Revision to the standard for the active constituent dimethoate

The Australian Pesticides and Veterinary Medicines Authority invites comment from 26 October 2016 to 27 January  2017 on proposed changes to the current standard for the active constituent dimethoate. The purpose of the change is to update the standard in accordance with advice arising from the reconsideration of dimethoate which is consistent with the FAO standard published in 2005.

1. (Description) from:

• the material shall consist of dimethoate together with related manufacturing impurities and shall be in the form of white to greyish crystals, free from visible extraneous matter and added modifying agents

To:

• The material shall consist of dimethoate together with related manufacturing impurities and shall be a white solid, having a mercaptanic odour, free from visible extraneous matter and added modifying agents.

6. Composition

6.1 Active constituent: 950 g/kg minimum—no change

6.2 Toxicological or relevant impurities:

0,0,S-trimethyl phosphorodithioate: 5 g/kg max—no change

ADD Omethoate CAS No. 1113-02-6: 2 g/kg max

ADD Isodimethoate CAS No. 3344-11-4: 3 g/kg max

ADD Water: 2 g/kg max

See below the new proposed standard for dimethoate.

Please send your comments by email to or by mail to:

Director, Chemical Review
Australian Pesticides and Veterinary Medicines Authority
PO Box 6182
KINGSTON ACT 2609

Telephone: +61 2 6210 4947
Fax: +61 2 6210 4776
Email: chemicalreview@apvma.gov.au

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Draft standard for dimethoate active constituent

Version 2 (draft)

Effective date: TBA

1. Description: The material shall consist of dimethoate together with related manufacturing impurities and shall be a white solid, having a mercaptanic odour, free from visible extraneous matter and added modifying agents.

2. Common Name: Dimethoate.

3. Chemical Name (IUPAC): O,O-dimethyl S-methylcarbamoylmethyl phosphorodithioate

4. CAS Number: 60-51-5.

5. Identity test: identity of the active constituent must be established by one or more of the following methods: spectroscopic tests (IR spectrum, NMR, mass spectra), Chromatography (HPLC or GC retention time with reference compound) or any other suitable test method.

6. Composition
6.1 Active constituent: 950 g/kg minimum

6.2 Toxicological or relevant impurities:

0,0,S-trimethyl phosphorodithioate: 5g/kg max

Omethoate  CAS No. 1113-02-6: 2 g/kg max

Isodimethoate CAS No. 3344-11-4: 3 g/kg max

Water: 2 g/kg max

7. Analytical methods

• The analytical method used for the determination of the active constituent and toxicological significant impurities must be validated in accordance with the APVMA guidelines for the validation of analytical methods.
• The APVMA guidelines on validation of analytical methods state that—Analytical methods described in CIPAC¹ handbooks and AOAC² International Manual, and in recognized pharmacopoeias [BP, BP (Vet), Ph Eur and USP] for a particular active constituent or formulation are regarded as validated and do not require revalidation. However, the suitability of these methods must be verified under actual conditions of use i.e., the selectivity and accuracy of the method should be demonstrated for the published method when applied to the relevant sample matrix and laboratory conditions.
• When a CIPAC or AOAC method is used for the assay of an active constituent in a bulk active constituent, there is no matrix. The registrants need to check the specificity of the method to ensure there is no interference from impurities or degradation products. However, determination of accuracy of the method is not required as there is no matrix effect. However, when a CIPAC or AOAC method is used for the assay of an active constituent in a formulated product, determination of both specificity and accuracy is required as the matrix is relevant in formulated products (formulated products have different composition and quantities of excipients).
• Refer to Guidelines for the Validation of Analytical Methods for Active Constituent, Agricultural And Veterinary Chemical Products.
• Unless the scope of the collaborative method (CIPAC and AOAC) also includes toxicological significant impurities in the active constituent, validation data for impurities are required.