During the GasBench installation, the service engineer was observed cutting a shallow tray of sorts from the side of a plastic milk jug, into which he placed the acid pump. Paraphrasing...

Me: "What are you doing?"

Service engineer: "Making a tray for when the acid pump leaks."

The (peristaltic) pump blew a seal on day 3 or 4 of its use, and so said tray was a really good idea. The warranty replacement pump still resides "new" in its shipping carton 9+ years later.

Since then acid is injected by hand. The autosampler is set so the sample needle always lands in the southeast quadrant of the septum, and thus we always aim for the northwest quadrant with the acid injection needle/syringe (with the heating block cover removed for more precise aim). This avoids plugging the needle with crystallized acid and giving extended service life around 5000 samples for a single sample needle.

We keep an exetainer of o-phosphoric acid in the heating block to decrease its viscosity and make it easier to exclude bubbles from the injection syringe. We use a 1 ml syringe that will fit into the heated exetainer for refills. Expect it to hold enough for 16 or so samples, at eight drops each. Always better a few too many drops, rather than too few. You want your sample fully wetted.

Bubbles in the acid syringe will allow drips, because when the syringe is inverted for injection, the dense acid provides enough pull so that the bubble will expand and acid will drip. Attempt to exclude these bubbles, mostly by holding the syringe upright and whacking sharply but lightly on the benchtop edge to get them to rise, and plunger them out.