The locations and volumes of the contents of a single HepG2 cell were visualized under three-dimensional (3D) holographic and tomographic (HT) laser microscopy, colored by refractive index, not staining. After trapping the specific area of a target cell in a nanospray tip, quantification was performed by live single-cell mass spectrometry. Comparison of the HepG2 cells’ before and after 3D-HT images allowed the inference of the precise volume and original location of the trapped cell contents. The total amount of a trapped molecule was estimated. The images also revealed morphological changes in the cell structure caused by the manipulation.
The color-changing phenomenon of hydrophobic bisazo dye, Sudan III in an acetonitrile solution against the addition of concentrated sulfuric acid has been discovered and the chromic properties investigated. Based on observations, a novel quantification method of concentrated sulfuric acid has been developed. Sudan III changes its color from orange to blue against a small volume of sulfuric acid, and the acetonitrile solution of Sudan III is the most suitable for observing the color-change phenomenon. 1H-NMR and UV-Vis spectroscopic studies showed that the color-change mechanism of Sudan III against sulfuric acid is due to the protonation of the dye by sulfuric acid. This phenomenon is applicable to the quantification of concentrated sulfuric acid by introducing the Hammett acidity function. The proposed method requires only a small amount of the sample, 0.04 mL, and enables rapid quantification.
A low-interferences enzymatic sensor for evaluating the antioxidant capacity was developed. Xanthine oxidase was used to produce superoxide radicals that spontaneously dismutate to hydrogen peroxide. Low xanthine concentrations were used to minimize the rapid dismutation of the superoxide radical before its fast reaction with antioxidants. The sensor operates in the reduction mode, and evaluations with low interferences of the antioxidant capacity are based on the detection of remaining hydrogen peroxide using Prussian blue electrodes at low potentials. The linear calibration graph is between 2 – 10 μM ascorbic acid. No interferences were observed from easily oxidisable substances including uric acid, which is produced in the enzymatic reaction or other substances usually found in foods. The method was used to evaluate the antioxidant capacity in different real juice samples.
An improved GC method in terms of sensitivity and decrease in the analysis time has been developed for the analysis of eight guanidino compounds: guanidine (G), methylguanidine (MG), creatinine (CTN), guanidinoacetic acid (GAA), guanidinobutyric acid (GBA), guanidinopropionic acid (GPA), argenine (Arg), and guanidinosuccinic acid (GSA), using isovaleroylacetone (IVA) and ethyl chloroformate (ECF) as derivatizing reagents. The separation was obtained from column HP-5 (30 m × 0.32 mm i.d.) with film thickness of 0.25 μm within 11 min. The linear calibrations were obtained with 0.5 to 50 μg/mL with coefficient of determination (R2) within 0.9969 – 0.9998. Limits of detections (LODs) were within 5 – 140 ng/mL. The derivatization, separation and determination was repeatable (n = 6) with relative standard deviation (RSD) within 1.2 – 3.1%. The guanidino compounds were determined in deproteinized serum of healthy volunteers and uremic patients within below LOD to 8.8 μg/mL and below LOD to 43.99 μg/mL with RSD within 1.4 – 3.6%. The recovery of guanidino compounds calculated by standard addition from serum was within 96.1 – 98.9%, with RSD 1.4 – 3.6%.
Liquid chromatography/linear ion trap mass spectrometry (LC/LIT-MSn) was used to construct a database of disperse dyes. Fifty-three standard dyes were subjected to LC/LIT-MSn and characterized based on their mass spectra (MS, MS2, and MS3), values of λmax (maximum absorption wavelength in the UV-visible spectrum), and retention times. The results demonstrate that it is possible to reliably identify coexisting dyes that cannot be separated by LC or detected by diode array detection due to their low molecular absorption coefficients. In addition, the by-products included in the standard dyes were found to provide important information for the identification and discrimination of dyestuffs synthesized using different processes. The confirmation of the effectiveness of LC/LIT-MSn analysis in detecting small amounts of disperse dyes in this study shows its potential for use in the discrimination of dyed fibers obtained at crime scenes.
