Coal quality characterization: 
Analytical methods
Curtis Palmer
Brenda Pierce
Carol Skeen
Kris Dennen
Frank Dulong
U.S. Geological Survey,
956 National Center, 
Reston, Virginia 20192 USA

Sample collection and 
preservation
Brenda S. Pierce
U.S. Geological Survey,
956 National Center, 
Reston, Virginia 20192 USA

Quality of resultant data
directly dependent upon:
-Sample collection
-Sample preparation
-Analytical technique

Three American Society for 
Testing Materials (ASTM) 
standards currently exist for 
collection of coal samples:
-ASTM practice for collection of channel 
samples of coal in the mine (D 4596)
-ASTM test methods for collection of a gross 
sample of coal (D 2334)
-ASTM practice for collection of coal samples 
from core (D 5192)

Most important criteria:
Sample be representative
of the coal bed

Representative samples are 
difficult to obtain:
Coal beds are heterogenous 
both vertically and laterally
-physically
-petrographically
-chemically

Valid laboratory analysis 
dependent upon proper 
sampling and subsequent 
sample handling.

Type and Nature of Samples 
Dependent Upon:
-Purpose of collecting samples
-Types of analyses to be performed
-Use of data

For example:
For rank determination -
-Noncoalpartings > 1 cm thick and
-Mineral occurrences >1.27x5 cm must 
be removed from sample

Different Types of Samples
-Cuttings samples
-Channel samples
-Drill core samples

Cuttings Samples
(rotary drilling):
Should be collected at regular 
depths, rather than at regular 
times, because drilling times 
vary in different lithologiesand 
lag times vary with depth and 
penetration rates. 

Cuttings for Coal Samples:
Not representative of the bed, 
but can be used for vitrinite 
reflectance 

Drill Core and Channel Samples
Level of sampling detail dependent 
upon intended use
May Sample:
-Whole core
-Only coal, excluding partings >x thickness, 
depending on final research or technological need
-Regularly sampled intervals
-Facies(determined by visual inspection, x-
radiographs, geophysical logs)
In most cases, primary sampling criteria should be 
lithologic (coal type) changes
Core recovery is an important consideration


Coal bed facies:
(Sometimes called benches, 
intervals)
-Developmental units in the peat mire
-Laterally continuous
-Unique characteristics
-Better able to model a coal bed using 
facies analysis

Partings:
-Perhaps the single most 
confusing component in a coal 
sampling protocol
-When subsampling a single coal 
bed, best to sample and analyze 
all partings separately

Considerations when 
determining sampling scheme:
-Intended use of data
-Coal quality analyses to be run
-Well thought out sampling scheme
-Minimum sample mass 
-Sample handling (moisture 
loss/oxidation) 
-Detailed careful descriptions
-Careful sampling technique, to 
avoid any type of contamination

Methods Overview and 
Relative Merits
Curtis Palmer
U.S. Geological Survey,
956 National Center, 
Reston, Virginia 20192 USA

Text Box: Analytical Methods Overview and Relative Merits 
-Methods to be covered in this course 

(Elemental Analysis)
-Routine Methods
	--Multi-Element Techniques
		-Inductively Coupled Plasma-Atomic Emission Spectroscopy(ICP-AES)
		-Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS)
	Single Element Techniques
		-Cold Vapor Atomic Absorption (CVAA; Hg)
		-Hydride Generation Atomic Absorption (HGAA; Se)--Non-Routine Methods
	--X-Ray Florescence Analysis (XRF)
	--Instrumental Neutron Activation analysis (INAA)

-Methods to be covered in this course
(Mineral Analysis)
-Low Temperature Ashing
-X-Ray Diffraction Analysis

-Other Methods (not covered in this course)
-ASTM Methods
-Modes of Occurrence Analysis
-Ion Chromotrography
-Optical Spectroscopy
-Flame and Graphic Furnace Atomic 
Absorption Analysis
-Microbeam Anaysis-Energy dispersive 
and wavelength

-X-ray Absorption Fine Structure (XAFS) 
-X-ray Absorption Near Edge Structure 
(XANES)
-Proton induced X-ray Excitation (PIXE)
-Classic (Wet) Chemical Techniques
-Organic Analysis
-Thermal Analysis
-Etc.

