Anal. Chem. 1980, 52, 1310-1312
1310
Table 111. Titration of Benzyl Benzoate, Phenyl Salicylate, and Phthalic Anhydride with Lithium Silylamide
sample benzyl benzoate
phenyl salicylate phthalic anhydride
prepared molarity
experimen tally found molarity
0.210 0.0657 0.0976 0.145 0.145 0.00899
0.168 0.0477 0.0922 0.146 0.147 0.00949
error, %
92.0 27.0 4.5 0.7 1.4 5.6
Table IV. Titration of Some Nitrogen-Containing Compounds with Lithium Silylamide experi-
sample acetanilide ethylcarbamate
acetamide N-phenyl benzylamine caprolactam
prepared molarity 0.134 0.136 0.136 0.0280 0.136 0.140 0.0346 0.0974
0.110 0.151
mentally found molarity
error,
0.143 0.134 0.139 0.0303 0.146 0.129 0.0339 0.017 0.020 0.148
6.7 1.5 2.2 8.2 7.4 7.8 2.0 82.5 82.0 2.0
%
acetamide, and caprolactam behaved as monobasic acids. In general, the range in error appears to be somewhat greater for nitrogen compounds (2-870) than that for alcohols (1-570). N-Phenylbenzylamine is too weak an acid to be titrated. Carboxyacid amide and urea derivatives present little interference since the cleavage of carbanions such as amide anions is improbable. More experiments must be done before it can be said that all carbamates behave as monobasic acids when they are titrated with lithium silylamide (I). It should be noted
that diisopropylamide required more than one equivalent for titration of some carbamates because the reagent broke the acyl oxygen bond in addition to its reaction with the N-H moiety (8). Although the lithium silylamide reagent became darker in color over a period of one week, it changed neither in concentration within experimental error nor in its reactivity as long as it was stored under dry nitrogen in a glass stoppered bottle. Although experiments were not reported for the shelf life of lithium diisopropylamide, daily preparation of titrant was recommended. This was reported as a minor disadvantage in comparision to the time for the completion of analyses (8). In summary, lithium silylamide can be used to titrate alcohols, phenols, esters, ketones, and anhydrides. It can also be used to titrate nitrogenous compounds such as carbamates, ureas, and lactams. However, experiments need to be performed in order to see if it experiences side reactions with carbamates with phenoxy ester groups. The good precision and small time requirement for analyses are advantages over procedures which require saponification or steam distillations.
LITERATURE CITED (1) Kolthoff, I . M; Stenger, V. A. "Volumetric Analysis", Vol. I, 2nd ed.; Interscience: New vork, 1942;p 207. (2) Corwin, A. H.; Eilingson, R. C. J . Am. Cbem. SOC.1942, 6 4 , 2098. 131 Hiauchi. " ~ T.: .Zuck. D. A. J . Am. Cbem. Soc. 1951. 7 3 . 2676. i4j Higuchi, T.; Concha, J.; Kuramoto, -R. Aial. Cbem. 1952, 2 4 , 685. (5) Cluett, M. L. Anal. Cbem. 1962, 3 4 , 1491. (6) Haumesser W.; Gerhch, W.; Roder, C. Fresenius' 2.Anal. Cbem. 1977, 287,29 1. (7) Bauer, D.; Caillet, A. Analusis 1975, 3 , 440. (8) Haumesser, W.; Gerlach, W.; Roder, C-H. Fresenius' Z . Anal. Cbsm. 1970. 292. 23. (9) Amonoo-Neizer. E. H.: Shaw. R. A,: Skoolin. D.O.: Smith, B.C. Inora. Syn. 1966, 8 , 19. (IO) Seyferth, D.; Spohn, R. J. J . Am. Cbem. SOC. 1969, 91, 3037. (11) Jones, R. G.; Gilman, H. J . Org. Reactions. 1951, 6 , 352. (12) Torrey, H. A.; MacPherson, W . J . Am. Cbem. SOC. 1909, 3 1 , 582.
RECEIVED for review December 12, 1979. Accepted April 1, 1980. This investigation was supported in part by the National Science Foundation, Award No. SER 77-10894, and by the Robert A. Welch foundation, Grant No. 299.
