A wearable electrode based on copper nanoparticles for rapid determination of paraquat.

The application of copper-based nanoparticles synthesized via green synthesis and their integration with a wearable electrode is reported for designing a flexible catalytic electrode on a glove for onsite electroanalysis of paraquat. A copper precursor and an orange extract from Citrus reticulata are used to synthesize an economical electrocatalytic material for supporting the selective and sensitive detection of paraquat. The electrode yields multidimensional fingerprints due to two redox couples in a square wave voltammogram, corresponding to the presence of paraquat. The developed lab-on-a-finger sensor provides the fast electroanalysis of paraquat within 10 s, covering a wide range from 0.50 to 1000 µM, with a low detection limit down to 0.31 µM and high selectivity. It is also possible to use this sensor at a fast scan rate as high as 6 V s-1 (< 0.5 s for a scan). This wearable glove sensor allows the user to directly touch and analyze samples, such as surfaces of vegetables and fruits, to screen the contamination. It is envisioned that these glove-embedded sensors can be applied to the on-site analysis of food contamination and environments.

One-step electrodeposition of poly(o-phenylenediamine)-Zn composite on plaswood propeller as an extraction device for polycyclic aromatic hydrocarbons in coffee.

Coffee beans can be contaminated during roasting by polycyclic aromatic hydrocarbons (PAHs), some of which have been classified as carcinogens. An extraction device for PAHs in coffee drinks was designed with six compact DC motors rotating six sorbents. The sorbents were plaswood propellers modified by one-step electrodeposition of a poly(ortho-phenylenediamine) and Zn composite (PoPD-Zn). Benzo(a)anthracene (BaA), chrysene (Chry), benzo(b)fluoranthene (BbF), and benzo(a)pyrene (BaP) were chosen as representative PAHs. Scanning electron micrographs of the PoPD-Zn showed a porous structure. The extracted PAHs were quantified by gas chromatography coupled with a flame ionization detector. Detected concentrations of PAHs in coffee drink samples were as follows: BaA 1.4 ± 0.4 to 16.5 ± 0.8 µg L-1; Chry 0.5 ± 0.2 to 2.1 ± 0.5 µg L-1; BbF 2.2 ± 0.6 µg L-1; and BaP 6.2 ± 1.0 µg L-1. Good recoveries ranging from 82.7 ± 1.9% to 99.0 ± 0.5% were obtained.

A polypyrrole-cotton pad sorbent as micro-solid phase extractor enclosed in tea bag envelope for determination of synthetic antioxidants in non-alcoholic beverage products.

A polypyrrole (PPy)-cotton pad sorbent enclosed in tea bag envelope was developed and used in micro-solid phase extraction (µ-SPE) for the determination of butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). After extraction, the extract was qualified and quantified by a gas chromatograph equipped with a flame ionization detector (GC-FID). Parameters influencing this developed method and the efficiency of µ-SPE were studied and optimized. Under the optimal conditions, the developed method provided good linearity in a concentration range of 0.100-100 µg L-1 for BHA and 0.050-50 µg L-1 for BHT, respectively. The limits of detection were 39.27 ± 0.52 ng L-1 for BHA and 16.96 ± 0.17 ng L-1 for BHT. Satisfactory relative recoveries of BHA and BHT were achieved in the range from 86.8 ± 1.9 to 117.1 ± 2.3% with acceptable relative standard deviation (RSD) below 8.1%. Good reproducibility was obtained with RSDs < 3.1%, for n = 6. The developed adsorbent is easy to operate, low cost, eco-friendly, reusable, with high extraction efficiency, and was successfully applied in the simultaneous synthetic antioxidant determination of non-alcoholic beverage samples.

Single-step salt-template-based scalable production of 2D carbon sheets heterostructured with nickel nanocatalysts for lowering overpotential of hydrogen evolution reaction.

