Preservation of Mercury in Polyethylene Containers Samuel Paul Piccolino 861 New Scotland Avenue, Albany, NY 12208 persulfate in sulfuric acid. Mercuric ions are reduced with stannous chloride to the element state and the mercury vapor passed through a cell positioned in the light path of the atomic absorption spectrophotometer. The time of initial analyses is t = 0. Analyses were performed in duplicate, i.e., a morning and afternoon run on each test day. Analyses were carried out on the first four days ( t o- t g )and twice a week, thereafter. Ample calibration standards, standard reference samules, and reagent blanks were analyzed throughout all runs & insure good calibration points.
Water samples are often stored prior to analyses in polyethvlene containers. and anv minute loss of mercury during. storage is significant since measurements are made at the part Der billion level. In mv research, I have been successful in finding a preservative which my data demonstrates to he necessary and effective a t this concentration level. Experimental All glassware and polyethylene bottles were soaked overnight in 10%nitric acid and rinsed with deionized water immediately before use. A glass jug was filled with 12 L of tap water and 3 L of raw water. From this water reservoir, six glass volumetric flasks ( 2 L) were filled and each flask contained one of the corresponding preservatives that follow: 1) 0.15% HNOs 2) 0.15% H N 0 3 3) 0.5 % HNOs 4) 0.5 % HNOa 5) 0.5 % HNOs
Conclusion The graph and Table 1, that follow, show that there is no significant mercury loss from t = 0 t o t = 45 with either 0.5% H N 0 3 0.05% KzCrz07 or 0.5% H N 0 3 0.05% KMn04 as preservatives. Comparison of the standard deviation of the data set for each treatment for 45 days to the published single operator precision indicates that preservatives 2,4, and 5 are suitable. (Table 2. Statistical Data.) In summary, the results reported here are positive and definitelv favor the use of 0.5% HNOl with an oxidant to preserve samples for mercury analyses.
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Next, 24 half-liter glass flasks were arranged in six groups of four, each group containing a flask to have 0 @g/L,1 fig/L, 4 pg/L, and 7 pg/L of mercury, respectively. HgC12 and CHaHgCI contribute 50% each to the total mercury concentrations. These flasks were brought to volume with the preservative-water from the corresponding 2-L flask prepared earlier. These mercury-preservative-water solutions were transferred to corresponding half-liter polyethylene hottles. Samples ( 2 4 ) were then analyzed for mercury using the automated spectrophotometric method, consisting of digestion of the sample with potassium dichromate and potassium
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Table 1. Summary of Data (fromGraph) Aner Time (t) (days)
% Hg Loss
Treatment NOtreatment 0.15 % HNO. 0.5 % HN03 0.15 % HNO. 0.5 % HNO* 0.5 % HN05
48 10 7 7 0 0
+ 0.05 % KzCr207 + 0.05 % K~CTZOI + 0.05 % KMnO4
lr h4 f2 7
tm 45
Ls
Table 2. Statistical Data
-
Treatment Hg K!/L
-
0.15% HNOa
0.15% HN03
+ 0.05% CrzO7'-
0.5% HN03
0.5 % HN03 +0.05% Cr20i2-
0.5 % HN0s +0.05% Mn044
7
1
4
7
(0.96) 1.0
3.9
7.0
0.52
1.9
2.7
6.7
(10) 2.2
4.4
7.6
0.8
3.6
6.2
0.32
0.31
(0.21) 0.32
0.23
0.34
0.15
0.96
1.8
0.16
0.40
0.15
0.14
0.17
0.44
2.0
4.0
1
4
7
1
4
7
1
4
7
1
4
7
Mean (F)
0.74
3.1
5.6
091
3.7
6.5
0.80
3.4
5.7
0.98
3.9
6.6
Range: maxa
10
4.3
7.1
1.0
4.2
7.0
1.0
4.0
6.9
1.2
4.5
Std. deviationE
0.20
0.48
0.59
0.13
0.23
0.40
0.14
0.32
0.66
0.15
Meandifferenced
0.26
0.92
1.3
0.10
0.24
0.45
0.18
0.61
1.2
0.07
'Range max: for values from to - t3 a Range mi": for values fro", - t , ~ C Analyfical precision. ~ i n g l e operator (.'Methods for Chemica' Analysis of Water and Wastes," USEPA. 1974, p. 130) @ 1 &g/L = "~ean dinereme = ( ~ x ~ e c t eConc. d - W N ; where: i , =means conc. for day "i" and N = the number of d u e s in thedataset.
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Volume 60
1
Control
*
0.07. 4 &glL = -t0.16, 7 M I L =
Number 3
*
March 1983
0.28.
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