Environmental Sampling and Analysis for Metals - Chapter 14 pptx

14.1.3 P REFIELD P ROCEDURES Several prefield procedures must be considered prior to the sampling activities: • Selection of proper sampling equipment preferred materials for sampling an

Metals Analysis

14.1 GENERAL CONSIDERATIONS IN SAMPLING

The quality of any analytical system depends primarily on the sample analyzed A sample must berepresentative of the environmental system from which it is taken so that chemical analysis results,

in turn, represent the system

14.1.1 F ACTORS AND R EQUIREMENTS OF S AMPLING P ROGRAM

• Grab or composite samples (see Section 14.1.4)

• Manual and automatic sampling (see Section 14.1.5)

• Field measurements

• Quality control (QC) requirements

14.1.2 P REPARATION FOR S AMPLE C OLLECTION

• Understand the sampling plan; all information should be written and discussed with fieldpersonnel

• Prepare, clean, and calibrate sampling equipment so that it is ready to use

• Check, calibrate, and prepare equipment for field tests

• Prepare sample containers

• Prepare preservative and dispose in a safe container

• Collect labels and markers, field notebook, pH paper, and small disposable cups to check

pH of preserved samples

• Prepare all blanks

• Check all calibration standards and expiration dates for freshness If necessary, preparenew ones

• Check QC samples for availability, and check dates for freshness If necessary, preparenew ones Determine whether sample should be spiked and discuss concentration of thespikes Calculate the volume of the added spike stock solution for each spiked parameter.14

204 Environmental Sampling and Analysis for Metals

• Collect pipets with suitable volumes and pipet bulbs

• Collect empty bottles for splits, duplicates, and so on

• Collect glassware for field tests and check cleanliness of glassware

• Make sure that thermometers are stored in protective carriers to avoid breakage

• Check spike stock solutions and check dates for freshness If necessary, prepare new ones

• Collect soap for cleaning sampling equipment and for washing hands, paper towels, softtissues, and bottles with DI (deionized) water

14.1.3 P REFIELD P ROCEDURES

Several prefield procedures must be considered prior to the sampling activities:

• Selection of proper sampling equipment (preferred materials for sampling and purging ment for metals analysis include Teflon, polypropylene or polyethylene, and stainless steel)

equip-• Decontamination of sampling equipment

• Selection of sample bottles

• Preservative preparation

• Preparation and calibration of field analytical instruments

• Preparation of sample labels, chain-of-custody forms, field notebook, waterproof ink, and so on

14.1.4 T YPES OF S AMPLES

14.1.4.1 Grab or Individual Samples

Samples collected at a particular time and place are called grab or individual samples This type of

sample represents conditions at the time it was collected Therefore, a grab sample should not be used

as a basis for decision making about pollution abatement However, some sources are quite stable incomposition, thus single-grab samples would be considered representative

14.1.4.2 Composite Samples

If results for an entire source system are to be reported, a series of small samples are collected in a gle container and blended for analysis The mixing process averages variations in sample composition

sin-and minimizes analytical effort sin-and expense These types of samples are called composite samples When

a time factor is being taken into consideration, grab samples are collected at suitable intervals according

to expected changes Composite samples reflect average characteristics during the sampling period, and

in most cases a 24-h period is standard Subsample volume should be constant and at least 200 ml

14.1.5 M ANUAL AND A UTOMATED S AMPLE C OLLECTION

14.1.5.1 Manual Sample Collection

When collecting samples for immediate field tests or when automatic samplers are not available, lect samples directly into a sample container If a sample cannot be placed directly into the container,

col-an intermediate vessel should be used The intermediate container must be as clecol-an as the samplecontainer and must be made from the required material for parameter of interest The sample is col-lected by lowering a properly cleaned device on a rope, pole, or chain into the sample medium Insome cases, using a power or hand-operated pump is necessary to withdraw the sample Whencollecting samples for metals analysis, rinsing the sampling device three times is sufficient, except ifthe bottles are prepreserved

