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Product conductivity is an important consideration when evaluating pharmaceutical package integrity using electrical inspection methods. The electrical properties of a liquid formulation can influence how a test system responds to defects within a package, making conductivity an important variable during method development and performance evaluation.

Pharmaceutical formulations can differ significantly in their composition and physical properties. Injectable solutions, ophthalmic products, buffers, and other liquid formulations may contain different concentrations of salts, ions, active ingredients, and excipients. These differences can result in variations in electrical conductivity, which may influence inspection results.

Understanding the relationship between product conductivity and package integrity testing helps manufacturers establish appropriate test conditions, evaluate method performance, and maintain consistent inspection results across different products and manufacturing conditions.

The Science Behind High Voltage Leak Detection

High Voltage Leak Detection (HVLD) is a deterministic method used to identify defects in liquid-filled pharmaceutical containers. The technology applies a controlled high-voltage electrical potential across the package and monitors the resulting electrical response. When the container is intact, its packaging material acts as an electrical barrier. If a defect such as a pinhole, crack, or other small opening is present, it can create a conductive pathway between the liquid product and the outside of the container.

Factors such as product conductivity, defect characteristics, container material, and test conditions can influence the electrical response. PTI’s MicroCurrent HVLD enables testing of lower-conductivity solutions, which traditional HVLD methods typically cannot accommodate. With appropriately established test parameters, MicroCurrent HVLD can provide rapid, objective, and repeatable inspection of suitable containers, including vials, ampoules, cartridges, and pre-filled syringes. Pre-filled syringe testing can examine sealing interfaces such as plunger, stopper, and needle-shield regions for potential package integrity defects.

MicroCurrent HVLD is a non-destructive, non-invasive technology that utilizes approximately 50% less voltage than conventional HVLD solutions, reducing voltage exposure to the product and environment.

Benefits of MicroCurrent HVLD Technology

• Non-destructive, non-invasive, no sample preparation
• Effective across all parenteral products, including extremely low conductivity liquids
• Lower voltage exposure produces no ozone, eliminating risk to the product and environment
• Listed in USP 1207 Chapter as recommended method for parenteral liquid package inspection
• Simplifies the inspection and validation process
• Scalable from the lab to production line

Product Conductivity and Why Conductivity Is a Key Inspection Variable?

Product conductivity refers to the ability of a liquid to conduct electrical current and is mainly influenced by the presence and movement of electrically charged particles within the formulation. For HVLD applications, conductivity is important because the liquid product provides the conductive pathway required for electrical measurement. When a suitable conductive product is connected to the external environment through a package defect, it can produce a measurable electrical response.

Different pharmaceutical formulations can therefore produce different HVLD responses under the same test conditions. A method developed for one formulation may not provide the same response for another product with different conductivity characteristics. Characterizing product conductivity during method development helps manufacturers understand the electrical behaviour of the formulation, establish suitable inspection parameters, and assess method robustness when product or environmental conditions change.

Factors That Influence Product Conductivity

• Formulation composition: Active ingredients, salts, buffers, and excipients can influence the electrical properties of a formulation. Different ionic components may result in different conductivity levels.
• Concentration: The concentration of dissolved ionic substances can affect how effectively the formulation conducts electrical current. Changes in concentration may therefore influence the HVLD response.
• Temperature: Conductivity can change with temperature as the movement of charged particles within the liquid changes. Testing at different temperatures may produce different electrical responses.
• pH: Changes in pH can affect the concentration of ionized components in a formulation, which may influence its conductivity.
• Ionic strength: The amount and mobility of dissolved ions contribute to the electrical properties of the product. Differences in ionic strength can therefore affect conductivity.
• Formulation changes: Changes to ingredients, concentrations, buffers, or other formulation components can alter the conductivity of the final product and may require evaluation of the existing inspection method.
• Storage and environmental conditions: Temperature variations and other conditions during processing or storage can affect the physical properties of the formulation and may influence conductivity.

Product conductivity can influence the electrical response generated during HVLD inspection. When a conductive liquid is present inside a package, a defect can create an electrical pathway between the product and the external environment. The resulting change in electrical current can then be detected as an indication of a potential package defect.

Changes in product conductivity can affect the electrical response produced by the same physical defect. This may influence signal strength, measurement consistency, and the ability to distinguish an intact package from one containing a defect. Different formulations using the same container configuration may therefore produce different HVLD responses.

For this reason, product conductivity should be considered during method development and validation. Evaluating representative product samples under defined conditions can help manufacturers establish suitable test parameters and acceptance criteria. Changes in formulation, concentration, or temperature should also be considered when they may affect conductivity and inspection performance. A well-characterized method can provide more consistent testing conditions and support reliable detection of package defects.

