China toothpaste testing methods were approved and released by the National Medical Products Administration (NMPA) on March 21, 2024. These 15 testing methods are incorporated into China’s Cosmetics Safety and Technical Standards (CSTS). Effective from December 1, 2024, these testing methods apply to toothpaste notification and NMPA Sampling Inspections. Here are the 15 toothpaste testing methods:
1. Determination of pH in Toothpaste
- The method involves immersing a composite electrode into the solution being tested to form a battery. The potential difference generated by this battery is related to the pH of the solution according to the Nernst equation. The pH value can be directly read from the instrument.
Refer to “Chapter IV Physical and Chemical Inspection Methods / 1 Physical and Chemical Inspection Methods General / 1.11 Toothpaste pH test methods”.
2. Determination of Mercury in Toothpaste
- Method 1: Hydride Generation Atomic Fluorescence Spectrometry: After sample digestion, mercury is dissolved. Mercury ions react with potassium borohydride to form mercury atoms. These atoms, when stimulated by a specialized mercury hollow cathode lamp, emit fluorescence at a characteristic wavelength. The intensity of fluorescence is directly proportional to the mercury content within a certain concentration range.
- Method 2: Mercury Analyzer Method: Samples are directly weighed into sample cell then subjected to drying, decomposition, catalytic conversion, and mercury vapor generation reactions. The generated mercury vapor undergoes cold atomic absorption spectroscopy for quantification.
Refer to “Chapter IV Physical and Chemical Test Methods / 1 Physical and Chemical Test Methods General / 1.12 Test Methods for Mercury in Toothpaste”.
3. Determination of Lead in Toothpaste
- Graphite Furnace Atomic Absorption Spectrophotometry OR Flame Atomic Absorption Spectrophotometry: The sample undergoes treatment to ensure lead exists in ionic form in the solution. Lead ions in the sample solution are atomized, and the absorbance of the resonance line from a lead hollow cathode lamp is measured. The absorbance is directly proportional to the lead content in the sample. Quantification is done by comparing the absorbed spectral line intensity with standard solutions under consistent conditions.
Refer to “Chapter IV Physical and Chemical Test Methods / 1 Physical and Chemical Test Methods General / 1.13 Test Methods for Lead in Toothpaste”.
4. Determination of Arsenic in Toothpaste
- Under acidic conditions, pentavalent arsenic is reduced to trivalent arsenic. It reacts with sodium borohydride and acid to form arsine gas, which decomposes into arsenic atoms when heated. These atoms emit atomic fluorescence under the excitation of an arsenic hollow cathode lamp emission spectrum. The fluorescence intensity correlates with arsenic concentration, facilitating quantification against standard solutions.
Refer to “Chapter IV Physical and Chemical Test Methods / 1 Physical and Chemical Test Methods General / 1.14 Test Methods for Arsenic in Toothpaste”.
5. Determination of Cadmium in Toothpaste
- Flame Atomic Absorption Spectrophotometry: It involves processing the sample to ensure cadmium exists in ionic form in the solution. After atomization, the cadmium ions in the sample solution absorb resonance lines from a cadmium hollow cathode lamp. The absorption quantity is directly proportional to the cadmium content in the sample. Quantification is achieved by comparing the measured absorption values with standard solutions under consistent conditions.
Refer to “Chapter IV Physical and Chemical Test Methods / 1 General Principles of Physical and Chemical Test Methods / 1.15 Test Methods for Cadmium in Toothpaste”.
6. Determination of Li and 37 Kinds of Elements in Toothpaste
- Inductively Coupled Plasma Mass Spectrometry (ICP-MS): It involves acid digestion of the sample to form a solution, which is then aerosolized and introduced into a high-temperature plasma. The elements are converted into positively charged ions and quantified by comparing their signal intensity with standard solutions.
Refer to “Chapter IV Physical and Chemical Test Methods / 1 Physical and Chemical Test Methods General / 1.16 Toothpaste in lithium and other 37 kinds of raw materials test methods.
7. Determination of Dioxane in Toothpaste
- The method employs Gas Chromatography-Mass Spectrometry (GC-MS) to analyze dioxane in toothpaste. After heating extraction in a headspace vial, the sample is subjected to GC-MS analysis. Quantification is performed using internal standard quantification and standard curve method based on retention time and relative abundance of characteristic ions.
Refer to “Chapter 4 Physical and Chemical Test Methods / 2 Prohibited Component Test Methods / 2.37 Test Methods for Dioxane in Toothpaste”.
