ASTM F2714-08

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Designation: F2714 − 08
StandardTest Method for
Oxygen Headspace Analysis of Packages Using Fluorescent
Decay
This standard is issued under the fixed designation F2714; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2.4 The fluorescent response from the dot is monitored and
the decay rate determined.
1.1 This test method covers a procedure for determination
of the oxygen concentration in the headspace within a sealed
2.5 The internal oxygen content of the package is deter-
package without opening or compromising the integrity of the
mined by comparing the measured decay rate to the decay rate
package.
observed with known oxygen concentrations.
1.2 This test method requires that chemically coated com-
3. Significance and Use
ponents be placed on the inside surface of the package before
closing.
3.1 The oxygen content of a package’s headspace is an
important determinant of the packaging protection afforded by
1.3 The package must be either transparent, translucent, or a
barrier materials. The package under test is typically MAP
transparent window must be affixed to the package surface
(modified atmosphere packaging) packaged.
without affecting the package’s integrity.
3.2 Oxygen content is a key contributor to off-flavors and
1.4 As this test method determines the oxygen headspace
spoilage of various products, such as chemicals, food and
over time, the oxygen permeability can easily be calculated as
pharmaceuticals.
ingress per unit time as long as the volume of the container is
known.
3.3 The method determines the oxygen in a closed package
headspace. This ability has application in:
1.5 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this 3.3.1 Package Permeability Studies—The change of head-
standard. space composition over a known length of time allows the
calculation of permeation. Since the headspace oxygen is
1.6 This standard does not purport to address all of the
measured as a percentage, the volume of the container’s
safety concerns, if any, associated with its use. It is the
headspace must be known to allow conversion into a quantity
responsibility of the user of this standard to establish appro-
such as millilitres (ml) of oxygen. The use of this approach to
priate safety and health practices and determine the applica-
measure permeation generally applies to empty package sys-
bility of regulatory limitations prior to use.
tems only as oxygen uptake or outgassing of contained
products could affect results.
2. Summary of Test Method
3.3.2 Leak Detection—If the headspace contains more oxy-
2.1 Chemically coated components (dots) are affixed to the
gen than expected or is increasing faster than expected, a leak
inside surface of the package to be tested.
can be suspected. A wide variety of techniques can be
2.2 The package is gas flushed to a reduced level of oxygen
employed to verify that a leak is present and to identify its
either manually or by subjecting the package to a filling
location. If necessary or of interest, a leak rate may be
operation.
calculated with known headspace volume and measured oxy-
gen concentration change over time.
2.3 Apulsing light source is directed through the package at
the chemically treated dot (the package must be transparent, 3.3.3 Effıcacy of the MAP Packaging Process—If the head-
spaceoxygenconcentrationisfoundtobehigherthanexpected
translucent or contain a window through which the light can
pass). soon after packaging, the gas flushing process may not be
working as well as expected. Various techniques can evaluate
whether the MAP system is functioning properly.
This test method is under the jurisdiction ofASTM Committee F02 on Flexible
3.3.4 Storage Studies—As the method is non-destructive,
Barrier Packaging and is the direct responsibility of Subcommittee F02.40 on
the headspace can be monitored over time on individual
Package Integrity Test Methods.
samples to insure that results of storage studies such as shelf
Current edition approved Aug. 1, 2008. Published August 2008. DOI: 10.1520/
F2714-08. life testing are correctly interpreted.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2714 − 08
4. Discussion lifetime proportional to the oxygen partial pressure. The
fluorescence lifetime will decrease from 5 µs in an oxygen free
4.1 Oxygen sensing based on fluorescence is well estab-
environment (for example, nitrogen) to 1 µs in ambient air (see
lished. The typical indicators used are ruthenium complexes
Fig. 1). The most important aspect of using quenching for
and porphyrins both of which are compatible with light
oxygen detection is that neither the oxygen nor the sensor is
emitting diodes (LEDs). In one oxygen sensitive coating, tris
consumed during a measurement.
(4,7 biphenyl 1,10 phenanthroline) ruthenium chloride is used
duetoitsstability,longlifetime,andstrongabsorptionbetween
5. Interferences
400 nm and 500 nm in the blue region of the spectrum. The
absorption peak is compatible with high brightness blue LEDs
5.1 The presence of certain interfering substances in the
or blue semiconductor lasers. The emission peak is at 600 nm
headspace may, in theory, give rise to incorrect readings.
in the red region of the spectrum and is detected by a
Normal headspaces in empty or filled packages have not been
photomultiplier tube or a photo detector to offer the flexibility
found to be problematic. Relative humidity in that headspace
ofalargedynamicrangeandfastresponsetime.Theruthenium
also has shown to not cause interferences.
complex is immobilized in a highly chemically resistant
5.2 The temperature of the package, when tested, needs to
substrate.
be measured.
4.2 The principle of fluorescence quenching is based on the
5.3 It is recommended that calibration, described below, of
excitedstatecharacteristicsofaspecificdye.Dynamicquench-
the chemically treated dots be conducted on packages contain-
ing is the transfer of energy from a fluorescent dye in its
ing known oxygen concentrations as close to the level to be
excited state to oxygen in the surrounding medium.The energy
experienced in actual tests. If the calibration is carried out at
consumed by oxygen will be dissipated as heat after a short
levels far different than actual levels, the results may shown
time and the whole process can repeat itself indefinitely
lessprecisionthanpredictedintheprecisionandbiasstatement
without consuming oxygen.
below.
4.3 The ruthenium complex is excited with blue light from
an LED. Short pulses of blue light from the LED are absorbed
6. Apparatus
by the ruthenium complex. In the absence of oxygen, the
6.1 Chemically Treated Components (aka “dots”) —Coated
ruthenium complex will emit light in the red region of the
substrates of glass or flexible clear plastic have been found to
spectrum. The average time between the absorption of the blue
be satisfactory. A fluorescent dye polymer is deposited on one
photon and the release of the red photon is called the
side of the substrate.
fluorescence lifetime. The fluorescence lifetime of the ruthe-
nium complex is about 5 µs. However, if oxygen is present, the 6.2 Adhesive is used to attach the non-coated side of the dot
to the inside of the package. Silicone rubber adhesive has been
fluorescence is quenched. This occurs when oxygen molecules
collide with the excited ruthenium molecules. During the shown to be satisfactory. Other adhesives and double-sided
tape will work as well. No adhesive has yet been identified
collision, energy is transferred from the ruthenium to the
oxygen, preventing emission. This process is called dynamic which interferes with the fluorescence of the dye as long as the
quenching, and it results in a decrease in the fluorescence adhesive is sufficiently translucent.
NOTE 1—The fluorescent lifetime lies between 1 µs and 5 µs.
FIG. 1 Relative Fluorescence Signals (I/I ) after Illumination of a Short Blue Pulse, Quenched by Different Oxygen Pressures in Air of
20°C
F2714 − 08
6.3 Light Source producing sufficient energy in the appro- not change for 1 min and the package or fixture has received at
priate wavelength to activate the fluorescent dye. The light least 20 times the headspace volume in
...