High TDS Mining Samples: Custom CRMs for ICP-OES/MS

High total dissolved solids (TDS) matrices can cause signal suppression/enhancement, drift, and poor reproducibility in ICP-OES and ICP-MS. Matrix-matched standards reduce this bias by matching, as closely as possible, the chemistry of the standards to the chemistry of the samples. Custom CRMs help by locking in acids, dissolved solids, and element groupings under controlled, documented conditions.

What High TDS Does to ICP-OES and ICP-MS (and why it shows up as “bad data”)

Mining samples rarely arrive in a clean nitric acid matrix. After digestion or leaching, labs often end up with solutions that contain high acid and high TDS. Dilution is a common workaround, but it isn’t always possible, especially when you’re working near reporting limits.

When the matrix of your standards doesn’t match the matrix of your samples, the instrument is forced to compare apples to oranges. Even if analyte concentrations are similar, matrix differences can show up as:

Signal suppression or enhancement
Unexpected drift
Memory effects
Precipitation in complex chemistries

For ICP-OES, high TDS can still be manageable, but matrix mismatch can destabilize signals and complicate background correction.

For ICP-MS, matrix effects tend to be more punishing. Inconsistent chemistry can drive ionization suppression, increase oxide formation risk, and amplify long-term drift, especially across long mining runs.

Matrix Matching 101 , Match What the Instrument Sees (after dilution)

Matrix matching isn’t about perfection, it’s about minimizing bias.

The most important step happens before you ever grab a bottle of standard.. That means understanding what your samples look like after dilution, not what they looked like before digestion.

A common mistake is building a calibration curve based on instrument capability rather than sample reality. If your samples are routinely diluted 100× or 200×, your calibration should reflect those final concentrations.

As a practical starting point for ICP-OES, ICP-MS, and AA, a blank plus three to four standards is usually enough to see what’s really happening and confirm your curve behaves the way you expect.

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Stock CRMs vs Custom CRMs, where each fits in a high-TDS mining lab

Stock and custom CRMs aren’t an either-or decision. The best choice depends on the whether the analyte list changes often or remains the same, how aggressive your matrix is, and how much prep time (and risk) your lab can tolerate.

Stock single-element CRMs (flexibility + troubleshooting power)

Stock single-element CRMs are some of the most flexible tools a lab can have. They’re ideal when:

Your analyte list changes often
You need custom calibration curves (major + trace elements)
You want to avoid compatibility issues that can arise in large multi-element mixes

Best practice: use intermediate dilutions. Instead of pipetting from a 1,000 mg/mL stock straight down to low ppb working levels, create an intermediate (for example 10 ppm or 1 ppm) and work from there. This reduces pipetting error and improves reproducibility between analysts.

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Stock multi-element CRMs (efficiency + consistency)

Stock multi-element CRMs are all about efficiency. They tend to shine when:

Your analyte list remains the same
Your method is well established
The matrix is appropriate for your workflow

Using a multi-element stock CRM can reduce preparation time, minimize handling, and improve consistency across analysts, often a big win in high-throughput mining labs. Grouped standards can also be designed to help manage interferences and improve long-term stability.

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Where solution prep tends to go wrong (and why it looks like an instrument issue)

Many calibration problems aren’t instrument problems, they’re preparation problems. A few repeat offenders show up again and again:

Container compatibility: some matrices can leach metals from glass or interact with certain plastics
Adsorption: some elements (like Hg or precious metals) can stick to container walls at low concentrations
Precipitation: incompatible elements/chemistries can form solids, changing what your standard actually is
Dilution math errors: intermediate stocks, gravimetric prep, and proofing prevent avoidable rework

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Why Custom CRMs outperform in high-TDS mining matrices

When you’re dealing with complex matrices, unexplained bias, or unusual chemistries, custom CRMs can be the difference between “it should work” and “we can defend this result.”

Custom CRMs lock in matrix chemistry

Custom-built CRMs allow you to lock in the chemistry of your standards to match that of your samples, using the same acids, reagents, and dissolved solids concentration levels. This matters most when you’re near detection limits, where even small matrix differences can translate into measurable bias.