-Sample Preparation:To Ash or Not to Ash
-Advantages of Ashing
-Increases concentration and apparent detection 
limits
-Makes it easier to place many elements into solution
-Ash is more stable for long term storage (Archiving)
-Can improve homogeneity

Text Box: Disadvantages of Ashing
-Some elements may volatilize 
-Volatility may be matrix dependent
-Amounts volatilized may be different for each sample and element
-Occasionally elements not normally considered volatile are volatile for a given sample
-Potential of cross-contamination of volatile components
-Larger sample needed
--Additional steps and time
-Elements may need to be recalculated to a whole coal basis
-Care must be taken to ensure ashing is complete
-Mechanical losses can effect results

-Ashing Procedure--USGS
-Samples heated from 25oC to 200oC in about 1 hour 
-Samples heated at 200oC for 1.5 hrs 
-Temperature increased to 350oC  and held 2 hrs 
-Temperature increased to 525oC and held 36 hrs 
-Samples slowly cooled (1-2 hr)
-Samples examined and re-ignited at 525oC if necessary -Samples homogenized


Text Box: 
Text Box: Methods requiring ashing
-ICP-AES
-Advantages
-Rapid
-Low Cost
-Multi-element
-Disadvantages
-Requires dissolution of ash
-Moderate sensitivity

-Two dissolution procedures (sinter and acid digest)
-Sinter (Ash fused at 445oC with Na2O2)
-Advantages 
--Dissolves species difficult by acid dissolution 
--Conserves volatile elements during acid dissolution -Disadvantages 
--High dissolution ratio reduces sensitivity 
--High salt content can cause instrument problems 
-Elements Determined 
--Major elements in ash except Na 
--Trace elements: B, Ba, Zr 


Text Box: 
-Acid Digest
-Advantages
--Low dissolution ratio--Higher sensitivity
--Low salt content no Na contamination
-Disadvantages
--Some elements are volatile, eg. B, Se, 
Cl
--Some elements are associated with 
insolubleminerals, eg.Zr, Ba
-Elements Determined
--Major element: Na2O
--Trace elements: Be, Co Cr, Cu, Li, 
Mn, Ni, Sc, Sr, Th, V, Y, Zn

-ICP-MS
-Much higher sensitivity (10 to 1000 times)
-Higher cost instrument
-Some elements have interferences-poorer 
results than ICP-AES; Others similar results to 
ICP-AES
-Same dissolutions as ICP-AES but sinter 
dissolution is not routinely analyzed because the 
use of the highly ionic solution requires special 
setup and require additional maintenance
-Acid digest: Ag, As, Au, Bi, Cd, Cs, Ga, Ge, Mo, 
Nb, Pb, Rb, Sb, Sn, Te, Tl, U
-Sinter: 13 Rare earth elements,Hf, Ta and W 

Text Box: X-Ray Florescence Analysis (energy dispersive and wavelength dispersive XRF)
-Advantages
-Quick Non-Destructive technique
-Qualitative and Quantitative Multi-element Method 
-No dissolution needed; Fused pellets give more precise results for some elements eg. major elements. 
-Total cost - low to moderate usually less than ICP-AES 
-Disadvantages
-Low to moderate sensitivity
-Matrix Dependent
-Elements include: Major ash elements, Cr, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, and others if concentration is high enough.
-Elements that can be determined and sensitivity depend on instrument power and design which is a function of the cost.

Text Box: Whole Coal Techniques
-Cold Vapor Atomic Absorption (CVAA)
-Single element (Hg)
-Requires dissolution
-5 to 10 percent of Coals below detection limit of 0.02 ppm 
-Reliable and accurate (ASTM method)

-Hydride generation atomic absorption (HGAA)
-Single element (Se) 
-Requires dissolution
-Several elements (especially heavy and transition 
metals)in high concentrations can interfere with results
-Instrumental neutron activation analysis (INAA)
-Time consuming multi-element technique 
-Highly linear - few interferences
-Small sample size
-No ashing or dissolution required 
-High sensitivity
-High cost - requires nuclear reactor 
-Elements include: Na, K, Fe, Sc, Cr, Co, Ni, Zn, As, Se, Br Rb, Sr, Mo, Sb, Cs, Ba, La, Ce, Nd, Sm, Eu, Tb, Yb, Lu, Hf, Ta, W, Th, U
-Other elements possible Al, Ca, Mg, Ti, S, V, Cl, I, Mn, Dy, Hg

