This section applies to all the procedures. It provides background
information and reference/review material for the technician or chemist.
Commonly used techniques are explained in detail.
Section II Sample Pretreatment
This section provides a brief overview of sample pretreatment and three
digestion procedures. Two are USEPA digestions. The Hach Digesdahl
method is also included.
Section III Waste Management and Safety
Section 3 includes information an waste management, regulations, waste
disposal and resources on waste management. The Safety portion covers
reading an MSDS and general safety guidelines.
Section IV Procedures
Section 4 contains step-by-step illustrated instructions for measuring over
120 parameters. The steps also include helpful notes. Each procedure
contains information on sample collection, storage and preservation,
accuracy checks, possible interferences, summary of method and a list of
the reagents and apparatus necessary to run the test.
Section V Ordering Information
This section provides information needed for ordering, shipping, return of
items and Hach trademarks.
Before attempting the analysis procedures the analyst
should read the instrument manual to learn about the
spectrophotometer’s features and operation.
11
INTRODUCTION, continued
Hach Company Trademarks
AccuGrow
AccuVac
AccuVer™
AccuVial™
Add-A-Test™
AgriTrak™
AluVer
AmVer™
APA 6000™
AquaChek™
AquaTrend
BariVer
BODTrak™
BoroTrace™
BoroVer
C. Moore Green™
CA 610™
CalVer
ChromaVer
ColorQuik
CoolTrak
CuVer
CyaniVer
Digesdahl
DithiVer
Dr. F. Fluent™
Dr. H. Tueau™
DR/Check™
EC 310™
FerroMo
FerroVer
FerroZine
FilterTrak™ 660
Formula 2533™
Formula 2589™
Gelex
®
®
®
®
®
®
®
®
®
®
®
®
®
®
®
®
®
®
H2O University™
H2OU™
Hach Logo
Hach One
Hach Oval
Hach.com™
HachLink™
Hawkeye The Hach Guy™
HexaVer
HgEx™
HydraVer
ICE-PIC™
IncuTrol
Just Add Water™
LeadTrak
M-ColiBlue24
ManVer
MolyVer
Mug-O-Meter
NetSketcher™
NitraVer
NitriVer
NTrak
OASIS™
On Site Analysis.
Results You Can Trust
OptiQuant™
OriFlow™
OxyVer™
PathoScreen™
PbEx
PermaChem
PhosVer
Pocket Colorimeter™
Pocket Pal™
Pocket Turbidimeter™
®
®
®
®
®
®
®
®
®
®
®
®
®
®
SM
®
®
®
Pond In Pillow™
®
ion
√
®
®
®
®
™
SM
®
®
®
®
®
®
SM
®
®
®
®
PourRite
PrepTab™
ProNetic™
Pump Colorimeter™
QuanTab
Rapid Liquid™
RapidSilver™
Ratio™
RoVer
sens
Simply Accurate
SINGLET™
SofChek™
SoilSYS™
SP 510™
Spec ™
StablCal
StannaVer
SteriChek™
StillVer
SulfaVer
Surface Scatter
TanniVer
TenSette
Test ‘N Tube™
TestYES!
TitraStir
TitraVer
ToxTrak™
UniVer
VIScreen™
Voluette
WasteAway™
ZincoVer
12
Sample Procedure Explained
13
Sample Procedure Explained, continued
14
Sample Procedure Explained, continued
15
16
SECTION ICHEMICAL ANALYSIS INFORMATION
Abbreviations
The following abbreviations are used throughout the text of the
procedure section:
Abbrev-
iation
°Cdegree(s) Celsius (Centigrade)HRhigh range
°Fdegree(s) Fahrenheitkg/hakilograms per hectare
ACS
APHA
Standard
Methods
AVAccuVacMRmedium range
BicnbicinchoninateNIPDWR
CFRCode of Federal Regulations NPDES
concconcentratedPphosphorus
DBdropping bottlePCBPoly chlorinated biphenyl
EDLEstimated detection limitPVPhosVer
F&Tfree and totalRLRapid Liquid™
FAU
FMFerroMo
FVFerroVer
FZFerroZine
gr/galgrains per gallon (1 gr/gal = 17.12 mg/L)USEPA
American Chemical Society reagent
grade purity
Standard Methods for the Examination of
Water and Wastewater, published jointly by
the American Public Health Association
(APHA), the American Water Works
Association (AWWA), and the Water
Environment Federation (WEF). Order from
Hach requesting Cat. No. 22708-00 or from
the Publication Office of the American Public
Health Association. This book is the
standard reference work for water analysis.
