induced breakdown spectroscopy (LIBS)

Study of filtering Ag liquid sample by chitosan biomembrane using laserinduced breakdown spectroscopy (LIBS) Ni Nyoman Rupiasih, Hery Suyanto, Made Sumadiyasa, Christine Prita Purwanto, and Rendra Rustam Purnomo Citation: AIP Conf. Proc. 1555, 32 (2013); doi: 10.1063/1.4820987 View online: http://dx.doi.org/10.1063/1.4820987 View Table of Contents: http://proceedings.aip.org/dbt/dbt.jsp?KEY=APCPCS&Volume=1555&Issue=1 Published by the AIP Publishing LLC.

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Study of Filtering Ag Liquid Sample by Chitosan Biomembrane Using Laser-Induced Breakdown Spectroscopy (LIBS) Ni Nyoman Rupiasih1,*, Hery Suyanto2, Made Sumadiyasa2, Christine Prita Purwanto1 and Rendra Rustam Purnomo1 1

Biophysics Laboratory, 2 Applied Physics Laboratory, Department of Physics, Faculty of Mathematics and Natural Sciences, Udayana University, Denpasar, 80361, Indonesia *Email: [email protected] Abstract. The capability of Laser-Induced Breakdown Spectroscopy (LIBS) to resolve filtration process of Ag liquid sample by chitosan biomembrane is demonstrated. The biomembrane was prepared by inversion method used to filter Ag liquid using pressurized technique samples which were then analyzed by monitoring the emission corresponding to Ag (I) at wavelength of 328 nm. The experiment was conducted by varying the laser energy i.e. 80, 120, and 160 mJ, where, subsequently, and its effect on the depth-profile from 20 - 200 μm was characterized by LIBS. The results showed that the physical processes of pressurized filtration led a homogeneous Ag in the membrane from the surface to a depth of 200 μm. The optimum condition was obtained at laser energy of 120 mJ. The adsorption occurred only on the surface of the membrane i.e. 20 μm depth, but there was no inclusion. Improvement of the detection performance of adsorption process was done by heating the dripped membrane at 35 oC and was resulting in increase in emission intensity as expected. Keywords: Chitosan biomembrane; pressurized filtration; liquid Ag; Laser-Induced Breakdown Spectroscopy PACS: 82.35Pq

one requires a pulsed laser for generating microplasma on the target surface and elemental analysis is accomplished by studying the emission of the plasma plume. The performance of LIBS depends on several parameters including laser wavelength, pulse energy, pulse duration, time interval of observation, and geometrical configuration of collecting optics, target features, and properties of ambient medium. Extensive work has been devoted to optimize these parameters for the best experimental and commercial realization of this technique. The main disadvantage of LIBS is the high limit of detection, about 500 ppm but 1ppm can be reached for some elements [4]. LIBS is a very versatile technique and have been used in siderurgy, industrial process control [4-7], environmental geochemistry, biohazard material detection, forensic science, microbiology, odontology, archaeology, cultural heritage and art conservation [812]. Several papers dealing with LIBS applications in depth-resolved analysis have also reported [5, 9-13]. In their reports, the laser was focused to a different extent resulting in high irradiances (typically in the order of 109 - 1011 Wcm-2). In this study, the main purpose is to explore the capability of Laser-Induced Breakdown Spectroscopy

INTRODUCTION Chitosan is the most abundant natural polymer after cellulose. It is a partially deacetylated product of chitin, which has many useful features such as nontoxic, biocompatibility, biodegradability, and antibacterial property. Due to its features, chitosan has been widely applied in many industries including weastewater treatment. Chitosan has the ability to form complexes with metals. It exhibits higher adsorption capacity for metal ion compared to that of chitin owing to the amino group content. However, the serious drawback of chitosan for metal ion adsorbent from practical utilization is that it is soluble in acidic media [1-2]. Laser induced breakdown spectroscopy (LIBS) or laser induced plasma spectroscopy is a useful method to determine the chemical composition of a wide range of materials including metals, liquids, aerosols, plastics, minerals, biological tissues, etc. [3]. As an analytical technique, LIBS presents some advantages to other techniques: no sample preparation, real time analysis, contactless analysis, apparatus or experimental simplicity, inexpensiveness, robustness, and quickness are interesting properties which makes LIBS an attractive analytical technique. In many cases is a non destructive technique [1]. In this technique