Text Box: References
Visit our web site: energy.er.usgs.gov/products/papers 
-Click Palmer, C.A., 1997, The chemical analysis of Argonne Premium Coals: U.S. Geological Survey Bulletin 2144 or enter energy.er.usgs.gov/products/papers/B2144
-Click Golightly, D.W., and Simon, F.O., 1989, Methods for Sampling and Inorganic Analysis of Coal: USGS Bulletin 1823 or enter energy.er.usgs.gov/products/papers/B1893
-Click Swanson, V.E. and Huffman, C., Jr. 1976, Guidelines for sample collecting and 
analytical methods used in the U.S. Geological Survey for determining chemical 
composition of coal: United States Geological Survey Circular 735 or enter energy.er.usgs.gov/products/papers/C735


Chemical Characterization of Coal using Cold-Vapor and Hydride-Generation Atomic Absorption and Inductively Coupled Plasma Atomic Emission Spectroscopy and Mass Spectroscopy

Carol Skeen
U.S. Geological Survey,
956 National Center, 
Reston, Virginia 20192 USA

Introduction 
-Description of sample preparation and the 
basics of the instruments used to obtain 
data.
-Provide understanding of the advantages 
and limitations to each technique.
-A multi-technique approach for major and 
trace element analysis provides the data 
to characterize coal quality.

Agenda
-Sample Preparation
-Quality Control and Quality Assurance
-Cold Vapor Atomic Absorption Spectrometry
-Hydride Generation Atomic Absorption 
Spectrometry
-Inductively Coupled Plasma/Atomic Emission 
Spectrometry
-Inductively Coupled Plasma/Mass 
Spectrometry

Sample Preparation using 
pulverized whole coal
For Mercury (Hg) determination method:
-Digest 0.15 gm with nitric acid, sulfuric acid 
and vanadium pentoxide.
For Selenium (Se) determination method:
-Digest 0.1 gm using nitric acid, sulfuric acid 
and perchloric acid.
-Form a hydride by the addition of sodium 
borohydride.

Sample Preparation using coal ash
Multi-acid digestion for multi-element determination:
-Digest 0.2 gm of ash using hydrochloric acid, nitric 
acid, perchloric acid, and hydrofluoric acid.
-Final volume is 20 ml for use in the ICP-AES.
-Take a 2 ml aliquot of the acid digest and bring to 
10 ml volume for use in the ICP-MS.

Sample Preparation using coal ash
Sinter for multi-element determination:
-Place 0.1 gm of ash in a graphite crucible
-Mix ash with sodium peroxide
-Ash in a muffle furnace at 445oC
-Place sinter in 20 ml of deionizedwater to dissolve.
-Add 20 ml of 15% nitric acid
-Use final solution for both ICP/AES and ICP/MS

Quality Control & Quality Assurance
Accuracy -degree of agreement between the 
measured value to the ŅtrueÓ or proposed value
-Standard Reference Materials
1.CLB-1 -coal
2.NIST 1632b -coal (bituminous)
3.NIST 1633a -coal fly ash
-Certified Calibration Standards
Precision -degree of agreement between 
measured values under repetitive testing of a 
sample; reproducibility of results
-Duplicate samples

Instrumentation criteria guideline 
definitions:
Detection Limits-
-Lowest concentration of an analysis that is 
statistically different from the analytical blank.
-Detection limit ranges vary among instruments.
-Low detection limits usually are desired, but 
applications determine the detection limit needs. 


Instrumentation criteria guideline definitions
[Graph showing typical detection limit ranges (in ppb)
where CVAA= Cold vapor atomic absorption; HGAA =hydride generation atomic absorption; 
ICP/MS= inductively coupled plasma-mass spectroscopy]

Instrumentation criteria guideline definitions 
[Graph showing typical detection limit ranges (in ppb) - (ICP/AES)]

Instrumentation criteria guideline definitions 
Analytical Working Range -The concentration range over 
which quantitative results can be obtained; i.e., the 
linearity response range
[Graph showing signal versus concentration of analyte]

Instrumentation criteria guideline definitions
Analytical Working Ranges
[Graph showing CVAA, HGAA,ICP/AES, and
ICP/MS versus orders of magnitude]

Instrumentation criteria guideline 
definitions:
-Sample Throughput -Number of samples 
or elements determined per unit of time.
-Interferences -Effects of responses of 
the analytical sensor due to solution 
constituents other than analyte.

Text Box: Atomic Absorption Spectrometry (AAS)
Definition -an analytical technique based on the absorption of radiant energy by atoms.
-Atoms introduced to a source of energy remain in ground state.
-When a beam of light radiation passes through the energy source, ground-state atoms having the same wavelength absorb the radiation.
-Absorbed radiation is characteristic and  proportional to the concentration of specific atoms.




