Low Organic Solvent Content Research Articles

Stimuli-responsive aggregation-induced emission of molecular probes by electrostatic and hydrophobic interactions: Effect of organic solvent content and application for probing of alkaline phosphatase activity

We suggest that aggregation-induced emission (AIE) molecular probes with single charged/reactive group can exist in the formation of nanostructures but not monomers at extremely low organic solvent content. The nanoaggregates show good dispersivity and emit week emission. Stimuli-responsive assembly of nanoaggregates by electrostatic interactions can turn on the fluorescence, facilitating the design of biosensors with single-charged molecular probes as the AIE fluorogens. To prove the concept, tetraphenylethene-substituted pyridinium salt (TPE-Py) was used as the AIE fluorogen for probing of alkaline phosphatase (ALP) activity with pyrophosphate ion (PPi) as the enzyme substrate. The dynamic light scattering and transmission electron microscope experiments demonstrated that TPE-Py probes existed in aqueous solution at nanometer size and morphology. Stimuli such as the negatively charged PPi, citrate, ATP, ADP, NADP and DNA could trigger the aggregation of the positively charged TPE-Py nanoparticles, thus enhancing the fluorescence via AIE effect. ALP-enzymatic hydrolysis of PPi into two phosphate ions (Pi) limited the aggregation of TPE-Py nanoparticles. The strategy was used for the assay of ALP with a low detection limit (1 U/L) and wide linear range (1–200 U/L). We also investigated the effect of organic solvent content on the AIE process and found that high concentration of organic solvent can prevent the hydrophobic interaction between AIE molecules but show no essential influence on the electrostatic interaction-mediated assembly. The work should be evaluable for understanding AIE phenomenon and developing novel, simple and sensitive biosensors using a molecular probe with single charged/reactive group as the signal reporter.

Study of Sirolimus Adsorption and Preparation of Its Samples in Methanol, Acetonitrile and Their Mixtures with Water for HPLC–MS/MS Analysis

The paper discusses some of the problems associated with the preparation and reversed-phase HPLC analysis of sirolimus samples in mixtures of water with methanol or acetonitrile with different content of the latter. It was shown that when the sirolimus samples were evaporated to dryness in polypropylene tubes, almost quantitative irreversible adsorption of the substance occurred. The loss of sirolimus can be avoided by using glass tubes for sample preparation when a complete removal of a solvent is necessary. Preparation of sirolimus samples in water–methanol or water-acetonitrile mixtures can lead to a gradual adsorption of the substance on the walls of a glass vial in case of a low organic solvent content. It was shown that a reconstitution solution containing about 50% of an organic solvent should be used to analyze sirolimus by the RP-HPLC method, since the analysis of samples dissolved in pure acetonitrile or methanol is limited by the amount of sample injected due to broadening or distortion of the chromatographic peak.

Post-Column Make-Up Flow (PCMF) Enhances the Performance of Capillary-Flow PGC-LC-MS/MS-Based Glycomics.

Deep characterization of biologically relevant glycans remains challenging. Porous graphitized carbon-liquid chromatography tandem mass spectrometry (PGC-LC-MS/MS) enables the quantitative elucidation of glycan fine structures. However, the early PGC-LC elution of smaller glycans (tri-, tetra-, and pentasaccharides) at low organic solvent content hampers their detection. In efforts to improve the glycan profiling sensitivity and accuracy, we present a new capillary-flow PGC-LC-MS/MS-based configuration comprising a post-column make-up flow (PCMF) that supplies an ion-promoting organic solvent to separated glycans prior to their detection by MS. The analytical performance of this setup was systematically evaluated against our existing capillary-flow PGC-LC-MS/MS platform (Jensen et al., Nat. Protoc. 2012, 7, 1299). Specifically, the ion intensities and signal-to-noise ratios of various classes of nonderivatized glycans from N- and O-glycoproteins and fructooligosaccharide mixtures were compared using methanol (MeOH)-, isopropanol (IPA)-, and acetonitrile (ACN)-based PCMF at various concentrations. In particular, ACN- and IPA-based PCMF dramatically increased the signal response across all glycan types (30- to 100-fold), improved the MS/MS spectral quality, and reduced the quantitative glycoprofile variation between replicates. In particular, the detection of the early eluting glycans benefitted from the PCMF. The highest sensitivity gains were achieved with the supplements of 100% ACN and IPA (equating to 57% (v/v) net concentration at the ion source) while neither compromising the favorable PGC-LC properties including the high peak capacity and glycan isomer separation nor changing the MS detection behavior. In conclusion, PCMF-based PGC-LC-MS/MS dramatically improves the glycomics sensitivity, coverage, and quantitative accuracy not least for the difficult-to-detect early eluting and low-abundance glycans detached from N- and O-glycoproteins.

