Delennination of Chromium in AirborneParticulates by

Alomic Absorption SpectrophOlome!ry

1. INTRODUCTION

(1'lJomium is uoed principoUy in ,11< manuf",u", of>lui and otll., Illoy. Orfo' chrome pI..in•. O1romil. 0"', FeO, C"O., is ,he moo' imp"'tan'5OU''''' of chromium. Th. 0"', be<:.use of ito hi'" ,••istana: to heu, is ul<dto monufo"u", ",1,o"'ori<$. Chromium, findinK ill w.y inlO th. lir f,omthe meulIwgiCll indu"ry, is p,obably in ,he ,rivalent Or >e,O "'. The'o~icity of rrh.J.n, cllromitlm h.. nor bun d.monll d (l2 I).Chromium I<"luioxide, an ou",mely in50lubl< oomJ>OUnd, is prob.bly themos' .bundant fonn of wbom. lri..:l.nt chromium. Di....I.nt chromitlmrompounds .'" 50 ..sily o~idiud ,hat tl1.y cmnot be .~pect.d in ambien',iI. H.xa.,..l.n, chromium, In ,he li', prob.bly origin.t•• from tll.prOO""tion of chromo'" and dkhrom.,.. by ,It< ,It<mieol industry. Theh.ighly cnlo"'d salll of chromium hove be.n used os piimento and ..moldanu in the tutil. indus'!)'. H.u....lent chromium rompound, 0'".. t,..mely ,oxic. Con1OC' wi'h tit< 'kin should be av(liaed and inlla!>'ion ..duo' coo seve,.ly i"iut. the n...1 muco.. and ,••pifllOry trOCt, Inge"ion""'y be f"al

Gravim..ric tilrime,ric and colorime,ric metllod. fo, chromiumrkt.nninotion hove bun of hmit.d US< in li' qUllity "udin Th. Weisz dnaoven method hu been ""'d '0 m"'Ur< the chromium con,.nt ofpo"kuis'" coll«,.d on ..mple upes, wi'h I d<lection Umit ofO,ISI'1 ando range of O,J--I.O)Jg. Atomic .bso,ptiOfl method. ha.. been widely ....d tod.t.rmin. chromium boc.use of 'heir ..lUilivi,y "'d .peed.

In ,he method to be des.:rlbed, airborn. particulot.. ore cohected bydrawinl the IU lhrough I mt••. Th. m1<l, 0' an ....1a1iqllOl, wilh coll«",dplrticulo'n, is diln'ed to p..pa.. 0 ,..t sample. P'eplflljon of tllis sampleis simple Ind lipid, The iq""O\lO "'idie sampl. is scrutinized by an .,omieIboorplion .""ctrophotome..r II the w,,<length 3S7.8nm and thechromium cont'nt is ""kullt.d by r.fminK ,h••bsorb....,. found '0 ,he,pP\'oprio.. calibll,ion curve. By the lIS< of Ilflphi'. fum""" iddi'ional..n,i'ivity m-tty be .dtie"'d btyond ,h., of ,h. u,UlI flame mod•. Th.duomium ....lues found are txp.....d in mic'OI,"m, pe' cubic m.l'" of .ir..mpled. Some PrlCliCil rktlils of 1<C1l"C}' ""d p..ci,ion ob',;nable win befound und~, ,be l<t1ion "Exp't$Oion of Ruul1S'· (9).

2. FlELDOf AI'PLICATION

Th. method is app!i",bl. to ,he m,",u..m.nt of the le..ls of .u.pendedparticul". chromium found in either itnbient or indumW "moophe,••.

'00

Bued upon lbe flt.me mod•. wabed 111.. mI.... and a nominal air sunp\<volume of 2.000 cubic mel .... chromium i> mel$urabl. to 0.015microgram. per cubic m.r ... If tbe Pmp\< i> tol<en on analyticil grad.ceUnlose, lh. minimum quanlity me..nrable is d.cr.ase<! 10 I painl which i>dependent upon lbe chromium conlml of W r.agents ""'d 10 diswl.... lheceUulose. Analylical Vad. ceUulose """lain. 1<.. than 0.25 micrOl'""u Crper .liquot do.c 36mm In diamel.r, As I.veh of chromium in urban ai, ...low and ,,;nce the poISibilily of conwninallon f,om chromlum-conUiningmeliis in lh. laboratory may be rawr hi&h ......1}' can must be lak.n toen.u.. thlt the chromium beinK m<alu..d ;,. actually d"" to the air Amp\<.

