determination of trace elements in paints by direct sampling graphite

analyt ica ch im ica acta 6 0 2 ( 2 0 0 7 ) 2331

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Article history:

Received 6 M

Received in

20 August 2

Accepted 3

Published o

Keywords:

Direct samp

Graphite fur

spectrometr

Trace eleme

Paints

a b s t r a c t

A direct sampling graphite furnace atomic absorption spectrometric (DS-GFAAS) method

1. Int

Paints reprtional painpaint is elead chrompersed in aepoxy, polyhols, acetatand additivcarbonate,ticizers (tri

CorresponE-mail a

0003-2670/$doi:10.1016/ay 2007

revised form

007

September 2007

n line 6 September 2007

ling

nace atomic absorption

y

nts determination

for the determination of Cd, Pb, Cr, Ni, Co and Cu in paints has been developed. Serigraphy,

acrylic and tattoo paints were analysed. Approaches like pyrolysis and atomization temper-

atures, modiers and sample mass introduced in the atomizer were studied. Quantication

was performed using calibration curves measured with aqueous standard solutions pipet-

ted onto the platform. The sample mass introduced in the graphite tube ranged from 0.02

to 8.0mg. Palladium was used as modier for Cd, Pb and Cu, while Mg(NO3)2 was used for

Co. For Ni determination, the graphite platform was covered with carbon powder. The char-

acteristic masses of Cd, Pb, Cr, Ni, Co and Cu were 1.4, 22.5, 7.9, 11.0, 9.6 and 12.5pg, while

the limits of detection were 0.0004, 0.001, 0.03, 0.22, 0.11 and 0.05gg1 of Cd, Pb, Cr, Ni,

Co and Cu, respectively. The accuracy was determined by comparison of the results with

those obtained by inductively coupled plasmamass spectrometry (ICP-MS) and graphite fur-

nace atomic absorption spectrometry (GFAAS), using liquid sampling of digests. For matrix

characterization, major and minor elements (Al, Mg, Ba, Ca, Cr, Cu, Pb, Sr, Ti and Mg) were

determined by inductively coupled plasma optical emission spectrometry (ICP OES).

2007 Published by Elsevier B.V.

roduction

esent a wide range of products from conven-ts to varnishes, enamels and lacquers. Typicalssentially inorganic pigment (titanium dioxide,ate, chromium oxide, metallic powders, etc.) dis-matrix consisting of a binder (polyurethane, vinyl,styrene, etc.) and a solvent (water, ketones, alco-es, esters, hydrocarbons, etc.) with selected llerses used as extenders (barium carbonate, calciumtalc, mica, kaolin, etc.), driers (lead octate), plas-cresyl orthophosphate), fungicides (mercury aryl

ding author. Tel.: +55 51 3316 73 04; fax: +55 51 3316 72 15.ddress: [email protected] (D. Pozebon).

compounds and organic tin compounds) and dyes (-naftol,ftalocianine, anthraquinone, avantrones, etc.). The main dif-ferences among inorganic pigments and dyes, which areusually present in paints, are particle size and solubility in themedium. Inorganic pigments are more insoluble and stable inthe paint and promote higher resistance to light and superiorcoating capability [1].

Metals are present in the inorganic pigments of paintsand play an important role in the ability of the paint to per-form its function. Metal content of pigment compounds notonly produces colour but also contributes to other chemi-cal and physical properties of paints such as rust inhibitive

see front matter 2007 Published by Elsevier B.V.j.aca.2007.09.003mination of trace elements insampling graphite furnace atption spectrometry

R.S. Bentlina, Dirce Pozebona,, Paola A. Mee Qumica, Universidade Federal do Rio Grande do Sul, UFRGS, 9150nto de Qumica, Universidade Federal de Santa Maria, UFSM, 9710ints byic

b, Erico M.M. Floresb

0 Porto Alegre, RS, Brazil0 Santa Maria, RS, Brazil

24 analyt ica ch im ica acta 6 0 2 ( 2 0 0 7 ) 2331

characteristics and durability. However, inorganic pigmentsmay contain such toxic elements as lead, chromium, cadmiumand cobalt [1,2].

