Carbonyl compounds in E-cigarette smoke mist were measured using coupled silica cartridges impregnated with hydroquinone and 2,4-dinitrophenylhydrazine, followed by high-performance liquid chromatography. A total of 363 E-cigarettes (13 brands) were examined. Four of the 13 E-cigarette brands did not generate any carbonyl compounds, while the other nine E-cigarette brands generated various carbonyl compounds. However, the carbonyl concentrations of the E-cigarette products did not show typical distributions, and the mean values were largely different from the median values. It was elucidated that E-cigarettes incidentally generate high concentrations of carbonyl compounds.
The purpose of this review article is to outline recent progress in near-infrared (NIR) spectroscopy. Some particular emphasis is put on the delineation of its versatility in analytical chemistry. NIR spectroscopy is versatile in many aspects. For example, it is electronic spectroscopy as well as vibrational spectroscopy. It is also all-round in applications from basic to practical applications. NIR spectroscopy can be applied to various kinds of materials, bulk materials, thin or thick polymers, tablets, human bodies, and so on. It is particularly powerful in non-invasive, non-destructive, and in situ analysis. In this review, the principles and advantages of NIR spectroscopy are described first, and then its applications to various fields, including polymer science, on-line monitoring, inorganic material research, medical diagnosis, and NIR imaging are introduced.
An efficient simplified isotope dilution method was developed to determine four carboxyl containing phytohormones simultaneously in 200 mg of fresh tomato tissues using ultra high performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-MS/MS) with negative electrospray ionization. The four phytohormones are indole-3-acetic acid (IAA), abscisic acid (ABA), jasmonic acid (JA), and salicylic acid (SA). Only one purification step of Oasis MAX solid phase extraction (SPE) was employed to enrich target phytohormones after crude extraction. In addition, two endogenous isomers of JA, (−)-JA and (+)-7-iso-JA, were separated directly. The validated method has been applied to monitor changes of JA, SA, IAA, and ABA in both local and systemic leaves of wild-type and transgenic 35S::prosystemin (35S::PS) tomato lines. Meanwhile, the JA burst amplified by the overexpressed prosystemin in 35S::PS was verified. Furthermore, the spatial and temporal changes of JA, SA, ABA, and IAA were analyzed.
We report on trypsin-stabilized fluorescent gold nanoclusters (Au NCs) for the sensitive and selective detection of Hg2+ ions. The Au NCs have an average size of 1 nm and show a red emission at 645 nm. The photostable properties of the trypsin-stabilized Au NCs were examined, and their photochemical stability was found to be similar to that of CdSe quantum dots. The fluorescence was particularly quenched by Hg2+, and therefore the Au NCs can be used as fluorescent sensors for sensitive and selective Hg2+ detection to a detection limit of 50 ± 10 nM and the quantitative detection of Hg2+ in wide and low concentration range of 50 - 600 nM.
We developed an analytical method for analyzing electronic cigarette (E-cigarette) smoke, and measured the carbonyl compounds and volatile organic compounds generated by 10 brands of second-generation E-cigarettes. A glass filter (Cambridge filter pad) for particulate matter and a solid sorbent tube packed with Carboxen-572 for gaseous compounds were used to collect E-cigarette smoke. These were then analyzed using a two-step elution method with carbon disulfide and methanol, followed by high-performance liquid chromatography (HPLC) and gas chromatography mass spectrometry (GC/MS). Formaldehyde (FA), acetaldehyde (AA), acetone (AC), acrolein (ACR), propanal (PA), acetol (AT), glyoxal (GO), and methyl glyoxal (MGO) were detected by HPLC in some E-cigarettes. Propylene glycol (PG), glycerol (GLY), and some esters were detected by GC/MS. GO and MGO exist mainly as particulate matter. AA, AC, ACR, PA, and AT exist mainly as gaseous compounds. FA exists as both particulate matter and gaseous compounds. These carbonyl compounds have carbon numbers C1 - C3. The main components of E-liquid are PG (C3) and GLY (C3). Therefore, the oxidation of liquids, such as PG and GLY in E-cigarettes upon incidental contact with the heating element in E-cigarette, is suggested as being a possible cause for carbonyl generation. When the puff number exceeds a critical point, carbonyl generation rapidly increases and then remains constant. The results of this study are now being used to determine the following E-cigarette smoking protocol: puff volume, 55 mL; puff duration, 2 s; and puff number, 30. E-cigarette analysis revealed very large variation in carbonyl concentration among not only different brands, but also different samples of the same product. Typical distributions of carbonyl concentration were not observed in any of the E-cigarettes tested, and the mean values greatly differed from median values.
Surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF-MS) using nanoparticles (NPs) and nanostructured surfaces as the LDI-assisting nanomaterials is a soft ionization technique that features minimal fragmentation of analytes. As compared to traditional matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) using organic matrices, SALDI-MS affords several advantages, such as the ability to detect small molecules (<500 Da), easy sample preparation, low-noise background, high salt tolerance, and fast data collection without the use of an organic matrix. The performance of SALDI has been further improved recently in terms of the detection sensitivity, detection mass range from the low- to the high-mass region, a soft LDI process, the detection of both polar and nonpolar compounds, the selective detection of analytes from a complex mixture using functionalized NPs, and various applications, including imaging mass spectrometry. This review summarizes recent developments pertaining to various NPs and nanostructured surfaces for SALDI-MS.
