SN/T 4693-2016 in English

Standard Background and Scope of Application

This standard was proposed by the National Certification and Accreditation Administration. It aims to establish a qualitative detection method based on a polarizing microscope for the possible risk of asbestos fiber contamination in daily latex consumer products. It is applicable to the detection of six types of fibrous silicate minerals such as chrysotile and amosite, filling the gap in asbestos detection standards for domestic latex products.

Core Detection Principle

After removing organic matter by ashing, sample slices are prepared using immersion oils of different refractive indices, and the fiber's morphological characteristics, optical properties and dispersion dyeing reaction are observed under a polarizing microscope. Key identification indicators include:

Key Operation Points

Sample Pretreatment

Ashing was performed in a muffle furnace at 450℃ for 4 hours, and the temperature was strictly controlled not to exceed 500℃ to avoid damage to the fiber structure. Parallel sample preparation required uniform slice thickness, and at least 8 fields of view were observed for each sample.

Instrument configuration requirements

It is necessary to be equipped with a polarizing microscope system that complies with GB/T 24665, with special requirements:

• Five-hole objective lens converter (10×/20×/40×)
• Mica test plate and gypsum test plate color complement
• Dispersion dye objective (360-700nm wavelength coverage)

Technology evolution analysis

Compared with the traditional X-ray diffraction method, the polarizing microscopy technology used in this standard has the single fiber identification capability and can distinguish fibers with a diameter of less than 0.5μm. The characteristic spectrum provided in Appendix CH establishes a complete visual comparison system to solve the problem of mixed fiber identification.

Implementation recommendations

1. Laboratories should regularly verify the accuracy of the system using asbestos standard samples (Clause 5.3)
2. Complex matrix samples are recommended to be reviewed in combination with SEM-EDS
3. Operators need to receive at least 40 hours of special training in microscopic observation