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Cathode-ray-excited emission spectroscopic analysis of trace rare earths
Andyltcct C/:~tnrcaActa Elscvier
Publishing
Conlpally,
393
\mstcrclan1
Prmtcdin The Netherlands
CATHODE-RAY-EXCITED ER;ZISSION OF TRACE RARE EARTHS 1'AlCT IV. T~E’1’ERivTINATlON
SIJECTROSCOPIC
OF -l’HUI_.LUM
IN
ZINC
ANALYSIS
SULFIDE
Cathode-ray-excited emlsslon qxctroscopy of rare earths IS a rapid, nondestructive analytical procedure, which can be utlllzed for quahtatlvc or quantitative analyses for trace amounts in certain matxlces Previous papers m this series have establlslled the quahtatlve aspect of this techmquel, and determmatlons of europium” and of terbtum” have also been reported. This paper descrlbcs the determlnatmn of trace amounts of thuhum rn zinc sulfide, the f-f emission line at 478 nm being used for the analysis. Zmc sulfide phosphors doped with rare earths have been known for many years ; the luminescence emission from such materials usually consists of broad bands, upon which are supcrmlposed lmes. In 1963 GOLIXMITH et al.4 found that lummesccnce excited from many rare earths In zmc sulfide by an ax. field need not be accompanied by broad-band emission, and m 1965 Yoco~ AND LARACH~ reported the effect of alkali metal charge compensation m minimizing the broad-band emission from rare earths rn zmc sulfide The effect of such compensators has been discussed by ~AIrncH" for rare earths m Group II-VI compouncls, and in the case of thultum, It was found that litlnum served to enhance the emission, particularly in the visible region of tlie spectrum. For this rca\on, lithium was used as a charge-compensating ion m the present materials ESI’HRIhIEN’lRL
The matrls material used m the preparation of all samples was “lummescent grade” zmc sulfide, deslgnatcd as RCA 33-%-x9 Slurries were made with distilled water, and the doping ions were added a5 aqueous sulfate solutions. Crystallization firmgs were carried out m Vltreosll fused quartz vessels, which were prefired with pure zinc sulfide. The firing atmosphere was hydrogen sulfide. To improve sample uniformity, firings were carried out m the apparatus shown in Fig. IA. The firing tube was preflushed by passing the hydrogen sulfide through the inlet tube. During the firing, the gas flow was shunted through the cap of the firing tube, thus mamtaining a posrtlve pressure of hydrogen sulfide m the tube, while flow around the sample was avoided. The samples were fired at 800~ for 15 mm, and at 1100~ for 45 min. * At the Dcpnrtmcnt of Physics and Dcpartmcnt Ncbrcw Unlvcr srty of Jerusakm, Israel, I g69-1970
of Inoqpnlc
and AnaIytwxI
AY?tnZChtlw
Chcmlstry.
the
Aclrt, 51 (rg70) 393-398
S.
394
LRRACH,
R.
E.
SHRADER,
R.
A.
KAUFFIJNGER
Thulium in zmc sulfide showed detectable luminescence emission at or above firing temperatures of 800’ and Table I shows the cathode-ray-excited intensity as a function of firing temperature, for one composition. With the low rare-earth content investigated in thus work, rt was found that sequcntral frrmgs introduced expected varrations from run to run. For this reason, a multiple sample holder was designed, shown in Fig 113, whrch allowed six samples to be fired srmultaneously in the same ambience. Sample mixes in each firing were repeated in subsequent firings, thereby provrdmg a metlrod of normalrzing the varrous fn-mgs
--GAS
OUTLET
-GROUND
QUARTZ
JOINT
WOOL
I
SIDE VIEW MULTIPLE HOLDER
OF SAMPLE
MULTIPLE SAMPLE OLDER WITH OVER PLATE
A
e
FIN I App:~mius sa1111a! holclcr
for f~rrng sanq>lcs
for analysts
(A)
VICWof
apparatus,
(B)
SIC~CVICW of multqdc