Many procedures contained in this manual
are based on Standard Methods.
Formazin Attenuation Units. Turbidity unit
of measure based on a Formazin stock
suspension.
ggramsULRUltra low range
Definition
®
®
®
Abbrev-
iation
l or L
lbs/Acpounds per acre
LRlow range
MDLMethod detection limit
MDBmarked dropping bottle
mg/Lmilligrams per liter (ppm)
µg/Lmicrograms per liter (ppb)
ml or mL
SCDBself-contained dropping bottle
TNTTe s t ‘N Tube™
TPHTotal petroleum hydrocarbons
TPTZ(2,4,6-Tri-(2-Pyridyl)-1,3,5-Triazine)
Liter. Volume equal to one cubic
decimeter (dm
(milliliter)-approximately the same as a
cubic centimeter (cc) or 1/1000 of a liter.
Also known as a “cc”.
National Interim Primary Drinking
Water Regulations
National Pollutant Discharge
Elimination System
United States Environmental
Protection Agency
®
Definition
3
)
17
SECTION I, continued
Converting Chemical Species
Species conversion factors for many commonly used substances are
preprogrammed into the DR/2010 (see Table 1). Conversions are method
specific and are viewable after taking the reading by pressing
Table 1 Conversion Factors
To Convert From...To...Multiply By...Conversion used in program #
mg/L Almg/L Al2O
mg/L Bmg/L H
mg/L Ca-CaCO
mg/L CaCO
mg/L CaCO
3
3
3
3BO3
mg/L Ca0.4004220
mg/L Ca0.4004227
mg/L Mg0.2428227
3
1.88959, 10
5.745
µg/L Carbo.µg/L Hydro.1.92182
µg/L Carbo.µg/L ISA2.69182
µg/L Carbo.µg/L MEKO3.15182
mg/L Cr
mg/L Cr
mg/L Mg-CaCO
6+
6+
3
mg/L CrO
mg/L Na2CrO
mg/L Mg0.2428225
mg/L Mnmg/L KMnO
mg/L Mnmg/L MnO
mg/L Mo
mg/L Mo
6+
6+
mg/L MoO
mg/L Na2MoO
mg/L Nmg/L NH
mg/L Nmg/L NO
mg/L Na
mg/L Na
mg/L NH
mg/L NH
mg/L NH
mg/L NH
mg/L NO
mg/L NO
mg/L NO
µg/L NO
mg/L NO
µg/L NO
mg/L NO
mg/L PO
µg/L PO
mg/L PO
µg/L PO
mg/L SiO
µg/L SiO
CrO
2
4
CrO
2
4
Cl-Nmg/L Cl
2
Cl-Nmg/L NH2Cl3.6750386
2
-Nmg/L NH
3
-Nmg/L NH
3
-
2
-
2
-
-Nmg/L NaNO
2
-
-Nµg/L NaNO
2
-
-Nmg/L NO
2
-
-Nµg/L NO
2
-
-Nmg/L NO
3
3-
4
3-
4
3-
4
3-
4
2
2
mg/L Cr
mg/L CrO
mg/L NaNO
mg/L NO
mg/L P0.3261480, 482, 485, 490, 492, 535
µg/L P0.3261488
mg/L P2O
µg/L P2O
mg/L Si0.4674651, 656
µg/L Si0.4674645
2-
4
4
4
-
4
2-
4
4
3
-
3
6+
2-
4
2
3
+
4
2
-
-N0.3045373
2
2
2
-
2
-
2
-
3
5
5
2.23190, 95
3.11590, 95
2.876290, 295
2.165290, 295
1.667315, 320, 322
2.146315, 320, 322
1.216342, 343, 346, 347, 348
4.427346, 347, 348
0.321670
0.72670
5.0623386
1.216380, 385, 387
1.288380, 385, 387
1.5373
4.926345, 371, 375
4.926376
3.284345, 371, 375
3.284376
4.427344, 351, 353, 355, 359, 361
0.7473480, 482, 485, 490, 492, 535
0.7473488
18
CONC.