Fabrication of Novel Avermectin Nanoemulsion Using a Polyurethane Emulsifier with Cleavable Disulfide Bonds.

In this study, a polyurethane emulsifer with various functional groups was prepared from isophorone diisocyanate, avermectin, 2,2-dimethylol propionic acid, and bis(2-hydroxyethyl) disulfide. The chemical structure of the polymer was confirmed by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, and element analysis. The polymer exhibited adequate emulsification ability for avermectin after neutralization with triethylamine. A satisfaying nanoemulsion was obtained, in which avermectin was encapsulated in nanoparticles with 50 wt % drug loading, low organic solvent content, and high stability under dilution and centrifuging treatment in addition to low surface tension, high affinity to crop leaf, and improved avermectin photostability. The resulting nanoparticles showed degradability in the presence of dl-dithiothreitol or inside the insect as a result of the disulfide bonds, promoting the release of avermectin. As a result, the avermectin nanoparticles showed higher insecticidal ability compared to both the avermectin nanoparticles without a disulfide group and the avermectin emulsifiable concentrate.

A Simple Method for Automated Solid Phase Extraction of Water Samples for Immunological Analysis of Small Pollutants.

A new method for solid phase extraction (SPE) of environmental water samples is proposed. The developed prototype is cost-efficient and user friendly, and enables to perform rapid, automated and simple SPE. The pre-concentrated solution is compatible with analysis by immunoassay, with a low organic solvent content. A method is described for the extraction and pre-concentration of natural hormone 17β-estradiol in 100 ml water samples. Reverse phase SPE is performed with octadecyl-silica sorbent and elution is done with 200 µl of methanol 50% v/v. Eluent is diluted by adding di-water to lower the amount of methanol. After preparing manually the SPE column, the overall procedure is performed automatically within 1 hr. At the end of the process, estradiol concentration is measured by using a commercial enzyme-linked immune-sorbent assay (ELISA). 100-fold pre-concentration is achieved and the methanol content in only 10% v/v. Full recoveries of the molecule are achieved with 1 ng/L spiked de-ionized and synthetic sea water samples.

Viscosity Coefficients of KCl, NaCl, NaI, KNO3, LiNO3, NaBPh4 and Bu4NI in Water - Dimethyl Sulfoxide Binary Mixtures With a Low Organic Solvent Content

Viscosity Coefficients of KCl, NaCl, NaI, KNO3, LiNO3, NaBPh4 and Bu4NI in Water - Dimethyl Sulfoxide Binary Mixtures With a Low Organic Solvent Content

Implementation of gradients of organic solvent in micellar liquid chromatography using DryLab®: Separation of basic compounds in urine samples

