Designation: G121–18

Standard Practice for Preparation of

Contaminated Test Coupons for the
Evaluation of Cleaning Agents 1
This standard is issued under the fixed designation G121; 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 (ε)
indicates an editorial change since the last revision or reapproval.

IN THIS STANDARD:
Section 1 Scope
Section 2 Referenced Documents
Section 3 Terminology
Section 4 Summary of Practice
Section 5 Signi�cance and Use
Section 6 Apparatus
Section 7 Reagents
Section 8 Procedure
Section 9 Calculation
Section 10 Report
Section 11 Keywords
Footnotes

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1.1 is practice describes the procedure for the preparation of single- and double-sided contaminated
test coupons for the evaluation of cleaning agents. It is applicable for the evaluation of cleaning agents
proposed for the cleaning of oxygen equipment, pharmaceutical manufacturing equipment, and medical
devices (see Test Method G122 and Guide G127). It also is applicable to other systems where
contamination is a concern.

1.2 Several classes of contaminants/residues most likely to be found in oxygen equipment, pharmaceutical
manufacturing equipment, and medical devices are identi�ed. However, if the user of this practice has
identi�ed contaminants not included in these classes, such identi�ed contaminants may be substituted
 for the preparation of the test coupons if appropriate for this test method.

1.3 Solvent and cleaning agent compatibility with nonmetallic substrates should be veri�ed prior to the
preparation of the test coupons. Typical nonmetallic materials utilized in oxygen systems are contained in
Guide G63.

1.4 is practice may involve hazardous materials, operations, and equipment. is practice does not
purport to address all of the safety concerns associated with its use. It is the responsibility of whomever uses
this practice to consult and establish appropriate safety, health, and environmental practices and determine
the applicability of regulatory limitations prior to use.

1.5 is international standard was developed in accordance with internationally recognized principles on
standardization established in the Decision on Principles for the Development of International Standards,
Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT)
Committee.

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2.1 ASTM Standards: 2

D1193 Speci�cation for Reagent Water

E1235 Test Method for Gravimetric Determination of Nonvolatile Residue (NVR) in Environmentally
Controlled Areas for Spacecra

E3106 Guide for Science-Based and Risk-Based Cleaning Process Development and Validation

F303 Practices for Sampling for Particles in Aerospace Fluids and Components

F312 Test Methods for Microscopical Sizing and Counting Particles from Aerospace Fluids on
Membrane Filters

F324 Test Method for Nonvolatile Residue of Volatile Cleaning Solvents Using the Solvent Purity Meter
(Withdrawn 1987) 3

F331 Test Method for Nonvolatile Residue of Solvent Extract from Aerospace Components (Using Flash
Evaporator)

F3127 Guide for Validating Cleaning Processes Used During the Manufacture of Medical Devices

G63 Guide for Evaluating Nonmetallic Materials for Oxygen Service

G94 Guide for Evaluating Metals for Oxygen Service

G122 Test Method for Evaluating the Effectiveness of Cleaning Agents

G127 Guide for the Selection of Cleaning Agents for Oxygen-Enriched Systems

2.2 ANSI Standard: 4

B46.1 Surface Texture (Surface Roughness, Waviness, and Lay)

3 | TERMINOLOGY PREVIOUS NEXT | TOP BOTTOM

3.1 Definitions:

3.1.1 blank, n—the contamination level of the �uid when the test coupon is omitted.

3.1.1.1 Discussion—Sometimes referred to as “background” level.

3.1.2 cleaning agent, n—an agent used to support the removal of contaminant from equipment surfaces
or other critical objects (such as a medical device).

3.1.3 contaminant (contamination), n—unwanted molecular, non-volatile residue (NVR), and/or

particulate matter that could adversely affect or degrade the operation, life, or reliability of the systems
or components upon which they reside.

3.1.3.1 Discussion—e contaminant could be a drug substance, an intermediate, a formulated product, a

lubricant, a machining oil, a solvent, a cleaning agent, etc. e contaminant may migrate to other
surfaces or users may become exposed to the contaminant during the use of equipment.

3.1.4 contaminate, v—a process of applying contaminant (non-volatile residue (NVR) and/or particulate
matter).

3.1.5 control coupon (witness coupon), n—a coupon made from the same material as the test coupons,
but in this test method is not coated with the contaminant.

