Pipette and liquid transfer apparatus for dispensing liquid for analysis

A combination of a pipette and a liquid transfer apparatus is disclosed. The liquid transfer apparatus comprises a frame defining a liquid inlet aperture connected by a first passageway to a dispensing aperture, an air vent aperture connected by a second passageway that extends toward the first passageway, and a valve interposed between the two passageways to alternate between allowing continuous liquid flow along the first passageway, or continuous air flow along the second passageway and part of the first passageway.

FIELD OF THE INVENTION 
This invention relates to apparatus that allows any pipette to be used 
without careful control of manual positions, to accurately dispense small 
amounts of liquids for clinical analysis. 
BACKGROUND OF THE INVENTION 
The dispensing of aliquots of a body liquid such as blood serum onto a 
dried, slide like test element is a key first step in the analysis of the 
liquid in an analyzer. Because of the peculiar properties of many body 
liquids, and the need for accurate and reproducible dispensing of a 
predetermined aliquot, great care has been taken in prior art devices to 
ensure that (a) the proper tip is used by the dispensing apparatus to 
direct the flow properly, and/or (b) the dispensing tip is properly 
presented and positioned at the test element at the time of dispensing. 
Examples of the technology that achieve feature (a) include tips of the 
type described in U.S. Pat. No. 4,347,875. Examples of the technology used 
to achieve features (b) include dispensing means in analyzers of the type 
described in U.S. Pat. Nos. 4,340,390; 4,452,899 and 4,615,360. In the 
latter three, the analyzer is constructed, for example, to carefully 
prepare the dispensing tip Just prior to the dispensing, for example, in 
its spacing from the test element and/or by blowing off any exterior 
liquid hanging on the outside of the tip. 
Such care as expressed by such technologies has worked well. However, they 
all require expensive, peculiar apparatus that is costly either in its 
construction or its use. Although this is not particularly disadvantageous 
when constructing an expensive, high-volume analyzer, it is a drawback 
when constructing an inexpensive, low-volume analyzer, such as might be 
needed or used in remote field locations. 
Therefore, prior to this invention, there has been the need to provide an 
inexpensive interface that will allow a conventional pipette to dispense 
liquid that still flows onto the test element in a predictable, accurate 
manner. 
SUMMARY OF THE INVENTION 
I have constructed an interface and a method of using it that solve the 
aforementioned problems. 
More specifically, in accord with one aspect of the invention, there is 
provided a liquid transfer apparatus in combination with any pipette for 
manually receiving liquid from the pipette at an inlet aperture and for 
automatically dispensing that liquid at a dispensing aperture onto a test 
element. The transfer apparatus comprises: 
means defining an inlet aperture for liquid to be deposited into the 
apparatus, 
means defining a dispensing aperture for dispensing some of the liquid, 
means defining a first liquid flow path extending from the inlet aperture 
towards the dispensing aperture, 
means defining an air vent at the exterior of the apparatus and a second 
flow path extending from the vent towards the first flow path, 
and valve means interposed between the first and second flow paths for 
allowing continuous flow alternately from the inlet aperture to the 
aperture, or from the air vent to the dispensing aperture with the inlet 
aperture blocked. 
In accord with another aspect of the invention, there is provided a method 
of dispensing accurately a predetermined amount of liquid onto a test 
element, comprising the steps of 
(a) injecting more than the predetermined amount from any pipette into a 
liquid transfer apparatus of the type set forth in the previous paragraph, 
the valve means being adJusted to allow continuous flow of liquid from the 
inlet aperture to the dispensing aperture, 
(b) moving the valve means to block flow between the inlet aperture and the 
dispensing aperture and to fluidly connect the liquid adjacent the 
dispensing aperture with the air vent, and 
(c) applying an amount of air pressure to the air vent that is effective to 
accurately dispense the predetermined amount of liquid out of the 
dispensing aperture. 
Accordingly, it is an advantageous feature of the invention that any 
pipette can be used manually, and without careful control, to dispense 
accurate aliquots of a body liquid in the proper way onto a test element 
for assaying. 
It is a related advantageous feature that an inexpensive interface is 
provided that receives any pipette positioned without great care, and 
dispenses liquid received from the pipette in the proper way. 