As m the prevrous work, a “demountable” cathode-ray tube was used. Demountable refers to the tube’s capability of being repeatedly opened to the atmosphere electron-gun structures and windowfor the purpose of changing test-samples, material (quartz, sapphire, etc.). Of special importance IS the capability of accommodatmg, at one pumping, all samples of one or more series to minimize the error from carrying over a standard from one pumping to another. The unit used here can handle 29 samples. The voltage applied to the beam is not particularly critical II Awd
Cha?,t. Ada,
51
(‘970)
393-398
SPJZCTROSCOPICDETERMINATION OF THULIUM IN ZINC SULFIDE
395
if one avoids low or hIgIl voltages (Z-E., 3 kV < V c 20 kV). The proper region of voltage also depends on the secondary emission characteristics of the material under test. For zinc sulfide, voltages zn the range S-12 kV are satisfactory. Electron beam currents also are not critlcal if one avoids high current densities (z.e., a defocused beam 1s used) and keeps the wattage-loading below some safe value (e g. IO mW cm-l). In these tests, a I-PA beam, focused to a r-mm dlarneter spot, was scanned over a test area, I0 x 20 mm2. The radiant flux to be studied can be introduced mto any type of monochromator for measuring with a detector suitable for the wavelength and intensity involved. A Spex grating monochromator (Model 1700) fitted with a # 7265 multiplier phototube was used m this instance. It was found desirable to scan the monochromator over a small range mcludmg the rare-earth line (i.e 470-4s~ nm) while recording the photocurrent (or detector output) to determine the amount of backObviously the rcsolutlon (or band-pass) should bc adequate ground luminescence to dlstingul5h the line emission from tllc background. Since the spectral character of the rare-cart11 emlsslon is quite mscnsltlve to concentration below IOO-goo p,p.m., one needs to read only a peak-height above background for each sample. Avallabillty of zero-offset for the background bcfole amphflcatlon is hcll~ful in providing accuracy when a weak line 1s superlmposecl on a strong background.
The visible emission from thulium m zinc sulfldc consists of two spectral complexes (manifolds) I’, the major being about 47o-485 nm, and the minor about 630-(X5 nm. The spectral dlstrlbutlon curves arc shown m Fig. 2.
r
I_---_-
-__---
-
-_
WAVELENGTH,
Fig
2
thulium
Catl~oclolumincscci~cc in zinc sulf~dc (Note
nm
qxxtral clldrllmtlon the earn chmgc )
curvc~
of
blue
ant1 reel einlbwon
bands
from
The cathodoluminescence emission intensity of the 47o-485-nm emlsslon from thulmrn as a function of concentration (between one and 300 p.p.b.) m zinc sulfide is shown in Fig. 3. A detection limit of 0.01 p.p.b. is indicated for this type of analysis. “Added-found” data are shown in Table II, for thulium prepared in a zinc /1?tnlCl~rnr
Ada,
51 (1970)
393-398
S. LARACH, R E. SHRADER, R. A. KAUFFUNGER
396
sulficle matrix. I;or ‘f~ found, two columns are given, one for cathode-ray-excited emission analysis (CRBE) and the other for solid-state mass spectrometry (SSiMS). The ma%sspectrometer was an AEI MS-?, equipped with an r.f. sparksource and photographic detection. The spark source was operated at 25 kV between the sample electrodes, at a repetition frequency of 300 Hz and a pulse duration of zoo psec. Positive ions from the spark were accelerated to 20 kV, passed through both an electrostatic and a magnetic analyzer, and collected on an Ilford Q-2 ion-sensttlve emulsion. The samples were mlxed I : I by wetgllt with high-purity silver powder, and were hrlquetted in a polyethylene-slug die to form solid, conducting electrodes.
