compaq presario 4540

第 22 卷
第3期
2003 年
5月
环 境 化 学
ENVIRONMENTAL CHEMISTRY
Vol. 22, No. 3
May
2003
FLOW INJECTION ON LINE SEPARATION AND
SPECTROPHOTOMETRIC DETERMINATION OF TRACES
OF LEAD IN ENVIRONMENTAL SAMPLES
TOMIOKA Kenichi
OGUMA Koichi
( Faculty of Engineering, Chiba University, Yayoi cho, Inage ku, Chiba 263 8522, Japan)
SEKI T atsuya
( Chemical Research Laboratories, Nissan Chemical Industries, Ltd, Tsuboi cho, Funabashi 274 8507, Japan)
Abstract A flow injection method has been developed for the determination of lead in environmental
samples by use of on line preconcentration on a Pb SpecTM column and spectrophotometric detection. The
lead in sample solutions was adsorbed selectively on the column from 1mol l- 1 nitric acid and the retained
lead was eluted with 0 1mol l- 1 ammonium oxalate. 4 ( 2 pyridylazo) resorcinol ( PAR) was used as a
chromogenic reagent at pH 10 and the absorbance of Pb PAR complex was monitored at 530 nm. The
pumps, valves and spectrophotometer were controlled by a personal computer. The detection limit ( 3 )
was 3ng of lead. The RSD is 1 7% at a level of 0 4 g lead. The proposed method was successfully ap
plied to the determination of lead in fly ash of an incinerator for industrial waste and in river water certified
reference material provided by the Japan Society for Analytical Chemistry .
Keywords flow injection analysis, lead, environmental samples, on line preconcentration.
1
Introduction
Lead is well known as one of the most toxic metals and noted in the f ield of environmental
chemistry [ 1] . The lead concentrat ion in natural water is extremely low ( sub g l- 1 level ) so that
some preconcentration step must be included to assure the sensit ivity of a convent ional instrument
employed in the f inal measurement step of analysis. Furthermore, the blank value introduced from
the reagents or from the laboratory environment must be kept at as low level as possible in order to
obtain the precise analytical results for traces of lead.
Flow injection ( FI) on line preconcentrat ion procedures now play an important role in trace
metal analysis[ 2 6] . The advantages of the combination of FI on line preconcentration with spec
trometry have been reviewed in the previous paper [ 7] .
A lead selective chromatographic resin, Pb SpecTM ( EI Chrom Industries, Inc Darien, IL) ,
has already been applied by the present authors to the analysis of steel[ 7] and water sample[ 8] for lead
by FI flame atomic absorpt ion spectrometry or FI inductively coupled plasma mass spectrometry.
This commercially available resin is Amberchrom CG 71 resin ( Supelco) impregnated with an
isodecanol solution of bis 4, 4 ( 5 ) [ tert butylcyclohexano] 18 crown 6 and exhibits no affinity for
the alkali metal ions and other heavy metal ions[ 9] . This characteristic of the resin has turned out in
this work to be also well suited for the precise determination of traces of lead in fly ash of an incine
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rator for indus trial wastes and in riverwater by FI on line preconcentrat ion coupled with spectro
photometric detect ion.
2
Experimental
2 1 Apparatus
The block diagram of FIA system used for the spectrophotometric determination of lead is shown
in Fig 1.
PTFE tubing ( 1mm i. d. ) was used to construct the manifold. A six way valve, MPV 6A ( GL
Sciences Inc. , Tokyo, Japan) was used for flow switching. An eight way valve, SV 5008A ( GL
Sciences Inc. , Tokyo, Japan) was used to inject sample solution and washing solutions.
