of Cr(III) with ammonium pyrrolidinedithiocarbamate (APDC). The products of the Cr complexes, tris(1-pyrrolidinecarbodithioato)chromium(III) and bis(1-pyrrolidinecarbodithioato)[1-pyrrolidinecarbodithio(thioperoxoato)]chromium(III) were chromatographed with Shimadzu LC-20AT and Zobax Eclipse C18 (150mm × 4.6mm, 5µm) column using ACN: Water, (7:3, v/v) as the mobile phase. The concentration of Cr(III) ranged from 0.06mgL-1to 0.09mgL-1and that of Cr(VI) was between 0.02mgL-1to 0.04mgL-1in the samples. Percentage recoveries from spiked real samples were between 87% (tap water) to 110% (wastewater) for Cr(III) and 92% (pond water) to 117% (tap water) for Cr(VI). The limits of detection (LODs) were 0.0029mgL-1and 0.0014mg/L-1for Cr(III) Cr(VI) respectively. While the limits of quantitation (LOQs), were 0.0098mgL-1and 0.0047mgL-1for Cr(III) and Cr(VI) respectively. Method precision (RSD (%)) was 3.3% and 3.5% for Cr(III) and Cr(VI) respectively. The developed method was applied for the speciation analysis of chromium in drinking water, tap water, wastewater, river water, and pond water samples. Our findings proved the method is simple and inexpensive. The method was validated by the analysis of a certified reference material (CRM) SLRS-4. The percentage recovery and RSD(%) from the spiked CRM were 91% and 115% and 0.32% and 1.4% for Cr(III) and Cr(VI) respectively.
In this present study, magnetic nanoparticles (MNPs) nanocomposites modified with polyaniline (PANI) coated newly synthesised dicationic ionic liquid (DICAT) forming MNP-PANI-DICAT were successfully synthesised as new generation material for magnetic solid phase extraction (MSPE). MNP-PANI-DICAT was characterised by FT-IR NMR, CHN, BET, SEM, TEM, and VSM techniques and the results were compared with MNP-PANI and native MNP. This new material was applied as a magnetic adsorbent for the pre-concentration and separation of polycyclic aromatic hydrocarbons (PAHs) due to the π-π interaction between polyaniline shell and dicationic ionic liquid (DICAT) with PAHs compounds. Under the optimal conditions, the proposed method was evaluated and applied for the analysis of PAHs in environmental samples using gas chromatography-mass spectrometry (GC-MS). The validation method showed good linearity (0.005-500µgL-1) with the coefficient of determination (R2) > 0.999. The limits of detection (LOD) and quantification (LOQ) of the developed method (MNP-PANI-DICAT-MSPE) were in the range of 0.0008-0.2086µgL-1and 0.0024-0.6320µgL-1, respectively. The enrichment factor (EF) of PAHs on MNP-PANI-DICAT-MSPE were in the range of 7.546-29.632. The extraction recoveries of natural water, sludge, and soil samples were ranged from 80.2% to 111.9% with relative standard deviation (RSD) less than 5.6%. The newly synthesised MNP-PANI-DICAT possess good sensitivity, reusability, and fast extraction of PAHs under the MSPE procedure in various environmental samples.
Electro-mediated microextraction (EMM) combined with micro-high performance liquid chromatography-ultraviolet detection was successfully developed for the determination of selected phenols, namely 4-chlorophenol (4CP), 2-nitrophenol (2NP) and 2,4-dichlorophenols (2,4 DCP) in water. A solvent-impregnated agarose gel disc was utilized as a solvent holder in this study. Under optimum extraction conditions, the method showed good linearity in the range of 0.1-250µgL-1, 0.3-250µgL-1and 0.2-500µgL-1for 4CP, 2NP and 2,4 DCP, respectively with correlation coefficients of ≥ 0.9975, ultra-trace LODs (0.03-0.1µgL-1) and satisfactory relative recovery average (85.0-114.1%) for the analysis of selected phenols. The proposed method was rapid and eco-friendly as the solvent holder was constructed using minute amounts of extraction solvent immobilized within the biodegradable agarose gel disc. A comparative microextraction technique termed solvent-impregnated agarose gel liquid phase microextraction (AG-LPME) was re-optimized and validated for the extraction of phenols in water. The method offered good linearity, ultra-trace LODs ranging 0.1-0.5µgL-1and satisfactory average of relative recovery (86.1-114.1%). The EMM was superior in terms of sensitivity and time-effectiveness compared to AG-LPME. Both techniques combine extraction and pre-concentration in mini-scaled approaches using an eco-friendly solvent holder that fulfil the green chemistry concept.