3. PRINCIPLE

A pr.pa,.d I<>t Ampl. conlainirll: w ;nol'lanic con'tituents in aqueo'"acidic solution is atomiz.d in • name Or heat.d Vlphil' lub<. TheIbsorption of lIa/l1 of charlOt.ri't;' ........I.nglh by th. Ilom, of lh••I.m.ntof int....t is used 10 m<2$ure the con""nlration of \hlt element.

4. REACT10NS

The mOlr importanl ..."ion, ..Ial. to the complel. dissolution of th.particu!". Ample in acid m.di. to form a homO£etloou. "It sunpk. AImicrogram quantities of mat.riaI may be involY«!, 10.... due to incompletesolurion, volatilily 0' .dlOrpllon mult be avoided. If • portion of theairbom. ch,omium 10 be m'l$ured is in the form ofCr,O" 10m' difficultymay be .ncounle"d in IOlubililinK.ill the chromium. Uling the lest "mplepo-'paution method ou,lmed in 7.3, only a tOlal of from 5.1Oj.rg of (I, 0,will be IOlubilized pel di••,,;on. Thi< rep....nu a mI>limum of 0.1;0. percubic met.... flgu" approltima"ly .... timn the "normal" value expectedfor the chromium con"nt of urban air.

5. REAGL'l/TS

5.1 Ail', ro"'I,..1£<1

In p....u.. cyllnde,. or onlin•.

5.2 Acttyknt, rompressm

In P"$.1o" cyllnd.....

53 Gli:ufiJrm

Commercially available matorial is .xhaulti....ly wa<!J.d prior 10 0.. ; in,,;uW3 by :l.54mm.

'"

5.4 C~IIu/c$e {illm

iUhless, acid w"'hed, .n.lylical grad•• in ,ill' 203 by 254.

55 Walti'

Dis,ill.d a' 1•.,ltwico from ~us orquom.

5.6 HydroflUOl'icadd

4~ Reason! pad•• in poIy.'hylene IXInuirte".

5.7 Nilriuxid

71%. R.ogon! g,o<I.

5.8 Siandmd JO/l;lionsof chromium

Dil.so1.. th. am"",,' of chromium ""It O<lui..l.m 10 II",m of chromium inWi"r and dilute '0 I lil~ wilh w.ltr. I1n1 of 'hi' ,tocl< ""Iullon ~on,.in,

1.000 mk'OIflm. of chromium. C,. Both tri..l.m ""d hexaval.nlchromium h... bun found '0 give .qual It,!"""" using tho .toml~

.bsorplion condition, ducrib<d in 10.8 md 10.9.

6. APPARATUS

6.1 Sp«lropho,olml.,. alomic abJOTfJlim

With m<1<f, re~ord.r Or digital readoul md monocluoma'o' wilhw...l<llglh dial r.ading 10 0.1 n'nomotr•.

6.2 l'ipmes, r/<l..Milillilre cap.dti«, "'0 d.li......

6.3 Vo/l;IlU'rric flask.BorooiliCllt< with ground glass stopp'r, 25m1 capocity.

6.4 Boul,.. polyelltyl.".

Scr<w cap, "I.ok free" fot.,o,. of I.st ""mpln, 3Om1 capacily.

65 &<zJ<m. I£fJo~

Criffin form, 100m1 capad'y.

""

6,6 Bta!<e". boro,llicat<

Gradu.t.d, Griffin ronn, with t.flon OOlled rim, 1SOml <iplCity.

6.7 HOI plttu

Electric, with l.mperatur. <ontrol, thermoolal. and ",ramie he.ting .urfa"'.

6,8 BUchner funnel

Polypropyl.n•. custom roade, with ,int.red hlse bottom and ,,,-cuumoonn.ction. 216 by 267 by S5mm.

6.9 Graph;l. jur""ce

On••ui1lbl. ;nmumenl il .....il.bl. <ommercially to th. M.",mll1n d<$ign

6.10 Str;pcMnrecordu

To di,play .nd reoord Ih' rupon.. fwm th. furnace.

6, II P~I1t•. auto""";';

Eppendorf d..ign, wilh cop.dti.. 10. to 100 mkrolitr...

