• Nenhum resultado encontrado

ASSOCIATION OF THE METHODS OF A C T I V A T I O N ANALYSIS AND ISOTOPE DILUTION FOR THE DE-

N/A
N/A
Protected

Academic year: 2021

Share "ASSOCIATION OF THE METHODS OF A C T I V A T I O N ANALYSIS AND ISOTOPE DILUTION FOR THE DE-"

Copied!
12
0
0

Texto

(1)

ASSOCIATION OF THE METHODS OF A C T I V A T I O N ANALYSIS AND ISOTOPE DILUTION FOR THE DE-

TERMINATION OF COPPER IN CHEMICAL REAGENTS

F. W. LIMA, L. T. AT ALLA

PUBLICAÇÃO IEA N.°

Maio — 1970

INSTITUTO DE ENERGIA ATÔMICA Caixa Postal 11049 (Pinheiros)

CIDADE UNIVERSITÁRIA "ARMANDO DE SALLES OLIVEIRA"

SÃO PAULO — BRASIL

(2)

ASSOCIATION OF THE METHODS OF ACTIVATION ANALYSIS AND ISOTOPE DILUTION FOR THE DETERMINATION OF COPPER IN

CHEMICAL R E A G E N T S ^

F.W. Lima, L.T. Atalla

Divisão de Radioquimica Instituto de Energia Atômica

São Paulo - Brasil

Publicação IEA N9 206 Maio - 1970

(3)

Comissão Nacional de Energia Nuclear

Presidente: Prof.Dr. Hervásio Guimarães de Carvalho

Universidade de São Paulo Reitor: Prof.Dr, Miguel Reale

Instituto de Energia Atômica

Diretor: Prof.Dr. Rómulo Ribeiro Pieron.i

Conselho Técnico-Científico do IEA

Prof.Dr,, José Moura Gonçalves ) Prof.Dr. José Augusto Martins ) pela USP Prof.Dr. Rui Ribeiro Franco ) Prof.Dr. Theodoreto H.I. de Arruda Souto ) pela CNEN

Divisões Didatico-Cientificas Divisão de Física Nuclear -

Chefe: Prof.Dr. José Goldenberg Divisão de Radioquímica -

Chefe: Prof.Dr. Fausto Walter de Lima Divisão de Radiobiologia -

Chefe: Prof.Dr. Rómulo Ribeiro Pieroni 'Divisão de Metalurgia Nuclear -

Chefe: Prof.Dr. Tharcísio D.S. Santos Divisão de Engenharia Química -

Chefe: Lie. Alcídio Abrão Divisão de Engenharia Nuclear -

Chefe: Eng? Pedro Bento de Camargo Divisão de Operação e Manutenção de Reatore

Chefe: Eng9 Azor Camargo Penteado Filho Divisão de Física de Reatores -

Chefe: Prof.Dr. Paulo Saraiva de Toledo Divisão de Ensino e Formação -

Chefe: Prof.Dr. Rui Ribeiro Franco

(4)

RADIOCHEM.RADIOANAL.LETTERS 3 / 1 / 23-30 / 1 9 7 0 /

ASSOCIATION OF THE METHODS OF ACTIVATION ANALYSIS AND ISOTOPE DILUTION FOR THE DETERMINATION OF COPPER IN

CHEMICAL REAGENTS F.H.Lima, L . T . A t a l l a

R a d i o c h e m i s t r y D i v i s i o n , I n s t i t u t o de E n e r g i a Atomica Sao P a u l o , B r a z i l

Received 5 December 1969 Accepted 17 December 1969

S e n s i t i v i t y of i s o t o p e d i l u t i o n a n a l y s i s i s l i m i t e d by t h e method u s e d f o r d e t e r m i n a t i o n of t h e r e c o v e r e d mass of t h e l a b e l l e d e l e m e n t added a s t r a c e r / g r a v i m e t r y , f o r i n s t a n c e / . D e t e r m i n a t i o n of t h i s mass by a c t i v a t i o n a n a l y s i s i n c r e a s ­ e s s e n s i t i v i t y of i s o t o p e d i l u t i o n . T h i s method i s a p p l i e d t o t h e a n a l y s i s f o r c o p p e r , a t ppb l e v e l , i n a n a l y t i c a l g r a d e r e a g e n t s .

