Plan twice; validate once is a prudent variant of the adage. Cleaning validation is a hurdle in many applications, including aerospace, microelectronics, pharmaceuticals, and medical device manufacture.

The term “validation” is often associated with life science applications that are regulated by the FDA or analogous agencies world-wide. We choose to broaden the use of the term to include verification and documentation of cleaning processes in any industry that produces critical product. In this broader context, cleaning validation involves assuring the efficacy for the product being assembled and assuring that the product does not compromise the health and safety of either assembly workers or users of the product. In this context we are discussing cleaning, not sterilization. That is, cleaning validation means demonstrating and documenting that interfering residue, alive or dead, is reduced to an acceptable level.

The first step in validation, before any of the paperwork or signature cycles are established, is setting up an effective, rational, cleaning system. Cleaning includes washing (or soil removal), rinsing, and drying.

VALIDATING A MYSTERY
Often, we are called in at the validation stage, only to find cleaning processes that have been adopted for reasons unknown to even those most familiar to the process. We see an assortment of aqueous cleaning agents used in a variety of immersion and ultrasonic processes, perhaps interspersed with solvent spray, wipe or immersion steps, usually involving isopropyl alcohol and acetone. When we ask why the processes were adopted, we may be told that legendary engineers, half a dozen years ago, thought the processes would work. The all-important rationale has been lost in the mists of time. The processes have become set in stone; now we have one month to validate cleaning. Such mystery cleaning processes can be a challenge to validate. A report saying “nice cleaning process!” is not sufficient.

BENCHMARKING
If the cleaning process was used in previous, well-established products involving similar soils, substrates, and end-use requirements, a benchmark approach can often be used. Specifically, if it worked before, relating the level of residue on the older product to the new product may be appropriate and sufficient.

In order to use benchmarking, it is crucial that any differences in materials of construction, design, and enduse be addressed. It is necessary to show why these differences do not negate the benchmarking with the prior product.

BEYOND BENCHMARKING
If the product is breaking new ground, the situation becomes more challenging. This is where coordination between design, performance, and chemistry is necessary. A “safe” level of any surface residue may require relative risk analysis. This analysis can determine whether specific or non-specific analytical testing will be needed. For example, if organic contamination is expected to be an issue but molecular identity of the contamination is not required, a non-specific test may be sufficient.

It can be more difficult where specific contaminants can poison the performance of the product, or, as in implantable medical devices or in pharmaceutical applications, specific contaminants, literally can be poisons. The first line of defense is to understand all process materials used in the application, to understand all potential contaminants, and then to eliminate or reduce problematic materials.

The desirability of researching the cleaning processes holds for both particulate and thin-film soil removal. Understanding the process, including the sources and consequences of potential contaminants, makes for a rapid, defensible validation process. Such testing also promotes rugged, high-quality, and profitable manufacturing processes.

In Part 2 of this series, we will discuss developing and rehearsing the validation.

Barbara Kanegsberg and Ed Kanegsberg, “the Cleaning Lady and the Rocket Scientist,” are independent consultants in critical and precision cleaning, surface preparation, and contamination control. They are the editors of The Handbook for Critical Cleaning, CRC Press. Contact them at BFK Solutions LLC., 310-459-3614; info@bfksolutions.com; www.bfksolutions.com.