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Prediction of FIA peak width for a flow-injection manifold with spectrophotometric or ICP detection
Talanta, Vol. 36,No.9,pp. 969-912, 1989 Printed in Great Britain. All rights -cd
0039-9140/89 $3.00 + 0.00
Copyright0 1989 Pqamon Press plc
ANNOTATION
PREDICTION OF FIA PEAK WIDTH FOR A FLOW-INJECTION MANIFOLD WITH SPECTROPHOTOMETRIC OR ICP DETECTION PHILLIP LYLEKEMPSTER and HENK ROBERTVANVLIET Hydrological Research Institute, Department of Water Affairs, private Bag X313, Pretoria, South Africa
JACOBUSFREDRRICKVANSTADEN Department of Chemistry, University of Pretoria, Pretoria, South Africa (Received 21 December 1988. Accepted 31 March 1989)
Slmun;uy-Equations are proposed for predicting the width of a FIA peak when a sample injection volume of 300 ~1 is used. The equations for both spectrophotometric and inductively coupled plasma emission spectrometric detection are similar.
dissolving 0.1596 g of anhydrous copper sulphate and 5.35 g of ammonium chloride in 500 ml of demineralized water, adding 8 ml of 13M ammonia solution, and making up with water to 1 litre. Two blank solutions, corresponding to stock solutions A and B and containing ammonium chloride and ammonia, but not the copper sulphate, were also prepared, to serve as carrier and wash solutions.
In FIA thedry, expressions for peak width, such as baseline-to-baseline time, are of practical value in the design of FIA manifolds, for automated analysis of environmental water samples, for example. Vanderslice et al.’ provided an expression for baseline-to-baseline time from numerical integration of the diffusion-convection equation. Gbmez-Nieto et al.* developed an experimental approach for determining an expression for baseline peak-width and the present paper essentially describes an extension of that work. Vanderslice et al.’ took the sample injection volume as 2 ~1, while Gbmez-Nieto et al.* used a sample injection volume of 30 ~1. In the analysis of water samples by FIA methods, sample injection volumes in excess of 200 ~1 may be required3*’ in order to obtain sufficient sensitivity. Our aim was to develop an expression for peak width at half, one-third, one-tenth and one-fiftieth peak height, as well as baseline peak width, by using the experimental approach suggested by GbmezNieto et al.2 but for a 300-~1 injected sample volume. , A simple FIA configuration was used with either spectrophotometric or inductively coupled plasma (ICP) emission spectrometric detection of the analyte, which was the diaquatetra-aminecopper(I1) complex.
EXPERIMENTAL Reagents Analytical grade reagents were used. Copper stock sol-
ution A (O.OlM) was prepared by dissolving 1.596 g of anhydrous copper sulphate and 10.70 g of ammonium chloride in 500 ml of demineralized water, adding 16 ml of 13M ammonia solution and making up with water to 1 litre. Copper stock solution B (O.OOlM) was prepared by
Apparatus The FIA manifold is shown in Fig. 1. Two sets of measurements were made, one with an LKB Novaspec spectrophotometer with a Helhna 178.011-05 flow-cell having a chamber volume of 30 pl and an inlet dead volume of 147 ~1, the other with an ARL 34000 ICP Quantometer fitted with an ll-ml cloud chambezS The carrier solution was propelled with a Gilson Minipuls 2 peristaltic pump. A second Gilson Minipuls 2 pump was used to aspirate the sample/wash solutions from a Cenco 345.17.700 sampler, through the 300-p 1 sampling loops of a Carle 2013 sampling valve. The sampler and sampling valve were activated by a laboratory-made electronic timer. The sample uptake rate was adjusted to 6.3 ml/min. The FIA peak proties were recorded on a Hitachi 056-1002 potentiometric recorder, peaks being recorded in triplicate. Copper stock solution A was used as the sample solution when the spectrophotometer was employed as detector, the wavelength being set at 600 nm; copper stock solution B was used as the sample solution when the ICP spectrometer was employed as detector; the wavelength of the copper channel on the spectrometer was 327.40 nm. The plasma was operated at a radiofrequency power of 1.25 kW. Argon gas flow-rates to the torch were 11.0,0.40 and 0.40 l&in for the outer, intermediate and inner gas flows respe&vely, at a gauge pressure of 340 kPa. The length L and internal diameter d of the tubing betwen the flow injection valve and the deteotor were in the ranges 6240 cm and 0.38-1.19 mm respectively. Carrier flow-rate values, q, between 0.7 and 3.8 ml/min were chosen. As suggested by CSmez-Nieto et al.,2 at least five points were obtained for each variable, with the other two variables kept constant. The baseline width, width at one-ii!&&,
969
970
ANNOTATION
Fig. 1. FIA manifold used for peak-width evaluation.
