ASTM D4638-03(2007)
(Guide)Standard Guide for Preparation of Biological Samples for Inorganic Chemical Analysis
Standard Guide for Preparation of Biological Samples for Inorganic Chemical Analysis
SIGNIFICANCE AND USE
The chemical analysis of biological material, collected from such locations as streams, rivers, lakes, and oceans can provide information of environmental significance. The chemical analysis of biological material used in toxicity tests may be useful to better interpret the toxicological results.
Many aquatic biological samples, either as a result of their size, or their method of collection, are inherently heterogeneous in that they may contain occluded water in varying and unpredictable amounts and may contain foreign objects or material (for example, sediment) not ordinarily intended for analysis, the inclusion of which would result in inaccurate analysis.
Standard methods for separating foreign objects, to facilitate homogenization, will minimize errors due to poor mixing and inclusion of extraneous material.
Standardized procedures for drying provide a means for reporting analytical values to a common dry weight basis, if desired. Analyses may also be carried out or reported on a wet weight basis.
SCOPE
1.1 This guide describes procedures for the preparation of test samples collected from such locations as streams, rivers, ponds, lakes, estuaries, oceans, and toxicity tests and is applicable to such organisms as plankton, mollusks, fish, and plants.
1.2 The procedures are applicable to the determination of volatile, semivolatile, and nonvolatile inorganic constituents of biological materials. Analyses may be carried out or reported on either a dry or wet basis.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For a specific hazard statement, see 9.3.3.
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Designation:D4638–03 (Reapproved 2007)
Standard Guide for
Preparation of Biological Samples for Inorganic Chemical
Analysis
This standard is issued under the fixed designation D4638; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* 4.2 Before analysis, samples are allowed to return to room
temperature. Large foreign objects are mechanically removed
1.1 This guide describes procedures for the preparation of
from the samples based upon visual examination; smaller
test samples collected from such locations as streams, rivers,
foreign objects are also removed mechanically, with the aid of
ponds, lakes, estuaries, oceans, and toxicity tests and is
a low-power microscope.
applicable to such organisms as plankton, mollusks, fish, and
4.3 Wet samples of small organisms such as plankton, are
plants.
mixed for preliminary homogenization, then allowed to settle,
1.2 The procedures are applicable to the determination of
to remove most of the occluded water. Larger organisms, such
volatile, semivolatile, and nonvolatile inorganic constituents of
as fish, should be patted dry, using paper towels.
biological materials. Analyses may be carried out or reported
4.4 Where less than a whole organism is to be analyzed,
on either a dry or wet basis.
tissueexcisionsaremadewithnonmetallictoolssuchasplastic
1.3 This standard does not purport to address all of the
knives or TFE-fluorocarbon-coated scalpels.
safety concerns, if any, associated with its use. It is the
4.5 Moisture determinations are made on separate samples
responsibility of the user of this standard to establish appro-
from those analyzed for volatile or semivolatile constituents.
priate safety and health practices and determine the applica-
4.6 Analyses for volatile constituents are made using wet
bility of regulatory limitations prior to use. For a specific
samples from which supernatant liquid or occluded water has
hazard statement, see 9.3.3.
been removed (see 4.3). The results may be calculated to the
2. Referenced Documents dry, original-sample basis, using the results of a moisture
determination carried out on a separate sample.
2.1 ASTM Standards:
4.7 Analyses for semivolatile constituents are made on wet
D1129 Terminology Relating to Water
samples or samples previously dried at a temperature (depen-
D1193 Specification for Reagent Water
dent on constituents of interest), or using a procedure, found to
3. Terminology
be adequate for the purpose, and specified in the corresponding
analytical procedure.
3.1 Definitions—For definitions of terms used in this guide,
4.8 Analyses for nonvolatile constituents are made on
refer to Terminology D1129.
samples previously dried at a temperature (dependent on
4. Summary of Guide
constituents of interest), or using a procedure found to be
adequate for the purpose, and specified in the corresponding
4.1 Samples are collected, where possible, with nonmetallic
analytical procedure.
or TFE-fluorocarbon-coated sampling equipment to prevent
4.9 Digest the samples according to the procedures outlined
contamination, stored in plastic containers, and kept either at
in Section 9.
4°Corfrozenuntilreturnedtoanadequatefacilityforanalysis.
4.10 A flow diagram outlining typical procedures is shown
in Fig. 1.