INTRODUCTION

A c t i v a t i o n a n a l y s i s o f r e a g e n t s f a c e s some p r o b l e m s t h a t o t h e r t e c h n i q u e s may i g n o r e . The i m p o r t a n c e of t h e s e p r o b l e m s has a l r e a d y b e e n s t r e s s e d by Becker and S m i t h1. I n g e n e r a l ,

t h e s e r e a g e n t s a r e c o r r o s i v e l i q u i d s r e q u i r i n g s p e c i a l c a r e f o r i r r a d i a t i o n . Some of them may be decomposed by r a d i o l y s i s form­

i n g g a s e s w i t h a c o n s e q u e n t b u i l d - u p o f p r e s s u r e , which may cause r u p t u r e of i r r a d i a t i o n c a p s u l e s o r s p i l l a g e of i r r a d i a t e d l i q u i d s on o p e n i n g t h e i r r a d i a t i o n c o n t a i n e r . E f f e c t s o f n u c l e a r bombardment, such a s n u c l e a r r e c o i l and y-heating, may enhance

t h e i n t r o d u c t i o n of c o n t a m i n a t i o n from t h e c o n t a i n e r i n t o t h e r e a g e n t samples and may i n c r e a s e t h e r a t e of exchange of i m p u r i ­ t i e s between sample and c o n t a i n e r .

The number of p a p e r s on t h e d e t e r m i n a t i o n of t r a c e e l e ­ ments i n r e a g e n t s , by a c t i v a t i o n a n a l y s i s , i s n o t l a r g e , p r o b a b -

(5)

LIMA, ATALLA: ASSOCIATION OF THE METHODS

24

ly because of the difficulties mentioned. Allina and Otwinowski have determined, by activation, copper in reagents by evaporat­

ing about 10 ml of reagent and irradiating the residue;: the sen- _4

sitivity of the method is reported as being 10 ug. Jaskólska -3 -3 et al. reported a sensitivity of 10 yg for the analysis of copper in hydrochloric acid, nitric acid and hydrogen peroxide.

A method that would keep the characteristic sensitivity of activation analysis, without the problems mentioned in connect­

ion with direct irradiation of those special samples, might be a good alternative for activation analysis. Isotope dilution, followed by activation analysis of the recovered element to be determined;' may comply with the requirement of high sensitivity

4

inherent in direct activation. Pauly et al. were the first to use the association of these two techniques for the analysis of certain elements in a uranium alloy. »

In the present paper this method is applied to the deter­

mination of copper in analytical grade hydrochloric acid, nitric acid, ammonium hydroxide and ammonium sulphide solutions.

EXPERIMENTAL

For the analysis of ammonium sulphide solution a volume of 20 to 40 m l o f the reagent is treated with lead acetate solution /5 mg Pb/ml/ and 2 ml of copper tracer solution /l mg CuO irra-

1 3 - 2 -1

diated in a thermal neutron flux of 10 ~ ncm sec for 8 hours;

the oxidé is dissolved in nitric and hydrochloric acids and di­

luted to obtain 0.03 ug/ml of labelled copper/. The precipitat-

K The content of copper in the solid lead acetate can be deter­

mined by direct activation.

2

(6)

LIMA, ATALLAi ASSOCIATION OF THE METHODS

ed lead sulphide, carrying copper with it, is aged for 30 min.

and filtered under vacuum using a chimney funnel glass apparatus.

The precipitate is washed three times with 2 ml of water each time /deminerilized water then distilled twice in a quartz appa­

ratus/, dried under infra-red heat, placed in polyethylene en­

velopes and counted a t t h e photopeak of 0.51 MeV, in a 400-chan- nel ^-spectrometer coupled to a 3" x 3" well type Nal/Tl/ scin­

tillator, giving B cpm. The same volume of tracer solution which was added to the reagent to be analysed is counted at this time giving A cpm; the chemical yield is r = B/A.

