Qualitative Analysis of Pb Liquid Sample Using Laser- Induced Breakdown Spectroscopy (LIBS).

Qualitative analysis of Pb liquid sample using laser-induced breakdown
spectroscopy (LIBS)
Hery Suyanto, Ni Nyoman Rupiasih, T. B. Winardi, M. Manurung, and K. H. Kurniawan
Citation: AIP Conf. Proc. 1555, 14 (2013); doi: 10.1063/1.4820982
View online: http://dx.doi.org/10.1063/1.4820982
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Qualitative Analysis of Pb Liquid Sample Using LaserInduced Breakdown Spectroscopy (LIBS)
Hery Suyanto1*, Ni Nyoman Rupiasih1, Winardi T. B1, M. Manurung2, and
K. H. Kurniawan3
1

Physics Department, 2Chemistry Dept, Faculty of Mathematics and Natural Sciences, Udayana University.
Kampus Bukit Jimbaran, Badung, Bali, Indonesia 80361
3
Research Center of Maju Makmur Mandiri Foundation,
40 Srengseng Raya, Kembangan, Jakarta Barat 11630, Indonesia
* Email : hery6@yahoo.com

Abstract. Qualitative analysis of liquid sample containing 1,000 ppm of Pb was performed by using LIBS technique. In
order to avoid splashing off of the liquid sample during laser irradiation, a sample pretreatment was done, namely the liquid
sample was absorbed by using commercial available stomach medicine. Two kinds of absorbent materials were chosen in
this experiment, first containing 125 mg activated carbon and second 600 mg activated attapulgite. These absorbent
materials were used since carbon sample gives better absorption of infrared laser irradiation used in this experiment. In
order to characterize the absorption process, three treatments were conducted in this experiment; first, without heating the
sample but varying the absorption time before laser irradiation; second by varying the heating temperature after certain time
of absorption process and third by varying the temperature only. The maximum emission intensity of Pb I 405.7 nm was
found in the second treatment of heating the sample till 850C after 30 minutes absorption of the liquid sample in both
absorbent materials.
Keywords: liquid sample, laser-induced breakdown spectroscopy (LIBS), absorbent material, emission spectroscopy
PACS : 52.38.Mf

and Na with lowest detection limits (LOD) of 1 and 2
μg ml-1 respectively, while slightly higher LOD values
(1.2 and 2.5 m ml-1 ) were determined for the same
elements in the mixed solution. However, this
experiment is very difficult to apply for analyzing a
small amount of solution sample (in the order few
ml).
Another researcher [2-5] used another method,
namely a third harmonic Nd:YAG laser (355 nm, 5 ns)
with 10 Hz repetition rate and energy of 35 mJ was
focused through a 10-cm focal length quartz lens onto
the microdroplets generated by a 3 kV electrospray
ionization needle. The lowest detection limit used in
this method is 1.5 mg L-1. This experiment is slightly
dangerous since a high voltage was applied in the
sample side and also need a lot of sample solution to
be investigated.
This study was done by utilizing an absorbent in
which small amount of liquid sample was dropped on
the absorbent surface and the laser irradiation was

then directed to the absorbent surface containing
sample solution to be analyzed; thus no splashing off
of the liquid sample. The emitted plasma light was
then sent to the multichannel spectral analyzer with
working distance from 200 to 980 nm.

INTRODUCTION
The interaction between laser light with various
materials and the characteristics of the plasma have
been an importance topic recently in spectroscopy
field.
Nowadays
laser-induced
breakdown
spectroscopy (LIBS) is increasingly popular among
the available methods for direct qualitative and
quantitative analysis on solid and gas samples, but rare
report was found in case of liquid samples. This
mainly due to the splashing off of the liquid sample
during laser irradiation.

Many researchers had done different methods to
overcome this disadvantage of LIBS. Charfi et al [1],
reported
an
experiment
by
focusing
a
Neodymium:Yttrium Aluminum Garnet (Nd:YAG)
laser (1064 nm, 7 ns) on the water surface directly via
a quartz plano-convex lens of 100 mm focal length.
To avoid splashing off of water on the optical
componens in the vicinity, the focused beam was tilted
at an angle of 600 to the water surface by adjusting the
inclination angle of the reflecting dichroic mirror. To
improve data reproducibility, a low laser pulse
repetition rate of 0.2 Hz was used to get rid of any
shockwaves that produced ripples on the water
surface. This experiment used pure solutions of Mg

International Conference on Theoretical and Applied Physics (lCTAP 2012)
AIP Conf. Proc. 1555, 14-16 (2013); doi: 10.1063/1.4820982
© 2013 AIP Publishing LLC 978-0-7354-1181-4/$30.00

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EXPERIMENTAL PROCEDURE

RESULTS AND DISCUSSION

Sample Preparation

Figure 2 shows a typical plasma emission
spectrum of 50 l Pb solution absorbed in absorbent 1
at 1 μs delay time and laser energy of 120 mJ. The
graph clearly represents the emission of Pb I 405.7
nm. However as shown in the same figure, there is no
emission of Pb in original absorbent 1. Based on this
data, the absorbent 1 can be used for Pb analysis in

liquid sample.

In order to avoid splashing off of the liquid sample
during laser irradiation, a sample pretreatment was
done, namely the liquid sample was absorbed by using
commercialy available stomach medicine. Two kinds
of absorbent materials were chosen in this experiment,
first containing 125 mg activated carbon (absorbent 1)
and second 600 mg activated attapulgite (absorbent 2).
To characterize the absorption process, three
treatments were conducted in this experiment: first,
without heating the absorbent but varying the
absorption time before laser irradiation. In this
treatment 50 l liquid sample containing 1,000 ppm of
Pb was dropped onto the surface of absorbent and
time lag of 1,15, 30, 45 and 60 minutes before laser
irradiation was chosen in order to find the best
absorption time; second, by varying the heating
temperature (45 – 65 – 85 0C) after certain time of
optimum absorption process in the first treatment;

third, by varying the heating temperature of the
absorbent (45 – 65 – 85 0C) prior of dropping the
sample solution.

