**2. Literature survey**

The literature was surveyed through 2020 in PubMed, Web of Science and other commercial sources to identify published sample preparation and storage information of contaminants in any environmental matrix. Stability of analytes in analytical standards and in stored biospecimens were not included in this review.

**Table 1** summarizes the 63 peer-reviewed articles and 8 reports and book chapters selected after initial screening that discussed stability of anthropogenic chemical compounds in environmental matrices. The most common analytes studied were pesticides and trace elements. Various environmental matrices were considered, including air, water, soil/sediment, dust, and food (plant and animal tissue).

Two major scopes for stability studies were identified: (1) long-term stability in storage (retained samples, environmental specimen banking), and (2) short-term stability of samples in transport conditions. There was no generally accepted procedure for performing a stability study. Stability samples were sometimes prepared and stored all at the same time with some samples removed for analysis at various time periods. Alternatively, samples were prepared and stored at different time points and analyzed all at the same time. The former procedure is subject to dayto-day and longer term variability and changes in analysis procedures; the latter is subject to variability and changes in the preparation and analysis procedures when the time points are far apart.

Another sample stability test procedure, generally used for reference standards and sample transport, is isochronous testing, where samples are prepared at the same time and stored in conditions that offer the best stability, or the least degradation, until they are moved to the storage conditions to be tested for the specified time periods [43]. At the end of the testing period, each sample set is moved back to the original storage until all samples are removed for analysis at the same time. This procedure avoids the challenges of varying sample preparation and analysis conditions.

The determination of stability of an analyte in a sample is measured as the ratio of the concentration measured at time point t, compared to that measured at time point 0. The sample size required to make a decision with specified confidence for each analyte depends on the precision of the analysis method at each concentration level and the amount of change at which samples are considered to have degraded.

**199**

**Matrix**

Air

Endotoxin on PM filters and filter extracts Endotoxin on PM filters and in

LAL

−20°C, 4°C

14 d filters,

Filter, dessicant

24 h extracts

extracts

Cat (Fel d 1), dog (Can f 1),

Antigen-specific

RT EDC,

1.5 y

Buffer

−20°C

and − 80°C

extracts

RT

0, 1, 2, 4, 6 d

Concentration

immunoassay

mouse (Mus m 1), and mite

(DM, Der p 1, TP) allergens

Ammonia 15 volatile organic chemicals

GC-FID, GC-ECD

Not specified

7 d, 30 d

(VOC) in SUMMA canister and

sorbent tubes

2,3,3,3-tetrafluoropropene on

GC-FID

RT, frozen,

3, 7, 14, 30 d

sorbent

30 d is acceptable, analysis

[18]

within 14 d due to migration

Stable on sorbent for at least

[19]

12 d

Extract stable for at least 5 d

Unstable 2 d at RT

[21]

Stable 1 wk. at −14°C

[20]

refrigerated

4 °C

4, 12 d

sorbent

Formaldehyde, acetaldehyde on

HPLC

sorbent

Ortho-phthalaldehyde (OPA)

HPLC-MS

Extract

5 d

refrigerated

RT, 5.6,-14°C

2, 3, 11 d

on sorbent

1,2-Dibromo-3-chloropropane

GC-ECD

(DBCP), 1,3-diClpropene

(DCP) on charcoal

Volatile aliphatic and aromatic

GC (detector not

RT, −22°C

7, 14, 28 d

Sorbent

Stable at RT for Chromosorb

[22]

(except cyclohexanone), better

at −22°C for all sorbents

specified)

solvents on sorbents

Indophenol

spectrophotometry

LAL

**Analytes**

**Analysis method(s)**

**Temperature**

4 °C filters,

3 y

−20°C extracts

**Time**

**Other**

**Storage conditions**

**Results** Stored well both in extract and

[12]

on filter

Store both filters and extracts

[13]

frozen

EDC 4.8% loss Can f 1 every

30 d, extracts −20°C 1.2% loss

DM every 30 d, extract with

Tween

Loss 10–17% at 1 d, 40–64%

[15]

at 6 d, depending on

concentration

Suitable for compounds tested

[16, 17]

**References**

*Considerations for Stability of Environmental Samples in Storage for Long-Term Studies*

*DOI: http://dx.doi.org/10.5772/intechopen.97445*

[14]


#### *Considerations for Stability of Environmental Samples in Storage for Long-Term Studies DOI: http://dx.doi.org/10.5772/intechopen.97445*

*Analytical Chemistry - Advancement, Perspectives and Applications*

children included in subsequent case–control studies.

