Showing papers in "Analytical Sciences in 2018"
TL;DR: A paper-based 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl (DPPH) assay for a simple, inexpensive, low reagent and sample consumption and high throughput analysis of antioxidant activity, indicating that the developed method was reliable for antioxidant activity analysis of real samples.
Abstract: We report on a paper-based 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl (DPPH) assay for a simple, inexpensive, low reagent and sample consumption and high throughput analysis of antioxidant activity. The paper-based device was fabricated using a lamination method to create a 5-mm in diameter circular test zone that was embedded with a DPPH reagent. The analysis was carried out in one-step by dropping an antioxidant/sample onto the test zone. After reduction by the antioxidant, the DPPH radicals become stable DPPH molecules, resulting in a change in color from deep violet to pale yellow. The violet color intensity of DPPH was inversely proportional to the antioxidant activity of the samples, and was measured using imaging software. A high precision and a low limit of detection were found in the analysis of six standard antioxidants including gallic acid, trolox, ascorbic acid, caffeic acid, vanilliic acid and quercetin. The device was then validated against the traditional spectrophotometric DPPH assay by analyzing the antioxidant activity of 7 tea samples. The results showed no significant difference for gallic acid equivalent for all 7 samples obtained from the two methods at the 95% confidence level, indicating that the developed method was reliable for antioxidant activity analysis of real samples. Finally, the paper-based DPPH device was found to be stable over 10 days when stored in a refrigerator (2 - 4°C), making it an easy-to-use device for end-users.
87 citations
TL;DR: This review highlights the effect of adopting different sensor designs, distinct fabrication techniques, as well as different modification methods, in order to produce reliable and reproducible reading in electrochemical bio-sensing using paper-based detection systems.
Abstract: Electrochemical bio-sensing using paper-based detection systems is the main focus of this review. The different existing designs of 2-dimensional and 3-dimensional sensors, and fabrication techniques are discussed. This review highlights the effect of adopting different sensor designs, distinct fabrication techniques, as well as different modification methods, in order to produce reliable and reproducible reading. The use of various nanomaterials have been demonstrated in order to modify the surface of electrodes during fabrication to further enhance the signal for subsequent analysis. The reviewed sensors were classified into categories based on their applications, such as diagnostics, environmental and food testing. One of the major advantages of using paper-based electrochemical sensors is the potential for miniaturization, which only requires relatively small amount of samples, and the low cost for the purpose of mass production. Additionally, most of the devices reviewed were made to be portable, making them well-suited for on-site detection. Finally, paper-based detection is an ideal platform to fabricate cost-effective, user-friendly and sensitive electrochemical biosensors, with large capacity for customization depending on functional needs.
69 citations
TL;DR: This study shows that the Graphene/AuNPs-based sensor can detect Cr(VI) with a low detection limit, a wide dynamic range of 0 to 20 μM and very good selectivity and reproducibility.
Abstract: In this study, nanocomposites of ligand-free gold nanoparticles that are anchored onto the graphene surface (Graphene/AuNPs) were synthesized by a sonochemical method in a single reaction step A highly sensitive amperometric sensor using Graphene/AuNPs is proposed for the determination of trace hexavalent chromium Cr(VI) in environmental water samples Compared with a gold electrode, a glassy carbon electrode and a AuNPs modified glassy carbon electrode, the Graphene/AuNPs modified glassy carbon electrode exhibits the highest electrocatalytic activity and stability towards the reduction of Cr(VI), based on the results by cyclic voltammetry and electrochemical AC impedance studies This study shows that the Graphene/AuNPs-based sensor can detect Cr(VI) with a low detection limit of 10 nM (∼05 μg/L), a wide dynamic range of 0 to 20 μM (R = 0999) and very good selectivity and reproducibility The electrode is applied to the determination of Cr(VI) in river samples with satisfactory recovery values
42 citations
TL;DR: Electrochemical paper-based analytical devices drawn with graphite pencil for the determination of ascorbic acid (AA) in commercial tablets are described and the accuracy of the proposed devices was investigated through recovery experiments in three concentration levels.