FIGURE 2. Typical LIBS spectrum of 50 μl Pb
solution in absorbent 1.

In order to elucidate the best experimental
condition, the laser energy was varied in this
experiment. Figure 3 shows how the emission
intensity of Pb I 405.7 nm changes with increasing the
laser energy. For this experiment, 50 l Pb solution
was dropped on the absorbent 1 with 30 minutes
absorption time[6,7]. It is clearly seen that the
emission intensity is constantly increase with the
increasing of laser energy up to 140 mJ which is the
maximum laser energy in this system. One should be
noted that below 60 mJ, the Pb emission is very weak
meanwhile for above 120 mJ, vaporization amount is
too large yielding a dusty atmospheric condition in the

sample chamber. Thus a 120 mJ laser energy was used
in all of the next experiment.

Experimental Setup
The experimental set up used in this study is
illustrated in Figure 1. The commercial LIBS system
consists of Ocean Optics LIBS 2500+ spectrometer, a
sample chamber, Nd:YAG laser (model CRF 200,
1,064 nm, 7 ns) and OOILIBS software. For this
experiment, the Nd:YAG laser was operated at 5 Hz
repetition rate with energy of 120 mJ. The laser
irradiation was focused through 10 cm focal length
biconvex lens onto the sample surface and the resulted
emission radiation was analyzed by optical
multichannel analyzer containing 14,336 CCD pixels
in the wavelength region of 200 – 980 nm with
resolution of 0.1 nm. All the experiments were
conducted in surrounding gas of air at 760 Torr
pressure.
Mirror

Nd:YAG laser
LIBS 2500+ +
spectrometer

computer

A bundle
of
fiber

Lens

Plasm
Absorbent
sample

FIGURE 3. Emission intensity of Pb I 405.7 nm as a
function of laser energy.
FIGURE 1. Experimental setup.

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The next experiment was done to investigate the
influence of the delay time between the laser-sample
interaction and the detection time[8]. Same sample
was used as in the case of Fig. 3. Since rough Pb
emission characteristic was already known based on
Fig. 3 data, the signal (Pb I 405.7 nm) to background
ratio was used in this experiment and Fig. 4 shows
how the S/B changes with delay time. It is clearly seen
that maximum S/B was obtained at gate delay of 0.5
μs.

FIGURE 5. Emission intensity of Pb I 405.7 nm as a
function of sample pretreatment.

CONCLUSION
Preliminary qualitative analysis of Pb liquid

sample by means of LIBS technique has been
performed. A sample pretreatment was done, namely
the liquid sample was absorbed by using commercial
available stomach medicine. The maximum emission
intensity of Pb I 405.7 nm was found in the case of
heating the sample till 850C after 30 minutes
absorption of the liquid sample in carbon absorbent
materials. This fast and considered to be no sample
pretreatment will be easily developed for elemental
analysis of liquid sample using LIBS technique in the
near future.

FIGURE 4. Signal (Pb I 405.7 nm) to background
(S/B) ratio as a function of detection delay time.

Based on Fig. 3 and Fig. 4, laser energy of 120 mJ
and delay time of 0.5 s was chosen for further
experiment of sample pretreatment effect as shown in
Fig. 5. For the first treatment, 50 μl Pb solution was
dropped in both absorbent 1 and 2 and the absorption
waiting time was set at 1, 15, 30, 45 and 60 minutes
and the result is shown as point 1 till 5 respectively in
Fig. 5. Clearly seen that 30 minutes waiting time as
representated by point 3 in Fig. 5 is the best condition
for detecting Pb in both absorbents. For the second
treatment, point 3 sample was used and the heating
temperature was varied from 45, 65 and 85 0C and the
result is representated by point 6, 7 and 8 respectively
in Fig. 5. One should noted that heating temperature of
85 0C (point 8) yielding the best condition for Pb
emission in both absorbent. Further increasing the
temperature cause serious sample crack, thus 85 0C
was considered the best for second treatment. Finally
the third treatment was conducted. Absorbent 1 and 2
was heated till 45, 65 and 85 0C and then was dropped
by 50 l Pb solution and the resulted Pb emission can
be seen as point 9, 10, 11 respectively in Fig. 5 which
is much lower as compared to point 8 in the same
figure. Based on this result, the maximum emission
intensity of Pb I 405.7 nm was found in the case of
heating the sample till 850C after 30 minutes
absorption of the liquid sample in both absorbent
materials. This study also shown that there is no
significant difference between the use of absorbent 1
and 2.

REFERENCES
1. B. Charfi and M. A. Harith, Spectrochim. Acta B 57,
1141-1153 (2002).
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3. J. S. Huang, C. B. Ke and K. C. Lin, Spectrochim. Acta
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4. J. S. Huang and K. C. Lin, J. Anal. At. Spectrom 20, 5359 (2005).
5. J. S. Huang, H. T. Liu and K. C. Lin, Anal. Chim. Acta
581, 1303-308 (2007).
6. U. Agustiningrum, “Analisis Kualitatif Batu Paras
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(LIBS)”, Under Graduate Thesis, Udayana University,
2012.
7. G. Budiartawa, “Adsorbsi Batu Padas Terhadap Ion
Logam Pb+2 dan Cr+2 dalam Larutan”, Under Graduate
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8. D. A. Cremers and L. J. Radziemski, Handbook of
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