Practical Guide to Water for Injection (WFI) in Final Rinse of Medical Devices

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Water for Injection (WFI) used in the final rinse of medical devices

is a critical factor in ensuring device safety and sterility.

Below is a comprehensive overview of relevant regulations, standards, and implementation requirements:

Definition and Key Requirements of Water for Injection (WFI)

WFI is high-purity water produced by distillation, reverse osmosis, or other suitable methods. It is sterile, pyrogen-free, and suitable for the final rinse of medical devices, sterilization, or other product-contact processes.

Critical Quality Attributes

Microbial Limits: ≤10 CFU/100mL (Chinese Pharmacopoeia, EP); USP recommends dynamic control based on intended use.
Endotoxin: ≤0.25 EU/mL (Chinese Pharmacopoeia, USP, EP).
Conductivity: ≤1.3 μS/cm (25°C).
Total Organic Carbon (TOC): ≤0.5 mg/L (USP, EP, Chinese Pharmacopoeia).
pH: 5.0–7.0 (Chinese Pharmacopoeia).
References: Chinese Pharmacopoeia (2020 Edition), USP-NF, EP, etc.

Key Domestic and International Regulations & Standards

Item	Ch.P (2020)	General Chapter	EP 10th Ed.	General Chapter	USP 43	General Chapter	JP 18
Preparation Method	Produced by distillation of purified water	0261	Prepared by distillation of legally compliant water or purified water	0169	Must comply with EPA/EU/WHO drinking water standards; may be treated for final purification (e.g., distillation)	1231	Prepared by distillation, RO, or UF from pretreated water; RO/UF must ensure microbial control and equivalent quality to distillation
Appearance	Mandatory	0902	Mandatory	4	1		Mandatory
pH/Acidity-Alkalinity	Mandatory	0631	NA		NA		NA
Ammonia	Mandatory	0808	NA	2.4.1	NA		NA
Non-Volatile Residues	Mandatory	Tested as purified water	NA	2.5.30	NA		NA
Nitrates	Mandatory	Tested as purified water	Mandatory		NA		NA
Nitrites	Mandatory	Tested as purified water	NA		NA		NA
Subvisible Particulates	Mandatory	0903	NA		NA	788	Mandatory

Item	Ch.P (2020)	General Chapter	EP 10th Ed.	General Chapter	USP 43	General Chapter	JP 18
Heavy Metals	Mandatory	0821	4	2.4.8	NA	231	NA
Total Organic Carbon (TOC)	Mandatory	0682	Mandatory	2.2.44	Mandatory	643	Mandatory
Conductivity	Mandatory	0681	Mandatory	2.3.38	Mandatory	645	Mandatory
Bacterial Endotoxins	Mandatory	1143	Mandatory	2.6.14	Mandatory	85	Mandatory
Microbial Limits	Mandatory	1105	Mandatory		2		NA

Chinese Standards

Chinese Pharmacopoeia (2020 Edition): Specifies WFI preparation methods (distillation), quality standards, and testing requirements.
Medical Device Good Manufacturing Practice (GMP): Requires final rinse water to meet WFI standards.
YY/T 1244-2014 "Aseptic Processing of Medical Devices": Mandates WFI-grade water for rinsing.

International Standards

USP-NF: USP <1231> stipulates WFI must be produced via distillation or equivalent methods.
European Pharmacopoeia (EP): Emphasizes microbial and endotoxin control for WFI.
ISO 13485:2016: Requires validation of water systems to ensure compliance with product requirements.
FDA Guidelines (21 CFR Part 820): Mandates medical device rinse water to meet pharmacopeial standards, with periodic system validation.

WFI Preparation Methods & Storage Requirements

Preparation Methods

Primary Method: Distillation (multi-effect distillation, vapor compression distillation).
Reverse Osmosis (RO) + Electrodeionization (EDI), subject to validation for pharmacopeial compliance.

Storage & Distribution

System Requirements: Circulating systems must maintain temperatures >70°C or <4°C to prevent microbial growth.
Pipeline Requirements: 316L stainless steel with electropolished surfaces (Ra ≤0.6 μm). Regular testing at points of use, supply, and return.
Packaging Requirements: Must comply with pharmacopeial standards, including:
YY/T 0681.1-2018 Test methods for sterile medical device package —— Part 1: Test guide for accelerated aging.
GB 18280.1-2015 Sterilization of health care products-Radiation-Part 1: Requirements for development, validation and routine control of a sterilization process for medical devices.
USP - NF2021 Chapter<87> BIOLOGICAL REACTIVITY TESTS, IN VITRO.
USP<88> BIOLOGICAL REACTIVITY TESTS, IN VIVO, etc.

BioLink provides WFI packaging material validation guide.

Final Rinse Process Requirements

Cleaning Validation: Must verify absence of contaminants (e.g., subvisible particulates, conductivity, TOC, microbes/endotoxins, residues).
Reference Standard: ASTM E3106-17 (Guide for Cleanliness Validation).

Implementation Recommendations for Manufacturers

Compliance Management

Align with target market regulations (China, USP, EP, etc.).
Monitor regulatory updates (e.g., Chinese Pharmacopoeia 2025 revision).

Risk Control

Audit WFI suppliers if outsourcing.
BioLink, a biopharmaceutical process solutions provider, offers WFI systems integrating advanced technologies:
Continuous Distillation: Multi-effect distillation ensures energy efficiency and pharmacopeial compliance (Ch.P/USP/EP).
Flexible Packaging: Multiple sizes to meet varying demand.
Compliance Assurance: Weekly pharmacopeial testing with Certificate of Analysis (COA) for regulatory adherence.

practical-guide-to-water-for-injection-wfi-in-final-rinse-of-medical-devices1.jpg

BioLink HydroLinX® WFI (Bagged & Bottled)

Frequently Asked Questions (FAQs)

Q: Can purified water replace WFI in final rinsing?

A: No. WFI is mandatory for sterile/implantable devices per YY/T 1244-2014.

Q: Can BioLink’s packaged WFI support regulatory audits?

A: Yes. BioLink provides full documentation (quality standards, production processes, materials, environment) for audit compliance.

Q: Is BioLink’s WFI suitable for injectable drug formulation?

A: No. BioLink WFI is for research/industrial use only, not therapeutic applications.

By adhering to these requirements, manufacturers can ensure compliance in final rinse processes and mitigate contamination risks. Implementation should be tailored to device type (e.g., implants, sterile products).

References

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