Abstract: This study describes the use of electrochemical paper-based analytical devices (ePADs) drawn with graphite pencil for the determination of ascorbic acid (AA) in commercial tablets. ePADs were fabricated using vegetal paper and graphite pencil. First, the three-electrode electrochemical cell drawn using a graphical software and toner lines were laser printed on the vegetal paper surface to delimit the electrode areas. Then, the electrode regions were manually painted with graphite pencil. Afterwards, the pseudo-reference electrode was defined with the deposition of silver ink over the graphite surface. Cyclic voltammetry and square wave voltammetry (SWV) experiments were performed to optimize the electroanalytical parameters as well as to quantitatively determine the AA concentration in two commercial tables. ePADs exhibited linear behavior for a concentration range between 0.5 and 3.0 mmol L-1. The achieved limit of detection and sensitivity were 70 μmol L-1 and 0.47 μA/mmol L-1, respectively. The AA concentration levels found by SWV experiments in both CenevitTM and Energil CTM were 2.80 ± 0.02 and 3.10 ± 0.01 mmol L-1, respectively. The accuracy of the proposed devices was investigated through recovery experiments in three concentration levels and it presented values between 95 and 115%.
34 citations
TL;DR: Simple, low-cost and portable microfluidic paper-based analytical devices (μPADs) for determination of creatinine in urine samples were developed based on Jaffé reaction between the Creatinine and picric acid in alkaline conditions, generating a colorimetric creatinines-alkaline picrate complex.
Abstract: Simple, low-cost and portable microfluidic paper-based analytical devices (μPADs) for determination of creatinine in urine samples were developed. The methodology was based on Jaffe reaction between the creatinine and picric acid in alkaline conditions, generating a colorimetric creatinine-alkaline picrate complex. The product exhibits an orange color that is clearly visible on the μPADs. The color intensity of the complex, which is indicative of the concentration of creatinine, is then quantitatively determined using ImageJ software. Various experimental parameters were optimized to achieve the best performance of the μPADs. Under the optimum conditions, a wide linear range was obtained in the range of 0.2 - 1 mM with a limit of detection and limit of quantitation of 0.08 and 0.26 mM, respectively. The accuracy of the proposed method was in good agreement with the standard Jaffe method. Finally, the developed devices were successfully applied for the determination of creatinine in urine samples.
34 citations
TL;DR: A smartphone application, called CAnal, was developed as a colorimetric analyzer in paper-based devices for sensitive and selective determination of mercury(II) in water samples and demonstrated to have acceptable performance that was in agreement with the data from cold vapor atomic absorption spectrophotometry (CV-AAS), a conventional method.
Abstract: A smartphone application, called CAnal, was developed as a colorimetric analyzer in paper-based devices for sensitive and selective determination of mercury(II) in water samples. Measurement on the double layer of a microfluidic paper-based analytical device (μPAD) fabricated by alkyl ketene dimer (AKD)-inkjet printing technique with special design doped with unmodified silver nanoparticles (AgNPs) onto the detection zones was performed by monitoring the gray intensity in the blue channel of AgNPs, which disintegrated when exposed to mercury(II) on μPAD. Under the optimized conditions, the developed approach showed high sensitivity, low limit of detection (0.003 mg L-1, 3SD blank/slope of the calibration curve), small sample volume uptake (two times of 2 μL), and short analysis time. The linearity range of this technique ranged from 0.01 to 10 mg L-1 (r2 = 0.993). Furthermore, practical analysis of various water samples was also demonstrated to have acceptable performance that was in agreement with the data from cold vapor atomic absorption spectrophotometry (CV-AAS), a conventional method. The proposed technique allows for a rapid, simple (instant report of the final mercury(II) concentration in water samples via smartphone display), sensitive, selective, and on-site analysis with high sample throughput (48 samples h-1, n = 3) of trace mercury(II) in water samples, which is suitable for end users who are unskilled in analyzing mercury(II) in water samples.
33 citations
TL;DR: In this review, recent studies of the microfluidic vascular models are introduced and basic phenomena and functions were realized in vascular models, including fluid shear stress, cell strain, interstitial flow, endothelial permeation, angiogenesis, and thrombosis.
