My samples salinity is less or more 300 g/L. I would like to determine especially the concentration of trace elements which should be around 30 to 90 ppm. The issue is with dilution the initial content will be ppb or ppt and it will not be on the detection range of the ICP machine.
Ask ChatGPT about it. His answer gives a good general overview. Then look for information materials (application notes, etc.) from various manufacturers of ICP spectrometers (emission and mass), available for download from their websites. A Google query gave, for example:
https://www.researchgate.net/publication/344872875_Determination_of_Major_Elements_in_Saline_Water_Samples_Using_a_Dual-View_ICP-OES
https://www.researchgate.net/publication/282524464_Determination_of_trace_elements_in_salt_lake_brines_using_inductively_coupled_plasma_optical_emission_spectrometry_after_magnesium_hydroxide_precipitation
Determination of trace elements in salt lake brines using inductively coupled plasma optical emission spectrometry after magnesium hydroxide precipitation October 2015 Analytical Methods 7(19) DOI: 10.1039/C5AY01971K
ICP-OES determination of trace elements in salinated water samples November 1999Atomic Spectroscopy 20(6):217-223
https://www.horiba.com/int/scientific/applications/environment/pages/brine-analysis-with-the-ultima-expert-icp-oes/
https://citeseerx.ist.psu.edu/document?repid=rep1&type=pdf&doi=e89792957814290270c1a163cd374db4aa560219
https://www.analytik-jena.fr/fileadmin/content/pdf_analytical_instrumentation/ICP/ICP-OS/AppNote_PQ9000_DirectAnalysis_Saline_Matrices_en.pdf
https://pearl.plymouth.ac.uk/bitstream/handle/10026.1/1781/HOWARD_WILLIAM_HANDLEY.PDF?sequence=1&isAllowed=y
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4522618/
https://img42.chem17.com/5/20090727/633843088643281250.pdf
https://www.usgs.gov/labs/brine-research-instrumentation-and-experimental-laboratory/capabilities
https://www.usgs.gov/publications/direct-trace-element-determination-oil-and-gas-produced-waters-inductively-coupled
https://link.springer.com/article/10.1007/s00126-023-01173-z
https://www.agilent.com/cs/library/applications/application-li-brine-icp-oes-5800-5994-5149en-agilent.pdf
https://hal.univ-lorraine.fr/hal-03360101/document
http://www.gpxygpfx.com/EN/abstract/abstract12020.shtml#
https://doi.org/10.18273/revbol.v45n2-2023005
And many others
ZJ
You may be able to selectively exchange the ions of interest onto a resin and recover them for measurement, or preferably, to separate chromatographically followed by measurement online
Dear Hassan:
As you already mentioned, brine samples need to be diluted at a compromise for the limit of detection of a given analyte(s). For example, if you go with a 100x dilution, then your measured solution will have 3g/L salinity (~0.3% Total dissolved solids). Although it is still fairly high and a bit harsh on the torch, nebulizer, etc., it may be at manageable levels for ICP-ES measurements. Then, you have to target the LODs for your analyte based on 100X and individual sensitivities. If you expect, concentration of analytes in the original brine to be 10-100ppm, the measured concentrations will be around 0.1 to 1 ppm which is realistic by ICP-ES for many analytes. As the solutions still have high salinity (0.3% TDS) which can introduce significant matrix effects, it is important that you prepare matrix-matched calibration standard.
However, if you wish to go to even lower limits than what you can get with the above direct dilution, then you may not have much choice except for resorting to some pre-concentration/matrix-removal chemistry. As the necessary chemistry can be quite different from one analyte to the other, it may need a number of pre-concentration strategies depending on the "trace elements" that you are interested.
Depending on how much effort you want to make, I would recommend:
1. Measure, the major ions using 1000X dilution (with minimal matrix effects)
2. Measure, high traces using 100X dilution, with matrix matched calibration.
3. If the LODs can not be met with the above, go for column chemistry according to the importance and targeted LODs of the "trace analytes"
Best wishes,
Nimal
Dear Nimal,
First of all, thank you very much for the detailed explanation.
Regarding your recommendations:
1. 10.000X dilution will be used for the major ions,
2. 100X dilution for the trace ions. And instead of 2% HNO3, 2% HCl will be used to match the calibration solutions salinity with my samples matrix.
Regards,
Hassan
Dear Hassan:
Glad to see that you have taken my comments and recommendations positively and found them useful.
When you do the measurement with 100X dilution for the traces, your solution will have 0.3% salt, which is still fairly high, and can introduce serious matrix effects (e.g. 20-30% signal suppression depending on the analyte). Using 2% HCl may not be a good way, as it can hardly match the matrix of 0.3% salt. Matrix effects arise due to scavenging of the plasma energy by the high levels of easily ionizable alkalis such as Na, K, Mg, etc.
To address this issue you can take one of the following two approaches:
1. Prepare calibration standards using a solution that contains approximately the same Na concentration as in 100X diluted brines, OR
2. Prepare calibration standards using one of the 100X diluted samples as the diluent for preparation of the standards. In that case, you will have to determine the sensitivity (slope) for calibration using the line similar to what you get in standard addition (as some analytes may be already present in the diluent solution).
Please feel free to contact me if you need further help or clarification.
Best wishes,
Nimal
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