Finding an Efficient, Cost-Effective Package Testing Method

By Erik Swain

As medical device manufacturers demand efficiency and FDA demands consistency, packaging engineers are under more pressure than ever to have their test methods operate cost-effectively and under control. Fortunately, test-method developers and standards-setting bodies have been taking steps to make this task easier.

COST-EFFECTIVENESS OF NONDESTRUCTIVE METHODS

In recent years, medical device packaging engineers have begun to understand the value of nondestructive package-testing devices. Nondestructive methods reduce waste, promote efficiency and, depending on how they are applied, can be used to check every package, rather than a mere sampling of an entire lot.

"We've been looking for a method based on science that could replace the current visual inspections that we all use," says John Spitzley, associate fellow–packaging for device manufacturer Medtronic Inc. (Minneapolis). "It could also replace the destructive tests, which you can only do on surplus or on empty packaging. Destructive tests have other limitations, from sensitivity to overall messiness. If it is done quickly enough, a nondestructive method could be used to do 100% inspection. Or at the very least, it could be a validated way to do a sampling."

One nondestructive testing system that attracted attention was True Technology Inc.'s (Newton, MA) SealCheck 210, which quantified leaks in porous packages. The device worked by introducing helium into a package and scanning the seal with a sampling probe. By showing how much helium escaped, the device could pinpoint the size of channel leaks. It was a highly automated system and incorporated data collection features for validation.

Helium leak detection can identify very small leaks.,
 

While device companies expressed interest in the technology, few made purchases—almost entirely due to the cost, approximately $75,000. Unfortunately, the slow sales forced True Technology to cease operations in July.

But the technology may live on. Mocon Inc. (Minneapolis) purchased the intellectual property rights to it and will design another system around it.

"The device was very nice, but there were a lot of price problems with it," says Dane Anderson, Mocon's acting chief financial officer. "People did not want to pay that amount of money. We plan to design and reintroduce a new system in the very near future. It will be the same concept, but more affordable. We plan to put a lot of resources behind this technology because the market potential looks big." Mocon will not use the SealCheck name, though. It has a line of equipment called Pac Guard, and the new name could derive from that, Anderson says.

True Technology had begun work on getting the technology its own American Society for Testing and Materials (ASTM; West Conshohocken, PA) standard, and Mocon will add a representative to ASTM subcommittee F02.60 on medical packaging to continue that work, Anderson says. The company will also make a great effort to work closely with device companies, FDA, and DuPont Medical Packaging (Wilmington, DE), whose Tyvek is the lidding for most porous medical packages, to promote acceptance of the technology, he says.

According to Spitzley, industry's arguments against using the technology were twofold: "It's only packaging; why should we spend any money on it?" and "If it ain't broke, don't fix it." But, he says, "there are problems with those arguments. If we don't have good packaging, then we don't have a good product. And just because the perception is that there are no problems does not mean there aren't. You may have a problem and not realize it."

While the True Technology/Mocon device tests porous packages, there are nondestructive testing methods for nonporous packages. One is the use of Linear Variable Displacement Transducer (LVDT) sensors, says David Goff, marketing director of Uson L.P. (Houston). If a vacuum is pulled on a flexible pouch, it expands and pushes on the LVDT, which measures displacement and confirms the presence or absence of a leak, he explains. "We can build big machines that test 20 to 30 bags at a time and can reject a particular package in the matrix. There is also a method using a light beam that causes no friction."

Another nondestructive test system for nonporous packages was recently released by T.M. Electronics (Worcester, MA). "It works on the principle of a surrogate chamber test and can be used with either pressure or vacuum decay," says Stephen H. Franks, vice president and principal. "The instrument can sense pressure decays of 0.0001 psi, which can be equivalent to leak sizes of 5 µm or less."

Also for nonporous packages is ITI Qualitek's (North Billerica, MA) nondestructive tester for nonporous packages. The Qualipak Q700 uses strain gauge technology under a vacuum to detect holes as small as 12.5 µm.

Attention is also being given to acoustic micro imaging (AMI), which has long been used in the materials and semiconductor industries for nondestructive inspection of various package types. "The strong point of AMI is its ability to image internal air gaps nondestructively," notes Lawrence W. Kessler, president of Sonoscan (Elk Grove Village, IL). "Any internal air gap — otherwise known as a delamination, a channel, a void, or a disbond — reflects all of the high—frequency ultrasound reaching it. In contrast, well-bonded internal interfaces reflect only a portion of the ultrasound. This property offers two valuable abilities: you can see acceptable internal features such as the boundary between two materials, and you can see all gap-type features, even if the air gap is less than 0.1 µm thick."