Abstract: The blood vessel is part of the circulatory system, and systemic circulation provides the blood supply to all tissues. Arteries are pathways through which the blood is carried, and the capillaries have a key role in material exchange to maintain the tissue environment. Blood vessels have structures appropriate for their functions, and their sizes and cell types are different. In this review, we introduced recent studies of the microfluidic vascular models. The model structures are classified mainly as poly(dimethylsiloxane) and hydrogel microchannels and self-assembled networks. Basic phenomena and functions were realized in vascular models, including fluid shear stress, cell strain, interstitial flow, endothelial permeation, angiogenesis, and thrombosis. In some models, endothelial cells were co-cultured with smooth muscle cells, pericytes, and fibroblasts in an extracellular matrix. Examples of vascular models involving the brain, lung, liver, kidney, placenta, and cancer were also introduced.
27 citations
TL;DR: The branched-chain SCFAs levels in feces from model mice of spontaneous obese type II diabetes were on a declining trend compared with normal, and the BA levels showed that normal mice were increasing, and model mice had decreased tendency for breeding months.
Abstract: We present a sensitive and selective method for the simultaneous determination of short-chain fatty acids (SCFAs), such as acetic acid (AA), propionic acid, butyric acid (BA), isobutyric acid, valeric acid, isovaleric acid, hydroangelic acid, caproic acid, 4-methylvaleric acid and succinic acid (SA) in feces samples using a ultra-high performance liquid-chromatography tandem mass spectrometry (UHPLC-MS/MS) with simple derivatization of 2-picolylamine. The main SFCAs were derivatized in the same condition, and showed the specific product ion (m/z 109) in the electrospray positive mode regarding to 2-picolylamine. The derivatized SA showed a different pattern of the product ion (m/z 191). The derivatized analytes showed LOD 0.991. The QuEChERS was used for sample preparation of feces samples. In the recovery test, the recovery values appeared from 89.7 to 100.2% (RSD: 2.1 to 9.2%, n = 6). This developed method was applied to evaluate obese diabetes model mice. In the result, the branched-chain SCFAs levels in feces from model mice of spontaneous obese type II diabetes were on a declining trend compared with normal. The AA levels from model mice with high-calorie/fat diet are owed a declining trend for 3 to 9 months. The BA levels showed that normal mice were increasing, and model mice had decreased tendency for breeding months. High-calorie/fat diet showed that the SA levels increased.
26 citations
TL;DR: It is demonstrated that a cost-efficient, easy to prepare, hybrid SERS substrate-gold nanoparticles (AuNPs) on untreated Al foil (AlF) can effectively detect pharmaceuticals, such as paracetamol and clinical biomarkers, like urea in artificial urine.
Abstract: We demonstrated that a cost-efficient, easy to prepare, hybrid SERS substrate-gold nanoparticles (AuNPs) on untreated Al foil (AlF) can effectively detect pharmaceuticals, such as paracetamol and clinical biomarkers, like urea in artificial urine The limit of detection (LOD) for paracetamol on AuNPs on AlF is superior (01 vs 1 mM ) to the LOD reported for SERS detection of paracetamol in the literature For SERS detection of urea in urine, AuNPs on both Al foil and Au film performed much better than AuNPs on glass, in terms of the concentration range, linearity and LOD However, assay on AuNPs on AlF showed a better semi-logarithmic trendline with R2 = 098 than an assay on AuNPs on Au film with R2 = 094 They have comparable sensitivity with LOD 0024 and 0017 M, respectively The limit of quantification (LOQ) of the former is 0026 M, which makes it sufficient for the quantification of urea in urine at both normal and pathophysiological (003 - 015 M) concentration
26 citations
TL;DR: The results demonstrated that the developed paper device is an alternative to allow for fast, simple, instrument-free, cheap, portable and high-throughput screening of antioxidant activity analysis in real samples.
