menthyl gloxime.pdf

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MEMOIRS OF THE FACULTY OF ENGINEERINGFUKUI UNIVERSITYVOL.27 No. 1 1979

Spectrophotometr ic de te rmina t ion o f nickel by adsorp t ionof n icke l dimethylglyoximate on naphthalene

*asatada SATAKEReceived Jan . 10, 1979

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Adsorpt ion of n icke l dimethylglyoximate on naphthalene wa s success fu l ly appl ied to the de te rmina t ion of microamounts of nicke l . To about40 ml of sample so lu t ion conta in ing 1-9 ml of 20 ppm n icke l so lu t ionwere added 1 .0 ml of 0.5% dimethylglyoxime in e thanol and 2.0 ml ofbuffer so lu t ion to ad jus t the pH to 6.0-11 .0 . The so lu t ion was mixedthoroughly , and 4.0 ml of 10% naphthalene in acetone were added. Aftershaking vigorously fo r about 1 min, the mixture of the n icke l complexand naphthalene c rys ta l s was f i l t e r ed off on a s in te r ed-g las s disc andthen dr i ed . The red c rys ta l s were disso lved in chloroform, the r e su l t ing yellow so lu t ion wa s di lu ted to 10 m13 and i t s absorbance was measured a t 375 nm agains t the reagent blank. The molar absorp t iv i ty ofthe nickel complex a t 37 5 nm was 3.2xl0 3 l 'mol - l ' cm- l , the sen s i t i v i t ybeing 0.019 ~ g / c m 2 per 0.001 of the absorbance. The c oe f f i c i e n t ofva r i a t i on for the de te rmina t ion of 100 ~ g of n icke l was 1.2% ( 10 de t e -rmina t ions ) . Various a l k a l i metal s a l t s and metal ions , except fo rEDTA, did not i n t e r f e r e with the de te rmina t ion .

1 In t roduct ionDimethylglyoxime, one of th e a-dioximes 3 has been widely employed

for the grav imetr ic and so lvent ex trac t ion-spec t rophotometr ic d e t e r minat ion of the t r ace amounts of n icke l or pal ladium.

We have been s tud ing a new method involv ing the adsorp t ion of themetal complexes on naphthalene and have a l ready appl ied it to the dete rmina t ion of t r ace nickel l ) with a-fur i ld iox ime as the complexforming reagent . In the presen t communication, a dimethylglyoxime waschosen as a s ign i f i can t complex-forming reagent fo r the de te rmina t ionof t r ace n i cke l . This reagent forms a water- inso lub le red complexwith nicke l , which i s qua n t i t a t i ve ly adsorpted as the nickel complex onmicrocrys t a l l i ne naphthalene a t room t empera ture . The mixture of the* Division of Applied Science


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complex an d crystals is dissolved in chloroform, and i t s absorbance i smeasured a t 375 nm. This method ca n be successfully applied for theanalysis of t race nickel , as well as chloroform and naphthalene methods.

2 Experimental method2.1 ReagentsStandard nickel solut ion, 20 ppm. Prepared by di lu t ing standard

nickel solution (1000 ppm, Wako Pure Chemical Industr ies LTD, Osaka,Japan) to 1000 ml with water .

Dimethylglyoxime solut ion, 0.5%. Prepared by dissolving 0.5 g ofdimethylglyoxime in 100 ml of ethanol .

Buffer solutions were prepared by mixing sui table amounts of 1Macetic acid and 1M ammonium acetate solution at pH 3-6, or 1M ammoniawater and 1M ammonium acetate solution at pH 8-11.

All other solutions were prepared with analyt ical reagent-gradechemicals by using deionized water.

2.2 ApparatusA Hitachi Model 200-20 double beam spectrophotometer was used for

the absorbance measurements with 10 mm glass ce l l s . The pHmeasurements were made with a Toa-Dempa Model HM-5A, pH meter, equipped withcombined glass and calomel electrodes.