**2. Literature survey**

the time points are far apart.

The National Children's Study (NCS) was a longitudinal cohort study that aimed to follow 100,000 children from birth until 21 years of age to evaluate the health effects of environmental exposures, including chemical, physical, biological, and psychosocial factors. A variety of different types of samples were collected during the NCS pilot study including environmental samples and biospecimens. The environmental samples that could not be stored because of known instability (e.g., badge samples for air oxidants) were analyzed immediately after collection. Other samples and biospecimens were stored in the NCS repository. The plan was to store the other environmental samples (e.g., water, soil, and dust) and biospecimens (e.g., blood, urine) until children aged, analyzing only samples as requisitioned for

As part of the NCS pilot, we considered which types of environmental samples could be stored for extended periods of time. Many factors can affect stability of chemical compounds in stored environmental samples over time, such as temperature, humidity, pH, and microbial enzymatic activity of the sample matrix, physicochemical properties of the analytes themselves and their reactions with the

The literature was surveyed through 2020 in PubMed, Web of Science and other commercial sources to identify published sample preparation and storage information of contaminants in any environmental matrix. Stability of analytes in analyti-

**Table 1** summarizes the 63 peer-reviewed articles and 8 reports and book chapters selected after initial screening that discussed stability of anthropogenic chemical compounds in environmental matrices. The most common analytes studied were pesticides and trace elements. Various environmental matrices were considered, including air, water, soil/sediment, dust, and food (plant and animal tissue).

Two major scopes for stability studies were identified: (1) long-term stability in storage (retained samples, environmental specimen banking), and (2) short-term stability of samples in transport conditions. There was no generally accepted procedure for performing a stability study. Stability samples were sometimes prepared and stored all at the same time with some samples removed for analysis at various time periods. Alternatively, samples were prepared and stored at different time points and analyzed all at the same time. The former procedure is subject to dayto-day and longer term variability and changes in analysis procedures; the latter is subject to variability and changes in the preparation and analysis procedures when

Another sample stability test procedure, generally used for reference standards and sample transport, is isochronous testing, where samples are prepared at the same time and stored in conditions that offer the best stability, or the least degradation, until they are moved to the storage conditions to be tested for the specified time periods [43]. At the end of the testing period, each sample set is moved back to the original storage until all samples are removed for analysis at the same time. This procedure avoids the challenges of varying sample preparation and analysis

The determination of stability of an analyte in a sample is measured as the ratio of the concentration measured at time point t, compared to that measured at time point 0. The sample size required to make a decision with specified confidence for each analyte depends on the precision of the analysis method at each concentration level and the amount of change at which samples are considered to have degraded.

matrix, container materials, and other analytes present in the sample [11].

cal standards and in stored biospecimens were not included in this review.

**198**

conditions.


**201**

**Matrix**

**Analytes** Benzo[a]pyrene on quartz filter

25 PAHs on PM filters and in extracts Organic solvents on charcoal (ketones, esters, alcohols, aromatic hydrocarbons)

GC-FID/MS

20 °C

1, 2, 4 wk

Carbon sorbent, water, hydroquinone rinse

Unstable: Esters, alcohols, cyclic & aliphatic ketones loss dramatic, more pronounced on one carbon

 Stable: Toluene, butanol, DMF, styrene, 111-TCA, ethyl acetate

Water adsorption affected

recovery differently on two

carbons

Hydroquinone rinse partly

effective in improving recovery

Stable on ABN Express

[32]

sorbent, 367–62% loss on

ENV+ sorbent

Average loss 9–14%

[33]

Cyclic volatile methylsiloxanes

GC–MS

−20°C

14 d

Sorbent type

(cVMS)

30 pharmaceuticals, pesticides

Not specified

Freezer

o-DGT 18 mo

Sampler type

POCIS 6 yr

on organic-diffusive gradients

in thin-films (o-DGT) passive

sampler and the polar organic

chemical integrative sampler

(POCIS)

