Measuring and testing – Sampler – sample handling – etc. – Analyzer supplier
Reexamination Certificate
1998-02-25
2001-02-27
Noland, Thomas P. (Department: 2856)
Measuring and testing
Sampler, sample handling, etc.
Analyzer supplier
C073S864840, C073S864330, C073S863000, C073S863310
Reexamination Certificate
active
06192768
ABSTRACT:
This invention relates to a sampling cell of flow-through type, a method for directing samples from such a sampling cell and use of such a sampling cell. The sampling cell is preferably manufactured by etching of silicon wafers. It is especially useful for continuous picovolume sampling in an analytical flow or for picovolume deposition of specific chemicals.
1. Background and Prior Art
Micro sample extraction is useful in e.g. fraction determination from protein separation systems. The sample extration and the fraction determination are tedious procedures, often including test tube matrix handling followed by analysis through e.g. gel electrophoresis before a final fraction identification is achieved.
Ref. 1 discloses a known sampling tool for fraction identification, being a flow-through cell comprising an orifice type nozzle and a piezo-ceramic disc glued onto a brass membrane. The brass membrane bends when a voltage is applied across the piezo-ceramic disc. The bending brass membrane creates a pressure pulse in a conical fluid-filled chamber which in turn transmits the pressure pulse onto a teflon membrane in the wall of the flow channel. Finally the pressure pulse, essentially unaffected, passes the teflon membrane and arrives in the fluid in the flow channel from which micro samples, i.e. small drops of the fluid, are ejected through the orifice type nozzle. This sampling tool is manufactured by conventional mechanical methods. This prior art sampling tool is schematically shown in the below
FIG. 1 and 2
.
Ref. 2 discloses an ink-drop generator comprising a piezo-ceramic layer generating a pressure pulse in a liquid-filled pressure channel. Anyhow this device is not of the flow-through type and can not be used for extracting samples from a continuous flow.
2. Advantages over Prior Art
The present invention relates to a sampling cell of flow-through type, i.e. a sampling cell with at least one flow inlet and at least one flow outlet from which samples are extracted from at least one sample emerging orifice, this orifice being separated from the flow inlet and the flow outlet. A sampling cell of flow-through type thus differs from other sampling cells, of non flow-through types, such as those wherein the flow outlet also serves as sample emerging orifice.
The above described tool for micro sampling according to Ref. 1 has some disadvantages, such as transmission of the pressure pulse through an intermediate chamber and through two separate membranes, rather large dead volumes, risk for sticking of pressure pulse absorbing bubbles within the tool due to the hollow part adjacent the orifice type nozzle, low resonance frequency due to the large overall dimensions of the tool, adherence of liquid to the area around the exit side of the orifice type nozzle, need for separate filling of the conical fluid-filled chamber, need for regular exchange of the teflon membrane, requirements for tightening around the teflon membrane, and comparably complicated and expensive manufacturing.
U.S. Pat. No. 5,338,688 (ROLF DEEG ET AL.) discloses a method for metered application of a biochemical analytical liquid to a target. Anyhow the device used is not of the flow-through type. Furthermore the method is limited to ejection of small liquid volumes through heating and subsequent evaporation of the liquid. Such heating may destroy the characteristics of the liquid.
U.S. Pat. No. 3,775,058 (BRIAN BUSH) discloses method and apparatus for mixing liquids. Anyhow the apparatus used is not of the flow-through type. Furthermore the apparaturs requires means for electrostatically charging droplets to be formed by the apparatus.
EP 119 573 A1 (MILES LABORATORIES, INC.) discloses microdroplet dispensing apparatus and method. Also in this reference the apparatus used is not of the flow-through type.
The sampling cell according to the present invention has inter alia the following advantages over prior art devices:
the sample emerging orifice (
6
) is placed directly in the wall of the flow channel, which provides for a very smooth channel, thus minimizing the risk for sticking of pressure pulse absorbing bubbles within the cell;
small dead volumes which implies small losses when changing the liquid in the flow channel (
3
), in turn being beneficial when expensive liquids to be analyzed are handled;
bandbroadening due to dead volume is reduced;
in the present silicon micro-machined sampling cell the pressure pulse is generated directly on the walls of the flow channel while in prior art flow-through cells, such as the cell according to Ref. 1, the actuating means act on a fluid chamber which in turn transmits the pressure pulse to the flow cell via a membrane;
small drops are often required. With the present silicon based sampling cell smaller drops can be generated than with prior art sampling cells. This is due to the fact that smaller and more precise holes can be made by etching in silicon than in cells being manufactured with conventional mechanical methods;
the sampling cell is preferably made entirely of silicon, which is a uniform, inert and biocompatible material being hydrophilic when oxidized;
the silicon parts may easily be chemically modified to adjust their surface properties.
OBJECTS OF THE INVENTION
A first object of the present invention is a sampling cell without the above disadvantages in accordance with claim
1
.
Further objects of the invention are different embodiments of the sampling cell of claim
1
.
Still further objects of the invention are different uses of the sampling cell and a method of directing samples emerging from the sampling cell.
REFERENCES:
patent: 3775058 (1973-11-01), Bush
patent: 5270212 (1993-12-01), Horiuchi et al.
patent: 5338688 (1994-08-01), Deeg et al.
patent: 5351563 (1994-10-01), Koppf et al.
patent: 5650577 (1997-07-01), Nagai et al.
patent: 5738133 (1998-04-01), Seki et al.
patent: 0119573 (1984-09-01), None
patent: 0268237 (1988-05-01), None
patent: 0668500 (1995-08-01), None
patent: WO9301485 (1993-01-01), None
Nilsson et al., Journal of Biochemical and Biophysical Methods, 27 181-190, (1993 month not given) “A flow-through microsampling device applied to an ion-exchange chromotography system”.
Drott Johan
Laurell Thomas
Nilsson Johan
Nilsson Staffan
Wallman Lars
Birch & Stewart Kolasch & Birch, LLP
Noland Thomas P.
Pharmacia Biotech AB
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