Paints may present many difculties to the analyti-cal chemists towards developing reliable methods for traceelements determination. Major drawbacks are matrix inter-ference, sample insolubility, analyte loss and contaminationduring decomposition in open vessels. Microwave assisteddigestion in pressurized vessels, or digestion in open ves-sels assisted by heating in hot plate, or partial acid digestionin addition to charring in mufe have been employed, beingHNO3 and HF frequently used [38]. However, some authorsreported that volatile elements like Pbwere lost in open vesselduring the digestion step. In these methodologies the liq-uid paint is mechanically homogenized and then analysed,or a dry lm of the paint is obtained over a surface and thenscraped and analysed [8]. However, by using the last procedurethe risk of contamination is high.

Elementby ame atfurnace atinductively(ICP OES) [2compoundexpected tplasma mamay haveother handapplied [9]painted su(LODs) andminor andquantied.result in inLA-ICP-MSuorescencalso a direcdeterminatciently low

Amongcould be ufurnace atovery attracnation, sm

little sample preparation. DS-GFAAS has proven its usefulnessfor fast mono-element determination in complex materials.The technique is nowadays being employed to analyse mate-rials such as silicon carbide, niobium oxide, pure titanium,etc. [1316]. However, no reports dealing with the use of thetechnique for paints analysis were found. Hence, the mainpurpose of the present work is to investigate the applica-tion of direct sampling graphite furnace atomic absorptionspectrometer (DS-GFAAS) for trace elements determination inpaints. Approaches like pyrolysis and atomization tempera-tures, modiers, sample amount introduced in the atomizerand calibrations with aqueous standards are investigated. Formatrix characterization with respect to metals content, theinvestigated samples are analysed by ICP OES. The proposedmethod is validated by comparison with ICP-MS and GF AAS.For the determinations using these techniques, the paint sam-ples are acid digested in quartz vessel in microwave oven.

Ex

Ins

d, Cng ana, Jte at. Thhich

, Cu,and C0.7n0.8nIntete fu.anu

tic calanometas ughed000

or th

Table 1 min

Step Cs1

DryingPyrolysisAtomizatio 500Clean out 550

Maximum:a Cd.b Ni.c Cr.d Cu.e Co.f Pb.s determination in paints was carried out mainlyomic absorption spectrometry (FAAS) [3,4], graphiteomic absorption spectrometry (GFAAS) [5] andcoupled plasma optical emission spectrometry,6,7]. Given the high content of salts and organic

s usually present in paints,matrix interferences areo occur in quantications by inductively coupledss spectrometry (ICP-MS) and such inconveniencelimited the application of the technique. On the, laser ablation (LA) coupled to ICP-MS has being. In this case, a drying lm of the paint or therface can be analyzed. Low limits of detectionelemental information are obtained and major,trace elements present can be identied and/orHowever, the complex matrix composition mayterferences. Therefore, for quantications usingmatrix-matched standards may be required. X-raye (XRF) [10] has been employed as well, which ist sampling technique and provides multi-elemention. However, the LODs of XRF are usually not suf-for trace elements determination.

the different direct sampling techniques [911] thatsed for paint analysis, direct sampling graphitemic absorption spectrometry (DS-GFAAS) [12] istive, due to good sensitivity, low risk of contami-all sample amount, low reagent consumption and

2.

2.1.