GC–MS-SIM

4°C

7, 30 d filters, 1,5,6 mo extracts

HPLC

**Analysis method(s)**

**Temperature**

−20°C, 20°C

0.5,1,2,4,12 yr

In air, argon

−20°C: Stable for 6 mo, 12% loss at 12 yr. 20°C: Unstable, 50% loss at 12 yr. No effect air vs. argon

[29]

**Time**

**Other**

**Storage conditions**

**Results**

**References**

*Considerations for Stability of Environmental Samples in Storage for Long-Term Studies*

*DOI: http://dx.doi.org/10.5772/intechopen.97445*

[30]

Filters can be stored for 1 mo, extracts for 1 mo, hopanes and steranes for 5 mo

[31]

#### *Analytical Chemistry - Advancement, Perspectives and Applications*


*Considerations for Stability of Environmental Samples in Storage for Long-Term Studies DOI: http://dx.doi.org/10.5772/intechopen.97445*

*Analytical Chemistry - Advancement, Perspectives and Applications*

**200**

**Matrix**

**Analytes** Ketones on carbon sorbents

4-vinyl-1-cyclohexene on

GC-FID

RT (27–29 °C),

21 d

4–6 °C

charcoal

94 VOC (including terpenes,

TD/GC–MS-SIM

4°C

1 mo

aromatic, halogenated, and

aliphatic compounds) on Tenax

GR sorbent

Hazardous air pollutants (HAPs)

Varied: GC-FID,

RT

Varied:

Stable: 52 HAPs

[26]

Likely stable: 9 HAPs

Likely unstable: 17 HAPs

Unknown: 19 HAPs

SVOCs stable in amber vials,

[27]

PAHs mostly stable (monsubstituted phenols more affected by temperature),

Half-life in clear vials 28–31

d, Constant temperature

more important than absolute

temperature

Stable: All at −20°C

[28]

Stable PUF, RT: PAH

Unstable PUF, RT:

naphthalene, anthracene,

benzo-a-pyrene

Stable quartz filter, RT: All but

cyclopenta[c,d]

pyrene

Stable XAD2, RT: All but

2,3-nitrofluoranthrene

generally 7–14

d, up to 35 d

GC-ECD

in canisters – review of literature

*(applicable* 

56 SVOCs (amines, halo

GC–MS

Extract

53 days

Vial color (light),

fluctuating

temperature

purified for

analysis:

−20°C, 4°C,

22°C

ethers, nitrobenzenes, phenols,

phthalate esters, polycyclic

aromatic hydrocarbons and

chlorinated compounds)

Polycyclic aromatic

Ref provided

Room

10, 20, 30 d

Sorbent, filter

temperature,

−20°C

hydrocarbons (PAH) on

sorbents (XAD2, PYF) and

quartz fiber filter

*to other* 

*matrices)*

GC (detector not

specified)

**Analysis method(s)**

**Temperature**

RT, 4°C

1, 7, 30 d

Sorbent, water

Stable 7 days on Anasorb, 30 d

[23]

on Carboxen 564,

except cyclohexanone

Stable 7 days at RT, 21 days

[24]

refrigerated

Stable 1 mo: 87 compounds

[25]

vapor

**Time**

**Other**

**Storage conditions**

**Results**

**References**


**203**

**Matrix**

**Analytes** Pharmaceuticals and pesticides

21 organochlorine pesticides on solid-phase extraction (SPE) disks

12 pesticides 9 pesticides 8 phenylurea pesticides

10 pesticides 9 organophosphate pesticides

10 pesticides, 3 atrazine

LC-APCI-MS,

−20°C, 4°C, RT

1 wk., 3 mo

In SPE

Recovery>90% after storage

[52]

for 3 mo at −20°C

Variability due to complexity

[53]

of matrix

In SPE 6 wk. frozen, otherwise

[54]

5 d

Best 60 d at −20°C in dark

[55]

LC-DAD

HPLC-UV

4 °C

14 d, 30 d

metabolites

Isoproturon, bentazone,

terbuthylazine, alachlor

OP, OC pesticides, pyrethroids,

GC-ECD

−17°C, 3°C

2,5,8,14,21,28,

In SPE, pH

39 d

carbamates

18 herbicides Phenoxyacid herbicides

LC-DAD-MS

20°C

LC-APCI-MS

−20°C, 4°C,

30 d, 60 d

In SPE Water type, bottle

Half-life river water ~20 d in

[56]

light, 34–50 d in dark storage;

seawater has shorter half-life

type

20°C

GC-NPD

−20 °C, 4°C,

60 d

In SPE, drying

60 d at −20°C in dark

[51]