A vortex-assisted liquid-liquid-liquid microextraction method followed by high performance liquid chromatography-diode array detection for the determination of fourteen phenolic acids (cinnamic, m-coumaric, chlorogenic, syringic, ferulic, o-coumaric, p-coumaric, vanillic, p-hydroxybenzoic, caffeic, 2, 4-dihydroxybenzoic, sinapic, gentisic and gallic acids) in honey, iced tea and canned coffee drink samples has been developed. The separation was achieved using a Poroshell 120-EC-C18 column under a gradient elution at a flow rate of 0.6mLmin-1 and mobile phase composed of methanol and acetic acid (1%, v/v). Under the optimum chromatographic conditions, the fourteen phenolic acids were separated in less than 32min. The extraction was performed using a small volume (400µL) of ternary organic solvents (1-pentanol, propyl acetate and 1-hexanol) dispersed into the aqueous sample (10mL) and assisted by vortex agitation (2500rpm for 45s), the analytes were next back-extracted from the organic solvent using 0.02M KOH (40µL) with vortex speed and time of 2500rpm and 60s, respectively. Under these conditions, enrichment factors of 30-193-fold were achieved. The limits of detection (LODs) were 0.05-0.68µgL-1. Recoveries in honey, iced tea and canned coffee drinks were in the range 72.2-112%. The method was successfully applied for the determination of the phenolic acids in honey, iced tea and canned coffee drinks.
This research work demonstrates compositional engineering of an organic-inorganic hybrid nano-composites for modifying absolute threshold of humidity sensors. Vanadyl-2,9,16,23-tetraphenoxy-29H,31H-phthalocyanine (VOPcPhO), an organic semiconductor, doped with Titanium-dioxide nanoparticles (TiO2NPs) has been employed to fabricate humidity sensors. The morphology of the VOPcPhO:TiO2nano-composite films has been analyzed by atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). The sensors have been examined over a wide range of relative humidity i.e. 20-99% RH. The sensor with TiO2(90nm) shows reduced sensitivity-threshold and improved linearity. The VOPcPhO:TiO2(90nm) nano-composite film is comprised of uniformly distributed voids which makes the surface more favorable for adsorption of moisture content from environment. The VOPcPhO:TiO2nano-composite based sensor demonstrates remarkable improvement in the sensing parameter when equated with VOPcPhO sensors.
Estuary sediments are one of the important components of coastal ecosystems and have been regarded as a sink for various types of organic pollutants. Organic pollutants such as endocrine disrupting compounds (EDCs) which have been associated with various environmental and human health effects were detected in the estuary sediment at trace level. Considering various interferences that may exist in the estuarine sediment, a sensitive and selective method, capable of detecting multiclass EDC pollutants at the trace levels, needs to be developed and optimized to be applied for environmental analysis. A combination of Soxhlet extraction followed by offline solid phase extraction (SPE) cleaned up with detection based on LC triple quadrupole MS was optimized and validated in this study. The targeted compounds consisted of ten multiclass EDCs, namely, diclofenac, primidone, bisphenol A, estrone (E1), 17β-estradiol (E2), 17α-ethynylestradiol (EE2), 4-octylphenol (4-OP), 4-nonylphenol (4-NP), progesterone, and testosterone. The method showed high extraction efficiency with percentage of recovery from 78% to 108% and excellent sensitivity with detection limit between 0.02ngg-1 and 0.81ngg-1. Excellent linearity from 0.991 to 0.999 was achieved for the developed compounds and the relative standard deviation was less than 18%, an indication of good precision analysis. Evaluation of the matrix effects showed ionization suppression for all the developed compounds. Verification of the method was carried out by analyzing the estuarine sediment collected from Langat River. The analyzed estuarine sediments showed a trace concentration of diclofenac, bisphenol A, progesterone, testosterone, primidone, and E1. However, E2, EE2, 4-OP, and 4-NP were below the method's detection limit. Diclofenac exhibited the highest concentration at 2.67ngg-1 followed by bisphenol A (1.78ngg-1) while E1 showed the lowest concentration at 0.07ngg-1.
