As with the TDCR and CNET sources, nominally 0.06 g of the respective X-D2 solutions were gravimetrically added to each hemisphere prior to being sealed with epoxy.
The TDCR sources were measured in the NIST TDCR system  using the MAC3 module to handle the coincidence logic .
Activity concentration values for each individual TDCR measurement were calculated using a second-order polynomial fit to data provided by Kossert  obtained by using the MICELLE2 code .
The difference between the LTAC and TDCR results for the acid solution was 0.38 % and was within the respective experimental standard uncertainties (p = 0.096 from Student t- distribution for equal means).
The use of the triple-to-double coincidence ratio (TDCR) LSC method for activity standardizations has been reviewed in depth by Broda .
In modern applications, the "enhanced TDCR method" , which accounts for PMT inequality but requires a more sophisticated computational model, is often applied.
The NIST TDCR spectrometer has been described by Zimmerman et al.
TDCR results can be affected by the model used, LS cocktail instabilities, and aspects of the counting conditions including count rate and various instrumental parameters.
Key words: anticoincidence counting; CIEMAT/NIST method; germanium-68; liquid scintillation counting; positron emitter; standardization; TDCR method.
Seeking to take advantage of this, we have measured a single solution of [.sup.68] Ge/[.sup.68] Ga using three LS-based method: live-timed 4 [pi] [beta] - [gamma] anticonincidence (LTAC) using LS as the [beta] counting channel, the Triple-to-Double Coincidence Ratio Method (TDCR) (9), (10), and CNET (6), (7).
For the TDCR experiments, two cocktails each of HiSafe-3 and PCS were prepared by dispensing 10mL of the scintillant into four 22 mL borosilicate glass LS vials (two per scintillant), followed by the gravimetric addition of nominally 0.04 g of solution from AID2.
Two background blanks (one for each scintillant) were prepared for the TDCR and LTAC measurements in their appropriate vials.