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.Spectrochimica Acta Part B 55 2000 1643 1657

Determination of barium, chromium, cadmium,manganese, lead and zinc in atmospheric particulate

matter by inductively coupled plasma atomic emission /spectrometry ICP-AES

Iv. Boevski, N. Daskalova , I. Havezov Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, BG 1113 Soa, Bulgaria

Received 8 June 2000; accepted 29 June 2000

Abstract

The present paper has shown that the Q concept, as proposed by P.W.J.M. Boumans, J.J.A.M. Vrakking, .Spectrochim. Acta Part B 43 1988 69, can be used as a basic methodology in the determination of Ba, Cr, Cd, Mn,

.Pb and Zn in pairs of atmospheric particles by inductively coupled plasma atomic emission spectrometry ICP-AES . . .The data base of Q values for line interference Q and Q values for wing background interference Q Ij a WJ a

were obtained in our former work N. Daskalova, Iv. Boevski, Spectral interferences in the determination of traceelements in environmental materials by inductively coupled plasma atomic emission spectrometry, Spectrochim. Acta

. rtB 54 1999 1099 1122 . The samples of atmospheric particles were collected by the Bergerhoff method. TheICP-AES determination was performed after sample digestion with aqua regia. Q values were used for thecalculation of both the total interfering signal under the analysis lines and the true detection limits, depending on thematrix constituents in the different samples. Comparative data for the concentration of analytes were obtained by

. ame atomic absorption spectrometry FAAS and direct current arc atomic emission spectrographic method dc.arc-AES . 2000 Elsevier Science B.V. All rights reserved.

Keywords: ICP-AES; Q-concept; Atmospheric particulate matter; Trace elements; Correction procedure; Truedetection limits

Corresponding author. Tel.: 3592-979-2543; fax: 3592-70-50-24. . E-mail address: [email protected] N. Daskalova .

0584-8547 00 $ - see front matter 2000 Elsevier Science B.V. All rights reserved. .PII: S 0 5 8 4 - 8 5 4 7 0 0 0 0 2 6 5 - 2

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( ) I . Boe ski et al. Spectrochimica Acta Part B: Atomic Spectroscopy 55 2000 1643 1657 1644

1. Introduction

At present at least, accurate analysis of envi-ronmental materials other then natural or waste waters requires dissolution of the samples. Thereare a large number of possible objectives for thistype of analysis, including verication that amaterial is legally dened as hazardous waste:soils, sediments, sludges, atmospheric particulatematter, mine tailing, industrial wastes, etc. Themost commonly used procedure for this analysisis to solubilize the samples in question using anacid digestion procedure and analyze the result-

ing liquid digestate by ame atomic absorption .spectrometry FAAS , electrothermal atomic ab- .sorption spectrometry ETAAS , inductively cou-

pled plasma atomic emission spectrometry ICP-. AES or inductively coupled plasma mass spec-

.trometry ICP-MS . Less common techniques suchas glow discharge and laser-induced breakdownspectrometry have been used in the analysis of

gaseous species 1 6Instrumental methods are used to monitor air-

borne particulates outdoors 6 and in industrial

workplaces to safeguard occupational health 7 9 .The coarse atmospheric aerosol fraction par-.ticles with aerodynamic diameter above 100 m

determines dry sedimentation. The routes of thistype of aerosol exposure may involve skin deposi-

tion, the food chain after deposition on soils,. waters, plants, etc. and inhalation 8 . The nature

and magnitude of the hazards in a given situationdepend on a complex combination of many fac-tors, including particle size distribution, wind-speed range, airborne concentration, particle

morphology, mineralogy and chemical composi-tion. The chemical analysis of atmospheric parti-cles is of great interest in order to estimate thesource and trend of atmospheric pollution. Thecontent of toxic pollutants of atmospheric parti-cles is of interest for industrial hygiene chemistry.The main functions of industrial hygiene chem-istry are screening for chemical stressors duringthe recognition phase and monitoring of specic

hazard concentrations during the evaluation 10 .The application of the ICP-AES to air quality

monitoring is now widespread 6 . It is commonknowledge that spectral interference is the mostsevere problem. However, the question of what it

actually is, why it is such a severe problem, and what progress has been made in recent years tocope with it, remains. The matrix may substan-tially worsen the accuracy and true detectionlimits, and affect line selection, chiey because of

spectral interference 11 . A detailed experimental study of spectral inter-

ferences in ICP-AES in the analysis of a varietyof complex environmental materials has beenshown in a previous paper. Spectral data for Al,Ca, Mg, Fe, Ti, K and Na as interferents for