Molecularly imprinted polymer (MIP) was employed as sorbent in ultrasound assisted emulsification molecularly imprinted polymer micro-solid phase extraction (USAE-MIP-µ-SPE) of bisphenol A (BPA) in water, beverages and the aqueous liquid in canned foods prior to high performance liquid chromatography-diode array detector (HPLC-DAD) analysis. Several effective variables, such as types of emulsification solvent and its volume, types of desorption solvent and its volume, salting out effect, pH of sample solution, mass of sorbent, extraction and desorption time, and sample volume, were optimized comprehensively. Under the optimized USAE-MIP-µ-SPE and HPLC-DAD conditions, the method demonstrated good linearity over the range of 0.5-700μgL-1with a coefficient determination of R2=0.9973, low limit of detection (0.07μgL-1), good analyte recoveries (82.2-118.9%) and acceptable RSDs (0.7-14.2%, n=3) with enrichment factor of 49. The method was applied to thirty samples of drinking water, mineral water, river water, lake water, as well as beverages and canned foods, the presence of BPA was identified in four samples. The proposed method showed good selectivity and reusability for extraction of BPA, and hence the USAE-MIP-µ-SPE is rapid, simple, cost effective and environmentally friendly.
The identification and quantification of chemicals play a vital role in evaluation and surveillance of environmental health and safety. However, current techniques usually depend on costly equipment, professional staff, and/or essential infrastructure, limiting their accessibility. In this work, we develop paper-based capacitive sensors (PCSs) that allow simple, rapid identification and quantification of various chemicals from microliter size samples with the aid of a handheld multimeter. PCSs are low-cost parallel-plate capacitors (~$0.01 per sensor) assembled from layers of aluminum foil and filter paper via double-sided tape. The developed PCSs can identify different kinds of fluids (e.g., organic chemicals) and quantify diverse concentrations of substances (e.g., heavy metal ions) based on differences in dielectric properties, including capacitance, frequency spectrum, and dielectric loss tangent. The PCS-based method enables chemical identification and quantification to take place much cheaply, simply, and quickly at the point-of-care (POC), holding great promise for environmental monitoring in resource-limited settings.
The low conductivity of separation electrolytes employed in nonaqueous capillary electrophoresis (NACE) limits the use of on-line sample concentration or stacking by field enhancement. Herein, micelle-to-solvent stacking (MSS) was performed by the simple injection of a micellar solution plug prior to electrokinetic injection of sample prepared under field-enhanced stacking conditions (known as field-enhanced sample injection, FESI). The proposed approach allowed a 214-625-fold improvement in peak signals for targeted anticancer drugs (e.g., tamoxifen) and its major metabolites in NACE using 100% methanol-based separation electrolyte that comprised of 7.5mM deoxycholic acid sodium salt, 15mM acetic acid and 1mM 18-crown-6. These improvements yielded tamoxifen and its metabolites with 2-5 times better stacking efficiency as compared to those obtained without micellar solution injection or FESI only. This is comparable to the results typically achieved when FESI is combined with isotachophoresis (electrokinetic supercharging). The FESI-MSS-NACE was tested for the measuring levels of target drugs in plasma. The analytical figures of merit are also reported.
A new sample preparation method, ion-pair vortex assisted liquid-liquid microextraction (VALLME-BE), for the determination of a highly polar anti-diabetic drug (metformin) in plasma sample was developed. The VALLME-BE was performed by diluting the plasma in borate buffer and extracted to 150µL 1-octanol containing 0.2M di-(2-ethylhexyl)phosphoric acid as intermediate phase. The drug was next back-extracted into 20µL of 0.075M HCl solution. The effects of pH, ion-pair concentration, type of organic solvent, volume of extraction phases, ionic strength, vortexing and centrifugation times on the extraction efficiency were investigated. The optimum conditions were at pH 9.3, 60s vortexing and 2min centrifugation. The microextract, contained metformin and buformin (internal standard), was directly injected into a HPLC unit using C1 column (250mm×4.6mm×10µm) and detected at 235nm. The method was validated and calibration curve was linear with r2>0.99 over the range of 20-2000µgL-1. The limits of detection and quantitation were 1.4 and 4.1µgL-1, respectively. The accuracy was within 94.8-108% of the nominal concentration. The relative standard deviation for inter- and intra-day precision was less than 10.8%. The method was conveniently applied for the determination of metformin in plasma samples.