3.1.6 dirty hold time (DHT), n—the maximum time interval between equipment use and cleaning.

3.1.7 molecular contaminant (non-particulate contamination), n—molecular contaminants that may exist
in a gaseous, liquid, or solid state and may be uniformly or non-uniformly distributed.

3.1.7.1 Discussion—Molecular contaminants may be found as a solution, an emulsion, or in the form of

droplets. Molecular contaminants account for most of what constitutes NVR.

3.1.8 nonvolatile residue (NVR), n—a molecular and particulate matter remaining following the �ltration
and controlled evaporation of a solvent containing contaminants.

3.1.9 particle (particulate contaminant), n—a general term used to describe a �nely divided solid of
organic or inorganic matter with observable length, width, and thickness.

3.1.9.1 Discussion—Particulates are usually reported as the amount of contaminant by the population of a
speci�c micrometer size, usually de�ned by its greatest dimension. See methods described in Test
Methods F312, Practices F303, or ARP 598 for particle size and population determination.

3.1.10 surface roughness, Ra, n—the arithmetic average deviation of the surface pro�le from the
centerline, normally reported in micrometres.

3.1.11 test coupon, n—representative surface that is typically a rectangular piece of a material of
construction on which a known amount of a compound is deposited to simulate a process residue.

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4.1 e contaminant under study is applied to either one side or both sides of precleaned test coupons in a
de�ned area. e amount of contaminant on the test coupons is determined by weighing the test coupons
 before and aer application. e amount of contaminant applied should be controlled and the variation
in weight between test coupons minimized. Test coupons should be tested in a manner that simulates the
actual cleaning conditions for the product, equipment, or system. Coupons may be tested immediately to
simulate actual cleaning conditions or dried under speci�ed conditions (for example, ambient overnight,
8 h at 104 °C, etc.) prior to testing (for example, for Dirty Hold Time studies). Nonmetallic material test
coupons used as inserts, seats, seals, gaskets, etc. may also be prepared by this procedure and are
evaluated under actual cleaning conditions.

4.2 ree methods of test coupon preparation are used:

Method A: NVR sample, single side,

Method B: NVR sample, double side, and

Method C: NVR and particulate sample.

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5.1 is practice will be suitable to direct the preparation of test coupons with a known amount of
contaminant on the surface. A standard test coupon is described and a list of contaminants that have
typically been found in oxygen-enriched systems and components is provided.

5.2 ese test coupons shall be used in the evaluation of cleaning agents for oxygen-enriched systems and
components. is will permit direct comparison within and between test facilities.

5.3 Materials used in other �uid handling systems such as nitrogen, helium, hydrogen, gasoline, etc. may
also be prepared for evaluation by this practice.

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6.1 Test Coupon—Panels of the same material of construction and �nish as the equipment, product, or
system to be cleaned. Other alloys that may be used if the speci�c alloy is unknown are included in Guide
G94. Test coupons should be numbered and in a manner that prevents removal during testing. A
speci�ed area of the test coupon may be designated as the test area where the test material is applied. Test
coupons may be of different test area dimensions (for example, 5 cm x 5 cm, 10 cm x 10 cm) depending
on the test procedure they are used in. An example test coupon con�guration is shown in Fig. 1.

FIG. 1 Example Test Coupon

 NOTE 1: The surface finish of the test coupon should be the same as the part to be cleaned.

6.2 Balance—Range to a minimum of 50 g with an 0.1-mg accuracy capable of weighing to ±0.1 mg.

6.3 Convection Oven—Capable of maintaining 50 °C ± 5 °C.

6.4 Spray Applicator—Capable of applying an even coat of contaminant; that is, an artist's airbrush,
perfume atomizer, or a spray device such as that used with window or tile cleaners has been found to
apply an even coating of the contaminant in a controlled manner.

6.5 Other standard equipment such as a vacuum �ltration system, solvent resistant �lters, gloves,
laboratory glassware, syringes, pipettes, desiccator, laboratory tongs, tweezers, and wire.

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7.1 Contaminant Materials—General classes of materials that have typically been found in oxygen-enriched
systems and components as a result of the manufacturing, assembly, fabrication, and construction
processes include:

silicone oils and greases,

�uorinated aerospace �uids and greases,

petroleum based oils,

ester based oils,

phosphate esters,

waxes,

chlorotri�uoroethylene based oils,

 inks,

cutting oils, and

dye penetrants.

