Metal Quantifications by TXRF in Solution with Large Matrices

Transcription

1 Metal Quantificatins by TXRF in Slutin with Large Matrices Tm Vander Hgerstraete, Sfia Riañ, and Ken Binnemans

2 Outline Intrductin Results Research activities Equipment Imprving data quality (Nd) Measurements in large matrices Y measurements with a M X-ray surce Halide determinatin in slutin Expensive mistakes Cnclusins 2

3 Intrductin

4 Research activities Labratry f Inrganic Chemistry (KULeuven, Belgium) Head: Prf. K. Binnemans Research activities Separatin and purificatin f metals mainly by slvent extractin Critical metal recvery (e.g. NdFeB magnets, lamp phsphrs) Synthesis and extractin with (new) inic liquids Crdinatin chemistry 4

5 Research activities Inic liquids (ILs) are rganic salts that cnsist entirely ut f ins and have traditinally a melting pint belw 100 C Beneficial prperties fr extractin systems Negligible vapr pressure Nn flammable Often called greener slvents 5

6 Research activities 6

7 Equipment Metal quantificatin by TXRF 3 x S2 PICOFOX (Bruker) with M X-ray surce ± 500 samples every week Quartz disk Measurements Aqueus phase Pure Salty water (salt = matrix!) Organic phase (nt preferred) Vlatile (tluene) Nn-vlatile (inic liquid = matrix!) 7

8 Equipment TXRF uses calibratin factr (e.g. Nd vs Ga) We calibrate the TXRF nce every year (abut 30 elements in grups f 4 r 5 elements) Anyne shuld get the mst precise and accurate data need fr a standard prcedure By using standard slutins Accuracy Recvery rate (%), depends als n calibatin factr Relative standard deviatin, RSD (%) RSD % = i=1 N (x i x) 2 N 1 x 100% 8

9 Results

10 Imprving data quality (Nd) Influence f measuring time (vs cnstant number f cunts) 4 1 x 5 µl cntaining 100 mg L -1 Ga and 100 mg L -1 Nd Average cunt rate: 8500 cunts s -1 RSD (%) calculated n 3 measurements 3 TXRF1 TXRF2 series 1 TXRF2 series 2 RSD (%) Measurement time (s) 10

11 Imprving data quality (Nd) Rtatin f sample 3 x 5 µl cntaining 100 mg L -1 Ga and 100 mg L -1 Nd RSD (%) calculated n 6 rtatins f 60 degrees Sample RSD (%)

12 Imprving data quality (Nd) Optimal sample preparatin prcedure Drying time f 30 µl silicne il (1%) in isprpanl 5 x 10 samples 5 µl cntaining 100 mg L -1 Ga and 100 mg L -1 Nd Drplet residue becmes smaller when drying lnger Rm temperature RSD (%) C Drying time f silicne il in isprpanl (min)

13 Imprving data quality (Nd) Optimal sample preparatin prcedure Sample vlume (9 x 10 carriers at different times) 5 µl cntaining 100 mg L -1 Ga and 100 mg L -1 Nd Measurement time: 300 secnds Decrease prbably mainly due t the increased number f cunts 4 3 RSD (%) Sample vlume (ml) 13

14 Imprving data quality (Nd) Optimal sample preparatin prcedure Drying time f sample: measured at specific time intervals. 3 carriers 5 µl cntaining 100 mg L -1 Ga and 100 mg L -1 Nd t n = 0, 5, 10, 15, 30, 45, 60, 960 minutes (3 x 8 measurements) RSD values shwn at t n calculated n t n-1, t n and t n RSD (%) Drying time (min) 14 N trend, hwever, ne must be careful with drying times that are t shrt (see later)

15 Imprving data quality (Nd) Optimal sample preparatin prcedure Results btained with ptimized sample preparatin prcedure as functin f the day and the peratr 3 x 10 carriers 5 µl cntaining 100 mg L -1 Ga and 100 mg L -1 Nd Calibratin factr calculated based n average f the 30 measurements Day/peratr Recvery rate (%) RSD (%) 1/ / /

16 Imprving data quality (Nd) Linear calibratin line? 100 mg L -1 Ga, changing Nd cncentratin RR (%) Nd cncentratin mg L -1 Recvery rates (%) f sme selected elements after calibratin. Ga cncentratin = 100 mg L -1 Cnc. Gd Er Ni Pr C

17 Measurements in large matrices Optimal sample preparatin prcedure A matrix f ther elements E.g. 100 ppm f Ga, Nd, Ni, As, In 10 samples RSDs fr Nd between 3 and 10% can be significant higher 250 cps Ar In Nd Ni Ga As kev -

18 Measurements in large matrices Optimal sample preparatin prcedure Overlapping peaks (e.g. Pr, Nd and Ga), L lines f Pr disappear belw thse f Nd shulders Keep cncentratin f Nd cnstant (100 mg L -1 ), the rati Pr/Ga = 1 and decrease Pr cncentratin Nd RR (%) Nd/Pr cncentratin rati

19 Measurements in large matrices Measurement in inic liquids Cyphs IL 101 chlride, 100 mg L -1 Ga, 100 mg L -1 Ln, 200 µl H 2 O and diluting with ethanl t 1 ml) Nd Pr 80 RR (%) v% IL in ethanl/water 19

20 Y measurements with a M X-ray surce 14 cps Y Y M M kev - 20

21 Y measurements with a M X-ray surce Cunts(Ga) x Cnc(Y) / Cnc(Ga) Slpe = Slpe = Cunts(Y) 21

22 Halide determinatin in slutin Mst internal standards are acidic (HNO 3 ) Gives vlatile HX cmpunds in cmbinatin with disslved halides MX n + nhno 3 M(NO 3 ) n + nhx HX evaprates during drying prcedure Adding NH 3 t acidic cpper standard Cu(NO 3 ) 2 + 4NH 3 Cu(NH 3 ) 4 (NO 3 ) 2 Stable standard in alkaline cnditins 22

23 Halide determinatin in slutin Ideal calibratin curve Alkaline standard made frm Cu(NO 3 ) 2 salt Alkaline standard made frm acidic standard Measured [Cl] (ppm) Uncntrllable Expected [Cl] (ppm) Be careful in cmbinatin with metals (hydrlysis) Cl = light element high RSD Effects are less prnunced fr Br and I (lwer vlatility f acids) Vander Hgerstraete, T., Jamar, S., Wellens, S., Binnemans, K. (2014). Analytical Chemistry, 86 (3), Vander Hgerstraete, T., Jamar, S., Wellens, S., Binnemans, K. (2014). Analytical Chemistry, 86 (8),

24 Expensive mistakes Detectr crrsin Detectr is placed very clse t the sample Imprper drying?.

25 Expensive mistakes Cleaning f quartz carriers in tefln hlders If slutin cmpletely evaprates increasing temperature decmpsitin f tefln t HF crrsin f quartz carriers.

26 Expensive mistakes Cleaning f quartz carriers in tefln hlders If slutin cmpletely evaprates increasing temperature decmpsitin f tefln t HF crrsin f quartz carriers.

27 Cnclusins

28 Cnclusins Sample preparatin is crucial fr btaining high quality data Significant matrix effects when using a standard with X-ray energies that are nt clse t X-ray energies f the element f interest Halides in slutin can be measured by adding NH 3 t a cpper internal standard.

29 Acknwledgement Prf. K. Binnemans Sfia Rian.