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SEMI C1-0705 © SEMI 1978, 2005 19 7.9.6 Background C orrection — Whe re spuriou s absorptio n or other backgr ound correction is re quired , details are given in the proce dure for an individual l iquid chemical. For an …
SEMI C1-0705 © SEMI 1978, 2005 18
analysis of cations is a dilute solution of hydrochloric acid in a solution with the appropriate grade of 18.2 Mohm-
cm water that meets ASTM Standard Guide D5127.
7.8.5 Eluent concentration, eluent flow rate, and system pressure are variables, which affect the chromatography.
Each must be determined for the chromatographic system being used.
7.8.6 Detector — A conductivity detector is used to monitor the changes in the eluent conductivity due to ions in
the sample. An ultraviolet absorbance detector can be used for detection of some ions. The detector output, after
amplification, is used to produce the chromatogram, a plot of component quantity versus elution time. Modern
systems digitize the analog output allowing direct printout of peak heights, peak areas, and retention times.
7.8.7 Calculation of Results
Ion Concentration =
Pk. Ht. S
I
= Peak Height of Sample Ion
Pk. Ht. B
I
= Peak Height of Blank Ion
Pk. Ht. Std
I
= Peak Height of Standard Ion
Conc. of Std
I
= Concentration of Standard Ion
Peak area may be used instead of peak height. Calibration linearity must be established before use.
7.9 Determination of Trace Elements by Atomic Absorption Spectrometry (AAS) — The purpose here is to describe
in general terms how the technique should be used when specified in the procedures for an individual liquid
chemical to assure that the specifications for one or more stated elements are met. No general procedure is given
since operating details will vary with instrument design; consequently, the manufacturer’s manual should be
followed.
7.9.1 Equipment — The source is a hollow cathode lamp, or equivalent, for the relevant element. The burner is
slotted and will vary in design and path length according to the gas(es) to be used. The monochromator should have
a resolution of at least 0.1 nm. The signal from the detector is read from a meter, digital display, recorder tracing or
custom software. A background correction system should be available.
7.9.2 Flame and Burner Conditions — The flame gases to be used are specified in the procedure for the individual
liquid chemical. The burner position and gas flow rates should be optimized for a given determination.
7.9.3 Solution Conditions — The solutions are prepared as given in the procedures for the individual liquid
chemical.
7.9.4 Working Standard Solutions — Working standard solutions should be prepared on the day of use by dilution
of a stock standard solution.
7.9.5 Quantitation — Commonly, the method of standard addition is employed. It is applicable at low
concentrations where a linear relationship exists between signal and concentration. By this technique the standards
have a matrix similar to the sample. It is essential that the sample solution, along with the additions, has absorbance
in the range for which linearity is expected: routinely, 0.1 to 0.5 absorbance unit. The use of standard additions does
not eliminate interferences, but assures that the element of interest behaves similarly in the sample preparation and
those with additions. Background correction is usually required, and additives may be called for (see below).
7.9.5.1 For specific tests, the signals are measured for five solution preparations: the reagent blank (which may be
only water), the sample solution, and three made by standard additions to the sample solution. The signal for the
reagent blank preparation is subtracted from the signals for each of the four other preparations. These four signals
are used graphically or mathematically to determine the content of the element in the sample. Where several
elements are to be determined, they are added simultaneously to the third, fourth, and fifth preparations.
Commonly, the additions correspond to one half the specification limit, equal to the limit, and twice the limit.
7.9.5.2 A calibration line obtained for aqueous standards can be used if its slope and the slope of the standard
addition line are identical. In that event, liquid chemical (matrix) effects are negligible.
(Pk. Ht. S
I
Pk. Ht. B
I
) (Conc. of Std
I
)
Pk. Ht. Std
I
Pk. Ht. B
I
Dilution Factor
SEMI C1-0705 © SEMI 1978, 2005 19
7.9.6 Background Correction — Where spurious absorption or other background correction is required, details are
given in the procedure for an individual liquid chemical. For an element with the stated resonance line in the
ultraviolet region (<350 nm), the correction should be performed with a deuterium discharge lamp. For an element
with the stated line in the visible region (>350 nm), the adjacent line technique should be employed. In this method,
the background absorption is determined at a wavelength adjacent, ±5 nm, to the line being used for the element of
interest; that is, it is measured at a wavelength where significant atomic absorption by that element is absent.
Zeeman Background correction may also be used.
7.9.7 Additives — Where additives are included in the solution preparations, including an ionization suppressant,
details are provided in the procedures for the individual liquid chemical.
7.9.8 Remarks — The manufacturer’s manual should be consulted for details on the venting of burner gases and for
safety precautions in the operation of the instrument and burner. The user should check the performance of an
instrument from time to time to assure that adequate sensitivity is being attained for the needs of the particular
determination.
7.10 Determination of Trace Elements by Flame Emission Spectrometry — The purpose here is to describe in
general terms how the technique should be used when specified in the procedures for an individual liquid chemical
to assure that the specifications are met for one or more stated elements (commonly sodium or potassium, or both).
No general procedure is given since operating details will vary with instrumental design; consequently, the
manufacturer’s manual should be followed.
7.10.1 Equipment — The flame photometer should have a monochromator with a resolution of at least 1 nm. The
detector should have a red-sensitive phototube, a filter to remove the sodium D-line for potassium determinations,
and a photomultiplier. (Instruments having a photomultiplier specially sensitive to the potassium line do not need a
red-sensitive phototube.) The slit width must be adjustable. A sensitivity control should be available. Also, the
burner should have controls for adjusting its position and gas flow rates. The read-out device may be a meter,
digital display, or recorder.
