Pharmaceutical Elemental Analysis

Pharmaceutical Heavy Metals Testing

A Brief History: Why This Testing Looks Completely Different Than It Did a Decade Ago

Understanding where current pharmaceutical heavy metals testing came from helps explain why it’s structured the way it is today, and why “heavy metals testing” as a phrase can mean something quite different depending on which era of pharmacopeial standard you’re referencing.

For roughly a century, pharmaceutical heavy metals were screened using a method described in USP General Chapter <231> — a colorimetric sulfide precipitation test dating back to the early 1900s. This method had real, well-documented limitations: it was non-specific (it couldn’t distinguish which metal was actually present, only that something in a broad “heavy metals” category exceeded a threshold), insensitive, and poorly reproducible. Critically, it sometimes failed to detect mercury even at levels above its own stated limit — a genuinely serious gap for a test meant to protect patient safety.

Beginning in the 1990s, USP undertook a multi-year revision process that culminated in two new general chapters, USP <232> (Elemental Impurities — Limits) and USP <233> (Elemental Impurities — Procedures), developed in close alignment with the ICH Q3D guideline. These replaced General Chapter <231> entirely, becoming applicable to all USP-monographed drug products effective January 1, 2018, with ICH Q3D itself implemented for new drug products starting in 2016. This wasn’t a minor methodology update — it represented a fundamental shift from a single non-specific pass/fail test to element-specific, risk-based control built on toxicologically derived limits for each individual element, evaluated by route of administration.

The practical upshot for anyone submitting a sample for “heavy metals testing” today: the test you actually need is almost certainly not the old USP <231> sulfide precipitation method (now obsolete and removed from current USP), but rather a quantitative, element-specific ICP-OES or ICP-MS panel scoped to USP <232>/<233> and ICH Q3D limits.

The Four-Class System: Why Not Every Element Gets the Same Scrutiny

Class 1 covers arsenic, cadmium, mercury, and lead: human toxicants with no acceptable use in pharmaceutical manufacturing, requiring careful consideration across essentially every route of administration regardless of whether they're plausibly present in a given product.
Class 2A covers cobalt, nickel, and vanadium: elements with a relatively high probability of occurrence in drug products (often from manufacturing equipment, catalysts, or raw materials) combined with meaningful toxicity, generally requiring risk assessment for most products.
Class 2B covers platinum group metals (platinum, palladium, iridium, osmium, rhodium, ruthenium) along with silver, gold, and a few others: elements with low probability of occurrence (since they're not commonly present unless deliberately used, typically as catalysts) but meaningful toxicity when they are present — this is the class our Residual Palladium and Residual Platinum/Rhodium/Ruthenium services address specifically.
Class 3 covers elements with relatively low oral toxicity (such as barium, lithium, and others) that may still warrant consideration for parenteral or inhalation products specifically, where the risk profile shifts.

This classification is the actual logic behind why a thoughtful elemental impurity testing program doesn’t test every possible element on every sample — it tests according to a documented risk assessment that considers your specific synthesis route, raw materials, and manufacturing process, with Class 1 elements warranting attention essentially always and other classes scoped according to actual likelihood of occurrence in your specific product.

Matrix & Digestion

Pharmaceutical heavy metals testing spans an unusually wide range of sample types — APIs, excipients, finished oral solid dosage forms, parenteral solutions, and raw materials — each requiring digestion conditions suited to its specific composition.

Our approach:

Microwave-assisted closed-vessel acid digestion designed to fully break down organic API and excipient matrices
Method selection accounting for the specific elements being targeted, since required sensitivity varies enormously by element and route of administration
Recovery conditions appropriate to each Class 1 element's chemical behavior, since arsenic, cadmium, mercury, and lead each present distinct digestion and recovery considerations
Specific attention to mercury, given its documented history as the element most likely to be under-detected by inadequate methodology — exactly the failure mode that drove the replacement of USP in the first place

Detection Limits and Method Selection: ICP-OES vs. ICP-MS

This is where being honest about method fit matters most, because the right technique genuinely depends on which limit you’re trying to meet, and getting this wrong either wastes money on unnecessary sensitivity or — more seriously — produces a result that doesn’t actually demonstrate compliance.

