Extraction and Spectrophotometric Determination of ...

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Extraction and Spectrophotometric Determination of Manganese(VII) with 1

1

2

N -Hydroxy-N ,N Diphenylbenzamidine a

Dejene Ayele & B. S. Chandravanshi

a

a

Department of Chemistry, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia Version of record first published: 23 Oct 2006.

To cite this article: Dejene Ayele & B. S. Chandravanshi (1990): Extraction and 1

1

2

Spectrophotometric Determination of Manganese(VII) with N -Hydroxy-N ,N Diphenylbenzamidine, Analytical Letters, 23:9, 1729-1741 To link to this article: http://dx.doi.org/10.1080/00032719008052521

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ANALYTICAL LETTERS, 2 3 ( 9 ) , 1 7 2 9 - 1 7 4 1 ( 1 9 9 0 )


EXTRACTION AND SPECTROPHOTOMETRIC DETERMINATION OF MANGANESE(VI1) 1 1 2 WITH N -HYDROXY-N ,N -DIPHENYLBENZAMIDINE

KEY WORDS:

1 1 2 Manganese determination, N -Hydroxy-N ,N -diphenylbenzamidine, Steel analysis, Tea analysis Spectrophotometry

Dejene Ayele and B.S. Chandravanshi

*

Department of Chemistry, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia

ABSTRACT Spectrophotometric determination of manganese(VI1) after

its extraction

with N -hydroxy-N1 ,N2-diphenylbenzamidine

into amyl alcohol at pH 7-8 is described. ed f o r 0.1-10 yg ml

at 614 mn

1

-1

Mn(VI1).

Beer's law was obey-

The effects of experimental va-

riables and of several diverse ions on the determination of manganese(VI1) to

the

have

been

studied.

The method has been epplied

determination of manganese in steels 2nd in water ex-

tracts of a commercial tea and is found to be simple, precise and highly selective. INTRODUCTION d-Hydroxy-N', N2-diphenylbenzamidine spectrophotometric

*To whom

determination

of

has been used for the

vanadium

correspondence should be addressed. 1729

Copyright Q I990 by Marcel Dekker, Inc

1

,

and

AYELE AND CHANDRAVANSHL

1730 4

cobalt

.

1

A number of N -hydroxy-N1,N'-diarylbenzamidines

have

also been reported as reagents for the spectrophotometric determination of manganese( I I) in aqueous/ethanol medium5 ' How-

6

ever, these methods require at least one hour standing time for maximum color development.

These methods also suffer from se-

rious interference from Cu(II),


V(V),

Ni(II),

Co(II),

Pd(II),

oxalate, and EDTA, most of which are normally

Fe(III),

associated

with manganese in common samples and therefore, they find only limited applicstions.

Furthermore, there are no reports in the

literature about the possible reaction of permanganate with these reagents

under

permanganate

any

with

conditions. Hence the reaction of 1 N -hydroxy-N1 ,N'-diphenylbenzamidine, the

parent compound of the series, has been studied in detail under different experimental conditions to develop a rapid, precise, accurate,

and

selective method

for

the

spectrophotometric

determination of manganese in diverse samples. 1 2 The present paper deals with the use of N1-hydroxy-N ,N diphenylbenzamidine and

the

(HDPBA) as an extractant for permanganate,

application of the method to

the spectrophotometric

determination of manganese in steels and in water extracts of a tea sample, after oxidation of manganese(I1)

to manganese(VI1)

by periodate.

EXPERIMENTAL Equipment

A Beckman Model 24 UV-Visible spectrophotometer equipped with matched 1-cm quartz cells and a recorder were used for recording the absorption spectra and absorbance measurements. Beckman

A

Chem Mate pH meter was used for the pH measurements.

A Varian Tectron Model 575 Series atomic absorption spectrometer with air-C H flame system was also used for the determination 2 2 of manganese.

1731

SPECTROPHOTOMETRIC DETERMINATION OF MANGANESE ( V I I ) Reagents and Solutions solution of manganese(VI1)

A stock

was

prepared by dis-

solving 1.5794 g of potassium permanganate (AnalaR, BDH) in 500 ml

of water,

filtering

boiling

through

a

the

solution gently

sintered

manganese(1V) oxide formed,


watar.

