Did you try with 2-5% HNO3? Basically you need to put the cone in a beker with 2-5% HNO3 and place the beker in a sonicating bath. I never experienced this accumulation of sulfate, but it's worth trying.

Keep your sample cone as well as skimmer cone in 10% of HNO3 for 5min, sonicate it for 30-45 sec(if u sonicate the cones for the more than 1min the pore size of the cone may increase and u will fine the intensity issue) rinse it with distilled water and wipe gently with tissue paper. i think this should work.

My guess is that brushing would not help as it is mainly internal surfaces of the skimmer that are responsible for memory effects. Sonicating in acid bath, as others advise is probably the only way to clean that surface.

Hello Sarah,

when the orifice of ICP-MS sampler and skimmer was spoiled by some accretion I had good results using a strip of dental floss. Have a look that the floss diameter fits the orifice diameters of ICP-MS sampler and skimmer, which are in the range of 0.8 to 1.1 mm. Disassemble the cone from device, Pull the smooth thread end through the orifice in direction of cone opening until the fuzzy tufted segment reaches the orifice. Bring some droplets of diluted acid (1 N HNO3) onto the tufted part and pull the thread carefully and softly through; repeat. Rinse with distilled water. Take care to use floss with diameter as small as possible; otherwise, you could adapt the diameter by trimming the tufted part adequately (scalpel, razor blade). Controls: i) optical control before and after cleaning (binocular 20x – 40x should do); ii) run a reference before and after treatment; compare height and noise of signal (hopefully with improvement). Side note: a worn out orifice will not stand the treatment; however, worn out cones are of no use, anyway.

Good luck

D. W. Zachmann