bl
---
-_--
I
I
I THULIUM,
---_
IO PARTS-PER
_- ._--_-_--
I
I02 BILLION
_
The response of the ion-sensltlve plate was cahbrated with a series of platinum exposures by relating blackenmg on the plate to the total ion beam monitor, and fitting these data to an equation developed by HULL’. Thulium concentrations were calculated by comparmg the blackening for the leQl.rnt- ion to the total ion beam passing through the instrument. The agreement between the two sets of results is consistent within the accuracy of the measurements. A~cl. Ckhr. Acln, 51 (1970)
39+-398
SPECTROSCOPIC
DETERMINATION
OFTHULIUM
397
IN ZINC SULFIDE
Interferences
Interference effects caused by the presence of silver ion which itself promotes a blue catl~odolummescence emlsslonB, were investigated. Various concentrations of silver were incorporated into zinc sulfide contammg 5 p.p.m. of thuhum. This large thulium concentration was used to increase the accuracy of measurement for the case of large Interference. Any effect of interference observable at this concentration would be enhanced for lower concentrations. The results are shown in Fig. 4. It IS seen that silver ions begin to decrease the emission intensity from thulium at concentrations somewhat greater than one p.p m. At IO p p m., the silver 1011has decreased the thulium emission by a factor of about five, and a levellmg-off 1s indicated at about 50 p p m., where the residual thuhum emlsslon is only about zl>$ of the origmal
I 01
L
I
t
n,I*InI
I
t
,,,,,I
IO CONCENTRATION
(ppm)
Fig 4 I
I
1
IIlflc) I00
IO
intensity
OF
SILVER
)
Nd
&fE
IONS
.LSa functmn of conccntr,~tmi of thulium
Ce
d lx
of 5tllccr 111ant
(5 p p III ) 111ZII~Cwlfdc
Sm EAFZI
1 Gd
I 0~ ( Er Tb Ho
IONS
(iooppm)
sulfitlc contalnmg
5 p p In
as a function of r.wc earth inter-
The interference effects of twelve rare earths were also studied. The results of using loo-p.p.m amounts as interfermg ions in the analysis of 5 p p.m. of thuhum in zinc sulfide (hthium) are shown in Fig. 5 The slight general trend, with the exception of europlum, would appear to be decreasing emission intensity from thulium with increasing atomic number of the interfering rare earth. The relationship indicated prevrously3 (for terbium m an yttrium oxide matrix) between emission intensity and the magnetic moment of the rare-earth mterfering ion was not found for thulium in a zmc sulfide matrix. Whether or not tlus is due to the difference in matrix will be investigated in future work. The fact that with europium present as emission was detected from thulium, the interfermg Ion, IZO cathode-ray-excited may be connected with the fact that the europlurn m zinc sulfide ~sdivalent, asshown by e.p.r. investigations 9. Further work is planned to investigate tlus effect. The determination of thuhum by X-ray-excited fluorescence has been reported hmlt of IO p.p,m. in yttnum oxide, while by WALTERS et al. 10, with a detection OZAWA ANI) Tonvull reported a detection limtt m the region IO-~-IO-* mole, for each of several rare earths, including thulium, in yttrium oxide, utlhzing photoluminescence techniques.
who
The authors wish toacknowledge, obtained the mass spectrographic
with thanks, the aid of Dr. W. L. HARRINGTON, data. Anal.
Chum. Acta, 51 (1970) 393-398
398
S. LARACH,
R. E.
SHRADER,
R. A.
KAUFFUNGEII
The method of analysis for trace amounts of rare earths in a matrix by cathoderay-excited emlsslon spectroscopy has been extended to the detcrmmatlon of thulium m a zinc sulfide matrrx, with litlnum added as a charge-compensatmg ion. If the 47S-nm emission from thuhum is used as the detectlon wavelength, one p.p.b. can be leadlly determined, with an estimated detection limit of the order of 0.01 p p.b Thulium determinations by this means are compared with those from solid-state mass spectrometry. Effects of sample firmg paramctcrs and interferences are discussed
La m&llode d’analysc de traces de tcrrcs rares dans une matrice, par spectroscop~c d’Cmlssion ?Lrayon catl~ocliclue, a ht6 6tcndu au dosage clu thuhum dans une matrlcc de sulfurc clc zinc avec add&on de ltthlum ICn utllisant l’&nlsslon 478 nm clu thulium commc longueur d’onde de d&tectlon, il cst possible de doser facilemcnt I p.p.11., avec unc lnnite de d&ection de l’ordre de o OI p.p.1~. Les r&ultats de thulium ainsl obtenus son1 cornpar& h ceux de la spcctromirtric dc masse h 1’6tat solide. On examine divers paran&res et mterfdrences posslble~
Die Methode dcr Analyse von Seltcnerd-Spuren In emer Matrix durch Bmissions-- c-_ spektloslcople mlt I~athodetlstrahlanregul~g ist auf die Bestlmmung von Thulium in eincr Zinksulhd-Matrix erweltcrt worden, wobel Lttlnum als ladungskdmpenslerendes Ion zugegebcn wird. Als NachwciswellenlCmge wnd dlc Emission dcs Thuliums bcl 478 nm benutzt Em p p b. kann leicht bestimmt werden, die gcschYtzte Nachwcisgrenze he@ in der Grosscnordnung 0.01 p p.b. Thuliumbestimmungen nach dleser Metllode wcrden xnit den durch l’cstkcirper-Masscnspektrometrlc durchgefuhrten Uestimmungcn vergliclicn. Die IZinElusse clcr P~ol>envorbchancllung und Stcirungen werden cliskutiert.