7. SA.\1PLlNG AND SAMPLES

7.1 AirSampiing

Drow ail through lhe filwat • flow rote !lelw«n 1.13 and 1.60 cubkmetre. per minul' if high volume ...mpling il used. An 'pproprill. lim.period il 24 hou" wh.n &Jus fib,. fill'" are used. Th. resisl""'" 10 flowoff.red by the ",Uul"" mle" is much gre.l.r than for gil" lIId anapprt<i.bly .mall., 10111 v<>lum. will be llk.n wilh «l1ulo.. for • sim~",

..mpJing lim., C.lculat. and ",cord the 101.1 ",Ium. of.i, wnpled in cubicrneU<I, .. the product of m.an flow rol••nd time.

7.2 Preparalio" of the IttboralOT)' >I1mple

A> loon .. p""ibl. aft.. lh. sompJing hll been complet.d, the filter Ihouldbe carefully removed from tho filter he.d, pla"'d in on .n~lope wilhcompltte do-curnentalion and nan,milled to lhe Iabo"uoTY in the qulck..lrelitble way.

'0;

7.3 fupara/O;Jn of 1m wnpk

Cut .,ul lliqLlOt. f,om the exposed .urfoce of a fr1'~r uslrtl a cl,,,uw m~t:ol

punch. A .uiloble punch is one mode of a moww which will no, rele...

chromium dwino: the pWIchinl process, a cri'erion which mly bt<lctermin~d by Cl...blishim; ,he chromium conlent of filter blanks havinl nocontO<:1 with m~ ..1 during prtp""lioo. Th. cutUnl ~dgt of lh~ punch iscarefuUy wiped ,,·ith ten. tissue bt,w~n each use '0 prevent carry ove, ofcQfltamino,ion from 00...mpl~ '0 ono""'r. PI.". nne Or mort .uch diOC$ in• 'enon b..k~,- [oi'io .. the dissolu'ion of ,h. fill., mUm by ,he d'opwixaddition of lmi of hydrofluoric ocid (5,6), Genlly worm ,he COOtents of ,h.be.k.., .. low h..t, un'il the hydroflUoric Kid Is olmon completely~VlIporlle<l. AI ,hi. poin" add I to 2ml ofnitric acid (5.7) and. contin"" '0h.., I:'ntly untU a f~w drops of nilri" >old Ol. I.ft. Add o!>ou, IOm[ ofw..or, bring nearly '0 ,he boil and m,e, ,hrough a Whitman 41 fr1,er into aglu$ ben~, (6.6). Transfer '0 a 25ml ""lum.uie fluk (6,3). Rinse down thelen"" beaker with another IOmI quanti,y ofw.ter, ""orm >rid filter in'o the..me l>c.a.~,. T,"".f~r to the 25ml voIume'ric flu. and mn. up teSt sample'0 m..k at 25·C. ~h the cont~nlS of the ",lumCiric f1uk lhoroua:hly of'erodjustmen, '0 ,,>Iume, Tran.fer contenlS of ""Iurn.,ric f1uk topoIy~,hyl~n~ .to,ol:' boule (6.4). The l~n ..mpl. is 0r>W ,..dy fo' an:oly>i•.T1Ic .bo.... m"hod opp~~o to ,he dlBCS'ion of &lus fib'" filters, CeUulosefrIt~" con b~ diFned 0' eX'l1C,~d PSinl nilric acid,

8. PROCEDURE

8.1 Stif~lyprtatu'lonl

FoU""" norm:ol precautionl for the hondlinS of comprew:d lues. Obsoerve",""of",'urer. inmuch""" 011 I;voI;OJ ...d eXI;ngUMing nome. TEST GASSUPPLY SYSTEM FOR UAKS BEFORE liSE AND EACH TIME ACYLINDER OF FUEL IS REPU.CED.

8.2 T~'I Par/v".

8.2.1 Ten poniOll., f1am~

Inuoducc ,he I..,' portlO11 Into the f1ame by """tin"""" up;,";on, throughpo[y~lhylene tubin&. of 1JI W1mftUUmi portion of 'he \ClI ..mplo. A'pira ..dlstm.d ""ater in'o t1om~, bel""een ,he inrroduction of each ,~.t portion, 10

pte""m croS> c""..min..;on.

8.2.2 Te.. PO";oo" fufO'''''

M~uure and in.." in the fumatt, 1.., port;"'" of \010 100 mkIolltre. ofthe 1..1 ..mple usinB on ou,om"l< p;pel1~ (6.1\).