Lead, Cby usilytik Jegraphisystem0.8T, wPb, CdCr, Ni,and 24set atfor Co.graphiTable 1

A mpyrolymicrobspectrtion, wbe weiwave 3used f

Graphite furnace program for Pb, Cd, Cu, Cr, Ni and Co deter

Temperature (C) Ramp (

110 10700a,f, 1100b, 1200c,d, 1400e 30

n 1900f, 2100a, 2500b,c,d,e 190022500a,f, 2550b,c,d,e 25002

2 Lmin1.perimental

trumentation and operating conditions

u, Cr, Ni and Co in paints were directly determinedZEEnit 60 atomic absorption spectrometer (Ana-

ena, Germany) equippedwith a transversely heatedomizer and a Zeeman effect background correctionemagnetic eld strength can be varied from 0.05 tomodies the sensitivity. Hollow cathode lamps of

Cr, Ni and Co were used. The monitored Pb, Cd, Cu,owavelengthswere 283.3, 228.8, 324.8, 357.9, 232.0m, respectively, while the spectral bandwidth wasm for Cd, Cr, Cu and Ni, 0.5nm for Pb and 0.2nmgrated absorbancemodewas used throughout. Thernace program that was optimized is shown in

al solid sampling system (Model SSA 6Z) andoated graphite tubes with platform were used. Ace (Sartorius M500P), which is integrated to theer software for automatic sample weight acquisi-sed. Up to 2.000 g, with 0.001mg of resolution, canby this microbalance. A microwave oven (Multi-

model from Anton Paar) and quartz vessels weree paints decomposition.

ation in paints

) Holding (s) Gas ow rate

30 Maximum60 Maximum6a,b,d,e,f, 8c Stop4 Maximum

analyt ica ch im ica acta 6 0 2 ( 2 0 0 7 ) 2331 25

For major and minor elements determination an OPTIMA4300 DV ICP OES spectrometer from Perkin-Elmer wasemployed.lizer gas o0.60.8 Lmiences, whewas monitthrough a Gpled to anmeasured i2 points weplasma viethe elemen

An ICP-MDRC II) equspray chamwas used foof the ICP-lizer gas maximumM2+, MO+ arate and th1400W, resinterface assamples we

2.2. Rea

Deionised win order tothe samplegrade HNOwas doublysystem befICP-MS, muwere prepastock solutCd, Co, Cr,1000mgL1

concentratand 100 tomination. Fsolutions eor 200gL

used. Thestions. Modand 1000mfrom stockMg(NO3)2].(type RWA,carbon (weused to covDS-GFAAS.

A set ofchased in tblack, blueple) and taacrylic painraphy painhighly visc

Table 2 Microwave oven program for paintsdecompo

(Csng (m(Cs

ng (mg (m

enise sa

].

Sam

ce eles wet bewasbmitainee vooluti-MS.S tweduhichot pTheNO3e watandto a petedwerin tas ba

Dere dadd

sed twereas dr

theadeda. Th.02 tmpleout fmotiplatform to and from the balance, a tray was used. Intermination of Ni, before loading of the sample, aboutof carbon powder were placed onto the platform and

mplete temperature program was executed to elimi-ontamination from both the platform and the carbonr. After loading and weighing the sample, the platformtroduced into the graphite tube and the measurementas started. At the end, the paint residueswere removedParameters like the plasma power and nebu-w rate were optimised, being set at 1300W andn1, respectively. For checking spectral interfer-n possible, more than one wavelength per elementored. Solutions were introduced in the plasmaemCone nebulizer and a Scott spray chamber cou-alumina injector tube (2.0mm i.d.). Signals weren peak area mode using 3 points per peak, whilere used for background correction. Radial or axialwing was used, depending on the concentration oft in the sample.S spectrometer from Perkin-Elemer/SCIEX (ELAN

ipped with a Meinhard nebulizer, bafed cyclonicber, quartz tube injector (2.0mm i.d.) and Pt conesr trace elements determination. The optimizationMS parameters was done by adjusting the nebu-ow rate and the RF power in order to obtain theproduction of ions M+ and minimum signals fornd background at m/z 220. The nebulizer gas owe plasma power were optimised to 1.1 Lmin1 andpectively. In order to minimise salt deposits on thewell signal suppression, the solutions of the paintre properly diluted.

