Prefilled Syringes: High-Voltage Leak Detection (HVLD)

Overview

HVLD applied to prefilled syringes addresses the same two-seal-interface challenge as syringe vacuum decay, but through an electrical rather than pressure-based measurement principle. A conductive high-voltage probe scans the exterior of the rotating syringe while the system monitors for an increase in electrical current created when the applied voltage finds a conductive path through a package defect to the grounded liquid product.

HVLD is often considered when vacuum decay is not well suited to the product or package configuration. Vacuum decay can be challenged by formulations with high tackiness or large protein structures that may bridge or partially obstruct small defects. In these cases, HVLD can provide an effective alternative. Its performance, however, can be limited by thicker plastic container walls, low fill volumes, and greater headspace.

Sensitivity is also not uniform across a prefilled syringe. Defects in the plunger-stopper seal region are generally detected with high reliability, while defects at the needle-shield or rigid-needle-system interface can be significantly more difficult to detect. In PTI's experience, detection at the needle-end interface may be only approximately one-half to two-thirds as effective as detection of comparable defects in the stopper region on the same syringe design.

Sample & Container Type

• Liquid-filled glass prefilled syringes, typically 1–5 mL
• Rubber plunger/stopper at the fill end; needle shield or rigid needle system at the delivery end
• Tested rotating, under a high-voltage probe sweep

Product Class & Rheology

• Aqueous and viscous parenteral formulations, including biologic (protein) solutions
• Filled to nominal delivery volume; the fill liquid itself carries the electrical signal
• Requires a product-representative, liquid-filled unit rather than an empty syringe

General Test Method

Development establishes zone-specific voltage and sensitivity settings tuned to the syringe's barrel diameter and glass thickness, then challenges the recipe with populations of intact syringes and syringes carrying certified micro-defects at defined barrel, shoulder, and closure locations, across multiple fill volumes and orientations where relevant.

Typical Findings & Sensitivity

Defects clearly located in the plunger/stopper seal region are detected at a high rate, often approaching full separation from the intact population. Defects at the needle-shield or rigid-needle-system interface are detected far less consistently — a genuine, physically grounded limitation, since a mechanically imperfect shield seal does not always create a true liquid-conductive leak path, rather than an instrument shortcoming. HVLD is usually the strongest available single-technology option for a syringe's primary barrel seal, especially for anything beyond a simple aqueous fill.

Frequently Asked Questions

1. Is HVLD more sensitive than vacuum decay for prefilled syringes?

In head-to-head comparisons, HVLD has consistently shown a meaningfully better performance for tacky or proteinaceous applications.

2. Does HVLD reliably catch needle-shield leaks on a syringe?

Less reliably than plunger-stopper leaks — often only at roughly half to two-thirds the detection rate seen at the stopper region, since a mechanical imperfection at the shield interface doesn't always create a true conductive leak path.

3. What is the typical detection range for HVLD on syringes?

Detection performance is reported as a rate against certified defect populations rather than a single micron number, but the plunger/stopper region typically approaches full separation from the intact population.

4. Does HVLD work well with viscous or biologic fills?

Yes — this is one of HVLD's key strengths over vacuum decay for syringes, since the electrical sensing path only needs ionic conductivity rather than an open gas-flow path that a viscous fill can obstruct.

5. When should HVLD be paired with a second method on syringes?

When full closure-system coverage — including the shield or cap interface — is required with high confidence, PTI typically recommends pairing HVLD with a secondary confirmatory method or dedicated interface-focused development work.

Why Clients Choose PTI for This Application

PTI's syringe HVLD programs report plunger-stopper and shield-region sensitivity separately and transparently rather than overstating whole-container coverage. For most new prefilled syringe CCI programs, this makes HVLD PTI's most frequently recommended starting point, with a clear, evidence-based path to adding complementary coverage where the data shows it is needed.