International Conference on Theoretical and Applied Physics (lCTAP 2012) AIP Conf. Proc. 1555, 32-35 (2013); doi: 10.1063/1.4820987 © 2013 AIP Publishing LLC 978-0-7354-1181-4/$30.00

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(LIBS) too resolve filtrration processs of Ag liquiid sample byy chitosan bio omembrane ussing pressurizeed technique. Depth profilee analysis was conducted by b varying laser energy from m 80 to 160 mJ m each for 20 to t 200 μm depth. d Variouss methods off the adsorptioon process off Ag solution in the membrranes were alsso carried ouut i.e. control (w without treatm ment) is called as a Sample-1; natural adsorp ption as Sampple-2; adsorptioon by heatingg as Sample-3 3; adsorption after a heating as a Sample-4; and adsorption n with pressuree as Sample-5.

d. Laser-In nduced Breaakdown Specttroscopy (LIIBS) Lasser induced brreakdown specctroscopy was used to probbe the present of Ag elemennt in the pressuurized treatedd chitosan biom membrane at various v depths from the surrface. The LIB BS 2500-7 pluss model was ussed. It uses Nd-YAG N Laseer (1064 nm (wavelength), 7 ns (pulse width), 200 mJ m (max. energgy)) and echellle HR 2500 spectrometer s w specifications such as, range with of the spectrum 200--980 nm, with 7 channels, FW WHM resoluttion of 0,1 nm n using 7 deetectors with 2048 elemennt linier siliconn CCD arrayss that given tootal of 14336 pixels. The ouutput of the speectrometer anaalyzed OLIBS and OOIICOR softwarees that displeyyed on by OO the moonitor. In the t present stuudy, the delay time t used was 1 μs, 4 pulses of each scaan, and 0 pulsee cleaning (to avoid unneceessary scan). The T laser energgy density (fluuence) employyed in the expperiments was in the range 600-180 mJ. Thhe pulse to pullse energy variation throughoout all measurements perforrmed, was no > ± 5%. The saample was pllaced approxim mately 2 cm inn front of the focal point and a a relativelly wide spot (aapprox. 1 mm) was used in the LIBS measurement m inn order to obttain a represeentative averaage of the maaterial compossition. Emissiion spectra were recorded separately for each one off successive laaser pulses andd were subsequuently analyzzed.

MAT TERIALS AND A METH HODS a. Ma aterials The materials m used are a Chitosan powder p with characterisstics i.e. 87,9% deacetylateed and their solubility in acetic acid is 99,4%; aceetic acid and sodium hyydroxide p.a. All A reagents weere analytical grade and were used with hout further puurification.

b. Prep paration of Chitosan C M Membrane The chhitosan solution n of 4% (w/v) was w prepared by dissolvving 10 g of chiitosan powder in 250 ml of 1% acetic acid solution n. The mixturee was stirred for 8 houurs at room teemperature to obtain dope solution. The T dope solutiion was pouredd into a glass plate and dried d at room temperature t forr 6 days. The membranee was in the NH H3+ form. It was w dipped in 1% sodiuum hydroxidee solution too reach the unchargedd amino form, washed w with diistilled water 3 times to eliminate the excess of sodium hydroxide, then dried d.The thickneess of the membranee was around 236 μm.