2.3 ProcedureA ser ies of sample solutions was prepared containing 1-9 ml of 20ppm nickel solut ion, 2.0 ml of the buffer solution(pH 9.5) and 1.0 mlof 0.5% dimethylglyoxime solution in about 50 ml of to ta l volume. Mixthe solutions well and stand for 5 min a t room temperature. After4.0 ml of 10% naphthalene-acetone solution were added, the mixing sol -lu t ions were shaken for 1 ~ i n vigorously. Fi l te r them through a funnelattached with a disc-shaped f i l te r (No. 5C, f i l t e r paper) by aspira t ion.Wash with water and dry in a dryer. Then dissolve them in chloro-form and make up to 10 mI. Measure the a b s o ~ b a n c e s of the so-lu t ions in 10 mm glass ce l l s against the reagent blank prepared s imil arly.

3 Results and discuss ion3.1 Absorption spectraNickel in the sample solution containing 100 pg of nickel was ad

sorpted on microcrystal l ine naphthalene as the nickel complex. Themixture of the complex and naphthalene was dissolved in chloroform

, and the absorbance of the solution was measured a t various wavelengths between 330 and 470 nm. The resul t obtained is shown in Fig . l .


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The absorp t ion curve of the n ic k e l complex has two maximum peaks a t 375and 425 nm, while t h a t o f the reagen t blank does not show any apprec i ab le absorp t ion a t longer wavelengths above 340 nm. Therefore , 375 nmwa s adopted as the opuimum wavelength fo r th e absorbance measurement.

3.2 Effec t of pHAccording to the recommended procedure , sample solut ion conta in ing

100 ~ g of n ic k e l and 1 .0 ml o f 0.5% dimethylglyoxime solut ion was ad jus ted in the pH range of 4 .5-11 .0 by adding respec t ive buffe r so lu t ion .Then the adsorp t ion o f the complex was ca r r i ed out with microcrys ta l l inenaphthalene a t room temperature . The adsorpted mixture of the complexand c ry s t a l s was disso lved in chloroform and i t s absorbance was measured.The pH o f the so lu t ion was measured a f t e r adsorp t ion . Figure 2 showsthe e f f e c t of the pH on the absorbance. Th e absorbance s t a r t s from pH4 .5 , sharply inc reases with inc reas ing pH and reaches almost cons tan tand maximum a t pH 5 .8-11 .0 . Therefore , the pH of the solut ion was ad jus ted to 9.5 fo r the absorbance measurement.

3.3 Effec t of reagent concentrat ionTo sample solut ion conta in ing 10 0 pg of n ic k e l and 2.0 ml o f the

buffer solut ion(pH 9.5) in t o t a l volume of approximately 50 ml, 0 .1-5 .0ml o f 0.5% dimethylglyoxime solut ion was added, and the adsorp t ion wasca r r i ed out according to the recommended procedure . F igure 3 shows thee f f e c t of the amounts of dimethylglyoxime on the absorbance. From

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UJu 0.6IX)ILl 0.6uz

Q::0en 0.4X)ex:0:: 0.4enex:

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0o 2 4 6 8 ro 12330 350 370 3!}) 410 4:i) 450 470 pHWAVELENGTH, Ii'1 FJ G. 2 EFFECT OF pH

FIG. I ABSORPTION SPECTRA OF DIMETHYLGLYOXIME AND N I: 100 ; WAVELENGTH : 375 NM ; 0.5% DIMETHYL-NICKEL COMPLEX IN NAPHTHALENE-chloroform GLYOXIME : 1.0 ML ; 10% NAPHTHALENE-ACETONENI : 100 PG ; 0.5% DIMETHYLGLYOXIME : 1.0 ML ; : 4.0 ML ; DIGESTION TIME: 5 MIN; SHAKING TIMEpH : 9.5 ; 10% NAPHTHALENE-ACETONE: 4.0 ML ; : I MIN; STANDING TIME: 10 MINREFERENCE: WATER; (I) REAGENT BLANK I (2 ) NICKEL REFERENCE: REAGENT BLANKCOMPLEX


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the experimental resu l t , the absorbance increased sharply with increasing amounts of the reagent up to 0.1 ml of 0.5% dimethylglyoxime solut ion and remained almost constant between 0.1 and 1.0 mI. When 5.0ml of this solut ion were added, the absorbance decreased by less than5%. Therefore, 1.0 ml of 0.5% dimethylglyoxime solut ion was added forthe absorbance measurement.

