Introduction: Why Raw Material Testing Is the Foundation of Pharmaceutical Quality
In pharmaceutical manufacturing, quality cannot be tested into a finished product — it must be built in from the start. The raw materials entering a manufacturing facility — active pharmaceutical ingredients (APIs), excipients, solvents, water for injection, packaging components, and reagents — collectively determine the safety, efficacy, and regulatory compliance of every drug product that leaves it. Raw material testing is the first and most critical gatekeeping function in the pharmaceutical supply chain.
The regulatory framework governing pharmaceutical raw material testing is among the most comprehensive in any industry, spanning ICH guidelines, USP/EP/JP compendial methods, FDA and EMA Good Manufacturing Practice (GMP) regulations, and — since 2018 — a major new layer of nitrosamine impurity control requirements that has reshaped supplier qualification practices worldwide. This guide covers the complete testing program: from identity verification and purity analysis through elemental impurities, residual solvents, nitrosamine screening, microbiology, and the supplier qualification framework that governs how these tests are organized and documented.
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The Regulatory Framework: ICH Guidelines and Compendial Standards
Pharmaceutical raw material testing is governed by a layered regulatory framework. At the international harmonization level, ICH (International Council for Harmonisation) guidelines provide the scientific and technical standards. At the compendial level, USP (United States Pharmacopeia), EP (European Pharmacopoeia), and JP (Japanese Pharmacopoeia) provide the specific test methods and acceptance criteria. National regulatory agencies (FDA, EMA, PMDA) enforce GMP compliance through inspections.
Key ICH guidelines for raw material testing:
- ICH Q7: Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients. Chapter 7 (Materials Management) provides the regulatory framework for raw material supplier qualification, incoming material testing, approved vendor lists, CoA review, and identity testing requirements.
- ICH Q3A/Q3B: Impurities in New Drug Substances and Products. Establishes reporting, identification, and qualification thresholds for organic impurities (0.05–0.1% for reporting; 0.10–0.15% for identification; 0.15–0.20% for qualification, depending on maximum daily dose).
- ICH Q3C: Residual Solvents. Classifies pharmaceutical solvents as Class 1 (to be avoided), Class 2 (limited), or Class 3 (limited by GMP), with Permitted Daily Exposures (PDEs) for each.
- ICH Q3D (R2): Elemental Impurities. Establishes PDEs for 24 elements by route of administration (oral, parenteral, inhalation, cutaneous/transcutaneous). Updated in 2023 to add gold, silver, nickel PDEs and cutaneous/transcutaneous route-specific limits.
- ICH M7 (R2): Assessment and Control of DNA Reactive (Mutagenic) Impurities. Establishes the Threshold of Toxicological Concern (TTC) for genotoxic impurities (generally 1.5 μg/day), classifies N-nitroso compounds as a cohort of concern with acceptable intakes in the ng/day range, and governs structural alert analysis and risk assessment.
- ICH Q11: Development and Manufacture of Drug Substances (Chemical Entities and Biotechnological/Biological Entities). Covers raw material selection, process understanding, and control strategy for drug substance manufacturing.
Key USP general chapters for raw material testing (mirrored in EP and JP counterparts):
- USP <1> — Injections and Implanted Drug Products: Particulate Matter
- USP <61>/<62> — Microbial Limit Tests (TAMC/TYMC) and Specified Microorganisms
- USP <71> — Sterility Tests
- USP <85> — Bacterial Endotoxins Test (LAL/BET)
- USP <197> — Spectrophotometric Identification Tests
- USP <232>/<233> — Elemental Impurities Limits and Procedures (ICP-MS)
- USP <467> — Residual Solvents (GC headspace)
- USP <643>/<645> — Total Organic Carbon and Conductivity (Pharmaceutical Water)
- USP <851> — Spectrophotometry and Light Scattering (Identification)
- USP <1469> — Nitrosamine Impurities (LC-MS/MS, GC-MS)
Supplier Qualification: The Framework for Raw Material Testing
Raw material testing does not occur in isolation — it is embedded in a supplier qualification framework required by ICH Q7 and GMP regulations. Before any raw material can be used in pharmaceutical manufacturing, its supplier must be qualified and placed on an Approved Supplier List (ASL).