gents and samples

ater, puried in a Milli-Q system (Millipore Corp.)achieve 18.2M cm of resistivity, was used for

s and standard solutions preparation. Analytical

3, H2O2 and HF from Merck were used. The HNO3distilled in a sub-boiling Milestone duo PUR 2.01Eore using. For the determinations by ICP OES andltielement analytical solutions in 5% (v/v) HNO3red from serial dilution of stock solutions. Theions were ICP VI from Merck (used for Al, Ba,Mn, Ni, Pb, Sr, Cu and Ca determination) andTi (Titrisol from Merck). The analytical solutions

ion ranged from 1 to 50gL1 for trace elements500gL1 for minor and major elements deter-or the DS-GF AAS determinations, monoelementach containing 500gL1 of Pb, Cr, Ni and Cu,1 of Co, or 50gL1 of Cd in 5% v/v HNO3 were

e solutions were prepared from Titrisol stock solu-iers solutions, 100mgL1 Pd in 5% (v/v) HNO3gL1 Mg(NO3)2 in 5% (v/v) HNO3, were obtainedsolutions of Merck [10 g L1 of Pd and 10gLl1 ofCarbon powder of highest purity for spectral useno 431815/00, series x/62/403) was supplied by SGLrk Ringsdorff, Bonn, Germany). This carbon waser the graphite platform for Ni determination by

10 paints of different sorts and colours were pur-he local market and analyzed: serigraphy (white,, red, green and yellow), acrylic for wood (pur-ttoo (black, red, green and yellow). The tattoo andts were water soluble and uid, while the serig-ts were soluble in non-polar organic solvents andous. The paints were mechanically shaken and

Step

RampHoldiRampHoldiCoolin

homogtion, thlm [8

2.3.

For trasamplof painHNO3ture suThe atand thThis sby ICPICP OEIn procsel to won a hnace.(v/v) Hvolumlet to sferredcomplmentsdiluteddure w ASTMples wused inincreaHNO3ture w(1).

Forwas lospatulfrom 0and satakenlinearof thethe de12mgthe conate cpowdewas incyclewsition

Power (W)

1) 5 0700in) 1 7001) 2 7001400in) 20 1400in) 20 0

ed just before the analysis. To avoid contamina-mples were analysed in liquid form instead of dry

ple preparation and procedure

ements determination by GFAAS and ICP-MS, there acid digested in microwave oven, 0.1000.200 ging weighed in a quartz vessel to which 8mL ofadded. Then, the ask was closed and the mix-tted to the heating program, as shown in Table 2.d solution was transferred to a volumetric asklume was completed to 50mL by water addition.on was 1050-fold diluted in the determinationsFor major and minor elements determination byo different decomposition procedures were used.re (1), 0.200 g of paint was weighed in a glass ves-5mL of HNO3 was added. The mixture was dried

late and then burned at 500 C for 2h in a fur-attained ash was solubilized with 10mL of 50%and the solution heated in a hot plate until thes reduced to near 5mL. Next, this solution wasin order to achieve the room temperature, trans-olypropylene volumetric ask and the volumewasto 50mL by water addition. Major and minor ele-e directly determined in this solution, or properlyhe case of high analyte concentration. This proce-sed on the American Society for Testing Materials3335-85a method [8]. In procedure (2), the sam-ecomposed in Pt crucibles, but in this case HF wasition to HNO3 and the temperature of the furnaceo 600 C. In this procedure, 2mL of HF and 5mL ofadded to the sample in Pt crucible and the mix-ied, ashed, solubilized and diluted as in procedure

determinations by DS-GF AAS the paint sampleonto the graphite platform by means of a small

e sample mass applied for an analysis cycle variedo 8.0mg, depending on the analyte concentrationtype. The graphite platform was inserted into and

rom the graphite tube by means of high precisionon system with a pair of tweezers. For transport

26a

na

ly

tic

ac

him

ica

ac

ta

60

2(2

00

7)

2331

Table 3 Concentrations (in %) of major and minor elements in paints, determined by ICP OES