SECTION I, continued
Hardness Conversion
Table 2 lists the factors for converting one unit of measure for hardness to
another unit of measure. For example, to convert mg/L CaCO
parts/100,000 CaO, multiply the value in mg/L x 0.056.
Table 2 Hardness Conversion Factors
Units of
Measure
mg/L
CaCO
English
British
3
gr/gal
(Imperial)
mg/L
CaCO
CaCO
1.00.070.0580.10.0560.025.6x10
3
14.31.00.831.430.830.2868.0x10
3
American
gr/gal (US)
CaCO
gr/gal
CaCO
3
US gr/gal
CaCO
Fr. p/
17.11.21.01.720.960.3439.66x10
3
10.00.70.581.00.560.25.6x10
100,000
CaCO
3
Ger. p/
17.91.251.041.791.00.3581x10
100,000
CaO
meq/L50.03.52.95.02.81.02.8x10
g/L CaO1790.0125.0104.2179.0100.035.81.00.112
lbs./cu ft
CaCO
16,100.01,123.0935.01,610.0900.0321.09.01.0
3
1 ‘epm/L, or ‘mval/L’
Note: 1 meq/L = 1N/1000
French
parts/
100,000
3
CaCO
3
German
Parts/
100,000
CaO
meq/L
1
g/L CaO
to German
3
lbs./cu ft
-4
6.23x10
-3
-3
1.07x10
-3
6.23x10
-2
1.12x10
-2
3.11x10
CaCO
8.9x10
3
-5
-4
-3
-4
-3
-2
19
SECTION I, continued
Dissolved Oxygen
Table 3 lists the mg/L dissolved oxygen in water at saturation for various
temperatures and atmospheric pressures. The table was formulated in a
laboratory using pure water. The values given are only approximations for
estimating the oxygen content of a particular body of surface water.
Table 3 Dissolved Oxygen Saturation in Water
Pressure in Millimeters and Inches Hg
mm
775760750725700675650625
Temp inches
°F°C30.5129.9229.5328.4527.5626.5725.5924.61
32.0014.914.614.413.913.512.912.512.0
33.8114.514.214.113.613.112.612.211.7
35.6214.113.913.713.212.912.311.811.4
37.4313.813.513.312.912.412.011.511.1
39.2413.413.213.012.512.111.711.210.8
41.0513.112.812.612.211.811.410.910.5
42.8612.712.512.311.911.511.110.710.3
44.6712.412.212.011.611.210.810.410.0
46.4812.111.911.711.310.910.510.19.8
48.2911.811.611.511.110.710.39.99.5
50.01011.611.311.210.810.410.19.79.3
51.81111.311.110.910.610.29.89.59.1
53.61211.110.810.710.310.09.69.28.9
55.41310.810.610.510.19.89.49.18.7
57.21410.610.410.29.99.59.28.98.5
59.01510.410.210.09.79.39.08.78.3
60.81610.19.99.89.59.18.88.58.1
62.6179.99.79.69.39.08.68.38.0
64.4189.79.59.49.18.88.48.17.8
66.2199.59.39.28.98.68.38.07.6
68.0209.39.29.18.78.48.17.87.5
69.8219.29.08.98.68.38.07.77.4
71.6229.08.88.78.48.17.87.57.2
73.4238.88.78.58.28.07.77.47.1
75.2248.78.58.48.17.87.57.27.0
77.0258.58.48.38.07.77.47.16.8
78.8268.48.28.17.87.67.37.06.7
80.6278.28.18.07.77.47.16.96.6
20
SECTION I, continued
Table 3 Dissolved Oxygen Saturation in Water (continued)
Pressure in Millimeters and Inches Hg
mm
775760750725700675650625
Temp inches
°F°C30.5129.9229.5328.4527.5626.5725.5924.61
82.4288.17.97.87.67.37.06.76.5
84.2297.97.87.77.47.26.96.66.4