Table 1. Experimental and calculated data for the FIA manifold in Fig. 1, with spectrophotometric
Q> mllmin
d, mm
2.2 2.6 3.0 3.4 3.8 2.2 2.6 3.0 3.4 3.8 2.2 2.6 3.0 3.4 3.8 2.2 2.6 3.0
1.19 1.19 1.19 1.19 1.19 1.02 1.02 1.02 1.02 1.02 0.86 0.86 0.86 0.86 0.86 0.58 0.58 0.58 0.58 0.58 0.38 0.38 0.38 0.38 0.38 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02
:.;: 212 ::: :.;: 0:7 1.0 1.4 1.8 ;: 3:o 3.4 3.8 :?i 3:o 3.4 3.8 2.2 2.6 3.0 3.4 3.8 2.2 :::
L., m 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 loo.0 100.0 loo.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Z8
Ars, set
At,*, set
Atlo, set
At,, set
At,, set
Ats, set
A‘,, set
At,,, see
*r,, set
Ar,, see
65 64 48
62 59 43 46 38 49 42 38 32 28 45 36
43.6 36.3 32.0 29.9 26.5 39.2 33.5 29.2 24.7 21.6 30.3 25.2 21.2 18.4 15.1 20.3 16.7 14.4 12.3 11.0 17.6 15.1 12.9 11.1 10.0 106.5 82.9 57.6 43.0 34.5 27.2 22.1 18.7 16.6 43.4 37.8 32.3 27.9 24.0 49.1 42.0 36.6 33.2 29.8 59.1 45.8 42 5 44:1 38.6
27.3 22.7 19.6 18.5 15.6 28.4 24.3 21.1 18.1 16.0 18.9 16.8 13.9 11.7 9.5 12.1 10.7 9.1 8.2 6.8 10.5 9.2 8.4
20.1 17.2 14.8 14.2 11.6 23.5 19.8 17.4 14.6 12.7 14.6 12.8 10.7 9.1 7.7 9.5 8.6
70 60 53 47 43 65 56 49 44 40 60 52 46 41 37 51 44 38
64 54 47 41 37 57 48 42 37 33 50 42 37
::; 5.4 8.6 7.4 6.2
:: 42 36 32
:f 55:s 41.2 26.7 21.4 15.5 12.8 10.4 8.8 7.5 20.9 18.3 16.3 14.2 11.9 28.8 24.1 21.2 19.4 17.8 34.8 28.2 25.3 24.8 22.4
:: 157 114 84 67 56 48 43 38 35 61 53 46 41 38 74 64 56 50 46 83 72 63 56 51
31.8 26.3 22.4 19.4 17.1 27.2 22.5 19.1 (6.6 14.6 22.8 18.9 16.1 14.0 12.3 15.3 12.7 10.8 9.4 8.3 10.0 8.3 7.0 6.1 5.4 74.5 49.8 34.0 25.6 20.4 16.9 14.4 12.5 11.0 24.0 19.9 16.9 14.7 12.9 35.3 29.2 24.9 21.6 19.0 44.3 36.7 31.2 27.1 23.9
24.7 20.5 17.4 15.1 13.3 21.2 17.6 14.9 13.0 11.4 17.9 14.8 12.6 11.0 9.7 12.1 10.0 8.5 7.4 6.5 8.0 6.6 5.6
24 71:8 54.5 36.7 28.1 21.2 17.3 14.0 11.6 10.3 28.0 24.7 21.2 18.1 15.2 35.1 29.6 26.1 23.5 21.2 42.9 35.0 32.1 30.1 27.2
47.0 39.1 33.4 29.2 25.8 40.6 33.8 28.9 25.2 22.3 34.5 28.7 24.6 21.4 19.0 23.7 19.8 16.9 14.7 13.0 15.9 13.2 11.3 9.9 8.7 113.1 76.6 53.0 40.2 32.3 26.9 23.0 20.0 17.7 36.7 30.6 26.2 22.8 20.2 50.1 41.7 35.7 31.1 27.5 60.1 50.0 42.8 37.3 33.0
z 51 45 40 33 30 56 44 51 42 34 51 45 45 42 32 40 :: : 159 126 91
ZZ:8 ::8 ::8 60.0 80.0 80.0 80.0 80.0 80.0 160.0 160.0 160.0 160.0 160.0 240.0 240.0 240.0 240.0 240.0
detection
Calculated
Experimental
zl 44 38 ;: 69 60 56 54 47 79 72 64 54 :: :: 64 53
:: 27 37 :: 23 :; ;: 17 17 143 112 81 60 :; 32 ;: 61 54 47 42 36 69 59 52 46 42 78 55 z 51
*A!, = peak width at l/n fraction of peak height above the baseline.