USP <233> doesn’t mandate a specific instrument, but generally suggests ICP-OES or atomic absorption for parts-per-million-level work, with ICP-MS as the method of choice when sub-ppm or sub-ppb sensitivity is required. To make this concrete: the parenteral PDE for mercury is 0.3 micrograms per gram (at a 10 gram per day maximum dose), which works out to a limit of roughly 0.03 ppm — a concentration level that’s genuinely difficult or impossible for ICP-OES to reliably quantify, and squarely in ICP-MS territory. Many other Class 1 and Class 2B parenteral and inhalation limits sit in similarly demanding ranges.

This means a single “heavy metals testing” service can’t responsibly promise one universal detection capability across every element and every route of administration. We scope method selection — ICP-OES where its sensitivity genuinely covers your specification, ICP-MS where it doesn’t — based on your specific elements of concern and intended route of administration, rather than defaulting to whichever method happens to be more convenient or assuming one technique fits every case.

What We Test For

Class 1 : Arsenic (As), Cadmium (Cd), Mercury (Hg), Lead (Pb). Always considered; tightest scrutiny across all routes
Class 2A : Cobalt (Co), Nickel (Ni), Vanadium (V). High probability of occurrence; generally requires risk assessment
Class 2B : Platinum (Pt), Palladium (Pd), Iridium (Ir), Osmium (Os), Rhodium (Rh), Ruthenium (Ru), Silver (Ag), Gold (Au). Low probability unless deliberately used (e.g., as catalysts); see our dedicated residual catalyst metal pages for these.
Class 3 : Lithium (Li), Antimony (Sb), Barium (Ba), and others. Route-dependent; oral risk generally low, parenteral/inhalation may warrant inclusion

Panel scope is determined by risk assessment specific to your product — raw material sourcing, synthesis route, manufacturing equipment, water source, and container closure system all factor into which elements are realistically plausible contaminants for your specific drug product.

Building a Risk-Based Testing Program, Not Just Running a Panel

The core philosophy behind ICH Q3D and USP <232> is risk-based, not blanket testing — and this matters practically because over-testing wastes resources while under-testing fails compliance, and the right answer requires genuine process knowledge rather than a one-size-fits-all panel.

A complete risk assessment typically considers:

Raw material sourcing — mined or naturally derived materials (certain excipients, for example) inherently carry some baseline trace element content tied to their geological origin
Manufacturing equipment — stainless steel processing equipment is a recognized potential source of nickel, chromium, and molybdenum
Water used in manufacturing — a potential source depending on water source and treatment
Container closure systems — packaging materials can introduce certain elements, particularly relevant for parenteral products in prolonged contact with their container
Intentionally added elements — catalysts used in synthesis, which is where Class 2B platinum group metal testing typically becomes most directly relevant

This is why we work with clients to scope testing appropriately rather than defaulting to “test for all 24 ICH Q3D elements on every sample” — a thorough risk assessment, informed by accurate process knowledge, is both more defensible from a regulatory standpoint and more cost-effective than indiscriminate testing.

Compliance Options: Drug Product vs. Component Testing

ICH Q3D and USP <232> offer more than one path to demonstrating compliance, which is worth understanding since it affects how and where testing fits into your overall control strategy.

The Drug Product Analysis Option involves testing a representative sample of the finished, typical dosage unit, scaling the measured concentration against maximum daily dose to compare against the PDE — generally the most broadly applicable and well-accepted approach. Alternative approaches, including a Summation Option (combining known or measured levels from individual components) and an Individual Component Approach for large-volume parenterals, are also available depending on your specific situation and what level of testing burden makes sense for your control strategy.

Understanding which compliance option fits your situation — and which specific samples therefore need testing, whether that’s drug substance, individual excipients, or finished drug product — is part of the conversation we have with clients scoping a testing program, rather than assuming finished product testing is automatically the right (or only) answer.

Who Uses This Service

Regulatory affairs and CMC teams building and documenting risk assessments for new drug applications, where defensible analytical data supports the overall elemental impurities control strategy required for submission.
Quality control teams at manufacturing sites establishing routine release testing for elements identified as relevant through risk assessment, distinguishing between elements that warrant every-batch testing and those adequately controlled through other means.
Process development teams evaluating raw material, excipient, or equipment sourcing decisions where trace element content is a relevant consideration, using analytical data to compare options before committing to a supply chain.
Generic drug manufacturers conducting elemental impurity risk assessments and confirmatory testing as part of ANDA submissions, where demonstrating Q3D compliance is a standard expectation.
Contract manufacturers and CDMOs supporting client risk assessments and providing analytical documentation across multiple drug products and routes of administration.