.200-pm wide windows centered 100 pm aroundthe prominent lines of As, B, Ba, Be, Cd, Cr, Cu,Hg, Mn, P, Pb, Sb, Se, Sn, Tl, U and Zn and aquantitative data base of Q values for line inter-

.ference Q and for wing background inter- I a . ference Q were obtained 12 . The Q-W a

concept, as proposed by Boumans and Vrakking, was used for the quantication of the spectral

interferences 13,14 .The purpose of this work was to demonstrate

experimentally the possibilities of ICP-AES by

using a data base of Q values 12 in the determi-nation of Ba, Cr, Cd, Mn, Pb and Zn in atmo-spheric particulate matter. Comparative data forthe concentration of the above-mentioned ele-ments will be obtained by the ame atomic ab-

.sorption spectrometry FAAS and the direct cur-rent arc atomic emission spectrographic method .dc arc-AES .

2. Experimental

2.1. Instrumentation

.The Jobin Yvon Longjumeau, France equip-ment and the operating conditions used in theICP-AES experiments are specied in Table 1.

The FAAS measurements were performed withPye Unicam SP 192 spectrometer, using the mostsensitive lines of the elements under the operat-

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Table 1Specication of the spectrometer, ICP source and operating conditions

. Monochromator JY 38 Jobin Yvon, FranceMounting Czerny Turner, focal length 1 m

1Grating Holographic, 2400 grooves mm .Wavelength range 170 700 nm rst order

1Dispersion 0.38 nm mmEntrance slit 0.02 mmExit slit 0.04 mmResultant spectral slit 15.2 pmPractical spectral band width 15.6 pmPhotomultiplier Hamamatsu TV, R 446 HA

Rf generator Plasma Therm, model HFP 1500 D .Frequency 27.12 MHz 0.05%

Oscillator Crystal controlled at 13.56 MHz

Power output 0.5 1.5 kWNebulizer Meinhard, concentric glassPump Peristaltic, ten-roller, Gilson Minipuls

.Gilson Medical Electronics, France

Operating conditionsIncident power kW 1.0

1 .Outer argon ow rate l min 151 .Carrier ow rate l min 0.4

1 .Liquid uptake rate ml min 1.32 . .Nebulizer pressure ow lbf in 20 1.38 bar

Transport efciency of ICP system % 3Excitation temperature

of ICP plasma K 7200

ing conditions recommended in the manuals, in-cluding deuterium background correction.

Table 2 shows the specication of the spectro-graph, dc power generator and operating condi-tions.

2.2. Reagents

Reagents of the highest purity grade were used: .30% HCl Suprapur, Merck ; 65% HNO 3 .Suprapur, Merck ; and tridistilled water from a

quartz apparatus. Stock solutions of the analyte 11 .mg ml were prepared from Merck Titrisols.

PTFE ware was used throughout.

2.3. Sampling

The samples were collected by Bergerhoffs

method 15 from four separate spots around ametallurgical company in Soa, Bulgaria. Thesamples were air dried and ground in a rotatingplastic drum and were delivered for analysis tothe Institute for Hygiene and OccupationalHealth, Soa.

2.4. Digestion procedure

The extraction of trace elements soluble in .aqua regia ISO 11466:1995 E was used as a

decomposition method for reasons outlined in our previous paper 12 .

A 0.5-g sub-sample was weighed in a reaction vessel; 0.5 ml of tri-distilled water was added to

obtain a slurry, followed by 4.5 ml of HCl 12 mol1 . 1 .l and 1.5 ml HNO 15.8 mol l . Then 10 ml3

of 0.5 mol l 1 HNO were added to the absorp-3

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Table 2Specication of the spectrograph, dc power generator and operating conditions

.Spectrograph PGS-2 Jena, GDR1Grating Ruled, 650 groves mm

-blaze 570 nmRegistered spectrum In the second orderIllumination system One lens, quartz condenser,

f 80Slit width 20 m

.Hartmanns diaphragms S-10 7, 3, 2D.C. power generator Three phase rectier, 280 V, 20 A Operating conditionsCurrent 10 s

