Bringing the weaker parts to match with the strong.

[buffbong]

i agree with what most of the others said. the volume you are doing for arms is more than enough. 6sets for bis and for tris is plenty. atleast the last set of each exersize should be taken to postive failure.
 lee haney wrote a article about specialized routines for bringing up lagging parts. i would search for that to check out his thoughts.

example arm routines
tris one
close grip bench presses 10-6-6
lying dumbell exts          3x10

two
bar dips 10-8-8
lying e-z bar exts 3x10

bis
one arm preacher curls 3x10
standing e-z bar curls 2x8

two
one arm preacher curls 3x10
standing dumbell curls 2x8

just examples of my routines nothing special but they are basic and effective. id train each once a week and try to add wieght.