The present invention relates to liquid sam¬ ple analysis apparatus which uses a sampling probe to deliver liquids from a sample container to the analy¬ sis equipment. More particularly, the invention re¬ lates to an improved system for cleaning of the probe between samples in order to reduce carry-over of mate¬ rials from one sample to the next. Background Art

Various systems are available for the analy¬ sis of liquids, for example, body liquids which need to be quantitatively analyzed with respect to specific ingredients. One such system known as the Paramax Analytic System is fully shown and fully described in U.S. Patent 4,528,159 (Liston) issued July 9, 1985. Such analysis systems generally include a probe whic enters the sample container such as a test tube either through the open top thereof or by temporarily enter- ing through the closure, for example, by puncturing a rubber stopper to form a temporary opening. See, for example, U.S. Patent 4,951,512 (Mazza et al.) issued August 28, 1990.

Reusable probes that are used to deliver aliquots from successive containers such as blood col-

lection tubes or liquid reagent vessels are a source of intra-sample carryover or contamination. In order to minimize contamination and carry-over between sam¬ ples, it has been conventional to flush the probe with a diluent liquid such as water, for example, as de¬ scribed in the Liston patent. Another technique shown, for example, in U.S. Patent 3,266,322 (Negersmith et al.) issued August 16, 1966, has en¬ tailed aspiration of air through the probe by means of a vacuum pump or the aspirating pump used to withdraw the sample liquid from the sample container. Such aspiration, however, introduces the possibility of drawing the unwanted carry-over contaminants deeper into the tubing and apparatus which comprises the sam- pliήg system. It has also been proposed to utilize a separate probe wash sleeve through which a pressurized rinse liquid is flushed. See for example U.S. Patent No. 4,756,201 (Uffenheimer) granted July 12, 1988. In light of these existing probe wash systems, a need has continued to exist for an improved method and appara¬ tus for effectively cleaning such probes. Summary of the Invention

The principal object of the invention is to provide a new probe wash system that substantially reduces carryover between samples aspirated by the probe. An important aspect of the invention is to provide a probe wash in which a turbulent flow is cre¬ ated in the probe by means of a simultaneous introduc¬ tion of pressurized air and water. Alternatively such turbulent flow is created by introduction of bursts of the air and water in rapid sequence. A related aspect of the invention involves the use of a pressurized gas stream of short duration to blow the residue of the previous sample out of the probe prior to washing with additional diluent liquid.

The probe wash system further provides a segmented stream of air and water (or other gas and liquid) that effects thorough cleaning of the probe and its associated flow paths. An optional aspect of the invention relates to providing a cleaning method in which the air flowpath may be backflushed with dil¬ uent water at the end of the cleaning cycle thereby removing air from the system that could interfere with use of the probe in the next aspiration cycle. A further aspect of the invention relates to providing a waste receptacle to receive wash liquids from the probe, which receptacle is provided with an inlet opening and, optionally, a vent opening, each of which are provided with means to prevent discharge of aerosols into the atmosphere during the probe washing cycle.

Briefly summarized, the invention provides an improved system for cleaning a probe used for aspi¬ rating successive aliquots of liquid from successive containers. The improved means for cleaning said probe between aspiration of the successive aliquots includes a source of diluent liquid such as water which is connected to probe by means of a first fluid ^• flow path. Means such as a syringe pump is provided for pumping the diluent into the fluid flow path and to the probe. Appropriate control circuitry is pro¬ vided in order to control the time intervals during which the pump is activated. A source of pressurized gas such as air is connected by a second fluid flow path to the first fluid flow path, at a point interme¬ diate to the probe and the source of diluent liquid. A valve, preferably solenoid controlled, is provided to control the flow of gas to the probe.

In a preferred embodiment of the invention, a waste collection receptacle or chamber is included

which is provided with an opening in its top for re¬ ceiving the probe during the cleaning cycle. This opening is preferably provided with a filament or brush that is saturated with water to prevent the es- cape of aerosols from the waste receptacle. The cham¬ ber is also provided with a filtered outlet for ex¬ haust of gases therefrom, which is important to the proper function of the air purge effected by the in¬ vention. A further aspect of the invention includes means for moving said chamber and said probe relative to each other whereby the probe is inserted through said opening during the cleaning cycle and removed therefrom during a liquid aliquot aspiration cycle. Such motion is provided either by raising of the cham¬ ber toward the probe or alternatively by lowering of the probe into the chamber.

Another important aspect of the invention pertains to a method of cleaning a probe, after it has been used to aspirate and dispense a liquid, utilizing the apparatus of the invention. This aspect further contemplates a specific, controlled, rapid sequence of steps. These steps of the wash cycle include (1) opening the wash valve to cause pressurized gas to flow out through the probe, (2) resuming the pumping of diluent while continuing the flow of gas through the probe, (3) closing the valve while continuing the pumping of diluent to re-fill the probe with diluent, and (4) discontinuing the flow of liquid diluent. The probe can then be used for the next liquid aliquot aspiration cycle and the wash cycle repeated thereaf¬ ter. Brief Description of the Drawings

For more complete understanding of the in- vention reference is made to the embodiment illustrat-

ed in greater detail in the accompanying drawings and the following detailed description.

