Photo credit: NOAA Marine Debris Program 

Laboratory Methods for the Analysis of Microplastics in

the Marine Environment: 

Recommendations for quantifying synthetic particles in

waters and sediments 

NOAA Marine Debris Program 

National Oceanic and Atmospheric Administration 

U.S. Department of Commerce 

Technical Memorandum NOS-OR&R-48 

July 2015 

Mention of trade names or commercial products does not constitute 

endorsement or recommendation for their use by the United States 

government. 
 

 

 

Laboratory Methods for the 

Analysis of Microplastics in 

the Marine Environment 

Recommendations for quantifying synthetic particles 

in waters and sediments 

Julie Masura1, Joel Baker1, Gregory Foster2, and Courtney Arthur3,4 

Carlie Herring, Technical Editor3,4 

1 Center for Urban Waters, University of Washington, Tacoma WA 

2 Department of Chemistry and Biochemistry, George Mason University, Fairfax VA 

3 I.M. Systems Group, Rockville MD 

4 National Oceanic and Atmospheric Administration, Marine Debris Division, Silver Spring MD 

The suggested citation for this document is: 

Masura, J., et al. 2015. Laboratory methods for the analysis of microplastics in the 

marine environment: recommendations for quantifying synthetic particles in waters 

and sediments. NOAA Technical Memorandum NOS-OR&R-48. 

For copies of this document, please contact: 

NOAA Marine Debris Division 

1305 East-West Highway 

Silver Spring, MD 20910 USA 
 

 

Acknowledgements 

The NOAA Marine Debris Program would like to acknowledge Sherry Lippiatt, Sarah Opfer 

Lowe, and Nir Barnea (NOAA National Ocean Service, Marine Debris Program) for reviewing 

this manual and providing helpful comments and Asma Mahdi for design and layout. Funding 

for this project was provided by the NOAA Marine Debris Program. 

This publication does not constitute an endorsement of any commercial product or intend to be 

an opinion beyond scientific or other results obtained by the National Oceanic and Atmospheric 

Administration. No reference shall be made to NOAA, or this publication furnished by NOAA, 

to any advertising or sales promotion which would indicate or imply that NOAA recommends or 

endorses any proprietary product mentioned herein, or which has as its purpose an interest to 

cause the advertised product to be used or purchased because of this publication. Although 

released by NOAA, the information in this paper does not reflect, represent, or form any part of 

the support of the policies of NOAA or the Department of Commerce. 

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Laboratory Methods for the Analysis of Microplastics 

Table of Contents 

Acknowledgements ...................................................................................................................................i
 

Abbreviations ..........................................................................................................................................iii
 

Units...........................................................................................................................................................iii
 

Microplastics Background .................................................................................................................... 1
 

Introduction to Methods Manual ........................................................................................................ 2
 

1.0 Methods for the Analysis of Microplastics in Water Samples ........................................ 3
 

1.1 Apparatus and Materials ................................................................................................................................. 7
 

1.2 Wet Sieving......................................................................................................................................................... 8
 

1.3 Transfer Sieved Solids..................................................................................................................................... 8
 

1.4 Determine the Mass of Total Solids............................................................................................................ 8
 

1.5 Wet Peroxide Oxidation (WPO)................................................................................................................... 9
 

1.6 Density Separation.......................................................................................................................................... 10
 

1.7 Microscope Exam............................................................................................................................................ 11
 

1.8 Gravimetric Analysis .....................................................................................................................................12
 

2.0 Methods for the Analysis of Microplastics in Beach Samples....................................... 13
 

2.1 Apparatus and Materials ...............................................................................................................................15
 

2.2 Beach Sediment Sample Preparation ........................................................................................................16
 

2.3 Density Separation..........................................................................................................................................16
 

2.4 Determine the Mass of Total Solids..........................................................................................................17
 

2.5 Wet Peroxide Oxidation (WPO).................................................................................................................18
 

2.6 Density Separation.......................................................................................................................................... 18
 

2.7 Microscope Exam............................................................................................................................................19
 

2.8 Gravimetric Analysis .....................................................................................................................................19
 

3.0 Methods for the Analysis of Microplastics in Bed Samples .......................................... 20
 

3.1 Apparatus and Materials ...............................................................................................................................22
 

3.2 Bed Sediment Sample Preparation ............................................................................................................23
 

3.3 Wet Sieving and Transfer of Sieved Solids ............................................................................................23
 

3.4 Determine the Mass of Total Solids (Sample Matrix).........................................................................23
 

3.5 Density Separation..........................................................................................................................................24
 

3.6 Determine the Mass of Total Solids (Microplastics and Natural Materials) ................................24
 

3.7 Wet Peroxide Oxidation (WPO).................................................................................................................24
 

3.8 Density Separation.......................................................................................................................................... 25
 

3.9 Microscope Exam............................................................................................................................................25
 

3.10 Gravimetric Analysis .....................................................................................................................................25
 

4.0 Cited References................................................................................................................ 26
 

5.0 Appendices ......................................................................................................................... 27
 

5.1 Appendix of Calculations ............................................................................................................................. 27
 

5.2 Appendix of Guidelines and Considerations ..........................................................................................29
 

Note: All photos are credited to the University of Washington, Tacoma (with the exception of 

the cover photo to which the photo credit is the NOAA Marine Debris Program). 

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Laboratory Methods for the Analysis of Microplastics 

Abbreviations
 

(aq) aqueous 

Fe(II) iron (II) 

NaCl sodium chloride (a salt) 

NOAA National Oceanic and Atmospheric Administration 

NOS National Ocean Service 

OR&R NOAA Office of Response and Restoration 

PVC polyvinylchloride 

WPO* wet peroxide oxidation 

40X magnification with light microscopy by 40 times 

Units 

C Celsius 

d density 

g gram 

h hour 

in inch 

M Molar 

mg milligram 

mL milliliter 

mm millimeter 

min minute 

*The Wet Peroxide Oxidation (WPO) process results in a highly reactive mixture. Please review 

your laboratory safety practices and policies before completing this analysis. In this manual, we 

have highlighted the WPO steps with a CAUTION note. 