Human plasma arginine vasopressin (AVP) levels serve as a clinically relevant marker of diabetes and related syndromes. We developed a highly sensitive method for measuring human plasma AVP using high-performance liquid chromatography tandem mass spectrometry. AVP was extracted from human plasma using a weak-cation solid-phase extraction plate, and separated on a wide-bore octadecyl reverse-phase column. AVP was quantified in ion-transition experiments utilizing a product ion (m/z 328.3) derived from its parent ion (m/z 542.8). The sensitivity was enhanced using 0.02% dichloromethane as a mobile-phase additive. The lower limit of quantitation was 0.200 pmol/L. The extraction recovery ranged from 70.2 ± 7.2 to 73.3 ± 6.2% (mean ± SD), and the matrix effect ranged from 1.1 – 1.9%. Quality-testing samples revealed interday/intraday accuracy and precision ranging over 0.9 – 3% and –0.3 – 2%, respectively, which included the endogenous baseline. Our results correlated well with radioimmunoassay results using 22 human volunteer plasma samples.
Using environment-friendly materials for sensing toxic metal ions has drawn significant attention in recent research. Herein, we present an aqueous synthesis of stable CdS quantum dots (QDs) using thiol-functionalized poly(vinyl alcohol) (PVA) as the unique capping ligand for the detection of trace Hg2+ in environmental water samples. The CdS QDs with an average size of 3.3 nm had good water-solubility and favorable fluorescence with a quantum yield of 32.8% and a longer luminescence lifetime of 31.9 ns. The fluorescence intensity of QDs aqueous solution in the 520 nm wavelength was quenched upon the addition of Hg2+. Under the optimal conditions, the ratio of the blank fluorescence intensity to the quenched fluorescence intensity was linearly proportional to the Hg2+ concentration from 2 to 4000 nM with a detection limit of 1 nM. Also, many co-existing metal ions were not interfered with the detection of Hg2+. This nanomaterial was successfully applied to the measurement of Hg2+ in water samples.
A method for quantifying iodine in infant formula is described. Nitric acid and hydrogen peroxide converted iodine into iodate in microwave-assisted digestion and prevented iodine volatilization and memory effects. Acetic acid as a carbon source was added to both the sample and standard solutions as a countermeasure against carbon charge transfer to iodine and the addition of acetic acid helped to enhance the sensitivity. The instrument limit of quantification was 0.1 ng mL−1 and the relative standard deviation was less than 3%. The spike recoveries were between 94.8 and 106%. Good agreement with the values obtained using the tetramethylammonium hydroxide method was obtained for infant formula sold in several countries. This method permitted the simultaneous determination of iodine and 12 other important elements (Na, Mg, P, K, Ca, Cr, Mn, Fe, Cu, Zn, Se and Mo) in infant formula.
A lipophilic oxygen radical absorbance capacity (L-ORAC) assay is an evaluation of the antioxidant capacity of solutions of lipophilic compounds. The concentrations of fluorescein, radical generator, and Trolox standard solutions were optimized to improve the precision of the assay. An interlaboratory study using two antioxidant solutions and three food extracts as test samples conducted in accordance with harmonized protocol demonstrated satisfactory L-ORAC measurements; the intermediate precision relative standard deviations (RSDint) ranged from 7.0 to 16.7%, the reproducibility relative standard deviations (RSDR) ranged from 14.8 to 19.4%, and the HorRat values ranged from 1.35 to 1.78.
Trace moisture quantitation is crucial in medical, civilian and military applications. Current aquametry technologies are limited by the sample volume, reactivity, or interferences, and/or instrument size, weight, power, cost, and complexity. We report for the first time on the use of a pulsed discharge helium ionization detector (PDHID-D2) (∼196 cm3) for the sensitive (limit of detection, 0.047 ng; 26 ppm), linear (r2 >0.99), and rapid (< 2 min) quantitation of water using a small (0.2 – 5.0 μL) volume of liquid or gas. The relative humidity sensitivity was 0.22% (61.4 ppmv) with a limit of detection of less than 1 ng moisture with gaseous samples. The sensitivity was 10 to 100 to fold superior to competing technologies without the disadvantages inherent to these technologies. The PDHID-D2, due to its small footprint and low power requirement, has good size, weight, and power-portability (SWAPP) factors. The relatively low cost (∼$5000) and commercial availability of the PDHID-D2 makes our technique applicable to highly sensitive aquametry.
