Analisis instrumen 2.docx

FUNDAMENTALS OF POTENTOMETRIC MEASURMENT Potensiometry is Potensiometry is an extrem extremely ely versatile analytical metho that allo!s allo!s ra"i ra"i an an sim"le analyses#  The ex"erimen ex"erimental tal set$" %or "otentiomet "otentiometric ric meas$r meas$rement ement com"rises an inicator an re%erence electroe# The inicator electroe "rovies a "otential that e"ens on the com"osition o% analysis sol$tion# The tas& o% the re%er re%erence ence electroe is to s$""ly a "ot "otent ential ial !h !hich ich is as in ine"e e"en nent ent as "os "ossi' si'le le o% the an analy alysi siss sol sol$ti $tion# on# The meas$re "otential U is the s$m o% all inivi$al "otentials "ro$ce 'y inicator an re%erence electroe# Fi(# ) sho!s a schematic re"resentation o% the sit$ation $sin( the exam"le o% a "* (lass electroe !ith se"arate re%erence electroe# Inicator electroe +le%t, an re%erence electroe +ri(ht,#  The "otential meas$rem meas$rement ent is "ractically c$rr c$rrentless entless an is meas$r meas$re e $sin( voltmeter !ith a hi(h im"eance meas$rin( in"$t +"* meter,# U) - (alvanic "otential o% the mem'rane relative to the analysis sol$tion U. - (alvanic "otential o% the internal '$/er relative to the mem'rane U0 - 1alvanic "otential o% the internal re%erence electroe relative to the internal '$/er U2 - (alvanic "otential o% the external re%erence electroe U3 - li4$i 5$nction "otential at ia"hra(m +see li4$i 5$nction6 "a(e )0, Fi( )- Meas$rment set$" %or "otentiometric meas$rment  The inivi$al inivi$al "otential U.6U06an U.6U06an U2 are (iven 'y the electroe electroe assem'ly assem'ly an th$s constant %or a s"eci7c electroe "air# The li4$i 5$nction "otential at ia"hra(m U3 can 'e &e"t more or less constant an small thro$(h $se o% s$ita'le meas$res +see "a(e )0, so that the "otential meas$re 'et!een the t!o electroes e"ens only on the activity o% the analyte ion ai# This relationshi" is escri'e 'y the Nernst e4$ation U - "otential meas$re 'et!een inicator an re%erence electroe Uo - stanart "otential o% electroe assem'ly6 e"ens on its constr$ction R - (as constant +860)22) 9#:;)# 9#:;)# Mol;) , 2826 3> C#mol;), ai - activity o% analyte ion i UN - Nernst slo"e

.60?0 is the conversion %actor %or the nat$ral lo(arithm to 'ase ten#  The Nernst slo"e slo"e UN s"eci7es the the theoritical electroe electroe slo"e# slo"e# UN corres"ons corres"ons to the "otential char(e ca$se 'y the chan(e in ai to the "o!er o% ten# It e"ens on the conition o% the electroe assem'ly6 the tem"erat$re an the char(e < o% the analyte ion# It is 3=6)> m@ at .3 C %or $nivalent6 "ositivelly char(e ions +0; com"lexes#  The sol$tion %or the recorin( o% a cali'ration c$rve m$st 'e treate in exactly the same manner as the sam"les# The meas$re "otential U is "lotte as a %$nction o%  the lo(arithm o% the concentration +lo( c,# Instea o% the cali'ration6 stanar aition is o%ten em"loye# *ere6 an initial "otential meas$rement is "er%orme in the sam"le# Then a &no!n 4$antity o% the analyte ions is ae an the "otential remeas$re# From the "otential chan(e the ori(inal concentration o% the analyte ion in the sam"le can no! 'e calc$late# Ion selective electroes are also %re4$ently $se %or the inication o% titrations# In this case the ionic stren(th o% the analysis sol$tion is $nim"ortant an the cali'ration $nnecessary#  Ta'le . - Ion selective electroes

P* 1LASS ELECTRODES "* (lass electroes res"on to the hyro(en ions6 i#e# they are ion selective electroes %or *# The ion selective meas$rin( elemen is a (lass mem'rane o%  s"ecial com"osition# e%ore the electroe is reay %or meas$rment6 the (lass mem'rane m$st 'e soa&e in !ater# It %orms then a thin6 (el  li&e hyrate layer# I%  the (lass electroe is immerse in !ater at room tem"eret$re6 the s!ellin( o% the mem'rane is com"lete !ithin .2;28 h# The %ormation o% this hyrate (el layer is accelarate at hi(her tem"erat$res# In corrosive meia6 or(anic solvent an F; containin( sol$tions this hyrate (el layer can 'e ama(e# Fi( - 3 sho!s a "art o% a com'ine (lass electroe Several im"ortant conce"ts that constantly a""ear in conection !ith "* meas$rement !ill 'e ex"laine in !hat %ollo!sASJMMETRJ POTENTIAL6

Khen the (lass electroe is immerse in an analysis sol$tion that is ientical to the internal '$/er6 theoretically the meas$res "otential U sho$l 'e  Ta'le   The "rinsi"le o% the o$'le 5$nction electroe6 also calle electroe !ith salt 'ri(e6 can 'est 'e ill$strate 'y a i(ram + see Fi( =,  The 'ri(e electrolyte allo!s relatively %ee aa"tation to the anaysis sol$tion# It m$st sim"ly 'e com"ati'le !ith the internal electrolyte6 i#e # no reaction +e#(# "reci"itation m$st ta&e "lace# In the case o% non;a4$eos system6 'oth the internal an 'ri(e electrolyte sho$l 'e non;a4$eo$s# Th$s 6 no "hase 'o$naries a4$eo$s  non a4$eo$s arise at !hich salt that are sol$'le only in a4$eo$s meia can crystaline o$t# A s$ita'le internal electrolyte is c +LiCl, B sat# In etanol # For aitional exam"les6 see Ta'le = "a(e )>#

