What is mass spectrometry? source of ion? Quality Analyzer?
Mass spectrometry is an analytical instrument for measuring ion mass-to-charge ratio (m/z). Mass spectrometry instruments are generally composed of sample introduction system, ion source, ion transport component, mass analyzer, detector, data processing system, etc. Shown.
The ion source is a component that converts the substance to be tested into charged ions. According to the ionization principle, it is divided into an atmospheric piezoelectric ionization spray ion source (ESI), an atmospheric piezoelectric ionization ionization ion source (APCI), and the like.
The mass analyzer is the core component of the mass spectrometer and can generate electric fields of different shapes. The electric fields generated by the ion source are used to separate the sample ions generated in the ion source by m/z. The mass analyzer is divided into a conventional resolution mass analyzer and a high resolution mass analyzer. A conventional resolution mass analyzer includes a quadrupole and an ion trap.
Figure 1 Spectrum schematic
What is a quadrupole mass analyzer for conjugate hyperboloids?
In the 1950s, German physicist Wolfgang Paul applied for patent 944,900 (1956) to point out that the electric field enclosed by four conjugated hyperboloids can screen ions. The quadrupole mass analyzer is divided into a cylindrical quadrupole and a conjugate hyperbolic quadrupole, as shown in Figure 2. The conjugated hyperboloid quadrupole is very demanding for the precision casting process and requires the use of a precision three-coordinate grinding machine. It also has high requirements for the alloy material of the cast quadrupole. Therefore, the material and processing cost are more than the cylindrical quadrupole. The pole is much taller. However, only a conjugated hyperboloid quadrupole can produce a textbook-like perfect theoretical electric field, while a cylindrical quadrupole produces a 1-2% deviation between the electric field and the theoretical electric field. The conjugate hyperbolic quadrupole is a variable resolution quadrupole mass analyzer, but the cylindrical quadrupole resolution is immutable.
Figure 2 conjugate hyperbolic quadrupole (Hyperquand) and conventional cylindrical rods (Round rods)
What is triple quadrupole mass spectrometry? SRM detection mode? H-SRM detection mode?
Triple quadrupole mass spectrometry is often abbreviated as QqQ, as shown in Figure 3. The first heavy Q1 and the third heavy Q3 are mass analyzers, and the second 90 degree curved quadrupole is a Q2 collision cell, 90 degrees. The curved collision cell is a design that reduces neutral noise. Currently, the collision cell of the high-end triple quadrupole mass spectrometer on the market adopts a curved structure. Triple quadrupole mass spectrometry is a classic set of tandem mass spectrometry for quantitative quantification. The most commonly used quantitative detection mode is SRM detection mode (select reaction detection scan mode). The principle is that Q1 selects a specific parent ion and sends it to the Q2 collision cell. Fragmentation, Q3 selects the parent ion-specific fragment ions into the detector. SRM is a detection mode that improves selectivity, improves detection signal-to-noise ratio (S/N), and improves sensitivity.
Figure 3 Schematic diagram of TSQ series triple quadrupole mass spectrometer
The conjugate hyperbolic quadrupole is a variable resolution quadrupole with a high resolution H-SRM detection mode (0.2FWMH) in addition to the traditional SRM detection mode (0.7 FWMH), as shown in Figure 4. In the detection of dicyandiamide residues in milk powder, there is interference in the matrix (m/z is 85.7), which is very close to the dicyandiamide (m/z 85.3). If the traditional SRM detection mode is adopted, Q1 resolution At 0.7, Q1 cannot distinguish between m/z 85.3 and 85.7, that is, it is impossible to distinguish between interference and dicyandiamide, and a chromatogram with severe matrix interference can not be used for quantitative qualitative detection; when using H-SRM detection mode, improve Q1 resolution to 0.2, Q1 can easily distinguish m / z 85.3 and 85.7, that is, can distinguish between interference and dicyandiamide, can get a qualified for quantitative qualitative detection chromatogram. Samples using the same pre-treatment method only use the H-SRM detection mode to improve the sensitivity of the instrument by increasing the selectivity, significantly reducing the noise, and improving the signal-to-noise ratio. As shown in Figure 5, the same pretreatment method is used to detect pesticide residues in complex matrix samples, which has unique advantages when tested using H-SRM mode.
Figure 4 Conjugate hyperbolism quad with traditional SRM detection mode and H-SRM detection mode for improved resolution
Figure 5 Unique advantages of H-SRM detection mode for detecting complex matrix samples
What is Orbitrap ? Q Exactive ?
Orbitrap is an ultra-high resolution mass analyzer and is unique to Thermo Scientific's patented high resolution mass spectrometry technology, as shown in Figure 6. Orbitrap is a high-resolution mass spectrometry technology that is completely innovative after the high-resolution mass spectrometry technology such as magnetic mass spectrometer mass spectrometer, time-of-flight mass analyzer (ToF), and Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR). Many shortcomings of previous high resolution mass spectrometry. Orbitrap is an epoch-making high-resolution mass spectrometry technology!
In 1998, Makarov invented the highly-intelligent mass spectrometer Orbitrap, which was completely innovative in principle. In 2005, Orbitrap was first commercialized in the world. In 2011, Thermofisher Scientific released the world's first quadrupole-electrostatic field orbitrap hybrid mass spectrometer Q Exactive. Q Exactive is a liquid-mass spectrometer based on Orbitrap technology with ultra-high resolution, ultra-high quality accuracy, ultra-high sensitivity, and the ability to quantify high-end triple quadrupoles.
Figure 6 Schematic diagram of high-resolution mass spectrometry Orbitrap (electrostatic field orbitrap)
What can Q Exactive do in food and agricultural product testing ?
As a high-resolution mass spectrometer, Q Exactive is widely used in the screening of unknowns and dangerous substances in food and agricultural products, such as pesticide residues, veterinary drug residues, biotoxin residues and other organic pollutants to ensure the safety of food and agricultural products. In addition, Q Exactive has the quantitative ability of high-end triple quadrupoles, high-resolution quantification of target analytes in complex matrix samples, and a new trend in high-resolution mass spectrometry for food and agricultural product testing.
The RNA purification kit is used to purify and recover RNA molecules transcribed in vitro and total RNA extracted from various materials, which can effectively remove contaminating impurities in RNA samples. The recovery rate of this product can reach 80%, and the OD260/OD280 ratio of the obtained RNA is generally about 2.0, which can be directly used in subsequent sensitive experiments (such as microarray analysis, fluorescence RT-PCR, etc.). With the deepening of transcriptomics, the complexity of RNA types, expression regulation and functions is far beyond our imagination.
Removing ribosomal RNAs that account for more than 80% helps to focus sequencing on less abundant but informative RNAs. At present, the removal of rRNA is mainly through the combined use of probe and RNase H. The processed RNA will be mixed with many digestion products, enzymes and ions, which is not conducive to the subsequent construction of RNA library. Take the Columnar RNA Purification Kit as an example. Trizol is a ready-to-use reagent that can be used to purify total RNA from tissues and cells. This is a single-phase solution of phenol and guanidine isothiocyanate that facilitates lysis of tissues and cells, inhibiting RNases to maintain RNA integrity.
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