Chem126 Lab – Instrumental Analysis
EXPERIMENT 5 Chemical Interferences in Atomic Absorption Spectrophotometric Measurements Vanessa Ola !" #aon$on an$ %en M" Mene& Department of Chemistry, Chemistry, College of Arts and Sciences, ni!ersity of the "hilippines – #isayas, $iag%ao Iloilo
A'STRACT Calcium content in prepared samples containing other species such as K, P, La, EDTA and Al was determined using AAS or Atomic Absorption Spectroscopy. our schemes were adapted in the e!periment" #$% absorbance o& Ca standards determined using air'acetylene (ame) #*% absorbance o& Ca + K stan standa darrds dete deterrmine mined d us usin ing g air' air'ac acet etyl ylen ene e (am (ame) #% #% absorbance o& Ca standards determined using -*'acetylene (ame) and #/% absorbance o& Ca + K standards determined using -*'acetylene (ame. Addition o& K and P contributes to the chemical inter&erence due to the incomplete dissociation o& com compou pounds nds. This his can be minim inimi0 i0ed ed by using sing a high high temperature (ame ame -*'acetylene (ame instead ead o& air'acetylene and by adding a releasing agent, La. Addition o& Al can cause cause anothe anotherr type type o& chemic chemical al inter& inter&er erenc ence e using using inte inter& r&er eren ence ce due to e1ec e1ectts o& ion ioni0at i0atio ion n. This his can be minimi0ed by using a low temperature (ame, air' acetylene and by adding a protecti2e agent such as EDTA.
INTRO#(CTION Atomic Atom ic spectr spectros oscop copy y is a series series o& di1er di1erent ent 3ualit 3ualitati ati2e 2e analys analyses es regarding the concentration o& a speci4c substance in an analyte, with each analysis applied based on the characteristics o& the substance.$ As with any atomic spectroscopic method, the identity and concentration o& a subs su bsta tanc nce e in a samp sample le solu soluti tion on coul could d be dete deterrmine mined d by e!ci e!citi ting ng the the molecules o& the solution using a source, such as heat or strong light. This e!citation produces neutral atoms in the gas phase, which emit a speci4c wa2ele wa2elengt ngth h and and intens intensity ity o& light light that that gets gets captur captured ed and analy0 analy0ed ed by $ detectors. These processes are considered 2ery success&ul in a wide array Page ) o& )5
Chem126 Lab – Instrumental Analysis o& applications in data analysis, with most processes already built into special automated
machines.$5 This e!periment uses the (ame atomic igure *. A schematic diagram &or the process o& atomic absorption spectroscopy.$
igure $. arian SpectrAA >> atomic absortion spectrometer. The user inter&ace is located top right, the light source and detector at the lower right, the nebuli0er and aspirator #clear tube% at the lower le&t, and the co2ered burner at the top le&t which
spectroscopy, where an analyte is ta6en up by an atomic absorption spectrometer to be e!cited using di1erent mi!tures o& acetylene (ame. The mi!tures depend on the includes an e!haust chimney .$ substance being analy0ed, as not all substances can be atomi0ed with the same type o& (ame. Each substance has a certain temperature needed to atomi0e them in gas phase, as well as a ma!imum speed &or the (ame to attain. 7n the case o& this e!periment using metallic substances, too high a temperature can ioni0e the metal while too low will ha2e less metal atoms e!cited) both decrease sensiti2ity.8 As only air 9 acetylene and nitrous o!ide 9 acetylene torches were used in this e!periment, the ma!imum (ame speed o& air 9 acetylene is $:5 cm s;$ and ma!imum temperature at *55 >
Chem126 Lab – Instrumental Analysis aerosol will easily 2apori0e the analyte, and a hotter (ame will easily 2apori0e stable compounds) both reduce inter&erences at this step.8 A&ter e!citation, the released energy is con2erted as light, which tra2els through a monochromator. The monochromator is a de2ice that helps select one certain wa2elength to reach the detector. @owe2er, the light coming &rom the neutral atomic gas is so narrow that it causes gaps in the monochromator slit which greatly de2iates the amount o& light obtained by the detector) this can be sol2ed by acti2ating a hollow 9 cathode ray tube that deli2ers radiation patterns similar to the substance being analy0ed.