What is the difference between a mass spectrometer and a gas phase?

This ......Much worse? Generally speaking, when the method is stable, the difference should not be exceeded, and the difference is generally too much. If there are too many checks, one is to redo it, then make a standard sample, and then make a sample, which does not rule out the instability of the instrument, operation errors and other reasons.

If you didn't get these two stitches in one day, then don't ask. Experiments that have to be done in a day are counted. Because maybe the carrier gas flow has changed or something).

Mass spectrometry is different from the principle of gas phase detection, mass spectrometry is based on the different nucleus-to-mass ratio and molecular weight of different substances, separated in the electromagnetic field, which can more accurately detect the molecular weight of the detected substance or its group, and identify each substance through different molecular weights, while in the gas phase, no matter what detector it is, only reflects the corresponding value of the detected substance in the detector, and the purpose is only to separate the substances and cannot play a role in identification.

Mass spectrometry MS

Principle of analysis: Molecules are bombarded by electrons in a vacuum, forming ions, passing through an electromagnetic field.

Separate by different mE.

Spectra are represented in the form of a bar plot of the relative kurtosis of the ions.

Change with mE.

Information provided: Mass of molecular ions and fragment ions.

and its relative kurtosis, providing information on molecular weight, elemental composition and structure GC

Principle of analysis: The components in the sample are separated between the mobile phase (gas) and the stationary phase due to different partition coefficients.

Spectral representation: information provided by the change of post-column effluent concentration with retention value: the retention value of the peak is related to the thermodynamic parameters of the component and is a qualitative basis; Peak area is related to component content.

The liquid chromatograph is based on the classical liquid column chromatograph, introduces the theory of gas chromatograph, and technically adopts high-pressure infusion pump, stationary phase, gradient elution technology and high-sensitivity detector, which has the characteristics of high pressure, high speed, high sensitivity, high selectivity and wide application range.

2. The main differences between liquid chromatography and gas chromatograph:

1. Analyze the difference between objects

1) Analytical object of gas chromatograph:

1) Samples that can be gasified, have good thermal stability and low boiling point.

2) High boiling point, poor volatility, poor thermal stability, ionic type and polymer samples cannot be detected.

3) It only accounts for about 15% of organic matter.

2) Analytical object of liquid chromatograph:

1) A sample that can be dissolved to make a solution.

2) It is not limited by the volatility and thermal stability of the sample.

3) Large molecular weight, difficult to gasify, poor thermal stability, polymer and ionic samples can be detected.

4) It is widely used, accounting for about 80% and 85% of organic matter.

2. Difference in mobile phase:

1) Mobile phase of the gas chromatograph:

1) The mobile phase is an inert gas.

2) There is no affinity between the component and the mobile phase, and only acts with the stationary phase.

2) Mobile phase of the liquid chromatograph:

1) The mobile phase is liquid.

2) There is an affinity between the mobile phase and the components, which adds a factor to the selectivity of the column and improves the resolution, which plays a great role in the separation.

3) There are many types of mobile phases, and there is a large room for choice.

4) The choice of mobile phase polarity and pH value plays an important role in the separation.

5) The selectivity of separation can be increased by using two or more liquids in different proportions as mobile phases.

3. Differences in operating conditions

1) Operating conditions of gas chromatograph: Heated operation.

2) Operating conditions of liquid chromatograph: room temperature, high pressure (high viscosity of liquid).

Instruments for separating and detecting different isotopes. The main device of the instrument is placed in a vacuum. The substance is vaporized and ionized into an ion beam, which is accelerated and focused by voltage.

Then, through the magnetic field electric field region, ions of different masses are deflected differently by the magnetic field electric field and focused at different positions, so as to obtain mass spectra of different isotopes. The mass spectrometry method was first established by Thomson in 1913 and later adopted.

Aston et al. improved and perfected. Modern mass spectrometers have been continuously improved to still use the principle of electromagnetics to separate ion beams according to the charge-to-mass ratio. The performance indicator of a mass spectrometer is its resolution, which is defined as m δm if the mass spectrometer is able to resolve masses m and m δm.

Modern mass spectrometers have a resolution of up to:

Measuring atomic mass to 7 decimal places.

The most important application of mass spectrometry is the separation of isotopes and the determination of their atomic mass and relative abundance. The accuracy of the determination of atomic mass exceeds that of chemical measurement methods, and the exact mass of about 2 3 more atoms is determined by mass spectrometry methods. Due to the equivalence relationship between mass and energy, knowledge of nuclear structure and nuclear binding energy can be obtained.

The geological age of the ore can be determined by the analytical measurement of the radioactive decay product elements that can be extracted from the ore. Mass spectrometry methods can also be used for organic chemical analysis, especially trace impurity analysis, to measure the molecular weight of molecules, providing a reliable basis for determining the molecular formula and molecular structure of compounds. Due to the unique mass spectrometry of the compound with eggplant dust like a fingerprint, mass spectrometers are also widely used in industrial production.

Solid spark source mass spectrometry: Laughing beam impurity analysis of high-purity materials. It can be applied to semiconductor materials, non-ferrous metals, and building materials departments; Gas isotope mass spectrometry:

The determination of stable isotopes C, H, N, O, S and radioisotopes RB, SR, U, PB, K, AR can be applied to geology, petroleum, medicine, environmental protection, agriculture and other departments.

The principle of mass spectrometer is to bombard a sample molecule with a stream of high-energy electrons, etc., so that the molecule loses electrons and becomes positively charged molecular ions and fragment ions. These different ions have different masses, and the ions of different masses reach the detector at different times under the action of the magnetic field, and the result is a mass spectrum.

Mass spectrometers have an ion source, a mass analyzer, and an ion detector at their core. An ion source is a device that ionizes the molecules of a specimen under high vacuum. The ionized molecule receives too much energy and further fragments into a variety of fragment ions and neutral particles with smaller masses.

They enter the mass analyzer by acquiring the average kinetic energy with the same energy under the action of an accelerating electric field. A mass analyzer is a device that separates ions of different masses that enter it at the same time according to the mass-to-charge ratio m e size.

The separated ions enter the ion detector in turn, collect the amplified ion signal, and process it by computer to draw a mass spectrum. There are many types of ion sources, mass analyzers, and ion detectors. Mass spectrometers are divided into isotope mass spectrometers, inorganic mass spectrometers and organic mass spectrometers according to their application ranges; According to the resolution ability, it is divided into high-resolution, medium-resolution and low-resolution mass spectrometers; According to the working principle, it is divided into static instruments and dynamic instruments.