.Exposure time 30 s Cd, Zn .60 s Cr .80 s Ba, Mn

Electrodes RW-0 Ringsdorf-Werke GMBH,.Mehlem

Electrode shape Crater 3. 5 mm diameter,4. 0 mm depth the electrode with

.Sample set as anode ; half-sphere .upper electrode

Electrode spacing 4 mm Amount of sample 10 mg

.Spectral plates WU-2 ORWOWavelength of analysis Ba I 307 159 pm ; Cd I 326 106 pmProminent lines Cr II 283 563 pm ; Mn II 293 930 pm

Pb I 283 306 pm ; Zn I 328 233 pm

tion vessel and connected with the reux con-denser. Both apparatus were placed on the top of the reaction vessel and the sample was allowed tostand for 16 h at room temperature for slowoxidation of the organic matter and reduction of the gases produced during the subsequent heatingcycle. They were heated under reux until boilingfor 2 h and allowed to cool slowly at room tem-perature. The contents and the subsequent rinsesof the absorption vessel were passed through thecondenser into the reaction vessel. The content of

the reaction vessel was transferred quantitativelyto a 25-ml graduated ask and lled up to themark with 0.5 mol l 1 HNO . After the undis-3solved material had settled, the supernatant solu-tion was subjected to analysis by ICP-AES orFAAS. A blank sample containing the acids usedfor digestion was prepared in the same way

All glass and plastic ware were kept in 10% v vHNO for at least one night and then rinsed with31% v v HNO , and subsequently with distilled3 water before use.

2.5. Calibration procedures

2.5.1. ICP-AES and FAASThe reference solutions for the determination

of the analytes were prepared on the basis of ablank containing the acids used for digestion anda complex matrix. The number of reference solu-tions for any particular analyte ranged from 5 to20, depending on the necessary concentrationrange. It was not necessary to run all 20 referencesolutions for each calibration.

2.5.2. dc Arc-AESCertied standard reference materials: IAEA

marine sediment SD-N-1 2; IAEA lake sedi-ment SL-1; IAEA SOIL-5; and IAEA SOIL-7 were used for calibration. These reference mate-rials could be used for calibration for the fol-lowing reasons:

1. they were of approximately the same mineralcomposition;

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2. the reference materials were ground to 100m in a rotating plastic drum. Such grinding

is designed to give a homogeneous sample

from which a sub-sample is taken; and3. the concentration level of the analytes

permitted the analysis of samples in a wideconcentration range.

3. Results and discussion

3.1. ICP-AES method

3.1.1. Data base of Q- aluesSpectral interferences, especially line overlaps,

are a major problem in atomic emission radiationsources, but it is emphasized with the ICP be-cause of the richness of the spectra. The ICPemits lines which do not appear in the classical

tables 16,17 . The relative intensities of the spectral lines emitted by the classical sources 16,17

and the ICP 18 are different. These are thereasons why various groups of workers have em-barked upon the compilation of new data relevant

to ICP 12,19 23 . A detailed experimental studyof spectral interferences in ICP-AES encountered with environmental materials was shown in our

previous work 12 . Table 3 lists the prominentlines of analytes: Ba, Cd, Cr, Mn, Pb and Zn,

.Q values for wing background interference w a .and Q values for line interference in the I a

presence of 2 mg ml 1 Al, Ca, Mg, Fe and Ti, .respectively, as interferents. The term Q is I a

. .expressed as the ratio S S , where S is I a A I athe partial sensitivity of the interfering line, de-

ned as the signal per unit interferent concentra-tion produced by the interfering line at the peak wavelength of the analysis line , and S is the a A

sensitivity of the analysis line signal per unit. .analyte concentration . The term Q is ex- w a

. .pressed as the ratio S S , where S w a A w ais the wing sensitivity of the interfering line in thespectral window and S is as stated above. a AThe best analysis lines in the presence of acomplex matrix are printed in bold.

.These data were used for: a the determina-

tion of the true detection limits in the case of a . multicomponent system by using Eq. 1 23 :

.C 2 5 Q C C L ,true J I J a I J L ,conv .2 5 BEC C 1 J I J L ,conv

where the conventional detection limit can be written as:

' C 2 2 0.01 RSDBL BEC L ,conv . . jQ C Q C I J a I J J W J a I J

'2 2 0.01 RSDBL .BEC BEC BEC 2 J I J J W J

.and b calculation of the interfering background signals BEC BEC under the promi- J I J J W J

nent analysis lines for the samples with differentmatrix concentrations.

