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RP – DRAFT -
GFAAS-Z
ELEMENTAL ANALYSIS OF AMBIENT AIR PARTICUALATE SAMPLES
COLLECTED FROM SEAS USING GFAAS-Z
Identification code: RP GFAAS-Z
RP Working RP pages
Issue Date: 01/04/2001
Revision No:1
Revision date:06/10/2002
Revision description:
APPROVALS
Local PI:01/22/2001
Local PI:
End cap GF tubes and 5% H2 for group 2 elements. Improved detection limits for As,
Se, Pb and Ni
Revision No:3
Revision date:5/1/03
Revision description:
Inclusion of NIST’s interim PM2.5 RM
Local PI:
Rev. 1. date
1/9/01
Rev. 2. date
Rev. 3. date

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GFAAS-Z
ELEMENTAL ANALYSIS OF AMBIENT AIR PARTICUALATE SAMPLES
COLLECTED FROM SEAS USING GFAAS-Z
1. PURPOSE AND APPLICABILITY
This research protocol (RP) contains protocol for performing multi elemental analysis of aqueous slurry samples using Perkin-Elmer SIMAA 6000. This is an evaluation version of an anticipated standard operating procedure (SOP), which will result from experiences with this RP.
Due to this fact, this RP is subject to change. The SIMAA6000 is capable of determining upto six elements simultaneously. Samples are analyzed for multiple multielement suites to achieve analyses for all of the elements desired. Note that the number and choice of elements to be determined in each analytical suite are being reoptimized, and both are subject to change.
2. REFERENCES
The Perkin Elmer SIMAA 6000 Instrument Manual, ‘Installation, Maintenance, and
System Description’ (Part Number 0993-5218).
The Perkin Elmer SIMAA 6000 Instrument Manual, ‘Setting Up and Performing
Analyses’ (Part Number 0993-5219).
The Perkin Elmer SIMAA 6000 Instrument Manual, ‘AA WinLab for SIMAA 6000,
Software Guide’ (Part Number 0993-5216).
Kidwell, C. B., Ondov, J. M. (Submitted), ‘Elemental Analysis of Sub-Hourly Ambient
Aerosol Collections’
, Aerosol Sci. Technol., Jan 2001 .
Caulcutt, R., Boddy, R., ‘Statistics for Analytical Chemists’, Chapman and Hall, New
York, 1983.
Miller, J.C., Miller, J.N, ‘Statistics for Analytical Chemistry’, 3 rd
edition, Ellis Horwood
PTR Prentice Hall, 1993.

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3.
TERMINOLOGY
GFAAS-Z
GFAAS-Z: Graphite Furnace Atomic Absorption Spectrometer with Zeeman background correction.
SIMAA: Simultaneous Multielemental A tomic A bsorption
NIST: National Institute of Standards and Technology, Gaithersburg, USA
SEAS: Semicontinuous Environmental Aerosol Sampler
RSD:
RP:
Relative Standard Deviation
Research Protocol
Analyte: The component of a sample that is under investigation whose concentration is sought.
Accuracy: The degree to which the results obtained agrees with the actual concentration.
Precision: Nearness of the measurements made on the same sample with same measurement system.
SRM : RM certified by a certifying body such as National Institute of Standards and
Technology (NIST), National Institute of Environmental Studies, Japan (NIES) or
Japan Society for Standards (JSS), whose constituent concentrations are certified by a procedure which establishes its traceability and is accompanied by an uncertainty statement at a stated level of confidence.
Characteristic mass: Mass of the analyte that gives one percent absorption.
4.
EQUIPMENT
4.1 Perkin Elmer SIMAA 6000:
This instrument operates under Stabilized Temperature Platform Furnace Technology (STPF) that uses a transversely heated graphite atomizer with an integrated L’vov platform. Suspended solids up to about 1% can be accommodated, but analytical results will suffer somewhat.
Multielemental analyses are accomplished using a tetrahedral echelle polychromator (TEP) optical arrangement. The detector is a monolithic solid-state type with 61 high performance photodiodes which allow for simultaneous determination of up to six elements. Background correction is achieved by a longitudinal Zeeman system. SIMAA6000 is also equipped with 40 and 80-position autosampler trays.
4.2 ACCESSORIES
1.
HEPA filter
2.
Exhaust hood
3.
Hollow Cathode Lamps (HCL) Pb, Bi, Cd, Al, Ag, Ti, Ca, V, Cr, Mn, Fe, Ni, Cu and Zn
4.
Electrodeless Discharge Lamps (EDL) As, Se
5.
Pyrollytically coated graphite tubes
6.
Autosampler vials
7.
Auto sampler pipettes