Development of an Arsenic Trioxide Vapor and Arsine Sampling Train E. A. Crecelius" Battelle, Pacific Northwest Laboratory, Marine Research Laboratory, 5388 Washington Harbor Road, Sequim, Washington 98382
R. W. Sanders Battelle, Pacific NoChwest Laboratory, Richland, Washington 99352
A sampling train was evaluated using "As tracer for the measurement of particulate arsenic, arsine, and arsenic trioxide vapor in air and industrial process gas streams. I n this train, a demister was used to remove droplets of water and oil, and particulates were removed by a filter. Vapor arsenic trioxide was collected in an impinger solution, and arsine gas was collected on silvered quartz beads. Hydrogen sulfide gas did not reduce the arsine trapping efficiency of the silvered beads, and charcoal proved to be an effective trap for both arsine and arsenic trioxide vapor.
In the course of our field sampling of arsenic for speciation 0003-2700/80/0352-1310$01,00/0
studies, it became apparent that the validity of the existing methods were sometimes questionable. The original sample train consisted of a 0.5-pm polycarbonate sieve type filter, two 0.5 M NaOH impingers, and two dry gas traps loaded with silver plated quartz beads. Particulate arsenic greater than 0.5 wm would, in theory, collect on the filter, arsenic trioxide vapor would be retained by the impinger solution, and arsine gas would trap on the silver. Some problems encountered in the field were in sampling gas streams that contained water or oil mist. The oil had the tendency to plug the filters, and the water washed the particulate from the filters along with increasing the volume in the impinger. Adequate surface contact with the silvered traps was also of concern because surface coating of the silver by water or oil could interfere with CZ 1980 American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 52, NO. 8, JULY 1980 A1203 INSULATION
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Figure 1. Sampling train used for determination of particulate arsenic, arsine, and arsenic trioxide vapor in air
arsine adsorption. One sample site presented the problem of arsine saturation of both silvered traps. A laboratory study was therefore initiated t o establish the dependability of the trapping procedures and to develop a sampling train that would provide confidence in the field collected samples. Incorporated into this study were evaluations of new trapping matrices and application of instrumental neutron activation analysis and X-ray fluorescence as supplemental methods to the sodium borohydride reduction-dc arc emission arsenic analytical method.
EXPERIMENTAL The sampling train (Figure 1) consisted of a dry impinger for mist removal, a 47-mm diameter Fluoropore (0.5-pmTeflon fiiter) for particulates, two wet impingers in series (gas wash bottles) for arsenic trioxide vapor (As406),two silvered quartz bead traps in series for arsine, and a four-stage charcoal trap for arsine breakthrough of the silvered traps. All glassware was quartz with ground glass fittings for glass to glass connections. Teflon was used for inlet and outlet tubing. The temperature was controlled separately for the demister-filter section of the train and the traps section. In the laboratory experiments, the demister filter section was controlled at 75 f 2 "C and the arsine traps at 90 f 2 "C. The impingers for vapor arsenic trioxide were located outside the temperature controlled chamber and were at ambient temperature. Air flow through the train was 0.6 L/min-'. The impingers each contained 150 mL of solution. The silvered quartz beads (0.5-mm diameter) were prepared as described by Braman and Johnson ( I ) . Each arsine trap contained 3 g of coconut charcoal (Fisher Scientific) as this was found to have the lowest blank for arsenic. All chemicals were reagent grade. The arsenic vapor species were produced from 16As labeled compounds. Arsine was generated by sodium borohydride reduction of neutron activated sodium arsenite. Arsenic trioxide vapor was generated from neutron activated arsenic trioxide crystals (Baker and Adamson) in a 6-L glass chamber that was held at the same temperature as the demister and filter. Air leaving the arsenic vapor chamber was filtered (0.5 pm) before entering the demister. The concentration of arsenic collected by various traps in the sampling train was determined by gamma counting 76Asin a 4-.rr multidimensional counting system ( 2 ) . Although many of the laboratory experiments did not incorporate the complete sample train, field application was considered in all experiments. RESULTS A N D DISCUSSION A number of separate experiments were run to check the operation of various components of the sampling train. In
Table I. Retention of Aresenic Trioxide Vapor by Components of the Sampling Train components in series demister filter Teflon silver trap charcoal trap +1 charcoal trap # 2 back-up charcoal total
%
retained
pF
retained 1.20
2.60 0.13
0.06
0.13
0.05
0.80
0.37 44.00
96.30 0.04