Publishing
Conlpally,
393
\mstcrclan1
Prmtcdin The Netherlands
CATHODE-RAY-EXCITED ER;ZISSION OF TRACE RARE EARTHS 1'AlCT IV. T~E’1’ERivTINATlON
SIJECTROSCOPIC
OF -l’HUI_.LUM
IN
ZINC
ANALYSIS
SULFIDE
Cathode-ray-excited emlsslon qxctroscopy of rare earths IS a rapid, nondestructive analytical procedure, which can be utlllzed for quahtatlvc or quantitative analyses for trace amounts in certain matxlces Previous papers m this series have establlslled the quahtatlve aspect of this techmquel, and determmatlons of europium” and of terbtum” have also been reported. This paper descrlbcs the determlnatmn of trace amounts of thuhum rn zinc sulfide, the f-f emission line at 478 nm being used for the analysis. Zmc sulfide phosphors doped with rare earths have been known for many years ; the luminescence emission from such materials usually consists of broad bands, upon which are supcrmlposed lmes. In 1963 GOLIXMITH et al.4 found that lummesccnce excited from many rare earths In zmc sulfide by an ax. field need not be accompanied by broad-band emission, and m 1965 Yoco~ AND LARACH~ reported the effect of alkali metal charge compensation m minimizing the broad-band emission from rare earths rn zmc sulfide The effect of such compensators has been discussed by ~AIrncH" for rare earths m Group II-VI compouncls, and in the case of thultum, It was found that litlnum served to enhance the emission, particularly in the visible region of tlie spectrum. For this rca\on, lithium was used as a charge-compensating ion m the present materials ESI’HRIhIEN’lRL
The matrls material used m the preparation of all samples was “lummescent grade” zmc sulfide, deslgnatcd as RCA 33-%-x9 Slurries were made with distilled water, and the doping ions were added a5 aqueous sulfate solutions. Crystallization firmgs were carried out m Vltreosll fused quartz vessels, which were prefired with pure zinc sulfide. The firing atmosphere was hydrogen sulfide. To improve sample uniformity, firings were carried out m the apparatus shown in Fig. IA. The firing tube was preflushed by passing the hydrogen sulfide through the inlet tube. During the firing, the gas flow was shunted through the cap of the firing tube, thus mamtaining a posrtlve pressure of hydrogen sulfide m the tube, while flow around the sample was avoided. The samples were fired at 800~ for 15 mm, and at 1100~ for 45 min. * At the Dcpnrtmcnt of Physics and Dcpartmcnt Ncbrcw Unlvcr srty of Jerusakm, Israel, I g69-1970
of Inoqpnlc
and AnaIytwxI
AY?tnZChtlw
Chcmlstry.
the
Aclrt, 51 (rg70) 393-398
S.
394
LRRACH,
R.
E.
SHRADER,
R.
A.
KAUFFIJNGER
Thulium in zmc sulfide showed detectable luminescence emission at or above firing temperatures of 800’ and Table I shows the cathode-ray-excited intensity as a function of firing temperature, for one composition. With the low rare-earth content investigated in thus work, rt was found that sequcntral frrmgs introduced expected varrations from run to run. For this reason, a multiple sample holder was designed, shown in Fig 113, whrch allowed six samples to be fired srmultaneously in the same ambience. Sample mixes in each firing were repeated in subsequent firings, thereby provrdmg a metlrod of normalrzing the varrous fn-mgs
--GAS
OUTLET
-GROUND
QUARTZ
JOINT
WOOL
I
SIDE VIEW MULTIPLE HOLDER
OF SAMPLE
MULTIPLE SAMPLE OLDER WITH OVER PLATE
A
e
FIN I App:~mius sa1111a! holclcr
for f~rrng sanq>lcs
for analysts
(A)
VICWof
apparatus,
(B)
SIC~CVICW of multqdc