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4.3 OTHER MATERIALS
1.
Elemental standard solutions
2.
Volumetric flasks(class A)
3.
Autopipettes and tips
4.
Ultrapure Conc nitric acid
5.
Milli-Q water(18.2 M

cm-1)
6.
Ultrahigh pure grade Argon gas
GFAAS-Z
7.
Computer
8.
Laboratory notebook
9.
Data entry forms
5.
PROCEDURES
5.1
Cleaning of sample vials, volumetric flask, reagent bottles and autosampler cups
1. Rinse material with distilled water.
2. Soak overnight in (10+1) reagent grade nitric acid.
3. Rinse 3 TIMES with Milli-Q water.
4. Soak overnight in Milli-Q water.
5. Dry overnight in clean hood.
6. Wear disposable powder-free gloves for all handling of the materials after step 4.
Cleaning may be done in bulk quantities
Note
: The word ‘
Clean
’ in this RP implies that the ones, which had been treated as said above.
5.2 Preparation of working standards from stock solution
1.
The following procedures must be performed in a laminar flow workbench (or in class 100 clean room).
2.
Shake the stock solutions well before use.
3.
Use only calibrated flasks (Class A), and auto pipettes having precision

0.25 for dilutions.
4.
Never attempt dilutions more than 100 times at a single step
5.
Always use 0.5% (v/v) ultrapure nitric acid for dilutions. Working standards can have 0.1% nitric acid. Remember to prepare fresh working standards every week as hydrolysis could change metal concentrations at low acid strength.
6.
Give sufficient time (~30 min) for the solution to attain equilibrium after every step of dilution.
7.
Transfer the appropriately diluted standard solution into a clean polyethylene bottle. It should have a label stating the element name, concentration, and date prepared.
6.
GFAAS-Z OPERATIONS

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GFAAS-Z
6.1 To power up
1.
Make sure the computer is securely connected to the instrument and switched on.
2.
Check the autosampler rinse and waste containers. Fill the rinse container with ultrapure 5%
(v/v) nitric acid and 0.001% triton x-100 solution mixture.
3.
Set the supply valve on the argon tank to 50 psi.
4.
Turn on exhaust fan and HEPA filter.
5.
Make sure that the water level is at maximum in the cooling tank
6.
Turn on the SIMAA 6000 from the green button on the lower left front.
7.
Wait approximately 1 minute for the autosampler to warm up.
8.
Start AA Winlab on the computer. After about 1 minute, the startup screen will appear.
9.
Click the Default button. Follow the on-screen message.
6.2 To shut down:
1.
Exit AA Winlab.
2.
Turn off the SIMAA 6000 from the green button on the lower left front.
3.
Close the supply valve on the argon tank.
4.
Turn off the exhaust fan and HEPA filter.
6.3 To analyze samples:
1.
Elements of interest are grouped into three suites. [Suite 1 (Al, Cr, Mn, Cu, Fe), Suit 2 (Se,
As, Ni, Pb), and Suite 3 (Zn, Cd)]. Select the customized methods by calling the method name. Refer to Chapter 1 of “AA WinLab for SIMAA 6000” manual for details.
2.
Install the appropriate (each suite has a separate lamp holder with lamps installed already) lamp assembly.
3.
From the Lamps window, turn on the desired lamps and align them to get the maximum signal intensity. Allow 45 minutes for lamps to warm up before beginning analysis.
4.
Enter sample data into the Sample Information File and fill the autosampler tray with sample vials. Sample vials should only be filled about 75% of the capacity of vials (1 ml). Adding more solution will cause droplets to adhere to the autosampler tip that will lead to pipetting errors.
5.
To reduce evaporation of water from the sample vials, place about 20 ml of Milli-Q water in the bottom of the autosampler tray, i.e., enough to cover the bottom but without touching the sample vials.
6.
From the Automated Analysis Control window, click the Setup tab and select locations for samples to be analyzed. Specify the Sample Information File (SIF) to be used and the Results file to store data.
7.
Click the ‘Analyze All’ button to analyze all specified samples in SIF.
6.4 Furnace Tubes:
Graphite furnace tubes should be good for 500 - 600 firings. Samples with high concentrations of acid and/or high atomization temperatures will cause faster degradation.
Graphite tube replacement:
1.
In the Furnace Control window (Chapter 4), click the Open/Close button.
2.
Unscrew the autosampler assembly, using the knob below the autosampler, and swing aside.