''''

8.3 C4/imation Cutw.8.3.1 Calibration cw,,". fbme

U.in, ~to d.li~r" pipe"", prtp." !:nown conoontmion. of chromium bydilution of .u.ndard tolution (S.8) "'ith filt.r b\lnl: ..,lution prtportd •• in(7.3) from unexF"""d filt.r to CO~r the "nB. of 1,0 to S.O mk'ovam. ofchromium per mi. 1",,.n in tbe .pectrophotom.t.r Ind llign, if ne""Mary,'he hollow cothode ..,uret for chromium, Set th. wl~l.ngth of themonochromllor ot 357.8nm. Usinl nitrous oxide.acetylene I1.lm•. aspi ..,.an unmeasured portion of each dllulO "and.rd chromium ..,Iulion for 10so<x>nd. (8.2.1), At the ..me time, ..pir". inlO tbe flame IlOlution offmerhlan!:. From lbe in"rumental ".pon... """in.d. prtpar•• calibrotioncu..... of .bsorb.nce again" cOr><:.ntration of chromium. in microgram. perml. S""h • "p",'emOli~ calibration CUr>O II p ....n in Figure 1, .... ith thecorr..ponding c"",e for chromium .""dud. in war., (Page Ill),

8.3.2 Calibration CUIVe•. futna«

By meln' of In lutomatic pipe". with polyethylene tip. place identicalmicrout" volumes of ,be dilute ."ndar<! chromium lOlu,ion. and. d;stille-dwOle, blank in lbe fumac., Menu" and ..cord tbe ....pome of nch leslporti"" following the pr.d.wmined m...uring cycle. Co",r th. 'ange 0.2to 1.0 nanogram chromium In ueps of 0.2 nanogram: 0.01 10 0.05microgr.m. po' mI fOf. 20 microHI... volume. Prep..e. calibrallon ourve of,"port... in Irbitrary units, again,t cono:nm.'ion of chromium inmi.crogrlm. per ml. Such. r.pment.li.... calibration ou"," is p ....n inFigure 2. Preparalion of st.nd.rd. in mter blank is nol n.usury for fum...worl< •• the mmix effeetl ol»erved do nol o«ur wi'h ,he fumlCt.

g.4 lXl~,mi1lilrlM

8.4.1 DetetminOlion, flam<

Set th. wlvelength of the monochrom.to, Il 357,8nm. Ob.. rv\nicondition. of 8.2.1 .nd 8.3.1, aspirate ." unm<....,.d ,..t portion of .Ichunkn""" te" ..mple intO ,he flame. Record the rnpOIll" for .""hunkn""'n. Aspi.. te dis,illed """ mto the n.me b.t..·..n ••ch unknown""t portion to p...... nt cross contamination, M...u,e the ohromium In all'he unknown 10" ..mples "'hich can be accommo,h'ed to Ih. w..... length357.8nm .nd the cor....ponding calib.. lion <u ......

8.4.2 Determination, furnace

M.a<ure in'o 'he furnac., by IUlomatio pi!",''", • simillf ,.1I portion of••ch un!:nown tel, ..mple, Follow the dryirli and heotin, progrlmmtlpr..;olt$ly ,,"blished. Record the r..pon.. fOf each test portion inarbitrary uni". Deri'" th••mOllnt of chromium p sent in th. , ..t ..... pleby ",f.rMi to the Ippropriat. calibration <u , such IS. for e~.mple.

figUlt Z(l'agc Ill).w,

8.S BIIlnk Tn"

85.1 Reagents

In pa..Uel with prepuatiOll of caUbraliOll CU1'\1'~. prfpne a reogent bllllk ofthe add. and di.tilled wo,er ""'d in the prepamion of ulil>ra,ion curve.ond 'e" ..mples. (hlllge or purify [tagent.... neceuary. if Mank. oreun.. ,i.f"",ory .

8,S.2 FUter blank.

