xrf user error !!!!

[Jimmi_p]

hello everyone!!! this is of course my first post. but Ive been hanging out reading for some time. Just an fyi. I was at one of my silver buyers last night with a friend and his father. we had brought them some silver bars, gold coins and some samples of my fine gold. they used their xrf to try and verify the samples and it worked just fine on the silver bars but not on the gold.
Every time we shot the gold (and yes i'm positive its pure gold) it came up as tungsten. I have run into this problem one time before. It turns out that there is another setting for PM's on the gun the "operators" were unaware of. Under all alloys it reads gold as W because W is like 99.1 %the atomic weight of gold.
I tried to tell them about the gold setting in the menu but they were unable to figure it out. And me, i was not able to remember how to get to the setting off hand. And they didn't want to hand their $40,000.00 gun over for me to find.
When in doubt consult the instructions.
according to the manufacturer;
Niton XRF Analyzer model xl2
1) turn the unit on and wait for the main menu screen to appear.

2) select sample type from the menu

3) from there select metals

4) then select precious metals

5) allow it to change over then then operate as usual.

found out in a three minute phone call. why didn't they think of that? heck i even suggested they read the directions. i guess its just hard to find good help these days... btw; thank you! to all of you who have made this site just a huge wealth of information!!!
jimmi

 

[4metals]

I've worked with refiners who generate very high grade gold (>99%) by doing stone removal. The reason the gold isn't higher purity is they add any insolubles from the processing to the fine gold melt so the customer is given credit for insolubles. Using a XRF to get a good value quickly yielded very strange results. Not unlike experienced by Jimmi.

We assayed samples of the high grade gold using an atomic absorption so the contaminants could be quantified and used the samples as standards which are used specifically for high grade gold. When the XRF is programmed for this type of material with standards made for the purpose, the results can be very accurate and fast.

It is important to remember an XRF is a calibrated machine. When the sample is very similar to the standards accuracy is good. When it varies greatly from a standard, beware the machine is winging it!

 

[nickvc]

Thanks 4metals that explains some of the dodgy results i have seen produced by these guns, maybe my scepticism was Ill founded and the problems that I encountered were caused by operators not fully understanding the proper way to set them up. I can now see that if used and set up correctly they can be an invaluable tool for fast and very accurate results....I wonder how many people that have and use them have a clue how to get the best out of them?

 

[Oz]

If you are being paid for your refined gold/silver buttons and bars based on an xrf result, be sure to bring along a gold or silver eagle (or bullion coin of your choice) to pull out of your pocket after they determine your purity. This way you can check the accuracy of their equipment.

 

[4metals]

The XRF was developed to give quick accurate results and non destructive testing for manufacturers who would set the machines up with standards made for the alloys they used.

Refiners buy scrap. It's a mixture of everything, so determining the best standard to use when you are really blind to what you're testing is difficult. In the case I mentioned we knew pretty well what we would be seeing so getting it to work accurately was easier.

With general scrap the numbers will be a bit off. Of course a refiner can tip the scales in his or her favor and have it off on the low side for insurance. Me, I'm a fire assay guy!!!!!

 

[HAuCl4]

Me, I'm a fire assay guy!!!!!

8)

I wonder what an XRF gun would read on a 12.5 Kg tungsten bar with 0.5 mm gold plating...stamped 9985 :lol:

IMO XRF is one of the most overpriced, overrated gadgets in the industry!.

 

[nickvc]

The XRF was developed to give quick accurate results and non destructive testing for manufacturers who would set the machines up with standards made for the alloys they used.

Refiners buy scrap. It's a mixture of everything, so determining the best standard to use when you are really blind to what you're testing is difficult. In the case I mentioned we knew pretty well what we would be seeing so getting it to work accurately was easier.

With general scrap the numbers will be a bit off. Of course a refiner can tip the scales in his or her favor and have it off on the low side for insurance. Me, I'm a fire assay guy!!!!!

I totally agree 4metals but always thought I was a bit of a dinosaur in that regard!

 

[Jimmi_p]

As 4metals and Oz were saying it is normally all about the calibration. Thats why I had brought some of my fine gold. It had already been tested.
I wanted to know how accurate their readings were before my friends decided to settle with them. ( I have paid attention to everything Ive read on this site and am thankful for it )

Imagine my surprise when they didn't even know how to get to the PM setting of there own guns. Oh yeah did I mention the even brought out a second gun? The first operator said to me "all this stuff is just gold colored tungsten." The other guy new better as Ive sold him around nine pounds of silver. He did say he was sorry though. I am extra sorry. because I now have to drive an hour and a half back to settle something that should have been done on Monday. I want to show them the fist direction in the instructions manual "1) read all of these instructions." lol

 

[Lou]

Most importantly is that the machine be calibrated over its working range with known, traceable standards!

By that I mean, have a 4K, 6K, 8K, 10K, 12 K, 14K, 16K, 18K, 20K, 22K, 24K disks with each having the same surface properties.

Doing this establishes linearity in the machine's response curve.

 

[Irons]

Most importantly is that the machine be calibrated over its working range with known, traceable standards!

By that I mean, have a 4K, 6K, 8K, 10K, 12 K, 14K, 16K, 18K, 20K, 22K, 24K disks with each having the same surface properties.

Doing this establishes linearity in the machine's response curve.

..and the same alloy ingredients. There are so many variations in a given K, that it's bound to have some effect on the reading.

 

[jessica]

hello. I am from XRF technological research center. I do not know whether you have solved the problem, but i only give some suggestions about the eror.
You said that when testing gold, it always reads W. i think that the peak may swift. as we all know, the peaks of W and Au are very close, and the spctrums of W and Au are very same. so we advise your silver buyer to make energy calibration for his machine.
we know that Niton belongs to Thermo Fischer. Niton is a very famous brand in the world, and it is really very good. but i think maybe it is not very easy to operate for jewelers, as it not only use for jewelry field. so if you are interested in the machine which is only designed for jewellers, you can contact Rosenthal Jewelers Supply in USA. here is the specific information:
Rosenthal Jewelers Supply
145 E. Flagler Street
Miami FL 33131
800-327-5784
305-573-6866
305-572-9782 fax
email: [email protected]
website:http://www.jewelerstoystore.com/XRay_Precious_Metal_Tester_p/xf-pmt.htm.

Rosenthal Jewelers Supply has XRF machine, which is automatical and more human-centered, and whose testing results can be close to Fire Assay and can compare with Fischer and Niton.you only cost one third or half of USD 40 000 to buy a XRF machine from low-end to high-end from Rosenthal Jewelers Supply. the performance can compare with those famous brands in the world. you can also send some samples to Rosenthal Jewelers Supply for testing and make some comparison. You will find the most cost-effective XRF machine.

 

[Oz]

you can also send some samples to Raphael for testing and make some comparison.

Now that is an interesting proposition. Would that be at no charge in order to compare your equipment to others?

 

[jessica]

Now that is an interesting proposition. Would that be at no charge in order to compare your equipment to others?

Testing is free of charge and it only costs a liittle to make samples. You may cost some to test samples by Fire Assay method. You may find that you only cost very small money to make the comparison, but it can greatly reduce the risks to buy the equipment. You can also send very small pieces of samples to us for testing and we will send back the testing results to you. if you are interested, you can send me private messenge about the specific information of your company and your email address .