In order to determine the amount of copper that was co- -precipitated with the lead sulphide, this last precipitate is irradiated for one hour in a thermal neutron flux of about

12 -2 -1

10 ncm sec ; a standard of copper is also simultaneously ir­

radiated. After irradiation, 20 mg of copper carrier /nitrate/

are added to sample and standard which are then treated with 2 ml of concentrated sulphuric acid and enough nitric acid to destroy organic matter from the filter paper. 20 ml of water and 0.5 ml of ferric chloride solution /10 mg Fe/ml/ are added

and the ferric ion is precipitated with ammonium hydroxide. The ferric hydroxide scavenger is filtered. Recovery of copper in the filtrate is over 99%. To the filtrate 2 ml of zinc chloride solution /10 mg Zn/ml/ is added and zinc and copper are preci­

pitated with ammonium sulphide. The precipitate is filtered, washed with a hot 1:20 hydrochloric acid solution and counted at

the peak of 0.51 MeV giving B. cpm.

(7)

LIMA, ATALLA: ASSOCIATION OF THE METHODS

The amount x of copper is calculated by the following ex­

pression, derived from the classical formula for isotope dilut­

i o n5

x

= (

B

i -

B

t K / v

in which is the remaining activity of the added copper tracer and which can be determined by counting an aliquot of the ori­

ginal copper tracer solution; M and A are the mass and activi- s s

ty of the copper standard irradiated together with the lead sul­

phide .

The analysis for ammonium hydroxide is performed similar­

ly; the amount of copper found in the ammonium sulphide is sub­

tracted from the copper found in the ammonium hydroxide.

For the analysis of hydrochloric and nitric acids, copper tracer is added to known volumes of these reagents which are gently heated tb dryness. Concentrated ammonium hydroxide is added up to alkaline reaction, followed by the lead acetate so­

lution, and lead is precipitated with 1 ml of the ammonium sul­

phide solution. From there on, the chemical procedure is carried out as in the analysis of ammonium hydroxide and ammonium sul­

phide solutions. The amounts of copper previously found in these two reagents are subtracted from the amounts found in

the chemicals being analysed, i.e. hydrochloric and nitric acids.

RESULTS

Results are presented in Tables 1 to 4.

26

(8)

LIMA, AT ALLA: ASSOCIATION OF THE METHODS

TABLE 1

Copper in analytical grade hydrochloric acid Sample Volume, Cu

ml pg ppb

1 25 0.286 9.61

2 40 0.550 11.55

3 40 0.501 10.52

4 25 0.198 6.64

5 25 0.254 8.55

6 40 0.684 14.38

7 40 0.836 13.36

8 40 0.490 10.29

9 40 0.358 7.52

= 10.3, a* = 2.6, s *x = 0.9 m

x Standard deviation of a single result

^Standard deviation of mean.

TABLE 2

Copper in analytical grade nitric acid Sample Volume Cu

ml yg ppb 1 40 0.720 12.85 2 40 0.490 8.75 3 40 0.518 9.25 4 40 0.572 10.21 5 25 0.327 9.34 6 25 0.303 8.66

9.8, sx = 1.6, s„ = 0 . 7 m

(9)

LIMA, ATAIAA: ASSOCIATION OF THE METHODS

TABLE 3

Copper in analytical grade ammonium hydroxide

Sample Volume, Cu

ml y g ppb 1 25 0.217 9.54 2 40 0.361 9.91 3 40 0.364 10.00 4 40 0.288 7.92 5 40 0.306 8.40

9.1, Sx = 0.7, sm = 0.3

TABLE 4

Copper in analytical grade ammonium sulphide solution Sample Volume,

ml

Cu

vg ppb

1 40 0.491 12.27

2 40 0.532 13.30

3 40 0.518 12.95

4 40 0.628 15.70

x = 13.6, sx = 1.6, sm = 0.8

DISCUSSION

The accuracy and precision of the method have been dis­

cussed in another p a p e r6 in which copper was determined in gold samples. In the present paper it is seen that the method can be applied equally well for very low quantities of copper in analyt­

ical grade reagents.

