Microanalysis with the aid of ion exchangers

ANALYTICA

MICROANALYSIS PAR-I’

XXI’.

WITH

CHIMICA

THE

AID

ACTA

OF ION

373

EXCHANGERS*

MODIFICATIONS OF THE RESIN SPOT HIGH MOLECULAR WEIGHT AMINES FUJ IAIOT0

iUAS.~TOSl-IL D,cpuufmoiL of Chenlislry, Dcpu~f~nc1~1 o_f Chcmislry.

Facrilly

of Scicncr.

AND YUKIO The

TEST

WITH

N.l\liA\TSIJ ICASA

Ut~iversily of Tokyo, Hottgo, Tokyo (.Japnn) CJriDa Universily. J\‘o,lclkadni-rnnclri, CJliba

Fucrrlly of cl rls a,nd Scicrtces, (Jaflarr)

(Received

lhxmber

I I th, 1901)

The microchemical applications of high molecular weight amines (HhlwA),** so-called liquid anion es&angers, have been investigated as reaction media for micro dctection of ions, in an attempt to improve and dstcnd the range of resin spot tests; such tests have been estensivcly developed in the past decade by FUJIMOTO”~~. The essential merits of the resin spot test are the efficient concentration of traces of ions in the small space of an ion eschangcr particle” and the easy elimination of interlering substances with a charge opposite to that of the counter-ion of the resin. However, the resin spot test has a practical drawback because of the slow attainment of masimum sensitivity. As reaction media for micro tests, HMWA (or their solutions in some immiscible solvent) are superior to cross-linked ion-cschangc resins and to the usual inert immiscible solvents because of the rapid attainment of the distribution equilibria and because of their applicability to the estraction of strong electrolyte systems. Interesting results would therefore be espected when HhfwA arc applied in microdetection, similarly to the resin spot tests. As a‘typical example for colour reactions, the cobalt(H)-thiocyanate system was examined; tests involving this sensitive blue coloration on a resin or in an immiscible solvent have been esamined previously 31s. When the system is shaken with a carbon tetrachloridc solution of a HMWA, Amberlite LA-r (N-dodecyltrialkylamine), the colourless or pale yellow organic phase becomes blue or greenish blue; the colour is very similar to that obtained with strongly basic anion-eschange resins or with an immiscible solvent*** and permits the sensitive detection of cobalt(I1). Similar observations * Since various materials with ion-exchange abilities other than resins can be applied by the same principles as those in the resin spot test, the general title of the series has been revised. ** The name “HnIwA” was usccl here, since it is not yet clear whcthcr the extraction of ions by thcsc amincs is true ion exchange or not. *** Preliminary experiments showed that a 5% carbon tctrachloride solution of previously conditioned commercial Ambcrlitc LA-I absorbs strongly at wave lengths below 500 rnp (vidc infra), but has no appreciable absorption in the region 550-750 mp. The blue solution of cobalt(TI)thiocyanatc complex in the same phase shows an absorption maximum at 625 mfi and a characteristic shoulder at about 5go rnp, both of which are very similar to the absorption curve of the same system in an immiscible solvent (e.g. isoamyl alcohol-ethyl cthcr) or in the strongly basic anion-exchange resin phases~“*o. Further details will bc reported elsewhere. Anaf.

Chiet.

Ada,

27 (x962)

373-376

M. FUJIMOTO,

374

Y.

NAKATSUKASA

have been reported by ZIEGLER et at.7 who employed association of complex anions with tri-n-butyl ammonium cation followed by extraction with iso-amyl alcohol, for the detection and calorimetric determination of cobalt(I1). The use of a new ion-exchange paper, which is easily prepared by simple impreg-’ nation of filter paper with HMWA, is also proposed. SANSONI~ also already reported the use of specially prepared ion-exchange papers for the detection of cobalt(II1) with thiocyanatc. EXPERIMENTAL

Reageltts All chemicals were of reagent grade. mown: Amberlite LA-I was chosen as the HMWA. A IO”/~ (v/v) stock solution was prepared by dissolving a commercial specimen of Amberlite LA-I (vide infra) in carbon tetrachloride. The solution was purified and conditioned by washing succcssivcly with 0.3 F nitric acid, deionized water, 0.1 I; aqueous sodium hydroxide, to convert to the hydroxide form, and finally with 0.1 I; hydrochloric acid to reconvert to the chloride form. Immediately before the experiment the solution of the purified HMWA was again thoroughly shaken with 0.1 I; hydrochloric acid. Stock solution of cobalt(II) : This was prepared by dissolving cobalt(I1) chloride in 0.01 F hydrochloric acid ; a series of standard solutions was prepared by diluting this solution with 0.01 F hydrochloric acid. The solution was passed through a column of an z I; Ammonium thiocyanate: anion-exchange resin in the thiocyanate form to remove traces of iron(III)alt. Other reagents: Hydrochloric acid, nitric acid and carbon tetrachloridc were redistilled. Dropping pipettes. These were adjusted to deliver a drop of 0.04 & 0.00~ ml of cleionizcd water. MICRO