86.0307.87.77.67.37.06.86.56.2
87.8317.77.57.47.26.96.76.46.1
89.6327.67.47.37.06.86.66.36.0
91.4337.47.37.26.96.76.46.25.9
93.2347.37.27.16.86.66.36.15.8
95.0357.27.17.06.76.56.26.05.7
96.8367.17.06.96.66.46.15.95.6
98.6377.06.86.76.56.36.05.85.6
100.4386.96.76.66.46.25.95.75.5
102.2396.86.66.56.36.15.85.65.4
104.0406.76.56.46.26.05.75.55.3
105.8416.66.46.36.15.95.65.45.2
107.6426.56.36.26.05.85.65.35.1
109.4436.46.26.15.95.75.55.25.0
111.2446.36.16.05.85.65.45.24.9
113.0456.26.05.95.75.55.35.14.8
114.8466.15.95.95.65.45.25.44.8
116.6476.05.95.85.65.35.14.84.7
118.4485.95.85.75.55.35.04.84.6
120.2495.85.75.65.45.25.04.74.5
122.0505.75.65.55.35.14.94.74.4
21
SECTION I, continued
Sample Collection, Preservation and Storage
Correct sampling and storage are critical for accurate testing. For greatest
accuracy, thoroughly clean sampling devices and containers to prevent
carryover from previous samples. Preserve the sample properly; each
procedure has information about sample preservation.
•The least expensive containers are polypropylene or polyethylene.
•The best and most expensive containers are quartz or PTFE
(polytetrafluoroethylene, Teflon).
•Avoid soft glass containers for metals in the
microgram-per-liter range.
•Store samples for silver determination in light absorbing containers,
such as amber bottles.
Avoid contaminating the sample with metals from containers, distilled
water or membrane filters. Thoroughly clean sample containers as
described under Acid Washing Bottles.
Preservation slows the chemical and biological changes that continue
after collection. These changes may change the amount of a chemical
species available for analysis. Normally, analyze the samples as soon as
possible after collection, especially when the analyte concentration is
expected to be low. This also reduces the chance for error and
minimizes labor.
Preservation methods include pH control, chemical addition, refrigeration
and freezing. Table 4 gives the recommended preservation for various
substances. It also includes suggested types of containers and the
maximum recommended holding times for properly preserved samples.
Preserve aluminum, cadmium, chromium, cobalt, copper, iron, lead,
nickel, potassium, silver and zinc samples for at least 24 hours by adding
one Nitric Acid Solution Pillow 1:1 (Cat. No. 2540-98) per liter of
sample. Check the pH with pH indicator paper or a pH meter to assure
the pH is 2 or less. Add additional pillows if necessary. Adjust the sample
pH prior to analysis by adding an equal number of Sodium Carbonate
Anhydrous Powder Pillows (Cat. No. 179-98). Or raise the pH to 4.5
with Sodium Hydroxide Standard Solution, 1 N or 5 N.
