14aa
Anal. Chem. 1985, 57, 1488-1490
amine in air has been developed. The technique offers a simple means of collecting air samples by using a novel twocomponent solid adsorbent system, and a fast analysis by thermal desorption directly into a GC equipped with an NPD. The key analytical features responsible for the good sensitivity and low background effects achieved include the selectivity of the NPD, the physicochemical properties of the soda lime/Tenax-GC adsorbent, and the advantages of the two-stage thermal desorption system.
2 m x 3 . 2 m m O.D.,
3% O V - I ON ULTRA BOND 2 O M (100-120 M E S H ) - 160°C
n
I6O
Registry No. Amphetamine, 300-62-9.
LITERATURE CITED
u
0
I 2 3 4 5 MINUTES
I_LL--IL_I
0 1 2 3 4 MINUTES
5
Figure 4. Chromatograms of desorbates from (a) sampler no. (-5,O) and (b) sampler no. (+5,1). of the desorbates indicated that amphetamine was collected efficiently on sampler no. (+5,1) and only a trace quantity was collected on sampler (+5,0) (Figure 3). This was not unexpected since the mean wind direction during the 60-min sampling period was estimated to be southeast. The amount of amphetamine collected on sampler (+5,1) and measured chromatographically (Figure 4) compared well with the value estimated by using the turbulent diffusion equation for a steady emitting source near the ground (15). The detection limit with the present two-component adsorber configuration of amphetamine vapor in ambient air, based on a signal-to-noise ratio SIN >3, corresponds to 5 ppt or 0.03 bg/m3 amphetamine, in a 65-L air sample.
CONCLUSIONS A method for the detection of trace amounts of amphet-
(1) Lawrence, A. H.; MacNeil, J. D. Anal. Chem. 1982, 5 4 , 2385-2367. (2) Fishbein, L. "Chromatography of Environmental Hazards"; Elsevier: New York, 1982; Voi. IV, p 311. (3) Baker, J. K. Anal. Chem. 1977, 49,906-906. (4) Dalene, M.; Mathiasson, L.; Jonsson, J. A. J . Chromatogr. 1981, 207, 37-46. (5) Audunsson, G.; Mathiasson. L. J . Chromatogr. 1983, 261, 253-257. (6) Kuwata, K.; Akiyama, E.; Yamazaki, Y.; Yamazaki, H.; Kuge, Y. Anal. Chem. 1983, 55, 2199-2201. (7) Wood, G. 0.: Nichols, J. W. LASL Project R-059, NIOSH-IA-77-12 Report, LA-7295-PR, Los Alamos Scientific Laboratory, University of California, 1976. (8) Lovkvist, P.; Jonsson, J. A. J . Chromatogr. 1984. 286, 279-285. (9) Kashihira, N.; Makino, K.; Kirita, K.; Watanable, Y. J . Chromatogr. 1982, 239, 617-624. (IO) Kuwata, K.; Yamazaki, Y.; Uebori, M. Bunseki Kagaku, Shimpo Sosetsu 1980, 29, 170; Chem. Abstr. 1980, 92,220050. (1 1) Lawrence, A. H.; Elias, L.; Authier-Martin, M. Can. J . Chem. 1984, 62,1886-1888. (12) Predmore, D. B.; Christian, G. D. Anal. Chem. 1976, 4 8 , 361-363. (13) Lawrence, A. H.; Elias, L. Canadian Patent Application No. 429803, June 6, 1963. (14) Andr6, C. E.; Mosier, A. R. Anal. Chem. 1973, 4 5 , 1971-1973. (15) Crabbe, R. S. NRC DMEINAE, Quarterly Bulletin, National Research Council, 1973, Ottawa, Canada.
RECEIVED for review November 21,1984. Accepted February 4, 1985. Presented in part a t the ACS Symposium on Analytical Methods in Forensic Chemistry, April 29-May 2, 1985, Miami, FL.
