1. Open the mass spectrometry software: First, open the installed mass spectrometry software, such as MassHunter, MestReNova, etc., on the computer.

2. Import mass spectrometry data: In the interface of the software, there is usually an option to import data, click on the option, select the mass spectrometry data file that needs to be searched for molecular formula, and import it into the software.

3. Setting search parameters: In the toolbar or menu of the mass spectrometry software, find the molecular search related function options, such as "Search" or "Formula Search". After clicking the option, a setting window will pop up, you can set the search parameters, such as the search range, error tolerance, etc.

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4. To perform a molecular formula search: Enter the molecular formula to be searched or a range of molecular formulas as needed, and click the Search button. The mass spectrometry software will search the imported mass spectrometry data according to the set search parameters to find compounds matching the entered molecular formula.

Explanation and expansion of the reason:

The purpose of the molecular formula search of mass spectrometry software is to determine the molecular formula of a compound from mass spectrometry data. Mass spectrometry breaks down molecules in a sample into ions and analyzes them based on their mass-to-charge ratio (m/z). Molecular formula searches utilize the m/z values of the ions in the mass spectrometry data to compare with the m/z values of known compounds to determine possible molecular formulas.

Setting the search parameters is critical in the molecular formula search process. The search range determines the size range of the molecular formula to be searched, while the error tolerance determines the allowable error range of the m/z value during the search. Depending on the characteristics and needs of the sample, these parameters can be flexibly adjusted to obtain more accurate search results.

It is worth noting that mass spectrometry software molecular formula searches are not absolutely accurate. There may be errors or multiple possible molecular formulae in the search results. Therefore, when using mass spectrometry software for molecular formula search, it is necessary to combine other experimental data, chemical knowledge and experience for comprehensive analysis and judgment to determine the final molecular formula of the compound.