Abstract: This work reports a portable distance-based detection paper device that has a thermometer-like shape for rapid, instrument-free determination of antioxidant activity using a nanoceria assay. The assay is based on partial reduction of cerium ion from Ce4+ to Ce3+ on nanoceria deposited along the detection channel by antioxidants present in food, giving highly reactive oxidation products. Either these products or the parent antioxidant compounds could then bind to the OH-rich ceria nanoparticles and generate charge transfer ceria-antioxidant complexes resulting in a yellow to brown color change. The distance of the brown color on the detection channel is directly proportional to antioxidant activity, and can be easily measured using an integrated ruler without the need of any external sophisticated instrument for detection. The paper sensor has been studied for the analysis of common antioxidants and its performance was validated against traditional antioxidant assays for 11 tea sample analyses. Using the Spearman rank correlation coefficient method, the antioxidant activity of tea samples obtained from the paper device correlated with the traditional assay at the 95% confidence level. The developed sensor provided a high recovery and tolerance limit and was stable for 50 days both when stored at ambient and low temperature (6 and -20°C). The results demonstrated that the developed paper device is an alternative to allow for fast, simple, instrument-free, cheap, portable and high-throughput screening of antioxidant activity analysis in real samples.
24 citations
TL;DR: The anodized porous gold electrodes demonstrate promise as scaffolds for direct electron transfer (DET)-type bioelectrocatalysis and exhibit well-defined sigmoidal steady-state waves corresponding to DET-type bio electrodynamics.
Abstract: In this study, nanostructured porous gold electrodes were prepared by the anodization of gold in the presence of oxalic acid or glucose as a reductant, and applied as scaffolds for direct electron transfer (DET)-type bioelectrocatalysis. Gold cations generated in the anodization seem to be reduced by the reductant to construct a porous gold structure. The DET-type performance of the electrode was examined using two DET-type model enzymes, bilirubin oxidase (BOD) and peroxidase (POD), for the four-electron reduction of dioxygen and the two-electron reduction of peroxide, respectively. BOD and POD on the anodized porous gold electrodes exhibited well-defined sigmoidal steady-state waves corresponding to DET-type bioelectrocatalysis. Scanning electron microscopy images revealed sponge-like pores on the electrodes. The anodized porous gold electrodes demonstrate promise as scaffolds for DET-type bioelectrocatalysis.
TL;DR: A simple and inexpensive microfluidic paper-based analytical device (μPAD) for the determination of hexavalent chromium (CrVI) in water samples and the green intensity analysis was the best sensitive among the RGB color.
Abstract: This article describes a simple and inexpensive microfluidic paper-based analytical device (μPAD) for the determination of hexavalent chromium (CrVI) in water samples. The μPADs were fabricated on paper by photolithography using a photomask printed with a 3D printer and functionalized with reagents for a colorimetric assay. In the μPAD, CrVI reacts with 1,5-diphenylcarbazide to form a violet-colored complex. Images of μPADs were captured with a digital camera; then the red, green, and blue color intensity of each detection zone were measured using images processing software. The green intensity analysis was the best sensitive among the RGB color. A linear working range (40 - 400 ppm; R2 = 0.981) between the CrVI and green intensity was obtained with a detection limit of 30 ppm. All of the recoveries were between 94 and 109% in recovery studies on water samples, and good results were obtained.
TL;DR: The probe's fluorescence was turn-off after adding N2H4, which could be observed under UV light at 365 nm, which indicates that probe 1 could be used as a visual sensor for hydrazine.
Abstract: A fluorescent probe, 7-(diethylamino)-2-oxo-2H-chromene-4-carbaldehyde (probe 1), was designed and synthesized for the sensitive detection of hydrazine. The addition of N2H4 caused the fluorescence intensity of probe 1 to decrease. The probe's fluorescence was turn-off after adding N2H4, which could be observed under UV light at 365 nm. Moreover, once treated with different concentrations N2H4 solutions, the solution color change could be distinguished, which indicates that probe 1 could be used as a visual sensor for hydrazine. Moreover, probe 1 can be used as a signal tool to determine hydrazine levels in solutions, such as red wine and water.
TL;DR: The review results suggest that the stable isotope compositions of the biometals can be used as effective markers for diagnostics of various kinds of diseases related to metabolic disorders.
Abstract: Stable isotope composition varies due to different reactivity or mobility among the isotopes. Various pioneering studies revealed that isotope fractionation is common for many elements, and it is now widely recognized that the stable isotope compositions of biometals can be used as new tracers for element metabolism. In this review, we summarize the recently published isotope compositions of iron (Fe), copper (Cu), zinc (Zn), and calcium (Ca) in various biological samples, including tissues from plants, animals, and humans. Discussions were carried out with respect to age, sex, organ, and the presence or absence of particular diseases for animals and humans. For Fe and Cu isotopes, changes in oxidation states generate large isotopic fractionation through the metabolism of those elements. Isotope composition of Zn greatly fractionates among tissues even without changes in oxidation state. Isotopic composition of Ca is a powerful tracer for the metabolism of Ca in bones. The review results suggest that the stable isotope compositions of the biometals can be used as effective markers for diagnostics of various kinds of diseases related to metabolic disorders.