The supplier qualification process involves:
- Supplier audit: On-site (or remote) audit of the supplier’s manufacturing facility, quality system, analytical capabilities, and documentation practices. ICH Q7 principles govern audit scope.
- Technical specification agreement: Formal specification for every raw material defining identity, purity, assay, impurity limits, microbial limits, physical properties, and any material-specific additional tests (e.g., particle size for inhalation APIs).
- Certificate of Analysis (CoA) review: Every shipment is accompanied by a supplier CoA; QC reviews the CoA against approved specifications before incoming testing proceeds.
- Incoming identity testing: ICH Q7 requires identity testing of every container of incoming API and every lot of excipients (or a statistically representative sample). Identity testing cannot be skipped based on supplier trust alone.
- Skip-lot testing: For fully qualified suppliers with an established track record, a risk-based reduced testing program (skip-lot) may be applied to full compendial testing — but identity testing of each container remains mandatory per ICH Q7.
- Ongoing surveillance: Re-qualification audits at defined intervals; review of any supplier changes (change notification); review of complaints and OOS results attributed to specific lots.
The 2018–2019 valsartan and sartan nitrosamine crisis was a direct consequence of supplier qualification failures: process changes at API manufacturers introduced nitrosamine-forming conditions that were not detected because the analytical methods in the original specifications did not include nitrosamine screening. This catalyzed a wholesale revision of how raw material specifications are developed and how supplier process changes are communicated and evaluated.
Pharmaceutical Raw Material Testing: Methods and Standards Quick Reference
| Test category | Primary method(s) | Regulatory standard(s) | Applies to | Key parameter |
| Identity | FTIR; NIR; NMR; Raman; UV-Vis; HPLC comparison to reference standard; TLC | USP <197>, <851>; ICH Q7 §7; compendial monograph identity tests | APIs, excipients, solvents, packaging — every container | Confirm material is what label states; detect substitution or misidentification |
| Assay / potency | HPLC (RP-HPLC, HILIC); UV-Vis spectrophotometry; titrimetry; GC | ICH Q6A; compendial monograph assay method; FDA Guidance on Analytical Procedures | APIs, reference standards | % purity / labeled strength; within-specification range for release |
| Organic impurities | HPLC with UV, PDA, or MS detection; GC-FID; GC-MS; LC-MS/MS | ICH Q3A/Q3B reporting (0.05–0.1%), identification (0.1–0.15%), qualification (0.15–0.2%) thresholds; compendial monograph | APIs, excipients, synthesis intermediates | Known and unknown related substances, degradation products, process impurities |
| Nitrosamine impurities | LC-MS/MS (primary); GC-MS; GC-TEA; HRMS (high-resolution MS for NDSRIs) | ICH M7 (R2); USP <1469>; FDA Guidance 2021; EMA CHMP Q&A | APIs, excipients (nitrite content), drug substances and products | NDMA, NDEA, NMBA, NDBA, and drug substance-related nitrosamines (NDSRIs) at ng/g or ng/mL sensitivity |
| Elemental impurities | ICP-MS (primary); ICP-OES; AAS | ICH Q3D (R2); USP <232>/<233>; EP 5.20; JP guidance | APIs, excipients, water, packaging in contact with product | 24 elements by route-specific PDE limits: Class 1 (As, Cd, Hg, Pb), Class 2A (Co, Ni, V), Class 2B, Class 3 |
| Residual solvents | GC with FID detection; headspace GC (static or dynamic); GC-MS for identification | ICH Q3C; USP <467>; EP 2.4.24 | APIs, excipients processed with organic solvents | Class 1 (avoid), Class 2 (PDE limits), Class 3 (limited by GMP); ppm-level quantification |