Conclusion

Product conductivity is an important variable when applying High Voltage Leak Detection to liquid-filled pharmaceutical containers, as differences in formulation composition, concentration, temperature, pH, and ionic content can influence the electrical response during inspection. Characterizing product conductivity during method development can help manufacturers evaluate the expected electrical response and establish appropriate inspection conditions, while evaluating conductivity alongside package configuration and known defect conditions can support method validation and performance assessment. By considering the relationship between product conductivity and HVLD inspection, pharmaceutical manufacturers can develop suitable testing approaches, improve measurement consistency, and strengthen package integrity evaluation across development, validation, and manufacturing.

Frequently Asked Questions

1. Why is product conductivity important for HVLD testing?

Product conductivity affects the electrical response generated during High Voltage Leak Detection. Differences in formulation, concentration, temperature, pH, and ionic content can influence the test response and should be considered when establishing suitable inspection conditions.

2. Can PTI’s MicroCurrent HVLD be used for pharmaceutical products with different conductivity levels?

Common deterministic CCIT technologies include Vacuum Decay Technology, Airborne Ultrasound Technology, Helium Leak Detection, and High Voltage Leak Detection (HVLD). The selection of a testing method depends on factors such as package design, packaging materials, product characteristics, and validation objectives. Yes. HVLD can be applied to a range of liquid-filled pharmaceutical containers, including products with low conductivity. However, the inspection method and test parameters should be appropriately established and evaluated for the specific product and package configuration.

3. How can manufacturers ensure consistent HVLD inspection results?

Manufacturers can characterize product conductivity during method development, evaluate representative samples under defined conditions, and consider factors such as temperature, formulation changes, package configuration, and known defect conditions. This helps establish suitable test parameters and supports consistent package integrity evaluation.

Container Closure Integrity (CCI) testing is widely applied to evaluate whether packaging systems prevent the ingress of gases, moisture, and microorganisms. With advancements in pharmaceutical and medical device packaging, testing technologies have become more sensitive and capable of detecting extremely small defects. While this improved sensitivity enhances detection capability, it can also increase the occurrence of false rejects, where packages without defects are classified as failures.

False rejects can lead to product loss, repeated inspections, and additional investigation efforts within manufacturing environments. These outcomes may disrupt production flow and introduce variability in quality assessment. In many situations, these rejections are not linked to actual defects but arise from inconsistencies in testing conditions, equipment setup, or interactions between product and packaging materials.

A more structured approach to testing can reduce these inconsistencies. Factors such as calibration accuracy, parameter selection, environmental stability, and system performance influence how results are generated and interpreted. In addition, the use of quantitative, deterministic technologies provides clearer measurement outputs that reduce ambiguity. By understanding the sources of variation and refining testing strategies, manufacturers can improve result consistency and reduce unnecessary rejection of acceptable packages across development and production stages.

Main Causes of False Rejections

• Improper Calibration: Inaccurate or inconsistent calibration can shift baseline readings and affect measurement thresholds. This may cause normal package responses to be interpreted as defects during testing.
• Incorrect Test Parameters: Test pressure, cycle time, and sensitivity settings that are not aligned with packaging characteristics can distort results. When parameters are too aggressive or poorly configured, acceptable packages may be flagged as failures.
• Environmental Variations: Changes in temperature, humidity, and ambient pressure can influence measurement signals during testing. These variations can introduce instability and lead to inconsistent or misleading outcomes.
• Product and Packaging Interaction: Headspace volume, material flexibility, and product properties such as viscosity or conductivity can affect how signals are generated. These factors may create responses that resemble leaks even when the package is intact.
• System Noise and Signal Instability: Background noise or fluctuations within the testing system can interfere with signal clarity. This can result in inaccurate readings and increase the likelihood of false rejection.
• Operator Handling Differences: Variations in sample placement, orientation, or handling can introduce inconsistencies in measurement. These differences are more noticeable in semi-automated systems where manual interaction is involved.

Solutions to Minimize False Rejections

• Regular Calibration and Verification: Routine calibration using traceable standards keeps instrument performance aligned with defined detection limits. Periodic verification helps identify drift and improves consistency in measurement results.
• Optimization of Test Conditions: Adjusting pressure levels, test duration, and sensitivity settings based on packaging format improves result accuracy. Properly optimized conditions help distinguish between actual leaks and normal package responses.
• Controlled Testing Environment: Maintaining stable environmental conditions reduces external influences on measurement signals. Consistent temperature and pressure conditions improve repeatability across test cycles.
• Use of Deterministic Technologies: Methods such as Vacuum decay, high voltage leak detection (HVLD), and Helium rely on measurable physical changes. These technologies generate quantitative outputs, reducing reliance on subjective interpretation.
• System Maintenance and Noise Reduction: Routine maintenance of equipment helps maintain stable system performance over time. Signal filtering and noise reduction techniques improve measurement clarity and reduce interference.
• Standardized Procedures: Consistent sample handling, loading, and testing protocols reduce variability across operators and shifts. Clear procedures improve repeatability and minimize human-induced differences.
• Validation with Calibrated Defects: Using known leak standards during method development helps define realistic acceptance criteria. This approach improves confidence in the system’s ability to differentiate between acceptable and defective packages.