Sample Method Al Mga Ba Ca Cr Cu Pb Sra Ti Zna

SerigraphyWhite N 0.31 0.01 217 2 2.70.4 206 12a 4465.3 4.40.1 1.30.02

F 0.26 0.02 190 11 2.20.4 213 9a 39334 9.20.4 2.10.8Black N 180 40 26 6


Fig. 1 Pyrolysis temperature curves of Pb, Cu, Ni, Cr, Co and Cd in aqueous solution; Pb and Ni in blue serigraphy paint, Cuin purple acrylic paint, Cr in black serigraphy paint, Co in serigraphy paint and Cd in black tattoo paint. The absorbance ofthe analyte in the sample was normalized to 1mg of mass.

from the pa clean outhe blank sincluding trcation of sacurves werof the calibgraphite pl5L (Pd forcalibrationered onto thplatform. InTable 1 was

Re

Ma

l metermchainordecole 3,ina

Fig. 2 TraCr, withoutplatform watomizatiois referredlatform by means of a small spatula, followed byt step in the graphite furnace. For determiningignal, a complete analytical cycle was performed,ansport to and fromthebalance, butwithout appli-mple, excepting the modier addition. Calibratione obtained by manually pippeting a given volumeration andmodier solutions and delivering on theatform. The volume of the modier solution wasPb, Cd and Cu or Mg(NO3)2 for Co), while that ofsolution was 215L. Both solutions were deliv-eweighed sample or the analytical solution on theall determinations the furnace program shown in

3.

3.1.

Severathe dematrixand mferentto TabContamemployed. vessel, and

nsient signals of Cr and Ni in blue serigraphy paint. Blue line: bamodier; (b) Cr, in presence of 500ng of Mg(NO3)2; (c) Ni, in platithout carbon powder covering. The pyrolysis temperature was 1n temperature was 2500 C for both. (For interpretation of the refto the web version of the article.)sults and discussion

jor and minor elements determination

tals are usually high in paints and may interfere inination of a trace element. In the present work, forracterization with respect to metals content, majorelements were determined by ICP OES. Two dif-mposition procedures were applied and accordingthe concentrations found are in good agreement.tion or analyte losses are prone to occur in open

these could be the reasons for some differences

ckground signal and red line: atomic signal. (a)form covered with carbon powder and (d) Ni, in100 C for Ni and 1200 C for Cr, while the

erences to color in this gure legend, the reader


found, for example Pb in the blue and Mg in the red serig-raphy paint samples. The remarkable exception is Ti, whoseconcentratby means otion of HF iobserved weral solutioonly HNO3the solutiomicrowaveple decompmajor andpaints (notand Ca. Ththe black ondetected intion founda toxic elemAdditionallbe seen thaplex, beingtask.

3.2. DS

3.2.1. FurConsiderinacteristicschosen forwere initiaDifferent panalyte conplexity. Preappropriatesensitivitythat thesethe absencCu. On theof Mg(NO3)nation by Geffect in abbut not in pother handMg(NO3)2 aRegardingatomic tranorder to ovcovered witdened Nieffects ovethe matrixpowder onthe samplethe pyrolyssolution antion that thto the diffeaqueous sotures chose1100 C for

Traand0ng)00 Cg o

terpr, the.)

arding to the atomization temperature, the highest sig-Pb was observed at 1700 C for both aqueous solutionmple. The proles of the atomization curves were anal-but it was observed the transient signal of Pb in the

e did not return to baseline at temperatures lower than. This observation suggested application of 1900 C asation temperature for Pb. At this temperature, Pb sig-e those shown in Fig. 3 were obtained that were almost

r for the different samples. The atomization tempera-tablished for Cd was 2100 C, while 2500 C was for Co,and Ni. These temperatures were chosen in virtue oftter peak shape observed for both analytical solutionint. The sensitivity was similar as well. Owing to therities observed for analytical solution and sample at thezed conditions with respect to peak shape and sensitiv-as concluded that calibration with aqueous standardbe possible.

