To change moderator purity:

! Moderator D2O
! Atom purity - 99.91 %

EVALUATE Tmod   Pmod    ppmB hpitch       mhpitch     
           hpitchm01 mhpitchm01 := 
           346.0  99.91   0.0  28.575 2. /  -28.575 2. /  
           28.575 2. / 0.1 -   -28.575 2. / 0.1 +  ;