Sonoscan has already begun testing numerous medical package types for a large number of U.S. firms. To date, the key benefits are in process development, where internal defects can quickly be found and remedied, as well as in batch sampling of production lines, where defect trends can be identified and corrected.

STANDARDIZATION

Efforts in progress at ASTM to standardize certain test methods are helping packaging engineers control their in-house package tests.

At an April meeting in Toronto, Hal Miller, director of packaging technology for Johnson & Johnson (New Brunswick, NJ) and the chairman of subcommittee F02.60, announced that he had submitted several standards to FDA to try to get them recognized as consensus standards. The idea, he says, is for device manufacturers to preempt some of an inspector's questions on test methods by showing they have followed a standard. However, "they may still ask you to validate your test methods," he said in April. "Maybe that will go by the wayside as we get better."

The standards submitted were D3078 (bubble leak test), F1886 (visual inspection), F1929 (dye penetration), F1980 (accelerated aging), F1608 (microbial ranking of porous packaging materials), F88 (seal strength–flexible barrier materials), and F1140 (unrestrained burst testing).

ITI Qualitek's Q700 tests packages up to 8.5 x 10.5 x 4 in.
 

He said he hopes to hear a response from FDA by the next subcommittee meeting, which will be held October 11–13 in Orlando, FL. ASTM is also working on adopting a guide on design and evaluation of primary packaging for medical products. The draft is based on a decision tree prepared by a Flexible Packaging Association (FPA; Washington, DC) working group. It is intended to show packaging engineers at device companies what tests they should run to evaluate materials and packages they receive from suppliers, or packages they make themselves if they are doing in-house form-fill-seal. The draft presented in April was written for flexible packages, but the subcommittee expressed interest in extending it to rigid packages as well. The measure might be ready for subcommittee ballot in October.

In other developments, the committee approved a new standard for restrained burst tests of flexible packages, which will serve the same purpose that F1140 does for unrestrained burst tests. It should be assigned a number and published soon. Two revisions of standards, F1585, "Guide for Integrity Testing of Porous Barrier Medical Packages," and F1608, "Microbial Ranking of Porous Packaging Materials," also received final approval in April and have been submitted for publication.

Franks of T.M. Electronics is spearheading a new standard for pressure-decay leak testing by means of pressure inflation. The basic ruggedness and sensitivity tests have been done, and the round-robin tests, in which the method is used at several laboratories and evaluated for efficacy and consistency, should be completed by the October meeting, he says.

Also in progress is a new standard on an internal pressurization bubble test. At the April meeting, the subcommittee debated whether this new standard should apply just to porous packages or to nonporous as well. That issue will be sorted out during round-robin testing. There was also discussion about absorbing the internal pressurization bubble test into Standard D3078, the vacuum leak bubble test, but Miller opposed that because there are significant differences between the two methods.

DEMANDING MORE FROM TESTERS

As medical device packaging engineers feel more pressure from FDA and from their own quality assurance departments to ensure that their packages have no defects, package-testing technology and standards should continue to evolve at a rapid pace.

One demand may be the detection of smaller leaks. On that count, helium leak detectors may have an advantage over other methods, says Jean-Pierre DeLuca, director of sales and marketing, helium leak detection, for Alcatel Vacuum Products (Hingham, MA). "Medical device manufacturers may want to see results down to 10–9 or 10–10 cm3/sec. Helium is a tracer gas and can do that," he says. "Pressure-decay methods stop at 10–3 or 10–4cm3/sec."

In order to choose the best test method, engineers must know the acceptable leak rate, DeLuca says. For very small leaks, only some methods will suffice. For larger leaks, a wider range of choices are available, and other parameters, such as repeatability, accuracy, and cost, should be considered, he says.

Franks notes, however, that "there is still great debate relating to the efficacy of the aerosol challenge test and defining leak sizes that will provide an effective barrier for sterility. Using leak-rate specifications for instruments does not effectively define the requirement for the package."

Even 100% in-line inspection may not be far off. "In the past, big companies have not wanted to put expensive quality-control devices on their form-fill-seal machines," Uson's Goff says. "They said, 'If we spent $250,000 on that machine, [packaging] should be OK.' But that [attitude] will change."

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