In pa.1lI1I.l with Ih. pr.p.oration of cal'l>ralion curve. and ,e" ...mple••pr'J>lI' or..l re" pollion. from un..""",d m,er media .. d''''ril>ed in 7.3.Me..ur. chromium and expressl>lonk. in microy,om. of ch'omium per mL

9, EXPRESSION OF RESULTS

9.1 Blank.

The P'" m,e, blank ,a1 ... fOT any el.m.nt may v.ry CQnsideral>ly withthe l>atch. Thi. h.. been "..,y nOlieeable with mongan.... beryUium .ndchromium. For rhis ..ason. filter l>1."I<> ,hould be det.rmined regul.rly. Ilshould be noted. ho...."..,. rhol ,h. filler blonk ....1.... for Chromium "'ithino p""" batch of f~ren a.e extremely uniform. If, whe.e pos.sil>le. rut...from • known l>."h .", ....,d. de,.orion hmi" of rho method may belowered.u,reme core m"'t be t:lk.n '0 ioo!a,e ond .1Imin.,. chromium interferenonnormally present in thol.boratol)'. Pan of 'he filte' bl""k val". i. due tomllrix inte,ference. from .I.,n""" p'e<en, in larter arnnunl$ in rho filterwch .. Na. Ro. Si. Ca. In, K and AI.

9,2 frutrom.nta/ precision

This io defined os me .undlld deviation of 0 number of repllr:>.tede,.rmin.,ions and is up..wd in microgram, per m!. Typical predsion. fo,ren repeal determination. on "llldoni ...mpl.. are 2.00 ± 0.01 microgram.pe' rnl for ,he name mode, apinS! O.OS % 0.0008 micfogram. per ml for thenomeLns mod. U$ing 0 20pl ..mple,

9.3 Minimum~SUNb/e

9.3.1 Concentration in r.....mpl<

This is uken os twice me bl"'k d...iation. or instrument precision ....hkhe'~r is lo1'&e,. This i. 0.06 microgram. per mI in the case of chromium.U$ing ,he f10me mode and Vas fibre nlten. For the nomeleu mod. thebllllk deviation i. the det.rmining factor and this may vary for diff.,entfilter batchel. Minimum m...u,.ble may be a. high os OJ)4 mi<:Iogrun. pe,mI for glass fihre mren.

''''

9.3,2 Cone<ntralion in air

This i. based upon. <ample "clume of 2,000 cubic metreS and lwo aliquo'discs 36mm in diamet<r. The minimum measurable conctntralion is 0.015micrograms pe' cubic metre for lhe n.me mode and 0.010 microgr.m. peTcubic metre for the fbmeleu mooe. The.. valUl:s Of< I""'e' fo' cellulo..fillets as e~plained in Section 2,

9.4 Cakukiti<ms

The chromium content of the '''' solution is expre,..d in mkrogroms ofchromium pe, ml, X" The blank, X" in the same units, i> ,ubtracted fromX, to get the corrected concentt.tlon of chromium in the .." sample in lISpe, m!. Multiplication by the dilution factor, usually 25. gi"'. 'ht totalquon'ity of chromium in tht ,tst sample, in microg,.t"'.

Fo, high 'olume filte" of nominal si.. , 203 by 254mm:Total .~po..d filt., surf.« • 4.159 ~ lO'mm'AreoJ te" portion, 2 ~ 36mm discs • 2,036mm'Surfact mulliplicotion factor • 10,43Dilution factor • 25Volume of air lampled, "ubi< metro1 • VRespon.. , unknown ,est porlion • X,Respon.., total blank • X,Chromium conctnlration, in l1s/m' • T

T .(X,

10. NOTES ON PROCEDURE

X,)~20.43~25,

10.1 Linle is ~nown aboot actual coll«tion emeiencit. and in method. forthe anal)"i. of particul ..e m.tab, the.. dfidenci...ro usually ignored. Th.particle s;u of pmkulate ch,omium i' alm"'t all between 0.6 and 4.5mkron••cco,ding 10 Lee (I 2.2).

10,2 The effect of tempe"tur••nd pressure durins tho ..mpl,ng p<,jod h..been l1fgely di.regarded in ,he pnt. Since the.. flct015 mu" hi\-e someeffect on the measured air volume. it is recommended 'hat these C01T<cllon.be inlloduc<d routinely. The,. is inc....ing ogre.m.nt lhal if 'tandardcondition. of 'emperature and pre"ure are to be used to corr.Ot the final\'CIlume, th... cClfldition' mould be 25'C and 760mm Hg.