7.1.1 Solvent-reagent-grade used to prepare standard solutions of contaminants which may include the
following: 2-propanol, 2-butanone, hexane, Type II reagent water, or better, in accordance with
Speci�cation D1193, and per�uorinated carbon �uids. (Warning—Solvents such as 2-propanol hexane
and 2-butanone are highly �ammable. Appropriate safe handling procedures should be used.)

7.2 Contaminant materials—Classes of materials that are typically evaluated in health care industry
products, equipment, and processes include but are not limited to the following:

Active Pharmaceutical Ingredients,

Intermediates of Active Pharmaceutical Ingredients,

Finished Pharmaceutical Products,

Biological products (proteins, fermentation broth, etc.),

Cosmetic products,

Degradants,

Excipients,

Etc.

7.2.1 Solvent-reagent-grade used to prepare standard solutions of contaminants may include USP
Puri�ed Water and Water for Injection, and solvents such as Methanol, Ethanol, Isopropyl Alcohol, etc.

7.3 Desiccant—for example, silica gel.

7.4 Particulate Contaminant—�ne (0- to 80-μm), or coarse (0- to 200-μm) powders/particles. 5

8 | PROCEDURE PREVIOUS NEXT | TOP BOTTOM

8.1 Test Coupon Preparation:

8.1.1 Test coupons should be prepared from the same Material of Construction (MOC) and with the
same material grade (for example, SS 316L/#4) that will be used in the equipment, product, or system
under study. e test coupons shall be numbered and precleaned prior to use and the number recorded.
If surface roughness is a variable in the application, selecting the roughest surface �nish for the test
coupons is advisable to represent worst-case conditions. e surface roughness, Ra, of representative
test coupons of each alloy can be evaluated per ANSI B46.1 and recorded. e surface area to be
contaminated (S) of each of the test coupons should be predetermined (for example, 5 cm x 5 cm, 5 cm
x 10 cm, etc.). e test coupons may also have an inscribed test area. If desired, attach a handling wire
through the hole at the top of each of the test coupons. New test coupons should be cleaned prior to use
with a similar procedure to that used for the equipment MOC under study (for example, stainless steel
test coupons should be passivated prior to use). Test coupons should be cleaned aer use with a de�ned
procedure that restores the test coupons' surfaces to their original state (for example, original starting
 weight or less). Prepare one control coupon with the test coupons to be contaminated for each cleaning
agent to be evaluated if a control will be used. e test coupons shall be dried and stored until needed to
avoid possible contamination. Test coupons used for a dirty hold time study should be stored in a
manner similar to the equipment under study.

8.1.1.1 Test coupons should be examined prior to use to determine if they are acceptable for use against a
de�ned standard for the test coupons (for example, change in surface roughness, Ra, maximum
number of scratches, surface imperfections that interfere with evaluation, staining, or lack of visual
cleanliness).

8.1.2 For testing for Oxygen Service, verify that the test coupons have an NVR of 10 mg/sq m (1 mg/sq
) or less using Test Methods E1235, F324, or F331 and have no particles larger than 300 μm when
evaluated using Test Methods F312. Determine the blank NVR values and particle counts on the
solvents used to prepare the contaminating solutions as recommended in Practices F303. ese values
must be taken into account when preparing the standard contaminating solutions, especially when very
dilute solutions are desired. Rinse each test coupon being prepared for contamination with the solvent
to be used in the contaminant solution. Allow the test coupons to dry overnight or in an oven at 40 to
50 °C for 1 h, cool to room temperature in a desiccator, and weigh. Reweigh the test coupon at intervals,
1 h typically, until a constant weight, ±0.1 mg, is achieved. Weigh, record the weight (W1) in grams to
the nearest 0.1 mg, and store in a desiccator until needed.

NOTE 2: It is recommended that test coupons be prepared in lots of ten or more to ensure the necessary sensitivity for the
verification.

8.1.3 Aer cleaning, the test coupons should be handled only with laboratory tongs or tweezers by the
handling wire or a hook on the test coupon itself.

