FEATURE
Joyce Laird
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In the medical arena, the goal is always to present a sterile, zero-defect product to the end user. Not only must the product itself be perfect, but the packaging must be free of defects that could compromise the integrity of the contents. To ensure package integrity, manufacturers may rely on both destructive and nondestructive test methods. In the past, nondestructive package testing methods tended to be time consuming, and the equipment was expensive and complicated to use. Today, suppliers are offering better solutions, and device manufacturers are taking heed.
Ultrasonic testing
Traditional ultrasonic technology requires the test piece to be placed in contact with a wet physical coupling. Although very effective, moisture contact rules out the use of this technology for 90% of medical and pharmaceutical packaging.
In response, PTI / Packaging Technologies and Inspection (Tuckahoe, NY, USA) has developed air-coupled ultrasonic testing. Air is the only coupling medium used, and no special package preparation is needed prior to testing. The technology is suited for seal-integrity testing on a full range of nonrigid packaging, such as heat-sealed pouches, sachets, and some blister packs, as well as porous packaging. In addition to basic package integrity testing for air, this technology will identify defects such as voids, delamination, foreign materials, inclusions in the seal and misaligned seals.
In air-coupled ultrasonic testing, focussed high-frequency sound waves are fired in 200-Hz pulses through the seal area under inspection. A sensitive noncontact receiver detects and interprets the transmitted ultrasound signal and shows the results in a visual display.
The company’s Seal Scan Airborne ultrasound inspection technology is capable of testing many types of packaging materials, including aluminium, foil, paper, Tyvek or any combination thereof, according to Michelle Wolf, marketing communications. “PTI offers configurations for R&D, quality and process control as well as 100% on-line inspection. All use the same principle of operation,” says Wolf.
Using this technology, the package or pouch passes through the scanning area and the ultrasonic wave goes through the package making no contact with the product. “ It is truly an analytical tool,” says Wolf. “It’s not just telling the user that a seal is bad. It indicates the exact type of defect that is occurring with a visual image and quantifiable data.”
Airborne ultrasonic testing is a huge step forward, but there is still a place for standard ultrasonic methods, according to Jack Richtsmeier, new business development manager for Sonoscan Inc. (Elk Grove Village, IL, USA). He cites one high-end medical company that makes a saline pouch used as a calibration device for blood diagnostics machines. Because it is a wet-seal package, says Richtsmeier, “the company has no qualms about using our technology to test those saline package seals.”
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Figure 1: An ultrasound of a foil-to-foil seal shows poorly bonded material in red. The image produced using a Sonoscan system reveals numerous voids within the seal.
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Sonoscan has developed a method of using waterfall transducers and spray nozzles to limit water contact to small surface areas (Figure 1). “The waterfall can hit at an angle, and the transducers producing the ultrasound can be 1/8 to 1 inch from the part, depending on the application,” Richtsmeier says. “Our technology can scan down to 5 µm,” he adds.
Vacuum decay leak testing
The Association for Standards Testing and Materials (ASTM) International has approved vacuum decay leak test technology methods for different types of packages including flexible, rigid, and semi-rigid designs and packaging with porous and nonporous barrier lidding materials such as Tyvek. There are subtle differences in the way various testing instruments work, but they share some basic similarities.
All vacuum decay leak testing is done using some type of closed chamber, typically custom designed to fit the product to be tested. Because every package has atmospheric pressure on the inside, when air is evacuated from the chamber it creates inside-to-outside differential pressure. As air leaves the package and goes into the chamber, it drives up the vacuum level. The more air that leaves the package, the less trustworthy the package is. Basically this method converts internal chamber changes into electronic signals that feed into proprietary software that indicates the degree of leakage, if any.
A vacuum test chamber developed by Test-A-Pack Systems, a division of Carleton Technologies Inc. (Orchard Park, NY, USA), incorporates a pressure transducer that comes down and makes contact with the package as the vacuum is drawn. The pressure transducer then rises up, creating an electrical signal that goes through a series of software algorithms. If there is even the smallest leak, the pressure transducer drops down and the electronic signal indicates a pass/fail.
Although this nondestructive test unit is manufactured for a specific medical device manufacturer, Jim Zynda, sales manager, explains that the company is currently working on the development of a benchtop unit for a wider medical and pharmaceutical audience.
“The benchtop unit will make this very practical and affordable to pharmaceutical companies that want to do off-line testing or laboratory testing. It’s about a year away,” Zynda says. “We can detect leaks down into the micron range; 0.02 in. is what we’ve actually proven with this system.”
PTI also offers vacuum decay test equipment. Its VeriPac differential pressure and vacuum decay system is used for the full range of package integrity testing per ASTM F2338-05 Test Method and Recognized FDA Standard for Package Integrity Testing.
