S1
Supporting Information for:
Quantification of rare earth elements using cloud point extraction with diglycolamide and ICP-MS for environmental analysis
Charles Labrecquea, and Dominic Larivièrea†
a Laboratoire de radioécologie, Département de chimie, Université Laval, 1045 Avenue de la Médecine, Québec, QC, Canada, G1V 0A6
† To whom correspondence should be addressed:
E-mail: [email protected]
Département de chimie, Faculté des sciences et de génieUniversité Laval1045, avenue de la Médecine, Bureau 1250DPavillon Alexandre-VachonQuébec, QC, Canada G1V 0A6 Phone: 418-656-7250 Fax : 418-656-7916E-Mail: [email protected]
Content
1. Soil digestion S2
2. Fusion protocol S3
3. Cloud Point Extraction protocol S4
4. Equations used S5
5. Extraction behavior for all REEs S7
Electronic Supplementary Material (ESI) for Analytical Methods.This journal is © The Royal Society of Chemistry 2014
S2
Soil digestion
The soil solutions were prepared using fluxer digestion (0.5 g of soil was
dissolved in 3.4 g of flux) for soil and sediment. For solid matrices that contained
high amounts of iron, such as red sludge, a mixture of lithium metaborate,
LiMBO2, and lithium tetraborate, LiTBO2 (in a ratio of 0.3 g of red sludge with
1.5 g of LiMBO2 and 1.5 g LiTBO2) was used.
The fluxes were purchased from Corporation Scientifique Claisse and are
composed of ultrapure lithium metaborate:lithium bromide (98.5:1.5) and lithium
tetraborate:lithium bromide (99:1). (Bouchard, M., Rivard, S., Ness, S. ISO 9516-
1 Simplified Borate Fusion & WDXRF Analytical Method for Iron Ores Analysis
Including Exploration Samples; Technical Report from Corporation Scientifique
Claisse: Quebec, QC, 2013)
Lithium bromide was added to prevent the flux from sticking to the crucibles. A
revised method (Table S1) from the protocol, as suggested by the M4 fluxer
manufacturer, was used throughout the experiments. The fluxer parameters used
allowed the complete and stable dissolution of solid environmental matrices in
3 M HNO3, and the samples remained stable for weeks following fusion. The
parameters remained the same regardless of the flux mixture used.
To facilitate cloud point extraction, the solutions were treated with PEG-6000 to
eliminate the silica in solution. (Dai, X.; Kramer-Tremblay S. Health Phys. 2011,
101, 144-147.) The silica was eliminated for instrumental reasons, i.e., to limit the
ICP-MS nebulizer clogging and to ease the surfactant rich phase (SRP)
redispersion.
S3
Fusion ProtocolTable S1 : Fusion protocol used for the dissolution of environmental samples
Function Steps Time (min)
Proposed Protocol
0 Pre-heating 00:051 Oxidation 00:302 First dissolution 00:303 Cooling –4 Heating 01:005 Final dissolution 03:006 Cooling -7 Pouring 00:108 Stirring 10:00
Total 15:15
S4
CPE conditions
Table S2: Optimised CPE system conditions
Parameter Condition Unit
Sample 6.5 mL
[HNO3] 0.1-2 M
[TTX-114] 1.07 mmol L-1
[DGA] 165 µmol L-1
[CTAB] 100 µmol L-1
[KBr] 10 mmol L-1
[KBrO3] 1,5 mmol L-1
Textraction 4 °C
Tphase separation 20 °C
RCFaverage 4 700 G
S5
Equations used
The method’s figures of merit were calculated using the following equations. The
principal parameters evaluated were: extraction efficiencies, chemical recovery,
detection limits, and quantification limits. The chemical recovery (CR, %) was
determined using the following equation, proposed in a previous report
(Labrecque, C. et al. Anal. Chem. 2013, 85, 10549-10555.):
𝐶𝑅 =𝐶𝑆𝑅𝑃𝑥 𝑉 𝑆𝑅𝑃 𝑟𝑒𝑑𝑖𝑠𝑝
𝐶𝑠𝑝𝑖𝑘𝑒𝑑𝑥 𝑉 𝑆𝑝𝑖𝑘𝑒𝑑× 100 𝐸𝑞.1
where CSRP redisp is defined as the concentration found in the surfactant-rich phase,
Cspiked is the spiked concentration, VSRP redisp is the volume (analysed) of the SRP,
and Vspiked is the spiked volume.
The equations were slightly modified from the previous report as the chemical
recoveries were done with alpha spectrometry instead of ICP-MS, hence the
measured properties are different and required different data analysis.
The extraction efficiencies (EE, %) were calculated using the following equation,
proposed in a previous report (Labrecque, C. et al. Talanta 2013, 107, 284-291.),
based on the equations of Favre-Réguillon et al. (Favre-Reguillon, A. et al.
Talanta 2004, 63, 803-806.)
𝐸𝐸 =𝐶𝑆𝑅𝑃 𝑟𝑒𝑑𝑖𝑠𝑝
𝐶𝑆𝑅𝑃 𝑟𝑒𝑑𝑖𝑠𝑝 + 𝐶𝑠𝑢𝑝𝑒𝑟𝑛𝑎𝑡𝑎𝑛𝑡×
𝑉𝑠𝑢𝑝𝑒𝑟𝑛𝑎𝑡𝑎𝑛𝑡
𝑉𝑆𝑅𝑃 𝑟𝑒𝑑𝑖𝑠𝑝 𝐸𝑞.2
where CSRP redisp and VSRP redisp are the same as defined above, whereas Vsupernatant
and Csupernatant represent the volume and concentration in the isolated
supernatant after the extraction, respectively.
S6
The preconcentration factor (PF) was determined using the following equation
reported in a previous communication:
𝑃𝐹 =𝐶𝑖𝑛𝑖𝑡𝑖𝑎𝑙𝑉𝑖𝑛𝑖𝑡𝑖𝑎𝑙 ‒ 𝐶𝑠𝑢𝑝𝑒𝑟𝑛𝑎𝑡𝑎𝑛𝑡𝑉𝑠𝑢𝑝𝑒𝑟𝑛𝑎𝑡𝑎𝑛𝑡
𝐶𝑠𝑢𝑝𝑒𝑟𝑛𝑎𝑡𝑎𝑛𝑡𝑉𝑠𝑢𝑝𝑒𝑟𝑛𝑎𝑡𝑎𝑛𝑡 𝐸𝑞.3
Vsupernatant and Csupernatant are the same as defined above and Cinitial and Vinitial are
the concentration and volume prior to the extraction, respectively.
S7
Figure S1 a) Influence of various parameters [a) nitric acid, b) hydrochloric acid,
c), ligand d) TTX-114 e) KBrO3 and f) CTAB concentrations] on the extraction of
REEs with other parameters being kept constant (at the concentration shown in
Table S4), using nitric acid.