Glass Cartridges: HVLD and Helium Leak Detection for Pen and Auto-Injector Systems

Overview

Glass cartridges — the small-format, dual-seal containers used in pen-injector and auto-injector delivery systems — are tested using both of PTI's primary technologies, applied in a complementary rather than either/or fashion, because the cartridge's two closures (a plunger/stopper at the fill end and a crimped or pierceable septum at the delivery end) behave differently under each method.

For HVLD , the cartridge is rotated past a voltage probe while a detector monitors for the current spike indicating a conductive breach; cartridge HVLD programs consistently demonstrate accurate, repeatable discrimination between intact and defective units down to the 5 micron range across multiple analysts and test days, with the plunger/stopper seal typically the more reliably resolved of the two closure regions. Helium leak detection is used on cartridges as an absolute, quantitative complement, most often to characterize and confirm the crimp-seal and stopper-seal regions independently against a defined Maximum Allowable Leakage Limit.

Sample & Container Type

• Glass cartridges, typically 1–3 mL
• Used in pen-injector and auto-injector delivery systems
• Sealed with a plunger/stopper at one end and a pierceable septum or crimped cap at the other

Product Class & Rheology

• Liquid parenteral formulations, including biologic solutions filled to a defined delivery volume
• Frequently high-value, chronic-therapy injectable products
• Tested with device assembly and downstream handling considered in method development

General Test Method

HVLD recipes are developed and validated with multi-analyst, multi-day reproducibility testing. Helium testing runs each session against a certified external leak standard, reporting a quantitative leak rate (mbar·L/sec) against a defined MALL. Because cartridges are almost always paired with a specific delivery device, method development also considers whether the device's own assembly process — piercing the septum, seating the cartridge in a device housing — could plausibly introduce a defect the release test would need to catch.

Typical Findings & Sensitivity

HVLD provides a fast, sensitive, whole-container screening method suitable for routine or high-throughput evaluation, typically discriminating down to the 5 micron range, while helium testing provides a slower but absolute confirmatory result focused on the seal interfaces most likely to fail.

Frequently Asked Questions

1. Why use two different methods on the same cartridge?

HVLD and helium leak detection are complementary: HVLD is fast and sensitive enough for routine or high-throughput screening, while helium testing gives an absolute, regulator-recognized leak-rate number focused on the seal interfaces most likely to fail.

2. What sensitivity does cartridge HVLD achieve?

Programs consistently demonstrate accurate, repeatable discrimination down to the 5 micron range across multiple analysts and test days, with the plunger/stopper seal typically the more reliably resolved closure region.

3. Is helium testing needed if HVLD already passes?

It's often used as confirmation of component fit as a design tool, since it provides an absolute leak-rate number against a defined Maximum Allowable Leakage Limit.

4. Does the delivery device (pen injector) affect cartridge testing?

Yes. Method development considers whether the device's own assembly process — piercing the septum or seating the cartridge in its housing — could plausibly introduce a defect the release test needs to catch.

5. What cartridge size range does PTI typically test?

Most cartridge programs involve small-format containers, typically 1–3 mL, consistent with standard pen-injector and auto-injector cartridge designs.

Why Clients Choose PTI for This Application

PTI develops and validates HVLD and helium recipes independently for cartridge programs, including multi-analyst, multi-day reproducibility testing, so a client can choose either method on its own merits or use both in combination with full visibility into where each one's sensitivity is strongest.