RESULTS S AND DISC CUSSION Figgure 1 shows LIBS L spectra off control (Sampple-1) and pressurized p t treated chitoosan biomem mbrane (Sampple-5) scanned with w laser enerrgy of 120 mJ in the range 327 - 329 nm. It shows a peak at wavelenggth of 328 nm n in Samplee-5 which is known as attomic emission line of Ag (I), whereas no n peak observves in the control membranne (Sample-1). This explains that there is Ag in the Sam mple-5 that adm mitted by presssure.

c. Membrane Treatm ments In this study, the chiitosan biomem mbranes have been treatted in 5 diffeerent ways i.ee. Sample-1: control (w without treatm ment), Sample-2: Ag 1000 ppm droppped on the meembrane and allow a to dry naturally (natural ( adsorp ption), Samplee-3: Ag 1000 ppm droppped on the mem mbrane and heeated to 35°C (adsorptionn by heatin ng), Sample-44: heat the membranee to 35°C then dropped wiith Ag 1000 ppm (adssorption after heating), andd Sample-5: membranee exposed to Ag A 1000 ppm m solution by filtration method with h pressure ~ 50 kPa (adsorptionn with pressuree).

FIGUR RE 1. LIBS sppectra of controol (Sample-1) and a pressurrized treated chhitosan biomem mbrane (Sample--5) scannedd with laser eneergy of 120 mJ in the range 3277 329 nm m.


200 180 160

Intensity (a.u.)

140 120 100 80

Samp ple-5, 80mJ

60

Samp ple-5, 120mJ

40 20

Samp ple-5, 160mJ

0 0

20 40 60 8 80 100 120 140 160 180 200 220 Depth (μm)

FIGURE 2. 2 LIBS spectraa of the pressurrized chitosan biomembraane (Sample-5) in i the range 3277 - 329 nm for laser energiies 80, 120, and d 160 mJ. Contrrol (Sample-1) spectrum iss presented (kep pt at laser energgy of 120 mJ) for the com mparison.

FIGUR RE 3. Intensityy of atomic em mission of Ag (I) at wavelength of 328 nm obtained by LIB BS with laser ennergies d from the surface 80, 1200, and 160 mJ ass a variation of depth for the pressurized chittosan biomembraane (Sample-5).

To study about thhe adsorption process p of Ag in the chitosaan biomembrrane, four methods m mem mbrane treatment are introduuced. The resullts are shown inn Fig. 4. For natural (Sampple-2) after firstt shot (shot-1, depth ~ 20 μm) μ by laser energy e of 120 mJ, the intensity of Ag (I) obtained was ~ 6.67 a.u, whhile at a depth of 40 μm (ssecond shot) was null, indicating i thaat no inclusiion process occcurred. To im mprove the deteection perform mance of the t adsorptioon processes, an adsorpption by heatiing method was w introducedd, the treatedd membrane with w the same process p of Sam mple-2 is heaated to 35°C (Sample-3) annd the intensiity is increassed to ~ 8.75 a.u. a This indicaates that the prrocess was innfluenced by the t temperaturre. Result from m the secondd shot was alsoo zero. Furtherrmore an adsorrption after heating h methodd was used. Heating the mem mbrane before dripping it with 1000 ppm Ag sollution (Sampple-4), gave inttensity as low w as, ~ 5.5 a.uu. The intensiity of Samplle-5 (adsorptiion with preessure methodd) was the highhest at ~ 21.5 a.u. a Theese results desscribe Ag liquiid penetrate intto the membrrane properly when w pressurizzed (adsorptionn with pressuure method). This causes Ag interact both chemiccally and phyysically with the t membranee and producces strong covaalent bonds in the t membrane. As a result, providing a strong s reboundd momentum during d the lasser shot and prroduced plasmaa emission inteensity Ag (I) at wavelengthh of 328 nm is high h comparedd with other adsorption a methods.