Non-precious metals have been considered as suitable alternatives for high-performance hydrogen evolution reactions (HER). Although the incorporation of carbon substances is shown to improve the number of active sites, electron transfer pathways, and long-term stability, there have been rare reports on their single-step scalable production. Herein, we realize free-standing two-dimensional (2D) carbon sheets heterostructured with nickel (Ni) nanocatalysts by pyrolyzing ultrathin layers of acetate tetrahydrate (i.e. the single precursor for both Ni and C sources) over water-soluble salt crystals. Such a salt-templated methodology is environmentally friendly and readily scalable without the implementation of sophisticated equipment. The resulting 2D carbon sheets exhibit an average small thickness of âˆ¼ 3 nm and lateral dimensions with tens of micrometers, where a large number of nano-sized Ni particles with an average diameter of 14 nm are uniformly dispersed. Such 2D Ni-C sheets demonstrate a small overpotential of 111 mV at 10 mA/cm2 and a low Tafel slope of 86 mV/dec for HER in 1 M KOH, which is significantly improved over those of reported non-precious metals composited with carbon substances. This work offers new insight into the design and practical production of non-precious metal matrixes for economical HER.

Waste polystyrene foam-derived sorbent for determining bisphenol-A from canned beverages.

Polystyrene-based products are widely used in industrial and daily activities, but their subsequent disposal can negatively affect the environment. This work focuses on reducing polystyrene waste into useful material. A waste-derived polystyrene sorbent (WDPS) was fabricated and successfully applied to determine bisphenol-A in canned beverages. High-performance liquid chromatography with a diode-array detection (HPLC-DAD) was applied to quantify bisphenol-A. Good linearity at a concentration range of 2.5-50 µg L-1 was achieved. The limit of detection was 0.93 ± 0.02 µg L-1. Good precision (RSDs < 1.6 %, 4 concentrations, n = 6) in spiked coconut juice samples were obtained. The contamination of BPA in canned beverage samples were found in the range of 6.3 ± 0.2 µg L-1 to 27.0 ± 1.0 µg L-1 with recoveries in the range of 70.4 ± 1.6 % to 82.4 ± 0.4 %. This proposed method also offers reduced polystyrene waste, reuse as a sorbent, and recycling after use.

A stir bar sorptive extraction device coupled with a gas chromatography flame ionization detector for the determination of abused prescription drugs in lean cocktail samples.

A lean cocktail is a mixed drink for the non-medical use of prescription medications that has emerged in recent years as a drug of abuse and is related to drug-facilitated crimes. The determination of active ingredients in a lean cocktail is necessary for forensic investigations. This work presents an in-house developed stir bar sorptive extraction (SBSE) device with an XAD-2 adsorbent followed by analysis using GC-FID for the extraction and determination of the five main abused prescription drugs (diphenhydramine, tramadol, chlorpheniramine, dextromethorphan and promethazine) in lean cocktail samples. Under optimized conditions, the developed method provided linearity for 1.0-250 µg mL-1 of each of the five abused prescription drugs. The limits of detection and limits of quantitation were in the respective ranges of 0.25-0.5 µg mL-1 and 1.0-1.5 µg mL-1. The percentage of extraction was 85.0-94.9%. The intra-day and inter-day precisions were 1.2-14.4% RSD and 1.4-15.8% RSD, respectively. Good relative recoveries in the range of 86.7-110.3% and 88.5-107.9% were obtained when the proposed method was applied for extraction and analysis of abused prescription drugs in five lean cocktail samples. The developed method can be a useful tool for measuring the levels of abused prescription drugs in a lean cocktail and the data could also be used as evidence in a forensic investigation.

Fluorescent cysteine probe based on a signal amplification unit, a catalyzed hairpin assembly reaction and Förster resonance energy transfer.

This work developed a sensitive DNA-based fluorescent probe comprising a cysteine binding unit and a signal amplification unit based on a catalyzed hairpin assembly (CHA) reaction. The cysteine binding unit comprises a homodimer of single-stranded DNA (ssDNA) rich in cytosine and held together by silver ions. In the presence of cysteine, the homodimer is disintegrated because of cysteine-silver binding that liberates the ssDNA, which drives the CHA reaction in the signal amplification unit. Förster resonance energy transfer (FRET) was used to report the generation of the amplified double-stranded DNA (dsDNA) product. Under the optimal conditions, the probe provided a good linearity (100-1200 nM), a good detection limit (47.8 ± 2.7 nM) and quantification limit (159.3 ± 5.3 nM), and a good sensitivity (1.900 ± 0.045µM-1). The probe was then used to detect cysteine in nine real food supplement samples. All results provided good recoveries that are acceptable by the AOAC, indicating that it has potential for practical applications.