Fi( =# Re%erence electroe o% o$'le;5$nction constr$ction e#(# A(A(Cl re%erence !ith sleeve ia"hra(m For meas$rements at lo! tem"erat$res it m$st 'e note that the sol$'ility o% salts ecreases !ith ecreasin( tem"erat$re# Salts o% a concentrate electrolyte sol$tions o% lo!er concentration6 e#( c+:Cl,B)63 molI instea o% c+:cL,; sat or 0molI Since every electroe assem'ly com"rises an inicator an a re%erence electroe6 the "otential o% the re%erence system contri'$tes to the meas$re "otential U# I% the re%erence system is chan(e6 the ne! electroe assem'ly "otential U ne! can 'e calc$late as %ollo!sUne! B UoG  U re%# Ol Ure%# Ne!  Ta'le 8 shoes several re%erences system an their "otentials relative to the stanar hyro(en electroe# In "ractice6 the most %re4$ently $se re%erence system are he silver chlorie an calomel systems# In the case o% ion selective electroes the re%erence system s"eci7e 'y the man$%act$rer sho$l 'e $se so that the asymmetry "otential remains small an the meas$res val$es are in the normal meas$rment ran(e# Silver chlorie re%erence system have $niversal a""lica'ility# It m$st 'e note that the s"arin(ly sol$'le A(Cl %orms chloro com"lexes in chlorie containin( meia an hence 'ecomes more sol$'le# In meas$rements in chlorie %ree meia the

i"hra(m can 'e 'loc&e 'y crystallise A(Cl# This "ro'lem can 'e cimc$mverten 'y !or&in( !ith a chlorie containin( 'ri(e electrolyte# Calomel re%erence systems can 'e $se $" to tem"erat$res o% ?C# At hi(her tem"erat$res calomel is"ro"ornations#  Ta'le 8#  The %ollo!in( Ta'le sho!s several exam"les o% re%erence system %or i/erent a""lications#6 an "ossi'le 'ri(e electrolyte sol$tions are mentione i% o$'le  5$nction electroes are $se#  Ta'le = In a aition to the a'ove;mentione re%erence systems6 any electroe that s$""lies a "otential ine"enent o% the com"osition o% the analysis sol$tion can 'e $se as a re%erence# In "reci"itation titrations !ith A(6 %or exam"le6 the "* (lass electroe occasionally is $se as re%erence electroe# A re4$irement is that the "* val$e o%  the analysis sol$tion remains constant # O!in( to its hi(h resistance +resistance o% a %e! h$nre Mohm,6 the re%erence (lass electroe m$st 'e attache to yhe hi(h im"eance meas$rin( in"$t o% the meas$rin( instr$ment6i#e# !here the inicator electroe is normally attache6 !hereas the inicator electroe it sel% +e#(# A( electroe, is connecte to the lo! im"eance in"$t # This ex"erimental set$" has the avanta(e o% not neein( a ia"hra(m+no contaminate or clo((e 5$nction6 no re7llin( o% the re%erence electrolyte, Sometimes car'on electroes are $se as re%erence electroes# No ia"hra(m is neee here either# I% yo$ !ish to chech !hether s$ch $n ex"erimental arran(ement !itho$t ia"hra(m is "ossi'le6 the electroe $ner test can 'e $se as one "art o% the electroe co$"le an "revio$s re%erence electroe as the other "art # Then a titration is "er%orme # I%  the res$ltin( titration c$rve IS A STRAI1*T LINE 6 the ne! re%erence electroe s$""lies a "otential that is ine"enent o% the analyte ion6 i#e# the electroe can 'e $se as a re%erence6

AD@ANTA1ES AND PRO@EN ENEFITS OF POLARO1RAP*J AND @OLTAMMETRJ  The statement o% most %$namental conse4$ence at this "oint is that these techni4$es are not o/ere as a $niversal "anacea %or all analytical "ro'lems# No sin(le analytical techni4$es is a'sol$te an in this res"ect it is as !ell to 'e a!are o% the isavantan(es as !ell as the avantan(es# In essence 6 the @A (ro$"h o%  techni4$e is a com"liment to the other analytical instr$mentations in the ro$tine la'oratory# This is "artic$larly mar&e !ith res"ect to AAS# This statement is 'ein( 4$ali7e 'y the very s$'stantial increase in the $se an a""lication o% the @A instr$mentation in the in$strial sector#