In micellar liquid chromatography (MLC), chromatographic peaks are more evenly distributed compared to conventional reversed-phase liquid chromatography (RPLC). This is the reason that most procedures are implemented using isocratic elution. However, gradient elution may be still useful in MLC to analyse mixtures of compounds within a wide range of polarities, decreasing the analysis time. Also, it benefits the determination of moderately to low polar compounds in physiological fluids performing direct injection: an initial micellar eluent with a low organic solvent content, or a pure micellar (without surfactant) solution, will provide better protection of the column against the proteins in the physiological fluid, and once the proteins are swept away, the elution strength can be increased using a positive linear gradient of organic solvent to reduce the analysis time. This work aims to encourage analysts to implement gradients of organic solvent in MLC, which is rather simple and allows rapid analytical procedures without pre-treatment or the need of re-equilibration. The implementation of gradient elution is illustrated through the separation of eight basic compounds (β-blockers) in urine samples directly injected into the chromatograph, the most hydrophobic showing large retention in both conventional RPLC and MLC. The use of the DryLab® software to optimise gradients of organic solvent with eluents containing a fixed amount of surfactant above the critical micellar concentration is shown to provide satisfactory predictions, and can facilitate greatly the implementation of gradient protocols.

A facile and efficient strategy to enhance hydrophilicity of zwitterionic sulfoalkylbetaine type monoliths

In order to prepare zwitterionic HILIC monolithic columns with high polarity, the highly hydrophilic monomer N,N-dimethyl-N-acryloyloxyethyl-N-(3-sulfopropyl)ammonium betaine (SPDA) and crosslinker N,N′-methylenebisacrylamide (MBA) were employed for developing a novel sulfoalkylbetaine type stationary phase. The polymerization parameters were systematically optimized in order to obtain a satisfactory performance for column permeability, mechanical stability, hydrophilicity, efficiency and selectivity. Compared to the previously reported poly(N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl)ammonium betaine-co-ethylene dimethacrylate) (poly(SPE-co-EDMA)) monolith and the poly(SPDA-co-EDMA) monolith that we developed, a significantly enhanced hydrophilicity was obtained on the poly(SPDA-co-MBA) monolithic column, illustrated by the lowered critical composition of the mobile phase corresponding to the transition from the HILIC to the RP mode. Excellent permeability, reproducibility and stability were achieved on this optimized poly(SPDA-co-MBA) monolith. A column efficiency of 70,000plates/m was obtained for the analysis of bases at a linear velocity of 1.95mm/s. As expected, by studying the influence of mobile phase pH and salt concentration on their retention, a weak electrostatic repulsion interaction for negatively charged analytes was also observed at low organic solvent content on the poly(SPDA-co-MBA) monolithic column. The final optimized poly(SPDA-co-MBA) monolith exhibited good selectivity for a series of polar compounds, such as phenols, bases, benzoic acid derivatives, small peptides, urea and allantoin.

Novel zwitterionic polyphosphorylcholine monolithic column for hydrophilic interaction chromatography

A novel porous zwitterionic monolith was prepared by thermal co-polymerisation of 2-methacryloyloxyethyl phosphorylcholine (MPC) and ethylene glycol dimethacrylate (EDMA) within 100 μm I.D. capillaries. Mercury intrusion porosimetry, scanning electron microscopy (SEM), micro-HPLC (μ-HPLC), elemental analysis and ζ-potential analysis were used to evaluate the monolithic structure. No evidence of swelling or shrinking of the monolith in different polarity solvents was observed. A typical hydrophilic liquid chromatography (HILIC) mechanism was observed at high organic solvent content (acetonitrile >60%). The phosphorylcholine (PC) functionality has both a positively charged quaternary ammonium and a negatively charged phosphate group. For charged analytes, a weak electrostatic interaction was also observed by studying the influence of mobile phase pH and salt concentration on their retentions on the poly(MPC- co-EDMA) monolithic column. The optimised poly(MPC- co-EDMA) monolith showed very good selectivities for a range of polar test analytes, especially small peptides. This might be ascribed to the good biocompatibility of PC functionality. At low organic solvent content, baseline separation was also observed for a test mixture of seven alkylphenones by a reversed-phase separation mechanism.

