Boron element is widely distributed in different geologic bodies, and there are important geo-chemical applications in earth science. Halite is a common mineral found in sediment basin. However there is no good method to accurately measure the boron content in halite, which is mainly because Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) and Inductively Coupled Plasma Mass Spectrometer (ICP-MS) are limited by the high salt matrix interference and the instrument detection limit. Thus enriching the boron element and removing the matrix interference are necessary before the measuring. In this paper, Amberlite IRA 743 boron-specific resin was applied to enrich the boron element and remove most of the high-salt matrix. The strong acid cation resin (Dowex 50 W×8, 200-400 mesh, USA) and weak-base anion resin (Ion Exchanger II, Germany) were mixed with equal volume, which could remove the foreign ions completely: meanwhile, the relative content of boron in the solution reached above 98%, and the recoveries ranged from 97.8% to 104%. 208.900 nm was chosen as the detection wavelength for ICP-OES, and the detection identification and quantification limits were 0.006 mg·L−1 and 0.02 mg·L−1, respectively. 11B was chosen as the measuring element for ICP-MS, and the detection identification and quantification limits were severally 0.036 mg·L−1 and 0.12 mg·L−1. The relative standard deviations ranged from 1.4% to 3.4% through six replicates under different salinities. Therefore, the process could be regarded as a feasible method to measure boron content in halite by ICP-OES and ICP-MS.
The boron is a strongly incompatible element in the earth [
Because of the high sensitivity and rapid analysis, the ICP-MS and ICP-OES are good methods for measuring the boron content in different minerals, such as coal, quartz, and other geochemical samples [
Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES, ICAP 6500 DUO, Thermo Electron): RF power was 1150 W; flux of cooling air was 15 L·min−1; flux of auxiliary air was 0.5 L·min−1; flux of carrying-air was 0.55 L·min−1; pump speed was 60 r·min−1; observation way of plasma was automatic.
Inductively Coupled Plasma Mass Spectrum (ICP-MS, X series 2 type, Thermo Electron): RF power was 1250 W; flux of cooling air (Ar) was 12.0 L·min−1; flux of auxiliary was 0.75 L·min−1; atomizer flow (Ar) was 0.85 L·min−1; measuring method was peak jumping with 11B.
Boric acid solid (H3BO3, GR) and sodium chloride solid (NaCl, GR) were made in Beijing Reagent Factory. Balanced hydrochloric acid was made from concentrated hydrochloric acid (GR): sub-boiling ammonia. Deionized water was made through multiple distillation and then the boron was removed by Amberlite IRA 743 type boron-specific resin made in American Rohm & Hass Company. It contains hydrophobic styrene skeleton and tertiary amine group and can strongly adsorb borate anion from alkaline solution with an exchange capacity of 10.9 mg B•g−1 [
Natural Samples: natural salt samples came from ZK309 Drill Hole, Long-hu Diggings, Laos (ZK-03, ZK-04, ZK-10), and salt lake in Pakistan (KR03-2, BS01-2, KS05).
Prepare a standard solution of 10 mg·L−1 boron, and then use it and NaCl to make a series of mixtures with boron content from 10
For numbers ZK-03, ZK-04, ZK-10, KR03-2, BS01-2, and KS05, weight 5.0 g halite and dissolve them into 50 mL deionized water. Remove the high-salt matrix and enrich the boron element using the above method.
The recovery of boron in the pure solutions ranged from 97.6% to 102.34% (Table
The recoveries of boron in pure solutions.
Total amount of boron / | Total recovery amount of boron / | Recovery /% | |
---|---|---|---|
10 | 9.76 | 97.6 | ICP-OES |
30 | 30.27 | 100.9 | |
50 | 49.60 | 99.20 | |
70 | 71.64 | 102.34 | |
| |||
10 | 10.2 | 102 | ICP-MS |
30 | 30.0 | 100 | |
50 | 49.4 | 98.8 | |
70 | 70.3 | 100.4 |
The relationship of measuring value by ICP-OES and ICP-MS. The lines of actual values were consistent with the theoretical line of 1:1 which showed that the values measured by ICP-OES were the same as those by ICP-MS.
The recoveries of boron in solutions under different salinities ranged from 99.95% to 103.3% (Table
The recovery results of boron in different salinities.
The content of | amount of boron / | Measuring by ICP-OES | Measuring by ICP-MS | Recovery | Recovery for ICP-MS % |
---|---|---|---|---|---|
500 | 40 | 4.053 | 4.132 | 101.33 | 103.3 |
5000 | 40 | 4.112 | 4.023 | 102.8 | 100.57 |
50000 | 40 | 4.181 | 3.998 | 104.5 | 99.95 |
The recovery of additional standard of the natural halite (ZK-04, ZK-10) ranged from 98.8% to 106.00% (Table
The recovery additional standard for natural sample.
