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Residual Platinum, Rhodium & Ruthenium Testing
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Sterling Analytical provides residual platinum, rhodium, and ruthenium testing in active pharmaceutical ingredients, intermediates, and reaction products by ICP-OES. These three platinum group metals (PGMs) are used across a range of pharmaceutical synthesis chemistry — platinum primarily in hydrogenation, rhodium and ruthenium frequently in chiral and asymmetric hydrogenation catalysis, and ruthenium additionally in olefin metathesis — and like palladium, residual amounts following synthesis need to be monitored to confirm catalyst removal and support consistent product quality.
Platinum, rhodium, and ruthenium sit alongside palladium as members of the platinum metals group, sharing enough chemical similarity that they’re often discussed together in both synthetic chemistry and regulatory contexts — but they aren’t interchangeable from a testing or risk-assessment standpoint, and treating them as a single generic “PGM panel” without understanding the real differences between them misses some genuinely important context.
A Regulatory Detail Worth Understanding: Why Rhodium and Ruthenium Are Tested Against Palladium's Limit
This is a specific, somewhat surprising regulatory fact that’s directly relevant to how rhodium and ruthenium testing is actually interpreted, and it’s worth explaining clearly rather than glossing over.
Under ICH Q3D, the global framework governing elemental impurities in pharmaceuticals, there isn’t enough independent toxicological data to establish a dedicated Permitted Daily Exposure (PDE) for iridium, osmium, rhodium, or ruthenium. Rather than leaving these elements unregulated, ICH Q3D explicitly applies palladium’s PDE to all four, based on their chemical similarity to palladium as platinum group metals. Platinum does have its own independently established PDE, set at the same numerical level as palladium’s. In practical terms, this means rhodium and ruthenium results are evaluated against the palladium limit, not a rhodium- or ruthenium-specific one — a detail that matters when setting internal specifications or interpreting a result, since there’s no separate published rhodium or ruthenium number to test against.
This shared-limit framework is also why testing these elements together, with shared method development and a consistent reporting approach, makes practical sense — the regulatory logic already treats them as a connected group, even though the underlying chemistry of how each metal behaves during digestion and recovery is genuinely distinct.
This regulatory landscape predates ICH Q3D, too, and it’s worth knowing the history briefly: European regulators specifically addressed metal catalyst residues in pharmaceuticals years before ICH Q3D’s global harmonization, through European Medicines Agency guidance establishing limits for residues of metal catalysts in drug products. That earlier regulatory attention is part of why metal scavenging and residual metal control became standard pharmaceutical industry practice well before ICH Q3D formalized the current 24-element, four-class international framework — the underlying concern (and the purification technology developed to address it) is not a recent development.
From High Result to Low Result: What Purification Actually Looks Like for These Three Metals
As with palladium, it’s worth understanding the practical purification context this testing exists to evaluate, because a number on a certificate of analysis only means something once you understand what process produced it.
Reaction mixtures from platinum, rhodium, or ruthenium-catalyzed synthesis don’t start out clean. A real, published example involving rhodium-catalyzed hydroformylation illustrates the kind of purification step residual metal testing is designed to track: an untreated reaction mixture containing 1.94 ppm rhodium, passed once through an activated carbon bed, came out the other side at 0.21 ppm — an 89.2% reduction in a single pass. This is a comparatively modest starting concentration relative to some palladium-catalyzed coupling reactions (which can start in the hundreds or low thousands of ppm), but it illustrates the same underlying principle: purification technology exists specifically to bridge the gap between “what a reaction mixture contains right after the reaction” and “what a finished API needs to contain,” and residual metal testing is how that bridge gets verified rather than assumed.
Three general strategies are used to manage residual platinum group metals across pharmaceutical and fine chemical synthesis: classical purification techniques (crystallization, extraction, chromatography), specially designed “self-scavenging” catalysts engineered to be easily removable after the reaction completes, and dedicated metal scavengers — materials that bind metal contaminants and are then physically removed, similar to the thiol- and thiourea-functionalized scavengers discussed in more detail on our Residual Palladium in API Testing page. Activated carbon, in particular, has a long, well-documented history as a scavenging medium across the platinum group broadly, including documented selectivity differences between metals — activated carbon has been shown in some contexts to selectively adsorb palladium before either rhodium or another platinum group element, a useful property when a process needs to separate one metal from another rather than just removing all metals indiscriminately.