ICP-OES: where custom CRMs help most

When standards and samples share the same matrix, matrix-driven suppression and enhancement are minimized. For ICP-OES, this typically improves:

Signal stability
Background correction reliability
Day-to-day reproducibility in challenging mining matrices

ICP-MS: where custom CRMs help most

ICP-MS is more sensitive to matrix effects and interferences, so consistent chemistry and thoughtful element grouping are critical. Matrix-matched custom CRMs can help control:

Ionization suppression variability
Oxide formation behavior
Long-term drift across extended runs

Defensible accuracy + documentation

Custom CRMs produced under controlled conditions come with certified values, traceability, and uncertainty budgets, valuable during audits, method validation, and data reviews.

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Bottle size + stability strategy (reduce contamination risk, extend shelf life)

Custom standards also let labs dictate bottle size, which is an underrated lever for both cost control and risk reduction.

Bulk containers can be economical for high-use solutions (for example, internal standards that are tee’d into sample introduction systems).
Multiple smaller bottles (such as 125 mL) let labs keep unused standards sealed, extend usable shelf life, and limit the impact of a single contamination event.

If long-term stability is a priority, packaging strategy matters.

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The hybrid approach (best of both): Custom matrix base + stock spikes

Custom and stock CRMs don’t have to be an either-or decision. Many labs use a hybrid approach:

Use a custom CRM as the matrix foundation.
Spike stock single-element CRMs into that matrix to build calibration curves for analytes of interest.

This provides the matrix accuracy of a custom solution with the flexibility of stock single-element standards, so analytes can change without reordering an entirely new custom blend.

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Quick decision framework

Choose stock single-element CRMs when: flexibility matters, analytes change, and you want maximum troubleshooting control.
Choose stock multi-element CRMs when: your analyte list is stable and speed/consistency matters.
Choose custom CRMs when: you have high TDS or aggressive matrices, you’re near reporting limits, you need defensible accuracy, or analyst time is limited.
Choose a hybrid approach when: your matrix is consistent but your analyte list varies.

Checklist , Designing matrix-matched standards for high-TDS mining samples

Confirm the final post-dilution matrix (e.g. acid %, trace HCl, dissolved solids level).
Match standards to what the instrument sees (not just digestion chemistry).
Use intermediate dilutions to reduce pipetting error.
Choose containers that minimize contamination/leaching.
Watch for adsorption-prone analytes at low levels.
Avoid incompatible element combinations that can precipitate.
Proof dilution math: consider gravimetric prep where appropriate.
Document prep steps, labels, lot numbers, and storage conditions.

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Reduce high-TDS bias with a defensible, repeatable CRM strategy

High TDS matrices can make good instruments look inconsistent. The fix is rarely a single setting. I It is usually a strategy, where standards and samples match what your instrument actually sees.

If you’re seeing unexplained bias, drift, or poor reproducibility in mining workflows, matrix matching is the fastest path to more confident results. Custom CRMs make that approach repeatable, efficient, and defensible.

Next steps:

Explore custom standards: https://www.inorganicventures.com/icp-icp-ms-standards/custom-standards
Learn about services: https://www.inorganicventures.com/services

FAQs

What is matrix matching in ICP-OES and ICP-MS?

Matrix matching is designing standards so their chemistry matches the final diluted sample solution the instrument measures, reducing matrix-driven bias.

Why do high TDS matrices cause signal suppression and drift?

High dissolved solids and acid chemistry can change the nebulizer aerosol formation, transport efficiency, and plasma/ionization behavior, which shows up as suppression/enhancement and drift.

When should a mining lab choose custom CRMs over stock CRMs?

When matrices are aggressive or inconsistent, you’re working near reporting limits, you need audit-defensible accuracy, or prep time and variability are becoming a bottleneck.

How do intermediate dilutions reduce error when preparing low-level standards?

They reduce the size of the dilution step taken from very concentrated stocks, which lowers pipetting error and improves reproducibility.

How many calibration points are recommended for ICP-OES/ICP-MS?

A blank plus three to four standards is a solid starting point for many methods, then adjust based on linearity and reporting needs.

Can I use a custom CRM as a base and spike single-element standards into it?

Yes. A custom CRM can serve as the matrix foundation, then stock single-element CRMs can be spiked into that same matrix to build flexible calibration curves.

Related resources:

ICP periodic table guide: https://www.inorganicventures.com/new-icp-periodic-table-guide
Guides hub: https://www.inorganicventures.com/guides-and-papers2
Technical questions answered: https://www.inorganicventures.com/technical-questions-answered

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Conquering High Total Dissolved Solids (TDS) Matrices: How Custom Certified Reference Materials (CRMs) Improve ICP-OES and ICP-MS Performance in Mining Labs