| Microbial limits (non-sterile) | Total Aerobic Microbial Count (TAMC) by membrane filtration or pour plate; Total Yeast/Mold Count (TYMC); specified pathogen absence by culture/PCR | USP <61>/<62>; EP 2.6.12/2.6.13; JP 4.05/4.06 | Non-sterile APIs, excipients, water (purified water) | Category-specific microbial limits; absence of Salmonella, E. coli, P. aeruginosa, S. aureus |
| Bacterial endotoxins (LAL/BET) | LAL gel-clot; turbidimetric; chromogenic; recombinant Factor C (rFC) assay | USP <85>; EP 2.6.14; ICH Q6A | APIs for parenteral products, WFI, excipients for injectables | EU per mL or per mg limits; endotoxin units (EU) — mandatory for parenteral route materials |
| Pharmaceutical water quality | TOC by oxidation/conductivity; conductivity (direct measurement); microbial testing | USP <643> (TOC), <645> (Conductivity), <1231>; EP 0169; FDA Water for Pharma Use guidance | Purified Water (PW), Water for Injection (WFI), Highly Purified Water (HPW) | TOC <500 ppb (PW) / <500 ppb (WFI); conductivity limits; microbial TAMC limits |
| Physical properties | Particle size (laser diffraction, dynamic light scattering, sieve analysis); polymorphism (XRPD, DSC); moisture (Karl Fischer); bulk/tap density; melting point | USP <429>, <786>, <776>; ICH Q6A; compendial monograph physical tests | APIs for solid dosage forms, inhalation products; all materials with critical physical specifications | Particle size distribution; polymorph form; moisture content; flow properties |
Nitrosamine Impurities: The Defining Pharmaceutical Safety Challenge Since 2018
The detection of N-nitrosodimethylamine (NDMA) in valsartan-containing APIs in 2018 triggered one of the most consequential pharmaceutical safety crises in decades. NDMA and related N-nitrosamines are potent genotoxic carcinogens classified by ICH M7 as a cohort of concern — their potential carcinogenicity at very low doses requires control to acceptable intake (AI) levels in the nanogram-per-day range, far below the 1.5 μg/day TTC that applies to most genotoxic impurities.
The crisis expanded rapidly: investigations revealed nitrosamine contamination across multiple API classes — sartans, ranitidine, metformin, nizatidine, and others — resulting in widespread global recalls and mandatory regulatory action. FDA issued its Guidance for Industry: Control of Nitrosamine Impurities in Human Drugs (2021, revised 2022). EMA published a detailed Q&A and step-by-step investigation procedure. USP published General Chapter <1469> (Nitrosamine Impurities) providing analytical methods and performance criteria for LC-MS/MS and GC-MS approaches.
Sources of nitrosamine contamination in raw materials
- Synthesis byproducts: N-nitrosamines can form when secondary or tertiary amines (common in API synthesis intermediates and excipients) come into contact with nitrosating agents (sodium nitrite, nitrogen oxides, nitrous acid) under acidic conditions. Dimethylformamide (DMF), N-methylpyrrolidone (NMP), and triethylamine are commonly used synthesis solvents that can contribute to nitrosamine formation.
- Storage and packaging: Nitrosamines can form post-synthesis during storage, particularly from nitrite-containing excipients or packaging materials in the presence of secondary amines from the API. Nitrite monitoring in excipients is now a standard part of excipient supplier qualification.
- Drug substance-related nitrosamines (NDSRIs): A newer category recognized from 2021 onward — nitrosamines that form from the API itself (or a closely related structure) acting as the amine precursor. NDSRIs often require HRMS (high-resolution mass spectrometry) for identification and characterization.
Analytical methods for nitrosamine testing
- LC-MS/MS (primary method): Liquid chromatography-tandem mass spectrometry provides ppb-level (parts per billion) sensitivity and specificity for simple nitrosamines (NDMA, NDEA, NDBA, NMBA, NDIPA, NEIPA). USP <1469> Procedure 3 uses LC-MS/MS with an Ascentis Express C18 column.