14.1.5.2 Automated Sample Collection

A wide variety of automatic samplers are commercially available When sampling a large number oflocations, automatic samplers are more practical, help reduce human error, and are able to keep thesamples cool to 4°C during the time spent gathering samples Automatic samplers, however, are ex-pensive

14.1.6 G ENERAL R ULES IN S AMPLING

• Samples must be collected from the least to the most contaminated sampling locationswithin the site

• Disposable latex gloves must be worn while sampling, and new, unused gloves must beused for each separate sampling point

• For compositing or mixing samples for metals analysis, use a stainless steel or Teflon bowl

• Keep in mind that the order of sample collection is as follows:

1 Volatile organic compounds (VOCs)

14.1.7 P ROPER M ATERIAL FOR S AMPLING D EVICES

Devices used for collecting samples for metals analysis should be made of plastic, stainless steel,

or Teflon

14.1.8 E RRORS I NTRODUCED DURING S AMPLING

Serious errors that may be introduced during sampling and storage are the contamination resultingfrom improperly cleaned sampling devices and sample containers and loss of metals by absorption

or precipitation in sample containers because of failure to acidify the sample properly

14.1.9 W ASTE D ISPOSAL IN THE F IELD

Wastes generated during sampling are separated into specialized and properly labeled waste tainers Laboratory- and field-generated wastes are disposed of by certified waste management com-panies The certificate and contract of this company should be recorded

con-14.2 AUTOMATIC SAMPLERS

14.2.1 P ROPER O PERATION OF A UTOMATIC S AMPLERS

To ensure proper operation of automatic samplers and thus the collection of representative samples,correct maintenance and calibration must be followed:

• A maintenance log containing all repair information should be available

• Prior to each field trip, check the sampler for correct operation (proper working order, teries, desiccant, etc.)

bat-206 Environmental Sampling and Analysis for Metals

• Before sampling, check the constant pumping volume

• After returning from the field, check operation of sampler and repair if necessary

14.2.2 P REPARATION OF S AMPLING E QUIPMENT

Step-by-step cleaning procedures (called decon for decontamination) should be performed These

procedures derive from specific regulations and must be available in written form Equipment should

be cleaned before sampling and in the field between samples At the end of the field trip, samplingequipment must be labeled as “rinsed, ready for house cleaning.” After being sufficiently cleaned inthe laboratory, the equipment should be labeled as “in-house cleaned, ready for field,” accompanied

by the date and the signature of the cleaner Both house and field cleaning should be documented

properly Detergents specified for cleaning include Alconox (or equivalent) with 5% phosphate, or Liquinox (or equivalent), which is free of phosphates and ammonia.

The purity and reliability of the analyte-free water used for rinsing and blank preparation areshown in results of tests performed on the blank

14.2.2.1 In-House Cleaning of Sampling Equipment

1 Wash with hot, soapy tap water and scrub with a brush

2 Rinse thoroughly with hot tap water

3 Rinse with 10 to 15% nitric acid (HNO3) Acid rinses should never be applied to stainlesssteel or metallic equipment

4 Rinse thoroughly with deionized water

5 Rinse thoroughly with pesticide-grade isopropanol

6 Rinse thoroughly with analyte-free water

7 Air dry completely

8 Wrap in aluminum foil for storage and transportation

14.2.2.2 Field Cleaning of Sampling Equipment

Use the same procedure as in-house cleaning procedure, with the exception of hot water wash andrinse Laboratory-pure water rinse is recommended, but optional Rinsing with sample water is ac-ceptable when proper cleaning of the equipment is impossible It should be disposed of until effec-tive cleaning is possible

14.3 SAMPLE CONTAINERS

14.3.1 P REFERRED S AMPLE C ONTAINERS

• Preferred sample containers for metals analysis are polyethylene bottles with tight, type lids

screw-• Borosilicate glass containers also may be used, but avoid soft glass bottles for samplescontaining metals in the microgram-per-liter (ppb) range

• Store samples for silver analysis in light-absorbing containers

• Sample containers may be cleaned in-house or in the field or purchased from commercialvendors as precleaned containers The cleaning grades must meet EPA analyte-specific re-quirements All records for these containers (lot numbers, certification statements, date ofreceipt, etc.) and their uses must be documented