$ A&ter the light reaches the detector, it is then analy0ed. A simpli4ed process is shown as igure *. Due to di1erent substances ha2ing di1erent properties, the metals &eatured in this e!periment ha2e to be dissol2ed in certain concentrations and ha2e speci4c (ames to atomi0e. Aluminum was present in the &orm o& aluminum chloride he!ahydrate. eing a more easily dissol2able &orm o& aluminum, it was added directly to the standard solution. The optimal wa2elength &or aluminum is 8:.$ nanometers while using a nitrous o!ide 9 acetylene (ame) due to it being partially ioni0ed in the (ame, a small amount o& potassium chloride was added to the solution as a suppressor.* Calcium was used as a standard &or all the other solutions in this e!periment. sed in the &orm o& calcium carbonate, a small amount o& nitric acid was added be&ore dilution o& water to help it dissol2e completely. The optimal wa2elength &or aluminum is /**.? nanometers, while using a nitrous o!ide 9 acetylene (ame) in air 9 acetylene (ames the inter&erences o& calcium can be reduced by adding lanthanum, while in nitrous 9 o!ide acetylene (ames potassium chloride is added to suppress ioni0ation. Potassium was present as potassium chloride. The optimal wa2elength is at ?::.> nanometers with an air 9 acetylene (ame) this same (ame helps eliminate inter&erences in the sample./ Lanthanum was present as lanthanum chloride in the e!periment. The optimal wa2elength is at //$.? nanometers, with a nitrous o!ide 9 acetylene (ame) the inter&erences caused by partial ioni0ation were suppressed by the potassium present in the solution.> Phosphorus was present in the e!periment as sodium phosphate. The optimal wa2elength is at *$.: nanometers at a nitrous o!ide 9 acetylene (ame) due to being an uncommon substance determined in AAS and ha2ing a lac6 o& sensiti2ity in the process only a &ew studies contain inter&erence in&ormation about phosphorus.: The standard solutions are prepared to obtain a common constant between all other solutions. This standard was based around calcium. 7& the concentration o& the solution is plotted against the absorption o& each Page + o& )5
Chem126 Lab – Instrumental Analysis standard, the slope o& the resulting line e3uals the common constant or molar absorpti2ity F. This is used in the eer 9 LambertGs Law, which relates absorbance #A% to the molar absorpti2ity, path length o& light #b%, and concentration o& the sample solution #c%"8 A = εbc
#
%$ The obtained absorbance &rom the di1erent solutions is then con2erted to transmittance"8 − A
T =10
#*%
7n 2ice 2ersa, absorbance could also e3ual the logarithmic &unction o& transmittance. To decrease inter&erences in the samples the same suggestions that were mentioned earlier were used as well as adHusting se2eral aspects o& the (ame and samples to obtain the ma!imum sensiti2ity in high precision.8 MET,O#O-O./ Two series o& standard solutions were prepared. The 4rst series contained only calcium carbonate. i2e $55 milliliter 2olumetric (as6s were used to contain 5, $, *, , and > ppm o& calcium carbonate, respecti2ely. These (as6s were labeled &rom $A to >A in the manner o& increasing calcium concentration, and then diluted to mar6 with distilled water. The second series was prepared similar to the 4rst, howe2er an added appro!imate o& 5.5=$ grams o& potassium chloride was added to each (as6. The second series (as6s were labeled &rom $ to >, same in order as the 4rst series. A set o& sample solutions were prepared in $55 mL 2olumetric (as6s, with di1erent mi!tures o& substances &or each. A stoc6 solution o& *>5 mL calcium was prepared by dissol2ing *./8?: grams calcium chloride into *>5 mL water in a *>5 mL (as6. This stoc6 calcium solution was used &or each o& the &ollowing sample solutions" The 4rst (as6, labeled $S, and all other (as6s were each added with mL o& stoc6 calcium solution. The second (as6, labeled *S, was added 5.55> grams o& sodium phosphate. The third (as6, labeled S was added 5.55> grams o& sodium phosphate, and 5.=$= grams o& potassium chloride. The &ourth (as6, labeled /S, was added with 5.55> grams o& sodium phosphate, 5.=$= grams o& potassium chloride, and 5.55$? grams o& lanthanum chloride. The 4&th (as6, labeled >S, was added with 5.585= grams o& aluminum chloride he!ahydrate. The si!th (as6, labeled :S, was added with 5.585= grams o& aluminum chloride he!ahydrate and *.$/: grams o& EDTA.