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GFAAS-Z
3.
Swing the furnace support lever aside and tilt the furnace contact down.
4.
Use the clothespin to remove and inspect the graphite tube. Never handle graphite tubes with bare hands.
5.
Clean the furnace contacts with a cotton swab to remove any carbon buildup.
6.
Insert the graphite tube into the rear contact. The higher side of the platform within the furnace tube should be located to the rear of the furnace.
7.
Carefully tilt the furnace contact up and replace the support lever.
8.
Replace the autosampler assembly.
9.
Click the Open/Close button.
10.
Check the autosampler tip alignment using the Tip Align button.
If a new tube is inserted, click the Condition Tube button. Also go to Diagnostics in the Tools menu, click the Furnace tab, and click Reset for the number of tube cycles.
6.5 Instrumental operating conditions
The GFAAS-Z operating conditions are summarized below.
Purge pas
Atomize
Cleanout
Suite 1 Suite 2 Suite 3
Elements Al, Cr, Mn, Cu, Fe Se, As, Ni, Pb Cd, Zn
Sample Volume 20 µL
20+20 µL 10 µL
Dry Stage 1
Dry Stage 2
Char
25 s, 110°C
25 s, 130°C
25 s, 1250°C
25 s, 110°C
20 s, 130°C
20 s, 1000°C
20 s, 110°C
20 s, 130°C
15 s, 500°C
5% H2/Ar mix
5 s, 2400°C
3 s, 2450°C
5% H2/Ar mix Ar gas
5 s, 2300°C
3 s, 2400°C
5 s, 1900°C
3 s, 2450°C
6.6 INSTRUMENT MAINTENANCE/CHECK
Everyday check/maintenance.
1.
Check water level in the cooling tank.
2.
Check Ar gas pressure
3.
Inspect graphite tube for surface contamination and perform furnace cleaning through software.
4.
Fill the rinse bottle with Triton X-100 and nitric acid solution.
5.
Lamp intensity (there shouldn’t be much fluctuation).
6.
Autosampler tip alignment in graphite tube.
Monthly maintenance
1.
Change the fume extraction unit filter.
2.
Calibrate auto sampler pipette by weighing the dispensed volume.

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7. DETERMINATION
GFAAS-Z
Calibration:
Quantitative measurements in atomic absorption are based on the Beer-Lambert law, which states that the concentration of an analyte is proportional to its absorbance:
C = KA = K log I
0
/ I
In this expression C is the concentration, A is the integrated absorbance, I
0
and I are the incident and transmitted source intensities, and K is a proportionality constant. It is well known that for most elements, the observed relationship between concentration and absorbance is not linear over an extended concentration range. For this reason, generally a suitable non-linear curve equation is used to construct calibration plot.
Blanks and samples:
The calibration standards, reagent blank, SEAS system blank, and SEAS samples have the following composition when their solution is placed in the graphite furnace for the analysis of elemental concentration.
Reagent blank SEAS System blank SEAS sample
Matrix modifier +
0.2 % HNO
3
in milliQ water.
Calibration standards
Matrix modifier +
0.2 % HNO
3
in milliQ water +
Appropriate metal ions
Matrix modifier +
0.2 % HNO
3
in milliQ water +
Atmospheric air particles from uncontrollable sources/ temporary contamination from
SEAS instrument
Matrix modifier +
0.2 % HNO
3
in milliQ water + atmospheric air particles
As the volume of the sample injection, and the nature and amount of matrix modifiers remains same for the entire suite of elements, the elemental impurities associated with reagent blank are determined first and stored in the temporary memory of the method data-file of the instrument software. The software automatically subtracts this value for all subsequent measurements performed using this method file. Finally, as is evident from the above table, the actual elemental concentrations (in calibration units) in the atmospheric air particles are obtained by subtracting
SEAS system blank values from SEAS sample values.
Atmospheric concentration of elements:
Assuming the density of the sample slurry produced by SEAS is 1.0 g/ml, elemental mass in the
SEAS sample is obtained by multiplying the concentration of the element (in the calibration units, i.e. ng/ml) by the sample slurry mass (in g). The volume of air sampled is obtained by multiplying the duration of sample collection (in min) by the airflow rate (in m
3
/min). The atmospheric concentration (in units of ng/m
3
) of the element is obtained by dividing the elemental mass by the volume of air sampled.

