Simulation and Optimization of Distillation Processes for Separating the Methanol–Chlorobenzene Mixture with Separate Heat-Pump Distillation

The methanol–chlorobenzene mixture has a larger relative volatility in the low composition range than in the high composition range. Based on this characteristic, the mixture can be effectively separated by separate heat-pump distillation (SHPD) with significant energy savings. The binary interaction parameters of the UNIQUAC equation were used to predict the vapor–liquid equilibrium by means of the binary interaction parameters included in the Aspen Plus database. To minimize the overall annual operating costs, simulations for SHPD were carried out using Aspen Plus software, including the RadFrac and Compr blocks, and the optimal operating conditions, such as the split-point concentration, were determined. Simulations for conventional distillation, conventional heat-pump distillation, and multieffect distillation processes were also carried out for comparison. The simulated results showed that the SHPD process has obvious advantages over the other distillation processes in the assessment of energy savings and overall economic efficiency

Simulation and Optimization of Distillation Processes for Separating a Close-Boiling Mixture of <i>n</i>‑Butanol and Isobutanol

Separation of close-boiling mixtures by conventional distillation consumes a large amount of energy because of the very high reflux ratio required. Mechanical vapor recompression heat pumps (MVRHPs) can recycle the energy of the vapor and can thus be used in such distillation processes to save energy. Three different distillation schemes, namely, conventional distillation, top MVRHP distillation, and bottom-flashing MVRHP distillation, were simulated for the separation of the close-boiling mixture of <i>n</i>-butanol and isobutanol using Aspen Plus to determine the economically best option. The research results indicate that, compared to conventional distillation, the energy savings for bottom-flashing MVRHP distillation and top MVRHP distillation can reach 67.92% and 72.92%, respectively, and the TACs correspondingly decrease by 71.74% and 75.57%

ICPMS-Based Specific Quantification of Phosphotyrosine: A Gallium-Tagging and Tyrosine-Phosphatase Mediated Strategy

Low-abundance tyrosine phosphorylation is crucial to not only normal but also aberrant life processes. We designed and synthesized a photocleavable magnetic nanoparticle-based gallium tag for tagging and enrichment as well as UV-release of the phosphate-bearing molecules/ions in cells. HPLC/⁷¹Ga species-unspecific isotope dilution (⁷¹Ga-SUID) ICPMS was subsequently developed for specific and absolute quantification of phosphotyrosine (<b>pY</b>) under the assistance of a protein tyrosine phosphatase-1B (PTP-1B). <b>pY</b> quantification was thus achieved via determination of Ga in the Ga-phosphate complexes that come exclusively from the Ga-tagged <b>pY</b>. In this way, the method detection limit of <b>pY</b> reached down to 30 amol with the RSD lower than 5.70% (<i>n</i> = 5 at pmol level). Feasibility of this proposed method was validated using VNQI­GTLSE­<b>pY</b>IK, VNQI­GTL<b>pS</b>E­<b>pY</b>IK, and extracellular regulated protein kinase 1 peptide (-<b>pT</b>E<b>pY</b>-) standards with the recovery of more than 96% (<i>n</i> = 5). It was applied to the absolute quantification of <b>pY</b> in human breast cancer MCF-7 cells, indicating that <b>pY</b> increased by 1.60 nmol (61.1%) in 3.0 × 10⁶ MCF-7 cells after 100 nM insulin stimulation. We believe that, not limited to <b>pY</b> quantification, this element-tagging and protease-specific reaction mediated ICPMS methodology will pave a simple path for ever more applications of ICPMS to the studies of quantitative protein post-translational modifications (PTMs) when suitable element-tags are designed and specific proteases are available toward targeted PTMs

Monitoring the adulteration of milk with melamine: a visualised sensor array approach

<div><p>Melamine, a toxic triazine, is illegally used as an additive in milk to apparently increase the amount of protein, causing acute renal failure in thousands of Chinese infants. In this study, a rapid, simple, sensitive and selective colourimetric sensor array is reported as a potential screening tool for monitoring the adulteration of raw milk with melamine. Using chemically responsive dyes (mainly porphyrins and pH indicators) as the recognition elements, determination of melamine at different concentrations (0.1, 0.5, 1.0, 1.5 and 2.0 mg kg⁻¹) and a detection limit of 0.1 mg kg⁻¹ were achieved because of diverse and strong molecular interactions. Furthermore, the colourimetric sensor array was successfully able to discriminate between melamine and its analogues. The unique “fingerprint” of melamine was obtained with a novel signal processing method named “two-step subtraction”, which made it possible for the detection results to be easily observed with the naked eye even without any statistical analysis. In addition, the process including sample pre-treatment and detection process took only 12 min at room temperature. The merits (such as simplicity, rapidity, low cost, visual colourimetry, sensitivity and selectivity) make the proposed method especially useful for on-site screening of melamine levels in milk.</p></div