Lateral flow assays (LFAs) hold great promise for point-of-care testing, especially in resource-poor settings. However, the poor sensitivity of LFAs limits their widespread applications. To address this, we developed a novel device by integrating dialysis-based concentration method into LFAs. The device successfully achieved 10-fold signal enhancement in Human Immunodeficiency Virus (HIV) nucleic acid detection with a detection limit of 0.1nM and 4-fold signal enhancement in myoglobin (MYO) detection with a detection limit of 1.56ng/mL in less than 25min. This simple, low-cost and portable integrated device holds great potential for highly sensitive detection of various target analytes for medical diagnostics, food safety analysis and environmental monitoring.
An effective electrode was developed based on electromembrane extraction (EME) and square wave voltammetry (SWV) for simultaneous separation, pre-concentration and determination of lead (II) (Pb(II)) ions in complex aqueous samples. Electrochemically reduced graphene oxide-graphite reinforced carbon (ErGO-GRC) was utilized in conjunction with the SWV. Pb(II) ions were extracted from an aqueous sample solution into an acidic acceptor phase (1M HCl) in the lumen of the polyvinylidene fluoride (PVDF) membrane bag by the application of voltage of maximum 6 V across the supported liquid membrane (SLM), consisting of organic solvent and di-(2-ethylhexyl)phosphoric acid (D2EHPA). The parameters affecting the EME were optimized for Pb(II) ions. The optimum EME conditions were found to be 20% D2EHPA in 1-octanol impregnated in the wall of PVDF membrane (PVDF17) as the SLM, extraction time of 20 min, pH of sample solution of 8 and a voltage of 5 V. The PVDF-ErGO-GRC electrode system attained enrichment factors of 40 times and 80% of extraction with relative standard deviations (n=5) of 8.3%. Good linearity ranging from 0.25 to 2 nM with coefficients correlation of 0.999 was obtained. The Pb(II) ions detection limit of PVDF-ErGO-GRC electrode was found to be 0.09 nM. The newly developed single setup electrochemical system was applied to complex aqueous samples such as tap, river and sea water to evaluate the feasibility of the method for applications.
This study describes the synthesis, characterization and application of a new chrysin-based silica core-shell magnetic nanoparticles (Fe3O4@SiO2-N-chrysin) as an adsorbent for the preconcentration of Cu(II) from aqueous environment. The morphology, thermal stability and magnetic property of Fe3O4@SiO2-N-chrysin were analyzed using FTIR, FESEM, TEM, XRD, thermal analysis and VSM. The extraction efficiency of Fe3O4@SiO2-N-chrysin was analyzed using the batch wise method with flame atomic absorption spectrometry. Parameters such as the pH, the sample volume, the adsorption-desorption time, the concentration of the desorption solvent, the desorption volume, the interference effects and the regeneration of the adsorbent were optimized. It was determined that Cu(II) adsorption is highly pH-dependent, and a high recovery (98%) was achieved at a pH 6. The limit of detection (S/N=3), the limit of quantification (S/N=10), the preconcentration factor and the relative standard deviation for Cu(II) extraction were 0.3 ng mL(-1), 1 ng mL(-1), 100 and 1.9% (concentration=30 ng mL(-1), n=7), respectively. Excellent relative recoveries of 97-104% (%RSD<3.12) were achieved from samples from a spiked river, a lake and tap water. The MSPE method was also validated using certified reference materials SLRS-5 with good recovery (92.53%).
In this report, silver nanoparticles (Ag NPs) were successfully deposited on graphene oxide (GO) sheets to form GO-Ag nanocomposite using garlic extract and sunlight and the nanocomposite modified glassy carbon (GC) electrode was applied as an electrochemical sensor for the detection of nitrite ions. The formation of GO-Ag nanocomposite was confirmed by using UV-visible absorption spectroscopy, TEM, XRD and FTIR spectroscopy analyses. Further, TEM pictures showed a uniform distribution Ag on GO sheets with an average size of 19 nm. The nanocomposite modified electrode produced synergistic catalytic current in nitrite oxidation with a negative shift in overpotential. The limit of detection (LOD) values were found as 2.1 µM and 37 nM, respectively using linear sweep voltammetry (LSV) and amperometric i-t curve techniques. The proposed sensor was stable, reproducible, sensitive and selective toward the detection nitrite and could be applied for the detection of nitrite in real water sample.