TL;DR: The proposed probe Cu-P, a new and simple fluorescent probe for detecting copper ion (Cu2+) was designed and synthesized and showed high sensitivity and selectivity toward Cu2+.
Abstract: The fluorescent probe has become an important method for the detection of heavy metal ions. In the present work, a new and simple fluorescent probe, Cu-P, for detecting copper ion (Cu2+) was designed and synthesized. The probe has shown high sensitivity and selectivity toward Cu2+. The detection limit was 13 nM (based on the 3σ/slope). A significant color change from yellow to pink was observed; thus, the probe Cu-P could serve as a "naked-eye" indicator for Cu2+. Furthermore, the proposed probe was used to detect Cu2+ in real water and soil extract samples, with the result being satisfactory. Therefore, our proposed probe would provide a promising method for the detection of Cu2+ in the environment.
TL;DR: A novel multilayer film based on poly-L-cysteine, graphene quantum dots (GQDs), and gold nanoparticles (GNPs) was exploited to develop a highly sensitive electrochemical sensor for the detection of L-Pro.
Abstract: An innovative electrochemical interface for quantitation of L-proline (L-Pro) based on ternary amplification strategy was fabricated. In this work, gold nanoparticles prepared by soft template methodology were immobilized onto green and biocompatible nanocomposite containing poly as a conductive matrix and graphene quantum dots as the amplification element. Therefore, a novel multilayer film based on poly-L-cysteine, graphene quantum dots (GQDs), and gold nanoparticles (GNPs) was exploited to develop a highly sensitive electrochemical sensor for the detection of L-Pro. Fully electrochemical methodology was used to prepare a new transducer on a glassy carbon electrode, which provided a high surface area towards sensitive detection of L-Pro. The prepared electrode was employed for the detection of L-Pro. Under optimized conditions, the calibration curve for L-Pro concentration was linear in 0.5 nM - 10 mM with a low limit of quantification of 0.1 nM. The practical analytical utility of the modified electrode was illustrated by determination of L-Pro in unprocessed human plasma samples.
TL;DR: This on-line SFE-SFC method is powerful to simplify the pre-processing and quantitative analysis of natural products.
Abstract: In this study, an on-line supercritical fluid extraction (SFE) and supercritical fluid chromatography (SFC) method was developed for the rapid determination of oleanoic acid and ursolic acid in Chaenomelis Fructus. After optimization of the conditions, the two triterpenoid acids was obtained by SFE using 20% methanol as a modifier at 35°C in 8 min. They were resolved on a Shim-pack UC-X Diol column (4.6 × 150 mm, 3 μm) in 14 min (0 - 10 min, 5 - 10%; 10 - 14 min, 10% methanol in CO2) with a backpressure of 15 MPa at 40°C. The on-line SFE-SFC method could be completed within 40 min (10.79 mg/g dry plant, Rs = 2.36), while the ultrasound-assisted extraction and HPLC method required at least 90 min (3.55 mg/g dry plant, Rs = 1.92). This on-line SFE-SFC method is powerful to simplify the pre-processing and quantitative analysis of natural products.
TL;DR: It is shown that probe 1 can be successfully applied to detect N2H4 concentrations in real water samples and offers a certain practical significance for use as a visible detection agent to detect H4 efficiently by distinct color response.
Abstract: A new highly selective and visible colorimetric fluorescent probe (probe 1) was developed to detect hydrazine (N2H4) concentration in real water samples. As different concentrations of N2H4 were added, the color of the probe solution was graded gradually from colorless to pink, which could be observed by the naked eye under UV light at 365 nm. Our research indicates that probe 1 offers a certain practical significance for use as a visible detection agent to detect N2H4 efficiently by distinct color response. Furthermore, our work showed that probe 1 can be successfully applied to detect N2H4 concentrations in real water samples.