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Chem126 Lab – Instrumental Analysis The spectral inter&erence o& the each solution was recorded using atomic absorption spectroscopy by air'acetylene and -*'acetylene (ames. Each set o& solutions were analy0ed by air'acetylene and -*5'acetylene (ames, with the standards being tested 4rst be&ore the samples. RES(-TS
AN# #ISC(SSION
Two sets o& standards were prepared in the e!periment" one is composed o& calcium in di1erent concentrations and the other one is composed o& calcium and potassium in di1erent concentrations. The absorbances o& each set o& standards were analy0ed in the AAS using two (ames" air'acetylene and -*' Acetylene (ame. This resulted to &our schemes" Scheme $ used air'acetylene (ame to analy0e the calcium standards) scheme * used the same (ame to analy0e the calcium plus potassium standards) scheme used -*'acetylene (ame to analy0e the calcium standards) and, scheme / used the same (ame to analy0e the calcium plus potassium standards. These &our schemes will result to 42e calibration cur2es used to obtain the concentration o& calcium in the prepared samples. This 2ariation o& conditions is done to identi&y the e1ect o& the added inter&erence in the prepared samples and also the e1ect o& the type o& (ame used in the analyses. Table $ summari0es the result o& absorbances obtained &rom each schemes. -otice that in scheme $ at the concentration o& $ mg'L, there was no recorded absorbance. This is because the absorbance read was negati2e and there&ore would be erroneous. The data was discarded instead. igure shows the calibration cur2es obtained &rom each schemes. Linearity o& the calibration cur2es was not satis&actory. The calibration cur2e is somehow cur2ed up or has an Iupward cur2atureJ. hile this may be due to the inaccurate preparation o& the standards, it is a &act that it is rare &or atomic absorption calibration cur2es to show ideality #i.e. linear plot%. The Iupward cur2atureJ in the calibration cur2es generated is usually obser2ed on the standards o& small concentration range.$$ Table * shows the absorbances recorded in each samples prepared. As shown, there are si! samples with the same concentration o& calcium, each o& which contains di1erent inter&erences. Table shows the concentration o& calcium o& the samples obtained &rom each scheme. 7t can be obser2ed the (uctuation o& the 2alues &or the concentration o& calcium in each sample despite the &act that they are o& the same
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Chem126 Lab – Instrumental Analysis concentration o& calcium when prepared. This shows how much an addition o& inter&erence a1ects the analysis done in AAS. 7n the 4rst sample which theoretically contains only mg'L calcium, the obtained concentrations &rom the &our calibration cur2es were much lesser than the theoretical 2alue #Table %. This indicates that there are indeed errors in the preparation o& the calibration cur2es #i.e. preparation o& standards%. All the other samples contain the same amount o& calcium as that o& the 4rst sample. @owe2er, the remaining samples contains other components such as P, K, La, Al, and EDTA. 7nter&erences in atomic absorption &all into si! categories" chemical inter&erences, ioni0ation inter&erences, matri! inter&erences, emission inter&erences, spectral inter&erences, and bac6ground absorption. The most common inter&erences are chemical inter&erences. A chemical inter&erence emerges when the sample being analy0ed contains a thermally stable compound with the analyte that is not totally decomposed by the energy o& the (ame and thus, the number o& atoms in the (ame capable o& absorbing light is reduced. $* There are to general &orms o& chemical inter&erences" ioni0ation and incomplete dissociation o& compounds.$ The e1ect o& phosphorous and potassium in calcium, as in the second and third sample, is an e!ample o& a chemical inter&erence due to incomplete dissociation o& compounds. These inter&erents &orm compounds which are not completely dissociated at the temperature o& the (ame and hence pre2ent the &ormation o& neutral ground state atoms.$ To o2ercome this inter&erence, a higher temperature (ame can be used, as in in scheme * which uses -*'Acetylene (ame, or La can be added as a releasing agent, as in sample /. A releasing agent, which can be re&erred also as a competing cation, reacts with the inter&erent releasing the analyte.$* The presence o& Al, as in samples >, are another e!ample o& a chemical inter&erence. This time, the inter&erence is due to ioni0ation. To o2ercome this in&erence, a lower temperature (ame such as air' acetylene (ame must be used, as in in scheme $, because high temperature (ames such as nitrous -*'acetylene may cause appreciable ioni0ation o& the analyte element. The al6ali and al6aline;earth metals such as Al are more susceptible to ioni0ation. To control this inter&erence, a suitable cation with an ioni0ation potential lower than that o& the analyte is added. A protecti2e agent such as EDTA can also be added to reduce this e1ect, as in sample :. A protecti2e agent is a ligand reacts with the analyte &orming a relati2ely 2olatile comple!.
