Can anyone please advise where I can purchase a chalcocite standard from?
Many thanks!
Hi Jeff,
Are you intending this standard for major element (Cu and S) characterization or as a trace element (blank) standard?
In other words do you need it certified for trace elements or not? I ask because I tested a number of natural single crystal pyrite standards from the UC Berkeley collection some years ago and found that so far as Fe and S are concerned, they were all the same within a fairly high precision. And when we ran AA on them, the trace elements were all less than 10 PPM or so.
I'm intending this standards for only Cu and S measurements.
Hi Jeff,
Well in that case you would be just fine with pure Cu and pyrite (FeS2) for S. The matrix corrections for these are minimal so there is no need to "matrix match" your standard and unknown.
How can one tell this, you might ask? See below.
Here is CuS2 calculated from pure elements using CalcZAF (I just entered the formula into the Enter Composition As Formula String button dialog...)
Current Mass Absorption Coefficients From:
LINEMU Henke (LBL, 1985) < 10KeV / CITZMU > 10KeV
Z-LINE X-RAY Z-ABSOR MAC
Cu ka Cu 5.0035e+01
Cu ka S 8.9734e+01
S ka Cu 1.4765e+03
S ka S 2.6132e+02
ELEMENT ABSFAC ZEDFAC FINFAC STP-POW BKS-COR F(x)e
Cu ka 1.0102 4.5717 4.6184 .2042 .9334 .9899
S ka 1.0740 3.9498 4.2421 .2289 .9041 .9311
SAMPLE: 32767, ITERATIONS: 0, Z-BAR: 22.47037
ELEMENT ABSCOR FLUCOR ZEDCOR ZAFCOR STP-POW BKS-COR F(x)u Ec Eo/Ec MACs
Cu ka 1.0033 1.0000 1.0985 1.1021 1.1230 .9782 .9866 8.9790 1.6706 69.9750
S ka 1.1778 1.0000 .9370 1.1035 .8964 1.0452 .7906 2.4720 6.0680 866.155
ELEMENT K-RAW K-VALUE ELEMWT% OXIDWT% ATOMIC% FORMULA KILOVOL
Cu ka .00000 .45160 49.772 ----- 33.333 .333 15.00
S ka .00000 .45516 50.228 ----- 66.667 .667 15.00
TOTAL: 100.000 ----- 100.000 1.000
Note that both the Cu Ka and S ka lines have about a 10% matrix correction (see the ZAFCOR column). Here's the same calculation for FeS2:
Current Mass Absorption Coefficients From:
LINEMU Henke (LBL, 1985) < 10KeV / CITZMU > 10KeV
Z-LINE X-RAY Z-ABSOR MAC
Fe ka Fe 6.8270e+01
Fe ka S 1.7255e+02
S ka Fe 1.0951e+03
S ka S 2.6132e+02
ELEMENT ABSFAC ZEDFAC FINFAC STP-POW BKS-COR F(x)e
Fe ka 1.0157 4.3900 4.4588 .2087 .9161 .9846
S ka 1.0740 3.9498 4.2421 .2289 .9041 .9311
SAMPLE: 32767, ITERATIONS: 0, Z-BAR: 20.65489
ELEMENT ABSCOR FLUCOR ZEDCOR ZAFCOR STP-POW BKS-COR F(x)u Ec Eo/Ec MACs
Fe ka 1.0116 1.0000 1.0757 1.0882 1.1023 .9758 .9733 7.1120 2.1091 124.011
S ka 1.1115 .9978 .9520 1.0559 .9217 1.0329 .8377 2.4720 6.0680 649.431
ELEMENT K-RAW K-VALUE ELEMWT% OXIDWT% ATOMIC% FORMULA KILOVOL
Fe ka .00000 .42777 46.549 ----- 33.333 .333 15.00
S ka .00000 .50623 53.451 ----- 66.667 .667 15.00
TOTAL: 100.000 ----- 100.000 1.000
Note the corrections are a little smaller in this case.
Of course if you use FeS2 as your sulfur standard, you'll have almost a matrix match with your CuS2 unknowns and therefore the correction for S Ka will be even smaller.
john