A

and

glass

of manganese(I1)

in water,

any

to exactly 1 R with

was prepared by dissolving

sulphate monohydrate (AnalaR, BDH)

500

exactly

ml

with

water,

and of manganese(I1)

manganese

content

of

complexometrically with EDTA HDPBA C,

remove

acidifying with dilute sulphuric acid, and diluting

manganese(VI1)

0

to

This solution was stored in a dark brown glass bottle.

0.8450 g

The

filter

diluting

stock solution of manganese(I1)

to

for 1 h, cooling,

was

reported'

prepared

163

0

C.

7

by

the

More

dilute

solutions of

were prepared as required. solutions

were

determined

. the reported method, m.p.

162-163

A 0.01 M solution of the reagent in amyl

alcohol was used f o r the extraction of manganese(VI1).

A

5%

(w/v)

potassium

periodate solution was prepared by

dissolving 25 g of potassium periodate in a mixture of 300 ml of water and 100 ml of concentrated nitric acid, gently heating to

complete dissolution, cooling and diluting to 500 m l with

water.

A 10% (w/v) ammonium fluoride solution in water was used

for masking of iron(II1)

in the samples.

A sulphuric/phosphoric

acid solution was prepared by mixing 150 nil of concentrated sulphuric acid and 150 ml of 85% orthophosphoric acid, and carefully adding the mixture to 600 ml of water, cooling and diluting to exactly 1 R.

All other chemicals used were of analytical grade.

General Procedure An aliquot ( 5 ml) of the solution containing up to 100 ug of manganese present as manganese(VI1)

was transferred into a

50-1111 beaker and 5 ml of 10% (w/v) ammonium fluoride was added

AYELE AND CHANDRAVANSHI

1732 to

it.

the solution w a s

The pH of

using 3 M

a d j u s t e d t o 7-8

ammonia s o l u t i o n (and 3 M n i t r i c a c i d when n e c e s s a r y )

and t h e

solution

separa-

tory

was

transferred

q u a n t i t a t i v e l y i n t o a 100-ml

A 5 m l a l i q u o t o f 0 . 0 1 M s o l u t i o n o f HDPBA i n amyl

funnel.

a l c o h o l was added t o t h e f u n n e l , t h e m i x t u r e was shaken v i g o r o u s ly

f o r 2 min,


The

and t h e

f u n n e l was a l l o w e d t o s t a n d f o r 2-3 min.

aqueous phase was s e p a r a t e d

lected

i n a 50-ml

beaker

and t h e o r g a n i c p h a s e was c o l -

containing

about

1 g of anhydrous so-

The aqueous p h a s e was t r a n s f e r r e d back t o t h e

dium s u l p h a t e .

s e p a r a t o r y f u n n e l and washed w i t h a b o u t 3 m l of amyl a l c o h o l . The washing

was

mixed

with

i n t o a 10-ml

quantitatively

volume w i t h amyl a l c o h o l . was

the

measured

at

colored

extract

and

transferred

v o l u m e t r i c f l a s k and d i l u t e d up t o

The a b s o r b a n c e of t h e c o l o r e d s o l u t i o n

614 nm a g a i n s t

t h e reagent blank prepared

in

t h e same manner.

P r o c e d u r e f o r Samples Steel. 1-2%

A c c u r a t e l y weighed

were

manganese

sulphuric/phosphoric

was

mixture boiled

to

in

ml

15

of

the

w i t h 15 m l o f

The

concentrated n i t r i c acid,

and e v a p o r a t e d t o d r y n e s s and

n i t r o u s fumes,

The r e s i d u e was b o i l e d w i t h 50 m l o f w a t e r t o d i s s o l v e

cooled. soluble

dissolved

a c i d m i x t u r e i n 250-ml c o n i c a l f l a s k s .

oxidized

expel

g s t e e l samples c o n t a i n i n g

0.1

salts.

necessary)

The

solution

i n t o a 250-ml

was

beaker.

cooled

and

filtered

(when

The s o l u t i o n was d i l u t e d t o

70 m l w i t h w a t e r and 1 0 m l of c o n c e n t r a t e d n i t r i c a c i d was added to

it.

The s o l u t i o n was b o i l e d

potassium 4

min.

f o r 2 min,

1 0 m l o f 5% (w/v)

p e r i o d a t e s o l u t i o n was added, and b o i l e d f o r a f u r t h e r The

solution

was

cooled,

transferred

v o l u m e t r i c f l a s k and made up t o volume w i t h w a t e r

Tea. 150 m l of

A c c u r a t e l y weighed 3 g of b o i l i n g w a t e r i n a 500-ml

8

to

a

100-ml

.

t e a powder was added t o conical flask,

boiled f o r

SPECTROPHOTOMETRIC DETERMINATION OF MANGANESE (VII)

1733

5 to 20 min as required, and filtered through a Buchner funnel.