Sample number | Measuring method | Boron content of original solution | The amount of addition standard / | Boron content of additional standard solution mg⋅L−1 | Recovery additional |
---|---|---|---|---|---|
ZK-04 | ICP-OES | 1.029 | 10 | 2.089 | 106.00 |
ICP-MS | 1.075 | 10 | 2.129 | 105.40 | |
| |||||
ZK-10 | ICP-OES | 0.832 | 10 | 1.82 | 98.8 |
ICP-MS | 0.803 | 10 | 1.842 | 104.2 |
In order to discuss the separating effect between boron element and foreign ions, three natural samples and four synthetic brines were processed based on the above method. The amounts of foreign ions were measured, whose results (Table
The separation effect by boron-special resin and mixed resins.
Sample | The amount of ions / | Total amount of | The amount of boron / | The relative content /% | |||
Na+ | Li+ | Mg2+ | Cl- | ||||
| |||||||
Big Qaidam | 0.2 | 0 | 0.08 | 0.13 | 0.41 | 24.3 (24.1) | 98.3(98.3) |
Inter-crystalline Brine | 0.26 | 0.45 | 0.04 | 0.32 | 1.07 | 48.6(48.3) | 97.9(97.8) |
Lake water | 0.17 | 0 | 0.05 | 0.25 | 0.47 | 14.9(15.1) | 97.0(96.98) |
Synthetic brine | 0.08 | 0 | 0.02 | 0.1 | 0.2 | 17.6(17.5) | 98.9(98.87) |
Brine-500 | 0.1 | 0 | 0 | 0.3 | 0.4 | 40.85(40.3) | 99.0(99.02) |
Brine-5000 | 0.2 | 0 | 0 | 0.4 | 0.6 | 41.25(40.9) | 98.57(98.55) |
Brine-50000 | 0.3 | 0 | 0 | 0.7 | 1.0 | 41.58(40.7) | 97.65(97.6) |
Take the deionized water through the entire process as a blank solution. Perform 11 consecutive measurements, and define 3 times standard deviation of the measurement results as the detection identification, 2 times the detection identification as the identification limit, and 10 times the standard deviation as the quantification limit for boron element [
The detection identification and quantification limits.
Method | Wavelength | Average content | SD | RSD | detection identification | identification limit | quantification limit |
---|---|---|---|---|---|---|---|
ICP-OES | 208.900 | -0.002 | 0.002 | 3.6 | 0.006 | 0.012 | 0.02 |
| |||||||
analytical isotope | Average content | SD | RSD | detection identification mg⋅L−1 | identification limit mg⋅L−1 | quantification limit | |
| |||||||
ICP-MS | 11B | 0.003 | 0.012 | 2.8 | 0.036 | 0.072 | 0.12 |
Repeatedly test solutions at different salinities 6 times, whose results which were showed in Table
Repeated results under different salinities.
number | Na+ 500 mg⋅L−1 | Na+ 5000 mg⋅L−1 | Na+ 50000 mg⋅L−1 | |||
---|---|---|---|---|---|---|
By ICP-OES | By ICP-MS | By ICP-OES | By ICP-MS | By ICP-OES | By ICP-MS | |
1 | 4.417 | 4.374 | 4.231 | 4.500 | 4.387 | 4.407 |
2 | 4.165 | 4.357 | 4.408 | 4.396 | 4.208 | 4.385 |
3 | 4.363 | 4.246 | 4.336 | 4.626 | 4.547 | 4.677 |
4 | 4.255 | 4.334 | 4.249 | 4.413 | 4.227 | 4.743 |
5 | 4.425 | 4.275 | 4.438 | 4.369 | 4.468 | 4.646 |
6 | 4.437 | 4.385 | 4.365 | 4.325 | 4.556 | 4.458 |
average value | 4.344 | 4.329 | 4.338 | 4.438 | 4.440 | 4.553 |
SD | 0.11 | 0.06 | 0.08 | 0.11 | 0.15 | 0.15 |
RSD (%) | 2.5 | 1.4 | 1.8 | 2.5 | 3.4 | 3.3 |
The boron contents of natural samples which were showed in Figure
The boron content of natural halite.
The boron-specific resin could significantly enrich the boron in high-salt solution and remove the matrix, which is suitable for the detection of the boron content of halite by ICP-OES and ICP-MS, whose standard addition recovery ranged from 97.5% to 106.0, and the relative standard deviations of the repeated experiments were less than 5%.
The data used to support the findings of this study are included within the article.
The authors declare that they have no conflicts of interest.