DETECTION

OF COBALT(II)

WITH

THIOCYANATE

BY

SHAKING

WITH

HMWA

Procedzcve In a micro test tube (5 mm x 50 mm) mix a clrop of the slightly acidic test solution with a drop of 2 I; ammonium thiocyanate. Shake the mixture vigorously with a drop of the carbon tetrachloride solution of the HMWA, and observe the green or sky blue colour of the organic phase; the colour appears at once in the presence of cobalt(H).

Results Increasing the concentration of the HMWA in the organic phase enhances the sensitivity df the test; the limits of identification are I, 0.5, 0.2 and 0.2 ,ug of cobalt(H) with I, 2, 5 ancl 10% carbon tetrachloride solutions of Amberlite LA-I, respectively. With solutions stronger than IO%, the brownish colour of the commercial mown in th6 organic phase interferes slightly with the detection, hence a 5% solutidn was adopted. However, the coloured impurities in Amberlite LA-I can easily be removed by a single distillation under reduced pressure ; the clistillate from a brown crude specimen at 185-200~ at 2-3 mm Hg pressure is only pale yellow. Data on the purification of HMWA will be reported in detail elsewhere. The effects of foreign substances are summarized in Table I.

MODIFICATIONS

EFFECT

Foreign

Colour of I hr orgnn’ic

d&d compound

ion

OF

phasem.b _-

---

Ti(lV) ,..

TiOSO4

V(V) Cr(III) Mn(I1)

N H4V03 IiCr(S04)2 MnSO4

Fc(III) Ni(II) Cu(I1) Zn(II) Cd(I1)

FCC13 NiCle cuso4 ZnS04 CdS04

pl Ye N Ye( Rc) pl Yc ;f - pl Ye(dk Br)

Hg(II) Mo(V1) W(VI)

Hg(NOa)e NarMoO4 N’aaW0.1

Pb(II)

I’b(NO&

cl cl (Or) cl cl cl

Sn(IV)

SnC1.j SbCls Bi(NO& Al(NO3)3 NazH1’0~

~(%I~ Al(II1) HP042C2042CaH4Qa!+ CoHa0?3-

(NH4)1Cr04 Iiochclle salt Ammonium citrate

Or cl cl(Ye) pl Ye Cl

OF THE RESIN SPOT TEST TABLE

I

FOREIGN

SUBSTAXCES

cl moun: 01 jorcign ima I/d

375

Amount of dctcctable cob& (IZ)

Limilit8g

Remark

profiorf ia

(ml

0.7 0.4

1:1.3*10~

720 530 1Goo

0.2

1:3.6*Ioa

o-7 o*t

1:8*x0*

‘30 1000 130 I(ioO IGOO

0.7 0.4

I :2-x0=

0.7

I :2*10*

0.4 0.4

I :4.103

IGOO

0.4 0.7 I 0.7 0.4

1 :4-

cl cl cl

270 320 1300 1000 II00

0.7 0.4 0.3

I :,l.10= I :8* 102 I :4.103 I :I*103 1 :I.G*ros

cl cl cl

320 1Go0 1600

0.4 0.4 0.4

1 Cl

Cl Cl

85 100

530 400 530 IGOO

I :2.5.10*

I :4.10=

1:4*

103

I :4.x0=

103

I :8*102 I :4.10* I :8*x0* I

I

0.7

:4* 103

I :t3*102 I

:4.103

I :4.103

(a) The coloration by the foreign compound only. Colour code ‘$0: cl, colourlcss; dk, dark; pl pale; Br, brown; Or, orange; Iic, red; Yc, yellow. (6) In parentheses arc shown the colours of the organic phase when I<17 is omitted (cf. Rcmarlc (d)). (c) Values obtained by comparison with a blank test. (d) A drop ot 10% ICP was added to prcvcnt intcrfcrcncc from iron(II1). (e) If the blucish colour in the organic phase is masked by colourcd compounds in the aqueous phase, the latter is removed and the organic phase is washed with a few drops of distilled water. (f) Traces of solid KI and Na&Oa were added to mask coppcr(I1). (g) Zinc(I1) was previously separated by passing the test solution containing 4 F HCl through a microcolumn of a strongly basic anion-exchange resin(RC1) 1, and cluting cobalt(I1) with 4 F HCl 0. (Ir) Mcrcury(I1) was precipitated with a few grains of NH.$SCN. (i) The sample solution was evaporated to dryness on a water bath with a drop of concentrated hydrochloric acid before the test. (I) A few drops of aqueous ammonia wcrc added and the supcrnatant solution was tested.