“We use either single or double transducers, depending on the sensitivity needed,” Wolf says. “The transducer is connected to a test chamber, designed to fit exact product dimensions. The ASTM method was developed using PTI instruments,” Wolf adds. “In March 2005, FDA recognized test method ASTM F2338-05 as the standard for package integrity testing. It has the stamp of ASTM, which is very important, and it also has the stamp of FDA, which is a tremendous advantage in the medical industry.”
T.M. Electronics (Boyleston, MA, USA) offers three different instruments for this type of test, all of which use chambers designed to product dimensions. The technique applies either vacuum or differential pressure to the package (Figure 2). “This gives an accurate indication of leak integrity, and it can be applied in many different ways,” says Stephen Franks, executive vice president. “It’s a system that can be applied to practically any type of packaging made from any nonporous materials.”
All T.M. systems are designed for benchtop use. “We can actually take a CAD model of a package or bottle and mould a matching shape around it to create the chamber,” Franks says. “This method allows the customer to use either vacuum or positive pressure to test the package with the product included. Because the systems offer a high resolution of 0.0001 psig (0.007 mbar), very small leaks on the order of 5 to 10 µm can be detected.”
Testing rigid containers
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Figure 2: Testing systems from T.M. Electronics can apply vacuum or differential pressure to the package.
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Uson L.P. (Bury St. Edmunds, Suffolk, UK) offers single- and dual-channel Qualipak testers for both small and large pouches or packaging. According to Rudolph Fuentes, technical sales specialist at the company’s US headquarters, these pressure-decay testers can be designed to test all forms of rigid containers quickly to high levels of sensitivity.
“There is a force sensor in the tester, and we pull a vacuum off the package itself,” explains Fuentes. “When the package expands, it is pushed down against this force sensor. Based on the force generated with that particular package, we can set up parameters. When the force falls within these parameters, it’s a good package; if it falls outside, it’s determined to be defective. It’s very similar to leak testing but instead of using air and a pressure sensor, we’re using a force sensor,” he adds.
A unique nondestructive test lab
Medical Engineering Technologies (M.E.T.), headquartered in Hythe, Kent, UK, is strictly a test service provider and uses a unique technique. “We provide hydrogen trace testing,” explains sales manager Mark Turner. “We fill a pouch (typically made of any combination of foil materials) with a 5% hydrogen mixture and nitrogen, and then we use a highly sensitive probe that gives us a quantitative measurement and the location of any leak. This type of testing is used on pouches designed for very critical applications including cryogenic preservation and DNA samples.”
Turner says that the gas quickly dissipates over time, so the test is still considered to be nondestructive. The integrity of the pouch is not breached. “This is because hydrogen is such a tiny molecule. It can find extremely minute holes. This is important for areas like in vitro diagnostics, where moisture entry and sterility are concerns,” he says.
PTI, Sonoscan, T.M. Electronics and Test-a-Pack all also offer their own versions of nondestructive test services on a global basis for companies that prefer to send in samples for testing rather than buying equipment.
“Time to market is often critical and things can get hung up when a product is going through the chain of approval,” says Wolf. “The R&D team and packaging people may be desperate, because they can’t move forward with a new product or package design without having some testing protocol in place. Sending [the product] to a qualified service provider is a good interim solution that keeps the flow going.”
Meeting ISO 11607
DDL Inc. (Eden Prairie, MN, USA) provides services in the areas of environmental testing and dynamic testing. “When FDA started to regulate the design and manufacture of packaging for sterilised medical devices, we came up with some protocols that a medical device manufacturer could perform in compliance with the requirements of ISO 11607,” says chief operating officer Patrick Nolan.
Part of that standard requires the manufacturer to perform package validation, and this involves accelerated aging or shelf-life studies. This covers any type of medical device that is terminally sterilised and the same requirements apply to nonporous medical and pharmaceutical packaging. Everything has some type of shelf life, and everything needs to be shipped in some manner; therefore everything needs to hold up to both life expectancy and the rigours of shipping.
In the case of a product with a 1-year shelf life, Nolan explains, “we would put the package into a test chamber at 55°C for 40 days. It would then be removed, and samples would be pulled for integrity testing,” he adds.
“We also expose the product to forces that it might be subjected to while being transported or handled by people or machines,” says Nolan. “We do shock, drop, and vibration testing. We put compressive forces on the packaging and we do this all in a sequential manner. It goes from one test to another to try to simulate shipping and handling. Typically, we wind it all up with a nondestructive type of test,” Nolan adds. “More times than not, it would be a vacuum leak test.”
Bottom-line benefits
While many medical device manufacturers will choose to rely on destructive package testing, as the pressure for increased inspection ramps up it might be good to consider investing in the addition of one or more of the newer nondestructive test methods. Nondestructive testing opens the field to testing unlimited products since the integrity of the product is never breached. With new systems and technologies to choose from, adding nondestructive package testing is easier and more cost effective than ever before.
