175results about How to "Low limit of quantitation" patented technology

This invention provides a method of nucleic acid analysis that enables highly accurate and sensitive quantitation by counting the number of molecules among a plurality of types of genes without amplifying specific genes and that enable reduction of quantitation limits. This method comprises steps of: allowing a polynucleotide comprising a first region having a sequence complementary to the target gene at the 3′ end, a second region having a sequence complementary to the target gene at the 5′ end, and a third region corresponding to a detection probe to hybridize to the target gene; allowing the 3′ end of the first region hybridized to the target gene to ligate to the 5′ end of the second region so as to obtain a circularized polynucleotide; with the use of the circularized polynucleotide as a template, performing a primer extension reaction using a primer having a sequence complementary to part of the circularized polynucleotide and a strand-displacement DNA polymerase; allowing a detection probe containing a sequence identical to the third region to hybridize to a sequence complementary to the third region that iteratively appears in a single-stranded portion of the extension product; and optically detecting the quantity of the detection probe hybridized to the extension product to thereby quantitate the target gene.

The invention relates to a method for detection of 25-hydroxyvitamin D in serum. The method comprises sample pretreatment: adding an acetonitrile solution containing a 25-hydroxyvitamin D internal standard substance into a serum sample, carrying out protein precipitation, carrying out centrifugation, taking the supernatant and diluting the supernatant through acetonitrile to obtain a sample to be detected, wherein a volume ratio of the serum sample to the acetonitrile solution is 1: 1-4 and a volume ratio of the supernatant to acetonitrile is 1: 1-4, and enrichment, separation and detection: carrying out enrichment, separation and detection on the sample to be detected through a two-dimensional liquid chromatography-tandem quadrupole mass spectrometer. The method is simple, greatly shortens the detection time, improves the detection flux of the sample and has a high detection precision, a low cost, specificity and strong matrix interference resistance.

The invention provides a method of measuring multiple preservative, sweetener and colorant in food at the same time. The method comprises the following steps of 1, weighing and taking 5-10 g of a sample and placing the sample into a color comparison tube of 50 ml, adding water and dissolving the sample, implementing ultrasonic extraction for 30 minutes, if the protein content is high, needing to add a protein precipitant to regulate the pH value to be neutral, adding water to implement constant volume, mixing evenly, and flowing through a microporous membrane of 0.45 micrometer for use; 2, taking a sample solution to implement liquid chromatographic analysis, and calculating and obtaining preservative, sweetener and colorant contents in the sample to be measured against a standard curve. According to the method of measuring multiple preservative, sweetener and colorant in food at the same time, multiple preservatives, sweeteners and colorants in food can be measured at the same time, the accuracy rate and recovery rate of measured samples are guaranteed, it is ensured that the relative standard deviation is in an allowable range, the applicable range of the method is also ensured, the experiment efficiency is improved, and the laboratory cost is saved.

The invention provides a high performance liquid chromatography-ultraviolet detection method for simultaneously detecting specific migration amounts of nine anti-oxidants in five food simulants. The method comprises immersing a sample to be measured in food simulants, carrying out cooling to a room temperature, carrying out uniform mixture, metering a volume of the water-based food simulants by a tris(2-carboxyethyl)phosphine hydrochloride-containing tetrahydrofuran mixed solution, carrying out filtration by a hydrophilic Teflon syringe filter, carrying out sample introduction, carrying out rotary distillation nitrogen-blowing condensation on the isooctane food simulants until basic drying, metering the volume by tris(2-carboxyethyl)phosphine hydrochloride-containing methanol, carrying out filtration by the hydrophilic Teflon syringe filter and carrying out sample introduction. C8 column gradient elution separation is used, detection wavelength is 285nm and a sample size is 20 microliters. The method has good chromatographic separation and linear relationship, has high recovery rate and high accuracy, has a quantification limit satisfying limitation requirements on the total migration amount of the nine anti-oxidants in the EU NO 10 / 2011 regulation and has been used for detection of a practical sample.

The invention discloses a method for measuring a volatile organic compound in a tobacco material. The method comprises the steps of using a headspace sampler and ion molecular reaction mass spectrometry (IMR-MS) in a combination way, collecting a volatile constituent in tobacco material paper (including cigarette paper, tipping paper, hard box package paper, soft box package paper, strip package paper, tobacco filter stick and filaments by a headspace sampler, analyzing by the IMR-MS, and achieving rapid and accurate measurement of the content of the volatile organic compound in the tobacco material by drawing a standard curve and by calculation. By the method, relatively-simple clean mass spectrum can be obtained, the qualitative and quantitative analysis of the volatile organic compoundis simplified, 19 types of volatile organic compound common in the tobacco material can be simultaneously, accurately and quantitatively detected, the advantage of rapid analysis is beneficial for achieving detection of a large amount of volatile samples, and the rapid analysis demand of a laboratory is satisfied.