20°C

GC-NPD

HPLC GC-MSD

6°C, RT

21 d

6 °C

21 d

preservatives In SPE, pH,

additives

−18°C

119, 319 d

In SPE

119 d recovery 53–155%

21 day storage is ok

14 d storage with additives

[50]

[48]

GC-ECD, HPLC-UV

−20°C, 4°C

3, 30, 90, 180 d

In SPE

LC–MS/MS-SRM

GC-ECD

−18°C, 4°C

3, 14. 30 d

Sodium azide addition

**Analysis method(s)**

**Temperature**

4°C

21 d

**Time**

**Other**

**Storage conditions**

**Results** Steroidal hormones 3 d, others 21 d ok

[45] [46]

**References**

*Considerations for Stability of Environmental Samples in Storage for Long-Term Studies*

[49]

*DOI: http://dx.doi.org/10.5772/intechopen.97445*

Stable for at least 30 days at both temperatures, slight improvement for some analytes with sodium azide addition

Losses in storage for 90 and 180 d storage

[47]

#### *Analytical Chemistry - Advancement, Perspectives and Applications*


#### *Considerations for Stability of Environmental Samples in Storage for Long-Term Studies DOI: http://dx.doi.org/10.5772/intechopen.97445*

*Analytical Chemistry - Advancement, Perspectives and Applications*

[38]

**202**

**Matrix**

**Analytes** 14 Personal care products

Water

As(III), As(V) As(III), As(V)

As, Se, Sb, Te Inorganic Hg, labeled with 197Hg

Perchlorate 44 VOC in wastewater samples

18 bisphenols in wastewater

29 PFAS Polar pharmaceuticals,

LC–MS/MS

4°C, 20°C,

6 wk

40°C

pesticides, PFOS, PFOA,

caffeine, PBA

24 pharmaceuticals, pesticides

LC–MS/MS

−20°C

20 mo

In POCIS, in SPE

Small statistically significant

[44]

losses, add labeled IS

LC–MS/MS

−20°C, 4°C,

180 d

Sample type

(bottled, surface,

effluent)

20°C

Not specified

−20°C, 4°C

4 wk

GC–MS

4°C

2–5 wk

Glass vials

IC, LC–MS/MS

4°C, 22°C

638 d

HPGe

5 °C, 20°C

1, 3, 6, 7, 10 d

Partitioning

Stable at least for 10 d when

acidified and stored in Teflon

or glass

300 d ground water, 90 d

[39]

surface water

Stability varies by VOC:

[40]

Methylene chloride 2 wks,

Chloroform 4 wks.

Stable for 4 weeks at either

[41]

temperature

10 analytes increased or

[42]

decreased over time, analyte

conversion observed in surface

and effluent waters

Storage for 6 wk. at 4°C

[43]

into particulate,

containers

HPLC/ICP-MS

−20°C, 3°C,

30 d

speciation

Stable at 3°C in dark

[37]

20°C

ICP-MS ICP-MS

−18°C, 6°C,

9 d

20°C

6°C

3, 18 mo

pH pH

Storage in dark, pH < 2, 3 mo

Storage in dark, 7 d at 6°C

[36]

[35]

GC–MS

**Analysis method(s)**

**Temperature**

4°C

3, 7, 14 d

On sorbent

Stable 7 d at 4°C

[34]

cartridges

**Time**

**Other**

**Storage conditions**

**Results**

**References**


**205**

**Matrix**

**Analytes** Pesticides As, Se, Sb, Te As(III), As(V), monomethylarsonic acid, dimethylarsinic acid in reducing and oxidizing soil

As species in mineral and

HPLC/ICP-MS

−20°C, 2°C

1 mo

Drying

Storage and drying changes

[68]

speciation

Unstable, freeze-dried samples

more stable than wet samples

Storage above 20 °C should be

avoided

organic soils

As, Cd, Cr, Cu, Ni, Pb, Zr

FAAS, ZETAAS

20 °C, 40°C

24 mo

> (Zeeman singlebeam AAS),

ICP-AES

ICP-MS

4 °C, RT

90, 183, 284,

Air drying

Storage at −20°C: 364 709 d

Storage for 224 d at −20°C

[16]

