Step 1: Sample preparation - the cornerstone of analytical accuracy

Sample preparation is the foundation of the entire analysis process and directly affects the accuracy of the final results. Different types of samples require different pre-treatment methods:

Liquid samples (such as water quality samples) usually only require simple filtration and acidification treatment to remove suspended solids and maintain elemental stability. For solid samples such as soil, food, and metal materials, they need to be converted into liquid form through a digestion process. Common digestion methods include electric heating plate digestion, microwave digestion, etc. Strong acids such as nitric acid and hydrochloric acid are used to dissolve the target elements in the sample under high temperature and pressure.

All samples must be strictly avoided from contamination during the preparation process, using high-purity reagents and operating under suitable temperature and pressure conditions to ensure that the samples dissolve and the elements to be tested are not lost.

Step 2: Instrument Preparation - Ensuring Precision Analysis

Before sample analysis, it is necessary to ensure that the ICP spectrometer is in optimal working condition:

The gas supply system needs to check the purity of argon gas (usually requiring ≥ 99.996%) and pressure stability, as argon gas is not only the working gas for generating plasma, but also plays a cooling and auxiliary role. The injection system includes an atomizer, a mist chamber, and a torch tube, which need to be confirmed to be unobstructed and free of contamination. The detector needs to be preheated and stabilized to ensure consistency in signal response.

Instrument calibration is a key step in this stage, using blank and standard solutions to establish calibration curves and verify whether the instrument sensitivity, stability, and linear range meet analytical requirements.

Step 3: Sample Introduction and Atomization/Ionization - The Core of Technology

The prepared samples are introduced into the ICP system either through an automatic sampler or manually. The sample solution first passes through an atomizer and is broken into fine aerosols by high-speed argon gas flow; Subsequently, screening is carried out in the fog chamber, and only the finest droplets (usually with a diameter<10 μ m) can enter the central channel of the plasma.

When the sample aerosol enters the argon plasma region with a temperature of 6000-10000K, it instantly undergoes solvent removal, evaporation, atomization/ionization processes, and the elements in the sample transform into ground state atoms or ions. This high-temperature environment ensures that the vast majority of elements can be effectively excited, which is the key to the high sensitivity of ICP technology.

Step 4: Spectral Separation and Signal Detection - Accurate Identification and Quantification

The excited atoms or ions will emit spectra of characteristic wavelengths of the elements. In ICP-OES, the spectroscopic system separates these mixed lights into monochromatic light through gratings or prisms, and then the detector (such as CCD, CID, or photomultiplier tube) receives the light signal of a specific wavelength and converts it into an electrical signal.

For ICP-MS, ions with different mass to charge ratios are separated by a mass spectrometer and counted by an ion detector to achieve qualitative and quantitative analysis of elements.

Step 5: Data Processing and Result Output - Intelligent Analysis

The signal obtained by the detector is transmitted to the computer data processing system, and the software automatically compares the characteristic spectral line intensity or mass spectrometry signal with the calibration curve to calculate the concentration of each element in the sample.

Modern ICP software has powerful data processing capabilities: automatically removing background interference, correcting spectral overlap, identifying outliers, and generating detailed analysis reports. Analysts only need to make reasonable judgments on the results and confirm whether they meet quality control requirements.