8. Determination of Methanol in Toothpaste
- Gas Chromatography: After gas-liquid equilibrium or direct extraction, gas chromatography separation is employed with detection by a hydrogen flame ionization detector. Qualitative analysis is based on retention time, while quantification relies on peak area, calculated using a standard curve method.
Refer to “Chapter 4 Physical and Chemical Test Methods / 2 Prohibited Component Test Methods / 2.38 Test Methods for Methanol in Toothpaste”.
9. Determination of Free Formaldehyde in Toothpaste
- Post-Column Derivatization and High-Performance Liquid Chromatography (HPLC): Formaldehyde is separated by HPLC, then derivatized and detected using either a diode array detector or a fluorescence detector. Qualitative analysis depends on retention time and UV or fluorescence spectra, while quantification uses peak area and a standard curve method. The method’s detection limit is 0.00020%, with a lowest quantifiable concentration of 0.00067% when using 0.2 g of sample.
Refer to “Chapter 4 Physical and Chemical Test Methods / 4 Preservatives Test Methods / 4.10 Test Methods for Free Formaldehyde in Toothpaste”.
10. General Guidelines on Determination of Microbiology in Toothpaste
- The basic requirements for microbiological testing of toothpaste are outlined, including sample collection, preservation, and preparation. They specify the necessary instruments. Samples should be representative and maintained in their original packaging to prevent contamination. The testing process must adhere to strict microbiological safety standards, including sterilization of equipment and conducting all operations in a suitable laboratory.
Refer to “Chapter 5 Microbiological Test Methods / 7 General Rules for Microbiological Test Methods in Toothpaste”.
11. Aerobic Plate Count in Toothpaste
- The method for determining the aerobic plate count in toothpaste samples is outlined. Sample preparation involves diluting the toothpaste and inoculating it onto nutrient agar plates for incubation. After incubation, colonies are counted, and the results are reported based on the average colony count per plate.
Refer to “Chapter 5 Microbiological Test Methods / 8 Test Methods for Total Colony Count in Toothpaste”.
12. Determination of Thermotolerant Coliform Bacteria in Toothpaste
- Thermotolerant coliform bacteria are a group of aerobic or facultative anaerobic, Gram-negative, non-spore-forming rods that can ferment lactose, produce acid, and gas at 44.5°C after 24 to 48 hours of incubation. They are primarily found in human and warm-blooded animal feces and serve as indicators of fecal contamination, allowing assessment of toothpaste hygiene quality and inference of potential contamination with pathogenic intestinal bacteria.
Refer to “Chapter 5 Microbiological Test Methods / 9 Heat-resistant Coliform Test Methods in Toothpaste”.
13. Determination of Pseudomonas Aeruginosa in Toothpaste
- The method for detecting Pseudomonas aeruginosa in toothpaste is outlined. The method involves culturing toothpaste samples on specific agar plates at controlled temperatures, followed by various biochemical tests and observations to confirm the presence of Pseudomonas aeruginosa. The results are reported based on the growth characteristics and biochemical reactions observed during the testing process.
Refer to “Chapter 5 Microbiological Test Methods / 10 Test Methods for Pseudomonas aeruginosa in Toothpaste”.
14. Determination of Staphylococcus Aureus in Toothpaste
- The method involves culturing toothpaste samples on specific agar plates at controlled temperatures, followed by various biochemical tests and observations to confirm the presence of Staphylococcus Aureus. The results are reported based on the growth characteristics, biochemical reactions, and coagulase test results observed during the testing process.
Refer to “Chapter 5 Microbiological Test Methods / 11 Test Methods for Staphylococcus aureus in Toothpaste”.
15. Molds and Yeasts Count in Toothpaste
- The molds and yeasts count refers to the total number of molds and yeasts formed in 1 gram of toothpaste after processing and cultivation under specific conditions. This count helps assess the degree of contamination by molds and yeasts in toothpaste and its overall hygiene status. The method involves culturing the toothpaste sample on Sabouraud agar at 28°C ± 2°C for 5 days and then calculating the number of molds and yeasts that have grown based on their distinctive morphology and growth characteristics.
Refer to “Chapter 5 Microbiological Test Methods / 12 Test Methods for Moulds and Yeasts in Toothpaste.
Further information
Read the original NMPA announcement on China toothpaste testing methods.
Learn more about toothpaste filing in China with the latest information update from Beijing MPA.
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