Adsorption behavior of a teicoplanin aglycone bonded stationary phase under harsh overload conditions

Silica-bonded teicoplanin aglycone allows enantioseparation of amino acids by reversed-phase liquid chromatography with a low organic solvent content. However, a reversible change in the adsorption behavior leading to a retention time shift (RTS) was observed when a preparative scale column was treated with harsh preparative chromatography-like conditions between finite-injection HPLC runs conducted under exactly the same conditions. This behavior was observed for all five investigated aliphatic and aromatic amino acids. In all cases, the retention times were prolonged after the overload conditions and the RTS was more pronounced for the later eluting d-enantiomer. We defined a standardized method for measuring the RTS and performed a systematic investigation on the influence of experimental conditions (type and concentration of pH modifier and organic modifier, temperature, pH) on the RTS. In this way a solvent composition – 90/10 50 mM NH 4Ac pH 5.8/MeOH – was identified that yielded no observable shift in retention time after overload conditions for both enantiomers. In order to treat the observed phenomenon on a mechanistic level, we applied band profile analysis based on the stochastic theory of chromatography and identified two different enantioselective sites. When the band profile analysis was performed on elution profiles obtained from runs with prolonged retention time after harsh overload conditions, the retention time shift could be attributed to both differentiable types of adsorption sites. One site was found to make both, enantioselective and non-selective contributions.

ROMP-Based, Highly Hydrophilic Poly(7-oxanorborn-2-ene-5,6-dicarboxylic acid)-Coated Silica for Analytical and Preparative Scale High-Performance Ion Chromatography

Homopolymers of 7-oxanorborn-2-ene-5,6-dicarboxylic anhydride (ONDCA) and norborn-2-ene (NBE), respectively, as well as copolymers of ONDCA and NBE with well-defined block sizes and molecular weights have been prepared by ring-opening metathesis polymerization (ROMP) using initiators of the type Cl2Ru(PR3)2(CHAr‘) (R = phenyl, cyclohexyl, Ar‘ = C6H5, p-F−C6H5). Despite the fact that ONDCA is not initiated stoichiometrically by the initiators employed, the block-copolymers are well-defined in the case where the polymerization is started with NBE. The linear polymers and copolymers were coated onto various vinylsilanized silica materials and subsequently cross-linked employing azobis(isobutyronitrile) (AIBN). The influence of particle size, pore diameter and volume, the specific surface of the inorganic carrier, the influence of the block sizes, and the amounts of coating on the chemical stability of the resulting materials as well as on the separation efficiency and selectivity have been studied. The high hydrophilicity of any ONDCA-containing polymer or copolymer ensures a strong interaction of the mobile phase with the material even in the case of a low organic solvent content (<2%). The high selectivity of the stationary phases is demonstrated by fast baseline separations (6−10 min) of various isomeric anilines and lutidines as well as hydroxyquinolines. The complementary use of apolar, NBE-based coatings and highly polar, pure ONDCA-based coatings allows an in depth discussion of the separation mechanism. Tests designed to detect underivatized, accessible surface silanol groups (Engelhardt test) confirmed the quantitative coating of the surface, which also accounts for the significantly elevated pH stability compared to standard silica materials.

Water protection of wooden window joinery painted with low organic solvent content paints with known composition. Part 1. Results of inter-laboratory tests

An investigation of the water protection capacity of modern paints with low organic solvent content was carried out as part of an European research project. The wider scope of the project was to establish the performance and durability of these new coatings applied to window joinery made from European softwood species. The aim of the moisture studies was to employ well-proven methods to determine the liquid water absorption of the coatings. A range of standard moisture permeability tests, carried out on coating systems applied to pine and spruce substrates, indicated a high correlation between similar data obtained using different techniques at different laboratories. The results showed that permeability of the coatings tested did not depend on the timber substrate, as long as the permeability was expressed in absolute terms and not relative to the absorption of uncoated wood. The results from this study will be used to determine whether laboratory measurements of the moisture transmission properties of a coating can be used to predict outdoor weathering performance.