Burnettevest4117

ere confirmed by HPLC analysis, which underscores the utility of this portable photometer for the on-site monitoring of paraquat in water samples.This paper reports on the development of an extraction method called "ultrasound-assisted dispersive liquid antisolvent precipitation (UA-DLAP)". The developed method is a combination of dispersive liquid-liquid microextraction (DLLME) and liquid antisolvent precipitation (LAP) methods. Unlike DLLME, the extraction solvent in UA-DLAP is replaced with a bad solvent for the analyte which has a low affinity toward the analyte (antisolvent). Unlike LAP, in UA-DLAP the analyte is dissolved in water, the antisolvent is water-immiscible and denser than water, and the needed volume of the antisolvent is in microliter range. In UA-DLAP, after the addition of a mixture of the antisolvent and a disperser solvent to the sample solution under sonication, a cloudy mixture containing the antisolvent micro/nanodroplets appears. After centrifugation of the mixture, three phases appear (a water-rich phase in the top, an analyte rich precipitate phase in middle, and an antisolvent rich phase in the bottom). Finally, the analyte rich precipitate phase is separated and dissolved in a back-extraction solvent. To evaluate the efficiency of the UA-DLAP method and its possible mechanism of action, three model polar organic compounds in water were extracted by UA-DLAP and determined spectrophotometrically. The results showed that the precipitate phase for all of the investigated analytes was nanostructured. The limits of detection were 22 ng mL-1, 11 ng mL-1, and 3.9 ng mL-1 for doxorubicin, methylene blue, and Congo red, respectively. Respective experimental enrichment factors were 18.3, 27.8, and 31.1.In this article, we report a simple approach to stacking micro- and nanoparticle zones by electrokinetically migrating them through moderately confined channels of uniform cross-section. Experiments show the reported pre-concentration process to initiate at the tail end of the zone following its electrokinetic injection, with the stacked region migrating faster than the rest of the sample band. This effect causes the particles traveling in front to merge into the stacked region making it grow both in size and concentration. Because the stacked zone also gradually loses particles from its trailing edge, it eventually disintegrates upon running out of particles at its front end. Nevertheless, enhancements in peak height by over 100-fold were recorded using the reported approach for polystyrene beads with diameters comparable to the channel depth. This enhancement however, exhibited a temporal variation as the particle band migrated through the analysis column reaching a maximum value that depended on the particle diameter, particle concentration, channel depth, electric field strength, electroosmotic mobility, etc. Interestingly, the peak area recorded by the detector remained relatively constant during this particle migration period allowing reliable sample quantitation. Moreover, upon incubating antibody-coated particles against an antigen sample, the peak area for the particle zone was seen to scale linearly with the antigen concentration establishing the utility of the reported focusing phenomenon for chemical/biochemical analysis. The noted stacking technique was further applied to enabling UV absorbance detection of particle zones on microchips which then allowed us to determine the colloidal content in actual natural water samples. .In this study, boron-doped diamond (BDD) electrodes with varied B contents are prepared to determine the feasibility of the direct usage of BDD as an electrochemical biosensor without any modification. The electrochemical performance of the electrodes was investigated through the characterization of electrochemical impedance spectroscopy for potassium ferricyanide/potassium ferrocyanide (K3Fe(CN)6/K4Fe(CN)6) redox couples, as well as through qualitative and quantitative analysis of the two biomolecules dopamine (DA) and melatonin (MLT). The results show that the B content of BDD is the primary parameter for controlling the electrocatalytic current, that is, the response sensitivity. However, the abundant crystal planes and low background current are the key factors in improving the selectivity of the biomarkers to identify multiple analytes. Considering the catalytic current and its ability to distinguish the biomolecules, BDD with a B source carrier gas flow rate of 18 sccm is used as the sensing electrode for the simultaneous detection of DA and MLT. The response peak potential difference reaches 500 mV, and the linear concentration range for the two analytes is 0.4-600 μM, with detection limits of 0.1 μM for DA and 0.003 μM for MLT. These results match those observed for electrochemical sensors modified by various sensitive materials. BDD electrodes show good chemical resistance, good stability, and no pollution and are suitable for long-term usage as biomarker sensors.Alkaline phosphatase (ALP), which converts the phosphate group (-PO4) in the substrate to the hydroxyl group (-OH), is a useful tool in the biological analysis, a good indicator of dissolved inorganic phosphorus levels and an important biomarker for several diseases. In conventional designs for ALP detection, both the interferent with a -PO4 and the target with a -OH will go into the sensing path and give out the undesired background and the desired signal respectively. This limited the sensitivity of the method and required the complicated design to achieve a satisfying limit of detection (LOD) of ALP. Here, we provided a new sensing strategy for ALP detection design. Ebselen order We designed a path-choice-based biosensor with