Might do that as a last resort. I will have take a closer look at the the guts, there may be a way to introduce a vacuum around the detector. The software has a vacuum option...hmmm, must mean something.

Practically, the XRF will do Ti to Bi. I can't find any way to introduce a vacuum. He flush might work, something to try later....
Only templates for Au, Ag, Pt and Pd are provided. I am adding other elements using pure reference samples. The software handles the calculations, but is a little tricky to set up correctly.

How effective is increasing the voltage at detecting lower concentrations of heavy elements. Also, would it improve the low z detection limit?

I assume you are talking about increasing the voltage of the X-ray tube. I don't know how yours is set up, but the Amptek system allows any voltage to be programmed into the tube. Pre-programmed setting is 40KV, but for lighter elements anything above 20KV is overkill.

Henry Barwood
Troy University
Troy, Alabama USA

My XRF is setup for 35KV and 60microamperes current, set by the manufacturer. It's a gas proportional spectrometer, so does not have the resolution of the Amptek.

I have scanned about 30 reference samples of elements, pure analytical reagents with known concentration.

I have the following options for calculating concentrations:

1. Net Areas
2. Gross Areas
3. Pure spectrum (single element)
4. Pure spectrum (multi element)

My understanding is that
net areas calculates the areas under peaks of interest and converts them to concentration
pure spectrum (single element) uses some type of k ratio calculation

I am not sure what gross area and pure spectrum (multi element) are for

So far, it works great for qualitative and semi quantitative elements. I have not done enough tests for evaluating quantitative results

What calculation method would you guys use for this type of spectrometer for quantitative analysis?

I thought that I would mention how cheap good vacuum pumps are, and how easy it is to make a vacuum chamber.

Every university has pallet loads of used vacuum pumps. Many are perfectly good, and can achieve adequate vacuum to detect sodium without the need for a diffusion pump. The pallets of vacuum pumps here at the U.W. in Seattle often sell for less than $100. I have some good pumps that I would give away.

I have an old Kevex XRF unit. Its vacuum chamber is a sliding drawer about 2"x1"x3". The beam is fat, but a sample holder could be made out of plastic to eliminate stray spectra.

A larger chamber is easy to build out of thick plexi-glas, and using a fluorescent target you could see your beam diameter and location.

I still believe that eventually Bob and Henry will buy an old SEM and interface their Amptek detectors.

There is no work-around for the image and analysis resolution obtained by an SEM.

I also have some SEMs that I would give away. They all need a little work, but that's fun of it.

Hi Bart,

I would love to be able to have an SEM/EDS machine at my disposal, but I teach at a "second tier" university with very limited research funds. The mini-XRF will likely be as close as I get to one.

My experiences with fixing SEM's was entirely negative and I doubt I have enough time and resources left to tackle that kind of a project.

I do hope to have an XRD operational by summer. I like using a powder camera for mineral identification. I've worked with them so much that they hardly seem time consuming and they do provide reasonably definitive identification of a mineral species. If you happen to have EDS/WDS data also that is confirmation of the identify of the mineral.

At one time I had a micro XRF that Phillips/Norelco made for their vacuum spectrograpth. Left it behind during a move and it is likely in a landfill somewhere. Wish I had it now. It did pretty good spot analyses, and was WDS.

Henry

Henry Barwood
Troy University
Troy, Alabama USA

If I want to determine the beam width and location on my EDXRF, as Bart mentioned, what type of fluorescent target would be a good choice?

Standard is a fragment of benitoite.

Henry Barwood
Troy University
Troy, Alabama USA

I am doing a little catching up here. Sounds like dental x ray film may be more suitable for my machine. What is the story with this? Can it be opened and used in daylight, or does it need a darkroom?

You can get pakages opf film with developer form China on eBay. They are inexpensive, but in spite of the advertisement, they do require a darkroom to develop. At least, I've not been able to get them to work in full light. they are quite sensitive and will show a focal spot nicely if you note the positiion of the film accurately.

Henry Barwood
Troy University
Troy, Alabama USA

Thanks for the tips Henry. Use of a dark room is only a minor inconvenience.

Rock Bob - Which low cost Chinese XRF tabletop system did you get? Could you tell me how much you paid and the contact as I am wanting a tabeltop XRF setup.

Rock Bob - Which low cost Chinese XRF tabletop system did you get? Could you tell me how much you paid and the contact as I am wanting a tabeltop XRF setup.

Hi Gene,

I am not sure what you are wanting the XRF for? The XRF I have is advertised on the Internet as a Gold Testing Unit for around US$7000.00. I purchased direct from the Chinese. The model number is EXF7200.

The XRF comes with templates for quantitatively determining gold, silver, platinum and palladium. It will also detect other elements from Ti to Bi qualitatively. These can be identified by looking up their energies in the periodic table. I wrote my own templates for identifying the other elements. I might add an article on this XRF unit later.

Hi Bob,

Just a guess, but when I looked into these units a few years back, they used imported Amptek Peltier cooled diodes for the sensor. Most of the cost of these XRF's is likely those same diodes. Wish the Chinese would start manufacturing the things, then we might see a drop to several hundred rather than several thousand dollars.

Henry Barwood
Troy University
Troy, Alabama USA

Hi Henry,

Yes, they have several models, some of which use the Amptek Peltier Cooled Diode. The lower cost XRF's use gas proportional counters as the detector. The major cost would be the detector and x-ray tube.



Edited 2 time(s). Last edit at 06/27/2011 12:27AM by Bob Rock.