A simple gelatin aerogel tablet sorbent for the effective vortex assisted solid phase extraction of polycyclic aromatic hydrocarbons from tea samples.

A gelatin aerogel tablet was used as a vortex assisted solid phase extraction (VA-SPE) sorbent for the determination of polycyclic aromatic hydrocarbons (PAHs), benzo(a)anthracene (BaA), benzo(b)fluoranthene (BbF), and benzo(a)pyrene (BaP) in tea samples. They have been quantified by a high-performance liquid chromatography with a diode array detector (HPLC-DAD). The method shows good linearity (R2 = 0.999) at concentrations of 5.00-200 ng L-1, with the limits of detection of 1.65 ± 0.02, 1.81 ± 0.02, and 2.06 ± 0.03 ng L-1 for BaA, BbF, and BaP, respectively. Good reproducibility (RSDs < 0.24%, n = 6), good precision (RSDs < 6.3%), and excellent reusability (n = 40, RSDs < 0.17%) were achieved. The tablet can extract PAHs within 1.5 min with good recoveries (70.10 ± 0.74% - 119.3 ± 4.1%). This method, which is simple, rapid, ecofriendly, and inexpensive, requires low consumption of organic solvent, and has potential application in food safety.

A copper nanoclusters probe for dual detection of microalbumin and creatinine.

A fluorescent probe based on glutathione-capped copper nanoclusters (GSH-CuNCs) was developed for the detection of dual targets, human serum albumin (HSA) and creatinine, in human urine. The GSH-CuNCs were synthesized by a one-pot green method using ascorbic acid as a reducing agent. The detection of HSA was in a turn-on mode via electrostatic interaction in a basic condition while the detection of creatinine was in a turn-off mode via non-covalent bonding in an acidic condition. Under optimal conditions, the linear range and detection limit of HSA were 5.0 nM to 150 nM and 1.510 ±â€¯0.041 nM, while those of creatinine were 30 µM to 1000 µM and 13.0 ±â€¯1.0 µM. This easily fabricated nanocluster probe provided a fast response with high sensitivity, and good selectivity. Recoveries from urine samples were in the range of 81.44 ±â€¯0.25 to 109.22 ±â€¯0.57% for HSA and 80.57 ±â€¯0.16 to 109.0 ±â€¯0.10% for creatinine. The urinary analytical results from the fluorescent probe were in good agreement (P > 0.05) to those obtained from immunoturbidimetric and enzymatic methods, signifying the excellent performance of this sensing system.

Magnetic microsphere sorbent on CaCO3 templates: Simple synthesis and efficient extraction of trace carbamate pesticides in fresh produce.

Polypyrrole magnetic microspheres were synthesized and used to extract carbaryl, carbofuran, and methomyl before analysis by a high-performance liquid chromatography with diode array detection. Under optimal conditions, four times the preconcentration was achieved with the use of only 1.2 mL of sample. Good linearity with ranges of 3.0-7.5 × 103, 6.0-4.5 × 103, and 15-3.0 × 103 ng kg-1 and limits of detection of 1.37 ± 0.10, 4.7 ± 1.2, and 10.1 ± 5.7 ng kg-1 were obtained, respectively. Good reproducibility (RSDs < 5%) was achieved over 24 cycles of extraction and regeneration. Good accuracy (recoveries 81.6 ± 1.5%-108.3 ± 2.2%) and good precision (RSDs 0.11%-4.5%) were obtained. Carbaryl was detected in apple (2.75 ± 0.23 ng kg-1), carbofuran in tomato (11.34 ± 0.61 ng kg-1), and methomyl in watermelon (34.7 ± 1.7 ng kg-1). The relative expanded uncertainty of the measurement method was less than 14% for all three pesticides.

A miniature stainless steel net dumbbell-shaped stir-bar for the extraction of phthalate esters in instant noodle and rice soup samples.