As m the prevrous work, a “demountable” cathode-ray tube was used. Demountable refers to the tube’s capability of being repeatedly opened to the atmosphere electron-gun structures and windowfor the purpose of changing test-samples, material (quartz, sapphire, etc.). Of special importance IS the capability of accommodatmg, at one pumping, all samples of one or more series to minimize the error from carrying over a standard from one pumping to another. The unit used here can handle 29 samples. The voltage applied to the beam is not particularly critical II Awd
Cha?,t. Ada,
51
(‘970)
393-398
SPJZCTROSCOPICDETERMINATION OF THULIUM IN ZINC SULFIDE
395
if one avoids low or hIgIl voltages (Z-E., 3 kV < V c 20 kV). The proper region of voltage also depends on the secondary emission characteristics of the material under test. For zinc sulfide, voltages zn the range S-12 kV are satisfactory. Electron beam currents also are not critlcal if one avoids high current densities (z.e., a defocused beam 1s used) and keeps the wattage-loading below some safe value (e g. IO mW cm-l). In these tests, a I-PA beam, focused to a r-mm dlarneter spot, was scanned over a test area, I0 x 20 mm2. The radiant flux to be studied can be introduced mto any type of monochromator for measuring with a detector suitable for the wavelength and intensity involved. A Spex grating monochromator (Model 1700) fitted with a # 7265 multiplier phototube was used m this instance. It was found desirable to scan the monochromator over a small range mcludmg the rare-earth line (i.e 470-4s~ nm) while recording the photocurrent (or detector output) to determine the amount of backObviously the rcsolutlon (or band-pass) should bc adequate ground luminescence to dlstingul5h the line emission from tllc background. Since the spectral character of the rare-cart11 emlsslon is quite mscnsltlve to concentration below IOO-goo p,p.m., one needs to read only a peak-height above background for each sample. Avallabillty of zero-offset for the background bcfole amphflcatlon is hcll~ful in providing accuracy when a weak line 1s superlmposecl on a strong background.
The visible emission from thulium m zinc sulfldc consists of two spectral complexes (manifolds) I’, the major being about 47o-485 nm, and the minor about 630-(X5 nm. The spectral dlstrlbutlon curves arc shown m Fig. 2.
r
I_---_-
-__---
-
-_
WAVELENGTH,
Fig
2
thulium
Catl~oclolumincscci~cc in zinc sulf~dc (Note
nm
qxxtral clldrllmtlon the earn chmgc )
curvc~
of
blue
ant1 reel einlbwon
bands
from
The cathodoluminescence emission intensity of the 47o-485-nm emlsslon from thulmrn as a function of concentration (between one and 300 p.p.b.) m zinc sulfide is shown in Fig. 3. A detection limit of 0.01 p.p.b. is indicated for this type of analysis. “Added-found” data are shown in Table II, for thulium prepared in a zinc /1?tnlCl~rnr
Ada,
51 (1970)
393-398
S. LARACH, R E. SHRADER, R. A. KAUFFUNGER
396
sulficle matrix. I;or ‘f~ found, two columns are given, one for cathode-ray-excited emission analysis (CRBE) and the other for solid-state mass spectrometry (SSiMS). The ma%sspectrometer was an AEI MS-?, equipped with an r.f. sparksource and photographic detection. The spark source was operated at 25 kV between the sample electrodes, at a repetition frequency of 300 Hz and a pulse duration of zoo psec. Positive ions from the spark were accelerated to 20 kV, passed through both an electrostatic and a magnetic analyzer, and collected on an Ilford Q-2 ion-sensttlve emulsion. The samples were mlxed I : I by wetgllt with high-purity silver powder, and were hrlquetted in a polyethylene-slug die to form solid, conducting electrodes.
