Inductively coupled plasma mass spectrometer

Date：2025/7/7 18:13:31

I. Core Principle

Samples are ionized by inductively coupled plasma (ICP), and elements are separated and quantitatively analyzed by mass spectrometry (MS) according to mass-to-charge ratio (m/z). After the sample is atomized and ionized at high temperature in plasma, an ion beam is formed. Ions with specific m/z are screened by a mass analyzer (such as a quadrupole) and counted by a detector (such as an electron multiplier), realizing qualitative and quantitative detection of trace elements.

II. Key Structures and Functions

Components	Functions and Characteristics
Sampling System	- Nebulizer: Converts sample solution into aerosol (such as concentric nebulizer with an efficiency of about 1-5%);- Spray chamber: Condenses and removes large particles to maintain stable aerosol (double-pass glass spray chamber is commonly used);- Sample introduction methods: Liquid injection (conventional), solid injection (laser ablation LA-ICP-MS), gas injection.
Plasma Source (ICP)	- Composition: High-frequency generator (such as 27.12MHz), three concentric quartz torch (outer tube for cooling gas Ar, middle tube for auxiliary gas Ar, inner tube for carrier gas Ar to carry samples);- Temperature: 6000-10000K, ensuring complete ionization of samples (ionization efficiency > 90%).
Interface System	- Sampling cone (nickel or platinum): Intercepts ion beam from plasma (aperture 0.7-1mm);- Skimmer cone: Further focuses ions to form a vacuum transition (maintains 1-10Pa vacuum between the two cones).
r	- Quadrupole (most commonly used): Screens ions through radio frequency + DC voltage, with a scanning range of m/z 2-260 (such as detecting Li to U);- Magnetic mass spectrometry (MC-ICP-MS): High resolution, used for accurate isotope determination (such as Sr isotopic ratio);- Time-of-flight (TOF-ICP-MS): Fast multi-element synchronous analysis.
Detector	- Electron multiplier (SEM): Detects low-concentration ions (10 levels), with a linear range of 10;- Faraday cup: Detects high-concentration ions and resists saturation.

III. Typical Analysis Process

Sample Pretreatment:

Liquid samples: Acidification (such as HNO acidification to 1-2%), filtration (0.45μm filter membrane);

Solid samples: Acid digestion (such as HNO + HF microwave digestion of soil and ore), extraction and volume fixing.

Instrument Parameter Optimization:

Plasma power: 1100-1500W (such as 1300W to improve ionization efficiency);

Carrier gas flow rate: 0.8-1.2L/min (optimize sensitivity and stability).

Ionization and Detection: Sample aerosol is ionized in ICP, enters mass spectrometry through the interface, and is quantified by selecting isotopes (such as Mn, 3Cu). The internal standard method corrects matrix effects (such as adding 2Ge to monitor signal drift).

Data Processing: Calculate sample concentration according to the standard curve (such as 10-level standard solution), subtract blank and interference correction (such as interference of Ar3Cl on As).

IV. Core Application Fields

Industry	Examples of Detection Objects
Environmental Monitoring	Heavy metals in water (Hg, Cd, Pb), trace elements in soil (As, Cr), trace elements in atmospheric particulate matter.
Geology and Minerals	Rare earth elements (REE) in rocks/minerals, isotopic ratios (such as Sr for geological dating), ore grade analysis.
Food and Pharmaceuticals	Heavy metal pollutants in food (such as Cd in rice), trace elements in health products (Zn, Se), inorganic impurities in pharmaceuticals (As, Pb).
Semiconductors and Materials	Trace metals in high-purity reagents/ultrapure water (such as Fe, Cu, requiring < 10 levels), element distribution in nanomaterials (with laser ablation).
Life Sciences	Element analysis in biological samples (such as Hg content in blood), isotope tracing (such as Cu-labeled drug metabolism research).

V. Comparison with Other Element Analysis Technologies

Comparison Item	ICP-MS	Atomic Absorption Spectroscopy (AAS)	Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES)
Detection Limit	0.1-10 ng/L (trace)	1-100 ng/L (micro)	1-1000 ng/L (micro)
Simultaneous Detection Capability	Can analyze 70+ elements simultaneously	Single element detection one by one	Can analyze multiple elements simultaneously (about 30-50 kinds)
Isotope Analysis	Supported (such as Y/Sr ratio)	Not supported	Not supported
Sample Throughput	High (autosampler can handle hundreds of samples)	Medium	High
Instrument Cost	High (500,000-2,000,000 yuan)	Low (100,000-500,000 yuan)	Medium (300,000-1,000,000 yuan)

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