28

(10)

LIMA, AT ALL A: ASSOCIATION OF THE METHODS

.,. Volumes of samples were of the order of 20 to 40 ml-but it can be seen that volumes of 10 ml could be used since the amount of copper would be of the order of 0.1 v g , which is a mass that can be easily determined by this method. Direct activation, in the case of some reagents, have been applied by Allina and Ot- winowski using 10 ml samples, but submitting the sample to an evaporation procedure before.irradiation. At such low concentrat­

ion levels, corresponding to one to ten parts per billion, eva­

poration may lead to a loss of some elements. In the present paper evaporation of the reagents, when necessary, was carried out after the labelled copper solution had been added in order to carry the isotope dilution method. This will increase the to­

tal copper concentration avoiding possible losses by volatilizat­

ion or by adsorption in the glass ware. Besides, isotope dilut­

ion method corrects for losses of the element being analysed.

Results presented in Tables 1 to 4 show that even at this sub-trace level the precision, as indicated by the standard de­

viations, is very good.

An inconvenience of the method, compared with direct acti­

vation analysis, is that the time spent for one set of analyses is longer than for classical activation analysis. However, the advantages gained in avoiding irradiation of dangerous liquids compensate for this longer time for analysis of these particular types of samples.

It is interesting to note that an analysis of a nitric acid with the same trade mark as that whose results are report­

ed in Table 2, but taken from a bottle for general use in the laboratory, gave results corresponding to 235 and 223 parts per

(11)

LINA, AT ALLA: ASSOCIATION OF THE METHODS

billion in copper, showing how easily reagents become contamin­

ated when no special handling care is adopted.

REFERENCES

1. D.A.Becker, G.W.Smith, NBS Technical Notes 427, November 1967.

2. Z.Allina, W.Otwinowski, Nukleonlka, 10 /1965/ Suppl. 93-9.

3. H.Jaskolska, L.Wodkievicz, J.Minczewski, chem.Anal. /Warsaw/

9, /1964/ 459.

4. J.Pauly, E.Sabbioni, F.Girardi, Proc.Symp.Radiochemical Methods of Analysis, Salzburg, 19-23 October, IAEA, Vienna, 1965.

5. F.W.Lima, C.M.Silva, J.Radioanal.Chem., /in the press/.

6. F.W.Lima, L.T.Atalla, Proc.ANL Topical Meeting on Isotope Utilization in Latin American Development, held in San Juan, Puerto Rico, May 4-6, 1969. To appear in March, 1970.

30

(12)

SUMARIO

Em análise por diluição isotópica a sensibilidade fica limitada pelo método adotado para a determinação da massa recuperada do material marcado (gravimetria, p . ex„)„ A determinação daquela massa por ativação aumenta a sensibilidade do método^de diluição isotópica. No presente trabalho determina-se, pela associação dos dois meto dos, cobre presente em reagentes analíticos e no nível de partes por bilhão.

Referências

Documentos relacionados

Adsorption tests for the removal of lead ions were conducted by mixing 0.1 g activated carbon with 20 mL of a solution of known concentration (50–500 mg L -l at pH 7) in 250

The probability of attending school four our group of interest in this region increased by 6.5 percentage points after the expansion of the Bolsa Família program in 2007 and

Maximum concentrations of the protein used for SAXS solution studies of the hRXR ␣ dimer (3.1 mg/ml) and the hRXR ␣ tetramer (14 mg/ml) limited the maximum resolution of the

Investigar a presença de HPVs de alto risco em amostras de DNA de mucosa oral de indivíduos saudáveis fumantes e não fumantes e de pacientes com carcinoma espinocelular de cabeça

The soft extract solution sample for HPLC analysis was prepared.. by dissolving 300 mg in 5 ml of methanol, in a 10

The iterative methods: Jacobi, Gauss-Seidel and SOR methods were incorporated into the acceleration scheme (Chebyshev extrapolation, Residual smoothing, Accelerated

social assistance. The protection of jobs within some enterprises, cooperatives, forms of economical associations, constitute an efficient social policy, totally different from

Isso acontece porque o Parque Ambiental é o lugar escolhido pela Fundação Municipal de Cultura de Ponta Grossa para sediar os eventos musicais Sexta às Seis e