PREPARATION

AND

MICROCHEMICAL

APPLICATIONS

OF HMWA

PAPER

To prepare the HMWA paper, a strip of quantitative filter paper was treated with dilute nitric acid to remove traces of impurities, washed with deionized water and dried at room temperature. The paper was immersed in a 10% carbon tetrachloridc solution of Amberlite LA-I in the chloride form. ,After ,+,few, h, the,p&er, was dried ir: .’ _’

.&@.

‘.

’

‘,

C+im,.‘&la, 27 (rg62),,373-37t

M. FUJIMOTO,

376

Y.

NAKATSUKASA

air, cut into pieces of 3 x 3 mm (LA-I paper), and kept in the dark in a well-stoppcrecl bottle. This paper was used in a modification of the resin spot test for cobalt(I1) as follows. On a white spot plate, a drop of the slightly acidic test solution was mixed with a drop of 2 I; ammonium thiocyanate and a small piece of the LA-I paper. In the presence of cobalt(I1) a sky blue colour appeared at the eclge of the paper and gradually covered the whole. The limit of identification was found to be 0.2 ,q cobalt(H) per 0.04 ml (I : z *ION)'"" after IO min; this is the same value as that found in the above-mentioned test with HnxwA or in the resin spot test after I h. The wide utility of HMWA papers as reaction media for micro tests is thus clear. ACKNOWLEDGEMENT

The authors espress their gratitude for the supply of Ambcrlite LA-I.

to Nippon

Organo

Shokai,

Ltcl., Tokyo,

Japan,

SUMMARY

resin spot test is moclificcl by the use of a high molecular weight nminc, Ambcrlitc LA-r, in carbon tctrachloriclc; 0.2 /.dgof colxdt(Il) can lx dctcctctl rapidly by shaking an acidic solution containing thiocynnntc with u 5’/” amine solution. Anlinc-imprcgnatccl papers can also bc used.

Tlic

r,cs autcurs proposcnt unc duction scnsiblc pcrmcttant dc cldcclcr facilcmcnt 0.2 pug dc cobalt, cn utilisant Ic thiocyanatc cl’nmmonium comma: r6actif. ct unc nminc fr poids moldculi~irc &cvO, l’ambcrlitc LA-r, cn solution dnns lc tltrachlorurc clc carboric. Ccttc rdaction pcut SC firirc sur un papicr imprdgnd cl’ambcrlitc LA- I , %USAMMENL:ASSUNG l3cschrcibung cincr Motlifikation clcr ‘I’iipfclprobcn mit A~lst;iuuchcrliar~~n clurch Vcrwcnclung l~ocllr~lolclcuiarcr Amine (Ambcrlit LA-r). Als I3cispicl wird clcr Nachwcis von Kobnlt mit Thiocyrrnat bcschricbcn. Der Nachwcis kann such Papiercllromntograltlisch crfolgcn. 1IISl‘;ERENCIIS ’ l’Al1T XX: M. z M. FUJIMOTO,

NAKATSUKASA, A md. C/rim. Acfrc, 27 (r@_iz) 283. Clrerrlisl-A?rcclysf, ‘19 (rgGo) .+. ;a &I. J?uJxMo*ro, Bdt. C%??N. sot. Jrcpnrt, 27 (1954) 48, 4 M. F'UJIMOT,O, LhZ1. Ciaw~. Sot. Japuu, 29 (1956) 600. 0 M. FUJIMOTO, Blrll. Chcm. Sm. Juprt, 29 (1956) 285. U M. FUJIMOTO, Abslvrrcls 4llr A wrutrl AZcelit~g OH Ike Chrrislvy of Co-ovdiuuliorr Tokyo, rps+, w.3-5. 7 M. ZIICGLER AND 0. GLE~ISI~, %. urtnl. Clle~r., 152 (1956). 2.11. 8 I3. SANSONI, Naf~~vwisse~ascir~~f~c/lor. 4G (1959) 228. 0 I<. A. I
ANU

Y.

flrint.

Cliim.

flclu,

Con~~our~ds,

27 (rgG2)

373-376