Evaluation of BDE-47 Hydroxylation Metabolic Pathways Based on a Strong Electron-Withdrawing Pentafluorobenzoyl Derivatization Gas Chromatography/Electron Capture Negative Ionization Quadrupole Mass Spectrometry

Understanding the metabolic pathways of polybrominated diphenyl ethers (PBDEs) is a key issue in the evaluation of their cytotoxicity after they enter the biota. In order to obtain more information concerning the metabolic pathways of PBDEs, we developed a strong electron-withdrawing pentafluorobenzoyl (PFBoyl) derivatization capillary gas chromatography/electron capture negative ionization quadrupole mass spectrometry (GC/ECNI-<i>q</i>MS). PFBoyl esterification greatly improves separation of the metabolites of PBDEs such as hydroxylated PBDEs (OH-PBDEs) and bromophenols (BPs) metabolites in rat liver microsomes (RLMs). On the other hand, the strong electron-withdrawing property of PFBoyl derivatized on OH-PBDEs and/or BPs makes cleavage of the ester bond on ECNI easier resulting in higher abundance of the structure-informative characteristic fragment ions at a high <i>m</i>/<i>z</i> region, which facilitate the identification of OH-PBDEs metabolites. Subsequent quantification can be performed by monitoring not only ⁷⁹Br^– (or ⁸¹Br^–) but also their characteristic fragment ions, achieving more accurate isotope dilution quantification using GC/ECNI-<i>q</i>MS. These merits allow us to identify totally 12 metabolites of BDE-47, a typical example of PBDEs, in the RLMs <i>in vitro</i> incubation systems. In addition to the already known metabolites of BDE-47, one dihydroxylated 3,6-di-OH-BDE-47 and one dihydroxylated 3,5-di-OH-tetrabrominated dioxin were found. Moreover, the second hydroxylation took place on the same bromophenyl ring, where the first hydroxyl group was located, and was further confirmed via the identification of the dihydroxylated 2′,6′-di-OH-BDE-28 of an asymmetric 2′-OH-BDE-28. This methodological development and its subsequent findings of the metabolic pathways of BDE-47 provided experimental evidence for understanding its dioxin-like behavior and endocrine disrupting risk

Real-Time Imaging of Mitochondrial Hydrogen Peroxide and pH Fluctuations in Living Cells Using a Fluorescent Nanosensor

Mitochondrial reactive oxygen species (ROS) and pH fluctuations are closely correlated with mitochondrial dysfunctions, which are implicated in various human diseases including neurodegenerative disorders and cancers. Simultaneously monitoring the changes of ROS and pH of mitochondria remains a major challenge in the mitochondrial biology. In this study, we develop a novel mitochondria-targeted fluorescent nanosensor for real-time imaging of the fluctuations of hydrogen peroxide (H₂O₂) and pH in living cells. The fluorescence probes for detecting pH and H₂O₂ were loaded in the small-sized mesoporous silica nanoparticles (MSN). Then the polyethylenimine was attached to cap the pores of MSN, the triphenylphosphonium was further modified to target mitochondria in living cells. Confocal fluorescence imaging indicated that the nanosensor could effectively target mitochondria and successfully achieved real-time imaging of mitochondrial H₂O₂ and pH fluctuations in living cells. Notably, this is a single nanosensing system that is capable of visualizing multiple subcellular analytes at the same time and position by multicolor fluorescence imaging. The current approach can provide a promising tool to investigate the interplaying roles of various subcellular analytes in living cells

Nanosemiconductor-Based Photocatalytic Vapor Generation Systems for Subsequent Selenium Determination and Speciation with Atomic Fluorescence Spectrometry and Inductively Coupled Plasma Mass Spectrometry

We reported novel Ag–TiO₂- and ZrO₂-based photocatalytic vapor generation (PCVG) systems as effective sample introduction techniques for further improving the sensitivity of the atomic spectrometric determination of selenium for the first time, in which the conduction band electron served as a “reductant” to reduce selenium species including Se^VI and convert them directly into volatile H₂Se, which was easily separated from the sample matrix and underwent more effectively subsequent atomization and/or ionization. These two PCVG systems helped us to overcome the problem encountered in the most conventional KBH₄/OH^––H⁺ system, in that Se^VI was hardly converted into volatile selenium species without the aid of prereduction procedures. The limits of detection (LODs) (3σ) of the four most typical Se^IV, Se^VI, selenocystine ((SeCys)₂), and selenomethionine (SeMet) species were, respectively, down to 1.2, 1.8, 7.4, and 0.9 ng mL^–1 in UV/Ag–TiO₂–HCOOH, and 0.7, 1.0, 4.2, and 0.5 ng mL^–1 in UV/ZrO₂–HCOOH with the relative standard deviations (RSDs) lower than 5.1% (<i>n</i> = 9 at 1 μg mL^–1) when using atomic fluorescence spectrometry (AFS) under flow injection mode. They reached 10, 14, 18, and 8 pg mL^–1 in UV/Ag–TiO₂–HCOOH, and 6, 7, 10, and 5 pg mL^–1 in UV/ZrO₂–HCOOH with the RSDs lower than 4.4% (<i>n</i> = 9 at 10 ng mL^–1) when using inductively coupled plasma mass spectrometry (ICPMS). After the two PCVG systems were validated using certified reference materials GBW­(E)­080395 and SELM-1, they were applied to determine the total Se in the selenium-enriched yeast sample and used as interfaces between high-performance liquid chromatography (HPLC) and AFS or ICPMS for selenium speciation in the water- and/or enzyme-extractable fractions of the selenium-enriched yeast