The invention discloses an analytical method of gonyautoxins detected by combination of molecular imprinting solid phase extraction-hygroplasm, and belongs to the field of front treatment and chemical analysis and detection of a biological sample. The method applies a molecular imprinting polymer to structure a three-dimensional cavity and a specific recognition site which are highly similar as the imprinting molecule, so as to realize the selective recognition of the imprinting molecule, and improve efficiency of gathering target objects and removing interferent; moreover, an analytical method of hygroplasm combination detected target taking cyan column as a chromatograph column is developed; the cyan column has strong polarity in use of reverse phase, thus polarity target objects and impurities in the sample can be effectively separated; then better separating effect and mass spectrometric detection effect of gonyautoxins on the chromatographic column can be obtained according to the optimized hygroplasm condition. The method is featured by small sample demand, high recycle rate and precision, and low detection limit; the matrix effects in detection are reduced; the analytical method is applicable to the extraction and detection of multiple shellfish samples, and has very good universality.

The invention relates to the technical field of veterinary drug residue detection, in particular to a method for analyzing residual antibiotics in beef. The method at least comprises the steps that beef samples are subjected to pretreatment, extraction, purification and monitoring analysis, wherein the monitoring analysis is conducted by means of a chromatogram-mass spectrometry combined technology. In the extraction process, a surfactant is adopted for increasing a dissolution rate of the target antibiotics; in the purification process, a demulsifier is adopted for reducing an emulsificationrate of a system, matrices and other impurities are precipitated and removed, and the precision and sensitivity of the detection process are further improved.

The invention relates to a method of using a liquid chromatography tandem mass spectrometry for synchronously measuring four kinds of antibiotics in river sediment. The method of using the liquid chromatography tandem mass spectrometry for synchronously measuring the four kinds of antibiotics in the river sediment includes the following steps that 1, an experimental vessel is prepared; 2, the moisture content is measured; 3, vacuum freeze drying is conducted; 4, sequential extraction, grinding and sieving are conducted; 5, ultrasonic extraction and mechanical vibration are used for preparation; 6, double-column tandem solid-phase extraction is carried out, wherein before the solid-phase extraction, a buffer solution is added into an extraction solution subjected to rotary evaporation, then, ultrapure water is adopted to dilute a mixture, and the mixture is shaken to be fully uniform; 7, the extraction solution is purified and subjected to elution; 8, concentration and constant volume are conducted; 9, high-performance liquid chromatography is adopted to carry out synchronous computer measurement. By the adoption of the method of using the the liquid chromatography tandem mass spectrometry for synchronously measuring the four kinds of antibiotics in the river sediment, the purification and enrichment effects are greatly improved, 0.2% methanoic acid-2mmol / L ammonium acetate is used, acetonitrile and a citric acid buffer solution of which the pH value is 3 are used as the extraction solution of a solid sample, and optimal conditions are adopted to be configured and combined,so that a target analyte is better isolated, chromatographic peak area is larger, and the recovery rate is higher.

The invention provides a method for simultaneously separating and quantifying multiple components. The method comprises the steps of sample pretreatment and sample detection. The method provided by the invention has good specificity, and can avoid the interference of various components, especially components (such as polyethylene glycol and povidone) which are easy to interfere with each other, inmeasurement. The invention provides a good method for reverse engineering, component analysis, release detection of auxiliary materials and the like of pharmaceutical preparations and other products(such as cosmetics and foods). The method is simple to operate, good in specificity and accuracy, wide in linear range and high in sensitivity, and the detection capability and the detection efficiency are greatly improved.

The invention discloses a fluorescent quantitative PCR (polymerase chain reaction) detection kit for hepatitis B virus nucleic acid. The quantitative detection kit for the hepatitis B virus nucleic acid comprises primers and probes aiming at an S gene and / or a C gene, wherein the sequences of the primers are as shown in SEQ ID NO.1, SEQ ID NO.2, SEQ ID NO.3 and SEQ ID NO.4 in the specification, the sequences of the probes are as shown in SEQ ID NO.5 to SEQ ID NO.7 in the specification, and the three probes are respectively marked with fluorescence. The high-sensitivity quantitative detection kit for the hepatitis B virus nucleic acid has the advantages that HBV genome DNA molecules are detected, the quantitative range is wide, the sensitivity can reach 0.5 IU / ml of HBV DNA, the quantitative limit is as low as 2 IU / ml of HBV DNA, and the detection limit is as low as 1 IU / ml of HBV DNA; and in addition, a method and the kit are adopted, by means of the multi-functional utilization of theprimers and the probes at the nucleic acid invasion reaction stage, the complexity of the probe design and a detection system can be further reduced, and the economic cost of the probe design and thedetection system can be lowered.

The invention provides a high performance liquid chromatography detection method for anthocyanin in blueberries, and belongs to the technical field of photoelectrode materials. The anthocyanin comprises delphinidin-3-O-glucoside, cyanidin-3-O-glucoside, petunidin-3-O-glucoside, pelargonidin-3-O-glucoside, paeoniflorin 3-O-glucoside and malvidin 3-O-glucoside, wherein the flow rate of the high performance liquid chromatography is 0.8 mL / min, the detection wavelength is 520 nm, the detection temperature is 25 DEG C, the sample injection volume is 10 microliters, the detection time is 60 minutes, mobile phases: an aqueous phase B is a 0.3 wt% phosphoric acid aqueous solution, and an organic phase A is acetonitrile, and gradient elution. According to the present invention, the simultaneous determination of the six anthocyanins in the blueberry sample is achieved, the standard deviation of the peak area and the retention time is small, the detection limit and the quantification limit of the six anthocyanins are low, and the method has characteristics of high sensitivity, good precision, good reproducibility and good stability.