[16]

392 d

As, Cu, Pb, Zn

Cr(VI) Cd, Cr, Cu, Ni, Pb, Zn in

ICP-AES, ETAAS

−20°C, 4°C,

3, 6, 12, 18 mo

Sterilization

Unstable above 20°C

[70]

Sterilized samples more stable

than non-sterilized

Increase in all at 22°C due to

[70]

decreased pH

>50 d, store at −20°C or lower

Stable

[71]

20°C, 40°C

irrigation field soil

C, P, S, Al, Ba, Ca, Mg, Mn, Sr.,

ICP

−21°C, 3°C,

1842 d (5 yr)

22°C

Zn in forest soil

Hg

Cold vapor AAS

RT

10, 11, 12, 17 yr

Soil carbon

content

AAS

−20°C, 4°C

14, 28, 56, 112,

224 d

HPLC/ICP-MS HPLC/ICP-MS of extract

−20°C, 3°C

−20°C

1, 2, 3 mo

30 d

speciation Extraction solvent

Soil extracts storable 3 d at 3 °C

Extracts: MMA, DMA stable,

AsIII oxidized to AsV

[37] [67]

GC–MS

**Analysis method(s)**

**Temperature**

−20°C, 4°C

7, 14, 28, 42, 84, 168 d

**Time**

**Other**

**Storage conditions**

**Results** Storage for 299 d at −20°C

[66]

**References**

*Considerations for Stability of Environmental Samples in Storage for Long-Term Studies*

[69]

*DOI: http://dx.doi.org/10.5772/intechopen.97445*

#### *Analytical Chemistry - Advancement, Perspectives and Applications*


#### *Considerations for Stability of Environmental Samples in Storage for Long-Term Studies DOI: http://dx.doi.org/10.5772/intechopen.97445*

*Analytical Chemistry - Advancement, Perspectives and Applications*

**204**

**Matrix**

**Analytes** 65 Pharmaceuticals and drugs

Pharmaceuticals, PCPs, steroids,

LC/MS/MS

−20°C, 4°C

7, 14, 28 d

hormones

Drugs of abuse

Cocaine 3-mercaptopropionic acid,

derivatized

RDX explosive transformation

HPLC

4 °C, 23°C,

45 d

pH, salinity

40°C

products

Cat (Fel d 1) and mite (Der p 1)

ELISA

−80°C

6, 12, 18, 30 mo

allergens

Cat (Fel d 1) and mite (Der

ELISA, LAL

−20°C

10 mo

p 1, Der f 1) allergens,

β(1

→ 3)-glucan, endotoxin

181 VOCs on activated charcoal

GC

−80°C

4 wk

Concentration

cloth (ACC)

Organophosphate pesticides,

GC-ECD

−17°C, 3°C

2,5,8,14,21,28,

39 d

organochlorine pesticides,

pyrethroids, carbamates

4 OP pesticides (diazinon,

GC

2 °C, Room

8 mo

Fenamiphos: Stable

[65]

Diazinon, CPF, Malathion:

Unstable, more so at RT.

Store refrigerated or in deep

freeze.

temp

chlorpyrifos, malathion,

fenamiphos) in spiked soil

samples

Soil/

sediment

Dust/

wipes

Capillary

8 °C, 25°C,

1 wk

37°C

electrophoresis

HPLC

4°C

1, 2, 8, 52 wk

buffer

Derivatized samples can be

[60]

stored at least for 1 y.