Some the ma5or 'ene7ts are o$tline 'elo! )# Polaro(hra"y an voltammetry are ca"a'le to the analysis o% many i/erent ty"es o% materials as !ell as the coonstit$ent "art o% these materials# The techni4$e is not limite "$rely to the analysis o% metals# Many or(anics an anionic mateials may 'e analyse6 an this o%ten in the same matrix# Or(anic analysis may constit$te ma5or or minor com"onent etermination6 as !ell as e(raation "ro$ct either in the "rocess stream or as a %$nction activity6 an this as a res$lt o% the more esta'lishe techi4$e r$nnin( o$t o% stream at the trace an $ltra trace level# M$ch o% the a""lication !or& is there%ore evote to the estimation o% the trace metals in vario$s matrices# The "rinci"al area !ill 'e o$tline %$rther on# .# P$lse techni4$es an avance electronic evices as !ell as ne! chemical methoolo(ies have res$lte in reasona'ly tro$'le  %ree analysis o!n to the ""' level +%or metals,# The very lo! etections limits are there%ore one o%  "rimary "ossitive "oints 0# Polaro(ra"hy an @oltammetry are 4$alitative as !ell as 4$antitative techni4$es6 This means that in certain e7ne matrices6 si(nal at s"eci7e "otentials are inicative o% certain s"ecies in sol$tion6 an the si(nal hei(ht o'taine at that "otential can 'e irectly relate to the concentration o% this s"ecies in the same sam"le reaction# 2# In (eneral6 one may s$((est that there are %e!er sam"le "re"aration ste"s !ith Polaro(r"hyvoltammetry than !ith com"atitive techi4$es 3# Sim$ltaneo$s analysis are "ossi'le !ith these techni4$es # It is "ossi'le %or $" to six si(nals +realistically, to 'e enco$ntere in one "olaro(ra"hic or voltammetric scan# ># For trace analysis 6 voltammetric techni4$es o/er the $ni4$e %eat$re that elemental "reconcentration is "er%orme irectly %rom the sam"le itsel% at the electroe s$r%ace# This eliminates m$ch o% the c$stomary solvent extraction etc# Enco$ntere !ith other trace techni4$es# # ELEme't that are "ro'lematical !ith Aas can 'e etermine in some case !ith (reater relia'ility# 8# Initial instr$mental set;$" is extremely 4$ic&# Learnin( to $se the instr$mentation is easy =# This techni4$e re"resent a really cost e/ective alternative  com"liment to the ro$tine la'oratorys existin( e4$i"ment ran(e# )?#In%ormation re(arin( the s"ecies "resent in the sol$tion can 'e o'taine in certain cases Perha"s the 'est oc$mente exam"les are those Cr+III,6 Cr+@I, an A$+I,6 A$+II,#

FUNDAMENTAL DARI PEN1U:URAN POTENTOMETRIC Potensiometri aalah metoe analisis yan( san(at e&si'el yan( mem$n(&in&an analisis yan( ce"at an seerhana# Set$" yan( e&s"erimental $nt$& "en($&$ran "otensiometri teriri ari ini&ator an ele&troa re%erensi# Ele&troa ini&ator mem'eri&an "otensi yan( e"ens "aa &om"osisi sol$si analisis# T$(as ele&troa re%erensi aalah $nt$& memaso& "otensi yan( secara ine"enen m$n(&in ari sol$si analisis# Potensial U i$&$r aalah  5$mlah ari sem$a "otensi inivi$ yan( ihasil&an oleh ini&ator an ele&troa re%erensi# 1am'ar# ) men$n5$&&an re"resentasi s&emati& sit$asi en(an men(($na&an contoh ari &aca "* ele&troa en(an ele&troa re%erensi ter"isah# Ini&ator ele&troa +&iri, an ele&troa re%erensi +&anan,# Pen($&$ran "otensial aalah c$rrentless "ra&tis an i$&$r en(an men(($na&an voltmeter en(an men($&$r mas$&an im"eansi tin((i +"* meter,# U)"otensi (alvani mem'ran relati% terhaa" sol$si analisis U.(alvani& "otensi '$/er internal relati% terhaa" mem'ran U0- 1alvanic "otensi ac$an internal ele&troa relati% terhaa" '$/er internal U2"otensi (alvani re%erensi e&sternal ele&troa U3- cair "ersim"an(an "otensial "aa ia%ra(ma +lihat "ersim"an(an cair6 halaman )0, 1am'ar )"en($&$ran set$" $nt$& "en($&$ran "otensiometri U. "otensi6 U06 an U2 i'eri&an oleh ma5elis ele&troa an en(an emi&ian &onstan $nt$& se"asan( ele&troa tertent$# Potensi "ersim"an(an cair "aa U3 ia%ra(ma a"at isim"an &$ran( le'ih &onstan an &ecil melal$i "en(($naan tina&an;tina&an yan( ses$ai +lihat halaman )0, sehin((a "otensi yan( i$&$r antara $a ele&troa ter(ant$n( hanya "aa a&tivitas ion ai analit# *$'$n(an ini i(am'ar&an en(an "ersamaan NernstU"otensial ter$&$r antara ini&ator an re%erensi ele&troa Uo- "otensi stanart "era&itan ele&troa6 ter(ant$n( "aa &onstr$&si R&onstanta (as +860)22) 9#:;) Mol;)#, 2826 3> C#mol;),

