Chalcocite standard (Cu2S)

[Jeff C.]

Can anyone please advise where I can purchase a chalcocite standard from?
Many thanks!

[Probeman]

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.

[Karsten Goemann]

We've got a chalcocite standard from Geller Microanalytical which seems fine, but we haven't tested it for trace elements yet.

[Jeff C.]

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.

[Jeff C.]

We've got a chalcocite standard from Geller Microanalytical which seems fine, but we haven't tested it for trace elements yet.

Thank you Karsten. I'll contact the supplier for details.

[Probeman]

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