22
SECTION I, continued
Table 4 Required Containers, Preservation Techniques and Holding Times
Parameter No./NameContainer
2
Preservation
3,4
1
Maximum
Holding Time
5
Table 1A - Bacterial Tests
1-4. Coliform, fecal and totalP,GCool, 4°C, 0.008%, Na
5. Fecal streptococciP,GCool, 4°C, 0.008%, Na
2S2O3
2S2O3
6
6
6 hours
6 hours
Table 1B - Inorganic Tests
1. AcidityP, GCool, 4°C14 days
2. AlkalinityP, GCool, 4°C14 days
4. AmmoniaP, GCool, 4°C, H
9. Biochemical oxygen demand
P, GCool, 4°C48 hours
to pH<228 days
2SO4
(BOD)
10. BoronP, PFTE or quartzHNO
to pH<26 months
3
11. BromideP, GNone required28 days
14. Biochemical oxygen demand,
P, GCool, 4°C48 hours
carbonaceous
15. Chemical oxygen demandP, GCool, 4°C, H
to pH<228 days
2SO4
16. ChlorideP, GNone required28 days
17. Chlorine, total residualP, GNone requiredAnalyze immediately
21. ColorP, GCool, 4°C48 hours
23-24. Cyanide, total and amenable
to chlorination
P, GCool, 4°C, NaOH to pH>12, 0.6 g
ascorbic acid
6
14 days
7
25. FluoridePNone required28 days
27. HardnessP, GHNO
to pH<2, H2SO4 to pH<26 months
3
28. Hydrogen ion (pH)P, GNone requiredAnalyze immediately
1 This table was adapted from Table II published in the Federal Register, July 1, 1997, 40 CFR, Part 136.3,
pages 26-27. Organic tests are not included.
2 Polyethylene (P) or glass (G).
3 Sample preservation should be performed immediately upon sample collection. For composite chemical samples
each aliquot should be preserved at the time of collection. When use of an automated sampler makes it impossible
to preserve each aliquot, then chemical samples may be preserved by maintaining at 4°C until compositing and
sample splitting is completed.
4 When any sample is to be shipped by common carrier or sent through United States Mails, it must comply with the
Department of Transportation Hazardous Material Regulations (49 CFR Part 172). The person offering such
material for transportation is responsible for ensuring such compliance. For the preservation requirements of Table
II, the Office of Hazardous Materials, Materials Transportation Bureau, Department of Transportation has
determined that the Hazardous Materials Regulations do not apply to the following materials: Hydrochloric acid
(HCl) in water solutions at concentrations of 0.04% by weight or less (pH about 1.96 or greater); Nitric acid (HNO
in water solutions at concentrations of 0.15% by weight or less (pH about 1.62 or greater); Sulfuric acid (H
water solutions at concentrations of 0.35% by weight or less (pH about 1.15 or greater); and Sodium hydroxide
(NaOH) in water solutions at concentrations of 0.080% by weight or less (pH about 12.30 or less).
5 Samples should be analyzed as soon as possible after collection. The times listed are the maximum times that
samples may be held before analysis and still be considered valid. Samples may be held for longer periods only if
the permitee, or monitoring laboratory, has data on file to show that the specific types of samples under study are
stable for the longer time, and has received a variance from the Regional Administer under §136.3(e). Some
samples may not be stable for the maximum time period given in the table. A permitee, or monitoring laboratory, is
obligated to hold the sample for a shorter time if knowledge exists to show that this is necessary to maintain sample
stability. See §136.3(e) for details. The term “analyze immediately” usually means within 15 minutes or less after
sample collection.
6 Should only be used in the presence of residual chlorine.
7 Maximum holding time is 24 hours when sulfide is present. Optionally all samples may be tested with lead acetate
paper before pH adjustments in order to determine if sulfide is present. If sulfide is present, it can be removed by the
addition of cadmium nitrate powder until a negative spot test is obtained. The sample is filtered and then NaOH is
added to pH 12.
8 Samples should be filtered immediately on-site before adding preservative for dissolved metals.
9 Numbers refer to parameter number in 40 CFR, Part 136.3, Table 1B.
2
P, GCool 4°C, add zinc acetate plus
Preservation
sodium hydroxide to pH>9
3,4
to pH<228 days
2SO4
Maximum
Holding Time
7 days
2SO4
5
) in
)
3
24
SECTION I, continued
Collecting Water Samples
Obtain the best sample by careful collection. In general, collect samples
near the center of the vessel or duct and below the surface. Use only clean
containers (bottles, beakers). Rinse the container several times first with
the water to be sampled.
