Soil heavy metal detectorIt is a portable device for rapid screening of heavy metal pollutants such as lead, cadmium, mercury, chromium, etc. in soil. Its core principle revolves around the specific reaction between the tested heavy metal ions and specific reagents, combined with optical or electrochemical detection technology, to achieve rapid quantitative analysis. The following is a disassembly explanation of mainstream detection principles:
1、 Spectrophotometric method (colorimetric method) - the most commonly used principle for rapid detection
This is the core technology of a portable soil heavy metal detector, which is easy to operate, low-cost, and suitable for rapid on-site detection.
Preprocessing Fundamentals
Take a quantitative soil sample and add a digestion solution (such as a mixture of dilute nitric acid and hydrochloric acid) for rapid digestion, converting solid heavy metals in the soil into water-soluble heavy metal ions.
Color reaction core
Adding a specialized color developer to the digested solution will cause a specific complexation reaction between the color developer and the target heavy metal ions, resulting in the formation of compounds with specific colors.
Example: When detecting lead ions, the dithizone color reagent will bind with the lead ions to form a red complex; When detecting cadmium ions, the cadmium reagent will form a pink compound with it.
The depth of color is directly proportional to the concentration of heavy metal ions in the solution, and the higher the concentration, the darker the color.
Detect readings
The detector is equipped with a built-in spectrophotometer, which emits light of a specific wavelength through the colorimetric solution and calculates the concentration of heavy metals by detecting the absorbance.
Absorbance: The darker the color of the solution, the higher the degree of light absorption and the higher the absorbance value.
The instrument has a built-in standard concentration absorbance curve, which directly outputs the heavy metal concentration results by inputting the detected absorbance values into the curve.
2、 Electrochemical Method - Common Principles for High Precision Detection
Some portable detectors use electrochemical methods, which are suitable for precise detection of low concentration heavy metals. The core is the electrochemical reaction between electrodes and heavy metal ions.
Working electrode reaction
Drop the dissolved soil solution into the detection electrode pool, and heavy metal ions will undergo oxidation or reduction reactions on the surface of the working electrode, producing weak current or potential changes.
Signal conversion calculation
The instrument captures current/potential signals through electrodes, and the signal strength is linearly related to the concentration of heavy metal ions.
Common type: anodic stripping voltammetry (ASV), which amplifies the signal through a two-step enrichment stripping reaction, with detection accuracy up to ppb level (one billionth).
advantage
No need for color reagents, faster detection speed, strong anti-interference ability, suitable for the detection of volatile heavy metals such as mercury and arsenic.
3、 X-ray Fluorescence Spectroscopy (XRF) - Principle of Non destructive Rapid Testing
The portable XRF soil heavy metal detector does not require pre-treatment for digestion and can directly detect soil samples, making it suitable for large-scale on-site screening.
Core reaction process
The instrument emits X-rays to irradiate soil samples, which excite heavy metal atoms in the samples and release characteristic fluorescent X-rays.
qualitative and quantitative analysis
Qualitative analysis: The characteristic fluorescence X-ray wavelengths of different heavy metal elements are different, and the types of heavy metals are determined by identifying the wavelengths.
Quantitative: The intensity of characteristic fluorescent X-rays is directly proportional to the element content, and the concentration of heavy metals is calculated based on the intensity.
局限性
The uniformity requirement for soil samples is high, and the detection accuracy is slightly lower than the first two methods, making it suitable for rapid initial screening.
summary
Soil heavy metal detectorThe rapid detection capability of * * is essentially a combination of * * "sample preprocessing+specific reaction+signal detection" * *:
Spectrophotometric method: relying on colorimetric reaction and absorbance detection, suitable for rapid screening on site.
Electrochemical method: relying on electrochemical reactions and current/potential detection, suitable for precise determination of low concentrations.
XRF method: relying on characteristic X-ray and fluorescence detection, suitable for non-destructive and rapid initial screening.
Different principle detectors are suitable for different scenarios and can be selected according to the requirements of detection accuracy and efficiency.