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Laboratory Methods for the Analysis of Microplastics 

Microplastics Background 

Over the past decade, microplastic debris in both marine and freshwater systems has become an 

emerging issue. There is an increased interest to understand the impacts of microplastics on 

aquatic wildlife, as the impacts still remain poorly understood (Thompson et al. 2004, Browne et 

al. 2007). Microplastics were first noted in North America as spherules in plankton tows along 

the coast of New England in the 1970s (Carpenter et al. 1972). Since then, microplastics have 

been found in most large bodies of water (oceans, seas, lakes, and rivers). 

Microplastics are plastic particles smaller than 5.0 mm in size (Arthur et al. 2009). The lower 

bound (size) of the microplastics is not defined; however, it is common practice to use the mesh 

size (333μm or 0.33mm) of the neuston nets used to collect the samples (Arthur et al. 2009). 

There are two main ways microplastics are formed and enter a body of water: primary and 

secondary microplastics (Arthur et al. 2009). Primary microplastics consist of manufactured raw 

plastic material, such as virgin plastic pellets, scrubbers, and microbeads (Browne et al. 2007, 

Arthur et al. 2009) that enter the ocean via runoff from land (Andrady 2011). Secondary 

microplastic introductions occur when larger plastic items (meso- and macro- plastics) enter a 

beach or ocean and undergo mechanical, photo (oxidative) and/ or biological degradation 

(Thompson et al. 2004, Browne et al. 2007, Cooper and Corcoran 2010, Andrady 2011). This 

degradation breaks the larger pieces into progressively smaller plastic fragments which 

eventually become undetectable to the naked eye. 

There are many uses for microplastics. For example, microbeads are used in personal care 

products such as exfoliants in face scrubs. Microplastics are also used to deliver drugs in some 

medical applications (Browne et al. 2007). Further, fibers that shed from synthetic clothing and 

rope are microplastics (Thompson et al. 2004, Browne et al. 2007), as are particles used in 

“media blasting” processes to clean boat hulls and large machinery (Browne et al. 2007). Many 

of these microplastics, microbeads, and fibers are small enough to pass through wastewater 

treatment plants and enter a watershed (Browne et al. 2007). 

Impacts of microplastics on wildlife are not well understood at this time. However, a number of 

organisms, both vertebrates and invertebrates have been found to ingest microplastics. These 

examples represent numerous organisms with differing feeding mechanisms, including 

detritivores, deposit feeders, and filter feeders. Examples include scleractinian corals (Hall et al. 

2015), mussels (Mytilus edulis; Browne et al. 2007), fish (Carpenter et al. 1972), as well as 

lugworms, amphipods, and barnacles (Thompson et al. 2004). 

Scientists are also concerned that organisms ingesting plastic debris may be exposed to 

contaminants sorbed to the plastic (Teuten et al. 2007). Plastic debris provides a sink and a 

source for chemical contaminants. Additives used in the manufacturing of plastics can leach 

from the plastics into the marine environment (Andrady 2011). On the other hand, hydrophobic 

contaminants present in the water may sorb to the plastic particles (Carpenter et al. 1972, Teuten 

et al. 2007, Andrady 2011). Thus, microplastics may provide a mechanism to transport 

concentrated contaminants to organisms (Browne et al. 2007). 

1 | Page 
 

 

 

 

 

 

 

 

Laboratory Methods for the Analysis of Microplastics 

Introduction to Methods Manual 

This document is a methods manual for measuring microplastic in the environment. This manual 

outlines step-by-step instructions for quantifying microplastic in marine environmental samples, 

including processes to streamline terminology and approaches. 

The methods described here were determined after careful study and laboratory work conducted 

through a grant from the NOAA Marine Debris Program to the University of Washington, 

Tacoma. Project goals sought to streamline the terminology and techniques used to assess 

microplastic concentrations in marine environmental samples, and to develop laboratory 

procedures to quantify microplastic particles in marine surface waters and bed sediments, as well 

as personal care products. An overarching aim was to provide scientists and educators with 

simple techniques that are reproducible and robust without requiring extensive equipment, and to 

describe a method that could be easily adopted by groups around the world. 

Depending on the study aims and environmental collection techniques, these techniques can be 

used to calculate concentrations of microplastics using a variety of metrics, including per piece, 

per mass, or per volume. Considering metrics is important for comparing results with other 

researchers. For guidelines and considerations when conducting microplastic analyses, as well as 

calculations, see the appendices. 

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Laboratory Methods for the Analysis of Microplastics 

1.0 Methods for the Analysis of
 

Microplastics in Water Samples
 

This method can be used for the analysis of plastic debris as suspended solids in water samples 

collected by a surface net. Plastics include hard plastics, soft plastics (e.g. foams), films, line, 

fibers, and sheets. The method involves the filtration of solids obtained in a 0.335 mm surface 

sampling net (e.g. a manta net for surface water tows) through 5.6-mm and/or 0.3-mm sieves to 

isolate the solid material of the appropriate size (Figures 1-4). The sieved material is dried to 

determine the solids mass in the sample. The solids are subjected to wet peroxide oxidation 

(WPO) in the presence of a Fe(II) catalyst to digest labile organic matter. The plastic debris 

remains unaltered. The WPO mixture is subjected to density separation in NaCl(aq) to isolate the 

plastic debris through flotation. The floating solids are separated from the denser undigested 

mineral components using a density separator. The floating plastic debris is collected in the 

density separator using a custom 0.3-mm filter, air-dried, and plastic material is removed and 

weighed to determine the microplastics concentration. 

Figure 1. Researchers use a manta net to collect surface water samples in the Thea Foss 

Waterway, Puget Sound, Washington. 

3 | Page 
 

 

Laboratory Methods for the Analysis of Microplastics 

Figure 2. A water sample from Puget Sound is shown before processing. 

Figure 3. Note the variety in these field samples, all collected from surface waters. 

4 | Page 
 

 

 

 

 

Laboratory Methods for the Analysis of Microplastics 

Figure 4. Sieving and rinsing field samples. 

An overview of the analysis of microplastics in water is shown in Figure 

5. 

This method is applicable for the determination of many common plastics including polyethylene 

(0.91-0.97 g/mL), polypropylene (0.94 g/mL), polyvinyl chloride (1.4 g/mL), and polystyrene 

(1.05 g/mL). 