The clear extract was transferred to a 250-ml Kjeldhal flask, evaporated to dryness, and cooled.

The residue was decomposed

with a 10 ml mixture of nitric, sulphuric, and perchloric acid in the ratio 3:l:l and evaporated to dryness.

The residue was

boiled with 50 ml of water to dissolve soluble salts.

The solut-


ion was cooled, 5 ml of concentrated nitric acid was added, and the resultant solution boiled for 5 min. 5%

(w/v)

A 10 ml aliquot of

potassium periodate solution was then added and the

mixture was boiled for a further 2 min.

The solution was co-

oled, transferred to a 100-ml volumetric flask, and diluted to the mark with water. The manganese content of the sample solutions were determined by the general procedure. 0.30.

For calibration curve, 0.05, 0.10,

0.70, and 1.00 ml of 100 vg ml

-1

Mn(VI1)

solution were

used through the general procedure.

RESULTS AND DISCUSSION Color Reaction and Absorption Spectra Manganese(I1)

was

found to react slowly with HDPBA

in

aqueous/ethanol medium to give a deep green complex in the pH range 6.5-8.5 on exposure to air.

The spectrum of the complex

showed a broad absorption band at around 614 nm.

However, the

absorbance continued to increase with time and the reaction was found to be incomplete even after 6 h. conducted

in the presence

When the reaction was

of hydroxylamine hydrochloride the

system was found to give no color formation.

These results in-

dicate that the manganese species involved in the complex formation with HDPBA is not manganese(I1) but most likely to be manganese(II1)

resulting from the oxidation of manganese(I1) 9

mospheric air

.

In contrast to manganese(II),

by at-

manganese(VI1)

1734


was found to react rapidly with HDPBA in aqueous/ethanol medium in the pH range 3.5-9.5 to give the deep green complex immediately.

The spectrum of the complex showed an intense and broad

absorption constant

band

at

around 614 nm and the absorbance remained

for 4 days.

The exhibition of identical absorption

spectra by the deep green complex species formed by the react-


ion of both manganese(I1)

and manganese(VI1)

with HDPBA, res-

pectively, indicates the formation of identical complex species in

both

systems.

manganese(II1)

by

Thus manganese(V1I) ethanol which

is probably reduced to

forms the deep green complex

with HDPBA. The

deep green complex was found to be extractable into

higher alcohols such as n-butanol, n-hexanol, and n-amyl alcohol.

The absorption spectra of the complex were found to be

similar in all the solvents with absorption maximum invariably at

around 614 nm.

However minor variations in the intensity

of the absorption band were found. cohol gave the greatest sensitivity.

Of the solvents, amyl alHence the detailed study

has been conducted with amyl alcohol as the solvent for the extraction

of

the deep green complex formed by the reaction of

permanganate with HDPBA. The

spectrum of

HDPBA

in amyl alcohol did not show any

significant absorption between 500 and

700 nm.

However all

absorbance measurements have been made against the reagent blank to ensure maximum accuracy.

Effects of Experimental Variables The optimum pH range of the aqueous phase f o r the complete extraction of manganesefVI1) was found to be 3.5-9.5. At lower pH extraction of manganese(VI1)

decreased because of incomplete

complexation due to the protonation of the ligand.

At higher

SPECTROPHOTOMETRIC DETERMINATION OF MANGANESE (VII) pH extraction of manganese(VI1)

decreased probably due to format-

ion of manganese species other than manganese(II1). found that when manganese(VI1) presence of excess of

1735

It was also

was extracted at pH < 7 in the

potassium periodate the color of

the

complex changed from green to brown and resulted in some shift of

absorption maximum


when manganese(VI1)

towards shorter wavelengths.

However,

was extracted in the presence of excess of

periodate at pH 7-8 no shift in the absorption maximum of the green complex was observed and the results obtained were identiF o r this reason the

cal with that of standard manganese(VI1). of

extraction

manganese(I1)

manganese(VI1)

from

sample solutions, in which

was oxidized to manganese(VI1)

by excess of per-

iodate, was carried out at pH 7-8.

A minimum of an 8-fold molar excess of the reagent, HDPBA, was found to be necessary for the complete extraction of manganese(VI1)

from the aqueous phase.