- GC-MS / GC-TEA: Gas chromatography with MS or thermal energy analyzer (TEA) detection — particularly useful for volatile nitrosamines. GC-TEA is nitrosamine-specific and requires no matrix cleanup for some sample types.
- HRMS (high-resolution mass spectrometry): Becoming essential for NDSRIs and unknown nitrosamine identification where a reference standard is not available. Orbitrap and Q-TOF instruments provide accurate mass and structural information.
For risk assessment, pharmaceutical manufacturers are required to conduct a three-step investigation per ICH M7 and EMA/FDA guidance: (1) identify potential nitrosamine sources from synthesis routes, reagents, solvents, excipients, and packaging; (2) calculate theoretical purge factors and acceptable limits; (3) confirm or rule out actual nitrosamine presence by analytical testing where risk is not negligible.
Elemental Impurities: ICH Q3D and USP <232>/<233>
Elemental impurities in pharmaceutical products can originate from intentional use of metals as process catalysts, from equipment and container-closure systems, from mined excipients (which may contain naturally occurring heavy metals), or from environmental contamination. Because elemental impurities have no beneficial effect on patients and may be harmful, ICH Q3D (now at Revision 2, 2023) establishes Permitted Daily Exposures (PDEs) by route of administration and element class.
Element classes under ICH Q3D (R2):
- Class 1 (all routes — highest risk): Arsenic (As), Cadmium (Cd), Mercury (Hg), Lead (Pb). Strict PDEs apply regardless of route; require risk assessment across all potential sources.
- Class 2A (route-dependent, high likelihood): Cobalt (Co), Nickel (Ni), Vanadium (V). High probability of occurrence; require assessment across all sources.
- Class 2B (route-dependent, lower likelihood): Silver, Gold, Iridium, Osmium, Palladium, Platinum, Rhodium, Ruthenium, Selenium, Thallium. Require assessment when intentionally added.
- Class 3 (limited by GMP — lowest risk): Lithium, Antimony, Barium, Molybdenum, Copper, Tin, Chromium, manganese, and others. Require assessment only if intentionally added.
USP <232> specifies the concentration limits in drug products for each element by route. USP <233> specifies the analytical procedures — primarily ICP-MS (inductively coupled plasma mass spectrometry), which simultaneously quantifies all 24 regulated elements at ppm-to-ppb sensitivity in a single analytical run. ICP-OES (optical emission spectroscopy) is an alternative for higher-concentration elements. The 2023 update to ICH Q3D (R2) added new PDEs for gold, silver, and nickel, and established limits for cutaneous and transcutaneous products — these were incorporated into USP in May 2024.
Residual Solvents: ICH Q3C and USP <467>
Residual solvents are organic volatile chemicals used in the synthesis of APIs or excipients that are not completely removed during manufacturing. ICH Q3C classifies them by toxicological risk:
- Class 1 solvents (to be avoided): Benzene, carbon tetrachloride, 1,2-dichloroethane, 1,1-dichloroethene, 1,1,1-trichloroethane. Known or suspected human carcinogens or environmental hazards. Use is prohibited unless justified and the residual level controlled to a concentration limit.
- Class 2 solvents (to be limited): Acetonitrile, chlorobenzene, chloroform, cyclohexane, DCM (dichloromethane), DMF, DMSO, ethylene glycol, hexane, methanol, N-methylpyrrolidone, pyridine, sulfolane, tetrahydrofuran, toluene, xylene. PDEs ranging from 8.8 mg/day (chloroform) to 8,500 mg/day (acetone) for oral route.
