Page 14 - Shimadzu AA-7000

Dual-Background Correction Functions

The optimal background correction methods are installed as standard:
high-speed self-reversal method (SR method) and deuterium lamp method (D2 method).

These functions can correct for spectral interference in flame measurement.
Selecting the optimal background correction method for each sample ensures
accurate and reliable analysis results.

Samples suitable for the SR method Samples suitable for the D2 method

Samples with a complex matrix Purified water, tap water, environmental water, etc.
(Containing a large quantity of a specific element as the main component) Samples with a relatively simple matrix

SR (high-speed self-reversal) method –– accurate background correction over a wide range

Features
1. High-speed self-reversal (SR) correction is generally more accurate than deuterium lamp (D2) correction. As both atomic absorption and background
absorption can be measured using a single lamp, the correction errors due to light-axis misalignment are extremely small. This is ideal for the quantitation
of trace components in a matrix exhibiting complex background absorption, such as bio-samples and metals.
2. Permits background correction over the entire wavelength range from 185 nm to 900 nm.
3. This method can correct for spectral interference due to neighboring lines that can occur when a resonance line for another element exists near the
analytical line for the target element. (See table on next page.)
4. As no polarizer is used, measurements are possible with low light losses and a high S/N ratio.
5. The rapid lamp lighting permits accurate measurement unaffected by emission noise in the atomizer.
* Hollow cathode lamp L-2433 is required to use the SR method. Hollow cathode lamp L-2433 can also be used for the D2 method.
Background absorption Principle
IH spectrum
Background A small current IL (approx. 10 mA) and a large current IH (approx. 500
Atomic absorption mA) are alternately passed through the hollow cathode lamp. The
Atomic lamp emission spectrum when the large current flows has a depression
Lamp current Wavelength Wavelength Atomic in the center (self-reverse), due to self-absorption of the large number
absorption
IH
of sputtered atoms in the atom cloud, as shown in the diagram to the
IL
layer
IL spectrum Absorption absorption left. No significant atomic absorption is apparent and background
absorption mainly occurs. Conversely, the lamp emission spectrum
Background
when the small current flows comprises a single narrow peak resulting
Time from both atomic absorption and background absorption. By
Atomic absorption
determining the difference between the two types of absorption, it is
possible to accurately correct for the background absorption and
(Lamp energy) (Sample measurement) (Energy component ratio)
measure the true atomic absorption.
Examples suitable for SR method (where differences result between SR and D2 methods)
Example: Measurement of trace levels of zinc in iron (analysis of Zn in Fe solution)
BGC-SR method BGC-D2 method
Zn 0.25ppm
Atomic absorption signal
Background signal Atomic absorption signal Zn 0.50ppm
Background signal
Fe 0.1%
Fe 0.5%
Fe 0.5% Zn 0.25ppm
Fe 0.5% Zn 0.5ppm
Fe 0.75% Zn 0.3ppm
The identical 0.5 ppm Zn solution is accurately corrected to Due to inadequate correction, the absorbance is higher at
the same absorbance at (2) and (6). (6) than at (2) for the identical 0.5 ppm Zn solution.

14
Downloaded from www.Manualslib.com manuals search engine