;; :; 27 24 22 t: 20 18 16 153 106 75 58 : 35 30 27 53 44 38 :: 68 57 50 44 39 79 66 57 50 45
z 56:l 37.5 25.6 19.3 15.4 12.7 10.8 :*t: 18:4 15.3 13.0 11.3 9.9 28.5 23.6 20.1 17.4 15.4 36.8 30.4 25.9 22.5 19.8
971
ANNOTATION
one-tenth, one-third and half maximum peak-height were measured from the recorder chart. Recorder response-time was less than 0.1 sec.
equation (l), the equations which were obtained for the manifold described in this paper were: Atx = 35&jo.444L0.28Zq
RFSULTS AND DISCUSSION
Baseline-to-baseline
(2)
detection and
At, = 22J@.~LO.‘67 4 -0.888
Gomez-Nieto et al.’ proposed the equation for baseline-to-baseline times: Atx =
for spectrophotometric
time
-0.893
(3)
following for ICP emission spectrometric detection.
c~j7&293~0.107~1.057
The experimental data, giving the mean of the measured values together with the predicted values, are shown in Table 1 for spectrophotometric detection and in Table 2 for ICP emission spectrometric detection. A difference which is immediately apparent is that the exponent of q is negative in equations (2) and (3) but positive in equation (1). Since perusal of
(1)
where At, is the base width in set, and the units of the diameter d, length L and flow-rate q are mm, cm and ml/min respectively. By following the procedure suggested by Gomez-Nieto et al.’ of performing multiple regressions for the logarithmic form of
Table 2. Experimental and calculated data for FIA manifold in Fig. 1 with ICP emission spectrometric detection Experimental 4. mllmin
d, mm
2.2 2.6 2.9 3.4 3.8 0.7 1.2 2.2 2.9 3.8
1.19 1.19 1.19 1.19
4:: 2.9 3.4 3.8 2.2 2.6 2.9 3.4 3.8 2.2 g 3:4 3.8 0.7 1.2 2.2 2.9 3.8 0.7 1.2 g 3:8 0.7 1.2 22.; 3:8 0.7 1.2
1.19 1.02 1.02 1.02 1.02 1.02 0.86 0.86 0.86 0.86 0.86 0.58 0.58 0.58 0.58 0.58 0.38 0.38 0.38 0.38 0.38 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02
1.02 1.02 1.02 1.02
Calculated
At,,
At,*,
L, cm
set
see
set
loo.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 60.0 60.0 60.0 60.0 60.0 80.0 80.0 80.0 80.0 80.0 160.0 160.0 160.0 160.0 160.0 240.0 240.0 240.0 240.0 240.0
69 65 52 43 42 165 97 64 51 43
58 58 44 37 35 158 84 55 43
44.3 38.8 30.9 27.2 23.9 121.1 64.6 37.5 27.5 21.6 25.1 19.8 16.4 14.9 12.8 18.5 15.5 13.0 12.0 10.3 15.6 13.7 11.8 9.6 8.9 101.4 53.8 30.4 21.0 16.3 107.1 57.1 34.1 25.7 18.4 172.8 85.6 50.6 38.9 32.7 187.7 94.3 61.0 50.3 39.5
: 29 32 22 46 48 30 34 24 46 36 28 22 30 148 91 66 46 34 156 93 63 47 36 218 114 88 53 56 :: 92 68 64
: 31 24 22 18 30 28 22 21 15 26 21 18 14 14 124 71 53 :: 142 83 47 E 213 109 70 48 2: 119 80 65 57
AI,,,
AI,,
At,,
AL
AI,,
Al,,,
At,,
.W?C
set
set
set
see
set
set
20.9 17.7 13.9 12.1 9.5 74.9 38.5 20.4 15.1 11.6 13.5 10.1 8.8 8.0 6.8 9.8 8.7 6.8 6.0 5.5 8.8 7.3 6.1 5.1 4.7 51.7 27.9 13.9 9.6 7.9 58.3 32.1 17.9 11.5 9.3 94.4 47.9 26.6 22.1 18.1 96.2 51.2 33.7 27.4 23.1
67 58 52 46 41 172 106 62 48 38 57 51 44
41.6 34.9 31.1 26.3 23.4 120.0 68.0 35.9 26.8 20.2 30.4 26.6 22.7 19.2 17.1 20.8 17.4 15.5 13.1 11.7 13.8 11.6 10.3 8.7 7.8 89.4 50.6 26.7 20.0 15.0 105.5 59.8 31.6 23.6 17.7 157.4 89.2 47.1 35.2 26.4 198.8 112.7 59.5 44.4 33.4
27.5 22.9 20.4 17.1 15.2 83.3 46.3 23.9 17.7 13.2 20.4 17.8 15.1 12.7 11.2 14.2 11.8 10.5 8.8 7.8 9.6 8.0 7.1 6.0 5.3 60.4 33.5 17.3 12.8 9.5 72.4 40.2 20.8 15.4 11.4 111.9 62.2 32.1 23.7 17.7 144.5 80.2 41.4 30.6 22.6
21.0 17.4 15.4 12.9 11.4 65.8 36.0 18.3 13.5 10.0 15.8 13.7 11.6 9.7 8.6 11.2 9.3 8.2 6.9 6.1 7.7 6.4 5.7 4.7 4.2 46.8 25.7 13.0 9.6 7.1 56.7 31.1 15.8 11.6 8.6 89.9 49.2 25.0 18.4 13.6 117.6 64.4 32.8 24.1 17.8
28.2 24.1 19.1 16.8 13.9 90.8 46.6 25.6 18.7 14.7 16.6 12.9 10.9 9.8 8.9 12.3 10.7 9.1 8.3 6.8 10.6 9.2 8.1 6.5 5.9 66.9 35.4 18.6 12.5 10.6 74.9 39.6 23.4 15.7 12.5 123.3 61.9 34.2 27.8 22.6 119.9 64.5 43.1 34.5 27.3
*At” = peak width at l/n fraction of peak height above the baseline.