Figure 2 shows LIB BS spectra of the pressurizeed chitosan biomembrane b (Sample-5) ( in the range 327 329 nm foor varies of laseer energies 80 mJ, m 120 mJ, annd 160 mJ. Control C (Samplle-1) spectrum m at laser energgy of 120 mJJ was also keptt for the comparison. It show ws that the intensity of Ag A (I) peak increases witth increasingg laser energy. This describees more numbeer of electronns from the ato oms and more ions have beeen excited heence more em mission of specctrum obtained. The spectrrum also showss increasing in the backgrounnd signal as laser l energy in ncreases, whicch is due to thhe continuum m emission of the plasma foorm [14]. From m these resuults, further ex xperiments weere focused annd analyzed on laser energ gy of 120 mJJ and stated as a optimal coondition for thee chitosan biom membrane. Figure 3 shows the in ntensity of atom mic emission of o Ag (I) at wavelength of o 328 nm obttained by LIB BS (with laserr energies 80, 120, 1 and 160 mJ) m as a functioon of depth from fr the surfacce, of the presssurized chitosaan biomembrrane (Sample-5 5). The graph shows that thhe emission was w observed for all depthss indicating thhat Ag has beeen evenly disttributed withinn the sample. At A the higherr laser energy y, 160 mJ shoows fluctuationn. This meaans that the intensity i of the t backgrounnd increase, the t peak becom mes broad andd self adsorptioon process takke place. For fuurther examinaation of Fig. 3, the standarrd deviation of the LIBS intensity wass calculated by b measuringg the intensity from three ideentical series of o adjacent areas a on the sample surfacce. The overaall standard deviation d in th he intensities of o Ag (I) was ~ 2% for lasser energy 80 and a 120 mJ, annd ~ 5% for 1660 mJ.


ACKNOW WLEDGME ENTS

Intensity (a.u.)

25

w to thankk the Facultty of The authors wish Mathematics and Natural Sciences, Udaayana Univerrsity for the LIIBS facility.

20 15

REF FERENCES S

10 5

1.

0 SampleS SampleSample2 2;shot-1 Sample3;shot-1 Sample4;shot-1 Sample5;sshot-1 ampleSa 2;shot-2 3;shot-2 Sample4;sshot-2 5;shot-2

2.

FIGURE 4. 4 Intensity of em mission of Ag (I)) at wavelength of 328 nm for various membraane treatments. 3.

The addsorption proceesses occurredd in the chitosaan biomembrrane can be deescribed as follows. The Agg+ ions whichh were chemicaally adsorbed through t bondinng with N in [Ag (NH3)2]+ as a covalent bond b resulted in i only a paiir of electronss shared by attoms N. Such a bond is called a coordinaation covalent bond. b Here, Agg+ ion is an electron acceeptor, while N is an electroon donor. Thherefore, the fo ormed adsorption layer is noot sufficientlyy strong when the laser shot and hence gavve relatively low emission (Sample-2). To T enhance thhe results off this adsorpttion, the reinnforcement waas carried ouut by heatin ng (Sample-3)) and producce relatively higher emissions than without w heatinng (Sample-22). The adsorrption after heating h methood produced low emission ns. In this casse, heating haad caused a damage to th he physical structure s of thhe membranee and eliminatiing or reducingg the number of o N that acteed as Ag adsorrption media, thus t resulting in i a low intennsity.

4.

5. 6.

7. 8. 9. 10. 11.

CONCLUSION 12.

The present p study demonstrated laser induceed breakdownn spectroscopy y (LIBS) to prrobe the presennt of Ag eleement in the pressurized treated t chitosaan biomembrrane at variouss depths from m the surface. It was analyyzed by monittoring the em mission of Ag I (wavelenggth of 328 nm m). The pressuurized filtratioon process reesulted in a hom mogenously distributed Ag in i the membrrane up to a deepth of 200 μm m. The optimum m laser enerrgy was 120 mJ. m The chem mical adsorptioon process occcurred only att the surface of the membranne without innclusion. Impro ovements can be b done by heat treatment at a 35qC.

13. 14.

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