3.4 Effec t o f buf f e r so lu t ionFigure 4 shows the effec t of addition of the buffer solution(pH 9.5)

on the absorbance of the complex. The addition of 0.5-5.0 ml of thebuffer solut ion gave no effec t on the absorbance. Therefore, 2.0 ml ofthe buffer solut ion were taken for the absorbance measurement.

0.8w 0.6uzc(II I0:: 0.4enIII


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complex on the absorbance was s tud ied . From the experimental r e s u l t ,the format ion of the complex was very f a s t , and the d iges t ion was foundto be unnecessary. Therefore , 2 min of diges t ion t ime was chosen fo rthe absorbance measurement.

3.7 Ef fec t of shaking t ime4 .0 ml of 10% naphthalene-acetone so lu t ion were added to the so -

lu t ion conta in ing the n icke l complex and th e adsorp t ion of the complexwas performed according to the recommended procedure. Figure 6 showsthe e f f e c t of shaking t ime on the absorbance. No change was seen inthe degree of adsorp t ion when the shaking t ime was var ied from 3 to 18 0seconds. Therefore , 60 seconds were chosen as shaking t ime fo r theabsorbance measurement.

0,8LU 0,6uz.00:: 0,4(/ ).0c:r::

0,2o o 2 4 6 8 10 12 1410% NAPHTHALENE-ACETONE, ML

FIG, 5 EFFECT OF NAPHTHALENE CONCENTRATIONNI : 100 PG ; pH : 9,5 ; WAVELENGTH: 375 NM ;0,5% DIMETHYLGLYOXIME : 1,0 ML ; BUFFER SOLUTION: 2,0 ML ; SHAKING TIME: I MINREFERENCE : REAGENT BLANK

0,80,6LUuz.0 0,4::0(/ )

.0c:r:: 0,2o - - ~ - - ~ - - - - ~ ~ ~

o 20 40 60 120 180SHAKING TIME, MINFIG, 6 EFFECT OF SHAKING TIMENI : 100 PG ; pH : 9,5 ; WAVELENGTH: 375 NM0,5% DJMETHYLGLYOXIME : 1,0 ML ; DIGESTIONTIME : 5 MIN; STANDING TIME ': 10 MINREFERENCE : REAGENT BLANK

3.8 Effec t o f volume of aqueous phaseThe volume of aqueous phase conta in ing 100 ~ g of n ic ke l , 2.0 ml of

the buffer so lu t ion (pH 9.5) and 1 .0 ml of 0.5% dimethylglyoxime so -lu t ion was var ied from 50 to 1000 m l, and the adsorp t ion of the complexwas performed by vigorous shaking according to the recommended proce-dure . Figure 7 shows the e f fec t of volume of aqueous phase on the absorbane. The absorbance decreased gradua l ly with increas ing volume ofaqueous phase .

3 .9 Effect of s tanding t imeThe mixture of the complex and naphthalene c rys ta l s was disso lved in

chloroform, and the e f fec t of s tanding t ime on the absorbance of thechloroform so lu t ion was i nves t iga ted between 5 and 120 min. The r e su l t


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is shown in Fig. 8. The complex in naphthalene-chloroform solutionis very stable and the change of the color was not almost recognized.Therefore, 10 min of standing time were chosen for the absorbance measurement.