two DNA tracks in which ALP works as the switch to guide the reaction path of lambda exonuclease (λ exo). The path-choice character enlarged the difference between signal and background by separating the interferent removing path and the target sensing path. The substrate preference of ALP and λ exo was studied to optimize the structure of DNA tracks. The path-choice-based biosensor achieved simple, fast (30 min), sensitive (LOD 0.014 U L-1) and selective detection of the activity of ALP. The method has been applied to detect the activity of ALP in cell lysates, which shows the potential application in ALP-related biological research.The detection of a small number of exosomes provides the possibility for early cancer diagnosis and prognosis. Here, a multi-signal amplified electrochemical sensing platform was explored for the ultrasensitive detection of tumor exosomes relying on catalytic hairpin assembly-triggered DNA walker, entropy beacon-based DNA assembly and Ag@C core-shell nanocomposites. In this work, the utilization of Ag@C nanocomposites as electrode interface effectively enhanced functional active sites and electron transfer capability. By designing a target-assisted entropy beacon-based DNA assembly, single exosome initiated the release of multiple special DNA sequences, which could be separated conveniently by magnet and then hybridize with the blocking DNA to liberate swing arm. DNA walker was activated with the assistance of catalytic hairpin assembly, introducing extensive electroactive methylene blue (MB) to electrode surface. Thus, the detection of exosomes was transferred into the measurement of the MB current, with a good liner range from 100 to 75 000 particles/μL. Furthermore, this constructed sensing system displayed acceptable reproducibility, long-term stability, favorable selectivity, and highlighting application potential in real samples.This study reports on the development of a novel instrument for capillary electrophoresis (CE) coupled with laser induced fluorescence (LIF) detection that is inspired by the Lego-toy concept. The Lego CE-LIF design is an evolution of purpose-made CE instrumentation, allowing the users to construct their own analytical device with a high degree of standardization (i.e. a "standard" setup) without requirement of mechanical and electronic workshop facilities. To allow instrument reproduction outside the original fabrication laboratory, which is not trivial for in-house-built CE systems, the new design is based on unprecedent 'plugging' hyphenation of various off-the-shelf parts available for microfluidics, optics and electrophoresis. To render the operation with Lego CE-LIF optimal, we developed a new background electrolyte (BGE), using for the first time extremely high concentrations of zwitterionic and large weakly charged species for much improvement of detection sensitivity. The Lego CE-LIF was demonstrated for separation and detection of oligosaccharides labelled with 8-aminopyrene-1,3,6-trisulfonic acid (APTS). The new gel-free BGE for oligosaccharide analysis also allowed simplification of the conventional CE-LIF protocol used with commercial instruments while keeping satisfactory separation performances. Furthermore, the new BGE is fully compatible with a non-thermostatted Lego CE instrument thanks to low current and therefore low heat generation under application of a high voltage.Polyamines (such as spermine, spermidine) play important roles in biomedical and food field. The elevated polyamines have been proposed to serve as target analytes for monitoring meat spoilage. Because of structural similarity and low concentration of polyamines in real samples, it is exceedingly challenging to design and develop sensitive probes for visual detection of polyamines. To address this issue, a highly efficient probe was reported based on a newly developed chromophore reaction between lactam-fused aza-BODIPY (abbreviation LAB) and polyamines by virtue of unique multiple amino groups character of polyamines. This chromophore reaction includes a kinetic-controllable reaction of a B-N bond cleavage by polyamines followed by a fast hydrolysis reaction to yield much smaller conjugated molecules. With 130 nm hypsochromic shift of the absorption peak and up to 99% fluorescence quenching within 1 min, LAB can be used as a highly sensitive fluorescent probe for detection of polyamines solution and monitoring fish spoilage with synchronous colorimetric and fluorescent changes.Colorimetric sandwich-type biosensors that can both provide sensitivity competitive with fluorescence-based approaches, and leverage reagents that are cost-effective, widely available and as safe as possible, are highly sought after. Herein, we demonstrate an alternative highly-sensitive colorimetric method for paper-based sandwich-type biosensing that uses starch-iodide complexation to simplify practical biosensing using ubiquitous reagents. Targeting the mycotoxin ochratoxin A (OTA), a covalently-immobilised OTA antibody on a cellulose surface captures OTA and forms a sandwich with OTA aptamer-conjugated glucose oxidase. Adding the chromogenic reagents at an optimized concentration, a distinct blue color develops within 30 min, offering excellent contrast with the clear/white of the negative sample. With a sampling volume down to just 5 μL, the assay exhibits concentration limits of detection and quantitation of 20 and 320 pg mL-1, respectively, and a linear range from 10-1 to 105 ng mL-1 (R2 = 0.997). The method displays excellent selectivity against related mycotoxins, excellent %recovery (95-117%) and robust operation in complex matrices (beer, urine and human serum), with no significant difference versus gold-standard liquid chromatography.