Sample mass inuencemple mass introduced in the atomizer is a parame-t inuences accuracy and precision and, depending onount used, underestimated or overestimated concen-smay be determined by DS-GF AAS [17]. It is possible tonon-representative aliquot if the samplemass is too low,t is toohigh,matrixmay interfere and/or the absorbancet bewithin the linear range of the calibration curve. Thee range of samplemass varies according to the differentnts and matrices. An increase in the amount of sampleion is usually higher in the samples decomposedf HF and HNO3. These results show that the addi-mproves the sample decomposition. In fact, it washite precipitate, probably titanium oxide, in sev-ns of serigraphy paint samples decomposed using. Besides, white precipitate was also observed inns obtained from the white paints decomposed inoven, while HNO3 and H2O2 were used for sam-osition. Differently of the other analysed samples,minor elements were not detected in most tattooshown in Table 3). The few exceptions were Cu, Zne concentrations of Cu in the green paint and Zn inewere 0.45% and 0.41%, respectively. Calciumwasall tattoo paints, while the maximum concentra-

was 0.02%. It can also be observed in Table 3 that Pb,ent, is still used in high concentration in paints.

y, with the exception of the tattoo paints, it cant the matrices of the analysed samples are com-the determination of trace elements a challenging

-GF AAS method development

nace program and modiersg the concentrations of the elements and the char-of the samples, Cd, Cr, Cu, Pb, Co and Ni werethe study using DS-GFAAS. Pyrolysis temperatureslly investigated, whose curves are shown in Fig. 1.aints were used for this study due to high or lowcentration expected and/or sample matrix com-liminary investigations revealed that Pd was anmodier for Pb, Cd and Cu, which improved the

and precision. Subsequently, it was also observedelements could not be accurately determined ine of modier and then Pd was used for Pb, Cd andcontrary, Cr could not be determined in presence

2, which is usually recommended for Cr determi-F AAS. As shown in Fig. 2(a), there is not memorysenceof themodier andgoodCr signal is obtained,resence of Mg(NO3)2, as shown in Fig. 2(b). On the, Co determination was improved in presence ofnd, therefore, this modier was adopted for Co.to Ni, memory effects were observed, being thesient signals like that one shown in Fig. 2(d). Inercome this problem, the graphite platform wash carbon powder [15]. According to Fig. 2(c), a well-signal prole was then obtained and the memoryrcome as well. It was observed that the removal ofresidues was more easily performed with carbonthe platform, which minimized the interference ofresidues. In Fig. 1 it can be seen that the proles ofis temperature curves of the analyte in analyticald in paint are quite similar. It is important to men-e different absorbances observed in Fig. 1 are duerent analyte concentration in the paint and in thelution. According to Fig. 1, the pyrolysis tempera-n were 700 C for Pb and Cd, 1200 C for Cr and Cu,Ni and 1400 C for Co.

Fig. 3paintsPd (50and 190.504m(For inlegendarticle

Regnal ofand saogous,sampl1900 Catomisnals liksimilature esCr, Cuthe beand pasimilaoptimiity, it wwould

3.2.2.The sater thathe amtrationtakeabut if iwill nofeasiblelemensient signals of Pb (red line) in serigraphyrespective background (blue line) in presence of; pyrolysis and atomization temperatures: 700, respectively. Sample masses: 0.224 and

f blue and black serigraphy paints, respectively.etation of the references to color in this gurereader is referred to the web version of the


introduced in the graphite tube may inhibit the diffusion ofthe atomic vapour. Additionally, the abundant gas producedduring the vaporization or the thermal decomposition of thematrix may depress the analyte signal by decreasing the aver-age residence time of the analyte atoms in the furnace [17].Variations of Cd, Cu and Pb concentrations measured by DS-GF AAS were already observed for catalysts. It was found thatthe predicted resultsweremarkedly biased if the samplemasswas smaller than 0.4mg or higher than 1.6mg [20].

