Oligosaccharides attached to proteins are very challenging analytical targets because of their wide variety and complexity. Reliable analytical methods for the quantitative profiling of glycoprotein glycans is essential for investigating their functions in biological systems, and for use in the production of recombinant glycoproteinaceous pharmaceuticals. The most reliable and straightforward method to view glycan compositions is fluorescent labeling, followed by liquid chromatography or capillary electrophoresis. This article briefly summarizes the methods used for releasing glycans from glycoproteins and the purification with various solid phases, labeling, and separation by liquid chromatography and capillary electrophoresis of the released glycans.
This review highlights on-line sample preconcentration by large-volume sample stacking with an electroosmotic flow pump (LVSEP) in microscale electrophoresis. LVSEP requires only a hydrodynamic sample injection into the whole capillary/microchannel and a constant voltage application, i.e., without polarity switching, providing an efficient sensitivity enhancement with a relatively easy experimental procedure without loss of the separation efficiencies. Recent developments and applications of LVSEP are briefly reviewed from the first LVSEP study in 1999 with categorization on the basis of separation modes, including zone electrophoresis, cyclodextrin- and affinity-based separation modes and non-aqueous capillary electrophoresis.
To achieve a highly sensitive and prompt elemental analysis of materials on heat-sensitive substrates, like living tissues, the atmospheric plasma soft-ablation method (APSA) was developed. The damage-free plasma, which has room temperature and no risk of electrical shock, was used as a sampling medium for materials, and the sampled materials were introduced to inductively coupled plasma mass spectrometer (ICP-MS). By using APSA, a mass signal of molybdenum, using a thin molybdenum-grease layer, was successfully obtained without damaging the subjacent glass substrate. The use of a hydrogen admixture to generate the plasma was examined in order to achieve more effective sampling by utilizing chemical reactions between radicals in the plasma and the sample material. As a result, the sensitivity of all measured elements contained in tablet supplements increased by up to 20 times upon the addition of 1% hydrogen, even though the plasma-gas temperature did not change significantly.
We developed an injection gas heating system for introducing large droplets, because we want to effectively to measure elements in a single cell. This system was applied to ICP-atomic emission spectrometry (ICP-AES), to evaluate it performance. To evaluate the effect of the emission intensity, the emission intensity of Ca(II) increased to a maximum of tenfold at 147°C and the peak was shifted upstream of the plasma. To investigate in detail the effect of an injection gas heating system, we studied different conditions of the injection gas temperature and droplet volume. When the injection gas temperature was 89°C, smaller droplets were easily ionized. At 147°C, the emission intensity ratio and the absolute amount of the sample including the droplet exhibited close agreement. These results show the advantages of the injection gas heating system for large droplet introduction, and the sufficient reduction in the solvent load. The solvent load could be reduced by heating to 147°C using the system.
A simple method of graphite-furnace atomic-absorption spectrometry (GFAAS) after solid-phase extraction (SPE) was developed for the determination of diphenylarsinic acid (DPAA), phenylarsonic acid (PAA), and inorganic arsenic (iAs) in drinking water. This method involves the simultaneous collection of DPAA, PAA, and iAs using three stacked SPE disks, i.e., an Empore SDB-XD disk (the upper layer), an activated carbon disk (the middle layer), and a Cation-SR disk loaded with Zr and Ca (ZrCa-CED; the lower layer). A 200-mL aqueous sample was adjusted to pH 3 with nitric acid and passed through the SPE disks at a flow rate of 15 mL min−1, to concentrate DPAA on the SDB-XD disk, PAA on the activated carbon disk, and iAs on the ZrCa-CED. The As compounds were eluted from the disks with 10 mL of ethanol containing 0.5 mol L−1 ammonia solution for DPAA, 20 mL of 1 mol L−1 ammonia solution for PAA, and 20 mL of 6 mol L−1 hydrochloric acid for iAs. The eluates of DPAA, PAA, and iAs were diluted to 20, 25, and 25 mL, respectively, with deionized water, and then analyzed by GFAAS. The detection limits of As (three-times the standard deviation (n = 3) of the blank values) were 0.13 and 0.16 μg L−1 at enrichment factors of 10 and 8, respectively, using a 200-mL water sample. Spike tests with 2 μg (10 μg L−1) of DPAA, PAA, and iAs in 200 mL of tap water and bottled drinking water showed good recoveries (96.1 – 103.8%).