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GFAAS-Z
Atmospheri c con .
( ng / m
3
)

Con .
of the element sample collection
( ng / ml time (min)
) x volume of x flow rate of the sample ( ml ) air ( m
3
/ min)
 
( 1 )
Propagation of measurement uncertainties
As shown above, the atmospheric concentration of an element is calculated from a combination of experimental quantities such as concentration of the element in the SEAS sample solution, weight of the SEAS sample solution, duration of collection, and air flow rate. If the precision of each quantity is known, then simple mathematical rules can be used to estimate the precision
(random error) of the overall result. These rules are summarized as follows:
1) Linear combination
If the final value, y, is calculated from a linear combination of measured qunatities a, b, c, etc.. by:
Y = k + k a a + k b b + k c c +…
Where k, k a
, k b
, k c
, ..are constants,
Then, the standard deviation of y, y  , is given by y  =

(k a
 a
)
2
+ (k b
 b
)
2
+ (k c
 c
)
2
+ ..
Illustration :
Weight of the sample is obtained by: w sample
= w
(sample+bottle)
– w
(bottle
Therefore,
 w
=

(
 sample+bottle
)
2
+ (
 bottle
)
2
------(2)
Since the precision of the balance at both the measurement places are expected to be the same, we may rewrite the equation-(2) as:
 w
=

2
2) Multiplicative expressions :
If y is calculated from an expression of the type
Y = K ab/cd
Where K is a constant and a, b, c and d are independently measured quantities, then
 y
is given by
 y y 


 a a


2



 b b


2



 c c


2



 d d


2
3) If y is calculated from an expression y = b n , then

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GFAAS-Z
 y
 n
 b b
Based on these expressions, the error in the overall calculation of the atmospheric elemental concentration is derived as: s ac x ac


 s cm x cm


2


 s w x w


2


 s t x t


2
 s f

2 x f
Where, s ac
– standard deviation of atmospheric concentration of any element x ac
– atmospheric concentration value calculated from the expression (1) s cm
and x cm
– standard deviation and mean of elemental concentration obtained from the GFAAS, repectively.
S w
and x w
– standard deviation of analytical balance and weight of SEAS sample, respectively. s t
and x t
– standard deviation and mean of collection duration of SEAS sample, respectively. s f
and x f
– standard deviation and mean of flow rate of the atmospheric air sampled, respectively.
[Note: This approach assumes that there are no systematic errors in the calculation steps.]
Since AX105 is capable of measuring upto 0.1mg level with a precision of less than 5%, the uncertainty at grams level becomes insignificant. Uncertainties from mass flow meter reading and clock are also insignificant when compared to the magnitudes of their measurements. Thus, the overall uncertainty primarily evolves from the analytical platform, i.e., GFAASZ.
8.0 Data Quality Objectives and Indicators
The DQOs for the atmospheric elemental concentration data, generated using field instrument known as SEAS and off-line laboratory analytical platform multielement graphite furnace atomic absorption spectrometer are summarized in Table 1. Formulae for the determination of the DQOs are provided below.
The Data Quality Objectives such as instrument detection limit (IDL), method detection limit
(MDL), accuracy, precision, and data completeness – are presented in Table 1. These objectives are based on the assessment of the information and data that are needed to meet the goals of the supersite program while bearing in mind what is feasible given the current state of resources.
The typical data quality indicators associated with measurements are precision, accuracy, detection limit, completeness and comparability.

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Accuracy
GFAAS-Z
Accuracy of the GFAASZ is determined by the analysis of NIST SRM1640 and/or SRM1643d. It is determined by the following formula
Accuracy (%) = (100*[s-x])/s where s – certified value, and x – mean of the measured value.
New calibration plots are constructed for every batch of analyses (44 samples). SRM samples are analyzed immediately after the calibration. Sample analysis is continued only when the accuracy of the element of interest is within 10%. Goodness of the calibration curves is verified by analyzing a known standard after every 16 samples. Al, Fe and Zn are often found at poor accuracy. This can be attributed to their short-range and non-linear calibration curve fits. Acidity of the test solution plays major role in the determination of Cr and Al. Aged Cr standards show reduced atomic absorption.
Due to the unique research design of SEAS, standards are unavailable to determine its collection accuracy, i.e., the efficiency. Therefore, the following two approaches are employed in order to estimate bias in the final concentration.
1.
Comparison of results with collocated SEAS
2.
Comparison with parallel filter samples
Data acceptance criteria based on these measurements are yet to be evaluated.
Precision
Precision in the determination of elements by GFAASZ is determined from replicate analyses.
For each series of measurements or replicates, the precision (expressed as standard deviation or percent relative standard deviation) is calculated by:
S tan dar deviation ( s )