The total background signals under the bestanalysis lines included the background equivalent

concentration in the solvent blank due to source.and solvent , i.e. BEC BEC BEC Total J I J

BEC . J W J Table 4 shows the interferent matrix concentra-

.tions C for which Q 0 by using equation I J I J a . Q C C 23 . Table 5 lists the wave- I J a I J L

lengths of all prominent lines of analytes, thebackground equivalent concentration BEC, g

1 . 1 .ml and the detection limits C , g ml in L .the pure solvent acids used for digestion

obtained under our experimental conditions Ta-. . ble 1 by using Eq. 3 23 :

' .C 2 2 0.01 R.S . D . B BEC 3 L

where R.S.D.B 1% is the relative standard devi-ation of the background; and BEC is the back-

1 .ground equivalent concentration in g ml .

3.1.2. Analysis of samples of atmospheric particulate matter

Four samples of atmospheric particles werecollected by the Bergerhoff method from separate

spots around a metallurgical company Section.2.3 .

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3.1.2.1. Determination of major components. TheICP-AES determination of matrix components Al,

Ca, Fe, Mg and Ti was performed after digestion . with aqua regia Section 2.4 . The accuracy was

Table 3a . .Values of Q and Q for prominent lines of Ba, Cd, Cr, Mn, Pb and ZnW a I a

. . Analysis lines Interferents Q Q W a I a .pm

Ba II 455 404 Al 0 06Ca 9.0 10 0

Fe 0 05Mg 4.5 10 06Ti 2.6 10 0

6Ba II 493 409 Al 2.0 10 06Ca 7.4 10 07 5

Fe 5.0 10 4.0 107Mg 4.0 10 06Ti 3.3 10 0

6Ba II 233 527 Al 2.6 10 05Ca 5.2 10 05 5Fe 5.6 10 6.1 105Mg 1.7 10 05Ti 4.4 10 0

Ba II 230 424 Al 0 05Ca 7.2 10 05 5Fe 2.9 10 4.1 105Mg 2.3 10 05Ti 5.0 10 0

Cd II 214 438 Al 0 04Ca 1.3 10 04Fe 6.0 10 0

Mg 0 04Ti 8.5 10 0

5Cd I 228 802 Al 6.6 10 04Ca 7.0 10 04Fe 6.3 10 04Mg 4.8 10 04Ti 4.7 10 0

6 5Cd II 226 502 Al 6.0 10 5.7 104Ca 4.0 10 05Fe 9.1 10 0

Mg 4.7 10 4 04Ti 7.0 10 0

4Cr II 205 552 Al 3.4 10 04Ca 3.6 10 05 4Fe 7.0 10 1.1 104Mg 2.5 10 04Ti 2.0 10 0

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.Table 3 Continued

. . Analysis lines Interferents Q Q W a I a

.pmCr II 206 149 Al 0 0

4Ca 4.2 10 04Fe 2.2 10 04Mg 3.2 10 04 4Ti 1.9 10 1.8 10

Cr II 267 716 Al 0 05Ca 1.2 10 05Fe 6.7 10 05Mg 3.7 10 05 5Ti 1.2 10 2.7 10

Cr II 283 563 Al 0 06Ca 2.8 10 06 3Fe 5.7 10 1.0 104Mg 1.3 10 0

5Ti 0 2.7 10

6Mn II 257 610 Al 4.7 10 06Ca 5.5 10 05Fe 1.1 10 06Mg 9.5 10 06Ti 4.7 10 0

Mn II 259 373 Al 0 06Ca 4.7 10 05 40Fe 1.7 10 6.9 106Mg 8.8 10

5Ti 3.5 10 6 3.7 10

4 4Pb II 220 353 Al 9.7 10 4.0 104Ca 5.3 10 04Fe 4.1 10 04Mg 4.5 10 04 5Ti 5.2 10 5.510

3 3Pb I 216 999 Al 2.8 10 4.0 103Ca 2.1 10 04 3

Fe 6.9 10 1.0 10Mg 1.7 10 3 0

3Ti 1.3 10 0

5Pb I 261 418 Al 9.1 10 04Ca 4.1 10 03 2Fe 6.3 10 1.1 104Mg 3.2 10 04 4Ti 2.8 10 1.4 10

