Is a dose of poison on a weapon used up if the target is immune to poison?

Question

The archer in our group was low on arrows, so he switched over to his poisoned ones. I told him the poison would not affect the undead, so they were essentially shot as normal arrows. After the fight however, he went to retrieve his arrows, claiming they were still poisoned. We are currently in a huge argument over wether or not the arrows are currently still effectively coated with poison. Please help us resolve this ASAP.

Does a poisoned arrow become un-poisoned as usual when it hits an enemy that isn't affected by poison?

Answer 1

From the rules:

Mundane ammunition

Generally speaking, ammunition that hits its target is destroyed or rendered useless, while ammunition that misses has a 50% chance of being destroyed or lost.

Magic ammunition

Magic Ammunition and Breakage: When a magic arrow, crossbow bolt, or sling bullet misses its target, there is a 50% chance it breaks or is otherwise rendered useless. A magic arrow, bolt, or bullet that successfully hits a target is automatically destroyed after it delivers its damage.

The poison doesn't matter, the arrow is destroyed when it hits, regardless.

Additionally, the poison rules say that the poison is consumed on a hit. The fact that the creature is immune to it doesn't matter.

One dose of poison smeared on a weapon or some other object affects just a single target. A poisoned weapon or object retains its poison until the weapon scores a hit or the object is touched (unless the poison is wiped off before a target comes in contact with it).

Applying poison to a weapon or single piece of ammunition is a standard action. Whenever you apply or ready a poison for use, there is a 5% chance that you expose yourself to the poison and must save against the poison as normal. This does not consume the dose of poison. Whenever you attack with a poisoned weapon, if the attack roll results in a natural 1, you expose yourself to the poison. This poison is consumed when the weapon strikes a creature or is touched by the wielder.

Answer 2

Typical poisoned arrows are dipped in poison. The poison wipes off the arrow and enters the targets blood stream when the creature is hit. This happens regardless if the target is immune or not. If you allow him to recover arrows, there would be no poison on them.

d20pfs

Applied contact poisons and injury poisons cannot inflict more than one dose of poison per weapon at a time (because the poison on the weapon only lasts for one successful attack before it wears off).

Applying poison to a weapon or single piece of ammunition is a standard action. ... This poison is consumed when the weapon strikes a creature or is touched by the wielder.

Of course, if he has access to poison he can repoison the recovered arrows.

House ruling:
As a compromise, you could roll a d20 for each arrow recovered.
15-20 the arrow still has a full dose of poison.
10-15 the arrow has a half dose. Half poison damage rounded down.
1-10 the arrow doesn't have any poison

Note: if you use this compromise, the player may insist on it for any target hit by his poison arrows.

Answer 3

From https://www.d20pfsrd.com/gamemastering/afflictions/poison/ (emphasis mine):

One dose of poison smeared on a weapon or some other object affects just a single target. A poisoned weapon or object retains its poison until the weapon scores a hit or the object is touched (unless the poison is wiped off before a target comes in contact with it).

Applying poison to a weapon or single piece of ammunition is a standard action. Whenever you apply or ready a poison for use, there is a 5% chance that you expose yourself to the poison and must save against the poison as normal. This does not consume the dose of poison. Whenever you attack with a poisoned weapon, if the attack roll results in a natural 1, you expose yourself to the poison. This poison is consumed when the weapon strikes a creature or is touched by the wielder.

So, yes, the rules are clear that the arrows stop being poisoned when they strike a creature, regardless of whether the creature is immune to poison.

Kyle's answer, about arrows being destroyed on impact, is also relevant here.