Fig. 1 Automated flow injection system for determination of lead
S: Sample; W1: 1mol l- 1nitric acid; W 2: 0 1mol l- 1 ammonium nitrate; A: 0 1mol l- 1 ammonium oxalat e;
B: 0 015% PAR ( pH 10) ; Column: Pb SpecTM column ( 70
2 0 mm i . d. ) ; P1, P2: HPLC pumps; P3: non pulsation
pump; V 1: eight way valve; V2: six way valve; Sp: spectrophotometer with f low cell; PC: personal computer
A valve controller ( Model VC 655, GL Sciences Inc. , Tokyo, Japan) was used to control all
the valves. HPLC pumps, PU 611 ( GL Sciences Inc. , Tokyo, Japan) were used to deliver sample,
washing and 0 015% PAR solutions. A non pulsation pump, PUD 16 ( GL Sciences Inc. , Tokyo,
- 1
Japan) , was used to deliver the eluent ( 0 1mol l ammonium oxalate) . A UV/ VIS detector
(Model UV 620, GL Sciences Inc. , Tokyo, Japan) was equipped with an 8 l flow cell ( 10mm
path length) was used. Data collection and control of the PU 611 pumps, all the valves and the
UV/ VIS detector were performed on a personal computer ( Compaq presario 4540 model, Compaq
Computer Co. , U. S. ) using a data station, V Station version 1 64 ( GL Sciences Inc. , Tokyo,
Japan) .
The preconcentration column was prepared by packing an appropriate amount of Pb SpecTM in
a PTFE tube column ( 70 mm 2 0 mm i. d. ) . Both ends of the column were f ixed with glass filter
and cotton wool.
2 2 Procedure of FIA
TM
The Pb Spec
column was conditioned with 1mol l
- 1
- 1
nitric acid ( 4 ml min
The sample solution was then passed through the column at a flow rate of 4 ml min
on the column. After the column was washed first with 1mol l
- 1
) for 0 5 min.
-1
to adsorb lead
- 1
nitric acid ( 4 ml min ) for 1min
3期
Tomioka Kenichi et al. , 环境样品中痕量铅的流动注 射在线分离及分光光度检测
213
and then with 0 1mol l- 1 ammonium nitrate solution ( 4ml min- 1 ) for 1 min, the lead adsorbed on
- 1
- 1
the column was eluted by passing 0 1mol l ammonium oxalate solution ( 2 ml min ) through the
column from the opposite direction of the sample solut ions for 3 min. The lead eluted was mixed with
0 015% PAR and introduced to the spectrophotometer. The peak height was used for quantifica
tion. The calibrat ion curve was prepared by injecting known amounts ( 0 05 3 0 g) of lead as
- 1
1mol l nitric acid solut ion into the FIA system.
2 3 Analysis of ash
About 2g of ash was taken and decomposed with 10ml of nitric acid and 20ml of hydrochloric
acid by gent le heating. After evaporation nearly to dryness, the residue was treated with 10ml each
of nitric acid by heat ing several times. 0 5ml of 30% hydrogen peroxide was added to decompose
organic compounds. After evaporation nearly to dryness, the residue was treated with 10ml each of
nitric acid by heating a few times. The residue was taken up in 1mol l- 1 nitric acid and the sample
- 1
solution was filtered with a filter paper ( No 5B) , followed by its dilution to 100 ml with 1mol l
nitric acid. 4 ml of the appropriately diluted sample solution was injected into the flow injection
system.
5ml aliquot of the diluted sample solut ion was taken and treated with hydrofluoric acid, fol
lowed by evaporation to dryness. The residue was taken up to 100ml of 1mol l
which 2ml solut ion was injected into flow inject ion system.
-1
nitric acid, of
2 4 Analysis of river water
10 ml of sample solution ( JAC 0032, metal added) was taken and 0 7ml of nitric acid was
added. The sample solution was boiled for 10min moderately. After cooling, the sample solution was
adjusted to 25ml of 1 mol l- 1 nitric acid. 20ml of the solut ion was injected into the flow injection
system.
3
Results and discussion
Pb SpecTM shows high selectivity to lead in 1mol l- 1 nitric acid ( k = ca. 1000) . Horwitz
et al. showed other metal ions, stront ium ( ) and thallium ( ) to have k of ca. 20. Sodium
( ) , potassium ( ) and calcium ( ) show no adsorpt ion on the Pb SpecTM[ 9] . The most effec
tive eluent for Pb (
) found by Horwitz et al. was EDTA, but it was not used in the present work
because Pb EDTA complex was so stable that Pb PAR complex was not formed. Therefore, ammo
nium oxalate solution was used as an eluent. Oxalate ion did not interfere with the formation
of Pb ( ) PAR complex.