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.Table 3 Continued

. . Analysis lines Interferents Q Q W a I a .pm

Pb I 283 306 Al 0 04Ca 3.5 10 0

3Fe 0 3.6 103Mg 3.8 10 04 4Ti 3.3 10 5.3 10

5Zn I 213 856 Al 4.1 10 05Ca 2.7 10 0

4Fe 0 1.1 10Mg 0 0

5 5Ti 1.7 10 3.0 10

4

Zn II 202 548 Al 1.4 10 04Ca 2.2 10 05Fe 9.8 10 04 4Mg 3.1 10 4.0 104Ti 1.2 10 0

4Zn II 206 200 Al 3.0 10 04Ca 1.8 10 05Fe 7.4 10 04Mg 1.5 10 04Ti 1.1 10 0

a 1 . 1 . 1 . 1 . Interferents: aluminium 2 mg ml , calcium 2 mg ml , iron 2 mg ml , magnesium 2 mg ml and titanium 2 mg1 .ml .

improved by using two selected analysis lines foreach element: Al I 237 324 pm; Al I 394 401 pm;Ca I 422 673 pm; Ca II 315 887 pm; Fe II 238 204pm; Fe II 239 562 pm; Mg II 279 806 pm; Mg II285 213 pm; Ti II 334 941 pm; and Ti II 336 121

pm 11 .The basic sample solutions were diluted dilu-

.tion factor 4 in order to eliminate the multi-plicative interferences due to the matrix con-

stituents 12 . The reference solutions were pre-

pared on the basis of an acid blank Section.2.5.1 .The results obtained in g ml 1 are presented

in Table 6. The R.S.D. is 5%.

3.1.3. Determination of impurities of Ba, Cd, Cr, Mn, Pb and Zn

3.1.3.1. Determination of contaminations in sol - ent blank solutions. Random errors, which, due tocontaminations of the solvent blank with a givenanalyte, can be eliminated by the determination

of Ba, Cd, Cr, Mn, Pb and Zn in solvent blanksamples. The blank samples, containing the acidsused for digestions was prepared following the

.digestion procedure Section 2.4 . The back-ground was corrected for by a simple off-peakbackground measurement.

3.1.3.2. Calculation of the total background sig - nals under the best analysis lines. By using the

. . .Q and Q values Table 3 for the I J a W J abest analysis lines, the interferent concentra-

. .tions in sample solutions C Table 6 the back- I J ground equivalent concentration for line interfer- .ence BEC Q C BEC J I J J I J I J I Al

BEC BEC BEC BEC Table 7, I Ca I Mg I Fe I Ti.column 2 , the background equivalent concentra-

tion for wing interference BEC J W J J .Q C BEC BEC BEC I W I J W Al W Ca W Mg

.BEC BEC Table 7, column 3 and theW Fe W Tibackground equivalent concentrations in pure

.solvent Table 5 , the total background signals BEC BEC BEC at the peak wave- J I J J W J

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Table 4 .Interferent concentrations C for which Q 0 for aluminium, iron and titanium as a matrix elements I J I J a

Analysis lines Interferent concentrations C , g ml 1 I J . .pm for which Q 0 I J a

Aluminium Iron Titanium

Ba II 455 403 Ba II 493 409 20 Ba II 233 527 70 Ba II 230 424 140

Cd II 214 438 Cd I 228 802 Cd II 226 502 100 Cr II 205 552 120 Cr II 206 149 120

Cr II 267 716 200Cr II 283 563 710 260

Mn II 257 610 Mn II 259 373 2 35

Pb II 220 353 125 900Pb I 216 999 40 150 Pb I 261 418 20 1300Pb I 283 306 60 4100

Zn I 213 856 50 150Zn II 202 548 Zn II 206 200

length of the analysis lines were measured a .Table 7, column 4 . For a given matrix composi-

.tion Table 6 the following should be noted:

1. The interferent Ti concentrations for thebest analysis lines of Cr and Pb for which

. Q 0 were signicantly higher Table I Ti a

.4 in comparison with the corresponding val- .ues in sample solutions Table 6 : C ranged I Ti1 .from 4.8 to 6.6 g ml . Hence, in both

cases BEC BEC BEC , i.e. I Ti J W J BEC could not inuence both the total I Tibackground correction factor and the true