This guide is under the jurisdiction ofASTM Committee D19 on Water and is
the direct responsibility of Subcommittee D19.05 on Inorganic Constituents in
5. Significance and Use
Water.
5.1 The chemical analysis of biological material, collected
Current edition approved Dec. 1, 2007. Published January 2008. Originally
approved in 1986. Last previous edition approved in 2003 as D4638 – 03. DOI:
from such locations as streams, rivers, lakes, and oceans can
10.1520/D4638-03R07.
provide information of environmental significance.The chemi-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
cal analysis of biological material used in toxicity tests may be
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
useful to better interpret the toxicological results.
the ASTM website.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D4638–03 (2007)
FIG. 1 Flow Diagram for the Preparation of Biological Samples for Inorganic Analysis
5.2 Many aquatic biological samples, either as a result of number of small portions (at least five) from random locations
their size, or their method of collection, are inherently hetero- in the beaker, and composite them to obtain a representative
geneous in that they may contain occluded water in varying sample of a size sufficient for chemical analysis and a separate
and unpredictable amounts and may contain foreign objects or moisture determination. Using a tissue disrupter, blender, or
material (for example, sediment) not ordinarily intended for equivalent, homogenize the sample or composite (to ensure
analysis, the inclusion of which would result in inaccurate lack of contamination, carry a standard or blank, or both,
analysis.
through this procedure). Remove a subsample for moisture
5.3 Standard methods for separating foreign objects, to
determination and proceed to Section 7. Retain the remainder
facilitate homogenization, will minimize errors due to poor
and proceed to Section 9.
mixing and inclusion of extraneous material.
6.1.5 If chemical analyses are to be carried out on a dry
5.4 Standardized procedures for drying provide a means for
sample, and a large amount of material is available, remove a
reporting analytical values to a common dry weight basis, if
number of small portions (at least five) from random locations
desired.Analyses may also be carried out or reported on a wet
in the beaker, and composite them to obtain a representative
weight basis.
sample of a size sufficient for the analysis. Using a tissue
disrupter, blender, or equivalent, homogenize the sample, or
6. Preliminary Treatment of Samples
composite (to ensure lack of contamination, carry a standard or
6.1 Treat small heterogeneous samples, such as plankton, as
blank, or both, through this procedure), and proceed to Section
follows:
7.
6.1.1 Allow for the sample to return to room temperature.
6.2 Treat large samples such as fish as follows:
6.1.2 Remove foreign objects, such as leaves and twigs,
6.2.1 Allow the sample to return to room temperature.
mechanically, using nonmetallic instruments. Use a low-power
6.2.2 Pat the sample dry with paper toweling to remove as
microscope to facilitate removal of smaller foreign objects
much water as possible.
such as paint chips.
6.1.3 Transfer the sample to a beaker and thoroughly mix it 6.2.3 Transfer the sample to a nonmetallic surface, such as
with a glass stirring rod or equivalent, and allow it to settle so a flat glass plate, and excise a sufficient quantity of material, or
that most or all of the occluded water can be decanted. specific organs, to obtain sufficient material for analysis. Make
6.1.4 If chemical analyses are to be carried out on a wet excisions with plastic knives or TFE-fluorocarbon-coated scal-
sample, and a large amount of material is available, remove a pels.
D4638–03 (2007)
6.2.4 If chemical analyses are to be carried out on a wet 7.5.1.2 Leave the material in the desiccator for 48 h, then
sample, use a tissue disrupter, blender, or equivalent, to weigh the dried samples with the same accuracy as the wet
homogenize the material (to ensure lack of contamination, sample.
carry a standard or blank, or both, through this procedure).
7.5.1.3 Repeat weighings at 4-h intervals, to attain a con-
Remove a subsample for moisture determination and proceed
stant weight (see Note 1).
to Section 7. Retain the remainder and proceed to Section 9.
7.5.2 Alternatively, sample drying or moisture determina-
6.2.5 If chemical analyses are to be carried out on a dry
tions may be carried out in a laminar flow hood; treat as
sample, use a tissue disrupter, blender, or equivalent, to
follows:
homogenize the material (to ensure lack of contamination,
7.5.2.1 Transfer the containers holding the material to an
carry a standard or blank, or both, through this procedure) and
appropriate hood and turn it on.
proceed to Section 7.
7.5.2.2 Leave the material in the hood for 48 h, then weigh
the dried samples with the same accuracy as the wet sample.