TL;DR: The application of QDs to regenerative medicine, especially stem cell transplantation therapy, is reviewed and the in vivo imaging of transplanted stem cells in mice by QDs emitting fluorescence in the near-infrared region is described.
Abstract: Quantum dots (QDs) have excellent fluorescence properties in comparison to traditional fluorescence probes. Thus, the optical application of QDs is rapidly expanding to each field of analytical chemistry. In this review paper, we reviewed the application of QDs to regenerative medicine, especially stem cell transplantation therapy. The labeling of stem cells using QDs composed of semiconductor materials in combination with a chemical substance, poly-cationic liposome and cell penetrating peptide is reported. In addition, the influence of QD labeling on the pluripotency of stem cells is also reported. Finally, the in vivo imaging of transplanted stem cells in mice by QDs emitting fluorescence in the near-infrared region, which can be detected by in vivo fluorescence imaging systems such as IVIS and SAI-1000, is described. The future prospects for stem cell imaging technology by QDs are also discussed.
TL;DR: The features, advantages, and disadvantages of the available, practical techniques for sensing ozone gas in ambient air are described and results strongly suggest that optical ozone sensing using photoluminescent quantum dots is a promising technique.
Abstract: Ozone (O3) gas is widely used as a strong oxidizing agent for many purposes, such as the decomposition/removal of organic contaminants and photoresist, and the deodorization/disinfection of air and water. However, ozone is highly toxic to the human body when the air concentration exceeds about 1 ppm. Therefore, there is increasing demand for simple, sensitive, reliable, and cost-effective techniques for sensing ozone gas. This article describes the features, advantages, and disadvantages of the available, practical techniques for sensing ozone gas in ambient air. The advantages of optical gas sensors as next-generation sensors is specifically introduced. The features of photoluminescent, semiconductor nanoparticles (quantum dots, QDs) as bright phosphors with the potential for various applications is further explored. Lastly, recent research results demonstrating the ozone sensitivity of photoluminescent CdSe-based core-shell quantum dots are presented. These results strongly suggest that optical ozone sensing using photoluminescent quantum dots is a promising technique.
TL;DR: Investigation of the utility of using an ion-depletion zone in a microfluidic device to concentrate exosomes from the culture media of four types of cell lines shows that significantly less damage is incurred following passage through and concentration by the ion- Depleted zone microchannel device compared to concentration by ultra-centrifugation.
Abstract: Exosomes are of increasing research interest because they are integral to cell-cell communication and are implicated in various disease states. Here, we investigated the utility of using an ion-depletion zone in a microfluidic device to concentrate exosomes from the culture media of four types of cell lines. Furthermore, we evaluated the extent of damage to the exosomes following concentration by an ion-depletion zone microchannel device compared with exosomes concentrated by a conventional ultra-centrifugation technique. Our results conclusively demonstrate that significantly less damage is incurred by exosomes following passage through and concentration by the ion-depleted zone microchannel device compared to concentration by ultra-centrifugation. Our findings will help extend the utility of exosomes to various applications.
TL;DR: Methods to visualize GABA in the brain and head of Drosophila melanogaster using MALDI-IMS are described.
Abstract: Drosophila melanogaster is a model organism in neurodegenerative disease research. In neurodegenerative study, the direct spatial information of neurotransmitters such as γ-aminobutyric acid (GABA) in the brain of Drosophila melanogaster is important to understand the role of GABA. Matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS) is an attractive method for direct visualization of neurotransmitters. In this paper, we describe methods to visualize GABA in the brain and head of Drosophila melanogaster using MALDI-IMS.
TL;DR: The progress in and challenges observed during the development of a mass spectrometry-based bioanalytical method for therapeutic mAbs and ADCs are discussed.
Abstract: The increase in the use of therapeutic monoclonal antibodies (mAbs) and antibody-drug conjugates (ADCs) has made the detailed bioanalysis of these drugs essential not only for planning optimal therapeutic programs for clinical practice, but also for evaluating the biological equivalencies in the development of other biosimilars. The ligand binding assays that are widely in use now are being replaced rapidly by the highly accurate, sensitive, and selective analytical method using a mass spectrometer. This review will discuss the progress in and challenges observed during the development of a mass spectrometry-based bioanalytical method for therapeutic mAbs and ADCs.