The plastic debris analyzed by this method is considered microplastic and ranges in size from 5 

mm to 0.3 mm. Microplastic debris is operationally defined by this method as any solid material 

in the appropriate size range that is resistant to wet peroxide oxidation, exhibits flotation in a 5 M 

NaCl (d=1.15 g/mL) or ~5.4 M lithium metatungstate (d=1.62 g/mL) solution, and passes 

positive visual inspection under a microscope at 40X power. 

5 | Page 
 

 

 

 

 

 

Laboratory Methods for the Analysis of Microplastics 

Wet sieve 

(1.2) 

WPO 

(1.5) 

Density separation 

(1.6) 

Water sample 

(1) 

Discard or 

Archive 

Gravimetric 

Analysis 

(1.8) 

>0.3 mm 

fraction 

>5 mm 

fraction 

Microscope exam 

(1.7) 

Mass of total 

solids 

(1.3-1.4) 

Figure 5. Flow diagram for the analysis of microplastics in water samples. Note numbers refer 

to the numbers in this section. 

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Laboratory Methods for the Analysis of Microplastics 

1.1 Apparatus and Materials 

•	 Stainless steel sieves, each measuring 8 in (diameter) and 2 in (depth) 

o	 5.6 mm mesh (Number 3.5) 

o	 1 mm mesh (Number 18) 

o	 0.3 mm mesh (Number 50) 

•	 Squirt bottle containing distilled water 

•	 500-mL glass beaker 

•	 Analytical balance (precise to 0.1 mg) 

•	 Metal spatula 

•	 Drying oven (90oC) 

•	 Iron (Fe(II)) solution (0.05 M) 

o	 Prepared by adding 7.5 g of FeSO4°7H20 (= 278.02 g/mol) to 500 mL of water 

and 3 mL of concentrated sulfuric acid 

•	 30% Hydrogen peroxide 

•	 Stir bar 

•	 Laboratory hot plate 

•	 Watchglass 

•	 Sodium chloride (commercial table salt is sufficient) 

•	 Standard Metal Forceps 

•	 Density separator, which is assembled using the following method: 

o	 A glass funnel (122-mm in diameter) is fitted with a 50-mm segment of latex 

tubing on the bottom of the stem and a pinch clamp is attached to control liquid 

flow from the funnel. 

•	 Retort stand 

•	 O-ring 

•	 Spring clamp (2-inch) 

•	 Aluminum foil 

•	 Customized small sieves, each measuring 59 mm (diameter), which may be fabricated 

using either of two methods: 

o	 Use polypropylene Büchner funnels and nylon mesh. The funnel bottoms are 

removed and nylon mesh is glued to the modified funnel. Three funnels, with 

varying nylon mesh size (5 mm, 1 mm, and 0.3 mm), are needed. 

o	 Cut sections of polyvinylchloride (PVC) pipe, approximately 75 mm (diameter) 

and 25 mm (length), and use gel-type superglue to attach nylon mesh to one end 

of the pipe. Three funnels, with varying nylon mesh size (5 mm, 1 mm, and 0.3 

mm), are needed. 

•	 4-mL glass vials 

•	 Dissecting microscope (40X magnification) 

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Laboratory Methods for the Analysis of Microplastics 

1.2 Wet Sieving 

•	 Pour the sample through a stacked arrangement of 5.6-mm (No. 3.5) and 0.3-mm (No. 

50) stainless steel mesh sieves (Figure 4). 

•	 Rinse sample with squirt bottle filled with distilled water to transfer all residual solids to 

the sieves. This also removes salts from the field sample. Repeat as necessary. 

•	 Rinse sieves thoroughly using distilled water. Ensure all material has been well washed, 

drained, and sorted. 

•	 Discard or archive material retained on 5-mm sieve, as appropriate, depending on 

individual study objectives. 

1.3 Transfer Sieved Solids 

•	 Weigh a clean and dry 500-mL beaker to the nearest 0.1 mg. (a) 

•	 Transfer solids collected in the 0.3-mm sieve into the tared beaker using a spatula and 

minimal rinsing with a squirt bottle containing distilled water. 

•	 Ensure all solids are transferred into the beaker. 

•	 Place beaker in 90o

C drying oven for 24 hours or longer to sample dryness (Figure 6). 

Figure 6. Sieved samples are dried in an oven to determine dry weight. 

1.4 Determine the Mass of Total Solids 

•	 Determine the mass of the beaker with dried solids using an analytical balance to the 

nearest 0.1 mg. (b) 

•	 Subtract the mass of the tared beaker (a) to provide the mass of total solids (c) collected 

on the sieve. (Formula: b – a = c)* See Appendix 5.1.1 for formulae. This is the mass of 

all microplastics and natural materials. 

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Laboratory Methods for the Analysis of Microplastics 

1.5 Wet Peroxide Oxidation (WPO) 

CAUTION: This mixture is highly reactive. Please review and follow your laboratory safety 

practices and policies for handling this mixture before completing this analysis. 

•	 Add 20 mL of aqueous 0.05 M Fe(II) solution to the beaker containing the 0.3 mm size 

fraction of collected solids (Figure 7). 

Figure 7. Addition of iron sulfate solution catalyzes the reaction. 

•	 Add 20 mL of 30% hydrogen peroxide. CAUTION: this solution can boil violently if 

heated >75oC (Figure 8). 

Figure 8. Addition of hydrogen peroxide oxidizes natural organic material. 

•	 Let mixture stand on lab bench at room temperature for five minutes prior to proceeding 

to the next step. 

•	 Add a stir bar to the beaker and cover with a watchglass. 

•	 Heat to 75o

C on a hotplate. 

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Laboratory Methods for the Analysis of Microplastics 

•	 As soon as gas bubbles are observed at the surface, remove the beaker from the hotplate 

and place it in the fume hood until boiling subsides. If reaction appears to have the 

potential to overflow the beaker, add distilled water to slow the reaction. 

•	 Heat to 75oC for an additional 30 minutes. 

•	 If natural organic material is visible, add another 20 mL of 30% hydrogen peroxide. 

•	 Repeat until no natural organic material is visible. 

•	 Add ~6 g of salt (NaCl) per 20 mL of sample to increase the density of the aqueous 

solution (~5 M NaCl). 

•	 Heat mixture to 75oC until the salt dissolves. 

1.6 Density Separation 

•	 Transfer the WPO solution from step 1.5 to the density separator (Figure 9). 

