The regulations for transporting liquids in your carry-on baggage through the security checkpoint.
Liquids can still be put in check-in baggage if they do not conflict with the regulations governing dangerous goods in check-in baggage on aircraft.
The purchase of duty free articles is no problem. Your purchase in the duty free store will be sealed in a special bag after its payment, which will be done by a store employee. This procedure will enable you to change planes anywhere, especially in the European Union, if the bag remains closed until you have reached your final destination. Please keep your sales slip which must have the date of your travel printed on it.
For enquiries contact your local offices, contact details can be found in the following link https://www.qatarairways.com/en/worldwide-offices.html