- Class 3 solvents (limited by GMP, 50 mg/day PDE): Acetic acid, acetone, anisole, 1-butanol, 2-butanol, butyl acetate, tert-butyl methyl ether, dimethylsulfoxide, ethanol, ethyl acetate, ethyl ether, ethyl formate, formic acid, heptane, isobutyl acetate, isopropyl acetate, methyl acetate, 3-methyl-1-butanol, methylethyl ketone, 2-methyl-1-propanol, propyl acetate.
The primary analytical method is headspace gas chromatography with flame ionization detection (GC-FID), using either static or dynamic headspace sampling per USP <467>. GC-MS provides confirmatory identification of unknown solvents. Method validation must demonstrate specificity, linearity, precision, accuracy, and limit of detection for each Class 1 and 2 solvent present in the synthetic route.
Identity Testing: The Mandatory First Test for Every Container
Identity testing is the highest-priority raw material test: ICH Q7 requires that every container of incoming API and a statistically representative sample of every excipient lot be tested for identity before use. Identity testing confirms that the material in the container is what the label states — preventing material mix-ups, substitution, and fraud.
Primary identity methods:
- FTIR (Fourier-Transform Infrared Spectroscopy): The workhorse identity method for most small-molecule APIs and excipients. FTIR generates a complete infrared spectrum that functions as a molecular fingerprint. Comparison against a reference spectrum (from a qualified reference standard) provides rapid, non-destructive confirmation. Most modern FTIR instruments support automated spectral comparison with pass/fail reporting against a library.
- NIR (Near-Infrared Spectroscopy): Increasingly used for at-line and in-line identity testing, particularly for manufacturing scale where testing through closed containers or packaging is required. Requires calibration against verified reference spectra but provides high throughput without sample preparation.
- Raman Spectroscopy: Complementary to FTIR; particularly useful for polymorphism differentiation and identity testing of aqueous solutions (where water’s IR absorption interferes). Handheld Raman instruments enable point-of-receipt identity verification.
- NMR (Nuclear Magnetic Resonance): Quantitative NMR (qNMR) provides both identity confirmation and purity/assay information in a single analysis. Increasingly used for complex molecules, biologics raw materials, and reference standard characterization.
- Compendial methods: USP monograph identity tests (UV-Vis, specific chemical reactions, melting point, optical rotation) remain required for materials with established pharmacopeial monographs.
Microbiology Testing: USP <61>, <62>, and <85>
Microbiological quality of pharmaceutical raw materials directly determines the microbiological quality of the drug product. Testing requirements depend on the material and its intended route of administration.
Microbial limits testing — USP <61>/<62>
Non-sterile raw materials (excipients, non-sterile APIs) are tested for Total Aerobic Microbial Count (TAMC) and Total Combined Yeast/Mold Count (TYMC) per USP <61>, and for the absence of specified microorganisms (Salmonella species, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, and Clostridium species depending on application) per USP <62>. Acceptance criteria are defined by the intended use — oral solid dosage forms have different TAMC limits than materials for topical or non-aqueous preparations. Rapid microbiology methods (PCR, automated growth detection, flow cytometry) are increasingly used to reduce turnaround time compared to classical 5-day incubation methods.
Bacterial endotoxin testing — USP <85>
Bacterial endotoxins (lipopolysaccharides from gram-negative bacteria) are pyrogens that cause severe febrile reactions in patients receiving parenteral products. Endotoxin testing by the Limulus Amebocyte Lysate (LAL) assay per USP <85> is mandatory for APIs, excipients, water for injection, and container-closure systems used in parenteral products. The three validated LAL methods are: gel-clot (qualitative/semi-quantitative), turbidimetric (kinetic or end-point), and chromogenic (kinetic or end-point). The recombinant Factor C (rFC) assay is a validated animal-free alternative now approved by USP and the EP as a pharmacopeial method, reducing ethical and supply concerns associated with horseshoe crab blood harvesting. See our companion article on sterility testing for related microbiology testing guidance.
