Oxygen Ingress Measurement

Non-invasive, non-destructive & real conditions: Determine the shelf-life of your product

Oxygen Ingress Measurement
  • Determination of oxygen ingress in PET bottles
  • Determination of scavenger capacity
  • Determination of oxygen permeation through closures


A new non-invasive and non-destructive fiber optic oxygen meter determines oxygen permeability of plastic bottles and containers. Trace oxygen concentrations inside the package are measured. Ideal for assurance, production and quality control, this system incorporates the latest state-of-the-art in chemical optical sensor technology. Permeation rates can be confirmed without piercing the package or bottle.
The sensing principle is based on a fluorescence quenching method enabling oxygen measurements in a non-destructive way. A trace oxygen sensor spot is placed inside the transparent bottle or package and a fiber optic cable is positioned on the outside. The luminescence lifetime of the oxygen-sensitive spot changes with the oxygen concentration and is therefore acting as the oxygen dependent parameter.

Features:

  • Non-invasive & non-destructive
  • Real-conditions & online monitoring
  • Shelf-life determination
  • Sensitivity down to 1 ppb dissolved oxygen
  • Easy & precise measurement

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Measurement Set-ups

Single-Channel Set-up for Subsequent Measurement

Illustration: Permeation Measurement in PET Bottle

The sensor spot can be glued into the PET bottle which then can be closed with a standard closure. For this direct coating, the bottles should be transparent but the measurement is even possible through slightly coloured (e. g. greenish or yellowish) or turbid bottles.



Measurement with an Oxygen-Sensitive Cap in Case of Non-Transparent Bottles

Illustration: Oxygen Ingress Measurement in Non-Transparent PET Bottles

To determine the oxygen ingress in dark brown or non-transparent PET bottles, a direct coating of the PET bottle wall with a sensor spot is not possible. To enable non-invasive oxygen ingress measurement also for deeply coloured and non-transparent containers PreSens has developed an oxygen-sensitive cap (OSC) which can be used as closure.



Multi-Channel Set-up for Simultaneous Measurements

Illustration: Multi-Channel Set-Up for Oxygen Ingress Measurement

Transmitters for 4 and 10 oxygen sensors are offered. With this multi-channel set-up it is possible to monitor simultaneously up to 10 bottles.




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Results

Graph: Oxygen Ingress in Externally Coated PET Bottle
Bottle Type 1: External Coated PET Bottles

The oxygen ingress into an external coated (blue line) and the respective reference PET bottle without coating (red line) are shown over a period of more than 25 days. In the first 48 hours the increase of the oxygen concentration in non-coated bottles and bottles with the external coating is non-linear due to the additional migration of oxygen out of the PET bottle wall. The external barrier coating reduces the rate of permeation, resulting in a significantly decreased slope compared to the slope observed for non-coated PET bottles.



Graph: Oxygen Ingress in Bottles with External Coating and/or Different Amounts of O2 Scavenger
Bottle Type 2: PET Bottles with External Coating and / or Different Contents of Oxygen Scavenger

Oxygen ingress into differently treated PET bottles of the same type; (A) non-coated PET bottle with 2 % scavenger, (B) external coated PET bottle with no scavenger, (C) external coated PET bottle with 1 % scavenger, (D) external coated PET bottle with 0.5 % scavenger. The combination systems (C) and (D) hold oxygen ingress to less than 1 ppm over six months, which could not be accomplished with the active (scavenger (A)) or passive barrier (external coating (B)) alone.



Graph: Oxygen Ingress in Internally Coated PET Bottle
Bottle Type 3: Internal Coated PET Bottles

The inner coating provides an efficient barrier to oxygen (red line), and prevents oxygen desorption from the PET bottle wall into the product during the first few days of storage contrary to bottles coated externally.
In this case a thin layer of amorphous carbon, typically 100 to 200 nm thick, is applied  to the inner surface of the bottle. This is deposited from high-energy plasma of acetylene gas within a high vacuum environment.



Graph: Oxygen Ingress in Multilayer Bottles with Scavenger
Bottle Type 4: Multilayer Bottles Containing Oxygen Scavenger

Most common multilayer structures combine two layers of PET and a middle layer of Nylon MXD6 (metaxylylene diamine nylon) in three layer structures. The high barrier material is present in separate layers which are made by simultaneous or sequential co-injection (blue line). The combination of a multilayer structure adding an active barrier within the middle layer decreases oxygen ingress significantly, which could not be accomplished with a multilayer structure without an active barrier (red line).




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Technical Data

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