Atomic Absorption Spectrometry -
Schematic Diagram of the Principle
[Graphic showing movement from a lamp through an energy source and a monochromator into a detector]

Cold Vapor Atomic Absorption 
Spectrometry for Mercury Analysis
Reason for use of CVAA technique in 
determination of Hg-
-Due to volatility of mercury compounds, coal 
must ashed without the use of high temperatures.
-Then it must be chemically reduced to its 
elemental state as a vapor. 

Cold Vapor Atomic Absorption 
Spectrometry for Mercury Analysis
-Detection Limit -0.01 ppb in solution.
-Analytical Range -Two orders of magnitude 
which covers most concentrations in coal.
-Sample Throughput -Three to five min per single 
element (Hg) per sample.
-Interferences and Compensations -Samples with 
concentrations >10 ppm of Ag and Se can cause a 
suppression of the recovery of Hg. Dilution of the 
sample eliminates this problem.

Hydride Generation Atomic Absorption 
Spectrometry for Selenium Analysis
Reason for use of HGAA technique in 
determination of Se -
-Due to volatility of selenium compounds and need for 
chemical separation, coal must be ashedwithout the 
use of high temperatures.
-It must be chemically reduced to a suitable oxidation 
state.
-For separation from matrix, a hydride species of Se is 
formed into a vapor.

Hydride Generation Atomic Absorption 
Spectrometry for Selenium Analysis
Detection Limit - 0.1 ppb in solution.
Analytical Range-Two orders of magnitude 
which covers most concentrations in coal.
Sample Throughput-Five to ten minutes per 
sample.
Interferences and Compensations-
-High concentrations of certain transition and 
heavy metals cause interference. Sample 
dilution eliminates this problem.
-As concentrations >Se cause masking by 
arsenic hydride. Dilution or instrument 
modification are solutions to problem. 

Inductively Coupled Plasma (ICP)
Definition -
-Device as an excitation source.
-Creates a plasma (about 10,000 
K) generated by inducing a 
magnetic field with argon gas.

Inductively Coupled Plasma/Atomic 
Emission Spectrometry -Schematic 
Diagram of the Principle
[Diagram showing how atomic emission spectrometry works]

Atomic Emission Spectrometry
Definition-
-Analytical technique based on the emission of 
radiant energy by atoms.
-Free atoms excited by a source of energy.
-Excited atoms return to ground state.
-Atoms emit a characteristic radiation with 
intensity proportional to the concentration of the 
atoms.

Inductively Coupled Plasma/Mass Spectrometry 
-Schematic Diagram of the Principle
[Diagram showing movement of axial or radial plasma through a monochromator into a detector]

Inductively Coupled Plasma/Atomic 
Emission Spectrometry
-Detection Limit -0.02 to 0.1 ppm in solution 
depending upon the element and particular 
instrument. (Note: Axial provides better 
detection than radial but radial may be better for 
elements of high concentrations; see previous 
diagram for explainationof terms).
-Analytical Range -Five to six orders of 
magnitude.

Inductively Coupled 
Plasma/Atomic Emission 
Spectrometry
Sample Throughput-
-Three to five minutes/sample for 14 elements in 
acid digest solution.
-Three to five minutes/sample for 11 elements in 
sinter decomposition solution (not routinely 
done). 

Dissolution methods used for the detection of elements
by inductively coupled plasma-mass spectroscopy
[Chart showing acid digest solution and sinter decomposition solution]

Inductively Coupled 
Plasma/Atomic Emission 
Spectrometry
Interferences and Compensations
-Spectral interferences overcome by 
interelement correction factors and background 
factors.
-Matrix effects negated by proper matching of 
standard and sample matrices.

Mass Spectrometry
Definition-
-Analytical technique based on determination of mass 
to charge ratio of ion.
-Molecules broken into charged particles; separated 
by magnetic field generated by radiofrequency.
-Molecule fragments strike electron-emitting surface 
generating electrical signal.
-Relative numbers of ions specific for given 
compounds (including isomers and organic mixtures).

Inductively Coupled Plasma/Mass Spectrometry -
Schematic Diagram of the Principle 
[Graphic showing movement of axial plasma through a mass spectrometer into a detector]

Inductively Coupled 
Plasma/Mass Spectrometry
Detection Limit-0.5 to 50 ppb in solution 
depending upon the element.
Analytical Range-Six to eight orders of 
magnitude.

Inductively Coupled 
Plasma/Mass Spectrometry
Sample Throughput-
-Five to seven minutes/sample for 17 elements 
in acid digest solution.
-Five to seven minutes/sample for 16 elements 
in sinter decomposition solution. (Note: 
Instrument reconfiguration for determination in 
sinter solution.)