:; 47 40 36 :; 38 :o’ ;: 142 88 51 40 32 158 98 57 45 2: 126 74 58 45 236 146 85 67 53
45 :: 155 92 51 39 30 44 39 34 29 26 31 27 24 21 18 22 19 17 14 13 121 72 40 31 24 139 82 46 35 27 194 115 64 49 2:: 140 G 46
At*,
ANNOTATION
912
the data given by Gomez-Nieto et al.* indicates an inverse relationship between q and A?,, and in a quotation of equation (1) the exponent of q was given a negative sign, we assume that the original positive sign* arose from an undetected error in the manuscript or the proofs. In the work reported here, equations (2) and (3) predicted the results of more than three-quarters of the experiments, with a relative error of less than 20%.
Equations (4x11) predicted the results of more than three-quarters of the experiments, with a relative error of less than 20%. Expressions for peak width are of value in designing flow-injection manifolds for routine analysis of samples, because the peak width determines the maximum analysis rate that can be achieved. As some peak overlap is permissible, equations giving nearbaseline peak width are of practical value. ’
Peak width above baseline Where peak width is measured above the baseline, expressions analogous to equations (l)-(3) may be derived. For peak width measured at one-fiftieth of the peak height above the baseline, Atso, in set, is
CONCLUSION
for ICP emission spectrometric detection.
The procedure* for establishing an expression for peak width was found to give equally satisfactory results when applied to a flow-injection manifold where the injection volume was ten times that used in the original work. Similar expressions were obtained for both spectrophotometric and ICP emission spectrometric detection. Predictive equations for peak width at various points above the baseline can be formulated analogously.
The corresponding equations for peak widths measured at one-tenth (Atlo), one-third (AtJ) and half (At*) of the peak height above the baseline (all in set), are:
Acknowledgements-Mrs A. Kolbe is thanked for preparing Fig. 1. Mrs B. M. Sutton is thanked for typing the manuscript, which is published by permissiw~of the Department of Water Affairs.
Atso=
23&fl.745L0366q-l.022
for spectrophotometric
(4)
detection, and
At, = 11.7dO.BS9 LO.462q -0.968
(5)
At,, = 12.0f19m Lo”48q - Ls@S
(6)
Atlo = 5.67&‘.966 L”.577q-‘.oY
(7)
At, _ 4.97d’.0”L0.558q-1.130 At, =
3~0~0.9’8~0.629~-l.O91
At2 = 2.81d0.99’L0.6u1q-l.129 At, = 2~)~0.876~0.~~-1.116
REFERENCES
(8) (9) (10) (11)
where the first equation of each pair refers to spectrometric detection, and the second to ICP emission spectrometric detection.
1. J. T. Vanderslice, K. K. Stewart, A. G. Rosenfeld and D. J. Higgs, Tafanta, 1981, 2B, 11. 2. M. A. Gomez-Nieto, M. D. Luaue de Castro. A. Martin and M. ValcPrcel, ibid., 1985, j2, 319. 3. J. J. Pauer. H. R. Van Vliet and J. F. Van Staden. Wuter S.A., 1988, 14, 125. 4. P. L. Kempster, J. F. Van Staden and H. R. Van Vliet, Z. Anal. Chem., 1988, 332, 153. 5. I&m, J. Anal. At. Spectrom., 1987, 2, 823. 6. M. Valc&el and M. D. Luque de Castro, FfowInjection Analysis, Principles and Applications, p. 90. Horwooci, Chichester, 1987.