8.2 Method A, Nonvolatile Residue (NVR) Sample, Single Side:

8.2.1 Prepare a standard solution containing the desired contaminant, in a suitable solvent for that
contaminant. As an alternative, a mixture of as many contaminants as desired may be prepared in a
suitable solvent. e concentration of the solution, typically between 1 and 100 mg/mL, should be
adjusted to re�ect the worst expected contamination level in the system to be cleaned. In some cases
(for example, oils, dye penetrants, or inks) it may not be necessary to use a solvent in the preparation of
the test coupons to achieve the desired level of contamination.

8.2.2 Place the test coupon(s), number side down, on a horizontal surface and carefully apply the
solution containing the contaminant to the upper surface of the test coupon using a pipette, syringe,
brush, or spray applicator. Record the number of the test coupon and the surface area (S) in square
centimeters of each test coupon that was coated.

8.2.3 Allow the contaminant to dry overnight or in an oven at 40 to 50 °C for 1 h, cool to room
temperature in a desiccator, remove from the desiccator, and weigh. Reweigh the test coupon at
intervals while storing the test coupons in a desiccator between weighings, 4 h typically, until a constant
weight is achieved. Record the �nal weight (W2) in grams to the nearest 0.1 mg. It may be necessary to
make additional applications to achieve the desired contamination level. (Warning—Do not place test
coupons directly in the oven aer application of the solution containing the contaminant. A �re may
result if the solvent is �ammable; or rapid evaporation of the solvent may cause spattering of the
contaminant, thereby reducing the amount of contaminant on the test coupon. It is recommended that
the test coupons be air dried until no traces of a liquid phase are visible.)

8.2.4 Test coupons shall be used immediately aer �nal weighing.

8.3 Method B, NVR Sample, Double Side:

8.3.1 Prepare a standard solution containing the desired contaminant in a suitable solvent for that
contaminant. As an alternative, a mixture of as many contaminants as desired may be prepared in a
suitable solvent. e concentration of the solution, typically between 1 and 100 mg/mL, should be
adjusted to re�ect the worst expected contamination level in the system to be cleaned. In some cases
(for example, oils, dye penetrants, or inks) it may not be necessary to use a solvent in the preparation of
the test coupons to achieve the desired level of contamination.

8.3.2 Carefully dip the test coupon into the contaminant solution until it is completely immersed.
Slowly withdraw the test coupon from the contaminant solution. Other methods of application include
brushing or spraying. Record the number of the test coupon and the surface area (S) of each test coupon
that was coated. Hang the test coupon by the handling wire and allow the contaminant to dry overnight
or in an oven at 40 to 50 °C for 1 h. Cool to room temperature in a desiccator, and weigh. Reweigh the
test coupon at intervals, 4 h typically, until a constant weight is achieved. Record the �nal weight (W2).
If there is risk of losing the NVR contaminant from interaction with other surfaces, the test coupon
should remain hanging using the hanging wire during downtime and during the mass measurement.
(Warning—Do not place test coupons directly in the oven aer application of the solution containing
the contaminant. A �re may result if the solvent is �ammable; or rapid evaporation of the solvent may
cause spattering of the contaminant, thereby reducing the amount of contaminant on the test coupon. It
is recommended that the test coupons be air dried until no traces of a liquid phase are visible.)

8.3.3 Test coupons shall be used immediately aer the �nal weighing.

8.4 Method C, NVR and Particulate Sample:

8.4.1 Prepare a standard solution containing the desired NVR contaminant, in a suitable solvent for that
contaminant. As an alternative, a mixture of as many NVR contaminants as desired may be prepared in
a suitable solvent. e NVR contaminant concentration of the solution, typically between 1 and 100
mg/mL, should be adjusted to re�ect the worst expected NVR contamination level in the system to be
cleaned. Add 10, 20, or 30 mg of particulate contaminant to each 100 mL of solution to provide a light,
medium, or heavy particulate level, respectively. In some cases, that is, oils, dye penetrants, or inks, it
may not be necessary to use a solvent in the preparation of the test coupons to achieve the desired level
of contamination.