This work reports the development of a very-simple-to-construct stir-bar extraction device so called "a dumbbell-shaped stainless steel stir-bar." The extraction device was assembled from a rolled up stainless steel net filled with an XAD-2 sorbent and a metal rod to allow the use of a magnetic stirrer during extraction. The dumbbell-shaped stainless steel stir-bar was used to extract diethyl phthalate (DEP), dibutyl phthalate (DBP), and di(2-ethylhexyl) phthalate (DEHP) before analysis by a gas chromatograph equipped with an electron capture detector (GD-ECD). Under the optimal conditions, the developed method provided a good linearity from 10.0 to 1,000.0 ng mL-1 for all three compounds. Limits of detection and limits of quantification were 9.37 ± 0.29 ng mL-1 and 31.22 ± 0.95 ng mL-1 for DEP, 5.73 ± 0.31 ng mL-1 and 19.1 ± 1.0 ng mL-1 for DBP and 3.30 ± 0.06 ng mL-1 and 11.0 ± 0.19 ng mL-1 for DEHP, respectively. Good recoveries in the range of 81.89 ± 0.17 to 109.5 ± 2.0% were achieved when the method was used to extract phthalate esters in five instant noodle and two rice soup samples.

A novel 3D-printed solid phase microextraction device equipped with silver-polyaniline coated pencil lead for the extraction of phthalate esters in cosmeceutical products.

A screw-based portable and simple solid phase microextraction device was fabricated by a 3D printer and used in combination with the developed silver-incorporated porous polyaniline film pencil lead solid-phase microextraction fiber (Ag/PANI SPME). Scanning electron microscopy revealed a porous structure of the electrodeposited Ag/PANI film. The spectrum from energy dispersive x-ray spectroscopy (EDS) and the elemental map confirmed the presence of silver in the porous polymer film. It was used under stirring for the extraction of five phthalate esters: dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), benzyl butyl phthalate (BBP) and di-2-ethylhexyl phthalate (DEHP). The extracted solution was identified and quantified by gas chromatography using a flame ionization detector (GC-FID). Under the optimum conditions of the developed method, a good linearity was obtained in a concentration range of 5.0-1000 µg L-1 for all five phthalate esters with limits of detection (LODs) of 4.41 ±â€¯0.91 µg L-1, 3.98 ±â€¯0.92 µg L-1, 3.65 ±â€¯0.74 µg L-1, 4.91 ±â€¯0.52 µg L-1 and 4.25 ±â€¯0.66 µg L-1 for DMP, DEP, DBP, BBP and DEHP, respectively. The developed method provided good precision when tested with standard solutions (RSD < 5.5%, n = 6) and real samples (RSD < 3.4%, n = 6). Good fiber-to-fiber reproducibility was also confirmed by extraction with six newly prepared fibers; recoveries ranged from 81.09 ±â€¯0.54% to 92.92 ±â€¯0.46% with RSD <6.6%. The developed method was used to determine phthalate esters in 14 cosmeceutical samples. In rubbing alcohol samples, DEP and DEHP were detected at 7.03 ±â€¯0.76 µg L-1 and 5.89 ±â€¯0.53 µg L-1, respectively, while in contact lens cleaners, DEHP was found in a concentration range from 5.3 ±â€¯1.1 µg L-1 to 6.8 ±â€¯1.2 µg L-1. No phthalate esters contamination was detectable in saline solutions, eye cleaners and antibacterial disinfectant liquids. Recoveries in the range of 81.92 ±â€¯0.99% to 102.4 ±â€¯1.1% indicated the good accuracy of the developed method.

A miniaturized monolith-MWCNTs-COOH multi-stir-rod microextractor device for trace parabens determination in cosmetic and personal care products.