The pneumatic nebulization gas–solid microextraction device fascinating us is because it directly atomized organic samples to cross a solid-phase microextraction (SPME) cartridge without any pretreatment. In this work, both the spray chamber and SPME column of the extraction device were heated. We found that this would significantly improve the extraction efficiency of this method. Then, this method was used to detect seven triazine herbicides (atraton, desmetryn, atrazine, terbumeton, terbuthylazine, terbutryn, and dipropetryn) in drinking alcohol samples. The experimental results indicated that this extraction procedure could conveniently, efficiently and accurately concentrate any triazine herbicides from drinking alcohol samples. The limits of detection (LODs) were from 0.08 to 0.23 μg L−1, the limits of quantification (LOQs) were from 0.27 to 0.78 μg L−1. We used this method to detect triazine herbicides in five white spirit samples. Four concentrations were chosen (5, 25, 50 and 100 μg L−1) as the amounts of spikes to investigate the recovery and precision of the present PN-GSME method. The recoveries ranged from 95.91 to 106.67%. The relative standard deviations were not more than 6.51%. Also this method matches the requirement of the maximum residue limits of the European Union.
Ion transport through a single channel of gramicidin A (GA) within the bilayer lipid membrane (BLM) between two aqueous phases (W1 and W2) has been analyzed based on the electroneutrality principle. The single-channel current increases in proportion to the magnitude of the applied membrane potential and is also dependent on the permeability coefficients of electrolyte ions (K+ and Cl−). By varying the ratio of the concentration of KCl in W1 to that in W2, the ratio of the diffusion coefficient of K+ in the BLM to that of Cl− in the BLM can be evaluated.
A fluorescence resonance energy transfer (FRET) system between carbon dots (C-dots) and amine-capped gold nanoparticles (AuNPs) was developed for the selective determination of 2,4,6-trinitrotoluene (TNT). C-dots have an intrinsic florescence emission depending on their exciting wavelength. In the presence of AuNPs, C-dots adsorb on the Au surfaces, and NPs treat as energy acceptor, which can receive light emitted by C-dots, leading to decrease the fluorescence intensity of C-dots. Furthermore, it is observed that nitroaromatic compounds, especially TNT, could restore this fluorescence due to selective interaction with AuNPs via amine groups, and so releasing the C-dots. Based on this effect, a sensitive and selective fluorescence turn-on probe was designed for the determination of TNT. Some important factors including AuNPs and C-dot concentrations and media pH, which would affect the efficiency of the probe, were optimized. Under the optimum experimental conditions, good linear relationships in the range of 7 – 250 nmol L−1 TNT with the detection limit of 2.2 nmol L−1 were obtained. The proposed method was satisfactorily applied to the determination of TNT in the environmental water samples. Compared with previous reports, the developed method has relatively high sensitivity, short analysis time, low cost and ease of operation.
We have found that a positively charged cationic copper phthalocyanine, Alcian blue (Alcian blue 8GX), can efficiently quench the fluorescence of an oppositely charged red fluorescent phthalocyanine compound with a matched molecular structure, tetrasulfonated aluminum phthalocyanine (AlS4Pc), because of the formation of an ion pair complex (AlS4Pc-Alcian blue 8GX) that exhibits almost no fluorescence. An investigation was carried out on the fluorescence recovery of AlS4Pc-Alcian blue 8GX caused by a series of anionic surfactants containing a sulfonic group (sodium dodecylbenzenesulfonate (SDBS), sodium lauryl sulfate (SLS), and sodium dodecyl sulfate (SDS)). The results showed that SDBS exhibited a significant response, and the highest sensitivity among the surfactants. Due to its high efficiency of fluorescence quenching and the high level of fluorescence recovery, direct observes can even be performed by the naked eye. The results revealed that the Alcian blue 8GX-AlS4Pc ion-pair complex fluorescent probe only responded to SDBS in the low-concentration range. Based on the new founding, this study proposed a novel principle and method of fluorescence enhancement to specifically measure the concentration of SDBS, thereby achieving a highly sensitive and highly specific determination of SDBS. Under the optimal conditions, the fluorescence intensity (If) of the system and the concentration of SDBS in the range of 1 × 10−7 – 1 × 10−5 mol/dm3 exhibited a good linear relationship. This method is highly sensitive, and the operation is simple and rapid. It had been applied for the quantitative analysis of SDBS in environmental water, while achieving satisfactory results compared with those of the standard method. This study developed a new application of the fluorescent phthalocyanine compounds used as molecular probes in analytical sciences.
In this study, 3 automobile window glass manufacturers were identified based on refractive index, XRF, and XAFS analyses. The samples were classified into the corresponding groups using XRF, which should be the first step for identification. Samples having different manufacturing times showed differences in the refractive index. Based on XAFS, the amplitude of the EXAFS spectra and the intensities of Fourier transforms differed between manufacturers. In the scheme for manufacturer identification proposed in this study, performing XRF and refractive index studies is the first step. The concentrations of CeO2, MgO, Al2O3, and K2O allowed us to distinguish among manufacturers. Secondly, for samples containing cerium, we discriminated between manufacturer based on the amplitude of the EXAFS spectra and the intensities of Fourier transforms. As a result, the manufacturers of the 75 samples used in this study were multilaterally identified.