Figure 9. A sample is depicted in a glass funnel to separate plastic. 

•	 Rinse the WPO beaker with distilled water to transfer all remaining solids to the density 

separator. 

•	 Cover loosely with aluminum foil. 

•	 Allow solids to settle overnight. 

•	 Visually inspect settled solids for any microplastics. If any are present, drain the settled 

solids from the separator and remove microplastics using forceps. Archive or discard. 

•	 Drain settled solids from the separator and discard. 

•	 Collect floating solids in a clean 0.3-mm custom sieve (Figure 10). 

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Laboratory Methods for the Analysis of Microplastics 

Figure 10. Floating material is drained into a custom sieve. 

•	 Rinse the density separator several times with distilled water to transfer all solids to the 

0.3-mm sieve. 

•	 Allow the sieve to air dry while loosely covered with aluminum foil for 24 hours (Figure 

11). 

Figure 11. A prepared sample is ready for microscope examination. 

1.7 Microscope Exam 

•	 Weigh a clean and dry 4-mL vial. Include the label and cap. (d) 

•	 Under a dissecting microscope at 40X magnification (Figure 12), use forceps to collect 

identifiable microplastics from the 0.3-mm sieve and transfer them to the tared vial 

(Figure 13). See Appendix 5.2 for more guidance. 

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Laboratory Methods for the Analysis of Microplastics 

Figure 12. Microplastic fragments are extracted from the prepared sample during a microscope 

examination. 

Figure 13. A final microplastic sample is preserved in a vial. 

1.8 Gravimetric Analysis 

•	 Weigh the mass of the vial and microplastics to the nearest 0.1 mg. (e) 

•	 Subtract the mass of the tared vial (d) to provide the mass of microplastics (f) collected 

on the sieve. (Formula: e-d=f)* See Appendix 5.1.1 for formulae. This is the mass of all 

microplastics. 

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Laboratory Methods for the Analysis of Microplastics 

2.0 Methods for the Analysis of
 

Microplastics in Beach Samples
 

This method can be used for the analysis of plastic debris in beach sand collected by shovel or 

spade. Plastics include hard plastics, soft plastics (e.g., foams), films, line, fibers, and sheets. The 

method involves sieving dry beach samples to 5 mm to remove large macroscopic debris. 

An overview of the analysis of microplastics in beach sand is shown in 

Figure 14. 

This method is applicable for the determination of many common plastics including polyethylene 

(0.91-0.97 g/mL), polypropylene (0.94 g/mL), polyvinyl chloride (1.4 g/mL), and polystyrene 

(1.05 g/mL). 

The plastic debris analyzed by this method is considered microplastic and ranges in size from 5 

mm to 0.3 mm. Microplastic debris is operationally defined by this method as any solid material 

in the appropriate size range that is resistant to wet peroxide oxidation, exhibits flotation in a 5 M 

NaCl (d=1.15 g/mL) or ~5.4 M lithium metatungstate (d=1.62 g/mL) solution, and passes 

positive visual inspection under a microscope at 40X power. 

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WPO 

(2.5) 

Density separation 

(2.6) 

Gravimetric 

Analysis 

(2.8) 

Microscope exam 

(2.7) 

Mass of total 

solids 

(2.4) 

Discard 

Laboratory Methods for the Analysis of Microplastics 

Density separation 

(2.3) 

Beach sample 

(2) 

Floating solids Settled solids 

Sample 

preparation 

(2.2) 

Figure 14. Flow diagram for the analysis of microplastics in beach samples. Note numbers refer 

to the numbers in this section. 

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Laboratory Methods for the Analysis of Microplastics 

2.1 Apparatus and Materials 

•	 800-mL and 500-mL glass beakers 

•	 Analytical balance (precise to 0.1 mg) 

•	 Drying oven (90o

C) 

•	 Lithium metatungstate solution 

o	 Prepared from commercial lithium metatungstate solution (=2.95 g/mL) and 

diluted as needed with deionized water to 1.6 g/mL 

•	 Metal spatula 

•	 Customized small sieves, each measuring 59 mm (diameter), which may be fabricated 

using either of two methods: 

o	 Use polypropylene Büchner funnels and nylon mesh. The funnel bottoms are 

removed and nylon mesh is glued to the modified funnel. Three funnels, with 

varying nylon mesh size (5 mm, 1 mm, and 0.3 mm), are needed. 

o	 Cut sections of polyvinylchloride (PVC) pipe, approximately 75 mm (diameter) 

and 25 mm (length), and use gel-type superglue to attach nylon mesh to one end 

of the pipe. Three funnels, with varying nylon mesh size (5 mm, 1 mm, and 0.3 

mm), are needed. 

•	 Standard Metal Forceps 

•	 Iron (Fe(II)) solution (0.05 M) 

o	 Prepared by adding 7.5 g of FeSO4°7H20 (= 278.02 g/mol) to 500 mL of water 

and 3 mL of concentrated sulfuric acid 

•	 30% Hydrogen peroxide 

•	 Stir bar 

•	 Watchglass 

•	 Laboratory hot plate 

•	 Squirt bottle containing distilled water 

•	 Sodium chloride (commercial table salt is sufficient) 

•	 Density separator, which is assembled using the following method: 

o	 A glass funnel (122-mm in diameter) is fitted with a 50-mm segment of latex 

tubing on the bottom of the stem and a pinch clamp is attached to control liquid 

flow from the funnel. 

•	 Retort stand 

•	 O-ring 

•	 Spring clamp (2-inch) 

•	 Aluminum foil 

•	 4-mL glass vials 

•	 Dissecting microscope (40X magnification) 

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Laboratory Methods for the Analysis of Microplastics 

2.2 Beach Sediment Sample Preparation 

•	 Weigh and label a clean and dry 800-mL beaker to the nearest 0.1 mg. (a) 

• Weigh 400 g of wet sediment to the nearest 0.1 mg and add to the beaker (Figure 15). 

Figure 15. A beach sand (or sediment) sample is weighed. 

•	 Dry in a drying oven at 90°C overnight or until sample dryness. 

•	 Weigh the dried beaker and material to determine the dry sample weight. (b) 

•	 Subtract the mass of the tared beaker (a) to provide the mass of total solids (c). (Formula: 

b – a = c)* See Appendix 5.1.2 for formulae. This is the mass of the sample matrix. 