Other advantageous features will become apparent upon reference to the 
following detailed description when read in light of the attached drawings 
.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The invention is hereinafter described with respect to the Preferred 
embodiments, which feature the use of particular kinds of valves to 
control the two flow paths to dispense preferably blood serum or a 
reference liquid. Additionally, the invention is useful regardless of the 
type of liquid being dispensed and with apparatus using other kinds of 
valves, so long as the valve is effective to allow either the one flow 
path or the other flow path to be effective. 
As shown in FIG. 1, the combination of the invention features a pipette 10 
and a liquid transfer apparatus 20. The pipette can be any pipette 
whatsoever, of any construction, conventional or otherwise, having a tip 
portion 12 with an outlet 14. Tip portion 12 can be fixed to or removable 
from the rest of the pipette. 
It is because of the interface provided by apparatus 20 that it does not 
matter what pipette is used. Apparatus 20 comprises a frame 22, which can 
be any shape, a rectangular slab being shown by way of example. Top 
surface 24 is constructed to engage the pipette and a source of .DELTA.P 
air pressure (not shown). A bottom surface 26, FIG. 2 is provided to 
supply a dispensing aperture 28 and a proper spacing from a test element 
E, FIG. 4, as described more hereinafter. 
More specifically, top surface 24 has an inlet aperture 30, FIG. 1, shaped 
to receive tip portion 12 directly, or to receive liquid ejected 
therefrom. Preferably, the pipette is actually inserted, to seat on a 
surface 32 at the bottom of aperture 30, FIG. 2. 
Aperture 30 fluidly connects with a fixed passageway 34, 35 that extends to 
an orifice 36 in surface 26. Valve 50 described hereinafter is disposed 
partway along passageway 34, 35. An appropriate dispensing tip 38 is 
mounted at orifice 36 to fluidly connect its aperture 28 with orifice 36. 
Any kind of tip 38 can be used, provided it is shaped to discourage 
perfusion up outside surface 40 thereof, and instead directs flow, such as 
a drop D, FIG. 4, onto the element. A useful example (not shown) is a tip 
configured as described in the aforesaid U.S. Pat. No. 4,347,875. 
A vent aperture 42 is provided, such as in top surface 24, FIG. 2, and 
fluidly connects with a passageway 44 that extends towards passageway 34. 
Preferably, passageway 44 has a width sufficiently large as to discourage 
capillary attraction of liquid out of passageway 56. 
Between the two passageways, valve 50 is interposed to allow, as 
alternatives, the completion of passageway 34-35 or the completion of 
passageway 44-35. A three way stop cock valve, here shown as cylindrically 
shaped, is useful. The valve comprises a cylinder 52, disposed in a bore 
53, having a diameter passageway 54, a radial passageway 56 dead-ending on 
and 90.degree. between passageway 54's outlets, and a handle means 58 
exterior of frame 22 for rotating the valve, FIG. 1. Appropriate seals, 
not shown, are included to prevent axial leakage along the cylinder. 
In use, valve 50 is rotated so as to appear as in FIG. 2, to connect 
passageway 34, 35 via passageway 54. As liquid is ejected from an inserted 
pipette, the liquid fills passageway 34, 35 until it reaches dispensing 
aperture 28. 
Thereafter, cylinder 52 is rotated, arrow 60 or 60', until passageway 54 is 
aligned with passageway 44, AND passageway 56 is aligned with passageway 
35, FIG. 3. Now valve 50 has blocked off the inlet aperture 30. The 
application of a pressure .DELTA.P at aperture 42 will cause the 
dispensing of an aliquot of the liquid from passageway 35 and tip 38, onto 
element E. Most preferably, .DELTA.P is generated from external air 
pressure delivered via means such as a hose, not shown, to aperture 42. 
(The hose is shaped to seal at aperture 42). 
To insure that the proper dispensing height h' is achieved, surface 26 is 
positioned the proper height h above the support surface 70 of element E. 
Any suitable mechanism can be used to obtain such heights. For example, a 
spacer block 72 can be utilized, which can be a separate element or can be 
an integral part of apparatus 20. 
Alternatively, apparatus 20 can be constructed to provide multiple transfer 
opportunities for a multiple number of pipettes containing each a 
different liquid, as is suggested in phantom, FIG. 1. That is, a plural 
number of passageways 34,35 can be provided in parallel, each with an 
inlet aperture 30, to accommodate a ganged pipette 10,10'. In such a 
construction, cylinder 52 can extend the full width of the entire device, 
so that handle means 58 is effective to rotate all the valves 
simultaneously. Such a construction is useful to allow the dispensing of, 
e.g., serum from pipette 10 and a reference liquid from pipette 10'. 