Reducing false rejects in CCI testing involves refining both technical and operational aspects of the testing process. Careful calibration, optimized test parameters, and stable environmental conditions help align measurement results with actual package integrity. Deterministic technologies offer consistent, data-driven outputs that reduce ambiguity during evaluation. Standardized procedures further limit variation introduced by manual handling or interpretation.

By addressing these factors, manufacturers can reduce unnecessary product rejection, improve process efficiency, and gain clearer insight into packaging performance. A structured and consistent approach to integrity testing leads to more reliable outcomes across development, validation, and production environments.

Several leak detection methods, that are deterministic and non-destructive, are already available in the market. Pharmaceutical companies are urged to use technologies that significantly enhances quality assurance and leak detection rates. Appropriate leak detection technology is selected based on the specific characteristics of the product and container, such as conductivity, headspace parameters, contents, or API. Historically, dye immersion and microbial immersion have been the two main methods of vial integrity testing. Recently, the USP has issued guidelines that require critical methods to achieve more reproducible and predictable outcomes. USP <1207> encourages a move towards more deterministic methods, recommending the avoidance of dye immersion tests and the use of quantitative, non-destructive technologies instead.

Why High Voltage Leak Detection Method is Preferred for Testing Vials?

High Voltage Leak Detection or HVLD is a deterministic, non-destructive leak detection method to evaluate vials, cartridges, and other liquid-filled parenteral products for Container Closure Integrity. The current generation of PTI’s MicroCurrent HVLD may be utilized with a wide range of liquid-based products, from low conductivity sterile water for injection to highly proteinaceous drug preparations in suspensions. It is one of the most effective online container closure testing methods, requiring just minor infrastructure modifications. When compared to conventional HVLD solutions, MicroCurrent HVLD utilizes approximately 50% less voltage and exposes the product and environment to less than 5% of the voltage. This method is non-invasive and requires no sample preparation. Like vial leak testing, another major application of MicroCurrent HVLD is pre-filled syringe testing.

Working Principle of MicroCurrent HVLD Technology

In this method, the container is scanned using a set of high voltage electrode probes. A high voltage is applied to one side of the container, while a ground probe is attached to the other. If there is no leak in the package, the two container walls (high voltage side and ground side) offer complete electrical resistance, and no substantial current is measured flowing through the vial. If a micro-leak or fracture occurs in one of the container walls, the break-down resistance is achieved, and the current flows through. HVLD is the only leak detection method that does not require mass to travel through a defect location, instead of requiring just electricity to pass through a crack. Because of this feature, HVLD is sensitive to leaks that conventional leak detection technologies are unable to detect.

MicroCurrent HVLD Technology Advantages

• Deterministic and non-destructive test method.
• High level of repeatability and accuracy.
• Ensure more accuracy and dependability in results.
• At high production rates, both offline and 100% online inspections are performed.
• Simplifies the inspection and validation procedure.
• Highly effective in all parenteral preparations, even liquids with extremely low conductivity (WFI).
• Outlined in the USP 1207 Guideline.

Pharmaceutical containers like vials protect the product from contamination (sterile barrier) and prevent changes in product quality caused by external factors. In order to determine the functionality of such systems, container closure integrity testing is performed. CCIT provides sophisticated analytical methods for evaluating pharmaceutical containers.

Prior to commercialization, the development of new pharmaceuticals, particularly combination treatments, was a complicated process involving extensive research. When it comes to packing pharmaceuticals for patient use, several things must be considered to ensure that they satisfy the highest quality requirements and are safe to use.

Nowadays, the challenge of adopting traditional glass or specialized polymers as combination products has become common. Similarly, the demand for scientific evidence to support regulatory requirements for the pharmaceutical industry has also become more prevalent. For effective development and commercialization of a pharmaceutical product, it is important to understand the compatibility and performance of the primary packaging system with both, the pharmaceutical product and the delivery systems, regardless of the material.