7. Drying Procedures
7.5.2.3 Repeat weighings at 4-h intervals, to attain a con-
7.1 Use a sample or subsample prepared in accordance with
stant weight (see Note 1).
the directions given in Section 6.
NOTE 3—Air-drying in the open is strongly discouraged unless it is
7.2 Treat subsamples from biological materials that are to
carried out in a clean room, where possible contamination from airborne
undergo chemical analysis without drying for moisture deter-
particulates can be controlled.
minations as follows:
7.6 If a moisture determination (or sample drying) is to be
7.2.1 Accurately weigh 5 to 10 g 61mgor10to25g 6
made using a freeze dryer, treat the determination as follows:
10 mg of material into a nonmetallic container which has been
previously tared, and weighed with the same accuracy.
7.6.1 Transfer the containers holding the material to the
7.2.2 When a limited amount of material is available,
freeze dryer.
determinethemoistureona1to2-gsample,andweighwithan
7.6.2 Follow the manufacturer’s instructions for the particu-
accuracy of 60.1 mg. The use of samples smaller than 1 g is
lar unit in use. Make certain that a trap is placed between the
not recommended for moisture determination.
vacuum pump and the drying chamber to prevent pump oil
7.3 When an entire sample is to be dried prior to chemical
fumes from possibly contaminating the sample. Drying is
analysis,amoisturedeterminationisalsorequired.Transferthe
usually complete when the internal pressure in the drying
accurately weighed material (1 to 2 g 60.1mg,5to10g 6
chamber reaches 50 millitorrs or less.
1 mg, >10 g 6 10 mg) into a dry nonmetallic container which
7.6.3 Transfer the freeze-dried samples to a desiccator for
has been previously tared, and weigh with the same accuracy.
storage, and weigh them with the same accuracy as the wet
7.4 If a moisture determination (or sample drying) is to be
samples (see Note 1).
made using an oven, treat as follows:
NOTE 4—Because freeze drying occurs under vacuum, this may cause
7.4.1 Transferthecontainersholdingthematerialtoanoven
the loss of volatile or semivolatile inorganics such as mercury, or both, if
anddryfor2hatoneofthe following temperatures:
the dried sample is to be subjected to chemical analysis.
7.4.1.1 For the determination of semivolatile constituents,
usethetemperaturespecifiedintheanalyticalprocedureforthe 7.7 The possibility of loss of volatile constituents dictates
the drying procedure to be used, prior to chemical analysis.
constituents(s).
7.4.1.2 For determination of nonvolatile constituents use Determine volatile constituents using undried samples. Deter-
mine semivolatile constituents using samples dried at a tem-
105 6 2°C.
7.4.2 Cool in a desiccator, then weigh the dried samples perature at which no significant losses occur.
with the same accuracy as the wet samples.
7.8 Analytical data reported on a dry weight basis should
include percent moisture so that wet weight values can be
NOTE 1—Biological materials tend to be very hygroscopic. Keep
obtained. Likewise, wet weight analytical data should include
weighing times to a minimum.
percent moisture to permit recalculation to a dry weight basis.
7.4.3 Repeat drying at hourly intervals, to attain a constant
7.9 Use the following equations to calculate percent mois-
weight.
ture and to correct analytical results from samples analyzed
7.5 If a moisture determination (or sample drying) is to be
when wet.
made at room temperature, treat as follows:
7.9.1 Calculate percent moisture as follows:
7.5.1 If drying is to be done in a desiccator, ensure that the
moisture, % 5 ~W /W !100 (1)
w d
desiccantinthebottomisfresh,andsomemeansisavailableto
indicate when the desiccant loses its drying capacity (for
where:
example, color change). A vacuum desiccator may also be
W = wet weight, g, and
w
used.
W = dry weight, g
d
NOTE 2—If a vacuum desiccator is used, bear in mind that this may 7.9.2 To calculate concentrations on a dry weight basis,
cause the loss of volatile or semivolatile inorganics such as mercury, if the
when determinations have been made on an undried sample,
dried sample is to be subjected to chemical analysis.
use the following equation:
7.5.1.1 Transfer the containers holding the material to a C 100!
~
w
C 5 (2)
d
desiccator. 100 2 % moisture
D4638–03 (2007)
consult the pertinent literature to determine the utility and
where:
applicability of any method, prior to a final selection. Even
C = concentration on a dry weight basis, and
d
then, experience with a particular sample type or digestion
C = concentration on a wet weight basis.
w
apparatus, or both, may have to be the final arbiter in method
8. Reagents
selection.
