Willoughbydriscoll7840

This work presents a lab-made automatic flow-batch system for headspace single-drop microextraction and on-drop conductometric sensing ammonium. Sample and NaOH solution are simultaneously pumped into a reaction chamber (RC), where ammonium is converted to ammonia by raising pH. The converted ammonia then diffuses into the headspace of the RC, and reacts with a 100 mM boric acid drop. The conductivity of the drop is measured by an on-drop conductivity probe, which is made by two stainless-steel contacting electrodes. The result shows that the increasing rate of conductivity has a linear relationship to the ammonium concentration in sample (R2 = 0.9945). This method has a linear range up to 400 μM, a limit of detection 2.8 μM, a relative standard deviation of 3.0% (200 μM, n = 10) and carryover coefficient 0.028. Measurements of river waters, lake waters and wastewaters have been demonstrated. The recoveries have achieved from 99.0 to 114%. This method avoids using of harmful or odorous reagents and follows the concept of green chemistry.A facile MALDI-TOF mass spectrometric platform for quantitative analysis of protein biomarkers was developed based on magnetic ZnFe2O4 nanoparticles and mass tagging signal amplification. In this platform, magnetic ZnFe2O4 nanoparticles functionalized with an aptamer of the biomarker of interest was used to magnetically separate silica nanoparticles modified with another aptamer of the target biomarker and a barcoding peptide from solution phase in the presence of the biomarker of interest. After the silica nanoparticles were dissolved by KHF2, the released barcoding peptide was detected by MALDI-TOF mass spectrometry with magnetic ZnFe2O4 nanoparticles used as assisting matrix of laser desorption ionization. Since the mass spectral intensity of the barcoding peptide is directly related to the concentration of the target biomarker, the proposed platform can be applied to the quantification of the target biomarker in complex biological samples. The effectiveness of the proposed platform was tested on the detection of carcinoembryonic antigen (CEA) in serum. Experimental results revealed that the proposed platform could achieve quite reliable quantitative results for CEA in human serum samples with accuracy comparable to a commercial CEA ELISA Kit. Its limit of detection and limit of quantification for CEA were estimated to be 0.6 × 10-3 and 1.8 × 10-3 ng/mL, respectively, considerably lower than the corresponding values reported in literature. Due to its features of simplicity in design, extremely low background signal, high sensitivity and selectivity, the proposed method can be further developed to be a competitive alternative for the quantification of CEA and other protein biomarkers as well.An innovative electrochemical sensor for paracetamol (PCM) determination was fabricated by electropolymerization imprinting on three-dimension (3D) AuPd nanoparticles‒ionic liquid (IL) functionalized graphene‒carbon nanotubes nanocomposite (AuPd/GN-CNTs-IL) modified glassy carbon electrode. The GN-CNTs supported AuPd alloy nanoparticles were prepared via one-pot hydrothermal method in the presence of IL (i.e. this website 1-hydroxyethyl-3-methyl imidazolium bis[(trifluoromethyl) sulfonyl] imide), which not only promoted the formation of small AuPd alloy nanoparticles, but also acted as "spacer" to prevent the π-π stacking and aggregation of graphene sheets and carbon nanotubes. The resulting composite had large surface area and high electrocatalysis. The PCM imprinted poly(carbazole-co-pyrrole) exhibited good recognition to PCM and had high stability. Based on the synergic effect of PCM imprinted copolymer and 3D AuPd/GN-CNTs-IL nanocomposite, a highly selective and sensitive electrochemical sensor was established. It presented a good linear relationship from 0.10 to 10 μM with a low limit of detection of 50 nM (S/N = 3). The sensor could be applied to the detection of PCM in biological samples, with acceptable recoveries (84.5%-102%). In addition, it was successfully used to monitor the concentration of PCM in urine from a patient with fever cold.The integration of gel-based loop-mediated isothermal amplification (gLAMP) and finger-actuated microfluidic chip (μFAchip) was developed for the simultaneous detection of various different types of bacterial pathogens. The developed μFAchip consisted of three PDMS layers attached together by two adhesive tapes. Multiple chambers in the top PDMS layer were used for sample preparation, and the corresponding chambers in the bottom PDMS layer was used for long-term storage of LAMP reagents without DNA templates. The thin PDMS layer in the middle contained cross-shaped cuts as finger-actuated valves for fluid control. To reduce operation steps on the chip, such as pipetting and manipulation of samples, Whatman CloneSaver card was pre-embedded in the top chambers for on-chip DNA extraction and purification. Upon a simple press on the top layer, the finger-actuated valve was opened up, allowing DNA samples on the top layer flow into the bottom reaction chambers for gLAMP reaction. For POCT applications, on-chip LAMP reaction and imaging were conducted on a miniaturized peltier heater and a portable fluorescence imaging system respectively. Under the optimized condition, multiple pathogens were detected simultaneously with high selectivity and sensitivity (as low as 1.6 cells). The developed μFAchip provided a rapid and easy-to-operate platform for gLAMP-based pathogen detection, with the potential for in-field detection, especially in areas with limited resources.In this study, a novel of magnetic molecularly