Glass & Plastic Vials: High-Voltage Leak Detection (HVLD)

Overview

HVLD is an electrical-sensing CCI method rather than a pressure-based one. A high-voltage electrode sweeps the outside of the rotating, liquid-filled vial while a return electrode measures current; a breach that creates a conductive path from the electrode, through a defect, to the grounded liquid produces a detectable current spike. Because the technique senses through the liquid itself, the container should hold a conductive fill — the actual product or a representative placebo — and cannot be tested empty.

This makes HVLD especially valuable in two situations where vacuum decay struggles. Viscous, protein-containing, or otherwise "sticky" formulations can mechanically clog a micro-defect and mask it from a pressure-based test, but HVLD's electrical path only requires ionic conductivity, not open gas flow. Container geometries with dimensional variability — molded plastic vials in particular, whose wall thickness and shape vary from unit to unit — are addressed with a multi-zone HVLD setup.

Sample & Container Type

• Liquid-filled glass and plastic vials
• Thin-wall tubular glass and thicker-wall molded plastic formats
• Sealed with an elastomeric stopper and crimp or snap closure
• Tested at the as-manufactured fill volume, product-containing

Product Class & Rheology

• Filled aqueous drug products — small-molecule solutions and biologic (protein-based) solutions
• Requires the product itself or a representative placebo to be present, since the method senses through the liquid
• Viscous and protein-containing formulations that can mask a defect from pressure-based methods

General Test Method

Development follows the same staged progression as PTI's other CCI work — initial recipe creation, method development, and formal validation — using populations of intact negative controls alongside vials carrying certified micro-defects placed at defined body, shoulder, and neck locations. Because HVLD sensitivity is affected by fill conductivity, fill level, and container wall geometry, each combination is characterized independently rather than assumed to be portable between formats or fill types.

Typical Findings & Sensitivity

Typical outcomes show reliable detection at or below 10 microns for well-conditioned liquid fills, with several programs demonstrating consistent separation down to 5 microns or finer once the recipe and zoning are optimized. Thicker-wall plastic vials and very low-fill-volume containers generally require more careful zoning and can show somewhat reduced sensitivity at the extremes of the container (neck and base). In head-to-head evaluations against vacuum decay on the same difficult product, HVLD has consistently shown equal or superior sensitivity for viscous or protein-based fills, which is why it is frequently the recommended default for prefilled and liquid-filled biologic vial products.

Frequently Asked Questions

1. Why use HVLD instead of vacuum decay for a vial program?

HVLD is the stronger choice whenever the fill is viscous, protein-based, or otherwise likely to mechanically mask a defect from a pressure-based test, or when the container itself (such as molded plastic) has dimensional variability that a pressure test handles less consistently.

2. Does HVLD require the drug product to be present?

Yes. HVLD senses through the liquid fill, so testing requires the actual product or a representative, similarly conductive placebo rather than an empty container.

3. Can HVLD test plastic vials with wall-thickness variation?

Yes, using a multi-zone setup in which voltage and sensitivity are tuned independently for different vertical zones of the vial — heel, body, shoulder, and neck — to compensate for the electrical noise that thickness variation introduces.

4. What sensitivity does HVLD typically achieve on vials?

Well-conditioned liquid fills typically show reliable detection at or below 10 microns, with several programs achieving consistent separation down to 5 microns once the recipe and zoning are optimized.

5. Is HVLD better than vacuum decay for viscous or protein formulations?

In PTI's head-to-head comparisons, HVLD has consistently shown equal or superior sensitivity to vacuum decay for viscous and protein-based fills, which is why it is often the recommended starting point for biologic vial programs.

Why Clients Choose PTI for This Application

PTI develops and validates an HVLD recipe against the client's actual fill and container rather than reusing a generic voltage setting, and it reports zone-specific sensitivity transparently rather than a single blended number. For biologic and viscous vial products where a pressure-based method is a known risk, this gives a program sponsor a defensible, product-specific sensitivity claim before committing to production-scale testing.