This review addresses recent developments in electrochemistry and electroanalytical chemistry of carbon nanotubes (CNTs). CNTs have been proved to possess unique electronic, chemical and structural features that make them very attractive for electrochemical studies and electrochemical applications. For example, the structural and electronic properties of the CNTs endow them with distinct electrocatalytic activities and capabilities for facilitating direct electrochemistry of proteins and enzymes from other kinds of carbon materials. These striking electrochemical properties of the CNTs pave the way to CNT-based bioelectrochemistry and to bioelectronic nanodevices, such as electrochemical sensors and biosensors. The electrochemistry and bioelectrochemistry of the CNTs are summarized and discussed, along with some common methods for CNT electrode preparation and some recent advances in the rational functionalization of the CNTs for electroanalytical applications.
In this study, a simple and sensitive aptamer-based colorimetric method for the detection of Ochratoxin A by using gold nanoparticles (AuNPs) has been developed. In this assay, unmodified gold nanoparticles (AuNPs) were used as probes with a 36-mer aptamer as recognition element. In the absence of ochratoxin A, free aptamer could be adsorbed onto the surface of AuNPs and protect AuNPs from aggregation even with high concentrations of salt. The salt-induced aggregation of AuNPs was caused by the specific recognition of aptamers with OTA. Under optimum conditions, calibration modeling showed that the analytical linear range covered from 32 to 1024 ng/mL and the detection limit of 20 ng/mL was realized successfully. This proposed colorimetric bio-assay also showed high selectivity over other antibody based methods. Meanwhile, this strategy was further used to determine the concentrations of ochratoxin A in white wine sample with satisfying recovery rates.
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.
The present article reports the application of hexamethylsilazane (HMDS) modified filter paper for ultrasensitive detection of Hg2+, Co2+ and Zn2+. By chemical vapor deposition of HMDS, a highly hydrophilic filter paper was fabricated to a low wetting (hydrophobic) substrate. The water contact angle (θ) of modified paper was ∼128°, whereas scanning electron and atomic force microscopy confirmed the surface modification. Using chromogenic reagents, a one-step assay for aforementioned ions was demonstrated onto pristine as well as hydrophobic paper. The assay was completed in less than 10 min and the end-result was in form of a color change that could be easily read by the naked eye. The limit of detection on modified paper was 0.5 ppb, which was 5-order of magnitude superior to that observed on pristine paper. The proposed method was successfully applied for semi-quantitative determination of Hg2+ ions in real wastewater samples.
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.
Silver nanoprisms (AgNPrs) have a unique localized surface plasmon resonance, resulting in strong absorption and scattering within the visible light region. In this work, we propose image acquisition from colloidal solutions of AgNPrs using a combination of transmitted and scattered light. The developed measurement technique could be carried out by separately recording transmitted and scattering images of the solutions, using a mobile device camera prior to a calculation of the empirical absorption value (IA). The IA value of green for AgNPrs solutions was found to be in agreement with the absorption spectra obtained using a conventional spectroscopic technique. This technique was utilized for the quantifications of hydrogen peroxide and glucose. Good linearities between ΔIA and those typical analytes were observed. The limit of detection for the typical biosensor of glucose was 19.8 μM. As such, we expect the methodology herein developed for hydrogen peroxide and glucose determinations by means of monitoring the color change of transmitted and scatting images from solutions to contribute to the development of simple, rapid, and reliable detection systems to be further applied to biochemical analysis and clinical diagnosis, as well as to household biosensor applications.
We propose a method to evaluate the surface structure of Escherichia coli focusing on the doping state of bacterial cells into polypyrrole (PPy) matrix. We found that the orientation of doping states of E. coli O rough was different from those of other serotypes of E. coli cells, which had O-antigen on their outer membrane. The results indicated that more than seventy percent of E. coli cells having O-antigen was horizontally doped into PPy matrix based on the chemical structure and the placement of O-antigen. On the other hand, the percentage for horizontal doping state of E. coli O rough cells was only approximately fifty percent. Moreover, the cells of each E. coli serotypes were specifically bound to their own shape-complementary cavities on the microspheres, but the binding affinity of E. coli O rough was a bit lower than that of other serotypes.
Fluidic chip fabrication technologies using three-dimensional (3D) printing have received broad attention recently. Herein, we describe a new method for fabricating polydimethylsiloxane (PDMS) fluidic chips using a 3D-printed polyvinyl alcohol (PVA) or acrylonitrile butadiene styrene (ABS) template and polymer coating. In this method, polyethylene glycol (PEG) was coated on the 3D-printed template. This coated template was immersed in liquid PDMS, and subsequently the PDMS was cured. Space can be created between the template and PDMS by removing this liquid PEG from the channel. This space renders template removal easier. A flow path is formed by dissolving the template with a solvent. These PDMS chips are used for flow injection measurement.