The accurate detection and identification of food-borne pathogenic microorganisms is critical for food safety nowadays. In the present work, a visual DNA microarray was established and applied to detect pathogens commonly found in food, including Salmonella enterica, Shigella flexneri, E. coli O157:H7 and Listeria monocytogenes in food samples. Multiplex PCR (mPCR) was employed to simultaneously amplify specific gene fragments, fimY for Salmonella, ipaH for Shigella, iap for L. monocytogenes and ECs2841 for E. coli O157:H7, respectively. Biotinylated PCR amplicons annealed to the microarray probes were then reacted with a streptavidin-alkaline phosphatase conjugate and nitro blue tetrazolium/5-bromo-4-chloro-3′-indolylphosphate, p-toluidine salt (NBT/BCIP); the positive results were easily visualized as blue dots formatted on the microarray surface. The performance of a DNA microarray was tested against 14 representative collection strains and mock-contamination food samples. The combination of mPCR and a visual micro-plate chip specifically and sensitively detected Salmonella enterica, Shigella flexneri, E. coli O157:H7 and Listeria monocytogenes in standard strains and food matrices with a sensitivity of ∼102 CFU/mL of bacterial culture. Thus, the developed method is advantageous because of its high throughput, cost-effectiveness and ease of use.
The spectroscopic characteristics and analytical capability of argon–nitrogen (Ar–N2) inductively coupled plasma (ICP) in axially viewing optical emission spectrometry (OES) were examined and figures of merit were determined in the present study. The spectroscopic characteristics such as the emission intensity profile and the excitation temperature observed from the analytical zone of Ar–N2 ICP in axially viewing ICPOES, in order to elucidate the enhancement of the emission intensity of elements obtained in our previous study, were evaluated and compared to those of the standard ICP. The background and emission intensities of elements as well as their excitation behavior for both atom and ion lines were also examined. As results, a narrower emission intensity profile and an increased excitation temperature as well as enhancements for both background and emission intensities of elements, which could be due to the ICP shrunken as well as the enhancement of the interaction between the central channel of the ICP and samples introduced, were observed for Ar–N2 ICP in axially viewing OES. In addition, the elements with relatively higher excitation and ionization energies such as As, Bi, Cd, Ni, P, and Zn revealed larger enhancements of the emission intensities as well as improved limits of detection (LODs), which were also attributed to the enhanced interaction between Ar–N2 ICP and the samples. Since the Ar–N2 ICP could be obtained easily only by the addition of a small amount of N2 gas to the Ar plasma gas of the standard ICP and no optimization on the alignment between Ar–N2 ICP and the spectrometer in commercially available ICPOES instruments was needed, it could be utilized as simple and optional excitation and ionization sources in axially viewing ICPOES.
Diagnosis of periodontal disease by Fourier transform infrared (FT-IR) microscopic technique was achieved for saliva samples. Twenty-two saliva samples, collected from 10 patients with periodontal disease and 12 normal volunteers, were pre-processed and analyzed by FT-IR microscopy. We found that the periodontal samples showed a larger raw IR spectrum than the control samples. In addition, the shape of the second derivative spectrum was clearly different between the periodontal and control samples. Furthermore, the amount of saliva content and the mixture ratio were different between the two samples. Partial least squares discriminant analysis was used for the discrimination of periodontal samples based on the second derivative spectrum. The leave-one-out cross-validation discrimination accuracy was 94.3%. Thus, these results show that periodontal disease may be diagnosed by analyzing saliva samples with FT-IR microscopy.
Benzo[c]fluorene (BcFE) concentrations in benzene/ethanol extracts of airborne particulates were determined by high-performance liquid chromatography (HPLC) with fluorescence detection. HPLC conditions were as follows: columns, two ZORBAX Eclipse PAH (4.6 i.d. × 250 mm, 3.5 μm) and one Inertsil ODS-P (4.6 i.d. × 250 mm, 5 μm) in series; mobile phase, acetonitrile–water (98:2, v/v), 0.3 mL/min; detection wavelengths, excitation 309 nm, emission 354 nm. Particulate-phase BcFE concentrations in the atmosphere varied seasonally (winter > summer). The concentrations were 11000 ± 6100 pg m−3 (winter) and 40 ± 12 pg m−3 (summer) in Beijing, China, and 13 ± 5.0 pg m−3 (winter) and 2.7 ± 0.52 pg m−3 (summer), in Kanazawa, Japan. In both cities, the particulate-phase BcFE concentration in the atmosphere was lower than that of benzo[a]pyrene (BaP) by a factor of 0.03 – 0.43. However, the mutagenic contribution of particulate-phase BcFE in the atmosphere in winter calculated from the mutagenicity relative potency factor was greater than that of BaP.