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Chem126 Lab – Instrumental Analysis 7t can be obser2ed that the results o& the e!periment did not coincide with the theory o& the e!periment. This can be accounted with the inaccurate preparation o& the standards and also o& the samples. Table ). Absorbance eadings o& the Standards Air'Acetylene lame -*'Acetylene lame Scheme $ Scheme * Scheme Scheme / Ca Standard 5 mg'L 5.555> 5.555* $ mg'L 5.55*5 ; * mg'L 5.5??= 5.5:$ mg'L 5.5=*/ 5.5::$ > mg'L 5.$8: 5.$?=5 Ca Standard + K 5 mg'L $ mg'L * mg'L mg'L > mg'L
5.555 5.55:= 5.5??8 5.5=*/ 5.$=$=
Table *" Absorbance readings o& the samples Sample Air' Acetylene lame mg'L Ca 5.5=*/ mg'L Ca + P 5.5/$ mg'L Ca +P + K 5.5>$8 mg'L Ca + P + K + La 5.5>5= mg'L Ca + Al 5.5*8* mg'L Ca + Al + EDTA 5.555*
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5.55*8 5.55?5 5.5=8? 5.585= 5.$:?
-*' Acetylene lame 5.5::$ 5.5$/5 5.5>$: 5.5:8 5.5/>* 5.5*55
Chem126 Lab – Instrumental Analysis
Calibration Cur3e4 Scheme * 5.*555 &#!% M 5.5/! ; 5.5$ LN M 5.8>
5.$>55
Absorbance
5.$555 5.5>55 5.5555 5
$
*
,
/
>
:
Concentration of Ca 5 % Stan$ar$s 6m7-8
Calibration Cur3e4 Scheme ) 5.*>55 5.*555 &#!% M 5.5/! ; 5.5* LN M 5.8/
5.$>55
Absorbance 5.$555 5.5>55 5.5555 5
$
*
,
/
>
:
Concentration of Ca Stan$ar$s 6m7-8
#a%
#b%
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Chem126 Lab – Instrumental Analysis
Calibration Cur3e4 Scheme 0 5.$>55 &#!% M 5.5,! + 5 LN M 5.8
5.$555
Absorbance 5.5>55
5.5555 5
$
*
,
/
>
:
Concentration of Ca 5 % Stan$ar$s 6m7-8
Calibration Cur3e4 Scheme + $*.5555 $5.5555 =.5555
Absorbance
:.5555 /.5555 *.5555 5.5555 5 &#!% $ M* , / > : LN M 5
Concentration of Ca Stan$ar$s 6m7-8
#c%
#d% Page : o& )5
Chem126 Lab – Instrumental Analysis ;iure +" Calibration cur2es generated &rom each scheme" #a% plot o& the absorbance obtained using air'acetylene (ame against the concentration o& Ca standards, scheme $) #b% plot o& the absorbance obtained using air'acetylene (ame against the concentration o& Ca + K standards, scheme *) #c% plot o& the absorbance obtained using -*'acetylene (ame against the concentration o& Ca standards, scheme ) #/% plot o& the absorbance obtained using -*'acetylene (ame against the concentration o& Ca + K standards, scheme /.