Selecting Contract Laboratories for Pharmaceutical Raw Material Testing
Contract laboratory capabilities required for comprehensive pharmaceutical raw material testing span multiple instrument platforms and regulatory competencies. A laboratory conducting ICH Q3D elemental impurity testing must have ICP-MS with validated methods against USP <232>/<233>. A laboratory providing nitrosamine testing must have LC-MS/MS at sub-ng/mL sensitivity with validated methods for specific nitrosamines and FDA/EMA-compliant method performance criteria. A laboratory providing microbiology services must operate under cGMP with qualified cleanrooms or biological safety cabinets for specified microorganism testing.
Key accreditation and certification markers for pharmaceutical raw material testing laboratories: ISO/IEC 17025 for laboratory competence; FDA-registered and cGMP-compliant (21 CFR Part 211); DEA registration if testing controlled substances; USP/EP recognized methods; GLP certification for toxicological studies. Many specialized pharmaceutical contract labs additionally hold specific regulatory qualifications such as being listed in FDA’s Drug Establishment Registration database.
Additional resources: our guide to API manufacturing testing, our overview of sterility testing, potency testing for biopharmaceuticals, and USP standards.
Conclusion
Pharmaceutical raw material testing is a comprehensive, multi-disciplinary quality function that has grown substantially in scope and technical complexity since 2018. Identity testing under ICH Q7, impurity profiling under ICH Q3A/Q3B, residual solvent control under ICH Q3C, elemental impurity assessment under ICH Q3D, genotoxic impurity control under ICH M7, and — most critically for the current regulatory environment — nitrosamine risk assessment and analytical testing under ICH M7/USP <1469> all form mandatory components of a current-state raw material testing program. The supplier qualification framework under ICH Q7 provides the organizational structure within which these tests are planned, executed, and documented.
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Frequently Asked Questions About Pharmaceutical Raw Material Testing
ICH Q7 (Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients) establishes the regulatory framework for raw material testing in Chapter 7 (Materials Management). Key requirements include: maintaining a list of approved suppliers for each raw material; performing identity testing on every incoming container of API; conducting at least a visual inspection and identity test on excipient lots before use; reviewing supplier Certificates of Analysis (CoA) against approved material specifications before release; and establishing a qualification program that may include periodic supplier audits. ICH Q7 also addresses the handling of rejected materials, water quality requirements, and the conditions under which skip-lot testing of excipients may be applied. All testing must be documented in batch records traceable to individual material lots.
Nitrosamine impurities (N-nitroso compounds) are genotoxic carcinogens classified by ICH M7 as a ‘cohort of concern’ — they have acceptable daily intake (AI) limits in the nanogram-per-day range due to their high carcinogenic potency. The nitrosamine crisis began in 2018 when NDMA (N-nitrosodimethylamine) was detected in valsartan API from certain suppliers, triggering global recalls. Investigations revealed nitrosamine contamination across multiple drug classes (sartans, ranitidine, metformin). FDA issued mandatory guidance (2021) requiring all manufacturers to assess their products for nitrosamine risk. Testing is primarily by LC-MS/MS at ppb sensitivity, per USP <1469>. Excipient nitrite content testing has also become routine since nitrite-containing excipients can drive nitrosamine formation when combined with secondary amine APIs during storage.
ICH Q3D is the international harmonized guideline that establishes the science and policy for elemental impurity control — it defines which 24 elements to control, classifies them by risk (Classes 1, 2A, 2B, 3), and establishes Permitted Daily Exposures (PDEs) by route of administration. USP <232> is the compendial implementation of ICH Q3D’s limits in the United States Pharmacopeia — it specifies the concentration limits for each element in drug products. USP <233> specifies the analytical procedures (primarily ICP-MS) for measuring those elements. ICH Q3D (R2), the 2023 revision, added PDEs for gold, silver, and nickel and established cutaneous/transcutaneous limits; these were incorporated into USP in May 2024. The European Pharmacopoeia equivalent is Section 5.20 (Elemental Impurities) and related individual chapters.