Figure 1 is a perspective view of a probe of the type used in a liquid sampling system showing a stoppered container of the type in conjunction with which the probe is typically used and a waste recepta¬ cle;

Figure 2 is a diagrammatic view illustrating a preferred fluid flow path used in conjunction with the invention;

Figure 3 is a diagrammatic cross-sectional view illustrating a probe of the invention in conjunc¬ tion with a waste collection chamber;

Figure 4 is a top view of a waste collection chamber illustrating a different form of top closure;

Figure 5 is a cross-sectional side view of yet another alternative form of a top for the waste collection chamber of Figure 3; and,

Figure 6 is a diagram in chart form illus- trating a sequence of steps used to clean a probe in accordance with the invention. Detailed Description

Referring first to Figure 1 there is seen a probe 10 adapted to enter the interior of a container such as a glass tube 12 which contains a liquid sample 14. Container 12 can be positioned upon a lift plat¬ form 16 which is adapted to raise the stoppered con¬ tainer. A puncture tube 20 which includes a non-cor¬ ing, hollow needle is disposed above container 12 so that it will puncture stoppered end 15 of container 12 when the container is raised. A boom assembly 22 can be provided to lower probe 10 through puncture tube 20 into the interior of container 12 where fluid 14 can be aspirated into probe 10. As seen in the embodiment of Figure 1, probe

10 is connected by fluid flow path 24 to a syringe pump 26 (and optionally an additional syringe pump 27) , see Figure 2, which supplies a diluent liquid 25, such as water, to the probe. An air pump 28 is also connected by means of a flow path 29 and T-connection 31 to the fluid flow path 24. A solenoid controlled valve 30 is positioned between air pump 28 and the T- connection 31.

In the alternate embodiment illustrated in Figure 2, a solenoid-controlled valve 31 is used in¬ stead of a separate T-connection, as, with this ar¬ rangement, the function of the T-connection is per¬ formed by the valve. Fluid flow path 29a is supplied with air from a suitable supply 33, with the pressure and flow rate thereof being controlled by means of an air accumulator 34.

A waste receiving container 35 is positioned at a location such that probe 10 can be pivoted thereover and lowered therein through a probe receiv- ing opening 36. Waste receptacle 35, best seen in Figure 3, is preferably provided with air venting opening 37, which is provided with a hydrophobic air filter 38 to minimize escape of atomized liquids into the atmosphere, while permitting free escape of air from the waste receptacle. Filter 38 can be formed, for example, from an expanded polytetrafluoroethylene fibrous web or membrane. A drain opening 39 con¬ trolled by valves of conventional design (not shown) is provided for drainage of waste fluid 40 from the bottom of waste receptacle 35. Drainage may be accom¬ plished by gravity flow. Vent opening 37 can be omit¬ ted in its entirety if opening 39 is of a size large enough to permit efficient venting of gases from re¬ ceptacle 35. The top of waste receptacle 35 provided with

a water-saturated closure 42, which performs the dual functions of cleaning the outside of probe 10 and pre¬ venting escape of aerosols. Closure 42 can, alterna¬ tively, be formed from bristles 43, a woven fabric 44, or non-woven fabric 45. Closure 42 is kept in a satu¬ rated condition by means of liquid 47 which is caused to flow through flow path 48 by means of a suitable pump 49. Fluid 47 is preferably water, but can, de¬ pending on the type of fluid being handled by probe 10, constitute or contain a disinfectant material.

In operation the effectiveness of the probe wash is enhanced by nearly simultaneous introduction of pressurized air and water which creates a turbulent flow. A segmented stream is created in flow path 24 by rapidly causing a burst of air to flow through the probe, followed by diluent liquid. The timing of the air flow to the probe, controlled by solenoid valve 30 or 31 is also such that flow path 24 will be filled with diluent liquid at the end of the wash cycle. The absence of air is critical to the normal system per¬ formance.

As illustrated in Figure 6, a rapid, timed sequence of steps is used in the preferred backflushing procedure. In Figure 6 the time inter- vals t.l to t ₀ , t ₀ to t _1# t _x to t ₂ , etc . are preferably in the range of 0.5 to 1.0 second. As seen in Figure 6, at time t^ the boom 22 will lower the sample probe 10 into waste receptacle 35 so that the tip of the probe is roughly 0.4 inch into the waste receptacle. Then, at t ₀ the syringe pump will charge flow path 24 with diluent. At time t _λ the air valve is activated to force air through the system thus forcing contaminated fluid out into waste receptacle 35. Pressurized air is vented out of the waste receptacle 35 through vent filter 38. At time t ₂ the syringe will start to pump

liquid through the system. At time t ₃ , the air pump will turn off, allowing fluid to be pumped through all legs of T-coupling 31. At time t ₃ the solenoid valve turns off allowing the remaining liquid to flush any remaining air out of the tip of probe 10. At any time while the probe 10 is in waste receptacle 35 the pump 49 will flood closure 42 with liquid 47 to clean the exterior of probe tip 10. At t ₅ the flow of diluent liquid is discontinued and the probe is raised out of the waste receptacle.

When the probe wash of this invention is used to clean a probe that is used to aspirate a liq¬ uid reagent rather than samples of liquids such as bodily fluids, it will be apparent that a stoppered tube would not be used as shown in the drawings. Rather the probe would be inserted into a suitable receptacle, which may have an open top, for aspiration of the desired reagent. The probe wash system of this invention is readily adapted to such applications. The particular sequence or timing of wash steps also can be varied somewhat, as will be readily apparent to those skilled in the art. Modification of other aspects of the procedure may also be made with¬ out departing from the spirit of the invention.