8.4.2 Place the test coupon(s), number side down, on a horizontal surface and carefully apply the
solution containing the contaminant, which is agitated or stirred to keep the particulate suspended, to
the top upper surface of the test coupon using a pipette, syringe, brush, or spray applicator. Hang the
test coupon by the handling wire and allow the contaminant to dry overnight or in an oven at 40 to 50
°C for 1 h. Cool to room temperature in a desiccator, and weigh. Reweigh the test coupon at intervals, 4
h typically, until a constant weight is achieved. Record the �nal weight (W2). (Warning—Do not place
test coupons directly in the oven aer application of the solution containing the contaminant. A �re
may result if the solvent is �ammable; or rapid evaporation of the solvent may cause spattering of the
contaminant, thereby reducing the amount of contaminant on the test coupon. It is recommended that
the test coupons be air dried until no traces of a liquid phase are visible.)

8.4.3 Test coupons shall be used immediately aer �nal weighing.

8.5 Method D, Pharmaceutical, Biologics, and Cosmetic Products, Single Side:

8.5.1 Place the test coupon(s) on a horizontal surface and record the number of the test coupon and the
surface area (S) in square centimeters of each test coupon to be coated.
 8.5.2 Carefully and quickly apply the product under test to the test area of the test coupon using an
appropriate applicator. Product should be applied in manner that simulates the way residues occur in
actual use (for example, if residues build up over time, then coatings may be applied over a similar time
period to simulate this). Application of the coating and the subsequent testing should provide a small
scale simulation of the cleaning process under study. (See Guides E3106 and F3127.)

8.5.3 Weigh the test coupon in such a manner as to prevent weight losses from evaporation and record
the weight.

8.5.4 It is a good practice to take photographs of the coated test coupons prior to and aer testing for
reference.

8.5.5 Test coupons shall be tested immediately aer weighing to simulate "as is" cleaning conditions. In
the case of semi-solid materials, or contaminants containing water or volative substances, the dry
weight of the contaminant should be determined at the same time and used in the calculations to
prevent the loss on drying of the test coupon to appear as contaminant being removed by the cleaning
agent. e weight of contaminant should be adjusted based on this dry weight.

8.5.6 For studies on the effect of the contaminant drying on the MOC surface over a period of time
before cleaning (for example, dirty hold time studies for pharmaceuticals) the contaminant should be
allowed to dry onto the test coupon for a prescribed period of time (for example, one week) before
testing. e test coupons shall be tested aer the holding period.

9 | CALCULATION PREVIOUS NEXT | TOP BOTTOM

9.1 Calculate the amount of contaminant on the test coupon in mg/cm2 using:

where:

C = amount of contaminant, mg/cm2;

W1 = weight of the clean test coupon, g;
W2 = weight of the contaminated test coupon, g (adjusted for dry weight if necessary); and
S = contaminated surface area of the test coupon, cm2.

10 | REPORT PREVIOUS NEXT | TOP BOTTOM

10.1 e report shall include the following:

10.1.1 e number of the test coupon,

10.1.2 Identi�cation of alloy,

10.1.2.1 Name of Uni�ed Numbering System (UNS) alloy designation,

10.1.2.2 Heat,

10.1.2.3 Hardness,

10.1.2.4 Surface roughness (Ra),

 10.1.3 Identi�cation of the solvent used,

10.1.4 Identi�cation of the contaminant,

10.1.5 Method of application of the contaminant,

10.1.6 Method of drying the test coupon,

10.1.7 Weight of the uncontaminated test coupon (W1),

10.1.8 Weight of the contaminated test coupon (W2),

10.1.9 e amount of contaminant (C) on the test coupon in mg/cm2, and

10.1.10 Photographs of the pre and post contaminated test coupons (optional).

11 | KEYWORDS PREVIOUS NEXT | TOP BOTTOM

11.1 cleaning agents; contaminant; contamination; non-volatile residue; oxygen systems; standard test
coupon

FOOTNOTES PREVIOUS NEXT | TOP BOTTOM

(1) This practice is under the jurisdiction of ASTM Committee G04 on Compatibility and Sensitivity of Materials in Oxygen Enriched
Atmospheres and is the direct responsibility of Subcommittee G04.02 on Recommended Practices.

Current edition approved Dec. 1, 2018. Published January 2019. Originally approved in 1993. Last previous edition approved in
2015 as G121 – 98 (2015)ɛ1. DOI: 10.1520/G0121-18.

(2) For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at
service@astm.org. For Annual Book of ASTM Standards volume information, refer to the standard's Document Summary page on
the ASTM website.

(3) The last approved version of this historical standard is referenced on www.astm.org.

(4) Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.

(5) Available commercially.

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