Preparation of Chelex-100 Resin for Batch Treatment of Sewage and River Water at Ambient pH and Alkalinity J a m e s A. Buckley
Metro Water Quality Laboratory, 410 West Harrison Street, Seattle, Washington 98119 The chemistry of trace metals in natural waters and sewage is influenced bv DHand alkalinity (1-5). Moreover, the uptake of trace metals 6y Chelex-100 ispH-dependent (6, 7). 1; this laboratory, equilibration with Chelex-100 of samples of river water Or sewage by the batch method (8) in a substantial increase in p H above ambient levels, an increase that was believed due to wash out of free OH- from the resin pore structure. Extensive washing with deionized water was only partially successful in controlling the elevation in pH but suggested that using a buffer wash might be more successful. In the following report, the work described in ref 9 and 10 regarding p H reduction in Chelex-100 column effluent provided part of the rationale for the development of the following method in which ambient levels of pH and alkalinity are maintained in water samples equilibrated with Chelex-100 which has been prewashed in acetate buffer of predetermined concentration.
EXPERIMENTAL SECTION Materials. Analytical-grade Chelex-100 resin (Bio-Rad Laboratories, control 25633), 50-100 mesh, in the Na form was used 0003-2700/85/0357-1488$01.50/0
in units of 0.5 g (as weighed from the original container, moisture content 68% to 76%) per 100 mL of buffer or 50 mL of water sample. A stock 3.5 M acetate buffer solution of pH 4.7 was prepared from 238 g of sodium acetate trihydrate dissolved in deionized water(DW), to which was added 102 mL of glacial acetic acid. The solution was then diluted to L, This stock buffer was diluted to 0.5 M for daily use. River water samples were collected from the Green-Duwamish River near Renton, WA. Sewage samples were collected from a secondary clarifier at the Municipality of Metropolitan Seattle's Renton Treatment Plant-a secondary-treatment, activatedsludge-process plant. Procedure for Washing of Chelex Resin in 0.5-g Units. The 0.5 M buffer was diluted with DW to the desired concentration in a 100-mL volumetric flask, and the diluent transferred to a 150-mL beaker containing a 2.5-cmstir bar, Then o.5 of Chelex was added, and the beaker was placed on a mag-mixset at ficient speed to keep the resin in suspension. After 15 min (unless other time specified), the resin was recovered on a 5-in., S&S No. 123 filter-sub placed in a glass-powder funnel. While still on the filter-sub the resin was rinsed with 400-500 mL of DW for 3 min, removed from the funnel, and drained on paper towels for 12 min. 0 1985 American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 57, NO. 7, JUNE 1985
Table I. Mean pH and Total Alkalinity of Duplicate Samples of Sewage and River Water Equilibrated without Chelex (Control), or with Buffer-Washed Chelex, or with Unwashed Chelex for Three Time Periods sample
equilibration 4h 24 h
Chelex preparation
20 min
1489
polypropylene centrifuge tube containing a small glass marble for mixing. An aliquot of washed Chelex (0.5 g, original weight) was added, and the tube was capped and placed on a laboratory tube rocker. Equilibration was for 20 min (unless other time specified), after which the tube was centrifuged at low speed for approximately 30 s, and the supernatant was either decanted or removed by pipet for measurement of pH and total alkalinity (11).