0039-9140/89 $3.00 + 0.00
Copyright0 1989 Pqamon Press plc
ANNOTATION
PREDICTION OF FIA PEAK WIDTH FOR A FLOW-INJECTION MANIFOLD WITH SPECTROPHOTOMETRIC OR ICP DETECTION PHILLIP LYLEKEMPSTER and HENK ROBERTVANVLIET Hydrological Research Institute, Department of Water Affairs, private Bag X313, Pretoria, South Africa
JACOBUSFREDRRICKVANSTADEN Department of Chemistry, University of Pretoria, Pretoria, South Africa (Received 21 December 1988. Accepted 31 March 1989)
Slmun;uy-Equations are proposed for predicting the width of a FIA peak when a sample injection volume of 300 ~1 is used. The equations for both spectrophotometric and inductively coupled plasma emission spectrometric detection are similar.
dissolving 0.1596 g of anhydrous copper sulphate and 5.35 g of ammonium chloride in 500 ml of demineralized water, adding 8 ml of 13M ammonia solution, and making up with water to 1 litre. Two blank solutions, corresponding to stock solutions A and B and containing ammonium chloride and ammonia, but not the copper sulphate, were also prepared, to serve as carrier and wash solutions.
In FIA thedry, expressions for peak width, such as baseline-to-baseline time, are of practical value in the design of FIA manifolds, for automated analysis of environmental water samples, for example. Vanderslice et al.’ provided an expression for baseline-to-baseline time from numerical integration of the diffusion-convection equation. Gbmez-Nieto et al.* developed an experimental approach for determining an expression for baseline peak-width and the present paper essentially describes an extension of that work. Vanderslice et al.’ took the sample injection volume as 2 ~1, while Gbmez-Nieto et al.* used a sample injection volume of 30 ~1. In the analysis of water samples by FIA methods, sample injection volumes in excess of 200 ~1 may be required3*’ in order to obtain sufficient sensitivity. Our aim was to develop an expression for peak width at half, one-third, one-tenth and one-fiftieth peak height, as well as baseline peak width, by using the experimental approach suggested by GbmezNieto et al.2 but for a 300-~1 injected sample volume. , A simple FIA configuration was used with either spectrophotometric or inductively coupled plasma (ICP) emission spectrometric detection of the analyte, which was the diaquatetra-aminecopper(I1) complex.
EXPERIMENTAL Reagents Analytical grade reagents were used. Copper stock sol-
ution A (O.OlM) was prepared by dissolving 1.596 g of anhydrous copper sulphate and 10.70 g of ammonium chloride in 500 ml of demineralized water, adding 16 ml of 13M ammonia solution and making up with water to 1 litre. Copper stock solution B (O.OOlM) was prepared by
Apparatus The FIA manifold is shown in Fig. 1. Two sets of measurements were made, one with an LKB Novaspec spectrophotometer with a Helhna 178.011-05 flow-cell having a chamber volume of 30 pl and an inlet dead volume of 147 ~1, the other with an ARL 34000 ICP Quantometer fitted with an ll-ml cloud chambezS The carrier solution was propelled with a Gilson Minipuls 2 peristaltic pump. A second Gilson Minipuls 2 pump was used to aspirate the sample/wash solutions from a Cenco 345.17.700 sampler, through the 300-p 1 sampling loops of a Carle 2013 sampling valve. The sampler and sampling valve were activated by a laboratory-made electronic timer. The sample uptake rate was adjusted to 6.3 ml/min. The FIA peak proties were recorded on a Hitachi 056-1002 potentiometric recorder, peaks being recorded in triplicate. Copper stock solution A was used as the sample solution when the spectrophotometer was employed as detector, the wavelength being set at 600 nm; copper stock solution B was used as the sample solution when the ICP spectrometer was employed as detector; the wavelength of the copper channel on the spectrometer was 327.40 nm. The plasma was operated at a radiofrequency power of 1.25 kW. Argon gas flow-rates to the torch were 11.0,0.40 and 0.40 l&in for the outer, intermediate and inner gas flows respe&vely, at a gauge pressure of 340 kPa. The length L and internal diameter d of the tubing betwen the flow injection valve and the deteotor were in the ranges 6240 cm and 0.38-1.19 mm respectively. Carrier flow-rate values, q, between 0.7 and 3.8 ml/min were chosen. As suggested by CSmez-Nieto et al.,2 at least five points were obtained for each variable, with the other two variables kept constant. The baseline width, width at one-ii!&&,
969
970
ANNOTATION
Fig. 1. FIA manifold used for peak-width evaluation.