Table +" Concentration o& Ca in the samples in mg'L Air' Acetylene lame -*' Acetylene lame Sample Scheme $ Scheme * Scheme Scheme / mg'L Ca *./:5 *.>*:: *.*55/ *.*//= mg'L Ca + P $.// $./58= 5.:=/= 5./*$ mg'L Ca +P + K $.?5: $.:8?= $.??=: $.??= mg'L Ca + P + K + La $.:?85 $.::?8 *.*8> *.>:: mg'L Ca + Al $.$/5 $.5=58 $.>8*/ $.>$/5 mg'L Ca + Al + EDTA 5./*> 5.*8*8 5.=>8/ 5.:*8
CONC-(SION Atomic Absorption Spectroscopy #AAS% is a techni3ue &or measuring 3uantities o& chemical elements present in a sample by measuring the absorbed radiation by the chemical element o& interest. The sample is e!cited by radiation ma6ing its atoms absorb ultra2iolet or 2isible light and ma6e transitions to higher energy le2els. 7n this e!periment, (ame atomic spectroscopy is used to e!cite the analyte using di1erent mi!tures o& acetylene (ame. The analyte in this e!periment is calcium. Calcium content o& : samples containing inter&erences and other components were determined. To determine the calcium content in the samples, two sets o& calcium standards #Ca standards and Ca+K standards% were prepared to create calibration cur2es. The absorbances o& the standards were determined using air'acetylene and -*'acetylene (ames as indicated in the &our schemes &ollowed in the e!periment. our calibration cur2es were obtained in the e!periment. E1ects o& inter&erence in the determination o& calcium in the sample were e!amined. Potassium and phosphorus caused a chemical inter&erence due to incomplete dissociation o& compounds. This inter&erence can be aided by using a higher temperature (ame #-*'acetylene (ame instead o& air'acetylene% and also by adding Lanthanum which is a releasing agent. Aluminum can cause another type Page )< o& )5
Chem126 Lab – Instrumental Analysis o& chemical inter&erence due to e1ects o& ioni0ation. To aid this, a lower temperature (ame such as air' acetylene (ame must be used because high temperature (ames such as nitrous -*'acetylene may cause appreciable ioni0ation o& the analyte element and also by adding a protecti2e agent such as EDTA. These theories were not re(ected in the results o& the analysis because o& the inaccurate preparation o& standards and samples.
-ITERAT(RE CITE# $. I7ntroductionJ. Determination of Calcium by Atomic Spectroscopy . Chem /" Ouantitati2e Analysis Laboratory, Colorado State ni2ersity. arch */, *5$:. p. $ 9 *. *. IStandard Conditions" Al #Aluminum%J. &lame Atomic Absorption Spectrometry' Analytical $ethods. Agilent Technologies, Australia. $th ed. -o2ember *5$>. p. $:. . IStandard Conditions" Ca #Calcium%J. &lame Atomic Absorption Spectrometry' Analytical $ethods. Agilent Technologies, Australia. $th ed. -o2ember *5$>. p. */. /. IStandard Conditions" K #Potassium%J. &lame Atomic Absorption Spectrometry' Analytical $ethods. Agilent Technologies, Australia. $th ed. -o2ember *5$>. p. /*. >. IStandard Conditions" La #Lanthanum%J. &lame Atomic Absorption Spectrometry' Analytical $ethods. Agilent Technologies, Australia. $th ed. -o2ember *5$>. p. /. :. IStandard Conditions" P #Phosphorus%J. &lame Atomic Absorption Spectrometry' Analytical $ethods. Agilent Technologies, Australia. $th ed. -o2ember *5$>. p. >/. ?. Amos, . D. illis, Q. . IChoice o& lameJ. Spectrochimica Acta' se of high – temperature pre – mi(ed )ames in atomic absorption spectroscopy . Pergamon Press Ltd., -orthern 7reland. 2ol. **. $8::. p. $*?. =. arti0ano, Q. Iaterials ProceduresJ. Chemical Interferences in Atomic Absorption Spectrophotometric $easurements. ni2ersity o& the Philippines isayas 9 iagao Campus, Philippines. arch *5$:. p. $. Page )) o& )5
Chem126 Lab – Instrumental Analysis 8. el2ille, Q. ITheoryJ. Atomic Absorption Spectroscopy of $etal Alloys. Chemistry $5>" 7nstrumental ethods in Analytical Chemistry, er6eley College o& Chemistry, ni2ersity o& Cali&ornia, Cali&ornia. arch , *5$/. p. *. $5. alsh, A. I7ntroductionJ. Spectrochimica Acta' *he application of atomic absorption spectra to chemical analysis. Chemical Physics Section, Di2ision o& 7ndustrial Chemistry, Commonwealth Scienti4c and 7ndustrial esearch rgani0ation, elbourne, Australia. Pergamon Press Ltd., London. 2ol. ?. $8>>. pp. $5= 9 $??. $$. @ar2ey, D. odern Analytical Chemistry. nited State o& America" The cRraw;@ill Companies, 7nc.) *555 cited *5$: ebruary. A2ailable &rom" http"''elibrary.bsu.a0' $*. S6oog D. A., est D. ., @oller . Q., Crouch S. . *5$/. undamentals o& Analytical Chemistry -inth Edition. Canada" -elson Education, Ltd. $5*:p.