Table 1 shows the analytical results obtained for fly ash. The values obtained without hydro
fluoric acid treatment are lower than those obtained after hydrofluoric acid treatment. This is proba
bly because some portion of lead is present as chemical species containing silicone, which is not
adsorbed on the Pb SpecTM column, when the fly ash sample is not treated with hydrofluoric acid.
The values obtained for river water certified reference material JAC 0032 are in good agreement
with the certified value as shown in T able 2. The reproducibility is also excellent.
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Table 1 Analytical results of lead in fly ash ( unit: % )
FAAS
ICP AES
The present method
Sample
Standard addition method
St andard addit ion method
Without HF treatment
With HF treatment
A
0 406
0 538
0 313
0 401
B
0 434
0 407
0 285
0 425
C
0 388
0 485
0 283
M ean
SD
0 409
0 023
0 477
0 066
0 294
0 423
0 017
0 416
0 014
Table 2 Determination of lead in river water certified reference material*
Injection volume/ ml
20
20
20
20
Pb found/ ng
83
76
77
78
83
10 4
9 5
9 7
9 7
10 3
Content in original sample/ ng ml- 1*
*
Certified value/ ng ml- 1
20
9 9 0 2
* River water cert if ied reference material JAC 0032 ( metal added) provided by the Japan Society for Analyt ical Chemistry.
* * M ean
standard deviation: 9 9
0 4.
The relat ive standard deviations are 0 4% at 1 g Pb level ( n= 3) , 1 7% at 0 4 g Pb level
( n= 3) and 3 0% at 0 05 g Pb level ( n= 3) . The detection limit equivalent to 3 of the back
- 1
ground signal is 3ng Pb, so that the detection limit in concentration is 0 3 ng Pb mol when 10 ml
of a sample solution is injected to the proposed analytical system. The sample throughput is 9 per
hour when 4ml of the sample solution is injected.
References
[ 1]
Manahan S E, Environmental Chemistry. 6th Ed. , CRC Press, Boca Raton, 1994, Chap. 7
[ 2]
Valcarcel M, Luque de Castro M D, Non Chromatographic Cont inuous Separation Technique. The Royal Society of Chemistry,
Cambridge, 1991
[ 3]
Fang Z, Flow Injection Separat ion and Preconcentration. VCH, Weinheim, 1993
[ 4]
Burguera J L ( ed. ) , Flow Injection Atomic Spectroscopy. M arcel Dekker, New York, 1989
[ 5]
Fang Z, Xu S, Tao G, Development s and Trends in Flow Inject ion Atomic Absorpt ion Spectrometry. J. Anal . Atom . Spec
trom. , 1996, 11 1
[ 6]
24
Luque de Castro M D, Gamiz Gracia L, Recent Development s in Flow Inject ion Atomic Spectrometry. Ad . At om . Spec
trosc . , 1998, 4 177 212
[ 7]
Seki T, Takigawa H, Hirano Y et al . , On Line Preconcentration and Det ermination of Lead in Iron and Steel by Flow Injec
tion flame Atomic Absorption Spectrometry. Anal . Sci . , 2000, 16 513
[ 8]
516
Seki T, Hirano Y , Oguma K , On Line Preconcentration and Determination of Traces of Lead in R iver Water and Seawat er by
Folw Injection flame Atomic Absorption Spectrometry and ICP Mass Spectrometry. Anal . Sci . , 2002, 18 351
[ 9]
354
Horwit z E P, Dietz D L, Rhoads S et al. , A Lead Select ive Extraction Chromatographic Resin and Its Applicat ion to the Iso
lat ion of Lead from Geological Samples. Anal . Chim. Acta, 1994, 292 263
273
环境样品中痕量铅的流动注射在线分离及分光光度检测
TOMIOKA Kenichi, OGUMA Koichi; SEKI Tatsuya
日本千叶大学工业部, 千叶 263 8522, 日本; 尼桑化学工业有限公司化学研究实验室, 船桥 274 8507, 日本