2.3 Density Separation 

•	 Add 300 mL of aqueous lithium metatungstate (d=1.6 g/mL) solution to the dried 

sediments in the 800-mL beaker (Figure 16). Be sure to adjust density to 1.6 g/mL. See 

Section 2.1 (Apparatus and Materials) for preparation instructions. 

Figure 16. Lithium metatungstate is added to a sediment sample. 

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Laboratory Methods for the Analysis of Microplastics 

•	 Vigorously stir the sand-water mixture in the beaker for several minutes with a spatula to 

float out the microplastics. 

•	 Transfer all floating solids in the beaker to the custom 0.3 mm sieve. Rinse beaker with 

distilled water to transfer all residual solids to the sieves. 

•	 Remove any visible material > 5 mm with forceps. Either discard or archive, depending 

on individual study objectives. 

•	 Discard or archive settled solids left in the beaker. 

•	 Weigh and label a clean and dry 500-mL beaker to the nearest 0.1 mg. (a) 

•	 Transfer the solids collected on the 0.3-mm sieve into the tared 500-mL beaker. 

•	 Repeat until all of the floating debris is collected. 

•	 Dry the beaker and solids in a drying oven at 90oC for 24 hours or longer to sample 

dryness (Figure 6). 

•	 Recover and filter the metatungstate solution in a separate bottle to recycle for future use 

(Figure 17). 

Figure 17. The lithium metatungstate solution is sieved and saved. 

2.4 Determine the Mass of Total Solids 

•	 Determine the mass of the beaker with dried solids using an analytical balance to the 

nearest 0.1 mg. (b) 

•	 Subtract the mass of the tared beaker (a) to provide the mass of total solids (c). (Formula: 

b – a = c)* See Appendix 5.1.2 for formulae. This is the mass of all microplastics and 

natural materials. 

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Laboratory Methods for the Analysis of Microplastics 

2.5 Wet Peroxide Oxidation (WPO) 

CAUTION: This mixture is highly reactive. Please review and follow your laboratory safety 

practices and policies for handling this mixture before completing this analysis. 

•	 Add 20 mL of aqueous 0.05 M Fe(II) solution to the beaker containing the 0.3 mm size 

fraction of collected solids (Figure 7). 

•	 Add 20 mL of 30% hydrogen peroxide. CAUTION: this solution can boil violently if 

heated >75o

C (Figure 8). 

•	 Let mixture stand on lab bench at room temperature for five minutes prior to proceeding 

to the next step. 

•	 Add a stir bar to the beaker and cover with a watchglass. 

•	 Heat to 75oC on a hotplate. 

•	 As soon as gas bubbles are observed at the surface, remove the beaker from the hotplate 

and place it in the fume hood until boiling subsides. If the reaction appears to have the 

potential to overflow the beaker, add distilled water to slow the reaction. 

•	 Heat to 75o

C for an additional 30 minutes. 

•	 If natural organic material is visible, add another 20 mL of 30% hydrogen peroxide. 

•	 Repeat until no natural organic material is visible. 

•	 Add ~6 g of salt (NaCl) per 20 mL of sample to increase the density of the aqueous 

solution (~5 M NaCl). 

•	 Heat mixture to 75oC until the salt dissolves. 

2.6 Density Separation 

•	 Transfer the WPO solution from step 2.5 to the density separator (Figure 9). 

•	 Rinse the WPO beaker with distilled water to transfer all remaining solids to the density 

separator. 

•	 Cover loosely with aluminum foil. 

•	 Allow solids to settle overnight. 

•	 Visually inspect settled solids for any microplastics. If any are present, drain the settled 

solids from the separator and remove microplastics using forceps. Archive or discard. 

•	 Drain settled solids from the separator and discard. 

•	 Collect floating solids in a clean 0.3-mm custom sieve (Figure 10). 

•	 Rinse the density separator several times with distilled water to transfer all solids to the 

0.3-mm sieve. 

•	 Allow the sieve to air dry while loosely covered with aluminum foil for 24 hours (Figure 

11). 

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Laboratory Methods for the Analysis of Microplastics 

2.7 Microscope Exam 

•	 Weigh a clean and dry 4-mL vial. Include the label and cap. (g) 

•	 Under a dissecting microscope at 40X magnification (Figure 12), use forceps to collect 

identifiable microplastics from the 0.3-mm sieve and transfer them to the tared vial 

(Figure 13). See Appendix 5.2 for more guidance. 

2.8 Gravimetric Analysis 

•	 Weigh the mass of the vial and microplastics to the nearest 0.1 mg. (h) 

•	 Subtract the mass of the tared vial (g) to provide the mass of microplastics (i) collected 

on the sieve. (Formula: h - g = i)* See Appendix 5.1.2 for formulae. This is the mass of 

all microplastics. 

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Laboratory Methods for the Analysis of Microplastics 

3.0 Methods for the Analysis of
 

Microplastics in Bed Samples
 

This method can be used for the analysis of plastic debris in bed sediments collected by corer or 

grab sampler (e.g. Ponar sampler). Plastics include hard plastics, soft plastics (e.g., foams), films, 

line, fibers, and sheets. The method involves an initial disaggregation of dried sediments. The 

disaggregated sediments are sieved using stacked 5-mm and 0.3-mm sieves. Microplastics 

collected on the 0.3-mm sieve are subjected to wet peroxide oxidation (WPO) in the presence of 

a Fe(II) catalyst to digest labile organic matter. The plastic debris remains unaltered. The WPO 

mixture is subjected to density separation in NaCl(aq) to isolate the plastic debris through 

flotation. The floating solids are separated from the denser undigested mineral components using 

a density separator. The floating plastic debris is collected in the density separator using a 

custom 0.3-mm filter, air-dried, and plastic material is removed and weighed to determine the 

microplastics concentration. 

An overview of the analysis of microplastics in bed sediments is shown 

in Figure 18. 

This method is applicable for the determination of many common plastics including polyethylene 

(0.91-0.97 g/mL), polypropylene (0.94 g/mL), polyvinyl chloride (1.4 g/mL), and polystyrene 

(1.05 g/mL). 

