Can a buckler be dealt armored sacrifice damage while two-weapon fighting?

Question

Armored Sacrifice (Ex): When damage would cause the fighter or an adjacent ally to be knocked unconscious or killed, the fighter can instead direct the damage to a suit of armor that he is wearing or a shield he is using as an immediate action. The original target takes no damage, but the armor or shield is treated as if it had only half its normal hardness. The fighter can use this option once per day, plus one additional time each day at 11th level and every 8 fighter levels thereafter, to a maximum of three times per day at 19th level.

If I have a buckler equipped and make a full attack while two-weapon fighting, I lose the buckler's bonus to AC, but can I still redirect damage from me or from an ally to that buckler using the special ability armored sacrifice?

Answer 1

To expand on Robert's answer this is the key portion of the ability:

the fighter can instead direct the damage to a suit of armor that he is wearing or a shield he is using as an immediate action.

If we read the description of buckler we see,

This small metal shield is worn strapped to your forearm. You can use a bow or crossbow without penalty while carrying it. You can also use your shield arm to wield a weapon (whether you are using an offhand weapon or using your off hand to help wield a two-handed weapon), but you take a –1 penalty on attack rolls while doing so. This penalty stacks with those that may apply for fighting with your off hand and for fighting with two weapons. In any case, if you use a weapon in your off hand, you lose the buckler’s Armor Class bonus until your next turn. You can cast a spell with somatic components using your shield arm, but you lose the buckler’s Armor Class bonus until your next turn. You can’t make a shield bash with a buckler.

Since two-weapon fighting uses your off-hand, you wouldn't be considered using the shield, and thus would be unable to use Armored Sacrifice.

However, if you were to take Unhindering Shield you'd be able to benefit from Armored Sacrifice even if you were two-weapon fighting.

Answer 2

I would have to go with no, as you are not using the shield. To use an item you would have to benefit from it, such as if the shield was enchanted with Longstrider you would lose the 10ft enhancement bonus to speed whenever you swing with that weapon.