aia&tivitas ion analit i PNernst leren( .0?0 aalah %a&tor &onversi $nt$& lo(aritma alami $nt$& se"$l$h asar# leren( P Nernst menent$&an &emirin(an ele&troa teoritis# P ses$ai en(an m$atan "otensial ise'a'&an oleh "er$'ahan ai "aa &e&$atan se"$l$h# *al ini ter(ant$n( "aa &onisi "era&itan ele&troa6 s$h$ an m$atan < ion analit# *al ini 3=6)> m@ "aa .3  C selama $nivalen6 ion "ositivelly i'e'an&an +< B ),# 1am'ar# . men$n5$&&an "otensi ra&itan ele&troa yan( 'er'ea se'a(ai %$n(si ari "a B;lo( i .3 C an ) Ta'el a%tar Nernst &emirin(an "aa tem"erat$r yan( 'er'ea $nt$& < B )# Dari"aa $a ele&troa yan( ter"isah ; ele&troa ini&ator an ele&troa re%erensi ele&troa;(a'$n(an yan( serin( i($na&an# Ini aalah ele&troa i mana ini&ator an ele&troa re%erensi i(a'$n(&an alam t$'$h yan( sama# ele&troa (a'$n(an terse'$t le'ih m$ah $nt$& menan(ani ari $a ele&troa yan( ter"isah# 1am'ar# 0 men$n5$&&an "em'an($nan &aca (a'$n(an ele&troa "*# Se'$ah ele&troa re%erensi ter"isah6 'a(aimana"$n6 aalah ian5$r&an alam &as$s i mana e&si'ilitas le'ih i'$t$h&an alam hal sistem re%erensi 9i&a sol$si analisis men(an$n( ion yan( tia& &om"ati'el en(an sistem re%erensi# Se'$ah sistem re%erensi yan( 'er'ea &em$ian i"ilih6 m$n(&in en(an ele&trolit  5em'atan6 lihat halaman )3  9i&a sam"el mencemari ia%ra(ma 'erat an re%erensi ele&troa sehin((a "erl$ iservis serin( Dalam meia non;air ata$ meia &on$&tivitas renah imana ele&troa re%erensi &h$s$s isarin( har$s i($na&an# .# SELE:TIF ION Ele&troa .#) F$namental an i&htisar Ele&troa Ion sele&ti% memili&i elemen sensor yan( a"at menete&si ion tertent$ alam cam"$ran ion se'a(ai sele&ti% m$n(&in# Elemen sensor 'eri&$t ini serin( i($na&an alam "ra&te&:aca mem'ran $nt$& * 6 Na  :ristal mem'ran $nt$& F;6 Cl;6 r;6 I;6 CN;6 SCN;6 S.;6 A( 6 C$. 6 C. 6 P' Polimer mem'ran $nt$& : 6 Ca. 6 NO0;6 F2; mem'ran Ion selctive memili&i &onstr$&si yan( sama en(an ele&troa &aca "*G Paa lar$tan ion mem'ran antarm$&a selecive analisis "otensi i&em'an(&an yan( 'er(ant$n( "aa a&tivitas ion analit alam lar$tan sam"el# Re%erensi cair a"at i($na&an se'a(ai "en((anti ari re%erensi yan( soli# Ini aalah &as$s $nt$& ele&troe F;sele&ti%6 $nt$& sem$a ele&troa mem'ran "olimer an ele&troa &aca# 1as sensin( ele&troa $nt$& N*06 CO.6 ll alam ele&troa &aca "rinsi" "* yan( irenam alam lar$tan# Sol$si internal an sol$si analisis i"isah&an oleh s$at$ mem'ran "ermea'el (as# 1as yan( menye'ar melal$i mem'ran men($'ah nilai "* lar$tan internal an en(an emi&ian mem$n(&in&an "en($&$ran ari concertration (as# Persamaan Nernst mem'eri&an es&ri"si yan( te"at ari ia h$'$n(an antara

"otensial ter$&$r an a&tivitas ion analit hanya alam 'e'era"a &as$s# Dalam 'anya& &as$s selain ion ion $tama6 yan( ise'$t men((an(($ i ion inter%erent6  5$(a 'er&ontri'$si terhaa" "otensi# Pen(ar$h ion ini men((an(($ "aa "otensi "era&itan ele&troe a"at i(am'ar&an en(an "ersamaan Ni&ols&y# Ini aalah se'$ah "ersamaan Nernst i"erl$as yan( men(am'il sele&tivitas ele&troa ion sele&ti% &e re&enin( The ma(nit$te ari :i5 'eraa alam &isaran )?;) #### )?;3 $nt$& electroes#For ion yan( "alin( sele&ti% ieal ele&troa :i5 har$s ele&troa6 Sele&tivitas men5ai B ?6 ma&a ia hanya a&an meres"on "aa ion analit# Ele&troa &aca "* aalah yan( "alin( &oe7sien sele&tivitas :# Al&aline * 6 Na  aalah a"li&asi# )?;)0 +c%# Al&aline &esalahan6 halaman >,# 9i&a6 misalnya6 sam"el memili&i a&tivitas natri$m "aa tan((al ) mol I ah  B )?;). mol I +"* B )., ini mem'eri&an "* B; lo( +)?;). )#)?;)., B ))6=> alam &ata lain6 5i&a &esim"$lan iam'il ari "otensi yan( i$&$r tentan( a&tivitas * 6 &esalahan hanya )? ter5ai- a +* , B )#)#)?;). mol a&$ '$&an )6)?;).# Se'a(ai "er'anin(an cara6 = sam"ai )) sean(&an om'a +*  ion, a"at terleta& i antara )? om'a miliar +)?;)0, hitam +Na  ion,  Ta'el . a%tar yan( 'e'era"a ele&troa ion sele&ti% 'ersama en(an rentan( "en($&$ran an ion mere&a men((an(($# ion Men((an(($ 'ah!a rac$n ele&troa an &arenanya har$s a'sen iceta& alam !a5ah te'al alam Ta'el# Ion yan( tia& menim'$l&an inter%erensi sam"ai &onsentrasi mere&a mele'ihi ion analit a&an itam"il&an alam tana &$r$n( Ta'el# Men$r$t "ersamaan Nicols&y6 se'$ah "en($&$ran "otensial mem'eri&an in%ormasi men(enai a&tivitas ion analit alam lar$tan# Um$mnya6 'a(aimana"$n6 it$ aalah &onsentrasi yan( menari&# The ai :e(iatan ini 'er&aitan en(an ci &onsentrasi en(an "ersamaan 'eri&$tAi B yi#ci  Ji &e(iatan &oe7sien molar# Ini aalah %$n(si ari &e&$atan ion total sol$si an &arenanya '$&an &$antitas m$ah ia&ses# Unt$& san(at encer yi sol$si aalah sama en(an )6 i#e# a&tivitas ion analit sama en(an &onsentrasi analis ia&ses melal$i "en($&$ran "otensial seerhana6 te&ni& analisis &h$s$s telah i&em'an(&an yan( mem'$at "en(etah$an yan( te"at ari a&tivitas &oe7sien yan( tia& "erl$G :e&$atan ioni& ari sol$si analisis i5a(a &onstan en(an "enam'ahan s$at$ lar$tan ele&trolit inert# Sol$si ini memili&i &e&$atan ion 5a$h le'ih tin((i ari"aa sam"el# Serin(&ali en(an se"erti nilai "* lar$tan i5a(a &onstan "aa !a&t$ yan( sama an "en(ar$h ion men((an(($ ihilan(&an# Sol$si ini ise'$t  TISAS +Total Ionic Stren(th Penyes$aian $/er,# 9ai6 misalnya6 alam meas$rementISA en(an &om"osisi 'eri&$t i($na&anNaCl $nt$& men5a(a &e&$atan ion &onstan '$/er Asetat6 P* B 36 $nt$& mene&an &e"e&aan terhaa" O*;  Trans asam )6.;iaminocyclohexanetetreecetic B CDTA- &om"le&s yan( men((an(($ Al0 6 misalnya6 yan( mem'ent$& sta'il AlF>0;&om"le&s# Sol$si $nt$& mere&am &$rva &ali'rasi har$s i"erla&$&an "ersis en(an cara yan( sama se'a(ai sam"el# Potensial U i$&$r i"lot se'a(ai %$n(si lo(aritma ari &onsentrasi +lo( c,#