A large excess up to 100-fold

molar excess of HDPBA has been found to have no adverse effect on the extraction efficiency of the system. Manganese(VL1) amyl

was

found to be completely extracted into

alcohol with HDPBA within 2 min.

The absorbance of the

colored extract remained constant for 4 days at room temperature and then decreased gradually due to decomposition of the green complex.

It has been found that the ratio of

the volumes of

the aqueous to the organic phase can be varied from 1:l to 5:l without any significant variation in the extraction efficiency of

the

decrease

system. in

repetitive complete

not

ficiency

higher

volume

ratios there was

the degree of extraction of manganese(VI1). extractions

were

found

to be

extraction of manganese(VI1)

the aqueous phase. did

At

produce of

the

from

necessary

gradual Hence for

larger volumes of

Variation in temperature between 20 and 40 any measurable system.

change

The

the 0

C

in the extraction ef-

degree

of

extraction

of


1736 Table 1.

Photometric Characteristics of the System


X max, nm -1 -1 E, II mol cm

614 3 5.35 x 10

13 Sandell sensitivity , -2 ug cm Mn(VI1) 12 Limit of determination , -1 pg ml Mn(VI1)

0.01

0.02

Concentration range from Beer's law, -1 ug ml Mn(VI1)

0.1

-

10

Optimum concentration range from 14 -1 Ringbom's plot , pg ml Mn(VI1)

1.4

-

8.8

Relative standard deviations, (n = 6 ) , %

0.6

manganese(VI1)

did not

aqueous phase was potassium nitrate. was

established

varied between 0 to 2 M

(Mn

:

HDPBA).

with respect to

The composition of the deep green complex spectrophotometrically

continuous variationlo 1:3

change when the ionic strength of the

and

by

the

method of 11,12 the extraction method to be

These results indicate that the proposed

method is relatively free from the rigid control of experimental variables. Photometric Characteristics The photometric characteristics of the colored system have been evaluated and are summarized in Table 1.

The data given

in Table 1 clearly indicate that the proposed method is sensitive and gives reproducible

results.

SPECTROPHOTOMETRIC DETERMINATION OF M.4NGANESE ( V I I ) T a b l e 2.

T o l e r a n c e L i m i t o f D i v e r s e Ions i n t h e D e t e r m i n a t i o n o f 4 ug m 1 - I

Mn(vI1)

Tolerance l i m i t

Ion


Li

+,

Na

+,

+

K + , NH4

3C 1 0 4 , PO4

,

,

C1-,

NO;,

2-

SO4

,

oxalate, borate, 2000a

f l u o r i d e (each) Ca

2+

1737

,

Sr

2+

, A1

2S208 , lo4,

3+

,

Zn

2+

2-

, Moo4 ,

2W04

,

acetate, tartarate,

p h t h a l a t e , c i t r a t e (each)

BOOa

Mg2+

700

Cd2+

600

Fe

3+

600b

EDTA, B e 3+ La 3-

2+

,

Pb

2+

(each)

270 260

As04

Sn

4+

,

Ba

Th4+, Z r

2+ 4+

180

(each)

,

2+ 3+ U02 , C r (each)

160 60'

C r 022 7 Cu2+, Hg2+, N i 2 +

(each)

40

30

co2+ VO;,

320

Ce

4+

(each)

sc

a s h d i e d up t o t h e i n d i c a t e d amount o n l y . bMasked by ammonium f l u o r i d e . C

Causes p o s i t i v e i n t e r f e r e n c e when p r e s e n t i n amounts greater than the tolerance l i m i t .


1738 Table 3.

Determination of Manganese in BCS Steels

Manganese content (% w/w)

BCS steel


No.

Found

Certified

*

239/3

0.87

0.864 5 0.007

214/2

1.61

1.60

5 0.02

256/1

1.02

1.01

f 0.01

*Mean

f 95% confidence limits for 6 replicates.

Effects of Diverse Ions To evaluate the selectivity of the newly developed method, the effects of several diverse ions on the determination of manganese(VI1)

with

HDPBA

have been studied by the general pro-

cedure.

The ions that cause an error less than 2% in the deter-1 of manganese(VI1) are given in Table 2. mination of 4 pg ml These results clearly indicate that most common ions normally associated with manganese in ores, alloys, steels, aiid biological samples do not interfere in the determination of manganese by the proposed method. by

The interference of irorl(II1) was overcome

masking it with fluoride.