A cross-reactive sensor array consisting of polyion complexes (PICs) between anionic enzymes and poly(ethylene glycol)-modified (PEGylated) polyamines has been used to identify the source of mammalian sera. Although the catalytic activity of enzymes was inhibited by PIC formation with PEGylated polyamines, the subsequent addition of sera caused enzyme releases from PICs through competitive interactions between PICs and serum proteins, generating unique response patterns of changes in the enzyme activity. Linear discriminant analysis of the obtained patterns enabled the discrimination of five sera from different mammalian sources.
A simple visual method for determining the total iron in human serum is proposed based on color development in the nanospace of mesoporous silica MCM-41 and a chromogenic ligand bathophenathroline disulfonate (BPS). Observing the color intensity of a complex between iron(II) and BPS devloped on the MCM-41 material by the naked eye enabled us to quntify iron(II) with a detection limit of 0.5 μM. The BPS-loaded MCM-41 was successfully applied for quantifying the total iron in human serum.
A rapid and sensitive flow method, based on the combination of on-line solvent extraction with reversed micellar mediated chemiluminescence (CL) detection using rhodamine B (RB), was developed for the determination of antimony(III) and antimony(V) in aqueous samples. The on-line extraction procedure involved ion-pair formation of the antimony(V) chloro-complex anion with the protonated RBH+ ion and its extraction from an aqueous hydrochloric acid solution into toluene, followed by phase separation using a microporous membrane. When in a flow cell of a detector, the ion-pair in the extract driven was mixed with the reversed micellar solution of cetyltrimethylammonium chloride in 1-hexanol-cyclohexane/water (0.60 mol dm−3 H2SO4) containing cerium(IV), its uptake by the reversed micelles and the subsequent CL oxidation of RB with Ce(IV) occurred easily, then the produced CL signal was measured. Using the proposed flow method under the optimized experimental conditions, a detection limit (DL) of 0.35 μmol dm−3 and a linear calibration graph with a dynamic range from DL to 16 μmol dm−3 were obtained for Sb(V) with a precision of 1.4% relative standard deviation (n = 5) at the Sb(V) concentration of 8.2 μmol dm−3. The present method was successfully applied to the determination of Sb(V) in water samples and to the differential determination of Sb(III) and Sb(V) in copper electrolyte industrial samples, where total antimony Sb(III) + Sb(V) was determined after oxidation of Sb(III) to Sb(V) with Ce(IV) and Sb(III) was calculated by difference, for which the DL was almost the same as that for Sb(V).
2-Hydroxytryptanthrin (T2OH) and its sodium salt (sodium tryptanthrin-2-olate, T2ONa) were synthesized as near-infrared (NIR) dyes for fluorescent imaging. The absorption maxima (λa,max) of T2OH under a pH range from 1.3 to 7.2 and from 8.5 to 10.6 were ca. 410 nm and ca. 495 nm, respectively. Moreover, the fluorescence maxima (λf,max) were ca. 660 nm regardless of the pH range. T2ONa was water soluble and the λf,max were ca. 660 nm in both aprotic and protic solvents.
Multiphoton ionization time-of-flight mass spectrometry (MPI-TOFMS) combined with a pulsed laser for sample vaporization was developed for the detection of a low-volatile compound in a solution. A solution containing Taiwanin A ((3E,4E)-3,4-bis(1,3-benzodioxol-5-ylmethylene)dihydro-2(3H)-furanone), which is a lignan that has an anticancer effect, was employed in the present study. Consequently, Taiwanin A could be detected by irradiating a laser pulse for vaporization to an inlet nozzle, rather than by heating. Therefore, the present method could be effective for detecting compounds with lower volatilities in a liquid sample.
Edited and published by : The Japan Society for Analytical Chemistry Produced and listed by : Sobun Print Co., Ltd. (Vol.25 No.6-) Chuo Printing Co., Ltd. (Vol.14-Vol.18, Vol.20-Vol.25 No. 5) The Japan Society for Analytical Chemistry (Vol.19)