Alih;alih &ali'rasi6 "enam'ahan stanar serin( i($na&an# Di sini6 se'$ah "en($&$ran "otensial a!al ila&$&an alam sam"el# :em$ian i&etah$i &$antitas ion analit yan( itam'ah&an an i$&$r &em'ali "otensial# Dari "otensi "er$'ahan &onsentrasi ion asli ari analit alam sam"el se&aran( a"at ihit$n(# ele&troa sele&ti% ion 5$(a serin( i($na&an $nt$& ini&asi titrasi# Dalam hal ini &e&$atan ioni& ari sol$si analisis tia& "entin( an &ali'rasi yan( tia& "erl$#  Ta'el .ele&troa sele&ti% Ion P* :ACA Ele&troa ele&troa &aca "* menan((a"i ion hiro(en6 yait$ mere&a ele&troa sele&ti% ion * # Para elemen ion sele&ti% "en($&$ran aalah mem'ran se(elas &om"osisi &h$s$s# Se'el$m ele&troa sia" $nt$& "en($&$ran6 mem'ran &aca har$s irenam alam air# Mem'ent$& lal$6 ti"is (el ; la"isan hirat se"erti# 9i&a ele&troa &aca irenam alam air "aa s$h$ &amar6 "em'en(&a&an mem'ran selesai alam !a&t$ .2;28  5am Pem'ent$&an la"isan ini (el hirat ini accelarate "aa s$h$ yan( le'ih tin((i# Dalam meia &orosi%6 "elar$t or(ani& an F;sol$si ini 'erisi la"isan (el terhirasi 'isa r$sa&# 1am'ar- 3 men$n5$&&an 'a(ian ari &aca (a'$n(an ele&troa e'era"a &onse" "entin( yan( selal$ m$nc$l seh$'$(an en(an "en($&$ran "* a&an i5elas&an alam a"a 'eri&$tAsimetri POTENSIAL6 :eti&a ele&troa &aca irenam alam lar$tan analisis yan( ienti& en(an '$/er internal6 secara teoritis lan(&ah;lan(&ah yan( "otensial U har$s nol6 men(anai&an 'ah!a "era&itan ele&troa simetris6 yait$ ele&troa e&sternal an internal re%erensi inentical# Penyim"an(an 'e'era"a m@ yan( item$&an ise'$t "otensi asimetri# Lihat 5$(a 1am'ar # a# Asimetri e"ents "otensi "em'an($nan "era&itan ele&troa# $/er internal 'iasanya memili&i nilai "* G sehin((a "aa "* B 6 teoritis ?m@ sho$ls i$&$r6 yait$ sel nol aalah "aa "* B # AL:ALI ERROR Dalam lar$tan al&ali &$at &esalahan "en($&$ran a"at m$nc$l &arena contri'$tionto "otensi ari al&aine +lihat "ersamaan Ni&ols&y6 halaman 2, *al ini mem'$at mem'aca P* &e renah 6 :esalahan 'asa ter(ant$n( "aa nilai "* an &onsentrasi ion 'asa ini# Tays "* (lassessho! hanya exremly erorrs al&ali &ecil# P* cali'rasi :onisi "era&itan ele&troa "* ter(ant$n( "aa $&t$asi selama !a&t$# Ter(ant$n( "aa a&$rasi t$nt$tan it$6 &ali'rasi "* har$s ila&$&an secara 'er&ala6 misalnya se&ali sehari# Dalam &ali'rasi "* 'aris characeristic saat ele&troa alam 'ent$& "otensi asimetri an leren( Nernst aalah it$m"an(&an "aa (aris &ara&teristi& "* meter# Penera"an asimetri "otensial- +iteta"&an se'a(ai UAS ata$ Oha, Pertama merenam ele&troa "era&itan i '$/er en(an "* B  !iyh "otensiometer VUASV Penera"an leren( Nernst+Serin( itent$&an se'a(ai &emirin(an relati%- &emirin(an rel B P se'enarnya

