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ANALYTICAL CHEMISTRY, VOL. 51, NO. 1, JANUARY 1979
Irradiated Sample ( 2 weeks decay) HFIHNO, 3:l
1
Solution 1 1 H,BO, Solution 2 I
cox \
Eluant
_____.__
Column - - ...
Cr 54Mn 59Fe
"Rb 9'Nb
46sc
Ih9Yb
I3'Ba
I4'Ce
9rZr
6oCo
IWCs
"'Sm
lJiHf
51
b5
Zn
"* Ta
I4"La
152-iwEu
i
7
7
r
n
~
~
233pa
Afterwards, a modification in the procedure was introduced. Instead of using H,BO:, only as eluant, we added saturated H3B03 to the dissolved sample before loading the sample onto the column. This step is useful in cases where there is a precipitate of some insoluble fluoride after dissolution of the sample in HF medium; by formation of fluoride complexes, saturated H3B03allows the dissolution of that precipitate. This procedure also allows the use of normal vessels instead of Teflon vessels during the elution. Very interesting results were seen: %c '*'Hf, 233Paand the REE are quantitatively retained whereas oiher elements pass. The retention of '"Pa on the column allows the resolution of the 51Cr and elspa interference near 311 keV. On the other hand, Sc and REE do not impede the gamma spectra of lslHf or 233Pa,these radioelements being sufficiently active and having some other interference-free photopeaks.
'@Tb Figure 1. Proposed separation scheme
46Sc,"Zr, I4'Ce, '"Eu, '"Hf, and ""I'a were retained completely; 6oCo, "Rb, 95"b, ""Cs, and Ih'Ta passed directly in the eluate; 51Cr and "Fe were partially adsorbed; '"'Mn, retained in the beginning of the elution, began to pass partially in the eluate. Photopeaks of ""Zn (611 key, 1115 key) invisible before the removal of rare earth elements hecame visible in the eluate. The fact that "'Cr and "9Fe are partially adsorbed prompted us to look for another medium capahle of eluting these two ions completely. JVe tried various concent,rations of HCI and H,,B0,3. With HC1, "'cs and ""Fe are totally eluted. However "Sc begins to partition and, with saturated H:IRO,I.we obtained satisfactory results.
ACKNOWLEDGMENT Manuscript composition has been greatly improved by discussion with Y. Kasongo and M. Tshiashala, C.R.E.N.-K.
LITERATURE CITED (1) F. Girardi and E. Sabbioni. J . Radioanal. Chem., 1, 169 (1968) ( 2 ) G. H. Morrison and R. A. Nadkarni, J . Radioanal. Chem., 18, 153 (1973) (3) . . M. P. Menon and R. E. Wainerdi. Proc. Moder Trends in Activation Analvsis. Texas, 1965, p 152 (4) M. D. Tshiashala and 0. De Micheli Forma. RadioanalLett, 27, 101 (1976) ( 5 ) F. Girardi, R . Pietra, and E. Sabbioni. Techn. Rep. Eur. 4287e (1969)
RECEIVED for review ,July 24, 1978. Accepted August 11, 1978.
Vacuum Nebulizing Interface for Direct Coupling of Micro-Liquid Chromatograph and Mass Spectrometer Shin Tsuge" Department of Synthetic Chemistry, Faculty of Engineering, Nagoya University, Nagoya 464, Japan
Yukio Hirata and Tsugio Takeuchi School of Materials Science, Toyohashi University of Technology, Toyohashi 440, Japan
There has been an increasing interest in the direct coupling of a liquid chromatograph (LC) with a mass spectrometer (MS) (I -8). Among recent deLelopments in this field, are (1) moving wire ( I ) a n d moving belt (2). ('3) silicone membrane separator ( 3 ) ,( 3 )atmospheric preswre ionization (4,(4) direct introduction of a portion of t h e column effluent into t h e CT chamber (0-7), and (5) use of a jet separator for GC-MS (8). T h e latter two methods are similar to each other since hoth utilize t h e solvent vapor as the reagent gas for CI. However. both still have some disadvantages; in method 4, only a few percent of t h e effluent from a n ordinarv separation column is introduced into the ion source. and an uniform evaporation of t h e effluent is not always attained. while in method 5, relatively involatile compounds are difficult t o vaporize effectively with a conventional jet separator for GC-MS. T o overcome these problems, a new vacuum nebulizing interface for LAC-MScoupling was developed. With this interface, a more general system for I X - M S direct coupling can be established, where t h e wide range of flow rate of t h e solvent can be stably interfaced without any conventional splitting and even fairly Involatile compounds can effectively be introduced into t h e ion source a t relatively lower temperatures t h a n those required for nonnebulizing direct introduction. Further, this device is also quite effective for sample introduction of polar and/or large molecules of which 0003-2700/79/0351-0166$01 O O / O
mass spectra are otherwise difficult t o take (9).
EXPERIMENTAL Nebulizing Interface. A schematic diagram of the newly designed vacuum nebulizing interface is shown in Figure 1. The total effluent from a micro LC ranging between 2 and 16 pL/min was introduced into the nebulizer through a coaxial stainless steel capillary tube A (o.d.of 0.35 mm X i.d. of 0.15 mm with core-wire of 0.13 mm). The coaxial capillary nozzle is located at the center of the nebulizing tip F (i.d. of 0.4 mm). The top of the nozzle, however, is set about 0.3 mm above the nebulizing tip. Through a needle R , nebulizing gas of about 50 mL/min (at atmospheric pressure) was supplied to the nebulizer to form a jet stream at the narrow gap between the nozzle and the tip. The column effluent led to the top of the nozzle is continuously nebulized by the jet stream of He. Depending on experimental conditions such as the volatility of the solutes and boiling point and flow rate of the solvents. the nebulizing tube E (Pyrex) was heated to any desired temperature up to 300 "C, mostly to make up for the latent heat of vaporization of the solvents during nebulization. The distance between the nebulizing tip and the counter orifice (i.d. of O , , j mm) was adjusted to attain an optimum vapor pressure (ca. 1 Torr) at the CI chamber during full evacuation through G by a rotary pump at a rate of 170 L/min. For example, the optimum distances were about 2.0 and 2.5 mm for 16 pL/min of methanol and water solvent. respectively. In the following, only 16 pL/min of the flow rate was used, but it is possible to use higher '? 1978 American Chemical Society
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