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ANALYTICAL CHEMISTRY, VOL. 60, NO. 2, JANUARY 15, 1988
5rnm Vacutao
exhaust
inlet
Figure 1. Vacutap sample bottle with cooling insert. The inlet tube diameter was about 1 mm. The inlet tube points slightly downward on the inside. The exhaust tube diameter was 5 mm. The cooling tube diameter was 10 mm.
As mentioned above, the cooling time was less than 1 min. For automating the procedure, suction can be applied for a fixed period of 1-1.5 min. After the tube is filled with liquid nitrogen up to level A, a mixture of gas and liquid flows from the inlet tube straight into the exhaust tube. When pumping is interrupted, no liquid remains above level A. Further suction only causes unnecessary loss of liquid nitrogen but eventually the pump may be damaged by embrittlement of interior parts. After completing a sample freeze-back it takes
about 1 min for the filling tube and the plastic tube connected to the exhaust to warm up sufficiently to be detached from the sample bottle. For testing the freeze-back procedure we used a Vacutap freeze-back bottle on our automated Nuclide stable isotope mass spectrometer. One sample of I O cm3 COz gas was analysed and frozen back automatically for 28 times. The spread in 613C (la)was 0.02%0,and no systematic change in isotopic ratio could be detected. The loss of COP,primarily due to pumping of the sample after freezing back, amounted to 3%, equivalent to 0.1% /cycle. The cause of this loss of COzis that part of the C 0 2 is condensed near level A indicated in the figure. As the system is pumped some COz escaping from this position due to a lowering of the liquid nitrogen level is pumped away instead of condensing on the lower part. If this is considered undesirable, some additional liquid nitrogen can be drawn into the tube during pumping. The consumption of liquid nitrogen was 30 cm3/cycle. The bottle described also can be used to automatically collect condensable gases such as COz and SO2 from preparation systems. Another useful application can be achieved by constructing U-shaped sample bottles with two Vacutaps and a cooling insert. Such sample bottles can be used to automatically trap the condensables from the effluent gas of gas chromatographs. Registry No. COz, 124-38-9.
LITERATURE CITED (1) Brenninkmeijer, C. A. M. I n t . J . Appl. Radlat. h o t . 1981, 32, 679-680. (2) Brennlnkmeijer, C. A. M. Anal. Chem. 1882, 54, 2622. (3) Brenninkmeijer, C. A. M. Thesis, Unlverslty of Groningen, The Netherlands, 1983. (4) Brennlnkmeijer, C. A. M.; Louwers, M. C. Anal. Chem. 1885, 57, 960. (5) Brenninkmeijer, C. A. M.; Morrison, P. D. Isot. Geosc. 1987, in press.
RECEIVED for review July 15,1987. Accepted September 14, 1987.
CORRECTION Ion-Pair Chromatographic Determination of Anions Using an Ultraviolet-AbsorbingCo-Ion in the Mobile Phase Brian A. Bidlingmeyer, Carmen T. Santasania, and F. Vincent Warren, Jr. (Anal. Chem. 1987,59, 1843-1849). In the Results and Discussion section, the first two sentences of the second paragraph should read as follows: The conductometric monitoring of the separation shown in Figure 1B is similar to one previously reported that used a “dynamically coated” reversed-phase column with a tetramethylammonium salicylate (TMA-SAL) eluent (33). In that work cetylpyridinium chloride was used to “coat” the bonded phase column prior to using the low conductivity, aqueous eluent of 0.5 mM TMA-SAL at pH 6.3. The following reference corrections should also be noted: (3)Dreux, M.; LaFosse, M.; Pequignot, M. Chromatographia 1982,15, 653. (15) Vera-Avila, L. E.; Caude, M.; Rosset, R. Analusis 1982, 10, 36. (33) Cassidy, R. M.; Elchuk, S. J. Chromatogr. 1983,262, 311.