For the rapid and precise sorting of steel scrap with relatively high contents of copper, laser-induced breakdown spectroscopy (LIBS) is a promising method. It has several advantages such that it can work under ambient air atmospheres, and specimens can be tested without any pretreatment, such as acid digestion, polishing of the surface of the specimens, etc. For the application of LIBS for actual steel scrap, we obtained emission spectra by an LIBS system, which was mainly comprised of an Nd:YAG laser, an Echelle-type spectrometer, and an ICCD detector. The standard reference materials (SRMs) of JISF FXS 350-352, which are Fe-Cu binary alloy and have certified concentrations of copper, were employed for making calibration lines. Considering spectral interferences from the emission lines of the iron matrix in the alloys, Cu I lines having wavelengths of 324.754 and 327.396 nm could be chosen. In five replicate measurements of each SRM, shorter delay times after laser irradiation and longer gate widths for detecting the transient emission signal are suggested to be the optimal experiment parameters. In the determination process, utilizing the calibration line from Cu I 327.396 nm was better because of less spectral interference. By using 200 pulsed laser shots for the measurement sequence, a limit of detection of 0.004 Cu at% could be obtained.
Diphosphate (pyrophosphate, PPi) is vital for organisms, and therefore its detection is of special importance. In this paper, one cadmium complex of terpyridine (tpy) derivative, 4′-(aminomethylphenyl)-2,2′:6′,2″-terpyridine (aptpy), has been reported for the ratiometric fluorescence recognition of PPi. When added with cadmium, the emission of aptpy at 358 nm was greatly enhanced and red shifted to 397 nm due to the complexation-induced ICT process, which then blue shifted to 349 nm upon the further addition of PPi. Based on the different response of dual fluorescence emissions at 349 and 397 nm, a ratiometric fluorescence method could be successfully established for the fluorescence recognition of PPi. With that, PPi could be successfully discriminated from other structurally similar anions, including nucleotide triphosphates.
We designed and synthesized a highly selective and sensitive fluorescent probe for hydrogen sulfide (H2S) based on the one step nucleophilic addition reaction between H2S and electron-poor C=C double bond. Our proposed probe displayed high selectivity for H2S over other analytes including cysteine (Cys) and glutathione (GSH), which might be because the steric hindrance of H2S is less than other thiols. Additionally, a linear relationship between fluorescence intensity and the concentrations of Na2S (0 – 450 μM) was obtained in an aqueous buffer solution (pH 7.4, 20 mM PBS). Particularly, we found that the adoption of the acetyl benzimidazole derivative as a recognition receptor to distinguish H2S from other thiols and analytes provides a promising methodology for the design of fluorescent probes for the determination of H2S.
Alpha-ketoglutaric acid (KG) and hydroxymethylfurfural (HMF) are currently being investigated in clinical trials as an approach in targeted cancer therapy. Hence, a method for the simultaneous determination of KG and HMF in plasma has been developed. Due to the strongly discriminative chemical properties of KG and HMF, SPE purification is performed using an ion-exchange cartridge to separate KG, and a hydrophobic polymeric cartridge to separate HMF. The cartridges are connected together for several steps, thus resulting in a quicker approach for the purification of plasma samples. The derivatization step is based on the reaction of the carbonyl groups of KG and HMF with dansylhydrazine (DNSH) catalyzed by trifluoroacetic acid. The formed derivatives could be separated by reversed-phase LC on a C8-column, and analyzed by UV and fluorescence detection in a single run using a gradient program. The obtained results show good reproducibility, specificity, and detection limits down to the low picomole range.
An ultra-performance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS) method was established for the simultaneous determination of residues of enilconazole, parconazole, thiabendazole and its metabolite, 5-hydroxythiabendazole, in chicken tissues including liver, muscle and egg. Homogenized samples were extracted by acetonitrile, concentrated and purified by an Oasis MCX solid-phase extraction cartridge. Analysis of the target drugs was performed by liquid chromatography with an UPLCTM BEH C18 column, coupled with a tandem mass spectrometry (UPLC-MS/MS) operating in the positive multiple-reaction mode (MRM). Good linearity was obtained at concentrations of 0.10 – 100 μg kg−1. The average recoveries of the analytes in chicken liver, muscle and egg at six fortification levels were in the range 93.6 – 119.5% with acceptable coefficients of variation (<14.8%). The detection capability (CCβ) of the analytes upon the method ranged from 0.05 to 138.1 μg kg−1. This method was successfully applied in screening and confirming of target drugs in tens of real samples.