imprinted polymers (Fe3O4/GO/DMIPs) with multi-targets recognizing function were prepared by surface molecular imprinting technique adopting isoprenaline as the dummy-template molecule and graphene oxide (GO) as the carrier. The morphology, structures and magnetic properties of nanosorbents were characterized and assessed in detail and the results indicated that the 3D recognition cavities and matching functional groups with catecholamine neurotransmitters (CNs) were successfully fabricated on Fe3O4/GO surface. Moreover, the kinetic, isothermal and selective adsorption experiments were conducted to further reveal the adsorption behavior of adsorbent toward CNs and the results showed that the Fe3O4/GO/DMIPs possessed high adsorption capacity, rapid binding rate and excellent selectivity for CNs. On this basis, the Fe3O4/GO/DMIPs were further applied as adsorbent of magnetic solid-phase extraction (MSPE) for selective recognition and separation of CNs (dopamine, epinephrine, norepinephrine) followed by UPLC-MS/MS detection. The crucial parameters affecting the extraction efficiency were systematically optimized by Box-Behnken statistical design. Under the optimum conditions, satisfactory linearity (r > 0.99) was obtained with the lower limit of quantification from 0.53 to 1.93 ng mL-1. The accuracy (RE) ranged from -7.6% to 6.4% and the intra- and inter-day precisions were not more than 8.7% and 10.2%, respectively. Hence, the strategy proposed in this study might be used for high selectivity recognition and determination of CNs in complex biological matrices, which would provide a basis and reference for its application in the fields of separation and clinical monitoring.Phycotoxins in the marine food-web represent a serious threat to human health. Consumption of contaminated shellfish and/or finfish poses risk to consumer safety several cases of toxins-related seafood poisoning have been recorded so far worldwide. Cyclic imines are emerging lipophilic toxins, which have been detected in shellfish from different European countries. Currently, they are not regulated due to the lack of toxicological comprehensive data and hence the European Food Safety Authority has required more scientific efforts before establishing a maximum permitted level in seafood. In this work, a novel data dependent liquid chromatography - high resolution mass spectrometry (LC-HRMS) approach has been successfully applied and combined with targeted studies for an in-depth investigation of the metabolic profile of shellfish samples. The proposed analytical methodology has allowed i) to discover a plethora of unknown fatty acid esters of gymnodimines and ii) to conceive a brand new MS-based strategy, termed as backward analysis, for discovery and identification of new analogues. In particular, the implemented analytical workflow has broadened the structural diversity of cyclic imine family through the inclusion of five new congeners, namely gymnodimine -F, -G, -H, -I and -J. In addition, gymnodimine A (376.5 μg/kg), 13-desmethyl spirolide C (11.0-29.0 μg/kg) and pinnatoxin G (3.1-7.7 μg/kg) have been detected in shellfish from different sites of the Mediterranean basin (Tunisia and Italy) and the Atlantic coast of Spain, with the confirmation of the first finding of pinnatoxin G in mussels harvested in Sardinia (Tyrrhenian Sea, Italy).In contrast to most of essential and heavy metals, mercury levels in seaweed are very low, and pre-concentration methods are required for an adequate total mercury determination and mercury speciation in this foodstuff. An ionic imprinted polymer-based solid phase extraction (on column) pre-concentration procedure has been optimized for mercury species enrichment before liquid chromatography hyphenated with inductively coupled plasma mass spectrometry determination. The polymer has been synthesized by the precipitation polymerization method and using a ternary pre-polymerization mixture containing the template (methylmercury), a non-vinylated monomer (phenobarbital), and a vinylated monomer (methacrylic acid). Factors affecting the adsorption/desorption of Hg species (extract pH, loading and elution flow rates, volume of eluent, etc.), and parameters such as breakthrough volume and reusability, were fully studied. Mercury species were first isolated from seaweed by ultrasound assisted extraction using a 0.1% (v/v) HCl, 0.12% (w/v) l-cysteine, 0.1% (v/v) mercaptoethanol solution. Under optimized conditions, the limits of detection were 0.007 and 0.02 μg kg-1 dw for methylmercury and Hg(II), respectively. The pre-concentration factor (volume of 10 mL of seaweed extract) was 50. Repeatability and reproducibility of the method were satisfactory with relative standard deviations lower than 16%. The proposed methodology was finally applied for the selective pre-concentration and determination of methylmercury and Hg (II) in a BCR-463 certified reference material and in several edible seaweeds.A novel smartphone-assisted portable biosensor based on laccase-mineral hybrid microflowers (La-HMFs) was applied for real-time, accurate and reliable quantification of epinephrine (EP). La-HMFs with flower-like hierarchical nanostructure was synthesized via biomineralization using Cu3(PO4)2⋅3H2O as the mineral. Characterization results revealed laccase molecules as the framework were immobilized within La-HMFs. Smartphone-assisted colorimetric assays showed wide linear detection range (1-400 μM) and favorable anti-interference ability for EP detection, and the detection limit was 0.6 μM. Further, due to the protective effect of Cu3(PO4)2⋅3H2O, the immobilized laccase exhibited good stability and desirable reusability.