How pharma proves centrifuges and filters are truly clean — and regulators are watching

Cross-contamination isn’t a theoretical risk in multi-product drug plants; it’s a GMP red line. Cleaning activities on stainless equipment are “critical” to prevent carryover of potent APIs (active pharmaceutical ingredients) on shared centrifuges and filtration trains, according to industry literature (pmc.ncbi.nlm.nih.gov).

Regulatory expectations are harmonized. Indonesia’s GMP (CPOB) explicitly aligns with PIC/S (Pharmaceutical Inspection Co‑operation Scheme) and WHO guidance, and the latest CPOB (BPOM Reg. 34/2018) is based on PIC/S GMP doc. PE009‑16 (2022) (klikcpob.pom.go.id). That means cleaning procedures for centrifuges and filter skids must be developed, validated, and verified “drug‑free” with science — not faith.

Modern Clean‑in‑Place (CIP; automated spray/recirculation cleaning) has been a game‑changer since the 1950s, delivering improved compliance, reduced downtime, lower water/detergent consumption, and less manual labor than old-school manual washdowns (www.tsaprocessequipments.com). In one validated case, the conductivity of the final rinse matched purified water — a strong signal that detergents were fully removed (www.pharmtech.com).

CIP and COP: definitions and trade‑offs

CIP (Clean‑in‑Place) cleans equipment in situ using fixed spray balls/nozzles and pumped recirculation without disassembly; it’s ideal for large, enclosed systems like centrifuge bowls, piping, and filter skids, delivering reproducibility and lower labor. COP (Clean‑out‑of‑Place) disassembles components for manual or assisted cleaning (immersion, brushing, ultrasonics). COP reaches complex geometries but adds handling and variability. Many plants run a hybrid: CIP for vessels/loops and COP for sensitive removable parts (e.g., membranes, seals) when needed (www.pharmtech.com).

On filtration skids designed for pharma, sanitary housings matter; high‑pressure sanitary assemblies such as 316L stainless cartridge housings are built for CIP compatibility and documented cleanability in validation.

The GMP context is clear. CPOB’s PIC/S‑aligned framework pulls from risk‑based ICH principles (e.g., ICH Q7A/Q9) and EMA/ICH guidance, and regulators emphasize design for cleanability, documented procedures, and scientifically justified residue limits — increasingly based on health‑based ADE/PDE (acceptable/permitted daily exposure) rather than arbitrary numbers (klikcpob.pom.go.id) (www.pharmtech.com) (www.pharmtech.com).

Risk‑based procedure development

Validation starts with a risk/flow assessment: API potency, solubility, and toxicity; equipment geometry like dead‑legs, seals, joints; and exposure points. Centrifuge OEMs advise pre‑commissioning risk analyses with users, including riboflavin (a fluorescent tracer) spray coverage tests to reveal shadowed areas (process-technology-online.com).

Design helps. One “VBC” centrifuge uses an inclined basket with integral self‑cleaning spray nozzles and hygienic seals, enabling rinsing, spraying, scraping, suction, and even steam flushing to reach internal surfaces (process-technology-online.com) (process-technology-online.com). Good practice configures spray ball placement, recirculation loops, fast‑drain features, and minimal dead‑legs.

For COP, disassembly targets parts like seals or filter elements. Removable elements such as a cartridge filter can be brushed or ultrasonicated in validated sinks using specified detergents, with defined temperature, time, and number of passes in the SOP.

Worst‑case selection is central. Plants validate against the hardest‑to‑remove or most hazardous API (e.g., lowest solubility, highest potency) to cover all routine products (pmc.ncbi.nlm.nih.gov). One case identified the very water‑insoluble and toxic Oxcarbazepine as the worst case for shared lab equipment, and a partnering company reinforced that choice (pmc.ncbi.nlm.nih.gov).

Validated CIP sequence parameters

A representative CIP cycle follows a controlled sequence: pre‑rinse with water (often warm) to remove bulk product; detergent wash — heated caustic or enzymatic detergent recirculated for a fixed time (e.g., 30–60 minutes) at controlled temperature and concentration; intermediate rinses; acid wash or sanitizing step if needed (e.g., pH below 3 for passivation or scale removal); final rinse with purified water until analytics confirm clean; and drying (air blow‑out or vacuum).

One validated one‑pot processor example: 35 L of 40 °C water for prewash, about 80 L of 60 °C alkaline detergent (pH ~12.5), and ~110 L of rinse water (60 L cold wash + 50 L final rinse). The cycle lasted ~90 minutes plus ~30 minutes drying and removed both a water‑soluble drug (theophylline) and a water‑insoluble drug (mebendazole) below acceptance levels (www.pharmtech.com) (www.pharmtech.com).

Statistical reproducibility and controls

Validation demands reproducibility: typically three consecutive runs. In one data set, four consecutive theophylline batches were cleaned and sampled; low variance in residues confirmed robustness. Deviations like a 24‑hour delay before cleaning were also challenged (www.pharmtech.com).

Automated CIP logs critical parameters — pump flow, temperature, detergent strength, time — often in SCADA (supervisory control and data acquisition) to ensure identical cycles. Accurate detergent feed is typically metered with a dosing pump. COP relies on training and adherence to SOPs for consistency.

