He said once the samples are brought back to OPCW's headquarters in the Netherlands, "they will be split in our laboratory in the Hague and sent to designated labs, which may take some time".
Its boss, Ahmet Uzumcu, has said it will take about another three weeks to analyse and confirm its origin.
Russia and the United Kingdom have been embroiled in a bitter diplomatic row since Russian former double agent Sergey Skripal, 66, and his daughter, 33-year-old Yulia Skripal, were poisoned in the English cathedral city of Salisbury on March 4.
Both Mr Skripal and his daughter remain in critical conditions.
Meanwhile, according to the news agency AFP, EU leaders will say later this week that they will "coordinate on the consequences" for Russian Federation following the Salisbury spy poisoning, but will stop short of mentioning sanctions.
"There are other measures that government and security officials are actively considering and stand ready to deploy at any time", she said. "We have destroyed all our chemical weapons under worldwide oversight unlike some of our partners".
Tough new checks on private flights used by multi-millionaire travellers including Russian oligarchs have been introduced in response to the "reckless and brazen" Salisbury nerve agent attack, Downing Street has announced.
The identification of Novichok as the weapon has become the central pillar of Britain's case for Russia's culpability.
President, PM express grief over killing of Indians in Iraq
Misinster of State V K Singh will go to Iraq to bring back the bodies of the victims. He said the bodies will be sent back to India "in a couple of weeks or so".
Thanking them on behalf of President Vladimir Putin, who on Sunday after his re-election repeated that Moscow had played no part in the attack, ambassador Alexander Yakovenko said: "We are proud of you".
The confrontation escalated after May accused Moscow on Wednesday of an "unlawful use of force" involving a weapons-grade nerve agent and ordered out the largest number of Russian diplomats from London in 30 years.
Johnson said Britain's National Security Council will meet this week to discuss "what further measures if any" the country will take.
Britain has thrown out Russian 23 diplomats over the March 4 nerve agent attack on former Russian spy Sergei Skripal and his daughter Yulia in an English town.
While Russia has vigorously denied involvement in the attack, Western powers see it as the latest sign of alleged Russian meddling overseas. Western powers have described it as a sign of increasingly aggressive Russian meddling overseas.
President Donald Trump joined British Prime Minister Theresa May and the leaders of Germany and France on Thursday to issue a joint statement pinning the blame for the attack squarely on the Russian government.
British police appealed Saturday for witnesses who can help investigators reconstruct the Skripals' movements in the crucial hours before they were found unconscious. British Ambassador Laurie Bristow was called to the Foreign Ministry Saturday morning to be informed of the moves.
The mutual expulsion of diplomats is expected to further deepen the conflict between the 2 countries. Britain says it is Novichok, a class of powerful nerve agent developed in the Soviet Union toward the end of the Cold War.