bl
---
-_--
I
I
I THULIUM,
---_
IO PARTS-PER
_- ._--_-_--
I
I02 BILLION
_
The response of the ion-sensltlve plate was cahbrated with a series of platinum exposures by relating blackenmg on the plate to the total ion beam monitor, and fitting these data to an equation developed by HULL’. Thulium concentrations were calculated by comparmg the blackening for the leQl.rnt- ion to the total ion beam passing through the instrument. The agreement between the two sets of results is consistent within the accuracy of the measurements. A~cl. Ckhr. Acln, 51 (1970)
39+-398
SPECTROSCOPIC
DETERMINATION
OFTHULIUM
397
IN ZINC SULFIDE
Interferences
Interference effects caused by the presence of silver ion which itself promotes a blue catl~odolummescence emlsslonB, were investigated. Various concentrations of silver were incorporated into zinc sulfide contammg 5 p.p.m. of thuhum. This large thulium concentration was used to increase the accuracy of measurement for the case of large Interference. Any effect of interference observable at this concentration would be enhanced for lower concentrations. The results are shown in Fig. 4. It IS seen that silver ions begin to decrease the emission intensity from thulium at concentrations somewhat greater than one p.p m. At IO p p m., the silver 1011has decreased the thulium emission by a factor of about five, and a levellmg-off 1s indicated at about 50 p p m., where the residual thuhum emlsslon is only about zl>$ of the origmal
I 01
L
I
t
n,I*InI
I
t
,,,,,I
IO CONCENTRATION
(ppm)
Fig 4 I
I
1
IIlflc) I00
IO
intensity
OF
SILVER
)
Nd
&fE
IONS
.LSa functmn of conccntr,~tmi of thulium
Ce
d lx
of 5tllccr 111ant
(5 p p III ) 111ZII~Cwlfdc
Sm EAFZI
1 Gd
I 0~ ( Er Tb Ho
IONS
(iooppm)
sulfitlc contalnmg
5 p p In
as a function of r.wc earth inter-
The interference effects of twelve rare earths were also studied. The results of using loo-p.p.m amounts as interfermg ions in the analysis of 5 p p.m. of thuhum in zinc sulfide (hthium) are shown in Fig. 5 The slight general trend, with the exception of europlum, would appear to be decreasing emission intensity from thulium with increasing atomic number of the interfering rare earth. The relationship indicated prevrously3 (for terbium m an yttrium oxide matrix) between emission intensity and the magnetic moment of the rare-earth mterfering ion was not found for thulium in a zmc sulfide matrix. Whether or not tlus is due to the difference in matrix will be investigated in future work. The fact that with europium present as emission was detected from thulium, the interfermg Ion, IZO cathode-ray-excited may be connected with the fact that the europlurn m zinc sulfide ~sdivalent, asshown by e.p.r. investigations 9. Further work is planned to investigate tlus effect. The determination of thuhum by X-ray-excited fluorescence has been reported hmlt of IO p.p,m. in yttnum oxide, while by WALTERS et al. 10, with a detection OZAWA ANI) Tonvull reported a detection limtt m the region IO-~-IO-* mole, for each of several rare earths, including thulium, in yttrium oxide, utlhzing photoluminescence techniques.
who
The authors wish toacknowledge, obtained the mass spectrographic
with thanks, the aid of Dr. W. L. HARRINGTON, data. Anal.
Chum. Acta, 51 (1970) 393-398
398
S. LARACH,
R. E.
SHRADER,
R. A.
KAUFFUNGEII
The method of analysis for trace amounts of rare earths in a matrix by cathoderay-excited emlsslon spectroscopy has been extended to the detcrmmatlon of thulium m a zinc sulfide matrrx, with litlnum added as a charge-compensatmg ion. If the 47S-nm emission from thuhum is used as the detectlon wavelength, one p.p.b. can be leadlly determined, with an estimated detection limit of the order of 0.01 p p.b Thulium determinations by this means are compared with those from solid-state mass spectrometry. Effects of sample firmg paramctcrs and interferences are discussed
La m&llode d’analysc de traces de tcrrcs rares dans une matrice, par spectroscop~c d’Cmlssion ?Lrayon catl~ocliclue, a ht6 6tcndu au dosage clu thuhum dans une matrlcc de sulfurc clc zinc avec add&on de ltthlum ICn utllisant l’&nlsslon 478 nm clu thulium commc longueur d’onde de d&tectlon, il cst possible de doser facilemcnt I p.p.11., avec unc lnnite de d&ection de l’ordre de o OI p.p.1~. Les r&ultats de thulium ainsl obtenus son1 cornpar& h ceux de la spcctromirtric dc masse h 1’6tat solide. On examine divers paran&res et mterfdrences posslble~
Die Methode dcr Analyse von Seltcnerd-Spuren In emer Matrix durch Bmissions-- c-_ spektloslcople mlt I~athodetlstrahlanregul~g ist auf die Bestlmmung von Thulium in eincr Zinksulhd-Matrix erweltcrt worden, wobel Lttlnum als ladungskdmpenslerendes Ion zugegebcn wird. Als NachwciswellenlCmge wnd dlc Emission dcs Thuliums bcl 478 nm benutzt Em p p b. kann leicht bestimmt werden, die gcschYtzte Nachwcisgrenze he@ in der Grosscnordnung 0.01 p p.b. Thuliumbestimmungen nach dleser Metllode wcrden xnit den durch l’cstkcirper-Masscnspektrometrlc durchgefuhrten Uestimmungcn vergliclicn. Die IZinElusse clcr P~ol>envorbchancllung und Stcirungen werden cliskutiert.