Take samples as close as possible to the source of the supply. This lessens
the influence the distribution system has on the sample. Let the water run
long enough to flush the system. Fill sample containers slowly with a
gentle stream to avoid turbulence and air bubbles. Collect water samples
from wells after the pump has run long enough to deliver water
representative of the ground water feeding the well.
It is hard to obtain a truly representative sample when collecting surface
water samples. Obtain best results by testing several samples. Use
samples taken at different times from several locations and depths. The
results can be used to establish patterns for that particular body of water.
Generally, as little time as possible should elapse between collecting the
sample and analyzing it.
Depending on the test, special precautions in handling the sample may be
necessary. This prevents natural interferences such as organic growth or
loss or gain of dissolved gases. Each procedure describes sample
preservatives and storage techniques for samples that are held for testing.
Acid Washing Bottles
If a procedure suggests acid-washing, use the following procedure:
Use chromic acid or chromium-free substitutes to remove organic
deposits from glass containers. Rinse containers thoroughly with water
to remove traces of chromium.
a) Clean the glassware or plasticware with laboratory detergent
(phosphate-free detergent is recommended).
b) Rinse well with tap water.
c)Rinse with a 1:1 Hydrochloric Acid Solution or 1:1 Nitric Acid
Solution. The nitric acid rinse is important for testing for lead.
d) Rinse well with deionized water. Up to 12-15 rinses may be
necessary if chromium is being determined.
e)Air dry.
25
SECTION I, continued
Wash glassware for phosphate determinations with phosphate-free
detergents and acid-wash with 1:1 HCl. Thoroughly rinse the glassware
with deionized water. For ammonia and Kjeldahl nitrogen, rinse with
ammonia-free water.
Correcting for Volume Additions
If you use a large volume of preservative, correct for the volume of
preservative added. This accounts for dilution due to the acid added to
preserve the sample and the base used to adjust the pH to the range of the
procedure. This correction is made as follows:
1.Determine the volume of initial sample, the volume of acid and base
added, and the total final volume of the sample.
2.Divide the total volume by the initial volume.
3.Multiply the test result by this factor.
Example:
A one-liter sample was preserved with 2 mL of nitric acid. It was
neutralized with 5 mL of 5 N sodium hydroxide. The result of the analysis
procedure was 10.00 mg/L. What is the volume correction factor and
correct result?
Boiling Aids
Total Volume1000 mL 2 mL5 mL++1007 mL==
1.
1007
-------------1.007volume correction factor==
2.
1000
10.0 mg/L1.007×10.07 mg/Lcorrect result==
3.
Hach 1:1 Nitric Acid Pillows contain 2.5 mL of acid: correct for this
volume. The addition of a Sodium Carbonate Power Pillow neutralizes the
1:1 Nitric Acid Pillow does not need to be corrected for.
Boiling is necessary in some procedures. Using a boiling aid such as
boiling chips (Cat. no. 14835-31) reduces bumping. Bumping is caused
by the sudden, almost explosive conversion of water to steam as it is
heated. Avoid bumping; it may cause sample loss or injury.
Make sure the boiling aids will not contaminate the sample. Do not use
boiling aids (except glass beads) more than once. Loosely covering the
sample during boiling will prevent splashing, reduce the chances of
contamination and minimize sample loss.
26
SECTION I, continued
Sample Filtration
Filtering separates particles from the aqueous sample. Filtration uses a
medium, usually filter paper, to retain particles but pass solution. This is
especially helpful when sample turbidity interferes with analysis. Two
general methods of filtration are gravity and vacuum. Gravity filtration
uses gravity to pull the sample though the filter paper. Vacuum filtration uses
suction and gravity to move the sample through the filter. An aspirator or
vacuum pump creates the suction. Vacuum filtration is faster than gravity
filtration. Vacuum filter (see Figure 1) as follows:
1.Using tweezers, place a filter paper into the filter holder.
2.Place the filter holder assembly in the filtering flask. Wet the filter
with deionized water to ensure adhesion to the holder.