Sample Quantity & Handling

Required sample size: 0.5–2 grams for solid dosage forms, intermediates, or raw materials, or appropriate volume for liquid/parenteral samples depending on required sensitivity.

Packaging guidelines:

Use clean, sealed containers appropriate to sample type, avoiding glass for samples requiring very low reporting limits given the risk of trace element leaching from glass itself
Provide product type, route of administration, and maximum daily dose where known, since these directly determine the applicable PDE and therefore the required reporting limit
Indicate which elements are of specific concern based on your own risk assessment, where available, to help scope the appropriate analytical approach

Turnaround Time & Pricing

Standard turnaround: 3–5 business days Rush service: 24–48 hours available

Pricing starts from $150 per sample for ICP-OES-based panels, with ICP-MS-based ultra-trace panels priced according to element scope and required sensitivity.

What You Receive

Clients receive a Certificate of Analysis suitable for regulatory documentation, risk assessment support, and routine release testing.

Your COA includes:

Individual elemental results (ppm or ppb depending on method) for each tested element
Comparison context against applicable PDE limits where dose and route information is provided
Method references (ICP-OES or ICP-MS) and digestion notes
Reporting limits and analytical qualifiers
Batch-level quality control summary

All results are supported by CRM-traceable calibration, with duplicates and matrix spikes performed on each analytical batch — essential given how directly these results can feed into regulatory submissions and release decisions.

Methods & Standards

Sterling Analytical applies methods aligned with current pharmaceutical elemental impurity standards:

USP Elemental Impurities — Procedures, as the harmonized analytical methodology referenced by USP and ICH Q3D
ICP-OES for parts-per-million-level analysis
ICP-MS for sub-ppm and ultra-trace requirements, particularly relevant for parenteral and inhalation product specifications
Calibration using certified reference materials (CRMs) appropriate to pharmaceutical elemental impurity testing

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Request a Quote

Submit your product type, route of administration, and any known risk assessment findings to receive a tailored quote and recommended testing scope.

Frequently Asked Questions

What is pharmaceutical heavy metals testing under USP <232>/<233>?

It's quantitative, element-specific testing for toxicologically significant elements in pharmaceutical products, replacing the older non-specific USP <231> sulfide precipitation method. Testing is structured around ICH Q3D's risk-based, four-class elemental impurity framework.

Is USP <231> still used for heavy metals testing?

No. USP <231> was removed and replaced by USP <232> (limits) and <233> (procedures), effective January 1, 2018, in alignment with ICH Q3D. Current pharmaceutical heavy metals testing is element-specific and quantitative, not the older non-specific colorimetric method.

Do I need to test for all 24 ICH Q3D elements on every product?

No. ICH Q3D and USP <232> are built around risk assessment, not blanket testing. Class 1 elements (arsenic, cadmium, mercury, lead) generally warrant consideration across most products, while other classes are scoped according to actual likelihood of occurrence based on your raw materials, synthesis route, equipment, and packaging.

When is ICP-MS required instead of ICP-OES?

When required reporting limits fall below what ICP-OES can reliably quantify, generally for parenteral or inhalation products with the tightest PDE limits. As an example, the parenteral PDE for mercury works out to roughly 0.03 ppm at typical dosing, a level usually requiring ICP-MS.

What's the difference between Class 2A and Class 2B elements?

Class 2A elements (cobalt, nickel, vanadium) have relatively high probability of occurrence, often from manufacturing equipment, and generally require risk assessment. Class 2B elements (platinum group metals, silver, gold) have lower probability of occurrence since they're typically only present if deliberately used, such as catalysts in synthesis.

Can you test finished drug product, not just API or raw materials?

Yes. We can test active pharmaceutical ingredients, excipients, raw materials, and finished drug products, supporting whichever compliance option (drug product analysis, summation, or individual component approach) fits your control strategy.

How much sample do you need?

Typically 0.5–2 grams for solid materials, with appropriate volume for liquid or parenteral samples depending on required sensitivity.

How long does testing take?

Standard turnaround is 3–5 business days, with 24–48 hour rush service available.

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customerservice@sterlinganalytical.com

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