7.10.2 Flame and Burner Conditions — The flame gases to be used are specified in the procedure for the individual
liquid chemical. The burner position and gas flow rates should be optimized for a given determination.
7.10.3 Solution Conditions — The solutions are prepared as given in the procedures for the individual liquid
chemical.
7.10.4 Standards — A stock standard solution for each relevant element should be accurately prepared, usually at a
concentration of 0.1% wt/vol, as given either in the procedure for the individual liquid chemical or in §4. Working
standard solutions should be prepared on the day of use by dilution of a stock standard solution.
7.10.5 Quantitation — Commonly, a single addition of standard is employed. It is applicable at low concentration
where a linear relationship exists between signal and concentration. By this technique, the standard has a matrix
similar to the sample.
7.10.5.1 The amount of standard to be added to the sample to make the standard solution is given in the procedures
for the individual liquid chemical, and corresponds to the specification value of the element being determined.
7.10.5.2 For specific tests, the signals are measured for the sample solution and the standard solution. The
instrument is optimized with the standard solution at the wavelength specified. It is then zeroed with water, and the
sample is aspirated into the flame and its signal read. Without changing the slit, the wavelength is changed to a
nearby setting and the background value determined. The difference between the background value and the value
for the sample should not exceed the difference between the values obtained for the sample and standard solutions.
7.10.6 Remarks — The manufacturer’s manual should be consulted for details on the venting of burner gases and
for safety precautions in the operation of the instrument and burner. The user should check the performance of the
instrument from time to time to assure that adequate sensitivity is being attained for the needs of the particular
determination.
7.11 Determination of Trace Elements by Graphite Furnace Atomic Absorption Spectrometry — The purpose here
is to describe in general terms how the technique should be used when specified in the procedures for an individual
liquid chemical to assure that the specifications for one or more stated elements are met. No general procedure is
given since operating details will vary with instrument design; consequently, the manufacturer’s manual should be
followed.
SEMI C1-0705 © SEMI 1978, 2005 20
7.11.1 Equipment — The source is a hollow cathode lamp, or equivalent, for the relevant element. The furnace will
contain a pyrolytic coated graphite tube that has been conditioned according to manufacturer’s instructions. The
monochromator should have a resolution of at least 0.1 nm. The signal from the photomultiplier tube detector is
read from a meter, digital display, or recorder tracing. Zeeman or deuterium background correction can be used. An
autosampler is suggested in order to obtain better reproducibility.
7.11.2 Operating Conditions — Use an acceptable flow rate (300 mL per minute) argon as the inert carrier gas,
with no flow during the atomization portion of the program. The temperature programs outlined by the instrument
manufacturers should be checked using known standards, and adapted as necessary for optimum performance for a
specific instrument. Calibrate the temperature controller for the different atomization temperatures used for each
element. The conditions for iron, potassium, calcium, and sodium are included in Table 9.
Table 9 Conditions for Graphite Furnace Atomic Absorption Spectrometry
Element Iron Potassium Calcium Sodium
Wavelength (nm) 248.3 766.5 422.7 589.1
Bandwidth (nm) 0.2 1.4 2.0 0.2
Current (mA) 30 6 8 8
L’vov Platform Yes Yes Optional Yes
Sample Size (µL) 20 10 10 10
7.11.3 Solutions Conditions — The solutions are prepared as given in the procedures for the individual liquid
chemical. All solutions will be prepared in a clean environment as defined in the SEMI guidelines.
7.11.4 Working Standard Solutions — Working standard solutions should be prepared on the day of use by dilution
of a stock standard solution.
7.11.5 Sample Preparations — Sample preparation will be analyzed neat, with pre-concentration, or by dilution,
according to the individual procedure.
7.11.6 Quantification — Results shall be reported as the result of three replicate analyses. Each replicate is the
result of an 8-second integration of the peak area with the instrument in concentration mode. Recording should
commence 5 seconds before the atomization, and baseline should be established 2 seconds prior to atomization.
Reading should commence 1 second prior to atomization. Alternate integration schemes for the analytical peak shall
be performed in a manner that captures all of the signal, as appropriate for the instrument.
7.11.7 Calibration — Calibrate the instrument using a standard prepared in the appropriate grade of 18.2 Mohm-cm
water that meets ASTM Standard Guide D5127, over a concentration range appropriate for the analysis. The blank
must also be contained in the appropriate grade of 18.2 Mohm-cm water that meets ASTM Standard Guide D5127.
7.12 Determination of Trace Elements by Inductively Coupled Plasma Optical Emission Spectrometry
(ICP-OES) — The purpose here is to describe in general terms how the technique should be used when specified in
the procedures for an individual liquid chemical to assure that the specifications for one or more stated elements are
met. No general procedure is given since operating details will vary with instrument design; consequently, the
manufacturer’s manual should be followed.
7.12.1 Equipment — A spectrometer with sufficient resolution to separate the typical spectral lines of the elements
stated in the specification for an individual liquid chemical. The signal from the detector is processed by a computer
system and displayed on a recorder with graphics capability. A background correction technique is required.
Typical emission lines are listed in Table 10.
Table 10 Suggested Plasma Emission Line
Element Symbol Line (nm)
Aluminum (Al) 396.15
Antimony (Sb) 206.83
Arsenic (As) 193.76
Barium (Ba) 455.40