However, reducing agents should

be absent. Application The analytical potentialities of the newly developed method has been assessed by determining the manganese content of British Chemical

Standard

(BCS) steels.

The experimental results (Table

3 ) are in good agreement with the certified values.

1739

SPECTROPHOTOMETRIC DETERMINATION OF MANGANESE ( V I I ) Table 4 .

Determination of Manganese in Water Extracts of a Commercial Tea Sample


(3 g tea was boiled with 150 ml of water)

*

Extraction

Manganese Found

condition

Proposed method

(wg g

-1

tea)

AAS method

Single extraction for 5 min

320 k 3

325

First extraction for 20 min

340 f 4

346 +- 12

Second extraction for 20 min

19.3 2 0.2

19.6 k 0.5

9 . 4 f 0.1

9 . 7 +- 0.3

Third extraction for 20 min

*Mean

f 95% confidence limits for 6 replicates.

The proposed method has also been applied to of water extracts of

Impex C o ( K ) The

+- 10

the

analysis

a commercial tea sample (Red lebel, Almeta

Ltd., Idambassa, Kenya) f o r its manganese content.

manganese content of the extracts was also determined by

AAS as a standard method to compare the results obtained by the newly 4.

developed method.

The results are summarized in Table

These results indicate that about 90% of total manganese

that can be extracted into water from tea sample is extracted into water within 5 min, and prolonged and successive boiling of the tea sample in water increases the extraction of manganese only slightly.

The results obtained also indicate that every

cup of tea, prepared by boiling 3 g of tea sample in 150 ml of water, contains about 0.96 mg of manganese.

The results obtain-

1740 ed


by t h e proposed method are a l s o i n good agreement w i t h t h a t

of AAS.

Hence t h e newly d e v e l o p e d method i s p r e c i s e and r e l i a b l e

and can be a p p l i e d t o t h e d e t e r m i n a t i o n of manganese i n d i v e r s e samples.


ACKNOWLEDGEMENT The

authors

Chemistry,

are

Addis

grateful

Ababa

t o t h e Chairman,

University,

Department of

Addis Ababa,

Ethiopia,

for

providing laboratory f a c i l i t i e s .

REFERENCES

1.

Satyanarayana

K.

and

R.K.

Mishra,

Anal.

Chem.,

46, 1609

(1974). 2.

K.

S a t y a n a r a y a n a and R . K .

Mishra,

J . I n d i a n Chem. S o c . ,

53,

6 3 (1976). 3.

Moges,

G.

Jpn., 57, 4.

G.

D . A s s e f a and B.S.

C h a n d r a v a n s h i , B u l l . Chem. SOC.

866 ( 1 9 8 4 ) .

Moges and B.S.

Chandravanshi,

Ann. Chim.

(Rome),

I n d i a n Chem.

Soc.,

2,627

(1984).

5.

K.S.

P a t e 1 and R . K .

Mishra,

J.

hlohabey

and

55,

773

(1978). 6.

P.K.

Sharma,

Indica,

H.L.

[Ser.]

Chem.

, 8,

R.K.

198 ( 1 9 8 2 ) ;

Mishra.

Acta

Anal. A b s t r . ,

Cienc.

44,

566

(1983). 7.

H.A.

Flaschka,

EDTA T i t r a t i o n s ,

2nd Ed.,

Pergamon,

Oxford,

p . 81 (1967). 8.

D.T.

Burns

and

D.

Chimpalee,

Anal.

Chim.

Acta,

199,

241

(1987). 9.

F.A.

Cotton

and

G . Wilkinson,

Basic

I n o r g a n i c Chemistry,

Wiley E a s t e r n , N e w D e l h i , p. 397 (1982). 10 * P. J o b , Ann. Chim.

(Paris),

2,

113 (1928).

SPECTROPHOTOMETRIC DETERMINATION OF MANGANESE ( V I I ) 11. J.

1741

Inczedy, Analytical Applications of Complex Equilibria,

Ellis Horwood, Chichester (1976). 12. Z. Holzbecher, L. Divis, M. Kral, L. Sucha and F. Vlacil,

Handbook

of

Organic

Reagents in Inorganic Analysis, Ellis

Horwood, Chichester (1976). 13. E.B. Sandell, Colorimetric Determination of Traces of Metals,


3rd Ed., Interscience, New York (1959). 14. A . Ringbom, Z. Anal. Chem.,

115,332

(1939).

Received A p r i l 5, 1990 Accepted J u l y 9, 1990