Aspects of the present disclosure include a buffer pack for dispensing buffer for sample preparation using a sample preparation cartridge. Also provided are a sealing plate configured for holding the buffer pack and a cap for actuating the buffer pack in the sample preparation cartridge. Aspects of the present disclosure include a sample preparation cartridge that includes the buffer pack and the sealing plate. Aspects of the present disclosure also include a sample preparation cartridge that includes the buffer pack, the sealing plate, and the cap. Methods for filling the buffer pack, assembling a cartridge for use in sample preparation, and using the cartridge for preparing a sample also provided.