XRF malfunction?

[n10sivern]

so I bought a fair amount of isotope lead and had a piece of it XRF at the local scrap yard. It tested at 99.8% Pb which would likely be correct because the pencil test gave it a 5-6 hardness. Well, I stopped back by there to have some other containers XRF'd, even brought donuts. Well, supposedly the guy that checked my stuff before got in trouble and they said they couldn't do it again unless I was selling it to them. Another scrap yard 30 minutes away said they had no problem checking the lead with their gun. I went by there this morning and tested 10 different containers, 1 of them just like the previous one I had tested as a control. Their data was all over the place. A container that previously tested as 99.8% Pb now tested as 91.7% Pb and 6.67% Bi. Nothing else to get it closer to 100%. I also had an ingot of lead that was 100% made out of sheet lead taken from an X-ray room and it tested 91% Pb and 6.39% Bi. Every container tested positive for bismuth. Since it's so close to lead, I think their gun is messed up. Also, I had lead isotope containers testing positive for like 1% titanium. Craziness. I've contacted BNE to see if he's willing to test them. Oh well, hour round trip for nothing.

[pete501]

I have had similar results at a scrap yard. They retested the same sample with very different results. The operator said that the gun had to be re-calibrated, he wasn't sure if it needed to be sent back or they could do it.

[n10sivern]

I'm pretty sure they aren't adding titanium to lead isotope canisters. Unfortunately, the numbers are so wacky than I can't even just add the bismuth % with the lead % for total lead content and trust it.

[truckerdave397]

The XRF gun where I work gets sent away every so often to be recalibrated.

[tds]

The XRF gun needs to be calibrated. I had the same experience with results showing bismuth. A recently calibrated gun showed only lead and another gun that had not bee calibrated in over a year showed lead and bismuth

[n10sivern]

I sent samples off to a member for verification. There is no way the lead I had contained some of the stuff it was reading.

[RogerDat]

Calibration is probably the culprit, or debris on the sensor cover. Guns are really sensitive, can pick up Fe from a rust stain in a bucket. Titanium from the dust in tooling from gunning a barrel of shavings from CNC machine. Even absent total accuracy you can probably assume the lead & Bi are all lead and so there is a few percent "other" in there. I think there is also an element of setting the portable gun to what general element or elements one is looking for. Also they have to adjust to ambient temperature in a brief process before they are accurate.

[dragon813gt]

I'm interested in the findings. Mainly because your initial readings of almost pure is not what the couple thousand pounds I had were. Mine all tested at 96/3/1.

[n10sivern]

Are you talking about the big isotope cores? If so, mine are different than what everybody else is getting. They don't have an brass screw ins. They initially tested as pure and pencil BHN test confirmed that. I don't believe that they are anything but pure.

[dragon813gt]

Yes, large cores. But all of mine had the brass nutserts in them.

[n10sivern]

None of mine do so I think they are a different animal.

[jsizemore]

pure lead melts at 629degF and specific gravity is 11.35