APPEN#ICES I+ *ables Table 0. Statistical Data &or the Schemes $, *, and / Statistical Parameter sr sm sb sc r
Scheme $
Scheme *
Scheme
Scheme /
5.5/55/5>/ ;5.5$:=:=8$8 *.*=!$5;* >.8!$5; $.::!$5;* :.**!$5;$ 5.88
5.5:?8=:/8 ;5.5$5>??5 $.8: !$5;5* >.$5 !$5;5 $./ !$5;5* :./* !$5;5$
5.5:/8$=8 ;5.5$8$::** *.*= !$5;5* >.8* !$5;5 $.:> !$5;5* :.8$ !$5;5$
5.5*=: 5.55$8 *.$> !$5;5* >.:5 !$5;5 $.>: !$5;5* =./ !$5;5$
5.8/>/
5.8*:?
5.=8:8
II+ Sample Calculations Least Suare $ethod Page )* o& )5
Chem126 Lab – Instrumental Analysis Uor Scheme $ Let ! be the concentration o& the Ca standards and y be the absorbance =
>
=*
>*
=>
5
5.555>
5
5.555555* >
5
$
5.55*5
$
5.55555/
5.55*
*
5.5??=
/
5.5=*/
8
>
5.$8:
*>
sum
$$
5.>85
8
a3e
*.*
5.5?$=
?.=
S xx = Σ x
2
( Σx )
−
2
m=
S xy S xx
=
=39−
n
S yy = Σ y −
S xy = Σxy −
2
( Σy )
( 11) 5
=14.8
=0.05138054 −
( ΣxΣy ) n
0.5965 14.8
( )
2
5.5>$=5 >/ 5.5$5*?: $5
2
2
n
5.55:5>*= / 5.55:?=8? : 5.5=>: 8
( 0.3590 ) 5
2
= 0.02560434
[ ( 11) ( 0.3590 ) ] = 0.5965 =1.3863 − 2
5
=0.040304054
Σy Σx = 0.3590 −( 0.02560434 ) b= −m 5 n n
( )=− 11 5
0.01686892
Determination o& calcium in sample where y M 5.5=*/ equationof line : y =0.040304054 x − 0.01686892
Page )+ o& )5
5.$>>: 5.*/?* 5.8=$>
$.=: 5.*??*:
6>)? m=)b8* 5.5555$: ?8 5.555/>8/ :> 5.555$8?? 5: 5.555/:=/ 5.555$>: 8$
5.55$>:* 8? 5.555$* >8
Chem126 Lab – Instrumental Analysis x =
0.0824
+ 0.01686892
0.040304054
=2.4630 mg / L
ncertainty o& easurement 0.040304054
(¿¿ 2 )( 14.8) =2.28 × 10− 5 −2 S yy −m S xx =¿ √ ¿ N − 2 s r= √ ¿
0.02560434
−
2
2
√
sr ( 2.28 × 10−2 )2 =¿ =5.93 × 10−3 14.8 S xx s m= √ ¿ 2
x i
∑¿
¿ ¿ ¿ ¿ ¿ N −¿ 2
1
¿ s b= s r √ ¿
Page )0 o& )5
Chem126 Lab – Instrumental Analysis
∫ ¿− Σyn y ¿
¿ ¿
2
0.040304054
1 1
+
1 5
( +
0.0824
−
0.3590 5
)
2
(¿¿ 2)( 14.8 )
2.28 × 10
−2
0.02560434 2
√ ¿
¿
( ¿¿ m S xx ¿|=¿ 1
¿ 1 + +¿
M N sr
√ ¿
m sc =¿
uncertainty =√ ( 2.28 × 10 ) +( 5.93 × 10 ) +( 1.66 × 10 ) +( 6.22 × 10 ) =6.22 × 10 −2
2
−3
2
−2
2
−1
2
−1
UAll calculations &or the remaining schemes are done is the same way shown.
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