The inuence of the amount of sample was also inves-tigated in the present work. According to Fig. 4, theconcentration of Pb measured in the blue serigraphy paintvariesmarkedly when the samplemass is higher than 15ng ofPb (about 0.5mg of sample). In this case the Pb absorbance isno more within the linear range of the calibration curve (from1.0 to 12ng of pb). In the case of the black serigraphy paint,only small variations are observed because the concentrationof Pb is lower and the sample matrix is simpler. According toTable 3, there are about 2% of Ti, 0.5% of Cu and 0.1% of Al inthe blue paint, while in the black paint major elements are allin the gg1 range, or lower. The acrylic paint is also a verycomplex matrix (according to Table 3 it contains about 10% ofCa, 2% of Ti and 0.1% of Al). In Fig. 4 we can see that the Cu

and Cr concentrations measured decrease with the increas-ing acrylic paint mass, which demonstrates matrix inuence.On the other hand, the possibility of using higher amount ofmass was expected for the tattoo paints, since their matricesseemed simpler. Nevertheless, dark residues from the blackpaint remained in the graphite platform after the clean outstep of the furnace program. Therefore, matrix effects couldbe the reason for the decreasing of concentration observed,mainly those of Cu and Cd. From Fig. 4 it can be concludedthat, in general, 0.5mg of paint can be used in the analysis.However, this amount may not be appropriate for all paints.Therefore, when an unknown sample of paint is analyzed byDS-GF AAS, the analyst should test different aliquots of thesample in order to verify if the results are biased.Nevertheless,a unique calibration curve obtained with aqueous standardsof the element can be used for the different paints.

3.2.3. Analytical characteristics of the methodThe analytical characteristics of the DS-GFAAS method aresummarized in Table 4. The linear correlation coefcientsof the calibration curves, which were obtained by means ofaqueous standards, are not shown but they were at least0.997. As previously mentioned, higher and lower sensitivity

Fig. 4 In the dshown in T nd 5was covereuence of the sample mass introduced into the atomizer onable 1 was used. Modiers: 500ng of Pd for Cd, Cu and Pb ad with carbon powder for Ni determination.etermined concentration. The furnace program000ng of Mg(NO3)2 for Co. The graphite platform


Table 4 Analytical characteristics of the DS-GF AAS method for trace elements determination in paints

Analyte LOD (gg1) m0 (pg) Sample mass (mg) Linear range of calibration curves (ng)

High sensitivity Low sensitivity

Cd 0.0004 1.36 0.022.0 0.0020.02 0.020.2Co 0.11 9.65 0.51.25 0.42.8 Cr 0.03 7.85 0.31.0 0.21.0 1.02.5Cu 0.05 12.5 0.41.0 0.42.0 2.03.2Ni 0.24 11.0 3.08.0 0.051.0 1.04.0Pb 0.001 22.5 0.30.7 0.54.0 4.012.0

LOD: limit of detection and m0: characteristic mass.

are obtained by varying the magnetic eld. This is automati-cally done by the software of the instrument, depending onthe atomic signal intensity. According to Table 4, this toolcan extend the linear range of the calibration curve. Thecharacteristic masses that were found are similar to thosetypically obtained by GFAAS. As expected, the LODs are verylow, excepting those of Co and Ni. The presence of Mg(NO3)2

increased the blank signal in the case of Co. Regarding to Ni,the precision was poorer by using the carbon powder-coveredplatform, which worsened the LOD, but it proved to be usefulin minimizing the observed memory effect. The LODs wereobtained from 3s, s being the standard deviation of 10 con-secutive runs of the blank (the platform containing only themodier, or the carbon powder-covered platform in the case of

Table 5 Trace elements (in gg1) determination in paints using different techniques

Sample Technique Cd Co Cr Cu Ni Pb

SerigraphyBlack DS-GFAAS


Ni). The maximum sample amount employed was also takeninto account for calculating the LOD of each element.

