Is giving 10% of one's monthly salary with the intention of charity (sadaqah) and zakat to the people of Syria and some poor individuals sufficient to fulfill the obligatory zakat?

If you donate a portion of your wealth with the intention of charity (sadaqa) and another portion with the intention of zakat, then what you have given with the intention of zakat will suffice for the obligatory zakat, provided you possess the minimum taxable amount (nisab). It is permissible to pay zakat in advance before the full year (hawl) has passed. The time when zakat becomes obligatory is upon the completion of a full Hijri year on wealth that has reached the nisab, and it is not permissible to delay it thereafter. However, if the wealth is given with the intention of both zakat and charity simultaneously, it will not suffice for the obligatory zakat.