Zero-Interfacing μHPLC to ICPMS

The chromatography–mass spectrometry hyphenated technique is the most widely adopted tool for quantifying trace analytes in a complex biosample. One issue we frequently encountered, however, is that the separated analyte-containing chromatographic peaks broaden and even remix prior to mass spectrometric quantification due to the inevitable molecular diffusion within the dead-volume introduced by hyphenation. We developed a zero-interfacing approach for coupling microbore (μ) HPLC with inductively coupled plasma mass spectrometry (ICPMS). Zero-interfacing μHPLC to ICPMS has been achieved by a column-nebulizer assembly (COL-NEB) of a self-designed glass framework with a tapered nozzle, in which a capillary chromatographic column can be harbored while an Ar gas flow is blown through the nozzle mouth. The COL-NEB can be positioned just before the base of the Ar-ICP serving as the central sampling channel of a conventional Ar-ICP torch for online nebulization and transportation of the analytes separated on μHPLC into ICPMS, maintaining the molecular resolution obtained on μHPLC and the limit of detection (LOD) of ICPMS. For example, the full width at half-maximum of a SLUGT peptide chromatographic peak was reduced to 1.71 ± 0.07 s (n = 5) with a 0.72 fg LOD (3σ) of 80Se. Moreover, at least 32 Se-containing peptides were determined in the trypsin lysate of the water-soluble fraction (≥3000 MW) from Se-enriched yeast CRM SELM-1 within a 10 min run, the highest record to date. We believe such an approach paves the way to determining accurate information on a heteroatom and its binding biomolecules that play key roles during life processes

Conversion of Inhibition Biosensing to Substrate-Like Biosensing for Quinalphos Selective Detection

Since all of the organophosphorus pesticides (OPP) inhibit the cholinesterases with a common mechanism, it is still challenging to detect OPP selectively with inhibition-based biosensors. This study focuses on the conversion of a typical inhibition biosensing to a selective substrate-like biosensing. The interaction of quinalphos with plant-esterase involves not only a decrease in enzyme activity but also a heterolytic bond cleavage of quinalphos. The leaving group eliminated from quinalphos is an ideal biomarker due to its specificity in most OPP. Thus, using 2-hydroxyquinoxaline (HQO), the leaving group of quinalphos, as the biomarker and <i>meso</i>-tetra (4-sulfonatophenyl) porphine (TPPS₄) as an optical probe, quinalphos can be selectively detected. The molecular recognition between TPPS₄ and HQO leads to a considerable sensitivity of the detection. The spectral responses of TPPS₄ show a linear dependence on quinalphos concentration in the presence of plant-esterase within the 0.01–1 mg kg^–1 range. The detection limit is 0.01 mg kg^–1, well below the maximum residue limits (MRLs) defined by European Union (0.05 mg kg^–1) and China (0.2 mg kg^–1)

Single-Probe-Based Colorimetric and Photothermal Dual-Mode Identification of Multiple Bacteria

Effective identification of multiple pathogenic bacteria in unknown samples is important for disease prevention and control but remains a challenge yet. A single-mode array-based sensing approach is simple and sensitive, but it usually relies on the use of multiple cross-reactive receptors to construct sensor arrays, which is cumbersome and insufficiently accurate. Here, we developed a sensor array with colorimetric and photothermal dual mode of differentiating multiple pathogenic bacteria. The sensor array was based on boronic acid-functionalized Au–Fe3O4 nanoparticles (BA–GMNPs), which not only possess localized surface plasmon resonance properties, showing a burgundy color similar to that of AuNPs, but also exhibit mild superparamagnetism, allowing for the differentiation of bacteria before and after binding to the nanoparticles. Immobilization of BA–GMNPs on the bacterial cell surface by covalent bonding would diminish NaCl-induced assembly of BA–GMNPs. Different BA–GMNPs@bacterial complexes differed in their ability to resist assembly and produced different colorimetric and photothermal response signals. A unique molecular fingerprint of each bacterium was obtained by linear discriminant analysis of the response patterns, demonstrating an effective differentiation among the six species studied. Compared with single-mode sensing arrays based on multiple receptors, this method only requires the preparation of a single nanomaterial, which produces two signal outputs for the identification of multiple bacteria with better differentiation. It can distinguish not only multiple pathogenic bacteria but also Gram-negative and Gram-positive bacteria, and, more importantly, it can perform preliminary discrimination of unknown samples