TL;DR: It was found that Ar-N2 mixed gases introduced into nebulizing gas enhanced the sensitivity of online solid-phase extraction (SPE) with inductively coupled plasma mass spectrometry (ICPMS) for radioactive strontium quantification.
Abstract: The Ar-N2 mix gas effect can easily improve the sensitivity of ICPMS; however, this effect discriminates against Sr. In this study, it was found that Ar-N2 mixed gases introduced into nebulizing gas enhanced the sensitivity of online solid-phase extraction (SPE) with inductively coupled plasma mass spectrometry (ICPMS) for radioactive strontium quantification. An ultrasonic nebulizer (USN) improved the Ar-N2 mixture gases effect of Sr and the mix gases (with USN) enhanced 3.7-times the signal intensity of Sr in normal pure Ar gas (with USN) in an online SPE-ICPMS. By adapting the gas-loading means from a nebulizing gas unit via USN, no careful tuning was necessary for the plasma turning. With this signal enhancement, a 0.06 pg/L detection limit (0.3 Bq/L) was achieved for radioactive strontium (90Sr) in online SPE-ICPMS within 30 min. In addition, environmental paddle water in the Fukushima Nuclear Power Plant was measured and the valued correspond to that obtained by radiometry.
TL;DR: The measurement results of Me-Hg obtained by the present method were in good agreement within the expanded uncertainties with the certified values, and the analytical precision was less than 2%, and the recoveries were 101 ± 1 and 103 ± 3%, respectively.
Abstract: A new determination method was developed for the measurement of methylmercury (Me-Hg) and inorganic mercury (i-Hg) in biological samples using high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) following alkaline extraction. Mercury species in biological samples were extracted with 10% (w/w) tetramethylammonium hydroxide (TMAH) solution at 80°C for 2 h. Methylmercury was completely separated from i-Hg by adamantyl type and octadecylsilyl type columns within 6 and 4 min using isocratic elution, respectively. The detection limits (3σ) of adamantyl and octadecylsilyl columns using the proposed system were 0.08 and 0.13 ng g-1 (as Hg), respectively. Inorganic Hg completely separates from Me-Hg without tailing. The proposed determination methods were applied to several biological certified reference materials (CRMs). The measurement results of Me-Hg obtained by the present method were in good agreement within the expanded uncertainties (k = 2) with the certified values. The analytical precision (n = 3) of Me-Hg was less than 2%, and the recoveries of Me-Hg and i-Hg were 101 ± 1 and 103 ± 3%, respectively. In addition, this method enables the determination of Me-Hg and i-Hg for 20 samples in 1 h.
TL;DR: The viability of the immunosensor was shown to have good selectivity and satisfactory recovery in real serum samples, and the detection principle was developed based on the one-step synthesis of silver nanoparticle seeded onto a gold core.
Abstract: Nanoparticles have been widely developed and shown to have intrinsic enzymatic ability, and are used in biosensors. Compared to biological enzymes used in biosensors, which are expensive and tedious to harvest, enzyme-mimic nanoparticles or nanozymes are both more stable and sensitive. An important area in this work is the development of a simple detection principle of immunosensor based on the one-step synthesis of silver nanoparticle seeded onto a gold core. The gold-silver core-shell nanoparticle acts as a peroxidase mimic, which enables them to oxidise 3,3',5,5'-tetramethylbenzidine (TMB) with H2O2, giving a colourimetric response. Herein, the analytical performance of the nanozyme is exploited to detect haptoglobin as a model analyte in a 96-well plate and measured the colourimetric product using spectrophotometer. The sensitivity of the immunosensor was as low as 100 pg mL-1. The viability of our immunosensor was shown to have good selectivity and satisfactory recovery in real serum samples.
TL;DR: Although the boundary between the hydrophobic and hydrophilic areas in the μPAD is sharpest, the obtained K-scale intensity in measuring of protein concentrations is lower than those of the devices by other methods, and the detection intensity can be raised by optimizing the evaporation rate.