For the rapid, easy, and safe purification of alkali and alkaline-earth elements from rock samples for stable isotope analysis, we developed a semi-automated, high-throughput procedure using borate fusion and an ion chromatography system equipped with a fraction collector. This HF-free procedure for the decomposition of silicate rock samples can be performed in a short time without isotope fractionation; the purification procedure enables the collection of baseline-separated peaks of multiple target elements and the complete removal of interference matrices from reagents and samples. The accuracy of this procedure was verified by confirming the correspondence of stable isotopic values of Li, Mg, Sr (δ7Li, δ26Mg, δ88Sr) and radiogenic isotopic values of Sr (87Sr/86Sr) to previously reported values in various geochemical reference materials in which the concentration range of Li was 7.78 - 86.6 ng g-1, that of Mg was 0.02 - 26.9%, and that of Sr was 178 - 7240 ng g-1. These results demonstrate that this procedure, which allows for the concurrent multi-isotope analysis of alkali and alkaline-earth elements in the same sample, is applicable to a wide variety of sample types.
Simply structured conjugated compounds with cyanoacrylate (CA 1 - 4) and acrylonitrile (AN 1 - 4) terminal groups were synthesized by a Knoevenagel condensation reaction in one step and investigated for their recognition properties to p-toluenethiol by UV-vis, fluorescence spectra, and FT-IR measurements. When p-toluenethiol was added to CA 1, the FT-IR spectra revealed a cleavage of alkene caused by the addition reaction between p-toluenethiol and CA 1. An increase in p-toluenethiol concentration, a blue-shifted absorption band, and a decrease in the fluorescence intensity of CA 1 were observed because of the decrease in its effective conjugated length. Therefore, the most simply structured CA 1 was found to be the most effective and the most sensitive chemical sensor for p-toluenethiol.
This manuscript describes the determination of ammonia (NH3) in aqueous samples by purge-and-trap extraction using a needle-type extraction device with gas chromatography-barrier discharge ionization detector (GC-BID). NH3 was purged from the aqueous samples in basic conditions and then salted out with sodium chloride. Purged ammonia was trapped onto non-volatile carboxylic acid-coated macroporous terephthalic acid particles, which were contained within the needle-type extraction device. The analyte (NH3) was thermally desorbed by heating the extraction needle in the GC injection port, and detected by BID. After the optimization of both purge and extraction conditions, the linearity and sensitivity of the proposed method were evaluated. The limit of detection was found to be 2.0 mg L-1 at a headspace sampling volume of 100 mL. The method applicability was confirmed by the determination of spiked NH3 in tap water and river water samples.
We demonstrate that electorogenerated chemiluminescence (ECL) of an organometallic Eu(III) complex, tris(dibenzoylmethane)phenanthroline europium(III), whose emission spectra is very sharp with the maximum wavelength of 612 nm, can be used as a light source for the detection of PO43- based on changing the absorbance of the ion associate of malachite green (MG+) and phosphomolybdic acid. The ECL was also applied to measure the absorbance of MG+. With the detection system we established, absorbance up to ∼1.6 with a change of ∼0.1 could be detected.
Illudin S from mushroom, such as Omphalotus japonicus and illudens, is a natural sesquiterpene analog with strong anti-tumor and antiviral activities. These illudins compounds are highly effective against various drug-resistant cancers that show extreme cytotoxicity an in vitro assay. However, it is difficult to obtain a sufficient amount of highly pure illudin S from a natural product by simple, efficient and low-cost purification techniques. Here, we offer to apply the high-speed countercurrent chromatography for the preparative purification of illudin S from mushroom extract. For a two-solvent system, the optimal condition of hexane/ethyl acetate/methanol/water (1/5/1/5, v/v/v/v) was optimized to obtain pure illudin S from a crude extract. This purified component was evaluated by liquid chromatography (high-purity >99%) and tandem mass spectrometry. The yield amounts of illudin S (1.3 mg/about 10 g Omphalotus japonicus) at one running are determined by liquid chromatographic calibration. It is concluded that by requiring a natural material and cost-effectiveness, our method represents a significant improvement over complicated techniques for the purification of illudin S from natural materials.
Molybdenite (MLN) was physically co-adsorbed with Ag nanoparticles (Ag) on a glassy carbon electrode (GCE) for selectively sensing of ascorbic acid (AA). The composite was characterized with a scan electron microscope, a high-temperature confocal laser scanning microscope, an X-ray diffractometer, an X-ray fluorescence analyzer and electrochemical methods. The prepared MLN/Ag-GCE sensor exhibited good properties including a linear range from 3.0 × 10-5 to 1.0 × 10-3 M toward AA, a low detection limit of 1.5 × 10-5 M, good selectivity, excellent reproducibility, and good stability. The synergistic effect between MLN and Ag nanoparticles results in an enhancement of the electrocatalytic activity for molybdenite.