8.1 Purity of Reagents—Reagent grade chemicals shall be
NOTE 5—Contradictory reports, regarding recoveries for various pro-
, , ,
used in all tests. Unless otherwise indicated, it is intended that 4 5 6 7
cedures, can be found in the following literature.
all reagents conform to the specifications of the Committee on
9.2 Dry ashing entails procedures in which organic matter
Analytical Reagents of the American Chemical Society where
is oxidized by reaction with gaseous oxygen, generally with the
such specifications are available. Other grades may be used,
application of energy in some form. Included in this general
provided it is first ascertained that the reagent is of sufficiently
term are the methods in which the sample is heated to a
high purity to permit its use without lessening the accuracy of
relatively high temperature in a stream of air or oxygen and the
the determination.
related low-temperature technique where excited oxygen is
8.2 Purity of Water—Unless otherwise indicated, references
used.
towatershallbeunderstoodtomeanreagentwaterconforming
9.2.1 For high temperature ashing, digest as follows:
to Specification D1193, Type I. Other reagent water types may
9.2.1.1 Place a weighed 2 to 10-g sample, prepared accord-
be used, provided it is fir
...
This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:D 4638–95a (Reapproved 1999) Designation: D 4638 – 03 (Reapproved
2007)
Standard Guide for
Preparation of Biological Samples for Inorganic Chemical
Analysis
This standard is issued under the fixed designation D 4638; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 This guide describes procedures for the preparation of test samples collected from such locations as streams, rivers, ponds,
lakes, estuaries, oceans, and toxicity tests and is applicable to such organisms as plankton, mollusks, fish, and plants.
1.2 The procedures are applicable to the determination of volatile, semivolatile, and nonvolatile inorganic constituents of
biological materials. Analyses may be carried out or reported on either a dry or wet basis.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use. For a specific hazard statement, see 9.3.3.
2. Referenced Documents
2.1 ASTM Standards:
D 1129 Terminology Relating to Water
D 1193 Specification for Reagent Water
3. Terminology
3.1 Definitions—For definitions of terms used in this guide, refer to Terminology D 1129.
4. Summary of Guide
4.1 Samples are collected, where possible, with nonmetallic or TFE-fluorocarbon-coated sampling equipment to prevent
contamination, stored in plastic containers, and kept either at 4°C or frozen until returned to an adequate facility for analysis.
4.2 Before analysis, samples are allowed to return to room temperature. Large foreign objects are mechanically removed from
the samples based upon visual examination; smaller foreign objects are also removed mechanically, with the aid of a low-power
microscope.
4.3 Wet samples of small organisms such as plankton, are mixed for preliminary homogenization, then allowed to settle, to
remove most of the occluded water. Larger organisms, such as fish, should be patted dry, using paper towels.
4.4 Where less than a whole organism is to be analyzed, tissue excisions are made with nonmetallic tools such as plastic knives
or TFE-fluorocarbon-coated scalpels.
4.5 Moisture determinations are made on separate samples from those analyzed for volatile or semivolatile constituents.
4.6 Analyses for volatile constituents are made using wet samples from which supernatant liquid or occluded water has been
removed (see 4.3). The results may be calculated to the dry, original-sample basis, using the results of a moisture determination
carried out on a separate sample.
4.7 Analyses for semivolatile constituents are made on wet samples or samples previously dried at a temperature (dependent
on constituents of interest), or using a procedure, found to be adequate for the purpose, and specified in the corresponding
analytical procedure.
4.8 Analyses for nonvolatile constituents are made on samples previously dried at a temperature (dependent on constituents of
interest), or using a procedure found to be adequate for the purpose, and specified in the corresponding analytical procedure.
4.9 Digest the samples according to the procedures outlined in Section 9.
4.10 A flow diagram outlining typical procedures is shown in Fig. 1.
This guide is under the jurisdiction ofASTM Committee D-19D19 onWater and is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents inWater.
Current edition approved Dec. 10, 1995.1, 2007. Published February 1996.January 2008. Originally published as D4638–86.approved in 1986. Last previous edition
D4638–95.approved in 2003 as D 4638 – 03.
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
, Vol 11.01.volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 4638 – 03 (2007)
FIG. 1 Flow Diagram for the Preparation of Biological Samples for Inorganic Analysis
5. Significance and Use
5.1 The chemical analysis of biological material, collected from such locations as streams, rivers, lakes, and oceans can provide
information of environmental significance. The chemical analysis of biological material used in toxicity tests may be useful to
better interpret the toxicological results.