10,3 Although lhe m.,hod duoribed I. nomlnaUy b.,ed upon hish 'olume",mple, ,.ken fo' a 24-hou, "'mpling pl'riod. lh... i' no Ylliid ",..on whysample, may nol be 101:", for ollorler lime pe,jods,,, '10.... ' flow role" orboth. If hish volume sample, are liken on «lIulo.. , it i' particularlyIl>pr0l>riate to toke air 'aml>le ,olum.. of \,000 wbic metr.. o,lm, The

'"

lowe, p.rticulat. IWinS, '0 obtained, mmimiu. particulate f"l-off. Thiamllth more favourable blank r..u1'ln$ f,om 'he lISt of cellulose and theatt.ndant ~Tease in serui'ivity should be borne in mind when the """pIins

proctdute io b.in~ pllflned.

10.4 It ia cu"omary to ....._ that the decre..e in air flow flI. dutinll..mplina i. lin... Ind for usual purpOS<O of calculation, the mnn value ofinitial .nd final flow rate. i. taken. Thia i. not comet, althoush the 'rrorintroduced by ,hi. OVtnimplifi""tion io not ordinarily ><ficus.

10.5 For the pr.paration of ..e.1 te" portion•. the use of a Ularp circularmet" die ia to be prererred o"r the lISt of sassOts or,eetilinear template.of Ia'l!e perimeter. Arell,." portions prepared by th.se latt.r.re less likelyto be Id"'tical in size. A circular die. of limit.d diameter. machined fromsotid m...l, i. very ,igid "'d .re" a1iquo" can be ve,y easily ,eproducedwith accuracy. In the m.thod desctibed.• punch' made ofbr'" io uoed. Nochromium contamination has bHn found to , ..ult f,om its use.

10.6 In ,he repetitive and c",,><cuU,....... te" ponion. cut from anexposed high volume filt.r, the ...umpti"" is implicil that the .lem..n ofin","1 is uniformly d;,tribnted ocrOl.' the .,po..d .urf.ce of the filter.Thia ...umption is established a. fact,1l le..t in the case of lead (12.3, 12.4,12.5) and c.odmium (one ..«ption w.. noted in 12,5) measu,ed on highvolume mten. This uniform diatributi"" cannot be assumed in cenainMmembnne" type filtets d"" 10 inhe,.ntly high pressure d,op and faultygeometry of comme'cially ...ilable fllte' holdeN. In ,he cO$< of .uch filt.n.lreil a1iquonins cannol be used (I 2.6).

10.7 11 i. helpful, when it is possible, '0 h".....ral calib'atton ow....rolatina to different ..nsitivitie•. Thia minimize. the possibility that thecOII.,.ntrati"" of ,he meul, in the unknown t'''Slmple. will not nu.tch oneor .nother of the cu",",. Se. method for lead in this .. rie. where twoc.o~bration cu"e...e gi"en for the fllm••nd one fo, the furnac. (12,7).

10.8 Ope,ali-w cundilOJru, /IIlm<The optimum Operatilli condition. Ite .. gi,'.n,

W... lenl'lh • 357.8nmSpeetnJ band width • L4nmSou,ce • Holl<>w cathodeSou,ce current • A. ,.commendedOxidant • Nitrous oxideFuel • A.,.,ylen.Flame • Reducitll. rich "dS<nolti>ity • 0.026>1-ilml fo' 1% .b"''P'ion

ChanF "elylen. cy~nde' bofo," p,...u,. drops 10 SO psig.

''''

10.9 Grophitt !wn«t

••• 357.8nm

20 mkrolit""Afloo Of nitl'08Ondryin.c(IS..c.)OO°C)chorring (l Ssec, 230"C)Olomizins(IS..c, 1,400°)

The use of. deuterium I.mp b>ckground rompe",.lo, il recommend""

Th. eallbrolloo ""rve for tho name mode obty, Beer', Law up 10 8,0mic'''ilnrns of chlomium per m) of teol ••mple .. illunro'M by Filure I. Artprewntative curve for chromium, me..uted by tht I"phite furnace. ;,given in Figurt 2, which sho..... gr..tly Inc"'ued ",nsilivity over the nam•.FurnloCt ope,"ing condillo"':