A portable and simple microextractor device was constructed by aligning six miniaturized multi-stir-rod microextractors. Each microextractor was prepared from rod-like multiwalled carbon nanotubes functionalized with a carboxylic group (MWCNTs-COOH) in composite monoliths that were bundled together and connected to a small DC motor. Using six of these microextractors, the device could extract six samples at the same time. A scanning electron microscope (SEM) showed the MWCNTs-COOH well distributed throughout the highly porous structure of the monolith-MWCNTs-COOH-stir-rod. This miniaturized multi-stir-rod microextractor device was used for the extraction of four parabens, methylparaben (MP), ethylparaben (EP), propylparaben (PP) and butylparaben (BP). Under optimized conditions, good linearities were obtained in the concentration range of 1.0 ng mL-1 to 1.0 µg mL-1 for MP and EP and 2.0 ng mL-1 to 1.0 µg mL-1 for PP and BP. The limits of detection were low, 636.2 ±â€¯7.6 pg mL-1 for MP, 675.5 ±â€¯6.0 pg mL-1 for EP, 676.6 ±â€¯8.6 pg mL-1 for PP and 803.4 ±â€¯9.6 pg mL-1 for BP. The developed microextractor could be used up to 15 times (%RSDs from 1.5 to 5.2) and also provided good preparation reproducibility (%RSD from 1.3 to 5.8, n = 6). The % RSDs of intra-day (n = 6) and inter-day (n = 6) precisions were obtained from 1.10-7.79 and 1.96-7.55, respectively. This developed device coupled with high performance liquid chromatography-diode array detector (HPLC-DAD) was applied for the extraction and preconcentration of four parabens in personal care products and cosmetics. The recoveries were studied by spiking the standard solution of parabens in real samples. Good recoveries were obtained in the range of 89.0 ±â€¯2.7 to 102.7 ±â€¯1.8% for MP, 88.09 ±â€¯6.4 to 102.5 ±â€¯1.0% for EP, 83.4 ±â€¯6.4 to 102.9 ±â€¯1.5% for PP and 83.5 ±â€¯3.6 to 102.3 ±â€¯2.0% for BP. This developed device might be easily applied for the extraction and preconcentration of other trace organic compounds in sample matrices.

A stir foam composed of graphene oxide, poly(ethylene glycol) and natural latex for the extraction of preservatives and antioxidant.

A stir foam composed of graphene oxide, poly(ethylene glycol) and natural latex (GO-PEG-NL) was prepared for use in micro-solid phase extraction sorbent of preservative agents and antioxidants from cosmetic products. The extracted analytes were quantified by GC-MS. Under the optimized conditions, the calibration plots are linear in the concentration ranges between 5.0 µg·L-1 to 1.0 mg·L-1 for benzoic acid, of 10.0 µg·L-1 to 1.0 mg·L-1 for 2-methyl-3-isothiazolinone (MI), and between 1.0 µg·L-1 and 1.0 mg·L-1 for both 3-tert-butyl-4-hydroxyanisole (BHA) and 2,6-di-tert-butyl-p-hydroxytoluene (BHT). The LODs are 1.0 µg·L-1 for benzoic acid, 5.0 µg·L-1 for MI and 0.5 µg·L-1 for both BHA and BHT. The stir-foam can be easily prepared, is inexpensive and well reproducible (RSDs <3%, for n = 6). It can be re-used for up to 12 times after which extraction efficiency has dropped to 90%. The method was successfully applied to the determination of preservatives and antioxidants in cosmetic samples. Recoveries from spiked samples ranged between 94.5 ± 2.1% and 99.8 ± 1.8%. Graphical abstract A stir foam was prepared from graphene oxide, poly(ethylene glycol) and natural latex (GO-PEG-NL) and is shown to be a most viable sorbent for the microextraction of trace amounts of preservative agents and antioxidants from cosmetic products.

A polypyrrole-chitosan cryogel stir-bead micro-solid phase extractor for the determination of phthalate esters in contact lenses storage solutions and in artificial saliva in contact with baby teethers.