% RSD
 x s

100 i n 

1
 x
 x

2 i n

1
Where, n - number of determinations, x i
– value of the i-th replicate, x - mean of the replicates s is the standard deviation.
Precision of the sampling air volume is determined by measuring the flow rate every five minutes using a calibrated mass flow meter and recorded in the SEAS control program.
The relative standard deviation of three replicate measurements is generally less than 5% for calibration standards. However, for SEAS sample slurry, RSDs vary depending upon the concentration of elements in the sample slurry. Uncertainty in the determination also arises from the nature of the samples (variance of particle size and the number of particles present in the injected volume) and slurry inhomogeneity due to agglomeration or coagulation. Generally, elements that are present in concentrations 5-10 folds greater than their detection limits have
RSDs <5%, while elements at lower concentrations typically have RSDs of about 10-20%. If
RSD exceeds the set value for an element for which the expected or determined concentration is

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GFAAS-Z well above its detection limit, then instrument malfunction may be indicated.
For reagent and system blanks, RSDs are typically 30 to 40% due to their very low concentrations. System blanks are typically 1 to 10-fold greater than reagent blanks.
Detection Limits
Detection limits arise from both, the instrument that produce samples and from the off-line elemental concentration determination platform.
The instrumental minimum detection limit (IDL) may be defined as a statistically determined value above which the reported concentration can be differentiated, at a specific probability, from a zero concentration. For GFAASZ work, IDL is generally calculated based on several reagent blank determinations using the following formula:
DetectionL imit

3
 s b m where s b
- is the standard deviation of nine instrument blanks, and m – is the slope of the calibration line.
The method detection limit includes field conditions and system blanks. Table 1 lists the MDL for the elements of interest. It should rather be considered as background (temporary contamination in the collection system) plus the variations associated to it.
Completeness
The completeness of the data set is determined as the percentage of samples collected in the duration of interest that met the DQO set for the field instrument. For offline analyses it is always
100% as all of the selected samples are analyzed.
Data Quality Objectives of sub-hourly elemental measurements using SEAS
Element
Al
As
Cd
Cr
Cu
Fe
Ni
Mn
Pb
Se
Zn
IDL (ppb) 3

MDL (ppb)*
1

1.92
0.10
0.13
0.01
0.19
0.62
0.10
0.07
0.02
0.30
0.12
7.2

3.90
0.14

0.11
<0.13
0.12

0.06
0.39

0.27
1.61

0.89
0.32

0.18
0.31

0.51
0.48

0.59
<0.30
1.91

1.5
Accuracy (%)

15

10

10

10

10

10

10

10

10

10

10
Precision

10

5

5

5

5

5

5

5

5

5

5
* Method detection limits presented are from three blanks from four successive weeks of continuous operation of the field instrument (3x4=12 blank samples)

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GFAAS-Z
The UMCP-Analytical chemistry lab will provide sample collection trays with labels, data sheet and numbered clean sample vials.
Batch identification system will have the format: SSSnnnNN
S - site id (FMC, CLM, STL, PIT) n - batch number (001-999)
N – tube number (01-44)
Upon receipt at UMCP, the tray will be placed inside a clean plastic bag, and stored inside cold room, which is maintained at ~5 0 C.
11. DATA STORAGE
All raw and final results including the uncertainty values are stored in the laboratory computer hard drive. In addition to it, there will be a daily backup to CDROM and a weekly redundant backup, which will be stored in B0103, UMCP-Chem.
12. DATA REPORTING
The raw and processed analytical data are reported in electronic media for inspection of the PI.
The analytical report includes the sample id information, analysis date, concentration of each analyte determined (before and after the subtraction of reagent, field and system blanks), and their respective uncertainty levels (as one sigma) in the analyte concentration determination.
13. HEALTHS AND SAFTY WARNING
1.
Anyone wearing electronic heart pacemakers or having other metallic implants should remain at least 0.6 meter away from the furnace (in any direction) while the furnace is operating. The electromagnet generates a strong magnetic field inside furnace during measurement cycles. This could also affect magnetic storage devices, watches and other nearby instruments.
2.
Do not handle any solvents near the furnace.
3.
Ensure that laboratory ventilation is adequate to remove toxic products generated during instrument operation.

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