Heavy MetalTesting

1. Introduction

Common heavy metal elements in textiles and leather include lead, nickel, cadmium, copper, arsenic, mercury, cobalt, and chromium. Their primary sources are dyes and auxiliaries used during processing, such as various metal complex dyes, flame retardants, and tanning agents.

2. Hazards

Heavy metals are very difficult to biodegrade. They can interact strongly with proteins and enzymes in the human body, causing them to lose activity. They may also accumulate in certain organs, leading to chronic poisoning.

3. Detection Methods

Heavy metal detection primarily involves spectroscopic and mass spectrometric methods, including:

(1) Atomic Absorption Spectroscopy (FAAS, GFAAS)

A light source such as a hollow cathode lamp emits characteristic spectral radiation, which passes through an atomizer. The monochromatic light is obtained through a spectroscopic system and then reaches the detector via a photomultiplier tube. When the atomizer introduces a sample, part of the light is absorbed as it passes through, reducing the transmittance. According to the Lambert-Beer law, absorbance is proportional to the sample concentration, so the concentration can be determined from the absorbance. Atomic absorption spectroscopy includes flame atomic absorption spectroscopy and graphite furnace atomic absorption spectroscopy. The former is easy to use, while the latter offers high sensitivity. Both are widely used in heavy metal detection.

(2) Atomic Fluorescence Spectroscopy (AFS)

When an excitation light source of certain intensity irradiates atomic vapor containing a specific concentration of the element to be measured, atomic fluorescence of a certain intensity is produced. By measuring the intensity of the atomic fluorescence, the content of the element in the sample can be determined. The instrument is relatively simple, highly sensitive, and easy to use, making it an economical and practical tool for inorganic element detection.

(3) Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES)

A high-energy source is used to excite electrons from the ground state to higher energy levels. The excited electrons release energy and fall back to lower energy levels, emitting light of characteristic wavelengths in the form of radiation. Since the intensity of the emitted light is proportional to the concentration of the element to be measured, the content of the element in the sample can be determined. ICP-AES/OES offers high precision, high sensitivity, low matrix interference, and a wide linear range. It can simultaneously detect multiple elements and has been widely applied.

(4) Inductively Coupled Plasma Mass Spectrometry (ICP-MS), etc.

Inductively coupled plasma mass spectrometry (ICP-MS) is an analytical technique that combines plasma technology with mass spectrometry. It uses inductively coupled plasma technology as the ion source and mass spectrometry as the detection method. A high-energy source excites electrons, causing them to escape from the electron shells of atoms, producing free electrons and positively charged ions. The ions are extracted, passed through a mass filter, and detected. The concentration of the element to be measured is determined directly by measuring the number of ions passing through the mass filter. This analytical method offers high sensitivity, strong resolution, low detection limits, a wide analytical range, fast analysis speed, accurate results, and the ability to detect almost all elements in the periodic table. It has promising application prospects.

In summary, spectroscopic techniques such as atomic absorption spectroscopy, atomic fluorescence spectroscopy, and atomic emission spectroscopy, as well as mass spectrometric techniques represented by inductively coupled plasma mass spectrometry, have been applied to the detection of heavy metal elements in textiles and leather.

Due to their mature technology and low cost, atomic absorption spectroscopy, atomic fluorescence spectroscopy, and atomic emission spectroscopy play important roles in the detection of heavy metal elements in textiles and leather.

Although inductively coupled plasma mass spectrometry is advanced, highly sensitive, and has a wide dynamic range, its high cost has limited its widespread use in the textile and leather testing fields. However, with economic development and increasing research reports on its applications, it is expected to be widely adopted in the future.