Second hand mass spectrometerIt is a precision scientific instrument used for analyzing the composition and structure of substances, playing a key role in many fields such as chemistry, physics, biology, and environmental science. Its working principle is based on precise measurement of the motion behavior of charged particles in electromagnetic fields. The sample is first ionized and converted into charged ions. These ions are accelerated in an electric field and then enter a magnetic field. Under the action of a magnetic field, ions will undergo deflection, and the degree of deflection of ions with different mass to charge ratios (the ratio of ion mass to charge) varies, resulting in specific signal distributions on the detector, namely mass spectra. By analyzing the position, intensity, and other information of each peak on the mass spectrum, the molecular weight, structure, and relative content of different components in the sample can be determined.

Here isSecond hand mass spectrometerDetailed instructions for general operating procedures:

1、 Sample preparation (key prerequisite, affecting analysis results)

Select the appropriate processing method based on the sample state (solid, liquid, gas) and properties (volatility, thermal stability, polarity, etc.) to ensure that the sample can be effectively ionized and reduce interference:

Sample pre-treatment:

Liquid samples: If the purity is low, impurities need to be removed through filtration, extraction (such as liquid-liquid extraction, solid-phase extraction SPE), concentration (such as rotary evaporation), etc; If the concentration is too high, it needs to be diluted with solvents (such as methanol, acetonitrile) to the detection range of the instrument.

Solid samples: For thermally stable solids, they can be ground into powder and dissolved; If it is an insoluble solid (such as a polymer), derivatization (converting difficult to ionize substances into easily ionizable derivatives) or direct solid injection techniques may be required.

Gas samples: usually injected directly through gas sampling valves or enriched by adsorption desorption devices (such as detecting trace volatile organic compounds).

Sample dissolution and matrix matching:

Choose a solvent compatible with the ionization source (such as polar solvents commonly used for ESI sources and non-polar solvents commonly used for EI sources) to avoid solvent reaction with the sample or the generation of interfering ions.

For biological samples such as blood and urine, it is necessary to remove interference from large molecules such as proteins (such as precipitation and centrifugal filtration).

2、 Instrument startup and parameter debugging

Power on preheating:

Start the machine in the order specified in the instrument manual (usually starting the vacuum pump and power supply first, then the host and workstation software), ensuring that the vacuum system reaches the working vacuum level (such as high vacuum systems requiring 10 ⁻⁶ Pa), and that components such as the ion source and mass analyzer are stable (preheating time is usually 30 minutes to 2 hours).

Parameter settings:

Ionization source parameters: Select the ionization method based on the sample type (such as EI, ESI, MALDI, etc.), set the ion source temperature, ionization voltage, gas flow rate (such as ESI sheath gas, auxiliary gas), etc. For example:

EI source: Set the electron energy (usually 70 eV) and ion source temperature (150-300 ℃);

ESI source: set spray voltage (3-5 kV), capillary temperature (200-350 ℃) and atomizing gas pressure.

Quality analyzer parameters: Set the scanning range (m/z range, such as 50-1000), scanning speed, and resolution (choose according to requirements, such as high resolution for qualitative analysis and fast scanning for quantitative analysis).

Combined equipment parameters (such as GC-MS/LC-MS): If combined with chromatography, chromatographic conditions (such as column temperature, flow rate, and mobile phase ratio) need to be set synchronously to ensure that chromatographic separation matches mass spectrometry detection.

3、 Sample analysis (core operational step)

Sample injection:

Select according to the injection method:

Direct injection: Solid or liquid samples are directly fed into an ion source through an injection rod (suitable for pure samples or simple systems);

Chromatography injection: The sample is first separated by gas chromatography (GC) or liquid chromatography (LC), and then enters mass spectrometry through an interface (suitable for complex mixtures such as food and environmental samples);

Automatic sampling: Batch samples can be sequentially injected through an automatic sampler to improve efficiency and reduce human error.

Data collection:

Activate the "collection" function of the workstation software, and the instrument automatically scans the sample ions for mass to charge ratio, generating real-time mass spectra (with m/z on the horizontal axis and ion intensity on the vertical axis).

For quantitative analysis, it is necessary to first collect the mass spectrometry signal of the standard sample, establish a standard curve (the relationship between ion strength and concentration), and then analyze the unknown sample.

Quality Control:

Before analyzing each batch of samples, calibrate the instrument with a standard substance (such as perfluorotriamine PFTBA for calibrating m/z) to ensure the accuracy of the mass to charge ratio;

Insert blank samples (such as solvents) to eliminate background interference; Repeated injection validation for repeatability (relative standard deviation RSD usually needs to be<5%).

4、 Data processing and shutdown

Data processing:

Using workstation software to analyze raw mass spectrometry data:

Qualitative analysis: Determine the type of compound by comparing characteristic ion peaks (such as molecular ion peaks and fragment ion peaks) with standard spectral libraries (such as NIST libraries); High resolution mass spectrometry can directly provide accurate molecular weight and assist in structural identification.

Quantitative analysis: Select characteristic ions of the target compound (such as parent ion daughter ion pairs, suitable for triple quadrupole mass spectrometry), and calculate the sample concentration based on the standard curve.

Export analysis results (such as mass spectra and concentration reports) for result validation (such as eliminating false positives and confirming peak purity).

Instrument shutdown:

Stop data collection first, turn off ion source parameters (such as voltage and heating), then turn off the combined equipment and host power in sequence, and finally turn off the vacuum pump (some instruments need to wait until the vacuum degree decreases before turning off the pump).

Record the usage status of the instrument (such as vacuum level and malfunction), clean the injection system (such as flushing the chromatographic column and injection needle).