Dissolution methods used for the detection of elementsby inductively coupled plasma-mass spectroscopy
[Chart showing acid digest solutions and sinter decomposition solutions]

Inductively Coupled 
Plasma/Mass Spectrometry
Interferences and Compensations
-Isobaric overlap of elemental isotopes and 
molecular ions overcome by alternate isotopic 
masses.
-Matrix effects negated by matching of standard 
and sample matrices and use of internal 
standards.

Other Criteria to Consider in the Selection of Analytical 
Techniques for elemental analysis of Coal 
[Graph showing the cost of the various techniques]

Other criteria to consider in the selection 
of analytical techniques for elemental 
analysis of coal 
Cost versus value:
-Single element vs. multi-element
-Ease of use
-Reliability
-Ability to handle coal matrices

Summary
-Multi-element techniques provide methods for 
generation of large and varied data in short 
time.
-Cost of instruments for multi-element 
techniques can be high.
-Concentrations of some elements in coal 
canÕt be determined using multi-element 
techniques due to volatility and problem 
matrices and other techniques such as AA 
must be used.

X-Ray Fluorescence (XRF) 
Spectrometry
Kris Dennen
U.S. Geological Survey,
956 National Center, 
Reston, Virginia 20192 USA

X-Ray Fluorescence (XRF) 
Spectrometry
A brief overview of qualitative and 
quantitative XRF analysis of
coal and coal ash
 
Methods Used by the USGS
Currently --qualitative, +20 percent: 
-Energy dispersive X-ray fluoresce : 
Whole coal, whole coal powder, coal 
ash, fly ash 
In the past --quantitative, +5 percent:
-Wavelength dispersiveX-ray fluoresce: 
Major elements as oxides --coal ash 
(fluxed into glass disks) 
-Energy dispersivex-ray fluorescene: 
Trace elements (powders)

Accuracy and Precision of XRF
Depends on:
-Sample surface and composition
-Similarity in composition of standards to 
samples
-Number and level of background 
interferences and elemental overlaps

Minimum Detection Limits (MDL)
-Atomic numbers (N) < 11 (Na) are 
generally not detected
-MDL can be as low as two -five mg/g 
for elements having N > 26 (Fe)
-MDL for Al (N=13) andSi(N=14) is 
approximately 100-200 mg/g
-MDL for low N elements such as Na is 
approximately 2000 -3000 mg/g 

Techniques used in XRF 
Spectrometry
Acquiring optimized spectra
-Sample preparation
-Acquisition parameters
Making sure the concentrations are valid
-Choice of standards
-Mathematical methods

Quality of XRF Spectra -Sample 
Prep
An appropriate sample preparation 
method deals with:
-Sample surface -smooth
-Concentration ->MDL
-Particle size -homogeneous and ~ 80 
mesh

Quality of XRF Spectra -
Acquisition Parameters
-Excitation conditions: 1.5 times the 
energy of analyteline
-Vacuum or helium flush -background
-Use of filters and secondary targets -
overlaps
-Counting time = square root of 
concentration

Quality of Calculations -Choice of 
Standards
Reference standards are critical to the 
success of XRF analysis
-Must have same matrix as samples
-Three to four standards per element is 
best
-Concentrations of elements must vary 
independently

Quality of calculations -
mathematical methods
For quantitative analysis:
-Simple linear regression analysis
-Matrix correction algorithms
For qualitative analysis:
-Standardless fundamental parameters
-Pattern matching

Quantitative XRF Analysis of 
Coal Ash
-Widely available silicate rock reference 
standards are used for every element 
excluding sulfur (coal ash has higher S 
content than most rocks)
-Fused glass disks are used for major 
element analysis

Preparation of Coal Ash Samples 
for XRF Analysis
-Use sample ground to 80 mesh
-Mix one part sample with nine parts 
lithium tetra-borate flux
-Fusion at 1100oC to 1200oC 
-Cast in Pt-Au mold 

Advantages of Coal Ash Glass Disk
-Smooth surface
-No particle size problems
-Homogenous
-1:9 dilution means no matrix correction 
necessary

Disadvantages of Coal Ash 
Sample Fusion
-1:9 dilution makes trace element 
analyses impractical
-Volatile elements (Na and S) can be lost 
during fusion (in addition to other 
volatile elements that may be lost during 
required ashingof the sample)
-Extra steps and time involved