W...lenlth5.ample si>:tPurpnU"Thermal com,""silion •

10,10 Most chromium toJu. 1ik<ly to be found in ombient air. will besolubl. if lhe dil""tion procedure in 8.3 is follow.d, Compl<t. "covery ofadd.d ,ri..len' (CrCI,' 6H,O) and he~...lenl (K,(rO.) chromium h..betn demon"ra,ed in OUr aOOrllory. Chromium compound, which m.y bedifficuh 10 disloh...... chromillm sesquioxide (Cr,O]). elementalchromium (Cr), cMomium I"",,ide (C,....), chromium nilride (CrN) Indchromium silicide (C,]Si,), The soIubililY of (,,0, h.. been dilcu...d inSection 4. Cr..... CrN, C,.SI, .nd .l.mental chromium Ire not likely to befound in .mbient air. El.menu) chlOmium I, not found in nllure II\dairborne chromium in ,he vicinily of electropl.ting plonts 0' prod""'... ofchromium >110)'1 will likely be in tbe oxide form. The nuorides ofcbromium, CrF, .nd (rF" hive melting poi>u, above 1,0000 and loss ofchromium during dig••tion of 'he gl... fibre filter with hydrofluoric aciddoes nol occur,

10.11 The f01lowiOfl is an outline of the method for wubinS g1a.. fibremte... prior to use.

At pre"'nt, the e~pedient used i' to .u.mp! to le..h outth. impuritiesby me.nl of boiling distilled wller. A ,pecial BiJchner funnel, rectangul"rother thin circuar. was conslructed of polypropylene by Bel Art Products,~Ulnnod, New J.rsey. This was de'iIs'ed to hold One bo~ of 8 x toc.lm'n A mlers. To Improve the >cO", of the hot dislilled wltet. 'PO"'''are placed in the pile al inlerv.l, of every to fille". The pile of filt.,. i'rovered wilh boilini water. allo",ed 10 Ite.p for 30 minu". and the ",ater i'withdrawn by '''''lion. This ploc.ss is reputed. The washed g1us fih.,. areallowed to .ir dry in. dusl·fre. localion.

10.12 I'r,th the u", of fumeless .tomic .blOrption. ",!uipped with.background corrector, it w"' shown lhu chromium i' p,.,en' in 'he .dddige't of gl:ass fibre flit." hiving no previnu. con,." with metlll. Two36mm discs ..... ,. shown 10 contain from 1.64 to 3.35 microyam. ofchromium of which 0.3 microgranu were derived from lbe re"lent. used 10dissolve tbe twO discs. The .ariability of th. chromium cootent of tbe gl....;jbre was \eu if fihets from the same batch ....re used.

""

II. SCHEMATIC REPRESENTATION OF PROCEDURE

11.1 Drawllboralorylirsampll.

11.2 CU11"'"te>l polli"" from ..posed 'U,fICl,

11.3 [)iges11","1 I ••, portioo,

! 1.4 Adju" digln to ...,]ume to ti..e 1O'..ample,

11.5 Mpilll. 10., porti"" uno nlme.

11.6 Or. odd 'e.' portion 10 fUlnae<, mlnured by micro/i' .. pipelte.

12. REFERENCES

! 2.1 Ch'omium. InoyS, compounds. Encyclopedia of Oc<:upationoJllelhh""d Sofely. Inleml1i""ol Labou, OffiCI. GeneVi. SwiUlrllnd.

122 I.ee, R. E.• Plnenon, R. K. II\d Wagman, J, I. En;;;'. Sci ""d TICh. 2.288.1968.

12,3 Dubois, l., Tlichman, T., Airth. J. M.llld Monkman. J. l. The M....Con,ent of Urbon Air. Joum41 A.P.CA. 16, 2, 77, 1966.

12,4 ZdrojeW$ki, A.. Quicl:lrt. N.. Dubois, l. and M""kmon. J, l. TheAccur.'e M"s"lemen, of I.e"" in Airborne Particulates. fn( J. Envir.Allal. Oem. 2, 63, 1971.

12,5 Zdroj......ki. A.. Quicken. N.. and Dubois, L The Accurl,eMI",u,"men, of Cadmium in Airborne P.oniclllal". 1nl, J. Em-ir-.A""i Citem. Sopt.rn,,", 1972.

12.6 Pillce. J. 0, Ind Meyer. J. H. Sampling and An")1.il CoU$idellt;on, inEnlOlling I.e..els of A'mosphlric I.e"", A,mos. En.iJ'Q"",e11l 5, l! I I.1911.

12.7 Monkrnlrt, J, l. ~,e,minllion of Airborne Particulate I.e"" byA'omic Absorption Spe<lroICOPY. see p.l.

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