14.3.2 P ROPER C LEANING OF S AMPLE C ONTAINERS

1 The soap should be metal-free Acationox or equivalent.

2 Wash bottles and caps in hot, soapy water and rinse liberally with tap water until soapsudsare gone

3 Rinse bottles and caps with 1+1 HCl, followed by tap water rinse

4 Rinse bottles and caps with 1+1 HNO3

5 Rinse three times with liberal amounts of laboratory-pure water

6 Drain and cap tightly until used

14.4 SAMPLE PRESERVATION

Sample preservation is necessary for all samples (40 CFR, Part 136) Sample preservation may be complished by using ready, prepreserved bottles obtained from the laboratory, but additional preser-vatives must be available in the field if the measured pH of the preserved sample indicates that addi-tional preservative is necessary

ac-If the sample is preserved in the field, the following protocols should be practiced:

• Preservative should be prepared from reagent-grade chemical

• Fresh preservative should be used in each sampling trip

• Preservatives transported to the field should be stored in properly cleaned plastic or Tefloncontainers to avoid breakage

• Chemicals should be segregated from sample containers to avoid accidental contamination

• Preservatives should be added with a pipet or premeasured droppers

• After preservation, the pH of the preserved sample should be measured Transfer a smallquantity from the preserved and well-mixed sample into a disposable container, and de-termine the pH by using a narrow-range pH paper If the pH value indicates the addition

of more preservative, the preservative should be from the same source as used in the inal treatment The amount of the additional preservative should be documented, and theadditional preservative should be added to the corresponding blank as well

orig-• Acid preservation should be done in a well-ventilated area to avoid inhalation of acidfumes and toxic gases Any unusual reaction should be noted!

• In the case of any acid spill, wipe up immediately and flush the area with a great amount

of water

14.5 SPECIAL SAMPLING PROCEDURES

Before collecting a sample, decide on the metal fraction to be analyzed: dissolved (filterable), pended (nonfilterable), or total metals This decision will determine whether the sample is acidifiedwith or without filtration

208 Environmental Sampling and Analysis for Metals

14.5.2 D ISSOLVED M ETALS

Dissolved metals are defined as the concentration of metals determined in the sample after it is tered through a 0.45-µm filter Samples must be filtered through a 0.45-µm filter prior to preserva-tion Filter paper should be acid washed and dried before use After the sample is filtered, the filtratewill be the sample for dissolved metals and acidified in the same way as for total metals

fil-14.5.3 S USPENDED M ETALS

Suspended metals are defined as the concentration of metals determined in the portion of the samplethat is retained in a 0.45-µm filter Unpreserved samples are filtered through a 0.45-µm filter, as men-tioned above for the sample collection of dissolved metals, and the filter paper is retained for furtheranalysis of the suspended or unfilterable metals The filter paper containing the suspended matter istransferred to the laboratory for determination of suspended metals Samples should be filtered in thefield, or immediately after transport to the laboratory In the latter case, preserve the filtrate

14.5.4 S AMPLE C OLLECTION OF H EXAVALENT C HROMIUM

Materials containing hexavalent chromium (Cr6+) are sampled separately from other metals Do notadd acid preservation to this sample; transport it to the laboratory for analysis as soon as possible.During transportation and storage, samples should be kept at 4°C

“No preservative added” should be clearly written on the sample label in the request for this type

of sample Holding time is 24 h for these samples.

14.6 HOLDING TIME

Holding time for most preserved samples is 6 months For mercury (Hg) determination, holding time

of the preserved sample is 28 days Samples collected without preservation for the determination ofhexavalent chromium (Cr+6) can be held for only 24 h A sample holding-time log is illustrated in

Figure 14.1

14.7 FIELD RECORDS

Field records are taken for all data generated during sample collection These records are kept in achain-of-custody form (Figure 14.2), sample label (Figure 14.3), field notebook (Figure 14.4), sam-ple field log (Figure 14.5), preservative preparation log (Figure 14.6), and QC sample and spikepreparation log (Figure 14.7)

14.7.1 C HAIN - OF -C USTODY

All sampling events should be documented and recorded on a chain-of-custody form This practiceensures that the sample is collected, transferred, stored, analyzed, and destroyed only by authorizedpersonnel Each custodian or sampler must sign, record, and date the transfer The form includes thename of the sampling project; collector’s signature; sampling location; sampling site; sampling point,date, and time; type of sample; number of containers; and analysis required The chain-of-custodyform is illustrated in Figure 14.2

a single-line cross-through, accompanied by the date and initial of the person making the correction.

