Multi-element atomic fluorescence spectroscopy

Andyricu Elscvier

474

Publishing

Company.

Printed

Multi-element

atomic

fluorescence

Chlmlcu Acru Amsterdam

in The Nelhcrtands

spectroscopy

Part V. The determination of chromium and manganese in steels acetylene flame with a dual-element electrodeless discharge lamp

in a separated

air-

In Part IV of this scrics’, the determination of cobalt and nickel in steels by atomic fluorescence spectroscopy in a separated air-acetylene flame, with a dualelement electrodeless discharge lamp, was described. In this communication, a similar method is reported for the determination of chromium and manganese in steels. Experirnerml The apparatus and operating conditions were as described previously’. The electrodeless discharge lamps were prepared in the usual mannerrS2, filled with cu. 1 mg of A.R. grade chromium(IlL) chloride, cu. 1 mg of A.R. grade manganese(l1) chloride, and pressurized at 4 torr with argon. For steels containing CII.OS’;/, chromium and/or manganese, 0.02 g of the steel was weighed out. The preparation of a cu. 1 p.p.m. solution was similar to that described previously for cobalt and nickel l. For steels of different chromium and/or manganese contents, proportionate weights were taken. Owing to the depressing matrix effect of iron, it was necessary to remove most of the iron from steel samples containing less than 0.5 ‘x, chromium ; this was achieved by extracting the iron from the strong hydrochloric acid-nitric acid solution immediately after dissolution’, with an equal volume of A.R. grade amyl acetate. One such extraction removed 60 ‘x, of the iron present; depending on the sample taken, one or more extractions were used as necessary. R-e-equilibration of the amyl acetate with 11 M hydrochloric acid increased the efficiency of the iron(II1) extraction to 95’%,,. The preparation of calibration solutions (O-2 p.p.m. range) was carried out by diluting 100-p.p.m. stock solutions (0.5 123 g A.R. grade chromium chloride in 1 dm3 of distilled water and 0.3566 gA.R. grade manganese chloride in 1 dm3 distilled water) as described previously’. Results

trrul discrtssiort

The electrodeless discharge lamps were an intense blue in colour and showed the main spectral lines of chromium and manganese. The chromium 357.9-nm and 359.4-nm, and the manganese 279.8~run resonance lines were of approximately equal intensity. The optimal incident power for the operation of these lamps was 60 W. The stabilities over a period of 1 h were then within +3 0/Ofor all the lamps used in this work at 359.4 nm and 279.8 nm. After the initial running-in period, a warm-up time of CCL10 min was required when the discharge was initiated from the cold. The effects of 250-fold amounts (by weight) of 38 ions on the atomic fluorescence of 2 p,p.m. chromium3, and of lOOO-fold amounts of 26 ions on the atomic fluorescence of 0.5 p.p.m. manganese4 have recently been investigated. The only interferences observed were due to refractory metals, none o,f which was present at sign’ificant levels in the steels under investigation. Anal.Chink Actu, 59 (1972)

’

475

SHORT COMMUNICATIONS TABLE

I

DETERMINATION

OF CHROMIUM -

AND IblANGANESIi --__.--

IN STEELS

--

Chtorniunr

Smtple

--__--_

---

Manguncsc

_._--.__

_-----__.-__

A./k.

Certijicatc valrre

A.j:s.

B.C.S. B.C.!% B.C.!% B.C.!% B.C.S. B.C.S. B.C.!% B.C.S. B.C.S. B.C.S. _--_-.--

225 Ni--Cr-Mo steel 225/2 Ni-Cr-Mo steel 273 Mild steel 277 Mild steel 328 Mild steel 334 Austcnitic stainless steel 341 Fcrritic stainless steel 406 Low-alloy steel 407 Low-alloy steel 483 High-speed steel _.___-_..____

TABLE

II

RANGES

AND

MANGANESSB

-_.--__-._.

STANDARD

DfS’IATIONS

1.04

1 .os I .08 0.04 0.07

I .08 0.03 0.075

25.5 23.7 2.1 I 3.00 3.18

25.6 24.0 2.12 3.00 3.21

0.60 0.56 0.50 0.49 0.44 0.84 0.42 0.53 0.13 0.29 --- __.-

0.595

0.56 0.50 0.49 0.43 0.85 0.43 0.53 0.13 0.29

_-_.

FOR THE ATOMIC

FLUORI:SCiINCE

DETl!RMINATIDN

-____--..----_-_-

--

01: CHROMIUM

AND

IN STEEL

(B.C.% 406) -_____ _.._..-__----

__-._-~

Certilicate value Mcun value of atomic fluorcsccncc analysis Range in certificate value Range by a.f.s. Standard deviation (2;) by a.f.s. -.-----_--__-

--

--.---

Clrror~tiuri~

McIIlgunesc’

2.12 2.1 I 2.08-Z 15 2.04-2. I 8 2.5 ________

0.53 0.531 0.53--0.54 0.525-0.538 1.8 __-._ --_

The effect of a 2500-fold amount of manganese on 2 p.p,m. chromium and of a 2500-fold amount ofchromium on 2 p.p.m. manganese were investigated, and no interference was found. Examination of the effect of larger amounts of the matrix element (iron) showed that iron above a 250-fold amount interfered in the determination of chromium. Hence, for steels containing less than OSO/”chromium, a preliminary solvent extraction was used to remove the bulk of the iron. The results obtained for the determination of chromium and manganese in a variety of standard steels from the B.C.S. range (Bureau of Analysed Samples Ltd., Middlesborough) are given in Table I. One sample of each steel was weighed and dissolved, and four atomic fluorescence readings were taken and averaged to obtain these results. The precision of the method was investigated for one of the standard steels (B.C.S. 406 Low alloy steel). Seven samples of this steel were weighed and dissolved. Four atomic fluorescence readings were taken and averaged for each of these samples to obtain the results from which the ranges and standard deviations were calculated. These data are given in Table II. Anal.Chim.

Ado,

59 (1972)

476

SHORT COMMUNICATIONS

We arc grateful to the S.R.C. for the award of a grant to one of us (J.D.N.) and to Mr. I3. Bagshawe of Firth Brown Research Laboratories, Sheffield, for providing several of the samples. We also thank Southern Analytical Ltd. for the loan of the spectrophotometer. Deprtment of Citemistry, Imperial College of Science and Technology, Lonckon S W7 2A Y (Eqlud)

I J. D. NORIZIS AND T. S. WET, Arrd. Cltitn. Ada, 55 (1971) 359. 2 R. M. DAGNALL AND T. S. WEST, Appl. Opt., 7 (1968) 1287. 3 J. D. NOHHIS AND T. S. WEST. Anal. Cltim. Ada, 59 (1972) 355. 4 I_. EISDON. (3. F. KIRKIIIUGI-IT AND T. S. WEST, TU/N~IIN.17 (1970) 965.

(Received 2nd November Anal. Chitn. Acts, 59 (1972)

1971)

J. D. Norris T. S. West