Phthalate esters (PAEs), especially dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), di-2-ethylhexyl phthalate (DEHP) are widely used as plasticizers in plastics and polymers. They are not chemically bound and can easily migrate into food and human tissue that comes into contact with these materials. The method developed in this work was applied for the preconcentration and determination of these four phthalate esters that might leach from contact lenses and baby teethers. A novel stir-bead micro-solid phase extractor of chitosan cryogel composited with polypyrrole with a steel wire core was evaluated for the extraction of DMP, DEP, DBP and DEHP before analysis by high performance liquid chromatography (HPLC). Scanning electron micrographs of the polypyrrole-chitosan cryogel beads revealed a high porosity with large surface area. Under the optimum conditions, the developed method provided a good linearity in a concentration range from 10 to 750 ng mL-1 for DMP and from 5.0 to 750 ng mL-1 for DEP, DBP and DEHP. The limits of detection (LOD) were 6.07 ± 0.22 ng mL-1, 4.358 ± 0.097 ng mL-1, 4.408 ± 0.099 ng mL-1 and 3.916 ± 0.053 ng mL-1 for DMP, DEP, DBP and DEHP, respectively, and the method reproducibility was good (n = 6, % RSD < 6.0). DBP and DEHP were detected in two original storage solutions of contact lenses from 13.2 ± 1.1 ng mL-1 to 15.4 ± 1.9 ng mL-1 and from 21.3 ± 1.6 ng mL-1 to 23.5 ± 1.5 ng mL-1, respectively. In the artificial saliva in contact with baby teether samples only DEHP was found, from 4.91 ± 0.31 ng mL-1 to 6.78 ± 0.23 ng mL-1, with good recoveries ranging from 81.3 ± 8.4% to 106.3 ± 5.2%.

A scanner-based colorimetric mercuric ion detection using Tween-20-stabilized AuNPs solution in 96-well plates.

This paper reports the development of a sensitive, high-throughput colorimetric method for the detection of trace mercuric ions (Hg2+). The method is based on the binding of the analyte to gold nanoparticles (AuNPs) modified with Tween-20. Tween-20 was used as a nonionic stabilizer to allow a good dispersion of AuNPs in solution. When mercuric ions were added to the solution, they replaced the Tween-20 stabilizer on the surface of the AuNPs due to their stronger binding affinity. This caused the NPs to aggregate and the color of the solution to change from red to blue. The quantitative analysis of Hg2+ was achieved by plotting the Red Green Blue (RGB) values of the scanned images of the analyte samples in the AuNP solution against concentrations of Hg2+. Since the reaction was carried out in 96-well plates, ninety-six samples were analyzed simultaneously, reducing the cost and time of analysis. The experimental parameters optimized were the concentrations of Tween-20 and NaCl, the reactants ratio, and the incubation time. Under the optimum conditions, the calibration plot of the assay was linear over an Hg2+ concentration range of 0.10-2.00 mg L-1, and the detection limit was 0.050 mg L-1 (S/N  =  3). The selectivity of the technique was high with no significant colorimetric responses to the presence of 100-fold excesses of other metal ions. Quantification was validated with Hg2+ standard solutions and spiked tap and waste water samples, and the accuracy of the technique was confirmed. The developed technique is simple and cost effective because it requires no complicated instruments, yet the results demonstrate it to be a very powerful technique with the potential to be developed for on-site mercury detection.

A preconcentrator-separator two-in-one online system for polycyclic aromatic hydrocarbons analysis.

A novel preconcentrator-separator two-in-one online system has been developed for the online analysis of trace amounts of four polycyclic aromatic hydrocarbons (PAHs) in tea samples. A micro-preconcentrator unit of zeolite imidazolate framework-8-poly(vinyl alcohol) cryogel (ZIF-8-PVA cryogel) and a micro-separation unit of multiwalled carbon nanotubes-poly(vinyl alcohol) cryogel (MWCNTs-PVA cryogel) were fabricated onto an acrylic plate. The eluent from this two-in-one system flowed directly to an on-column UV-visible detector. Under optimum conditions, the system provided a wide linear range from 0.10µgL-1 to 2.00mgL-1 for benzo(a)anthracene (BaA) and chrysene (Chry), 0.15µgL-1 to 3.00mgL-1 for benzo(a)pyrene (BaP) and 0.20µgL-1 to 5.00mgL-1 for benzo(b)fluoranthene (BbF). The limits of detection were 0.05µgL-1 of both BaA and Chry, 0.10µgL-1 of BaP and 0.20µgL-1 of BbF. This two-in-one system was cost-effective, easy to prepare, had excellent stability for up to 417 consecutive injection cycles and provided a good system-to-system reproducibility (n=6) with a relative standard deviation of less than 4%. The system was successfully applied to detect PAHs in tea samples. The concentrations of BaA, Chry, BaP and BbF in seven tea samples were found in the range of non-detectable 2.73±0.07mgL-1 with good recoveries of 83±6 to 108±4%. In addition, it can be easily applied for the detection of other aromatic compounds in contaminated water samples.