Container Closure Integrity (CCI)

Container closure integrity (CCI) testing is important when ensuring the quality of all packaged products, especially when it comes to parenteral drugs. To evaluate the CCI of the packaging system, a pharmaceutical manufacturer must calculate the Maximum Allowable Leakage Limit (MALL) for the pharmaceutical product. MALL is defined by USP<1207> Package Integrity Evaluation – Sterile Products as the highest leak rate that may be tolerated for a specific packaging method while posing no harm to the safety and quality of the pharmaceutical product over its shelf life. In comparison to probabilistic approaches, USP <1207> provides guidelines on how to assess CCI, including deterministic methods, which are strongly encouraged. Helium leak detection, MicroCurrent HVLD, and Vacuum decay- are deterministic techniques. For the given system, these techniques must be created and validated.

Test methods

MicroCurrent HVLD

MicroCurrent HVLD is a non-destructive technique for determining the integrity of container closures for a variety of parenteral liquid products, including ultra-low conductivity sterile water for injection (WFI). A non-conductive container is examined for pinholes, micro-cracks, plunger leakage, and non-visible crimping leaks, among other things, using an electrode probe. Whenever a defect is identified, it causes a change in current flow and resistance differential, which indicates a breach in the container. The MicroCurrent HVLD is a High Voltage Leak Detection method effective across all parenteral products.

Helium Leak Detection

Helium leak detection is a deterministic method used to detect leaks in pressure vessels and other enclosed systems. In this technique, helium is used as a tracer gas. The change in helium concentration as it escapes through the container is monitored. For helium-based leak detection systems, the Seal Integrity Monitoring System (SIMS) 1915+ is a perfect choice. Helium as a tracer gas delivers excellent levels of quantitative accuracy when compared to traditional vacuum bubble and dye penetration test techniques. Helium is an optimal solution for product quality monitoring across the product lifecycle.

Vacuum Decay

A non-destructive CCI test method for evaluating medical device package integrity. Non-destructive testing improves package quality while decreasing waste when compared to destructive testing. This testing also saves time and money while ensuring product quality. This method operates by enclosing sample packages in a tight-fitting evacuation test chamber with an external vacuum source. A single or dual vacuum transducer is utilized in the test chamber to measure the level of vacuum as well as the change in vacuum over a pre-defined time period. The existence of leaks and defects is indicated by fluctuations in the package's absolute and differential vacuum.

Regardless of the pharmaceutical product, type of materials, devices used, developing a complete testing plan from initial compatibility to stability and release is critical. To assure the availability of scientific data that helps ensure optimal results for patients as well as rapid regulatory approval and delivery to the market, proper testing is required.

High Voltage Leak Detection (HVLD) of pre-filled syringes, vials, cartridges, ampoules, BFS, bottles and liquid filled pouches detects pinholes, micro-cracks, stopper/plunger leaks, non-visible leaks under crimping and many other defects. The HVLD testing procedure also guarantees the security of the product seal by finding tiny pinholes, micro fractures and screen defects that are not visible. Eventual packing defects lead to resistance differential and changes of current flow in the container and the approximate position of the fault. It is also one of the most affordable methods for testing container closure that requires little adjustments to the infrastructure. This technology is not invasive and does not require preparation of the sample. It is one of the most powerful CCI technologies for all biological and parenteral goods

E-Scan HVLD has a high-speed test cycle, produces highly reproducible results and is easy to handle. Fast changeover and easy adjustments of test parameters for various goods and applications are further advantages. Another advantage of the HVLD technique is that it can readily be moved from the laboratory offline to 100% online testing applications at high production speeds. That is an enormous benefit and makes the inspection and validation procedure globally simpler. E-Scan employs a number of electrode probes to scan a sealed container which is not conductive. Glass, plastic or poly laminate might be the container material.

Working principle of MicroCurrent HVLD technology

In non conductive or semi-conductive packing materials, HVLD works by implementing high voltage potential for electrically conductive goods. When electrical discharges between goods and device electrodes are observed, the pinholes are determined. The two container walls (high voltage side and ground side) offer complete electric resistance when the package is not leaked, and no significant current is detected by flash. If one of the container walls has a microleak or fracture, the barrier to breakup is met and the current passes. HVLD is the only technique for leak detection that requires a crack site without mass, needing just the flow of electricity via a crack. This feature sensitises HVLD to leaks that are not identified by typical leak test systems.

Applications of MicroCurrent HVLD

• Pre-filled syringes
• Vials
• Cartridges
• Ampoules
• BFS
• Bottles
• Pouches

Advantages of MicroCurrent HVLD

• High level of repeatability and precision
• Deterministic, non-destructive, non-invasive
• Product and environmental low voltage exposure
• Offline and 100% online testing at high production speeds
• Simpler inspection and validation procedure
• Most powerful CCI technology for all parenteral and biologic products
• Robust method and approximate 3x Signal-Noise-Ratio for a wide range of product classes and package formats