.detection limit C C . L ,true L ,conv2. The interferent Al concentrations for the

best analysis line of Pb for which Q 0 I Al .Table 4 were lower in comparison with theinterferent concentrations in sample solutions

.Table 6 : C ranged from 183 to 265 g I Alml 1. Hence, in the determination of Pb inatmospheric particulate matter the back-ground under a prominent line varied withthe sample composition. These values ranged

1 from 0.07 to 0.11 g ml Table 7, column.2 , whereas the total background signals

. 1

BEC varied from 2.41 to 2.93 g mltotal .Table 7 , i.e. BEC BEC . Due to the I Al tota lhigh total background signals, the lower inter-ferent signals BEC could not be distin- I Al

.guished, i.e. C C . Fig. 1 presents L ,true L ,convexamples of spectral scans over a spectralregion around the analysis line Pb II 220 353

. 1pm: 1 10 g ml lead in pure solvent; and . l2 matrix blank 270 g ml Al, 1250 gml 1 Ca, 170 g ml 1 Mg, 1300 g ml 1 Fe,7 g ml 1 Ti. This was a real situation in the

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Fig. 1. Example of spectral scans over a spectral region around .the analysis line of lead: 1 central wavelength 222 353 pm

. 1 .Pb line 10 g ml Pb in pure solvent; and 2 complex matrix bland 270 g ml 1 Al 1250 g ml 1 Ca 170 gml 1 Mg 1300 g ml 1 Fe 7 g ml 1 Ti.

determination of lead in sample 3 the con-centration of matrix elements was higher incomparison with the concentration of the

.same elements in samples 1 3 Table 6 . Thebackground enhancement could be correctedfor by a simple off-peak background measure-ments.

By using the total background correction fac-tor, the content of Ba, Cd, Cr, Mn, Pb and Zn in

1 .g g were obtained Table 8, column 1 . It

should be noted that the contamination from Mnand Zn was registered in solvent blank samples

.and its concentration determined Section 3.1.3.1 .

The analytical results for Mn and Zn wereobtained by correction of both the spectral inter-ferences and analyte concentrations in solventblank samples.

3.1.3.3. Detection limits. In Section 3.1.3.2, it wasshown that BEC 0 for the samples 1 4. J I J Hence, the true detection limits conventional

.detection limits. By using Eq. 2 in combination . with Q-values Table 3 and interferent concen-

.trations for Al, Ca, Fe, Mg and Ti Table 6 , the 1conventional detection limits in ng ml , column

.2 and the same detection limits with respect to 1 .the dissolved solid in g g , column 3 were

.calculated Table 9 .

Table 5The wavelengths of all investigated prominent lines in this

work, the background equivalent concentration BEC, g1 . ml and the detection limits in the pure solvent C , ng L1.ml

1 1 . . Analysis lines BEC g ml CL ng ml .pm

Ba II 455 403 0.02 0.65Ba II 493 409 0.03 0.79Ba II 233 527 0.14 4Ba II 230 424 0.20 5.7

Cd II 214 438 0.30 8.3Cd I 228 802 0.20 5.7Cd II 226 502 0.20 5.7

Cr II 205 552 0.40 12Cr II 206 149 0.70 21Cr II 267 716 0.20 5.7Cr II 283 563 0.25 7.1

Mn II 257 610 0.04 1.2Mn II 259 373 0.04 1.2

Pb II 220 353 1.30 37Pb I 216 999 5.00 140Pb I 261 418 6.30 180Pb I 283 306 7.60 216

Zn I 213 856 0.16 4.5Zn II 202 548 0.30 8.5Zn II 206 200 0.40 12

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The results from Tables 8 and 9 showed thefollowing:

1. By using the best analysis line, the concen-trations of Cd in samples 1 and 2 were in the vicinity of the detection limit concentrationlevels and could be determined with a desiredlevel of precision.

2. In most cases, the analyte concentration de-termined by the best analysis lines substan-

tially exceeded the detection limits Tables 8.and 9 . When the analyte concentration sub-

stantially exceeded the detection limits as in.the case of Ba, Cr, Mn, Pb and Zn the use of

a second analysis lines with Q 0 was justi- I J ed. In such cases the equation Q C I J I J C was used. The interferent concentration L

.C for which Q 0 Table 4 and the dilu- I J I J tion factor of the sample solution were de-termined. When necessary, more than twoanalysis lines could be used for improving the

accuracy and precision of an analytical de-termination.