3.Position the funnel housing on the filter holder assembly.
4.While applying a vacuum to the filtering flask, transfer the sample to
the filtering apparatus.
5.Slowly release the vacuum from the filtering flask and transfer the
solution from the filter flask to another container.
Flask, filter, 500 mL ................................................................................ each..................546-49
Pump, vacuum, hand operated ................................................................each..............14283-00
OR
Pump, vacuum, portable, 115 V ..............................................................each..............14697-00
Pump, vacuum, portable, 230 V ..............................................................each..............14697-02
27
SECTION I, continued
Many of the procedures in this manual use gravity filtration. The only
labware required is filter paper, a conical funnel and a receiving flask.
This labware is included under Optional Equipment and Supplies at the
end of a procedure. Gravity filtration is better for retaining fine particles.
For faster filtering, add solution until the filter paper cone is three-fourths
filled. Never fill the cone completely. Gravity filter (see Figure 2)
as follows:
1.Place a filter paper into the funnel.
2.Wet the filter with deionized water to ensure adhesion to the funnel.
3.Place the funnel into an erlenmeyer flask or graduated cylinder.
4.Pour the sample into the funnel.
Figure 2Gravity Filtration
REQUIRED APPARATUS FOR GRAVITY FILTRATION
DescriptionUnitCat No.
Cylinder, graduated, 100 mL ...................................................................each ................. 508-42
Funnel, poly, 65 mm ................................................................................each ............... 1083-67
Filter Paper, 12.5 cm ................................................................................each ............... 1894-57
Flask, erlenmeyer, 125 mL ......................................................................each ................. 505-43
Testing for metals requires acid and heat to pretreat the sample. Since
these conditions destroy filter paper, vacuum filtration with glass fiber
filter discs is recommended. Also, glass filter discs, unlike paper, do not
retain colored species.
28
SECTION I, continued
Temperature Considerations
For best results, most tests in this manual should be performed with
sample temperatures between 20 °C (68 °F) and 25 °C (77 °F). If a
test requires closer temperature control, notes in the procedure will
indicate this.
Sample Dilution Techniques
Ten and 25 mL are the volumes used for most colorimetric tests.
However, in some tests, the color developed in the sample may be too
intense to be measured. Unexpected colors may develop in other tests.
In both cases, dilute the sample to determine if interfering substances
are present.
To dilute the sample easily, pipet the chosen sample portion into a clean
graduated cylinder (or volumetric flask for more accurate work). Fill the
cylinder (or flask) to the desired volume with deionized water. Mix well.
Use the diluted sample when running the test.
To help with dilutions, Table 5 shows the amount of sample used, the
amount of deionized water used to bring the volume up to 25 mL and the
multiplication factor.
The concentration of the sample is equal to the diluted sample reading
multiplied by the multiplication factor.
More accurate dilutions can be done with a pipet and a 100-mL
volumetric flask (see Table 6 for more information). Pipet the sample and
dilute to volume with deionized water. Swirl to mix.
Table 5 Sample Dilution Volumes
Sample
Volume (mL)
25.00.01
12.512.52
1
10.0
1
5.0
1
2.5
1
1.0
1
0.250
1 For sample sizes of 10 mL or less, use a pipet to measure the sample into the graduated
cylinder or volumetric flask.
mL deionized Water Used
to Bring the Volume to 25 mL
15.02.5
20.05
22.510
24.025
24.75100
Multiplication
Factor
29
SECTION I, continued
Table 6 Multiplication Factors for Diluting to 100 mL
Sample Volume (mL)Multiplication Factor
1100
250
520
1010
254
502
Sample Dilution and Interfering Substances
Sample dilution may influence the level at which a substance may
interfere. The effect of the interferences decreases as the dilution
increases. In other words, higher levels of an interfering substance can be
present in the original sample if it is diluted before analysis.
An Example:
Copper does not interfere at or below 100 mg/L for a 25.00 mL sample in a
procedure. If the sample volume is diluted with an equal volume of water, what is
the level at which copper will not interfere?