Particularly for such an example, the dispensing tips, of which only the 
first one 38 is depicted (FIG. 2), preferably would be spaced apart a 
distance w, FIG. 1, that would allow the simultaneous dispensing of serum 
and reference liquid onto a single ISE test element of the type shown in, 
e.g., U.S. Pat. No. 4,184,936. 
Alternatively, (not shown), each of the separate passageways 34,35 can be 
valved separately from the others, in which case cylinder 52 would not 
extend across the entire unit. Instead, each passageway 34,35 would have 
its own cylinder and own operating handle means 58. 
Still further, an additional option is to provide a temporary seal (not 
shown) over aperture 30 after liquid is inserted via the pipette, to allow 
storage in apparatus 20 before the dispensing step. 
By reason of this transfer apparatus, the user need not be concerned about 
whether the pipette 10 has a tip 12 that is particularly suited for 
accurate dispensing (that is, will discourage perfusion). Nor need the 
user carefully position the pipette relative to any particular vertical 
position, since apparatus 20 automatically provides the correct height h' 
between the dispensing orifice and element E, FIG. 3. In fact, tips 38 can 
be different in length, if plural units U are ganged together, FIG. 1, and 
if a different height h' is needed at the adjacent apertures. For example, 
liquid used for radial wash preferably is applied with a height that is 
less than h' for serum dispensing. 
It is not essential that the valve be a rotating type as shown. 
Alternatively, for example, it can be a spool valve, FIGS. 4-5B. Parts 
similar to those previously described bear the same reference numeral, to 
which the distinguishing suffix A is appended. 
Thus, FIG. 4, apparatus 20A comprises a frame 22A providing a top surface 
24A in which an inlet aperture 30A and a vent aperture 42A are provided, 
as in the previous embodiment. A passageway 34A,35A fluidly connects 
apertures 30A and 42A with a dispensing aperture 28A, via a valve 50A, 
also as in the previous embodiment. However, in this embodiment, valve 50A 
is a spool valve comprising a cylinder 52A that slides, rather than 
rotates, within bore 53A. Outer diameter OD.sub.1, FIG. 5A, seals within 
bore 53A, whereas a reduced inner diameter OD.sub.2 is provided at two 
locations 80,82 spaced apart along axis 84 of cylinder 52A. The spacing of 
locations 80 and 82 is constructed to be less than the spacing "x", FIG. 
4, of passageway 34A from passageway 44A that extends from the vent 
aperture 42A. In this embodiment, passageway 44A does not feed into the 
extension of passageway 34A,35A that occurs within the valve, but rather 
joins passageway 35A downstream from valve 50A. That is, there is no 
intersection of the air path and liquid path within the valve, as in the 
previous embodiment, but rather downstream thereof. 
In use, cylinder 52A is slid so that reduced diameter OD.sub.2 at location 
80 is aligned with passageway 34A,35A, FIG. 5A, and liquid is inserted 
from the pipette (not shown), to provide continuous flow towards the 
dispensing aperture, arrow 90. In this position, cylinder 52A has OD.sub.2 
at location 82 misaligned with air passageway 44A. Thereafter, valve 50A 
is moved, using handle 58A, FIG. 4, by 5 sliding cylinder 50A sideways, 
arrow 92, FIG. 5B, so that outer diameter OD.sub.1 blocks any flow from 
passageway 34A to 35A, and at the same time OD.sub.1 at location 82 
becomes aligned with the parts of passageway 44A. This allows air pressure 
to flow continuously, arrow 94, from the air vent to passageway 35A, FIG. 
4, and hence, to the liquid therein. That is, when valve 50A is positioned 
as shown in FIG. 5B, air pressure is applied continuously in an amount 
effective to accurately dispense a predetermined aliquot, for example 10 
.mu.l, of liquid out of the dispensing aperture. 
Passageway 35A can be serpentine in its construction, as shown in FIG. 4, 
or it can be more linear in the manner of its construction shown in FIG. 
2. 
The invention has been described in detail with particular reference to 
certain preferred embodiments thereof, but it will be understood that 
variations and modifications can be effected within the spirit and scope 
of the invention.