Matrix & Digestion
Platinum, rhodium, and ruthenium each present somewhat different digestion behavior, which is part of why testing all three together requires a method genuinely validated across all of them rather than assuming one approach works equally well for all platinum group metals.
Our approach:
- Microwave-assisted closed-vessel digestion designed to fully break down organic API matrices while recovering each metal across its possible chemical forms
- Acid digestion conditions selected with attention to ruthenium specifically, which can form volatile compounds under certain oxidizing conditions and requires digestion chemistry that avoids losing the analyte before it ever reaches the instrument — a consideration that doesn't apply the same way to platinum or rhodium
- Recovery conditions accounting for metal that may be present as soluble species, nanoparticulate metal, or material bound to the API or to scavenger reagents used during purification, consistent with how residual metal more generally behaves in pharmaceutical matrices
- Calibration using platinum, rhodium, and ruthenium reference standards specifically, rather than assuming a single multi-element calibration approach performs equally well across chemically distinct elements
Incomplete digestion — particularly of particulate or strongly bound metal, or loss of ruthenium to volatilization — is a recognized source of underreporting, which is why digestion conditions are selected deliberately for this specific element combination rather than applied generically.
Detection Limits and Method Fit
ICP-OES provides reliable quantification of platinum, rhodium, and ruthenium in the low ppm range, suitable for most development and process control applications.
Typical capability:
- Reporting limits: approximately 0.1–1 ppm per element, depending on sample matrix and preparation
- Working range: low ppm through higher concentrations
As with residual palladium testing, method suitability depends on what specification you’re actually working against:
- Well-suited for process monitoring, development work, and catalyst removal verification where required limits sit at low ppm or higher
- For tighter specifications, particularly given that rhodium and ruthenium are evaluated against palladium's PDE (which, as covered on our Residual Palladium in API Testing page, can drop as low as roughly 1 ppm for inhaled products at typical dosing), achievable reporting limits should be confirmed in advance based on your matrix and required sensitivity
- Parenteral or inhaled products with ultra-trace requirements may need more sensitive techniques than ICP-OES can reliably provide
Why Rhodium and Ruthenium Specifically Matter in Chiral Synthesis
Platinum’s role in pharmaceutical synthesis is comparatively familiar — primarily hydrogenation, similar in spirit to palladium’s use. Rhodium and ruthenium deserve a bit more specific context, because their role is often tied to a particular kind of chemistry with particular stakes.
Rhodium and ruthenium catalysts are frequently used in chiral and asymmetric hydrogenation — chemistry associated with Nobel Prize-recognized advances in the field — where the catalyst doesn’t just add hydrogen across a double bond but does so selectively to produce one enantiomer preferentially over its mirror image. This is often essential for producing a single-enantiomer API rather than a racemic mixture, since the two mirror-image forms of a chiral drug molecule can have meaningfully different biological activity, and in some documented cases, one enantiomer provides the desired therapeutic effect while the other contributes only side effects or no benefit at all. Ruthenium also plays a distinct additional role in olefin metathesis chemistry — a powerful carbon-carbon bond-forming reaction used in certain specialized synthetic routes, separate from its hydrogenation applications.
This is genuinely specialized, often expensive catalysis: rhodium and ruthenium catalysts are relatively costly, and production yields per gram of catalyst metal are a real economic consideration in process design, which is part of why catalyst recovery and recycling are often built into a process alongside residual metal monitoring — the two considerations (cost recovery and regulatory compliance) point toward the same underlying need for accurate metal quantification at multiple points in a process.
API Matrices Supported
We analyze a range of pharmaceutical materials:
- Active pharmaceutical ingredients (APIs)
- Synthetic intermediates
- Crude and purified reaction products
- Process development and scale-up samples
Sample preparation is adapted to matrix composition and solubility, with particular attention to which of the three metals (or which combination) is relevant to your specific synthesis route.