Table 1. Experimental and calculated data for the FIA manifold in Fig. 1, with spectrophotometric
Q> mllmin
d, mm
2.2 2.6 3.0 3.4 3.8 2.2 2.6 3.0 3.4 3.8 2.2 2.6 3.0 3.4 3.8 2.2 2.6 3.0
1.19 1.19 1.19 1.19 1.19 1.02 1.02 1.02 1.02 1.02 0.86 0.86 0.86 0.86 0.86 0.58 0.58 0.58 0.58 0.58 0.38 0.38 0.38 0.38 0.38 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02
:.;: 212 ::: :.;: 0:7 1.0 1.4 1.8 ;: 3:o 3.4 3.8 :?i 3:o 3.4 3.8 2.2 2.6 3.0 3.4 3.8 2.2 :::
L., m 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 loo.0 100.0 loo.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Z8
Ars, set
At,*, set
Atlo, set
At,, set
At,, set
Ats, set
A‘,, set
At,,, see
*r,, set
Ar,, see
65 64 48
62 59 43 46 38 49 42 38 32 28 45 36
43.6 36.3 32.0 29.9 26.5 39.2 33.5 29.2 24.7 21.6 30.3 25.2 21.2 18.4 15.1 20.3 16.7 14.4 12.3 11.0 17.6 15.1 12.9 11.1 10.0 106.5 82.9 57.6 43.0 34.5 27.2 22.1 18.7 16.6 43.4 37.8 32.3 27.9 24.0 49.1 42.0 36.6 33.2 29.8 59.1 45.8 42 5 44:1 38.6
27.3 22.7 19.6 18.5 15.6 28.4 24.3 21.1 18.1 16.0 18.9 16.8 13.9 11.7 9.5 12.1 10.7 9.1 8.2 6.8 10.5 9.2 8.4
20.1 17.2 14.8 14.2 11.6 23.5 19.8 17.4 14.6 12.7 14.6 12.8 10.7 9.1 7.7 9.5 8.6
70 60 53 47 43 65 56 49 44 40 60 52 46 41 37 51 44 38
64 54 47 41 37 57 48 42 37 33 50 42 37
::; 5.4 8.6 7.4 6.2
:: 42 36 32
:f 55:s 41.2 26.7 21.4 15.5 12.8 10.4 8.8 7.5 20.9 18.3 16.3 14.2 11.9 28.8 24.1 21.2 19.4 17.8 34.8 28.2 25.3 24.8 22.4
:: 157 114 84 67 56 48 43 38 35 61 53 46 41 38 74 64 56 50 46 83 72 63 56 51
31.8 26.3 22.4 19.4 17.1 27.2 22.5 19.1 (6.6 14.6 22.8 18.9 16.1 14.0 12.3 15.3 12.7 10.8 9.4 8.3 10.0 8.3 7.0 6.1 5.4 74.5 49.8 34.0 25.6 20.4 16.9 14.4 12.5 11.0 24.0 19.9 16.9 14.7 12.9 35.3 29.2 24.9 21.6 19.0 44.3 36.7 31.2 27.1 23.9
24.7 20.5 17.4 15.1 13.3 21.2 17.6 14.9 13.0 11.4 17.9 14.8 12.6 11.0 9.7 12.1 10.0 8.5 7.4 6.5 8.0 6.6 5.6
24 71:8 54.5 36.7 28.1 21.2 17.3 14.0 11.6 10.3 28.0 24.7 21.2 18.1 15.2 35.1 29.6 26.1 23.5 21.2 42.9 35.0 32.1 30.1 27.2
47.0 39.1 33.4 29.2 25.8 40.6 33.8 28.9 25.2 22.3 34.5 28.7 24.6 21.4 19.0 23.7 19.8 16.9 14.7 13.0 15.9 13.2 11.3 9.9 8.7 113.1 76.6 53.0 40.2 32.3 26.9 23.0 20.0 17.7 36.7 30.6 26.2 22.8 20.2 50.1 41.7 35.7 31.1 27.5 60.1 50.0 42.8 37.3 33.0
z 51 45 40 33 30 56 44 51 42 34 51 45 45 42 32 40 :: : 159 126 91
ZZ:8 ::8 ::8 60.0 80.0 80.0 80.0 80.0 80.0 160.0 160.0 160.0 160.0 160.0 240.0 240.0 240.0 240.0 240.0
detection
Calculated
Experimental
zl 44 38 ;: 69 60 56 54 47 79 72 64 54 :: :: 64 53
:: 27 37 :: 23 :; ;: 17 17 143 112 81 60 :; 32 ;: 61 54 47 42 36 69 59 52 46 42 78 55 z 51
*A!, = peak width at l/n fraction of peak height above the baseline.
