Organic Tin Testing

1、Organic Tin

Organic tin compounds are metal-organic compounds formed by the direct bonding of tin and carbon elements. The general formula is RnSnX4-n (n=1-4, R is an alkyl or aromatic group). They are divided into two categories: alkyltin compounds and aromatic compounds. Their basic structures include monosubstituted, disubstituted, trisubstituted, and tetrasubstituted (referring to the number of R groups). 10-20% of tin production is used for the synthesis of organic tin compounds.

2、Uses

Main uses include: as catalysts, stabilizers (such as dimethyltin, dioctyltin, tetraphenyltin), agricultural pesticides, fungicides (such as dibutyltin, tributyltin, triphenyltin), as well as coatings and anti-mold agents for daily products. In the natural environment, these compounds decompose rapidly under the influence of heat, light, water, oxygen, ozone, etc. After entering an organism, they are easily absorbed by the small intestine or skin, particularly trisubstituted compounds which are most readily absorbed and distributed in the liver, kidneys, and brain. In the body, the microsomal drug-metabolizing enzyme system, primarily in the liver, rapidly dealkylates and dearomatizes them. The biological half-life of trisubstituted compounds is 3-11 days; after dealkylation, they become disubstituted and monosubstituted compounds, which have difficulty passing the blood-brain barrier and remain in the brain slightly longer. Tributyltin and triphenyltin are highly toxic to insects, bacteria, algae, etc. Trimethyltin and triethyltin are highly toxic to mammals. Increasing the number of carbon atoms reduces toxicity, hence tributyltin and triphenyltin are commonly used in pesticides and antifouling agents for fishing gear, increasing their release into the environment.

3、Hazards

The main damages of organic tin compounds to organisms include: central nervous system effects causing white matter edema in the brain, impairment of oxidative phosphorylation in cellular energy utilization, suppression of the thymus and lymphatic systems, hindrance to cellular immunity, and inhibition of hormone secretion leading to diabetes and hyperlipidemia. Human toxicity includes local irritation to the skin, respiratory tract, and cornea; systemic poisoning through skin absorption or cerebral edema can lead to death. In 1958, France experienced a 10% mortality rate due to the use of triethyltin-containing medications for skin diseases (known as the Stalinon event).

4、Organic Tin Compound Testing Standards and Regulations

(1) GB/T 18885—2002 Technical Requirements for Ecological Textiles

GB/T 18885—2002 Technical Requirements for Ecological Textiles include control requirements for tributyltin (TBT) and dibutyltin (DBT).

(2) REACH Annex XVII
Organic tin compounds must not be used in coatings or as pesticides on ships, aquaculture equipment, or any other devices submerged in water.

From July 1, 2010, trialkyltin compounds (including TBT, TPT) must not be used in articles and must not exceed 0.1% (by tin weight).

From January 1, 2012, DBT must not exceed 0.1% (by tin weight) in articles and mixtures;

DOT must not exceed 0.1% tin content in textiles in contact with skin, gloves, shoes, children's care products, etc.

(3) OEKO-TEX Standard 100

The ten organic tin substances specified in OEKO-TEX Standard 100 include: monobutyltin (MBT), monomethyltin (MMT), monooctyltin (MOT), dimethyltin, diphenyltin (DPhT), tricyclohexyltin (TCyHT), trimethyltin (TMT), trioctyltin (TOT), tripropyltin (TPT), and tetrabutyltin (TeBT).