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

giorgio.senesi@imip.cnr.it

Credits

D.M.B.P. Milori

G. Nicolodelli

C.H. dos Santos

C. Montes

P.R. Villas-Boas