;; :; 27 24 22 t: 20 18 16 153 106 75 58 : 35 30 27 53 44 38 :: 68 57 50 44 39 79 66 57 50 45
z 56:l 37.5 25.6 19.3 15.4 12.7 10.8 :*t: 18:4 15.3 13.0 11.3 9.9 28.5 23.6 20.1 17.4 15.4 36.8 30.4 25.9 22.5 19.8
971
ANNOTATION
one-tenth, one-third and half maximum peak-height were measured from the recorder chart. Recorder response-time was less than 0.1 sec.
equation (l), the equations which were obtained for the manifold described in this paper were: Atx = 35&jo.444L0.28Zq
RFSULTS AND DISCUSSION
Baseline-to-baseline
(2)
detection and
At, = 22J@.~LO.‘67 4 -0.888
Gomez-Nieto et al.’ proposed the equation for baseline-to-baseline times: Atx =
for spectrophotometric
time
-0.893
(3)
following for ICP emission spectrometric detection.
c~j7&293~0.107~1.057
The experimental data, giving the mean of the measured values together with the predicted values, are shown in Table 1 for spectrophotometric detection and in Table 2 for ICP emission spectrometric detection. A difference which is immediately apparent is that the exponent of q is negative in equations (2) and (3) but positive in equation (1). Since perusal of
(1)
where At, is the base width in set, and the units of the diameter d, length L and flow-rate q are mm, cm and ml/min respectively. By following the procedure suggested by Gomez-Nieto et al.’ of performing multiple regressions for the logarithmic form of
Table 2. Experimental and calculated data for FIA manifold in Fig. 1 with ICP emission spectrometric detection Experimental 4. mllmin
d, mm
2.2 2.6 2.9 3.4 3.8 0.7 1.2 2.2 2.9 3.8
1.19 1.19 1.19 1.19
4:: 2.9 3.4 3.8 2.2 2.6 2.9 3.4 3.8 2.2 g 3:4 3.8 0.7 1.2 2.2 2.9 3.8 0.7 1.2 g 3:8 0.7 1.2 22.; 3:8 0.7 1.2
1.19 1.02 1.02 1.02 1.02 1.02 0.86 0.86 0.86 0.86 0.86 0.58 0.58 0.58 0.58 0.58 0.38 0.38 0.38 0.38 0.38 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02
1.02 1.02 1.02 1.02
Calculated
At,,
At,*,
L, cm
set
see
set
loo.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 60.0 60.0 60.0 60.0 60.0 80.0 80.0 80.0 80.0 80.0 160.0 160.0 160.0 160.0 160.0 240.0 240.0 240.0 240.0 240.0
69 65 52 43 42 165 97 64 51 43
58 58 44 37 35 158 84 55 43
44.3 38.8 30.9 27.2 23.9 121.1 64.6 37.5 27.5 21.6 25.1 19.8 16.4 14.9 12.8 18.5 15.5 13.0 12.0 10.3 15.6 13.7 11.8 9.6 8.9 101.4 53.8 30.4 21.0 16.3 107.1 57.1 34.1 25.7 18.4 172.8 85.6 50.6 38.9 32.7 187.7 94.3 61.0 50.3 39.5
: 29 32 22 46 48 30 34 24 46 36 28 22 30 148 91 66 46 34 156 93 63 47 36 218 114 88 53 56 :: 92 68 64
: 31 24 22 18 30 28 22 21 15 26 21 18 14 14 124 71 53 :: 142 83 47 E 213 109 70 48 2: 119 80 65 57
AI,,,
AI,,
At,,
AL
AI,,
Al,,,
At,,
.W?C
set
set
set
see
set
set
20.9 17.7 13.9 12.1 9.5 74.9 38.5 20.4 15.1 11.6 13.5 10.1 8.8 8.0 6.8 9.8 8.7 6.8 6.0 5.5 8.8 7.3 6.1 5.1 4.7 51.7 27.9 13.9 9.6 7.9 58.3 32.1 17.9 11.5 9.3 94.4 47.9 26.6 22.1 18.1 96.2 51.2 33.7 27.4 23.1
67 58 52 46 41 172 106 62 48 38 57 51 44
41.6 34.9 31.1 26.3 23.4 120.0 68.0 35.9 26.8 20.2 30.4 26.6 22.7 19.2 17.1 20.8 17.4 15.5 13.1 11.7 13.8 11.6 10.3 8.7 7.8 89.4 50.6 26.7 20.0 15.0 105.5 59.8 31.6 23.6 17.7 157.4 89.2 47.1 35.2 26.4 198.8 112.7 59.5 44.4 33.4
27.5 22.9 20.4 17.1 15.2 83.3 46.3 23.9 17.7 13.2 20.4 17.8 15.1 12.7 11.2 14.2 11.8 10.5 8.8 7.8 9.6 8.0 7.1 6.0 5.3 60.4 33.5 17.3 12.8 9.5 72.4 40.2 20.8 15.4 11.4 111.9 62.2 32.1 23.7 17.7 144.5 80.2 41.4 30.6 22.6
21.0 17.4 15.4 12.9 11.4 65.8 36.0 18.3 13.5 10.0 15.8 13.7 11.6 9.7 8.6 11.2 9.3 8.2 6.9 6.1 7.7 6.4 5.7 4.7 4.2 46.8 25.7 13.0 9.6 7.1 56.7 31.1 15.8 11.6 8.6 89.9 49.2 25.0 18.4 13.6 117.6 64.4 32.8 24.1 17.8
28.2 24.1 19.1 16.8 13.9 90.8 46.6 25.6 18.7 14.7 16.6 12.9 10.9 9.8 8.9 12.3 10.7 9.1 8.3 6.8 10.6 9.2 8.1 6.5 5.9 66.9 35.4 18.6 12.5 10.6 74.9 39.6 23.4 15.7 12.5 123.3 61.9 34.2 27.8 22.6 119.9 64.5 43.1 34.5 27.3
*At” = peak width at l/n fraction of peak height above the baseline.