Surface sampling: swab and rinse methods

PIC/S accepts two complementary approaches for residue recovery on equipment: direct swab (wipe) sampling and indirect rinse (flush) sampling (gmpua.com) (process-technology-online.com).

Swab sampling involves wiping a defined area — typically 25–100 cm² — with a pre‑wetted inert swab (polyester or cotton), chosen with a solvent that matches API chemistry for recovery (gmpua.com) (pmc.ncbi.nlm.nih.gov). One protocol moistened a swab with 2 mL water and wiped a 100 cm² stainless area using horizontal and vertical strokes; both sides of the swab were then extracted in solvent for 10 minutes (or ultrasonicated), filtered, and analyzed (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Swabbing physically dislodges dried or insoluble deposits but introduces operator variability and requires swab material blanks.

Rinse sampling washes or flushes a known solvent volume over or through the equipment’s wetted surfaces, then collects it for analysis. In closed systems, the final rinse water can be collected; for open vessels, a defined volume is applied. One lab protocol used two sequential 5 mL washes (10 seconds each) for a total of 10 mL per item (gmpua.com) (pmc.ncbi.nlm.nih.gov). Rinse tests are reproducible and reach hidden areas but rely on sufficient residue solubility in the chosen solvent (gmpua.com) (gmpua.com).

In practice, a combination of swab for hard‑to‑reach or insoluble residues and rinse for full‑system coverage is ideal (gmpua.com) (gmpua.com).

Analytical assays and method validation

GMP requires validated, specific analytical methods with sensitivity at or below the acceptance limit (pubmed.ncbi.nlm.nih.gov). HPLC/UPLC (high/ultra‑performance liquid chromatography) with UV, tandem MS, or other detectors is typical for small‑molecule APIs, with published examples reporting detection down to single ng per swab (www.pharmtech.com) (pmc.ncbi.nlm.nih.gov). GC–MS (gas chromatography–mass spectrometry) is used if residues are volatile or semi‑volatile.

Non‑specific checks such as TOC (total organic carbon) and conductivity confirm global organic/inorganic cleanliness, including API, excipients, and cleaning agents (pubmed.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). In the one‑pot processor example, final rinse conductivity matched purified water, indicating no detergent remained (www.pharmtech.com). Some plants install online monitors — in‑column TOC or conductivity probes — to control CIP in real time (process-technology-online.com).

Each assay must be validated for accuracy, precision, linearity, and LOD/LOQ fit for the limit. Swab/rinse recovery is documented by spiking stainless coupons or real surfaces, typically demonstrating ≥70–80% recovery for the combined sampling + analysis process (pmc.ncbi.nlm.nih.gov). For high‑potency APIs, LC–MS/MS (liquid chromatography–tandem mass spectrometry) is increasingly used to achieve lower detection limits.

Acceptance criteria and health‑based limits

Legacy examples include criteria such as no visible residue, ≤10 ppm in the next product, ≤0.001× daily dose, or a fixed surface limit (historically ~1 µg/cm²) (www.pharmtech.com) (www.pharmtech.com). Current practice favors health‑based ADE/PDE (acceptable/permitted daily exposure) over fixed ppm rules (www.pharmtech.com).

Examples from the literature: an absolute surface limit of 1 µg/cm² for the active and 10 ppm for detergent in the one‑pot processor case (www.pharmtech.com); and in another study, a 10 ppm (0.01 mg/mL) threshold for Oxcarbazepine based on its PDE. Regulators accept that highly sensitive assays may detect tiny residues; results are acceptable provided they sit below the scientifically justified limit — zero is not required (www.pharmtech.com) (www.pharmtech.com).

Performance data bears this out. In the one‑pot processor CIP, all critical surfaces — filter, impeller blade, chopper, bowl, valve cover — showed theophylline residues well below the 1 µg/cm² limit, even with a 24‑hour cleaning delay (www.pharmtech.com). A few hard‑to‑wet spots (impeller wingnut, bowl seal) had slightly higher variation but stayed under the limit (www.pharmtech.com). One design feature — the impeller lipseal — exceeded the limit for the water‑soluble drug but not for the insoluble one, highlighting the need to optimize that zone or improve CIP coverage (www.pharmtech.com).

Outcomes, efficiency, and audit readiness

A robust CIP/COP program translates into hard metrics: “<X ppb of API on all surfaces” or “no growth in final rinse cultures,” reduced occupational exposure, and minimized downtime. The validated CIP cited above used ~200 L total water/detergent and fit within a single production shift — versus the days sometimes needed for manual soaking (www.pharmtech.com) (www.pharmtech.com).

Quality teams benefit from harmonized, data‑rich documentation: cleaning maps, swab/rinse results, and validated HPLC/TOC/conductivity assays aligned to ADE/PDE‑based limits. Re‑qualification on a defined cadence (e.g., annually or after equipment change) verifies performance over time. For sterile operations, biological assurance (BI challenge tests of sterilization steps) or ATP swabs may be part of the broader control strategy, though they sit outside chemical residue testing.

Bottom line: risk‑based CIP/COP methods, PIC/S‑endorsed sampling strategies, and quantitative analytics prove cleanliness — and keep plants audit‑ready in Indonesia and globally (klikcpob.pom.go.id) (gmpua.com) (process-technology-online.com) (www.tsaprocessequipments.com).