RESULTS AND DISCUSSION
PH sewage
control washed unwashed
7.27 7.29 8.66
7.30 7.28 8.65
7.28 7.28 8.59
river water
control washed unwashed
7.39 7.38 8.88
7.37 7.46 9.57
7.34 7.60 9.77
alkalinitp sewage
control washed unwashed
158 156 201
157 155 201
158 154 202
river water
control washed unwashed
48 47 64
48 48 76
47 49 85
"mg L-' as CaCO?. If not used immediately, the resin (on the filter-sub) was kept moist in a covered, humidified, 150 X 15 mm petri dish. Washing of Chelex Resin in Batch Lots. The resin was prepared as outlined in the previous section, with the ratio of acetate buffer to Chelex kept a t 100 mL per 0.5 g. The weight of the drained resin was divided by the original number of 0.5-g aliquots, and the resulting amounts of resin (usually somewhat greater than 0.5 g owing to the moisture from washing) were placed individually in small plastic weighboats. If not used immediately, the resin was kept humidified as described previously. Equilibration. With a 50-mL volumetric pipet and minimum aeration, the water sample was placed in a 50-mL, free standing,
Chelex-100 resin was washed in 0.5-g units in acetate buffer of 0.25-10 mM and in DW (control) and then equilibrated with samples of sewage for 30 min. A plot of the p H and alkalinity measurements of the equilibrated samples vs. the log concentration of the buffer wash yielded the sigmoid-shaped curves shown in Figure la. It can be seen that the p H (7.32) and alkalinity (139 mg L-l) of the original (untreated) sewage sample were maintained during equilibration with Chelex prewashed in approximately 1.5 m M buffer. When equilibration was extended t o 18 h, p H values were increased and decreased at low- and high-buffer concentrations, respectively, probably owing to washout of OH- or buffer from resin pores, but were only slightly increased at intermediate concentrations, corresponding to p H values of waters used in this work. To more precisely define the relationships shown in Figure l a , in the region of the curve most useful for samples of p H 7.0 to 7.4, and t o determine whether those relationships were constant over small variations in equilibration time, Chelex resin was washed in buffer of 1.0-2.2 m M and equilibrated with sewage for periods of 10, 20, and 30 min. The curves plotted from the results of tests over the three time periods were similar; therefore, a 20-min equilibration (Figure l b ) was used in subsequent work in which shorter equilibrations were wanted. As can be seen in Figure l b , the p H (7.30) and alkalinity (139 mg L-I) of the original (untreated) sample were maintained during equilibration with resin prewashed in 1.4 mM buffer. Because both the original p H and alkalinity of the samples were maintained with the same buffer concen-
Table 11. Mean pH of Triplicate Samples of River Water Equilibrated for 24 h with Chelex-100 That Was was Prewashed in Acetate Buffer for the Indicated Times wash time
x S
control"
15 rnin
30 rnin
l h
3h
5h
5 h DWb
7.47 0.02
7.75 0.01
7.40 0.01
7.31 0.03
7.27 0.01
7.30 0.01
8.88 0.02
"River water without Chelex. bChelexwashed for 5 h in deionized water only. Table 111. pH and Total Alkalinity of River Water and Sewage Equilibrated with Buffer-Washed Chelex or with Unwashed Chelex sample river water
x n S
river water
x n
S
river water
x n S
sewage
x n S
sewaged
x n
S
sewage
x n S
controlb
PH washed
unwashed
controlb
6.49 5 0.04 7.34 12 0.05 8.11 5 0.10 6.54 5 0.01 7.31 12 0.04 8.12 5 0.01
6.46 5 0.02 7.34 37 0.05 8.12 5 0.06 6.59' 5 0.02 7.32 16 0.05 8.21' 5 0.05
7.68' 5 0.09 8.8gC 3 0.05 9.42c 5 0.02 7.39' 5 0.05 9.52' 4 0.01 9.2lC 5 0.02
21 5 0 49 4 1 34 5 0 79 5
alkalinity" washed
0
61 4 0
170 5 1
"mg L-l as CaCO,. b N o Chelex. ' P < 0.05 vs. control by ANOVA. dSewage diluted with river water.
1gC 5 0 48 4 1 35 5 0 85' 5 1 60 4 1 170 5 1
unwashed 44' 5 1 66 1 5OC 5 1 136' 5 1 97 1 206' 5 2
1490
Anal. Chem. 1985, 57, 1490-1492
1
~ 1 7 5
11503
IO
14 18 ACtIlIf B U l l f R m M
22
Figure 1. The relationship between concentration of acetate buffer wash for the Chelex resin and pH and total alkalinity (as CaCO,) of sewage samples equilibrated (a) for 30 min (dashed curve equilibrated for 18 h) or (b) for 20 rnin with washed Chelex. Deionized water (DW) wash in (a) for comparison.
tration, the curve for pH alone was considered suitable as a standard for determining the concentration of wash buffer to be used for maintenance of those parameters once the pH of the original sample was known. The influence of equilibration time on pH and alkalinity of sewage and river water samples was examined further by construction of standard curves (15-min wash and 20-min equilibration) for determination of the concentration of wash buffer needed (1.7 and 1.6 mM for sewage and river water, respectively, determined from curves much like that for pH in Figure lb), and then equilibration of the samples with the washed resin for 20 min, 4 h, or 24 h. The results, shown in Table I, indicate that the original pH and alkalinity of the sewage samples were maintained for the full 24-h period. Over the same time period, the pH of the less-well-buffered river water increased slightly, from 7.38 to 7.60. When unwashed Chelex was used, both pH and alkalinity values increased substantially over control values.