This research investigated the ionizing radiation effect on thiamine hydrochloride (TH) and its usability as an irradiation dosimeter. The fundamental principle is to determine the concentration variations of TH solutions with high-performance liquid chromatography (HPLC) after exposing to γ-rays. The decreasing peak area of TH in the HPLC chromatogram forms a linear relationship with the rising radiation dose. We investigated the characteristics and suitable application range of the TH as a new radiation dosimeter. The influence factors and mechanism of the reaction induced by radiation were also discussed. According to the correlation between the concentration and the radiation dose, 0.3 g/L of a TH solution is suitable for the 0.1 – 10 kGy dose range, and 2 g/L is appropriate for 0.1 – 20 kGy. The easy availability and the simple, but stable, chemical structure of thiamine makes it a potential candidate for radiation dose research. Also, the preparation proceeding for sampling is easy, and the result can be automatic monitored by liquid chromatography.
A new and enzyme-free electrochemical immunoassay protocol was developed for the sensitive electronic monitoring of neuron-specific enolase (NSE) on a monoclonal mouse anti-human NSE antibody (mAb)-modified glassy carbon electrode, using guanine-decorated graphene nanostructures (GGN) as nanotags. To construct such an enzyme-free immunoassay format, guanine and polyclonal rabbit anti-human NSE antibody (pAb) were co-immobilized on the graphene nanostructures through the carbodiimide coupling. Based on a sandwich-type immunoassay mode, the assay was carried out in 0.1 M pH 7.4 PBS containing 5 μM Ru(bpy)32+ through the catalytic oxidation of Ru(bpy)32+ toward the guanine on the GGN. The presence of graphene nanostructures increased the immobilized amount of guanine, thus amplifying a detectable electronic signal. The covalent conjugation of guanine and pAb on the GGN resulted in a good repeatability and intermediate reproducibility down to 9.5%. Under optimal conditions, the dynamic concentration range of the developed immunoassay spanned from 0.005 to 80 ng mL−1 NSE with a detection limit of 1.0 pg mL−1 at the 3Sblank level. In addition, the methodology was evaluated by assaying the spiking serum samples, and the relative standard deviation (RSD) between the electrochemical immunoassay and a commercialized enzyme-linked immunosorbent assay (ELISA) were 2.8 – 7.0%.
A sexually transmitted disease is an illness that has a high probability of transmission between humans or animals who have sexual contact. Our research is based on the development of a microbiochip for Neisseria gonorrhoeae (N.G.). In our study, we have employed fusion technology between microarray technology and a microfluidic system for quantitative analysis of N.G. A great deal of attention has been focused on electrochemical detection by using a DNA probe, which is a specific DNA sequence and binds to a target biomolecule, because of high affinity, ease of usage, and fast measurement. The microbiochip consisted of two electrode systems and microchannel based PDMS. Our detection principles use electrochemical detection. Consequently, our microbiochip detected 5 ng/mL of N.G. and the correlation rate was over 0.95. We can produce a microbiochip, which could bind to a DNA probe and detect sample of interest. We expect that our electrobiochemical chip will be used for the development of a portable device.
The carbon, hydrogen, and nitrogen (CHN) contents of alanine and their uncertainties were estimated using a CHN analyzer and the certified reference material (CRM) L-alanine. The CHN contents and their uncertainties, as measured using the single-point calibration method, were 40.36 ± 0.20% for C, 7.86 ± 0.13% for H, and 15.66 ± 0.09% for N; the results obtained using the bracket calibration method were also comparable. The method described in this study is reasonable, convenient, and meets the general requirement of having uncertainties ≤ 0.4%.
We evaluated the capabilities of an in situ method for measuring copper isotopes of cubanite using UV-fs-LA-MC-ICP-MS. A comparison of the UV-fs laser results with those obtained from the NIR-fs laser system shows that there is obviously an improvement in the precision (<0.10‰, 2SE) when using the UV-fs laser. In both wavelength modes, matrix-matched standards are required for reliable in situ copper isotope analysis of cubanite. This method was applied to determinations for copper isotopes of minute cubanite grains in a skarn ore. Copper isotopic ratios of cubanite grains near a weathered surface of the sample are lower than those of intact cubanite grains within the sample, suggesting that selective leaching of heavier copper isotope in primary minerals occurred during weathering.
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.
Noncontact levitation in air of single micrometer-sized water droplets containing ammonium sulfate was successful by a laser trapping technique. The trapping laser beam was also used simultaneously as an excitation light source for the Raman spectroscopy of trapped droplets. Raman scattering of the symmetric stretching vibration of the SO42− anion and the OH stretching vibrations of H2O were observed at 980 and 3420 cm−1, respectively. The intensity ratio of these two Raman peaks was linearly proportional to the ammonium sulfate concentration in water. Therefore, the in situ quantification of ammonium sulfate in single aerosol droplets was achieved by means of laser trapping and Raman spectroscopy. To the best of our knowledge, this study is the first experimental observation of the independence of ammonium sulfate concentrations of aerosol water droplets to those of the mother solutions under constant relative humidity conditions.