Chromatography - LC-MS /Direct Mass Spectrometry-Molecular Weight Testing

Chromatography - LC-MS /Direct Mass Spectrometry-Molecular Weight Testing



Thermo Fisher Scientific (QE)



Thermo ScientificTM Q ExactiveTM high-performance benchtop quadrupole-orbitrap LC-MS/MS system is the first commercial combination of quadrupole precursor ion selectivity and high resolution accurate mass (HR/AM) OrbitrapTM mass analysis Chemical instruments, designed to provide highly reliable quantitative and qualitative (quan/qual) workflows.

The Q ExactiveTM mass spectrometer has an innovative HR/AM QuanfirmationTM function that can identify, quantify, and confirm more trace levels of metabolites, contaminants, peptides, and proteins in complex mixtures in a single analysis. Different from other technologies, this system can obtain extremely reliable analysis results without affecting the sensitivity of MS/MS, mass resolution or quantitative reproducibility.

The Q Exactive high-performance benchtop quadrupole-orbital trap LC-MS/MS system has the following significant innovative designs, greatly expanding the functions of the Thermo Scientific Exactive family Orbitrap system: Integrated quadrupole mass filter for precursor ion selectivity. Before the Orbitrap HR/AM detection, the MS/MS fragmentation process occurred in a higher energy collision-induced dissociation (HCD) pool;   

The new C-Trap ion optical system and HCD collision cell provide fast HCD MS/MS scanning and improve the transfer of low mass ions, thereby improving sensitivity and quantitative performance, especially suitable for experiments using isotope tags;   

Multiple detection improves the efficiency of the overall system work cycle, is more compatible with UHPLC, and collects and stores multiple precursor ions before Orbitrap performs simultaneous detection.

Test items:

  1. Drug analysis and pharmacokinetic studies;
  2. Analysis of environmental pollutants and their products;
  3. Natural product analysis;
  4. Unknown structure analysis
  5. Determination of protein molecular weight



  1. ESI/APCI source;
  2. Resolution: 140,000 FWHM (m/z≤200)
  3. Mass range 50-6000m/z
  4. High resolution mass spectrometry acquisition rate: up to 12Hz
  5. Super fast binary high pressure pump
  6. Diode array detector


Requirement on Sample

Liquid (above 1ml), solid (above 5mg)



How to pretreat LC-MS samples?

  1. The samples must not contain strong acids and bases. If they contain the above substances, they need to be processed to ensure that the batch pH is between 2 and 7.5. The sample must not contain sodium borohydride. For the sample of the system (such as sodium hydride) that will generate strong alkali after the addition of methanol, be sure to process it before sending the sample.
  2. If the system contains a large amount of inorganic salts, it needs to be treated to prevent the precipitation of inorganic salts and block the analytical column. At the same time, the presence of a large amount of inorganic salts can contaminate the ion source part of the mass spectrometer and even affect the signal of the sample.
  3. If some substances with strong mass spectrometry signal response are used in the reaction system, such as triethylamine, tetrabutylammonium bromide, triphenylphosphine oxide, etc., please deal with it before sending the sample to minimize the amount of such substances. Residues in the sample to avoid suppressing the mass spectrum signal of the target substance.
  4. For reaction systems using metal catalysts (such as palladium catalysts), be sure to process them before sending samples. Such metal catalysts are often easy to remain in the LCMS analysis system, and the mass spectrum signal is very strong, which will seriously affect the normal test of subsequent samples.
  5. Try to avoid solvents with strong ultraviolet absorption in the test sample, such as benzene, toluene, pyridine, etc.
  6. For the sample to monitor the reaction (such as the reaction solution or the reaction solution after extraction with ethyl acetate, dichloride, trichloride, and column with alkane solvent, etc.), take an appropriate amount and dilute it with methanol, acetonitrile, etc. to an appropriate concentration.
  7. The samples for delivery or purity determination should be dissolved in chromatographic grade methanol, acetonitrile, and water as much as possible; if the solubility of these solvents is not good, use a better soluble solvent to dissolve first and then use chromatographic methanol and acetonitrile to dilute to a suitable level. In addition, some shipment samples need to use 220nm, which can be dissolved in DMSO or DMF (the shipment samples should avoid solvents such as ethyl acetate and dichloride as much as possible), and then dilute to a suitable concentration with chromatographic methanol and acetonitrile. Because the peak retention time of these two solvents is short, they will not overlap with the sample peak. Please indicate the required solvent if the sample is solid.
  8. The tested sample or sample contains highly toxic substances or pungent odors. Please note that the experimenter must clearly label and inform the analyst so that protective measures can be taken.
  9. The sample must be filtered through a 0.22µm filter (the sample must be clear and free of floc after filtration), otherwise it will not be tested.

Are there any requirements for sample delivery and sample handling? 

  1. For the purified sample, it is best to remove the solvent, dip a small amount into the sample tube with the spotting capillary, and dilute it to 0.5mL, then filter it with a 0.22μm filter.
  2. For the reaction system sample, apply slightly on thin layer, the spots are very clear, indicating that the concentration is moderate. Take 0.2mL into the sample tube, dilute to 0.5mL, and filter with a 0.22μm filter.
  3. If you need to click multiple times to see on the thin layer, you need to increase it as appropriate.
  4. If the sample concentration is particularly small or particularly large, please indicate in advance. The reaction solution needs to use a 2ml centrifuge tube, do not use other centrifuge tubes or sample tubes. To choose a solvent that can completely dissolve the sample, the diluted sample needs to be clarified. Note if the concentration is too small or too large.

How to judge whether the sample can be used for LCMS

- You can query related literature or sample-related test information. General compounds, metabolites, and degradation products can all be tested.

Can LCMS perform quantitative experiments?

- Yes, standard products are required. LCMS quantification is more sensitive than general detection.