5.2 Many aquatic biological samples, either as a result of their size, or their method of collection, are inherently heterogeneous
in that they may contain occluded water in varying and unpredictable amounts and may contain foreign objects or material (for
example, sediment) not ordinarily intended for analysis, the inclusion of which would result in inaccurate analysis.
5.3 Standard methods for separating foreign objects, to facilitate homogenization, will minimize errors due to poor mixing and
inclusion of extraneous material.
5.4 Standardizedproceduresfordryingprovideameansforreportinganalyticalvaluestoacommondryweightbasis,ifdesired.
Analyses may also be carried out or reported on a wet weight basis.
6. Preliminary Treatment of Samples
6.1 Treat small heterogeneous samples, such as plankton, as follows:
6.1.1 Allow for the sample to return to room temperature.
6.1.2 Remove foreign objects, such as leaves and twigs, mechanically, using nonmetallic instruments. Use a low-power
microscope to facilitate removal of smaller foreign objects such as paint chips.
6.1.3 Transfer the sample to a beaker and thoroughly mix it with a glass stirring rod or equivalent, and allow it to settle so that
most or all of the occluded water can be decanted.
6.1.4 If chemical analyses are to be carried out on a wet sample, and a large amount of material is available, remove a number
of small portions (at least 5)five) from random locations in the beaker, and composite them to obtain a representative sample of
a size sufficient for chemical analysis and a separate moisture determination. Using a tissue disrupter, blender, or equivalent,
homogenize the sample or composite (to ensure lack of contamination, carry a standard or blank, or both, through this procedure).
Remove a subsample for moisture determination and proceed to Section 7. Retain the remainder and proceed to Section 9.
6.1.5 If chemical analyses are to be carried out on a dry sample, and a large amount of material is available, remove a number
of small portions (at least 5)five) from random locations in the beaker, and composite them to obtain a representative sample of
a size sufficient for the analysis. Using a tissue disrupter, blender, or equivalent, homogenize the sample, or composite (to ensure
lack of contamination, carry a standard or blank, or both, through this procedure), and proceed to Section 7.
D 4638 – 03 (2007)
6.2 Treat large samples such as fish as follows:
6.2.1 Allow the sample to return to room temperature.
6.2.2 Pat the sample dry with paper toweling to remove as much water as possible.
6.2.3 Transfer the sample to a nonmetallic surface, such as a flat glass plate, and excise a sufficient quantity of material, or
specific organs, to obtain sufficient material for analysis. Make excisions with plastic knives or TFE-fluorocarbon-coated scalpels.
6.2.4 If chemical analyses are to be carried out on a wet sample, use a tissue disrupter, blender, or equivalent, to homogenize
the material (to ensure lack of contamination, carry a standard or blank, or both, through this procedure). Remove a subsample
for moisture determination and proceed to Section 7. Retain the remainder and proceed to Section 9.
6.2.5 If chemical analyses are to be carried out on a dry sample, use a tissue disrupter, blender, or equivalent, to homogenize
the material (to ensure lack of contamination, carry a standard or blank, or both, through this procedure) and proceed to Section
7.
7. Drying Procedures
7.1 Use a sample or subsample prepared in accordance with the directions given in Section 6.
7.2 Treat subsamples from biological materials whichthat are to undergo chemical analysis without drying for moisture
determinations as follows:
7.2.1 Accurately weigh 5 to 10 g 61mgor10to25g 6 10 mg of material into a nonmetallic container which has been
previously tared, and weighed with the same accuracy.
7.2.2 When a limited amount of material is available, determine the moisture ona1to2-g sample, and weigh with an accuracy
of 60.1 mg. The use of samples smaller than1gisnot recommended for moisture determination.
7.3 When an entire sample is to be dried prior to chemical analysis, a moisture determination is also required. Transfer the
accurately weighed material (1 to 2 g 60.1mg,5to10g 6 1 mg, >10 g 6 10 mg) into a dry nonmetallic container which has
been previously tared, and weigh with the same accuracy.
7.4 If a moisture determination (or sample drying) is to be made using an oven, treat as follows:
7.4.1 Transfer the containers holding the material to an oven and dry for2hatoneofthe following temperatures:
7.4.1.1 For the determination of semivolatile constituents, use the temperature specified in the analytical procedure for the
constituents(s).