3.2. FAAS method

ICP-AES and FAAS are principally intendedfor the determination of impurities in liquids. Thegreatest contrast between ICP-AES and FAASlies in the domain of inter-element interferences.The type of interferences most commonly en-countered in each of the two techniques is virtu-ally mutually exclusive. In FAAS, inter-elementinterferences are mostly chemical in nature,

whereas spectroscopic interferences such as lineoverlaps are virtually non-existent. In ICP-AES,the opposite is true. With an appropriate choiceof plasma operating conditions, chemical interfer-ences are reduced to negligible proportions, but,in turn, the spectral interferences are the basic

problem 6 . The characterization of, and correc-

Table 61 a .Content of Al, Ca, Mg, Fe and Ti in solution g ml derived after dissolution of the different samples

1

. Analysis Concentrations g mllines, Sample 1 Sample 2 Sample 3 Sample 4 .pm

X X X X X X X X i i i i

Al I 237 324 204 220 260 180202 219 265 183

Al I 394 401 200 218 270 186

Ca I 422 673 1120 1045 1250 10481115 1049 1249 1051

Ca II 315 887 1110 1053 1248 1054

Mg II 279 806 150 160 172 100148 161 169 103

Mg II 285 213 146 162 166 106

Fe II 238 204 980 1050 1280 610990 1046 1275 615

Fe II 239 562 1000 1042 1270 620

Ti II 334 941 5.8 5.4 6.5 5.05.9 5.5 6.6 4.8

Ti II 336 121 6.0 5.6 6.7 4.6a Notes: X i is the mean of three replicates by using a given analysis line; X is the mean values of two concentrations, obtained by

using two analysis lines of each analyte.

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Table 71 .The background equivalent concentration for line interference BEC , g ml column 2 , background equivalent concentration I J

1 . for wing background interference BEC , g ml column 3 and total background signal at the peak wavelength BECW J a Total,1 .g ml column 4 for the best analysis lines

The best Sample BEC , BEC , BEC , J I J J W J Total1 1 1analysis lines No g ml g ml g ml

.pm

Ba II 455 403 1 0 0.017 0.252 0 0.017 0.253 0 0.019 0.254 0 0.014 0.24

Cd II 214 438 1 0 0.75 1.052 0 0.78 1.083 0 0.94 1.244 0 0.51 0.81

Cr II 267 716 1 0 0.120 0.372 0 0.12 0.373 0 0.15 0.404 0 0.09 0.34

Mn II 257 610 1 0 0.02 0.062 0 0.04 0.083 0 0.06 0.104 0 0.02 0.06

Pb II 220 353 1 0.08 1.27 2.652 0.09 1.28 2.673 0.11 1.52 2.934 0.07 1.04 2.4

Zn II 206 200 1 0 0.36 0. 762 0 0.34 0.743 0 0.43 0.834 0 0.30 0.70

tion for, various spectroscopic interferences en-countered in the determination of Ba, Cd, Cr,Mn, Pb and Zn in atmospheric particulate matter

has been shown in Section 3.1. Comparative datafor the concentration of above-mentioned ana-lytes were obtained by FAAS as an alternativemethod for the analysis of the same sample solu-

.tions Table 8, column 2 .

3.3. dc Arc-AES method

The dc arc-AES method for the analysis of solid samples of atmospheric particulate matter was used. The specication of the spectrograph,

dc power generator and operating conditions forthe direct spectral determination of Ba, Cd, Cr,Mn, Pb and Zn in samples 1 4 are listed in Table

2. The concentrations of the analytes are shown .in Table 8 column 3 .Using Students criterion, no statistical differ-

ences between the results obtained by the ICP- AES, FAAS and dc arc-AES methods was found.It followed from the results that Ba, Cd, Cr, Mn,Pb and Zn are soluble in aqua regia, and Q-val-ues provided a realistic estimation of the interfer-ence effects and could be used for the calculationof the total interfering background signals underthe prominent analysis lines.