0.8w 0.6zI:Qa::0 0.4/)I:Qcc

0.2

a 0 200 400 600 800 1000VOLUME OF AQUEOUS PHASE. ML

FIG. 7 EFFECT OF VOLUME OF AQUEOUS PHASENI : 100 j WAVELENGTH: 375 NM j pH : 9.50.5% DIMETHYLGLYOXIME : 1.0 ML i 10% NAPHTHALENE-ACETONE : 4.0 ML i DIGESTION TIME : 2 MINREFERENCE : REAGENT BLANK

3.10 Cal ibra t ion curve

0.8

t1 0.6z ( ) ' )o< 'I:Qg 0.4~

0.2

a I a 10 20 30 40 100 120STANDING TIME. MIN

FIG. 8 EFFECT OF STANDING TIMENI : 100 ; 0.5% DIMETHYLGLYOXIME : 1.0 ML ;pH : 9.5 j WAVELENGTH: 375 NM ; SHAKING TIME: I MIN j STANDING TIME : IO MINREFERENCE : REAGENT BLANK

With the optimum conditions descr ibed above, the cal ibrat ion curvefor nickel determination was established a t 375 nm against the reagentblank. The resul t is shown in Fig. 9. I t was l inear over the rangeof 10-186 ug of nickel in 10 ml of chloroform. The molar absorpt ivi ty3 -1-1was calculated to be 3 . ~ x l O l mol cm , t h e sens i t iv i ty being 0.019Pg of nickel per cm 2 for the absorbance of 0.001. Ten sample solutioncontaining 100 Pg of nikel , prepared by the recommended procedure, gavea mean absorbance of 0.540 with a re la t ive standard deviat ion of 1.2%.

3.11 Effect of d iverse ionsThe solutions containing 100 Pg of nickel were prepared with varyingamounts of the diverse ions and sa l t s , and the determination of nickel

was performed. Some of the resul t s are given in Tables 1 and 2. Onehundred micrograms of bismuth gave no in ter ference , but 200pg of i t did.Especially, even a small amount of EDTA gave serious negative in ter-ference. Other diverse metal ions and sa l t s did not interfere withdetermination of nickel .


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40 80 120 160 200NICKEL, pG/IO ML DMF

FIG. 9 CALIBRATION CURVE FOR NICKELWAVELENGTH: 375 NM ; 0.5% DIMETHYLGLYOXIME : I.O ML ;pH : 9.5 i IO% NAPHTHALENE-ACETONE: 4.0 ML ; DIGESTIONTIME : 2 MIN i SHAKING TIME : 1 MINREFERENCE : REAGENT BLANK

Table I Effec t of a lka l i sa l t sAlkali sa l t s Amount added(mg) Absorbance(375 nm)

0.540Na 2S04 100 0.542" 500 0.548CH 3COONH 4 100 0.545" 500 0.550NaCl 100 0.535" 500 0.550

NH 4Cl 100 0.546" 500 0.538

(NH4)2C204H20 100 0.532" 500 0.540

NaH 2P04 100 0.555" 500 0.545K2HP o4 100 0.548" 500 0.532KN0 3 100 0.545" 500 0.549KBr 100 0.548" 500 0.543

CH 3COONa 100 0.545" 500 0.548

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Sodium c i t ra te 100 0.539" 500 0.519

Sodium t a r t ra te 100 0.537" 500 0.548EDTA 2 0.002

Nickel 100 pg, pH 9.5, Naphthalene : 0.4 gTable 2 Effect of diverse metal ions

Metal ions Ion added ()lg) Absorbance(375 nm)0.540

Pb 2+ 100 0.530" 200 0.550Fe 3+ 100 0.535" 200 0.502Cu 2+ 100 0.534" 200 0.530Co 2+ 100 0.528" 200 0.532" 300 0.548Zn 2+ 100 0.551" 200 0.540Cd 2+ 100 0.546" 200 0.538Mn2+ 100 0.535II 200 0.551cr 6+ TOO 0.548" 200 0.547" 300 0.560Bi3+ 100 ,0.551" 200 0.588" 300 0.623

Ni : 100 pg, pH" 9.5 , Naphthalene 0.4 gReference1) M. Satake, Y. Matsumura, T. Fujinaga, Y. Takagi, Bunseki Kagaku, 27,

486 (1978).

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