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Topics Covered
Background
Fluorescence
Spectroscopy Instrumentation
Experimental
Procedures
Results and
Discussion
Background
Automobile-parts production can be paralysed by a defective
electron-galvanizing (EV) bath line. Because a sensitive and accurate analysis
of EV solutions is fundamental to productivity, quality, and identification of
errors, a detailed analytical profile can help trace the source of error and
contribute to selecting the best solution. Both downtime and material cost
therefore can be minimized.
Fluorescence spectroscopy is an analytical technique with
high sensitivity and selectivity. By characterizing the components in the
EV-coat solution with fluorescence, a detailed analytical profile can be formed
for each component. This can help trace the source of errors in the EV-coat
solution, and contribute to selection of the best formulation.
Quality-control tests can be preformed periodically to check
for consistent bath composition.
Fluorescence Spectroscopy Instrumentation
The SPEX® FLUOROMAX® spectrofluorometer was used in this
investigation. The system is compact, economical, and offers several automated
accessories. The FLUOROMAX® is noted for its outstanding sensitivity, speed,
and easy-to-use software.
- High sensitivity is achieved by means of all reflective optics and
photon-counting detection.
- Data acquisition is fast because the system can slew at 160
nm.s–1. Coupling sensitivity and rapid data acquisition creates a
system that can function as an efficient and productive laboratory
instrument.
- Complete experiments can be stored in memory and recalled by a
technician for push-button, menu-driven operation.
Therefore, spectra can be acquired in seconds, and a
time-based scan can be collected at 1 ms/data point. Simplicity is apparent in
the automation, computer-controlled variable slits, software, and calibration.
For convenience, all of the controls are located in the keyboard of a
PC-compatible computer.
Experimental Procedures
Samples obtained for analysis were divided into six segments.
Electro-galvanizing bath (EV) was a sample of the current bath causing problems
for the operator. Sample A is the plating bath that would compose the ideal EV
bath. Sample B is a bath that contains 0.6 mL of starter and 1.5 mL of
brightener. Sample C is a bath that contains 2 mL of starter and 0.5 mL of
brightener. Starter and brightener stock samples were obtained for
comparison.
Results and Discussion
The six samples were characterized by their excitation and
emission spectra shown in Figures 1 through 4. The fluorescence spectra as
determined by the SPEX® FLUOROMAX® spectrofluorometer could offer a possible
method for correctly mixing the appropriate concentrations or proportion of
starter and brightener solutions in the EV bath. For the coating process to
work, a constant level of starter and brightener is necessary.
Figure 1.
Comparison of excitation (left side) and emission (right side) spectra of
Samples A, B, and C, along with electron-galvanizing coat bath (EV). Next to
each trace, the excitation or emission wavelength is given.
Figure 2.
Comparison of excitation (left side) and emission (right side) spectra of
Samples A, C, electron-galvanizing coat bath (EV), and brightener. Next to each
trace, the excitation or emission wavelength is given.
Figure 3.
Comparison of fluorescence excitation (left side) and emission (right side) of
Samples A, C, and a 100-fold dilution of starter solution. Next to each trace,
the excitation or emission wavelength is given.
Figure 4.
Excitation (left side) and emission (right side) spectra of stock solution of
brightener and 100-fold dilution of starter. Next to each trace, the excitation
or emission wavelength is given.
Figure 1 illustrates that sample A was 5 × 105
counts lower in fluorescence intensity than the EV bath. Sample C was
106 counts higher in intensity than the EV bath. Therefore, a
component in sample C must have been the cause of the greater intensity.
Sample C contained the largest amount of starter solution,
the smallest volume of brightener solution. This indicates that the actual EV
bath contained too much starter solution, based on the difference in
fluorescence intensities.
The data were fitted to the following linear equation:
where A, B, and C are constants, [Brightener] is the
concentration of brightener, [Starter] is the concentration of starter, and If
is the observed intensity of fluorescence. An empirical linear relationship thus
was established between the fluorescence intensity and ratio of brightener to
starter.
Source: Horiba Scientific
For more information on this source please visit Horiba Scientific