ICH Q7 (Chapter 7.32) requires that each container of incoming API receive a 100% identity test before the material is released for use. This requirement exists because pharmaceutical supply chains are global and complex: the risk of material mix-up, mislabeling, counterfeiting, or substitution (intentional or accidental) cannot be eliminated by CoA review alone. Identity testing by FTIR, NIR, Raman, or compendial chemical methods provides rapid, independent confirmation that the material matches the label. Many high-profile pharmaceutical recalls have been traced to material mix-ups that occurred at the supplier or during transport. Excipient lots require identity testing of a statistically representative number of containers per lot, though 100% testing is best practice for high-risk materials.
The Limulus Amebocyte Lysate (LAL) test, formally called the Bacterial Endotoxins Test (BET) per USP <85>, detects and quantifies bacterial endotoxins — lipopolysaccharides from the outer membrane of gram-negative bacteria. Endotoxins are potent pyrogens (fever-causing agents) that can cause severe systemic reactions in patients receiving parenteral products, even at very low concentrations. LAL testing is mandatory for APIs, excipients, container-closure components, and water for injection (WFI) that will be used in the manufacture of parenteral (injectable) dosage forms. The three validated LAL methods are gel-clot, turbidimetric, and chromogenic. The recombinant Factor C (rFC) assay is an animal-free alternative, now validated and recognized as a pharmacopeial method by USP and EP, offering an ethical alternative to the traditional horseshoe crab blood-derived reagent.
Residual solvent testing per ICH Q3C and USP <467> is required for APIs and excipients synthesized or processed using organic solvents. Testing identifies and quantifies residual solvents against class-specific limits: Class 1 solvents (known carcinogens such as benzene) must be avoided and if present at all must be controlled to strict concentration limits; Class 2 solvents (including methanol, acetonitrile, DMF, toluene) have specific PDE-based limits by route of administration; Class 3 solvents (including ethanol, acetone, ethyl acetate) are limited by GMP to ≤50 mg/day. The analytical method is gas chromatography with headspace sampling (static or dynamic) and FID detection per USP <467>. All solvents used in synthesis or purification must be identified, and any Class 1 or 2 solvent present must be tested with validated methods demonstrating specificity to that solvent.
Pharmaceutical water (Purified Water and Water for Injection) is itself a regulated raw material with specific quality requirements. Testing per USP <643> (Total Organic Carbon), <645> (Conductivity), and <1231> (Water for Pharmaceutical Purposes guidance) is performed on samples collected from the water system at defined points and frequencies. TOC testing measures organic contamination with a limit of <500 ppb for both Purified Water and WFI. Conductivity is measured in real time or periodically with temperature-dependent limits. Microbial quality of Purified Water is tested by Total Aerobic Microbial Count (TAMC) with an alert limit of 100 CFU/mL (action limit varies by use). WFI has a TAMC action limit of 10 CFU/100 mL. Endotoxin testing of WFI is performed with a limit of 0.25 EU/mL. Pharmaceutical water systems (reverse osmosis, deionization, distillation, ultrafiltration) are monitored continuously or at validated sampling frequencies under a water monitoring program.
ICP-MS (Inductively Coupled Plasma Mass Spectrometry) is the primary method specified by USP <233> and ICH Q3D for elemental impurity quantification in pharmaceutical materials. ICP-MS simultaneously measures up to 24 regulated elements at detection limits in the ppb-to-ppt range in a single analytical run — making it highly efficient for the comprehensive elemental profiling required by ICH Q3D. The sample is digested (acid digestion or microwave digestion) or dissolved and introduced into the instrument as a liquid. ICP-OES (Optical Emission Spectroscopy) is an alternative for elements at higher concentrations where its lower sensitivity is acceptable. Atomic Absorption Spectroscopy (AAS) — the older conventional method — is being phased out in favor of ICP-MS for most pharmaceutical applications. Method validation per USP <1225> must demonstrate specificity, linearity, range, accuracy, precision, and limits of detection and quantitation for each element.