Applications
Residual platinum, rhodium, and ruthenium testing is used for:
- Catalyst removal monitoring during process development, particularly for chiral hydrogenation and metathesis routes
- Evaluation and comparison of purification or catalyst recovery strategies, including scavenger and activated carbon performance
- Batch comparison and consistency checks across a production campaign
- Investigation of unexpectedly elevated metal levels
- In-process quality control during scale-up and manufacturing
Who Uses This Service
- Process chemists and development teams working with hydrogenation, asymmetric hydrogenation, or metathesis routes, monitoring catalyst removal effectiveness across purification and crystallization steps.
- Manufacturing and scale-up teams maintaining batch-to-batch consistency in catalyst clearance as a process moves from lab to pilot to commercial scale, where late-introduced impurities carry a higher risk of being carried through to final product than those removed earlier in synthesis.
- Quality control teams establishing internal specifications for platinum, rhodium, or ruthenium content and identifying deviations across a production campaign.
- Regulatory and CMC teams building risk assessments and control strategies under ICH Q3D, where understanding the shared palladium-based PDE for rhodium and ruthenium is directly relevant to specification-setting.
- Catalyst recovery and recycling operations verifying residual metal levels in recovered process streams, where accurate quantification supports both cost recovery and confirming downstream material is clean enough for reuse or sale.
Sampling and Mass Requirements
Sample mass directly affects achievable reporting limits across all three elements.
General guidance:
- Preferred: 0.5–1 gram for low-level multi-element analysis
- Minimum: approximately 0.1 gram, though this may limit achievable reporting sensitivity, particularly when testing for all three elements from a single limited sample
- Indicate which specific metal or combination is expected, and your expected concentration range if known, since this helps scope the appropriate approach
Where sample material is limited and multiple elements need to be tested from the same submission, we can advise on realistic achievable reporting limits before testing begins.
Turnaround Time
Standard turnaround: 3–5 business days Expedited service: 24–48 hours available
Results and Reporting
Reports are structured for technical and process-focused use and include:
- Platinum, rhodium, and ruthenium concentrations (ppm), individually reported
- Reporting limits and method context for each element
- Digestion and preparation summary
- Quality control data (blanks, spikes, duplicates)
Related Services
Explore related services:
- Residual Palladium In API Testin
- Pharmaceutical Heavy Metals Testing
- Platinum Reforming Catalyst Testing
- Precious Metal Assay Lab
- USP Salt Analysis (NaCl, KCl)
Request a Quote
Submit your sample details, synthesis route information, and required reporting limits to receive a tailored quote and method recommendation.
Frequently Asked Questions
It's used to measure platinum group metals remaining in an API or intermediate following PGM-catalyzed synthesis, particularly hydrogenation, chiral/asymmetric hydrogenation, and metathesis, supporting catalyst removal monitoring and process consistency.
Under ICH Q3D, there isn't sufficient independent toxicological data to establish dedicated Permitted Daily Exposure limits for rhodium, ruthenium, iridium, or osmium. The guideline applies palladium's PDE to all four based on their chemical similarity, while platinum has its own independently established PDE at the same level as palladium's.
This varies by reaction, but a documented hydroformylation example showed a reaction mixture starting at 1.94 ppm rhodium reduced to 0.21 ppm after a single pass through activated carbon, an 89% reduction. Starting concentrations and achievable reduction depend heavily on the specific catalyst system and reaction.
Three general approaches are used: classical purification (crystallization, extraction, chromatography), self-scavenging catalysts designed for easy removal, and dedicated metal scavengers that bind contaminant metal for physical removal. Activated carbon has documented selectivity differences between platinum group metals in some contexts.
Ruthenium can form volatile compounds under certain oxidizing conditions, which can result in analyte loss before measurement if digestion conditions aren't specifically selected to avoid it. This is a consideration unique to ruthenium among the three elements.
Rhodium and ruthenium catalysts are frequently used in asymmetric hydrogenation, where selective addition of hydrogen produces one enantiomer preferentially, often essential for single-enantiomer API production rather than a racemic mixture, since the two enantiomers of a chiral drug can have meaningfully different biological activity.
Yes. Impurities introduced later in a synthesis route generally carry a higher risk of being carried through to the final product than those introduced earlier, since there are fewer subsequent purification steps available to remove them.
Typical reporting limits are approximately 0.1–1 ppm per element, depending on sample matrix and preparation, similar to residual palladium testing.
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