The plastic debris analyzed by this method is considered microplastics and ranges in size from 5 

mm to 0.3 mm. Microplastic debris is operationally defined by this method as any solid material 

in the appropriate size range that is resistant to wet peroxide oxidation, exhibits flotation in 5 M 

NaCl (d=1.15g/mL) or ~5.4 M lithium metatungstate (d=1.62 g/mL) solution, and passes positive 

visual inspection under a microscope at 40X power. 

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Laboratory Methods for the Analysis of Microplastics 

Sediment sample 

(3) 

Sample 

preparation 

(3.2) 

Wet sieve 

(3.3) 

Mass of total 

solids 

(3.4) 

WPO 

(3.7) 

Density separation 

(3.8) 

Gravimetric 

Analysis 

(3.10) 

Microscope exam 

(3.9) 

Density separation 

(3.5) 

Discard 

Settled solids 

Mass of total 

solids 

(3.6) 

Floating solids 

Figure 18. Flow diagram for the analysis of microplastics in bed samples. Note numbers refer to 

the numbers in this section. 

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Laboratory Methods for the Analysis of Microplastics 

3.1 Apparatus and Materials 

•	 800-mL and 500-mL glass beakers 

•	 Analytical balance (precise to 0.1 mg) 

•	 Drying oven (90o

C) 

•	 Potassium metaphosphate 

o	 Prepared by dissolving the salt in deionized water to 5.5 g/L 

•	 Stir bar 

•	 Customized small sieves, each measuring 59 mm (diameter), which may be fabricated 

using either of two methods: 

o	 Use polypropylene Büchner funnels and nylon mesh. The funnel bottoms are 

removed and nylon mesh is glued to the modified funnel. Three funnels, with 

varying nylon mesh size (5 mm, 1 mm, and 0.3 mm), are needed. 

o	 Cut sections of polyvinylchloride (PVC) pipe, approximately 75 mm (diameter) 

and 25 mm (length), and use gel-type superglue to attach nylon mesh to one end 

of the pipe. Three funnels, with varying nylon mesh size (5 mm, 1 mm, and 0.3 

mm), are needed. 

•	 Standard Metal Forceps 

•	 Plastic squirt bottle containing distilled water 

•	 Lithium metatungstate solution 

o	 Prepared from commercial lithium metatungstate solution (=2.95 g/mL) and 

diluted as needed with deionized water to 1.6 g/mL 

•	 Metal spatula 

•	 Iron (Fe(II)) solution (0.05 M) 

o	 Prepared by adding 7.5 g of FeSO4°7H20 (= 278.02 g/mol) to 500 mL of water 

and 3 mL of concentrated sulfuric acid 

•	 30% Hydrogen peroxide 

•	 Watchglass 

•	 Laboratory hot plate 

•	 Sodium chloride (commercial table salt is sufficient) 

•	 Density separator, which is assembled using the following method: 

o	 A glass funnel (122-mm in diameter) is fitted with a 50-mm segment of latex 

tubing on the bottom of the stem and a pinch clamp is attached to control liquid 

flow from the funnel. 

•	 Retort stand 

•	 O-ring 

•	 Spring clamp (2-inch) 

•	 Aluminum foil 

•	 4-mL glass vials 

•	 Dissecting microscope (40X magnification) 

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Laboratory Methods for the Analysis of Microplastics 

3.2 Bed Sediment Sample Preparation 

3.2.1 Dry Bed Sediments 

•	 Weigh and label a clean and dry 800-mL beaker to the nearest 0.1 mg. (a) 

•	 Weigh 400 g of wet sediment to the nearest 0.1 mg and add to the beaker (Figure 15). 

•	 Dry in a drying oven at 90°C overnight or until sample dryness. 

•	 Weigh the dried beaker and material to determine the dry sample weight. (b) 

•	 Subtract the mass of the tared beaker (a) to provide the mass of total solids (c). (Formula: 

b – a = c)* See Appendix 5.1.2 for formulae. This is the mass of the sample matrix. 

3.2.2 Disaggregate Dried Bed Sediments 

•	 Add 400 mL of potassium metaphosphate (5.5 g per liter of water) to the sediment 

sample. 

•	 Add a stir bar to the beaker and mix for 1 hour at high rpm. 

3.3 Wet Sieving and Transfer of Sieved Solids 

•	 Pour the sample through 0.3-mm sieve. 

•	 Rinse the sample beaker with distilled water to transfer all residual solids to the sieve. 

•	 Repeat as necessary. 

•	 Ensure all material has been well washed, drained, and sorted. 

•	 Remove any visible material > 5 mm with forceps. Either discard or archive, depending 

on individual study objectives. 

•	 Weigh and label a clean and dry 500-mL beaker to the nearest 0.1 mg. (a) 

•	 Transfer the solids retained on 0.3-mm sieves to tared 500-mL beakers using a spatula 

and minimal rinsing with a squirt bottle containing distilled water. 

•	 Ensure all solids are transferred to the beaker. 

•	 Dry the beakers and solids in a drying oven at 90o

C for 24 hours or longer to sample 

dryness (Figure 6). 

3.4 Determine the Mass of Total Solids (Sample Matrix) 

•	 Determine the mass of beaker with dried solids using an analytical balance to nearest 0.1 

mg. (b) 

•	 Subtract the mass of the tared beaker (a) to provide the mass of total solids (c). (Formula: 

b – a = c)* See Appendix 5.1.2 for formulae. This is the mass of the filtered sample 

matrix. 

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Laboratory Methods for the Analysis of Microplastics 

3.5 Density Separation 

•	 Add 300 mL of aqueous lithium metatungstate (d=1.6 g/mL) solution to the dried 

sediments in the beaker (Figure 16). Be sure to adjust density to1.6 g/mL. See Section 3.1 

(Apparatus and Materials) for preparation instructions. 

•	 Vigorously stir the sand-water mixture in the beaker for several minutes with a spatula to 

float out the microplastics. 

•	 Transfer all floating solids in the beaker to the custom 0.3 mm sieve. Rinse beaker with 

distilled water to transfer all residual solids to the sieves. 

•	 Weigh and label a clean and dry 500-mL beaker to the nearest 0.1 mg. (a) 

•	 Transfer the solids collected on the 0.3-mm sieve into tared 500-mL beaker. 

•	 Dry the beaker and solids in a drying oven at 90o

C for 24 hours or longer to sample 

dryness (Figure 6). 

•	 Recover and filter the metatungstate solution in a separate bottle to recycle for future use 

(Figure 17). 