Stable at 4 °C with 10% sea

[61]

salts

Stable in dust stored in vials

[62]

for 30 mo

Stable in dust stored on

[63]

vacuum filters stored in plastic

bags

Majority stable, exception is

[64]

n-pentane ~40% loss

1 mo frozen

[54]

GC–MS/MS

−20°C

1,3,5,7 d, 2,3,12

Preservation, SPE

wk

LC–MS/MS

**Analysis method(s)**

**Temperature**

−20°C

2, 4, 6 wk

In SPE, pH,

All analytes stored well

[57]

sample prep

Various

Stable 30 d < 6°C, with

[7]

appropriate preservatives

Stable in SPE at −20°C for at

[58]

least 3 mo

Store at 8 °C

[59]

co-contaminants

**Time**

**Other**

**Storage conditions**

**Results**

**References**


**207**

**Matrix**

**Analytes** As(III), As(V), monomethylarsonic acid, dimethylarsinic acid in rice

As species in algae

Arsenic species in marine microalgae 19 pesticides in various vegetables, fruits, grains, seeds

Animal

As, Se, Sb, Te Hg-total, Hg-org

As(III), As(V),

HPLC/ICP-MS

monomethylarsonic acid,

dimethylarsinic acid in fish and

chicken

CV-AAS

−150°C,

1 yr

−80°C, −30°C,

4°C, 25°C

−20°C

3 mo

Speciation

Extracts: Stable for 2 mo, then

[68]

AsB transformed to DMA

HPLC/ICP-MS

−20°C, 3°C

30 d

Speciation

tissue

HPLC, GC-NPD, GC-ECD

−20°C

1 yr

Hydrolysis, glass

Storage stability referred from

[79]

hydrolytic behavior:

Half-life >10 d at 70°C - stable

at least 1 y at −20°C.

Half-life <1 d: Unstable

Should be analyzed

[37]

immediately to avoid

transformations

Biobanking: stable after first

[80]

year

bottles

LC-ICP-MS

−80°C, −18°C, 4°C, RT

1, 45 d

Processing

HPLC/ICP-MS

−80°C, −18°C, 4°C, RT

1 yr

Preprocessing

Lyophilization and cryogenic grinding and storage in RT, other temp ok

[78]

Store dried at RT, non-dried at 4°C, freezing results in loss of As

**Analysis method(s)**

**Temperature**

−4°C

1, 2, 3 mo

Extraction solvent

Extracts stable at least for 3 mo.

[67]

HPLC/ICP-MS

**Time**

**Other**

**Storage conditions**

**Results**

**References**

*Considerations for Stability of Environmental Samples in Storage for Long-Term Studies*

*DOI: http://dx.doi.org/10.5772/intechopen.97445*

[77]


#### *Considerations for Stability of Environmental Samples in Storage for Long-Term Studies DOI: http://dx.doi.org/10.5772/intechopen.97445*

*Analytical Chemistry - Advancement, Perspectives and Applications*

**206**

**Matrix**

**Analytes** Methylmercury

3 PCB, 7 congeners

17 PAH 3-mercaptopropionic acid,

HPLC

4°C

1, 2, 8, 52 wk

Buffer

Derivatized samples can be

[58]

stored at least for 1 y.

Some stable for 8 mo, some

[74]

only 2 wk. at 4°C (e.g., 3-ring

PAH > degradation than 5-ring

PAH)

Sodium azide-contamination

stabilized PAH degradation

Stable in air-dried, ground

[75]

sediment in shade for 16 mo

Competitive effect on

[76]

extraction efficiency with soil

organic content and freeze–

thaw cycle

Storage and drying changes

[65]

speciation - Unstable, freezedried samples more stable than

wet samples

derivatized

13 PAH in contaminated soils

16 PAH 2 PAH (phenanthrene, pyrene)

Plant

As species in needles and mosses

HPLC/ICP-MS

−20°C, 2°C

1 mo

Drying

GC

Freeze–thaw

Extraction

Soil organic

content

efficiency at 1,

4, 8, 13, 16, 30

and 120 d

cycle (−15°C

8 h, 25°C 8 h)

GC–MS

RT < 30°C

4, 8, 12, 16 mo

HPLC-FlD

−20°C, 4°C

6 wk. frozen,

In dark, additives

8–10 mo

GC–MS

−20°C, 4°C

7, 14, 28, 42, 84,

168 d

GC-ECD

−20°C, 4°C

7, 14, 28, 42, 84,

168 d

Atomic fluorescence

detection

**Analysis method(s)**

**Temperature**

30 °C

1 hr., 1 d, 4

Drying method,

Freeze sample immediately

[72]

after collection and freeze-dry

to prevent bacterial mercury

methylation

Storage for 168 d at −20°C

Storage for 100 d at −20°C

[73]

[73]

soil type

d, 7 d

**Time**

**Other**

**Storage conditions**

**Results**

**References**

