UM NOVO E VERSÁTIL CAMINHO PARA ANÁLISE E MONITORAMENTO DE
SOLOS, PLANTAS E ADUBOS
G.S. SenesiG. Nicolodelli, C.H. dos Santos, C. Montes, P.R. Villas-Boas, D.M.B.P. Milori
IMIP-CNR, Bari Italia
Laser-Induced Breakdown Spectroscopy(LIBS)
An adaptable spectroscopic multi-elemental analytical technique based on atomic emission spectroscopy
LIBS can be employed on samples in any physical state: solid, liquid, and gaseous including aerosols
LIBS can be used in situ for real time analysis, either atreduced or atmospheric pressure
Physical processes in LIBS
focused laser pulses on the sample
small sample ablation and plume evolution
vaporization, atomization and excitation of the elements
high Bremsstrahlung continuum early in plasma lifetime
generation and emission in progressive time of ions > neutral atoms > molecule fragments
collection of the emitted light and detection by spectrometer
the unique spectral emissions obtained representthe fingerprint of each element analyzed
Sample
Pulsed laser
Fiber optic
DetectorSpectrometer
Em
issio
n In
ten
sity
wavelength
Experimental set-up
a single laser focused with a spherical lens close to the target position
axial collection of the plasma radiation with a pierced mirror
a spherical lens to form an image of the plasma at the entrance of a fiberoptic coupled optically with a monochromator.
The goal of the LIBS technique
To create an optically thin plasma that is in the LTE state and whose elemental composition is the same as that of the sample, assuming that the ablation is stoichiometric.
When these conditions are fulfilled the observed spectralline intensities are related to the concentrations of the elements in the sample.
Little to no sample preparation
Rapid and relatively simple chemical analysis in real time
Simultaneous multi-element analysis
Sensitive to light elements, such as C, B, Be, H, Li
Detection and quantification of trace elements (ppm)
Simple set-up with samples that can be analyzed in harsh
environments (underwater analysis also possible)
Only nanograms of material per laser pulse, minimally
destructive
Stratigraphic analysis
Environmentally friendly (no chemical waste)
The system is cost effective and less time consuming
LIBS advantages over other analytical methods(such as ICP-OES, ICP-MS, AAS, XRF)
LIBS Limitations/drawbacks
The matrix effects
Variations of the laser spark and resultant plasma formation
The accuracy of LIBS measurements is typically higher than10% RSD (Relative Standard Deviation), and the precision isoften higher than 5% RSD
LODs generally range from <1 ng/g to >100 ng/g and LODs of tens of ng/g by mass are not uncommon.
What is LIBS used for?
Environmental analyses
Cultural heritage
Combustion
Forensics and military applications
Food
Pharmaceutical
Biomedical
Nuclear and industrial analyses
During the last decade has undoubtedly achieved tremendous popularityDue to its simple and direct nature
Several fields of applications
LIBS applied to agriculture
Elemental profiling and identification of eco-toxic elements in
soil
S0 Apulia, Italy Silt loam
S1 Apulia, Italy Loam
S2 Apulia, Italy Loam
S3 Lombardy, Italy Clay loam
S4 Marche, Italy Sandy clay loam
SS Sewage sludge
LIBS qualitative soil analysis
Al, Ca, Cr, Cu, Fe, Mg, Mn, Pb, Si, Ti, V and Zn
LIBS quantitative measurementsof Cr, Cu, Zn, Pb, V
Element Unknown sample ICP-OES (mg kg-1
) LIBS (mg kg-1
)
Cr S3 550 ± 82 533 ± 80
Cu S4 100 ± 15 88 ± 21
Zn S2 897 ± 135 846 ± 37
Pb S1 180 ± 27 168 ± 18
V S1 84 ± 12 80 ± 7
Carbon concentration in Brazilian forest spodosols and oxisols
measured by LIBS
Double Pulse LIBS applied to analyze Amazonian soils
Cr conc. = 18.8 mg kg-1Cr conc. = 4.6 mg kg-1
Cr I
Ti I
Cr I
Ti I
SP DP
Tex = 8497 K Tex = 7295
K
SP DP
Tex = 7158 K Tex = 6890 K
LIBS applied to plants and composts
Al, Ca, Cr, Cu, Fe, K, Mg, Mn, Na, Pb, Sr, and Zn
LIBS vs ICP-OES
Ca Mg
Fe Cr
Limit of Detection (LODs) for elements
In situ analysis by LIBS
LIBS is an attractive option, and a promising and versatile candidate for use as a field sensor.
- In situations where access to the sample is difficult(hostile environment)
- When the sample cannot be transported to the laboratory
From http://www.msl-chemcam.com
Obrigado pela sua paciência e atenção
Dr. Giorgio S. Senesi
IMIP- CNR, Bari , Italia
Credits
D.M.B.P. Milori
G. Nicolodelli
C.H. dos Santos
C. Montes
P.R. Villas-Boas