3.2.4. Paint analysis by DS-GF AASThe elements concentrations determined by DS-FGAAS areshown in Table 5. The accuracy was checked by comparisonof the results with those obtained by ICP-MS and GFAAS usingsolution of the digested sample. According to Table 5, theresults obtained by DS-GF AAS agree with those obtained byGF AAS. However, not all results obtained by ICP-MS agree,possibly due to the matrix inuence. Although the solutionsof the digested samples were diluted, matrix interference wasstill observed in ICP-MS [18,19], which was veried throughrecovery tests. The results shown in Table 5 demonstratethat calibration with aqueous standards can be employed fortrace elements determination in paints by DS-GF AAS. Thisis very important because it is difcult to have paint stan-dards for calibration. Furthermore, by using solutions thecalibration of the DS-GF AAS system is more exible andeasier.

4. Co

It was for tused for dein general,low and nothe analysiduction. Aqin spite thetion neededbe appliedmass to bethe sampleModiers asive for minindicate thments detemay also btions.

Acknowledgements

The authors are grateful to CAPES for the Fabrina R.S. Bentlinscholarship.

r e f e r enc e s

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Standard Test Method for Low Concentrations of Lead,Cadmium and Cobalt in Paint by Atomic AbsorptionSpectroscopy, 2005.

[9] I. Deconinck, C. Latcokoczy, D. Gunther, F. Govaerth, F.nhaecke, J. Anal. At. Spectrom. 21 (2006) 279.Desnta BM. GoectroKurfmplialysM. DKrivaM. D.G.R.v. 41.A. BeectroH. TaM. Re994) 8F. Rodores,nclusion

he rst time demonstrated that DS-GF AAS can betermination of trace elements in paints that are,very complex matrices. The detection limits aresample decomposition is needed, which simpliess, reduces reagents consumption and waste pro-ueous standards can be used for calibration and,very complex matrix, the only sample prepara-is homogenization. In principle, the method canto different types of paints. The proper sampleused is about 0.5mg, but it may vary depending ontype, element and its concentration in the paint.nd atomization temperature are markedly deci-imizing matrix interference. The results obtained

e potential of the developed method for trace ele-rmination in small amounts of sample, whiche useful in forensic and archeometry investiga-

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Flica, K. Furic, B. Hochleitner, M. Mantler, Spectrochim.58 (2003) 681.ltz, D.C. Gregoire, C.L. Chakrabarti, Can. J. Appl.sc. 41 (1996) 70.urst, General aspects of the graphite furnace solidng method, in: U. Kurfurst (Ed.), Solid Sampleis, Springer-Verlag, Berlin, Heidelberg, 1998.ong, V. Krivan, Spectrochim. Acta B 56 (2001) 1645.n, H.M. Dong, Anal. Chem. 70 (1998) 5312.ong, V. Krivan, J. Anal. At. Spectrom. 18 (2003) 367.Vale, N. Olesczuck, W.N.L. Santos, Appl. Spectrosc.(2006) 377.larra, C. Crespo, M.P. Martnez-Garbayo, J.R. Castillo,chim. Acta B 52 (1997) 1855.n, G. Horlick, Appl. Spectrosc. 40 (1986) 445.ed, R.O. Cairns, R.C. Hutton, J. Anal. At. Spectrom. 981.rigues, J.C.P. Mattos, V.L. Dressler, D. Pozebon, E.M.M.Spectrochim. Acta B 62 (2007) 933.

Determination of trace elements in paints by direct sampling graphite furnace atomic absorption spectrometryIntroductionExperimentalInstrumentation and operating conditionsReagents and samplesSample preparation and procedure

Results and discussionMajor and minor elements determinationDS-GF AAS method developmentFurnace program and modifiersSample mass influenceAnalytical characteristics of the methodPaint analysis by DS-GF AAS

ConclusionAcknowledgementsReferences

determination of trace elements in paints by direct sampling graphite

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