EPMA standard for thallium

[emma_fisi]

Hi everyone,

One of my users would like to measure the thallium content in a sulfide. There's likely to be several weight percent Tl present, not trace amounts. Does anyone out there have an appropriate standard material they would recommend? I have seen some comments about thallium bromides and iodides - does anyone have experience with how beam-stable these are? Also, it appears there are some toxicity issues with thallium - does anyone out there who has prepared thallium standards have any advice about minimizing risks?

Thanks,
Em

[Probeman]

One of my users would like to measure the thallium content in a sulfide. There's likely to be several weight percent Tl present, not trace amounts. Does anyone out there have an appropriate standard material they would recommend? I have seen some comments about thallium bromides and iodides - does anyone have experience with how beam-stable these are? Also, it appears there are some toxicity issues with thallium - does anyone out there who has prepared thallium standards have any advice about minimizing risks?

Thallium is very toxic, especially the salts. When Ian Carmichael was a grad student he was picking grains under a binocular scope that had been separated using a Tl heavy liquid. Unfortunately he was licking the brush to get the grains to stick to the brush and within a few weeks all his hair fell out!

Back in the day I got a Thallium compound from Claudio Cermignani (retired) which was useful. Here is what he sent me:

St  829 Tl(Br,I)
TakeOff = 40.0  KiloVolt = 15.0  Density =  7.371  Mount = alkali

From Claudio Cermignani (U of Toronto)
TlI-Tl-Br mixture
XRF analysis by M. Gordon 
(75% total, recalculated to 100%)
Approx. half of Fe is machine blank
Elemental Composition

Average Total Oxygen:         .000     Average Total Weight%:   99.957
Average Calculated Oxygen:    .000     Average Atomic Number:   67.606
Average Excess Oxygen:        .000     Average Atomic Weight:  142.523
Oxygen Equiv. from Halogen:  2.749

ELEM:       Tl       I      Br      Na      Mg      Si       P       S
XRAY:      ma      la      la      ka      ka      ka      ka      ka 
ELWT:   61.441  25.828  11.197    .966    .060    .083    .008    .075
ATWT:  204.370 126.904  79.904  22.990  24.305  28.086  30.974  32.064
KFAC:    .5521   .2260   .0777   .0040   .0003   .0006   .0001   .0007
ZCOR:   1.1129  1.1430  1.4405  2.3910  1.7801  1.3232  1.1830  1.0290
AT% :   42.866  29.019  19.980   5.991    .352    .421    .037    .334

ELEM:        K      Ca      Fe      Zn      Ga
XRAY:      ka      ka      ka      ka      ka 
ELWT:     .110    .130    .025    .017    .017
ATWT:   39.102  40.080  55.847  65.370  69.720
KFAC:    .0010   .0013   .0003   .0002   .0002
ZCOR:   1.1027  1.0013   .8503   .7800   .8129
AT% :     .401    .462    .064    .037    .035

[emma_fisi]

Thanks for the reply (and also yikes! I will make sure my user is not doing anything similar during his sample preparation....)