nominal P6 &emirin(an rel misalnya B ?6=8 ata$ =8 , Cel$"&an ele&troa "era&itan i '$/%er &e$a +"* B  ,# Pilih nilai "* '$/er &e$a ini seemi&ian r$"a sehin((a i !ilayah sam"el yan( a&an i$&$r# Set nilai "* '$/er en(an &emirin(an "otensiometer# Den(an mi&ro"rosesor i&enali&an "* meter $r$tan ari sol$si '$/er tia& material &arena (aris &ali'rasi ihit$n( en(an 'ant$an ari ata "erco'aan# Lar$tan '$/er "* i&enal i($na&an $nt$& &ali'rasi "*6 Di sini har$s icatat 'ah!a nilai "* sol$si 'i/er ter(ant$n( "aa tem"erat$r6 lihat Ta'el 0# Unt$& "en($&$ran a&$rat s$h$ &ali'rasi har$s sama en(an s$h$ analisis# 9i&a "en($&$ran har$s ila&$&an i 'a!ah &onisi s$h$ $&t$asi "arah6 titi& "ersim"an(an isoterm ma5elis ele&troa har$s iat$r "aa instr$men "en($&$ran# *al ini im$n(&in&an en(an "* meter &elas tin((i6 nilai yan( ses$ai har$s itent$&an oleh "en(($na $nt$& setia" assem'lym ele&troa Nam$n6  Ta'el 0&eter(ant$n(an s$h$ nilai "* '$/er Metrohm Pera!atan an "emeliharaan ele&troa &aca "* Penyim"anan 1a'$n(an ele&troa &aca- Dalam ele&trolit re%erensi6 c +:Cl, B 0mol Saya A(Cl sistem re%ence lar$t se'a(ai &om"le&s Cholo le'ih 'ai& alam lar$tan yan( men(an$n( &loria ari alam air6 9i&a ele&troa i&om'inasi&an isim"an i Air6 A(Cl a"at memic$ alam ia%ra(ma Di"isah&an &aca ele&troaalam air ini Mem'ersih&an ia"har(m yan( Setelah "en($&$ran i meia en(an &onsentrasi &loria renah +ena"an A(Cl, i ia%ra(ma ia%ra(ma 'er!arna (ela",- tem"at ele&troa malam i conc# N*06 'ilas en(an air an ele&trolit re%erensi "er"an5an(# Setelah "en($&$ran i s$l%ia;'erisi meia +A(.S alam ia%ra(ma ia%ra(ma 'er!arna (ela",- Tem"at&an ele&troa alam lar$tan se(ar isia"&an6 tio$rea sei&it asam # Lal$ 'ilas en(an air an mem"er'ar$i ele&trolit re%erensi# Den(an &ontaminan or(ani&- Tem"at ele&troa $nt$& a""# 3 menit alam asam chromos$l"h$ric i 8?C6 &em$ian 'ilas an mem"er'ahar$i ele&trolit re%erensi  9i&a lan(&ah i atas tia& mem'ant$- hati;hati 7le &e ia%ra(ma en(an 7le &$&$ 'erlian# The elecrolyte o$to!in( har$s terlihat se'a(ai cincin (ela"# Pera!atan mem'ran &acaG Setelah "en($&$ran alam meia '$&an air- ele&troa renam alam air antara "en($&$ran# Setelah "en($&$ran "rotein 'erisi meia- merenam ele&troa selama 'e'era"a  5am alam lar$tan "e"sin alam asam &loria +"e"sin 3 i c +*Cl, B ?6) mol I,6 &em$ian renam secara menyel$r$h# Re(enerasi mem'ran &aca- &aca mem'ran merenam 'ai& selama ) menit6 alam lar$tan )? ari hyro(en$orie amoni$m +N*2*F., ata$ ari 'e'era"a eti& alam 2? *F# Setelah 'ilas etsa $nt$& a""# )? s alam lar$tan *Cl +*.O6 *Cl conc B )-), electoe ilas en(an air an mem$n(&in&an $nt$& 'eriri selama .2 5am alam lar$tan "enyim"anan# Masalah en(an ele&troa &aca Ta'el 'eri&$t 'erisi a%tar &er$sa&an yan( "alin( serin( 

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0# Ele&troa reo&s Dalam "en($&$ran ele&troa reo&s men(alami "ert$&aran ele&tron en(an sistem reo&s yan( i$&$r an &arenanya men(as$msi&an "ottential yan( ses$ai en(an yhe "otensial ele&tro&imia sistem# Se"erti "ert$&aran elecroe 'isa i'atasi hanya en(an sistem reo&s reversi'el# Potensi reo&s i$&$r '$&an mer$"a&an $&$ran lan(s$n( ari a&tivitas ion# Se'ali&nya6 it$ aalah $&$ran ari "osisi &esetim'an(an ari "asan(an reo&s con5$(ate an i5elas&an oleh "ersamaan PetersLo( U B U?  P sa"i  a merah Dimana6 Uo an P aalah stanar "otensial "asan(an reo&s an leren( Nernst an masin(;masin( AOQ an merah ses$ai en(an &e(iatan 'ent$& tero&siasi an men($ran(i ari "asan(an reo&s# Paa rea&si reo&s i mana ion hiro(en 'er"artisi"asi alam rea&si reo&s "otensial 5$(a ter(ant$n( "aa nilai "*6 misalnya MnO2; 8*   3e; Mn.   2*.O Persamaan Peters ter&ait aalahLo( U B Uo  P se'$ah MnO2; a Mn.;; 8 "* P Den(an &emirin(an Nernst Un B )3#3=#)> m@ B ))680 m@ i 03 era5at Sem$a ele&troa reo&s i($na&an alam "ra&ti& aalah &on$&tor ele&troni&6 misalnya alam 'ent$& lo(am m$lia se"erti Pt ata$ A$6 ata$ ele&troa carvon# Nam$n6 ele&troa ini tia& se"en$hnya ac$h ta& ac$h terhaa" "en(ar$h ion# 9ai6 misalnya6 ele&troa A$ 5$(a res"ons $nt$& ion siania ata$ &loria +siano sta'il ata$ &om"le&s &loro en(an A$ , ele&troa Reo&s serin( mem"erlihat&an "erila&$ yan( ter(ant$n( "aa se5arah mere&a# Mere&a cener$n( $nt$& mem'ent$& la"isan o&sia thn yan( men(arah &e "asivasi ari ele&troa# Ele&troa a"at ire(enerasi en(an lar$tan 4$inhyrone6 lihat halaman )) stanar Reo&s yan( se memeri&sa Pt m$rni an ele&troa A$# Nilai "otensial an "* $nt$& mem'ent$& Methrom reo&s stanar i'eri&an alam Ta'el 3# Mere&a 'erla&$ $nt$& Methrohm i&om'inasi&an en(an c ra&itan ele&troa A( A(Cl +:Cl, B 0 mol I se'a(ai sistem re%erensi# 