The influence of wash duration on the pH of river water after a 24-h equilibration was studied by selecting a concentration of wash buffer (1.7 mM) from a standard curve and then washing the Chelex for periods of 15 min to 5 h before equilibration. The results, in Table 11, indicate that increasing duration of wash to 25 (by graphical interpolation) to 30 min would be effective in maintaining pH to approximately that of the control sample over the 24-h equilibration and would eliminate the slight increase in pH observed for the river water sample, in Table I. The procedure outlined above for maintaining the pH and alkalinity at ambient levels during batch treatment with Chelex-100 was tested at three values of pH in the range 6.5-8.1 of natural waters and sewage. Before each test the pH of the water sample (-7.3) was adjusted with HNOB(6.5) or NaOH (8.1) and then a standard curve of sample pH vs. concentration of wash buffer (represented by Figure l b for samples of pH 7.3 and by Figure l a for sample of pH 6.5 and 8.1) was graphed from data obtained with a 15-min wash of the resin followed by a 20-min equilibration with the water sample. The results, in Table 111, show that washing the resin with a predetermined concentration of buffer was effective in maintaining pH and alkalinity very close to that of the control sample. The results presented here indicate that substantial increases in pH can occur in samples of river water and sewage undergoing batch equilibration with Chelex-100 and that the method presented here is useful in maintaining ambient levels of pH as well as alkalinity of these samples during equilibration. Hegistry No. H20,7732-18-5;sodium acetate, 127-09-3;acetic acid, 64-19-7; Chelex-100, 11139-85-8.
LITERATURE CITED (1) Stiff, M. J. Water Res. 1971, 5 , 585-599. (2) Gardiner, J. Water Res. 1974, 8 , 23-30. (3) Giesy, J. P.; Briese. L. A,; Leversee, G. J. Environ. G e o / ( N . V . ) 1978, 2 , 257-268. (4) Shephard, B. K.: McIntosh, A. W.; Atchison, G. J.; Nelson, D. W. WaterRes. 1980, 7 4 , 1061-1066. (5) Sposito, G. Environ. Sci. Technoi. 1981, 75, 396-403. (6) Florence, T. M.; Batley, G. E. Talanta 1975, 22, 201-204. (7) Figura. P.: McDuffie, B. Anal. Chem. 1977, 4 9 , 1950-1953. (8) Hart, B. T.; Davies, S. H. R . Aust. J . Mar. FreshwaterRes. 1977. 28, 397-402. (9) Pakalns, P.; Batley, G. E.; Cameron, A. J. Anal. Chlm. Acta 1978, 9 9 , 333-342. (10) "Cheiex 100 Chelating Ion Exchange Resin for Analysis, Removal or Recovery of Trace Metals"; Bulletin 2020; Bio-Rad Lab.: Richmond, CA, 1983. (1 1) "Standard Methods for the Examination of Water and Wastewater," 15th ed.; American Public Health Association, American Water Works Association and Water Pollution Control Federation: Washington, DC, 1980.
RECEIVED for review October 29, 1.984. Resubmitted and accepted February 25, 1985.
Determination of Iodine-I 31 at Low Concentrations in Formaldehyde-Preserved Milk Kar-Chun To* Radiation Laboratory, Kansas Department of Health and Environment, Office of Laboratory Services and Research, Topeka, Kansas 66620
Edward P. Rack Department of Chemistry, University of Nebraska--Lincoln, Lincoln, Nebraska 68588-0304 This paper describes a method for the analysis of total l3II
(tljz= 8.04 days) at low concentrations in milk in the presence 0003-2700/85/0357-1490$01.50/0
of formaldehyde which serves as a preservative. It has been found that when milk is preserved with formaldehyde, the 0 1985 American Chemical Society