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Table 8Element determination in couples of atmospheric particulate

.matter mean of three replicates

1Sample Element Concentrations, g gNo ICP-AES FAAS dc Arc-AES

1. Ba 695 10 707 10 690 25Cd 1.52 0.05 1.53 0.05 1.58 0.1Cr 250 5 242 5 245 20Mn 355 8 356 6 360 15Pb 165 5 176 5 169 10Zn 495 10 495 10 510 25

2. Ba 2000 5 2010 5 2025 20Cd 2.15 0.05 2.16 0.05 2.18 0.1Cr 475 10 470 10 465 20

Mn 1800 6 1805 5 1810 20Pb 265 5 270 5 275 20Zn 715 8 710 6 698 25

3. Ba 2148 5 2152 5 2150 20Cd 33.0 0.05 32.5 0.05 34.0 0.1Cr 85.0 5 88.0 5 84.0 10Mn 790 5 790 5 788 15Pb 288 5 285 5 282 10Zn 1280 5 1285 5 1278 15

4. Ba 1600 5 1605 5 1598 15Cd 8.70 0.05 8.68 0.05 8.65 0.1

Cr 138 5 138 5 140 10Mn 385 5 390 5 383 10Pb 176 5 178 5 170 10Zn 1170 5 1165 5 1162 12

3.4. Conclusion

The background under a spectral line cannotbe directly determined and, in addition, it varies

. with the sample composition Table 6 . It mightappear from the literature that a variety of instru-mental background correction procedures exist. All approaches are based on the visual inspectionof wavelength scans of samples, standards, andblanks to make a judicious choice of the wave-lengths at which the background is measured.The ideal background correction requires the si-multaneous collection of accurate data on analyti-cal and background signals under the prominentanalysis lines. The Q-concept ensures a possibility

for the quantication of the spectral interferencesin the presence of Al, Ca, Fe, Mg and Ti as abasic interferents in environmental materials for

.a relevant set of analysis lines Table 3 . Thesedata were used for:

1. quantitative line selection: the best analysislines are free or negligibly inuenced by line

.interference Table 3 ;2. calculation of the interfering background sig-

nals BEC BEC under the J I J J W J prominent analysis lines for the samples with

.different matrix concentrations Table 7 . Thetotal background signals under the best

analysis lines includes the background equiva-lent concentration in the solvent blank due.to source and solvent , i.e. BEC BECTotal

BEC BEC ; and J I J J W J 3. calculation of the true detection limits in this

.case C , C , ; Table 9, column 1 L true L conv. which can determine the vicinity of the detec-

tion limit concentration levels Table 8, sam-.ples 1 and 2, content for Cd .

The results obtained in the determination of Ba, Cd, Cr, Mn, Pb and Zn in samples of atmo-spheric particulate matter by ICP-AES methodagree well with the corresponding values obtained

by both FAAS and dc arc-AES methods Table.8 . It should be noted, however, that the dc arc-

AES method is a direct method for the analysis of solid samples. In this way, the efciency of extrac-tion of Ba, Cd, Cr, Mn, Pb and Zn from samplesof atmospheric particulate matter in aqua regia was experimentally demonstrated. Hence, theselected digestion procedure provides enough in-formation about the hazardous waste contribu-tion, such as Ba, Cd, Cr, Mn, Pb and Zn.

Acknowledgements

Thanks are due to the National Found Scien-tic Research of the Ministry of Education, Sci-ence and Technology of Bulgaria for nancialsupport of this work under registration N X-544.

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Table 91 1 . .Conventional detection limits ng ml and the same detection limits with respect to the dissolved solid in g g

Sample Best analysis C C L, conv. L ,conv.1 1 . .No lines, pm ng ml g g

1. Ba II 455 403 7.0 0.352. 7.0 0.353. 7.0 0.354. 7.0 0.35

1. Cd II 214 438 30.0 1.502. 31.0 1.553. 35.0 1.754. 23.0 1.15

1. Cr II 267 716 10.5 0.53

2. 10.5 0.533. 11.3 0.574. 9.6 0.48

1. Mn II 257 610 1.7 0.092. 2.3 0.103. 2.8 0.144. 1.7 0.09

1. Pb II 220 353 75.0 3.752. 75.0 3.783. 83. 0 4.154. 68. 0 3.40

1. Zn II 202 548 19.0 0.952. 19.0 0.953. 21.0 1.104. 17.5 0.88

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