*ar$s "otensi reo&s ise'$t ele&troa hiro(en stanar6 "otensi i$&$r a"at i&onversi men$r$t "ersamaanUa'sol$te B U i$&$r  sistem re%erensi U Potensi ari sistem re%erensi yan( i($na&an +lihat Ta'el 86 halaman )>, itam'ah&an &e alam "en($&$ran termas$& tananya# Pen(alaman memain&an "eranan 'esar alam "emilihan ele&troa reo&s yan( te"at# *al ini ham"ir tia& m$n(&in $nt$& meleta&&an at$ran "enera"an $m$m# Mes&i"$n emi&ian6 alam a"a 'eri&$t $"aya a&an ila&$&an $nt$& mem'eri&an 'e'era"a ti"s $nt$& "emilihan ele&troa reo&sele&troa Pt aalah yan( "alin( serin( i($na&an ele&troa A$ a"at $n(($l Pt ele&troa alam 'e'era"a &as$s &h$s$s6 misalnya

$nt$& ia  Ta'el  Para "rinsi"nya ari ele&troa "ersim"an(an (ana6 5$(a ise'$t ele&troa en(an 'ri(e (aram6 ter'ai& a"at i(am'ar&an oleh i(ram +lihat 1am'ar =, Ele&trolit 5em'atan mem$n(&in&an relati% aa"tasi 'iaya $nt$& sol$si analisis yan( i($na&an# Ini hanya har$s &om"ati'el en(an ele&trolit internal6 yait$# aa rea&si +misalnya c$rah h$5an har$s ter5ai# Dalam &as$s sistem non;a4$eos6 'ai& ele&trolit internal an 5em'atan har$s non;air# Den(an emi&ian6 tia& aa 'atas %asa air  '$&an air m$nc$l i mana (aram yan( lar$t hanya alam meia air a"at Crystaline &el$ar# Se'$ah ele&trolit internal coco& c +LiCl, B $$&# Dalam etanol# Unt$& contoh tam'ahan6 lihat Ta'el = halaman )># 1am'ar =# Re%erensi ele&troa &onstr$&si o$'le;5$nction misalnya A(  A(Cl re%erensi en(an ia%ra(ma len(an Unt$& "en($&$ran "aa tem"erat$r renah har$s icatat 'ah!a &elar$tan (aram men$r$n en(an "en$r$nan s$h$# 1aram ari sol$si ele&trolit "e&at &onsentrasi le'ih renah6 misalnya c +:Cl, B )63 mol  a&$ '$&an c +:CL, ; $$& ata$ 0mol  I :arena setia" "era&itan ele&troa teriri ari ini&ator an ele&troa re%erensi6 "otensi sistem r$5$&an &ontri'$si &e"aa "otensi U# i$&$r 9i&a sistem re%erensi i$'ah6 "era&itan ele&troa 'ar$ "otensial U 'ar$ a"at ihit$n( se'a(ai 'eri&$tUne! B UoG   U re%# Ol;Ure%# ar$  Ta'el 8 'e'era"a se"at$ re%erensi sistem an "otensi mere&a relati% terhaa" ele&troa hiro(en stanar# Dalam "ra&te&nya6 sistem r$5$&an yan( "alin( serin( i($na&an aalah ia &loria "era& an sistem &alomel# Dalam &as$s ele&troa ion sele&ti% sistem r$5$&an yan( iteta"&an oleh "a'ri&an har$s i($na&an sehin((a "otensi asimetri teta" &ecil an nilai;nilai tina&an alam rentan( "en($&$ran normal# Pera& &loria sistem re%erensi itera"&an secara $niversal# *ar$s icatat 'ah!a hemat A(Cl lar$t alam 'ent$& &om"le&s &loro &loria;'erisi meia an &arenanya men5ai le'ih lar$t# Dalam "en($&$ran i meia &loria 'e'as i"hra(m terse'$t a"at i'lo&ir oleh A(Cl men(&ristal# Masalah ini 'isa cimc$mverten en(an 'e&er5a en(an &loria yan( men(an$n( ele&trolit 'ri(e# sistem re%erensi &alomel a"at i($na&an sam"ai en(an s$h$ ?C# Paa s$h$ yan( le'ih tin((i is"ro"ornations &alomel#  Ta'el 8#  Ta'el 'eri&$t men$n5$&&an 'e'era"a contoh sistem re%erensi $nt$& a"li&asi yan( 'er'ea6 an# :em$n(&inan sol$si ele&trolit 5em'atan ise'$t&an 5i&a ele&troa "ersim"an(an (ana i($na&an#  Ta'el = Di sam"in( sistem re%erensi terse'$t i atas6 setia" ele&troa yan( memaso& ine"enen "otensi &om"osisi ari sol$si analisis a"at i($na&an se'a(ai re%erensi# Dalam titrasi "en(ena"an en(an A( 6 misalnya6 (elas ele&troa "*

