Mass Spectrometry Molecular Weight Determination
Mass spectrometry determination of molecular weight is a method based on the motion performance of sample molecules in an electromagnetic field to determine their relative molecular mass. Firstly, the sample is ionized into charged particles, which then move along different trajectories in the electromagnetic field. By measuring the flight time of particles in the electromagnetic field and correlating it with particle mass, the relative molecular mass can be determined. This method is of great value in analyzing complex mixtures, identifying unknown substances, determining molecular structure and conformation, gas analysis, isotope distribution, and other research areas.
In the application of mass spectrometry for molecular weight determination, accuracy and range are important considerations. The accuracy depends on factors such as the stability of the electromagnetic field, the stability of the ion source, and the sensitivity of the detector. The range is determined by the molecular mass of the sample. Generally speaking, the mass spectrometry method can measure a wide range of molecular weights, from tens of Daltons to millions of Daltons. However, for very large biomolecules such as proteins and nucleic acids, there may be certain difficulties in mass spectrometry determination of molecular weight.
Common Issues:
Q1. How to improve the accuracy of mass spectrometry in determining molecular weight?
A: Methods to improve measurement accuracy mainly include optimizing the stability of the electromagnetic field, enhancing the stability of the ion source, and improving the sensitivity of the detector. Additionally, thorough pretreatment of the sample, such as removing impurities, can also enhance measurement accuracy.
Q2. What techniques are used for mass spectrometry determination of large molecules?
A: For large molecule mass spectrometry, soft ionization techniques such as electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) are often employed. These techniques effectively convert large molecules into ions for mass spectrometry molecular weight determination, followed by detection using quadrupole or time-of-flight mass spectrometers.
Q3. How to use mass spectrometry to determine molecular weight for isomers?
A: For isomers, the molecular weight is the same, so mass spectrometry alone cannot distinguish them. In such cases, other analytical methods such as gas chromatography or liquid chromatography can be combined for two-dimensional or multi-dimensional analysis to distinguish isomers.
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