:; 47 40 36 :; 38 :o’ ;: 142 88 51 40 32 158 98 57 45 2: 126 74 58 45 236 146 85 67 53
45 :: 155 92 51 39 30 44 39 34 29 26 31 27 24 21 18 22 19 17 14 13 121 72 40 31 24 139 82 46 35 27 194 115 64 49 2:: 140 G 46
At*,
ANNOTATION
912
the data given by Gomez-Nieto et al.* indicates an inverse relationship between q and A?,, and in a quotation of equation (1) the exponent of q was given a negative sign, we assume that the original positive sign* arose from an undetected error in the manuscript or the proofs. In the work reported here, equations (2) and (3) predicted the results of more than three-quarters of the experiments, with a relative error of less than 20%.
Equations (4x11) predicted the results of more than three-quarters of the experiments, with a relative error of less than 20%. Expressions for peak width are of value in designing flow-injection manifolds for routine analysis of samples, because the peak width determines the maximum analysis rate that can be achieved. As some peak overlap is permissible, equations giving nearbaseline peak width are of practical value. ’
Peak width above baseline Where peak width is measured above the baseline, expressions analogous to equations (l)-(3) may be derived. For peak width measured at one-fiftieth of the peak height above the baseline, Atso, in set, is
CONCLUSION
for ICP emission spectrometric detection.
The procedure* for establishing an expression for peak width was found to give equally satisfactory results when applied to a flow-injection manifold where the injection volume was ten times that used in the original work. Similar expressions were obtained for both spectrophotometric and ICP emission spectrometric detection. Predictive equations for peak width at various points above the baseline can be formulated analogously.
The corresponding equations for peak widths measured at one-tenth (Atlo), one-third (AtJ) and half (At*) of the peak height above the baseline (all in set), are:
Acknowledgements-Mrs A. Kolbe is thanked for preparing Fig. 1. Mrs B. M. Sutton is thanked for typing the manuscript, which is published by permissiw~of the Department of Water Affairs.
Atso=
23&fl.745L0366q-l.022
for spectrophotometric
(4)
detection, and
At, = 11.7dO.BS9 LO.462q -0.968
(5)
At,, = 12.0f19m Lo”48q - Ls@S
(6)
Atlo = 5.67&‘.966 L”.577q-‘.oY
(7)
At, _ 4.97d’.0”L0.558q-1.130 At, =
3~0~0.9’8~0.629~-l.O91
At2 = 2.81d0.99’L0.6u1q-l.129 At, = 2~)~0.876~0.~~-1.116
REFERENCES
(8) (9) (10) (11)
where the first equation of each pair refers to spectrometric detection, and the second to ICP emission spectrometric detection.
1. J. T. Vanderslice, K. K. Stewart, A. G. Rosenfeld and D. J. Higgs, Tafanta, 1981, 2B, 11. 2. M. A. Gomez-Nieto, M. D. Luaue de Castro. A. Martin and M. ValcPrcel, ibid., 1985, j2, 319. 3. J. J. Pauer. H. R. Van Vliet and J. F. Van Staden. Wuter S.A., 1988, 14, 125. 4. P. L. Kempster, J. F. Van Staden and H. R. Van Vliet, Z. Anal. Chem., 1988, 332, 153. 5. I&m, J. Anal. At. Spectrom., 1987, 2, 823. 6. M. Valc&el and M. D. Luque de Castro, FfowInjection Analysis, Principles and Applications, p. 90. Horwooci, Chichester, 1987.