3.6 Determine the Mass of Total Solids (Microplastics and Natural Materials) 

•	 Determine the mass of beaker with dried solids using an analytical balance to nearest 0.1 

mg. (b) 

•	 Subtract the mass of the tared beaker (a) to provide the mass of total solids (c). (Formula: 

b – a = c)* See Appendix 5.1.2 for formulae. This is the mass of all microplastics and 

natural materials. 

3.7 Wet Peroxide Oxidation (WPO) 

CAUTION: This mixture is highly reactive. Please review and follow your laboratory safety 

practices and policies for handling this mixture before completing this analysis. 

•	 Add 20 mL of aqueous 0.05 M Fe(II) solution to the beaker containing the 0.3 mm size 

fraction of collected solids (Figure 7). 

•	 Add 20 mL of 30% hydrogen peroxide. CAUTION: this solution can boil violently if 

heated >75o

C (Figure 8). 

•	 Let mixture stand on lab bench at room temperature for five minutes prior to proceeding 

to the next step. 

•	 Add a stir bar to the beaker and cover with a watchglass. 

•	 Heat to 75oC on a hotplate. 

•	 As soon as gas bubbles are observed at the surface, remove the beaker from the hotplate 

and place it in the fume hood until boiling subsides. If reaction appears to have the 

potential to overflow the beaker, add distilled water to slow the reaction. 

•	 Heat to 75oC for an additional 30 minutes. 

•	 If natural organic material is visible, add another 20 mL of 30% hydrogen peroxide. 

•	 Repeat until no natural organic material is visible. 

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Laboratory Methods for the Analysis of Microplastics 

•	 Add ~6 g of salt (NaCl) per 20 mL of sample to increase the density of the aqueous 

solution (~5 M NaCl). 

•	 Heat mixture to 75oC until the salt dissolves. 

3.8 Density Separation 

•	 Transfer the WPO solution from step 3.7 to the density separator (Figure 9). 

•	 Rinse the WPO beaker with distilled water to transfer all remaining solids to the density 

separator. 

•	 Loosely cover with aluminum foil. 

•	 Allow solids to settle overnight. 

•	 Visually inspect settled solids for any microplastics. If any are present, drain the settled 

solids from the separator and remove microplastics using forceps. Archive or discard. 

•	 Drain settled solids from separator and discard. 

•	 Collect floating solids in a clean 0.3-mm custom sieve (Figure 10). 

•	 Rinse the density separator several times with distilled water to transfer all solids to the 

0.3-mm sieve. 

•	 Allow the sieve to air dry while loosely covered with aluminum foil for 24 hours (Figure 

11). 

3.9 Microscope Exam 

•	 Weigh a clean and dry 4-mL vial. Include the label and cap. (j) 

•	 Under a dissecting microscope at 40X magnification (Figure 12), use forceps to collect 

identifiable microplastics from the 0.3-mm sieve and transfer them to the tared vial 

(Figure 13). See Appendix 5.2 for more guidance. 

3.10 Gravimetric Analysis 

•	 Weigh the mass of the vial and microplastics to the nearest 0.1 mg. (k) 

•	 Subtract the mass of the tared vial (j) to provide the mass of microplastics (l) collected on 

the sieve. (Formula: k – j = l)* See Appendix 5.1.2 for formulae. This is the mass of all 

microplastics. 

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Laboratory Methods for the Analysis of Microplastics 

4.0 Cited References 

Andrady, A.L. (2011). Microplastics in the marine environment. Marine Pollution Bulletin, 

62:1596-1605. doi:10.1016/j.marpolbul.2011.05.030 

Arthur, C., Baker, J., & Bamford, H., Eds. Proceedings of the International Research Workshop 

on the Occurrence, Effects, and Fate of Microplastic Marine Debris. Sept 9-11, 2008. NOAA 

Technical Memorandum NOS-OR&R-30, 2009. 

Browne, M.A., Galloway, T., & Thompson, R. (2007). Microplastic – an emerging contaminant 

of potential concern? Integrated Environmental Assessment and Management, 3(4):559-561. 

DOI: 10.1002/ieam.5630030412 

Carpenter, E.J., Anderson, S.J., Harvey, G.R., Miklas, H.P., & Peck, B.B. (1972). Polystyrene 

spherules in coastal waters. Science, 17(4062):749-750. http://links.jstor.org/sici?sici=0036­

8075%2819721117%293%3A178%3A4062%3C749%3APSICW%3E2.0.CO%3B2-E 

Cooper, D.A., & Corcoran, P.L. (2010). Effects of mechanical and chemical processes on the 

degradation of plastic beach debris on the island of Kauai, Hawaii. Marine Pollution Bulletin, 

60:650-654. doi:10.1016/j.marpolbul.2009.12.026 

Hall, N.M., Berry, K.L.E., & Rintoul, L. (2015). Microplastic ingestion by scleractinian corals. 

Marine Biology, 162:725-732. DOI 10.1007/s00227-015-2619-7 

Teuten, E.L., Rowland, S.J., Galloway, T.S., & Thompson, R.C. (2007). Potential for plastics to 

transport hydrophobic contaminants. Environmental Science & Technology, 41(22):7759­

7764. DOI: 10.1021/es071737s 

Thompson, R.C., Olsen, Y., Mitchell, R.P., Davis, A., Rowland, S.J., John, A.W.G., McGonigle, 

D., & Russell, A.E. (2004). Lost at sea: where is all the plastic? Science, 

304:838. DOI:10.1126/science.1094559 

Woodall, L.C., Gwinnett, C., Packer, M., Thompson, R.C., Robinson, L.F., & Paterson, G.L.J. 