7.4.1.2 For determination of nonvolatile constituents use 105 6 2°C.
7.4.2 Cool in a desiccator, then weigh the dried samples with the same accuracy as the wet samples.
NOTE 1—Biological materials tend to be very hygroscopic. Keep weighing times to a minimum.
7.4.3 Repeat drying at hourly intervals, to attain a constant weight.
7.5 If a moisture determination (or sample drying) is to be made at room temperature, treat as follows:
7.5.1 If drying is to be done in a desiccator, ensure that the desiccant in the bottom is fresh, and some means is available to
indicate when the desiccant loses its drying capacity (for example, color change). A vacuum desiccator may also be used.
NOTE 2—If a vacuum desiccator is used, bear in mind that this may cause the loss of volatile or semivolatile inorganics such as mercury, if the dried
sample is to be subjected to chemical analysis.
7.5.1.1 Transfer the containers holding the material to a desiccator.
7.5.1.2 Leave the material in the desiccator for 48 h, then weigh the dried samples with the same accuracy as the wet sample.
7.5.1.3 Repeat weighings at 4-h intervals, to attain a constant weight (see Note 1).
7.5.2 Alternatively, sample drying or moisture determinations may be carried out in a laminar flow hood; treat as follows:
7.5.2.1 Transfer the containers holding the material to an appropriate hood and turn it on.
7.5.2.2 Leave the material in the hood for 48 h, then weigh the dried samples with the same accuracy as the wet sample.
7.5.2.3 Repeat weighings at 4-h intervals, to attain a constant weight (see Note 1).
NOTE 3—Air-dryingintheopenisstronglydiscouragedunlessitiscarriedoutinacleanroom,wherepossiblecontaminationfromairborneparticulates
can be controlled.
7.6 If a moisture determination (or sample drying) is to be made using a freeze dryer, treat the determination as follows:
7.6.1 Transfer the containers holding the material to the freeze dryer.
7.6.2 Followthemanufacturer’sinstructionsfortheparticularunitinuse.Makecertainthatatrapisplacedbetweenthevacuum
pump and the drying chamber to prevent pump oil fumes from possibly contaminating the sample. Drying is usually complete
when the internal pressure in the drying chamber reaches 50 millitorrs or less.
7.6.3 Transfer the freeze-dried samples to a desiccator for storage, and weigh them with the same accuracy as the wet samples
(see Note 1).
NOTE 4—Because freeze drying occurs under vacuum, this may cause the loss of volatile or semivolatile inorganics such as mercury, or both, if the
dried sample is to be subjected to chemical analysis.
7.7 Thepossibilityoflossofvolatileconstituentsdictatesthedryingproceduretobeused,priortochemicalanalysis.Determine
volatile constituents using undried samples. Determine semivolatile constituents using samples dried at a temperature at which no
significant losses occur.
D 4638 – 03 (2007)
7.8 Analytical data reported on a dry weight basis should include percent moisture so that wet weight values can be obtained.
Likewise, wet weight analytical data should include percent moisture to permit recalculation to a dry weight basis.
7.9 Use the following equations to calculate percent moisture and to correct analytical results from samples analyzed when wet.
7.9.1 Calculate percent moisture as follows:
moisture, % 5 ~W /W !100 (1)
w d
where:
W = wet weight, g, and
w
W = dry weight, g
d
7.9.2 To calculate concentrations on a dry weight basis, when determinations have been made on an undried sample, use the
following equation:
C ~100!
w
C 5 (2)
d
100 2 % moisture
where:
C = concentration on a dry weight basis, and
d
C = concentration on a wet weight basis.
w
8. Reagents
8.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where such
specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity
to permit its use without lessening the accuracy of the determination.
8.2 Purity of Water— Unless otherwise indicated, references to water shall be understood to mean reagent water conforming
to Specification D 1193, Type I. Other reagent water types may be used, provided it is first ascertained that the water is of
sufficiently high purity to permit its use without adversely affecting the bias and precision of the test method. Type II water was
specified at the time of round robin testing of this method.
8.3 All of the following reagents may not be required for a particular procedure. Check the digestion procedure(s) of interest
(Section 9) prior to preparing any reagents.
8.3.1 Amyl Alcohol.
8.3.2 Hydrochloric Acid (1+1)—Mix 1one volume of hydrochloric acid (HCl, sp gr 1.19) with 1one vo
...
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