FIGURE 14.1 Sample holding-time log.

Sample ID = sample identification number; prep = prepared; anal = analysis; dispo = disposal; rec = received; sign = signature of logger.

Holding Time Explanation:

prep = number of days between the date sample received and the date sample prepared

anal = number of days between the date sample prepared and the date of actual analysis

dispo = number of days between the date sample received and the date sample disposed

Storage Designations:

R T = room temperature in designated area

Ref O = refrigerator, designated for organic samples

Ref I = refrigerator, designated for inorganic samples

Fr = freezer, designated for special samples

Field ID: Site Name:

Date Sampled Received: Address:

Sampler(s): _ Laboratory:

Sample Container Description

FIGURE 14.2 Chain-of-custody form.

Relinquished By: Organization: Received By: Organization:

Relinquished By: Organization: Received By: Organization:

Delivery Method: (attach shipping bills, if any)

Use extra sheets if necessary.

Remarks Total

Date Sampled Sample Identity

Total Number of Containers

© 2002 by CRC Press LLC

FIGURE 14.3 Sample label.

Field Sequence No. _ Field Sample No. Date _Time Sample Location _ Sample Source _ Preservative Used Analyses Required _ _ Collected by Remarks _ _ Final pH Checked Additional Preservative Used (If Applicable) _ _

FIGURE 14.4 Field notebook.

Date _ Time Sampler’s name _ Signature Other field people

Sample location

Sample type grab

composite Compositing time hr

Time interval _min Subsample volume _ml

Sq No = sample sequence number; FID = field identification number; Cond = conductivity; DO = dissolved oxygen; Cl 2 = chlorine, residual; ppm = parts per million (mg/l).

Cond.

( µmhos /cm)

DO (ppm) Cl 2 Comment

212 Environmental Sampling and Analysis for Metals

14.7.4 S AMPLE F IELD L OG AND P RESERVATIVE P REPARATION L OG

Other field records are the sample field log (Figure 14.5) and preservative preparation log(Figure 14.6) Immediately after sampling while still at the sampling point, the correct preservationand proper identification of samples (chain-of-custody and submittal forms, sample labels, etc.)should be checked

14.7.5 I NFORMATION A VAILABLE IN F IELD R ECORDS

The following information should be available in field records:

• Name of sample collector and field personnel

• Date and time of sampling

• Field conditions (weather, important information about the sample site)

• Description of sample location (address, exact sampling points)

• Sample type (grab, composite) If composite sample, record the time intervals, duration ofsampling, and volume of subsamples

• Requested analytical parameters, type and number of containers, preservation technique

• Preservative preparation

FIGURE 14.5 Sample field log.

Purpose of Analysis: _Sample Field ID: Type of Sample: _ Sampler: Date/Time:

Bottle

No. Preservative Analysis Required

Remarks:

* Field Measurements

FIGURE 14.6 Preservative preparation log.

Preservative Preparation Procedure _ Date Prepared Date of Expiration Analyte Preserved _ Information Related to the Chemical Used:

Name, formula, and grade of the chemical

Source of the chemical (name of manufacturer)

Lot no of the chemical Date chemical received Date container was opened Expiration date _ Storage of the chemical Check of Preservative _

FIGURE 14.7 Field sample spike preparation log.

Analyte spiked _ Field no of sample spiked Sample volume spiked _ Value of spike added Concentration of spike stock solution Volume of spike stock solution added Source of spike stock solution:

Commercial source

Manufacturer: _ Lot no.: _ Date received: _ Date expired: Laboratory prepared

Date of preparation: Expiration date: Date spike sample prepared Signature of field personnel