(2015). Using a forensic science approach to minimize environmental contamination and to 

identify microfibres in marine sediments. Marine Pollution Bulletin 95:40­

46. http://dx.doi.org/10.1016/j.marpolbul.2015.04.044 

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Laboratory Methods for the Analysis of Microplastics 

5.0 Appendices 

5.1 Appendix of Calculations 

5.1.1 Water Samples 

Mass of Total Solids 

To calculate mass of total solids in a sample, which includes both natural material and 

microplastics, use the following formula (see Section 1.4): 

mass(total solids) = mass(beaker with dried solids) – mass(tared beaker) 

(c = b - a) 

Mass of Microplastics 

To calculate mass of microplastics in a sample, use the following formula (see Sections 1.8): 

mass(microplastic) = mass(vial with particles) – mass(tared vial) 

(f = e - d) 

5.1.2 Beach and Bed Samples 

Mass of Total Solids 

To calculate mass of total solids in a sample, which includes both natural material and 

microplastics, use the following formula (see Sections 2.2 and 2.4; Sections 3.4 and 3.6): 

mass(total solids) = (mass(beaker with dried solids) – mass(tared beaker)) 

(c = b - a) 

*Note: if you have samples with a lot of organic material or debris, you can sieve the samples 

using a 5mm, 1mm and 0.3mm sieve during the beginning steps. You will sort and weigh the 

1mm and 0.3mm samples separately and add them together to calculate the total mass of solids, 

using the following formula (see Appendix 5.2 for more information): 

mass(total solids) = (mass(beaker with dried 1-mm solids) – mass(tared beaker)) + 

(mass(beaker with dried 0.3-mm solids) – mass(tared beaker)) 

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Laboratory Methods for the Analysis of Microplastics 

Mass of Microplastics 

To calculate mass of microplastics in a sample, use the following formula (see Sections 2.8 and 

3.10): 

mass(microplastic) = (mass(vial with particles) – mass(tared vial)) 

(i = h - g) --- > for beach samples 

(l = k - j) --- > for bed samples 

*Note: if you have samples with a lot of organic material or debris, you can sieve the samples 

using a 5mm, 1mm and 0.3mm sieve during the beginning steps. You will sort and weigh the 

1mm and 0.3mm samples separately and add them together to calculate the total mass of 

microplastics, using the following formula (see Appendix 5.2 for more information): 

mass(microplastic) = (mass(vial with 1-mm particles) – mass(tared vial)) + 

(mass(vial with 0.3-mm particles) – mass(tared vial)) 

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Laboratory Methods for the Analysis of Microplastics 

5.2 Appendix of Guidelines and Considerations 

Technique 

Contamination of Samples 

When collecting samples in the field and processing samples in the laboratory, avoid wearing 

polyester-type clothing (fleece jackets, polyester lab coats, etc.), because they may contaminate 

your samples. For more information on the contamination of samples from clothing, see Woodall 

et al. (2015). It is also good practice to inspect all of the equipment made from plastic (sieves, 

squirt bottle, etc.) before use to ensure that there is no contamination from of these materials to 

the environmental samples. Sieves should be washed and sonicated before and after use. 

Guidelines for Microscope Inspection 

When identifying environmental samples, there is natural material that may be mistaken for 

plastics. Natural material remaining at the picking stage of each process may look like plastic, 

including grass sheaths, pine needles, diatom tests, and salt crystals. To rule out these particles, 

drag your forceps across the particles. If they powder or fall apart, then the pieces are not plastic. 

If the particles retain their shape, then they are properly identified as plastic. Another approach is 

to become familiar with reference plastic materials. 

High Mass Samples 

To avoid error in samples that have more organic carbon (e.g., lots of natural grass, pine needles, 

wood, etc.), sieve samples by 5 mm, 1 mm, and 330 μm at the beginning steps. Archive or 

discard material > 5 mm. Process the 1 mm and 330 μm fractions separately. Combine results to 

be used in an area or basin analysis. See Appendix 5.1.2. 

Time of Water Sample Collection 

Water sample collection is standardized to a 15-minute manta tow. The tow time is shortened if 

the net becomes clogged with material (typically a plankton bloom) or a large amount of material 

enters the net (typically flotsam or sea grass). Essentially, if the net loses its ability to sieve or 

begins to sink, end the tow and recover the sample collected. 

Spike and Recovery Rates 

1.	 Water Samples 

a.	 Water samples were spiked with two sizes of polyethylene microplastic pellets. 95% 

of the 1000 μm pellets and 60-85% of the 300 μm pellets were recovered. 

b.	 Water samples were spiked with 3 types of polymer microplastic pellets. 88% of the 

polyethylene pellets, 80% polypropylene pellets, and 92% polyvinyl chloride pellets 

were recovered. 

2.	 Bed Sediments: 

a.	 Bed sediments were spiked with a given mass of polyethylene microplastic pellets 

with an 81% recovery. 

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Laboratory Methods for the Analysis of Microplastics 

FT-IR Work 

Two environmental samples were analyzed using Fourier-Transform Infrared Spectroscopy. 

Sample 1 contained 219 pieces and Sample 2 contained 63 pieces. Sample 1 contained 72% 

polyethylene, 18% polypropylene, 2% polyvinyl chloride/polyethylene blend, 5% polystyrene, 

1% high dentistry polyethylene, 1% low density polyethylene, and 1% unknown. Sample 2 

contained 64% polyethylene, 15% polypropylene, 3% polyvinyl chloride/polyethylene blend, 

10% polyvinyl chloride, 2% polyethylene, and 6% unknown. Overall, 8 of the total 282 pieces 

were not identified as a standard polymer using FTIR analysis. 

Reporting Units 

The end result of these techniques is an estimated mass of microplastic in a given matrix. 

Depending on study objectives, a number of reporting units might be useful. 

You may want to understand how the microplastic concentration compares to the other natural 

materials within the specified size range. Compare the amount of microplastic to the total 

amount of dried material within the specific size range by using: 

[(g microplastic) / (g total solids)] 

You may want to understand regional or temporal trends and make comparisons among sampling 

sites. Compare the amount of microplastic across samples by using: 

[(g microplastic) / (mL matrix)] 

where matrix is the volume of water, sand, or sediment processed to obtain a sample. For 

example, use the volume of water filtered during a single surface water trawl or the amount of 

sediment captured in a Ponar grab. 

Lastly, you may want to understand how your samples compare to historic samples, or how the 

microplastic particles are distributed over a certain area. For these comparisons, use: 

[(g microplastic) / (m2 

matrix)]. 

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Laboratory Methods for the Analysis of Microplastics 

31 | P a g e 
Penny Pritzker
 

United States Secretary of Commerce
 

Dr. Kathryn D. Sullivan
 

NOAA Administrator and Under Secretary of Commerce for Oceans and Atmosphere
 

Dr. Russell Callender
 

Acting Assistant Administrator, National Ocean Service