Disclosed herein is a method for selectively reducing, using electrical energy, CO.sub.2 to carbon monoxide, a catalyst for use in the method, and an electrochemical reduction system. The method for producing carbon monoxide by electrochemically reducing carbon dioxide of the present invention includes (a) reacting carbon dioxide with a metal complex represented by formula (1), and (b) applying a voltage to a reaction product of the carbon dioxide and the metal complex represented by formula (1):

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The present invention refers to a mixture of positional isomers of aminaphtone, to an aminaphtone product comprising said mixture and to a new method of high-performance liquid chromatography (HPLC) useful for the characterization of aminaphtone. The method allows to identify in the positional isomers of which the aminaphtone in a product containing them, and can be used to choose lots of aminaphtone suitable for pharmaceutical use.

A method for simultaneously determining fat-soluble vitamins and carotenoids in serum, and belonging to the technical field of analytical chemistry, includes an ionic liquid (IL) or a binary mixed solvent composed of an IL and another solvent is adopted as an extractant; the biological samples are pre-treated by liquid-liquid extraction (LLE) and then detected by high-performance liquid chromatography (HPLC); retinyl acetate and trans-β-apo-8′-carotenal are adopted as the internal standards for fat-soluble vitamins and carotenoids, respectively; and the internal standard method is adopted to establish standard curves for quantification based on the retention time and the UV-Vis absorption spectrum. Compared with the existing methods, in the disclosure, the pretreatment process is simple and easy to be conducted, the sample can be prepared in a short time, and the toxic and harmful organic solvent is used at a reduced amount.

A method for determining a grade of black tea by HPLC detection belongs to the field of tea grade determination. The specific steps are as follows: adding known black tea powder samples of different grades into boiling water of 95-100° C. for extraction, and filtering with a filter membrane with a pore size in a range of 0.20-0.25 μm to obtain black tea sample liquid; measuring contents of ten components by peak area normalization method; standardizing data of the contents of the ten components in a black tea sample solution; carrying out unsupervised principal component analysis; carrying out supervised partial least squares discriminant analysis; carrying out hierarchical clustering analysis on the basis of partial least squares discriminant analysis, and finally establishing a tea grade discrimination model based on HPLC. The method is simple, accurate and efficient, and whose effectiveness is not affected by the variety of black tea.

The disclosure provides a thermal desorption (TD) tube sampler. The sampler comprises a first connector configured to reversibly connect to a TD tube containing a sample, and a second connector configured to couple to a direct injection mass spectrometer. The TD tube sampler is configured to desorb a sample in a TD tube connected thereto, and feed the desorbed sample from the TD tube to a direct injection mass spectrometer such that the desorbed sample does not pass through a cold trap.

A mixed-mode chromatography method for the determination of phosphorylated sugars in a sample is provided. The mixed-mode chromatography method includes obtaining a sample comprising at least one phosphorylated sugar. The sample is introduced onto a chromatography system. The chromatography system includes a column having a stationary phase material contained inside the column. The stationary phase material has a surface comprising a hydrophobic surface group and at least one ionizable modifier. The sample with a mobile phase eluent is flowed through the column, where the at least one phosphorylated sugar is substantially resolved and retained within seven minutes. The mobile phase eluent includes water with an additive and acetonitrile with the additive. The mobile phase eluent has a pH less than 6. The at least one phosphorylated sugar is detected using a detector.

The present invention discloses a method for judgment of cheddar cheese grade based on identification characteristic flavor compounds, comprising the following steps: selecting cheddar cheese of different grades as standard product, and extracting volatile flavor compounds from the standard product; using gas phase-sniffing device to screen out characteristic flavor compounds with higher flavor intensity from the volatile flavor compounds through aroma extract dilution analysis; proceeding with clustering of characteristic flavor compounds as screened out to obtain identification characteristic flavor compounds of cheddar cheese; measuring the concentration of identification characteristic flavor composition of cheddar cheese of known grade, and establish the training set for training of support vector machine; measuring the concentration of identification characteristic flavor composition of cheddar cheese to be tested, and inputting it into the support vector machine trained to judge the grade of cheddar cheese to be tested. The present invention aims to obtain the model of identification characteristic flavor compounds of cheddar cheese through statistical analysis, which is available for accurate judgment of cheddar cheese quality grade on this basis.

The disclosure relates to a reversed-phase chromatography method for the determination of at least one of glyphosate or AMPA in a sample. The method includes obtaining the sample comprising the at least one of glyphosate or AMPA in a sample matrix and introducing the sample to a reversed-phase chromatography system. The reversed-phase chromatography system includes a reversed-phase column having a stationary phase material contained inside the column. The stationary phase material includes a phenyl functional group. The method also includes flowing the sample with a mobile phase eluent through the reversed-phase column, wherein the at least one of glyphosate or AMPA is substantially resolved and retained. The mobile phase eluent has a pH between about 1.5 to about 2.5. The at least one of glyphosate or AMPA are detected using a detector.

A volatile organic compound collector can include a collector material configured to collect volatile organic compounds given off from a patient's skin; a wrapping configured to isolate the collector material from an external environment; a heater comprising a heating element, the heating element configured to emit a thermal pulse to desorb the volatile organic compounds from the collector material; and a mesh layer configured to prevent the collector material from contacting the patient's skin, wherein the collector material is received between the wrapping and the mesh layer.

The following six methods included in a method package for hazardous substances in fiber products is stored beforehand in a method storage section (26): simultaneous analysis method for specific aromatic amines, simultaneous analysis method for the first group of azo dyes, simultaneous analysis method for the second group of azo dyes, simultaneous analysis method for PFCs, simultaneous analysis method for AP, and simultaneous analysis method for APEO. Each analysis method includes analysis conditions and parameters which are suitable for a simultaneous analysis of a specific category of hazardous substances, e.g. azo dyes. An analysis condition setter (25) lists the six analysis methods on a display unit (28), from which an operator selects one analysis method to be executed. The operator also prepares mobile phases and a column specified for each analysis method. An LC controller (23) and an MS controller (24) control each relevant section of the system according to the analysis conditions and parameters described in the selected analysis method, to analyze a sample prepared from a fiber product. By this analysis, a test for major hazardous substances in the fiber product can be performed. A test for a specific hazardous substance which the operator desires to detect can also be easily and efficiently performed.