A system comprising: a cannula having a proximal end, a distal end, and a lumen extending therebetween, the cannula attachable to a first container having a first chamber such that the cannula is in fluid communication with the first chamber; a syringe adapter having a housing and a cannula seal, the cannula seal disposed within the housing, the housing including a first connection element; and a container adapter (14, 18) attachable to a second container having a second chamber, the container adapter (14, 18) having a container seal and a second connection element, wherein the cannula seal comprises a resilient sleeve, the cannula seal moveable relative to the housing between a sealed position where the distal end of the cannula is enclosed by the cannula seal and a retracted position where the distal end of the cannula is positioned outside of the cannula seal, wherein with the first connection element of the syringe adapter engaged with the second connection element of the container adapter (14, 18), the syringe adapter is secured to the container adapter (14, 18), characterized in that the syringe adapter includes a spring disposed over the cannula such that the spring is radially positioned between the cannula and the cannula seal and provides a biasing force that promotes the cannula seal to enclose the cannula in the sealed position, wherein the cannula seal and the container seal provide a substantially leak-proof seal during engagement of the cannula with the second container during transfer of a first substance from the second chamber of the second container to the first chamber of the first container via the cannula, and during disengagement of the cannula from the second container. a cannula having a proximal end, a distal end, and a lumen extending therebetween, the cannula attachable to a first container having a first chamber such that the cannula is in fluid communication with the first chamber; a syringe adapter having a housing and a cannula seal, the cannula seal disposed within the housing, the housing including a first connection element; and a container adapter (14, 18) attachable to a second container having a second chamber, the container adapter (14, 18) having a container seal and a second connection element, wherein the cannula seal comprises a resilient sleeve, the cannula seal moveable relative to the housing between a sealed position where the distal end of the cannula is enclosed by the cannula seal and a retracted position where the distal end of the cannula is positioned outside of the cannula seal, wherein with the first connection element of the syringe adapter engaged with the second connection element of the container adapter (14, 18), the syringe adapter is secured to the container adapter (14, 18), characterized in that the syringe adapter includes a spring disposed over the cannula such that the spring is radially positioned between the cannula and the cannula seal and provides a biasing force that promotes the cannula seal to enclose the cannula in the sealed position, wherein the cannula seal and the container seal provide a substantially leak-proof seal during engagement of the cannula with the second container during transfer of a first substance from the second chamber of the second container to the first chamber of the first container via the cannula, and during disengagement of the cannula from the second container.