&aan(;&aan( i($na&an se'a(ai re%erensi ele&troa# "ersyaratan aalah 'ah!a nilai "* lar$tan analisis teta" &onstan# :arena resistensi yan( tin((i +resistansi 'e'era"a rat$s Mohm,6 ele&troa re%erensi &aca har$s ter"asan( &e yhe im"eansi tin((i men($&$r in"$t ari alat $&$r6 yait$ imana ele&troa ini&ator 'iasanya ter"asan(6 sean(&an ini&ator ele&troa it$ seniri +misalnya ele&troa A(, ih$'$n(&an &e in"$t im"eansi renah# Set$" e&s"erimen ini memili&i &e$n(($lan tia& mem'$t$h&an s$at$ ia%ra(ma +tia& ter&ontaminasi ata$ ters$m'at "ersim"an(an6 tia& men(isi ari ele&trolit re%erensi, :aan(;&aan( ele&troa &ar'on i($na&an se'a(ai ele&troa re%erensi# ia%ra(ma tia& i"erl$&an i sini 'ai&#  9i&a Ana in(in chech a"a&ah s$at$ "er5an5ian e&s"erimental se"erti $n tan"a ia%ra(ma aalah m$n(&in6 ele&troa yan( i$5i a"at i($na&an se'a(ai salah sat$ 'a(ian ari "asan(an ele&troa an re%erensi se'el$mnya ele&troa se'a(ai 'a(ian lain# Lal$ titrasi yan( ila&$&an# 9i&a &$rva titrasi yan( ihasil&an WVADALA* LINE LURUS6 re%erensi 'ar$ ele&troa "erseiaan "otensi yan( ine"enen ari ion analit6 yait$ ele&troa a"at i($na&an se'a(ai re%erensi6 :EUNTUN1AN DAN MANFAAT TERU:TI DARI Polaro(ra7 DAN voltametri Pernyataan &onse&$ensi yan( "alin( menasar "aa saat ini aalah 'ah!a te&ni& ini tia& ita!ar&an se'a(ai o'at m$5ara' $niversal $nt$& sem$a masalah analitis#  Tia& aa te&ni& analisis t$n((al aalah m$tla& an alam hal ini aalah 5$(a $nt$& saar a&an isavantan(es serta avantan(es# Intinya6 (ro$"h @A te&ni& mer$"a&an "$5ian &e"aa instr$mentasi analitis lainnya i la'oratori$m r$tin# *al ini itanai seh$'$n(an en(an AAS# Pernyataan ini sean( memen$hi syarat oleh "enin(&atan yan( san(at s$'stansial alam "en(($naan an "enera"an instr$mentasi @A i se&tor in$stri# e'era"a man%aat $tama aalah se'a(ai 'eri&$t)#Polaro(hra"y an voltametri mam"$ $nt$& analisis ari 'er'a(ai 5enis 'ahan serta 'a(ian coonstit$ent ari 'ahan terse'$t# Te&ni& ini m$rni tia& ter'atas "aa analisis lo(am# anya& or(ani& yan( mateials anioni& a"at ianalisis6 an ini serin( alam matri&s yan( sama# Analisis Or(ani& m$n(&in mer$"a&an &om"onen $tama "enent$an ata$ &ecil6 an 5$(a se'a(ai "ro$& e(raasi 'ai& alam aliran "roses ata$ se'a(ai a&tivitas %$n(si6 an ini se'a(ai a&i'at ari techi4$e le'ih ma"an V&eha'isan ar$sV "aa 5e5a& 5e5a& an $ltra tin(&at# anya& &arya a"li&asi &arena it$ i&h$s$s&an $nt$& estimasi ari lo(am 5e5a& i 'er'a(ai matri&s# Area $tama a&an i$rai&an le'ih lan5$t# .#P$lse te&ni& an "eran(&at ele&troni& yan( can((ih serta metoolo(i &imia 'ar$ telah men(a&i'at&an c$&$" masalah ; analisa 'e'as sam"ai &e tin(&at ""' +$nt$& lo(am,# The 'atas ete&si yan( san(at renah &arena it$ salah sat$ "oin "ositi%  "rimer 0#Polaro(ra"hy an voltametri yan( &$alitati% ma$"$n te&ni& &$antitati%6 ini 'erarti 'ah!a alam matri&s tertent$ yan( telah itent$&an6 sinyal "aa "otensi tertent$ aalah ini&asi ari s"esies tertent$ alam lar$tan6 an tin((i sinyal i"eroleh "aa "otensial yan( a"at lan(s$n( 'erh$'$n(an en(an &onsentrasi ini s"esies alam rea&si sam"el yan( sama# 2#In $m$m6 &ita 'isa men$n5$&&an 'ah!a aa sei&it lan(&ah;lan(&ah "ersia"an

sam"el en(an Polaro(r"hy  voltametri i'anin(&an en(an techi4$es &om"etiti% analisis 3#Sim$ltaneo$s im$n(&in&an en(an te&ni& ini# *al ini im$n(&in&an $nt$& sam"ai en(an enam sinyal +realistis, yan( a&an ihaa"i alam sat$ "olaro(ra7 ata$ voltametri scan# >#Unt$& 5e5a& analisis6 te&ni& voltametri mena!ar&an 7t$r $ni& yan( "re&onsentrasi $ns$r ila&$&an lan(s$n( ari sam"el it$ seniri "aa "erm$&aan ele&troa# *al ini men(hilan(&an 'anya& aat ll e&stra&si "elar$t Dihaa"i en(an te&ni& 5e5a& lainnya# #ELEme't yan( 'ermasalah en(an Aas a"at itent$&an alam 'e'era"a &as$s en(an &eanalan yan( le'ih 'esar# 8#Initial instr$mental set;$" yan( san(at ce"at# ela5ar $nt$& men(($na&an instr$men yan( m$ah te&ni& =#This mer$"a&an 'enar;'enar 'iaya alternati% yan( e%e&ti%  "$5ian $nt$& 'er'a(ai "eralatan yan( aa la'oratori$m r$tin it$# )?#In%ormation men(enai 5enis yan( aa alam lar$tan a"at i"eroleh alam &as$s tertent$ M$n(&in contoh io&$mentasi&an ter'ai& aalah mere&a Cr +III,6 Cr +@I, an A$ +I,6 A$ +II,#