Specifications of the Standard SPMD

The design of commercially available SPMDs consists of a specified length (e.g., 91.4 cm between the inner-LDPE welds for 1 mL of triolein) of additive free, 2.5 cm wide layflat LDPE tubing. The LDPE wall thickness ranges between 70-95 pm and the triolein used is 95% purity. Note that in the USA, all commercially available SPMDs are fabricated with 99% purity triolein. The A y ratio is about 90 cm cm (lipid plus membrane), or about 460 cm mL of triolein. The standard SPMD thereby consists of approximately 20% triolein. For the 1 mL triolein configuration, the whole device typically weighs about 4.4 to 4.6 g. 

Any length of SPMD with an A V ratio of about 460 cm mL of 95% triolein, having an approximate 0.25 lipid-to-membrane-mass ratio (i.e., 20% lipid) and a 70-95 pm wall thickness is considered a standard SPMD. However, the aforementioned QC certification requirements for the membrane and triolein must be met. Because most SPMD calibration data and field data are based on the standard configuration, the use of non-standard designs for monitoring must be weighed against the lack of data comparability. 

---