Abstract: We report on the effects of fabrication methods, photolithography, wax printing, screen printing, and craft cutting, on selected properties of microfluidic paper-based analytical devices (μPADs): cost, fabrication precision, wicking rate, and analytical accuracy. Photolithography requires numerous fabrication steps, and an oxygen plasma treatment is necessary when using an aqueous solution. Although the boundary between the hydrophobic and hydrophilic areas in the μPAD is sharpest, the obtained K-scale intensity in measuring of protein concentrations is lower than those of the devices by other methods. Wax printing offers the simplest and fastest fabrication, although solution leakage measures should be taken to improve the wicking rate and to prevent cross-contamination. Screen printing also offers easy fabrication. The screen-printed μPAD has a good wicking performance and shows a high detection intensity. Craft cutting allows automated fabrication of many μPADs at once. The craft cut μPAD has the fastest wicking rate among the four μPADs due to bare cellulose fibers. We consider that the detection intensity of this μPAD can be raised by optimizing the evaporation rate.
TL;DR: A purge-and-trap method using a needle-type extraction device and a gas chromatography-barrier discharge ionization detector for the analysis of formic (FA) and acetic acids (AA) in aqueous samples was suitable for the determination of aqueously FA and AA in complex matrices with simple and rapid sample preparation steps.
Abstract: A purge-and-trap method using a needle-type extraction device and a gas chromatography-barrier discharge ionization detector for the analysis of formic (FA) and acetic acids (AA) in aqueous samples is presented. An activated carbon-based adsorbent, Carboxen 1000, was employed as the extraction medium for the needle-type extraction device. The sampling time was 5 min for collecting headspace gas in a glass vial, including 10 mL of an aqueous sample. The detection limits for FA and AA with a headspace sampling volume of 100 mL were 3.3 and 2.0 mg L-1, respectively. Since the proposed method was based on purge-and-trap collection, it was suitable for the determination of aqueous FA and AA in complex matrices with simple and rapid sample preparation steps. The proposed method was applied to the determination of FA and AA in fruit juice samples and FA generated by the electrochemical reduction of carbon dioxide.
TL;DR: A simultaneous immunosensor based on surface plasmon resonance (SPR) was developed for determination of 3 pesticides instead of the direct competitive enzyme-linked immunosorbent assays (dcELISAs) widely used as individual determination methods.
Abstract: A simultaneous immunosensor based on surface plasmon resonance (SPR) was developed for determination of 3 pesticides -boscalid, clothianidin and nitenpyram- instead of the direct competitive enzyme-linked immunosorbent assays (dcELISAs) widely used as individual determination methods. Carboxy groups that introduced compounds to their pesticides were designed, and conjugates of them and bovine serum albumin were immobilized onto separate channels of the same sensor chip. When a mixture of 3 monoclonal antibodies reacted to each pesticide, and 3 pesticides were injected into the SPR immunosensor, each channel showed specific reactivity at 15 - 93 ng mL-1 for boscalid, 6.7 - 27 ng mL-1 for clothianidin, and 7.3 - 62 ng mL-1 for nitenpyram. Recovery tests using vegetables spiked with a mixture of 3 pesticides showed good results: 75 - 90%, 88 - 104%, and 72 - 105%, respectively, with a high correlation to results of the dcELISAs. The SPR immunosensor would be useful for the determination of pesticide residues in vegetables.
TL;DR: This continuous-flow technique was applicable to the determination of iron ions at levels of several tens of ppb in natural water without preconcentration, and significantly improved both the limits of detection (LOD) and the Limits of quantification (LOQ) for a distance-based PAD.
Abstract: The implementation of continuous flow in paper-based analytical devices (PADs) was challenging because of the large-volume introduction that was created; but this allowed for the development of novel types of PADs for preconcentration, separation, and sensitive detection. In this study, pump-free continuous flow was applied to a distance-based PAD for the determination of iron ions. Continuous flow enabled the introduction of a volume that exceeded what was necessary to fill the hydrophilic channel of a PAD. Thus, this continuous-flow method significantly improved both the limits of detection (LOD) and the limits of quantification (LOQ) for a distance-based PAD by increasing the sample volume that could be introduced into the PAD. The values for LOD and LOQ were 20 and 26 ppb, respectively, which were more than 150-times lower than that obtained using a small sample volume (50 μL), and were comparable to those of inductively coupled plasma-atomic emission spectrometry. The continuous-flow technique was applicable to the determination of iron ions at levels of several tens of ppb in natural water without preconcentration.