Preparation of Whole Coal for 
XRF Analysis
-Loose powders are placed in disposable 
containers on transparent film and 
covered with vented tops for running 
under vacuum
-Pellets are prepared from whole coal or 
whole coal plus a binder

Advantages of Whole Coal 
Sample Preparation
-Fast, easy and inexpensive
-Pressed pellets provide smooth surface
-Volatile elements can be determined
-Loose powder samples can be 
recovered and analyzed by other 
techniques

Quantitative XRF Analysis of 
Whole Coal
-Major constituents of whole coal (C, H, 
N, O) must be determined by other 
methods (eg. pyrolysis)
-Must have whole coal reference 
standards
-Major element analysis is used in 
mathematical correction algorithm

Why Quantitative of Whole Coal XRF 
Analysis Is Difficult
-Certified primary whole coal reference 
standards are not widely available (6 is 
not enough)
-Only a few elements have certified 
values in some reference standards 

When to Use XRF Spectrometry 
with Coal
-To quickly group samples for further 
analysis or analysis by other means
-Qualitative analysis of irreplaceable 
samples. (Method is non-destructive)
-Quantitative analysis of coal ash 


Text Box: Low temperature ashing (LTA)
X-ray Diffraction (XRD) 
Frank Dulong
U.S. Geological Survey,
956 National Center, 
Reston, Virginia 20192 USA

Low temperature ashing (LTA)
-Combustion of organic 
matter at low 
temperature: <100”C
-Radio frequency 
induced oxygen 
plasma under vacuum

[Photograph of low-temperature oxygen plasma asher]
This is a low-temperature 
oxygen plasma asher

Sample preparation and 
handling
-Rock and coal ground to 95 percent <200 
mesh (75µm)
-Pre-weighed 3 inch (7.6 cm)petridish
-Weigh and stir samples every 6 to 8 hours
-Gravimetric determination of percent ash

X-ray Diffraction (XRD)
[Photograph of laboratory set-up]
-Qualitative determination of major phase mineralogy
-Search- Match software compares unknown peaks to standards



X-ray Diffraction (XRD)
[Photograph of laboratory equipment]
-Semi-quantitative major phase determination ±five percent for crystalline phases  greater than five  percent
-Internal standard
-External standard

Sample Mounting
[Photograph of laboratory equipment]
-Powder -Top and 
side loading
-Pressed disk
-Slide slurry

Instrumental neutron 
activation analysis (INAA)
Curtis Palmer
U.S. Geological Survey,
956 National Center, 
Reston, Virginia 20192 USA

INAA (Instrumental Neutron 
Activation Analysis )
-Advantages
-Non-destructive
-Whole coal method (No ashing needed)
-No dissolution needed
-Small sample size possible
-Low detection limits
-Multi-element
-Extremely precise and highly accurate
-Very large linear range 

INAA (Instrumental Neutron 
Activation Analysis )
-Disadvantages
-Very slow-sometimes takes up to three 
months for a single analysis
-Not compatible for most major elements
-Costly
-Requires a nuclear reactor
-Requires working with radioactive material
-A single element with very high 
concentration can reduce sensitivity for 
many other elements

-Analytical Method
-Small sample (300 mg) doubly sealed in 
polyethylene vials (Samples to 10 mg 
possible)
-Samples and standards generally 
irradiated together in nuclear research 
reactor for eight hours. 
-Gamma rays from samples and standards 
are counted on a germanium detector
-Different elements emit gamma rays of 
different energies, often more than one 
peak 

-Typical INAA spectrum (channel 
number is proportional to energy)
[Graph showing number of counts versus channel number]

--Several different spectra for each sample and standard are collected  at different times
--For elements with half lives greater than 12 hrs
	-First count (1 hour) at three to five days after completion of eight hour irradiation 
	-Second count (1hour) at 17-19 days after the irradiation 
	-Third count (two hours) at 60 days after the irradiation
 --For elements with half lives less than 12 hour 
	-First count after 10 minutes after irradiation of 10  minutes
	-Second count 30 minutes to one hour after irradiation of 10 minutes

Text Box: 
-Up to 40 elements can be detected in 
coal 
-Usually, about 30 are detected in 
routine analysis (elements with half lives 
greater than 12 hours)
-Usually, detection limits are from a few 
ppm to about 1 ppb

-Complex spectra are analyzed by 
computer
-Overlapping peaks are resolved or 
software corrected using ratios of peaks
-Net area of each peak is calculated
-Samples and standards are corrected for 
differing decay times depending on the half 
life of the element


