US 3863599 A
An applicator for forming a colinear array of spaced liquid sample streaks on a substrate for conducting parallel electrophoretic or chromatographic runs on such samples comprises a body supporting an array of aligned applicating strands of, e.g., stainless steel foil, in a manner enabling the individual strands to be dipped in liquid samples to pick-up a coating of liquid on each to be transferred to a substrate. The strands are preferably individually resiliently supported on the body so as to be self-aligning with the surface of a substrate against which the strands are pressed. The applicator is an adaptation of that of U.S. Pat. No. 3,505,858 to overcome the special difficulties in forming reproducible streaks of certain sample liquids, particularly haemoglobin extracted from whole blood.
Description (OCR text may contain errors)
nite States Patent [1 1 Kohn [451 Feb. 4, 1975  Assignee: Shandon Southern Instruments Limited, Surrey, England  Filed: Jan. 23, 1974  App]. No.: 435,722
 Foreign Application Priority Data Jan. 23, 1973 Great Britain 3431/73  U.S. Cl 118/256, ll8/221, ll8/225, 118/255  Int. Cl. B05c 1/06  Field of Search 118/216, 221, 255, 256, ll8/242, 243,219, 225; 33/41 D, 44
 References Cited UNITED STATES PATENTS 65,948 6/1867 Rile 118/221 2,656,605 10/1953 Schlieder 33/4l D 3,505,858 4/1970 Kohn 73/61.] C
Primary Examiner-Mervin Stein Assistant Examiner-Douglas A. Salser Attorney, Agent, or Firm-Kurt Kelman  ABSTRACT An applicator for forming a colinear array of spaced liquid sample streaks on a substrate for conducting parallel electrophoretic or chromatographic runs on such samples comprises a body supporting an array of aligned applicating strands of, eg, stainless steel foil. in a manner enabling the individual strands to be dipped in liquid samples to pick-up a coating of liquid on each to be transferred to a substrate. The strands are preferably individually resiliently supported on the body so as to be self-aligning with the surface of a substrate against which the strands are pressed. The applicator is an adaptation of that of U.S. Pat. No. 3,505,858 to overcome the special difficulties in forming reproducible streaks of certain sample liquids, particularly haemoglobin extracted from whole blood.
7 Claims, 3 Drawing Figures PATENTED FEB 1 APPLICATOR MEANS FIELD OF THE INVENTION The invention relates to applicators and is specifically concerned with an applicator for forming a colinear array of spaced liquid sample streaks on a substrate.
In techniques such as electrophoresis and chromatography the constituents of a sample are caused to travel along a substrate. In general, different sample constituents travel at different speeds under the same conditions so that, in the course of a run, the different constituents of a sample become spatially separated along the path of their travel from a common origin. In certain applications of these techniques the results of a run performed upon a sample of unknown composition are directly compared with the corresponding results of a calibration run performed under the same conditions upon a sample of known composition, in order to identify constituents of the sample of unknown composition. In order to provide for a valid comparison of the respective results, however, the conditions under which the respective runs are conducted must be identical: this is most conveniently accomplished in practice by conducting the runs in parallel. For this and other reasons, therefore, it is often desired to conduct parallel runs simultaneously on a number of different samples.
The substrate is normally prepared for conducting a set of parallel runs by forming streaks of the different samples on the surface at one end of the substrate. The streaks are normally arranged in a colinear array extending at right angles to the direction in which constituents of the streaks are to travel during the runs. The different constituents travel from the streaks to form discrete bands. To ensure spatial separation, in the direction of travel, of the bands of constituents which travel at only slightly differing speeds it is important that the streaks which constitute the origins of the runs should have negligible width. Inevitably some spreading of the streaks in the direction of travel occurs but by arranging for the streaks initially to have negligible width the bands of constituents travelling at nearly the same speed have the best chance of becoming suitably separated by the time that the band of the fastest travelling constituent approaches the end of the substrateremote from the streaks.
BACKGROUND TO THE INVENTION AND THE PRIOR ART At one time it was proposed to apply different samples to a substrate for such purposes in streaks of approximately the same length and of little width by the use of an applicator comprising a pair of parallel wires arranged side by side. This simple applicator was to be dipped into a sample liquid a portion of which would adhere to, and distribute itself uniformly between, the two wires by capillarity so as to form a liquid body having constant volume per unit length. The two wires were then to be placed on the substrate at the position where the streak was to be formed, so that at least a proportion of the liquid between the wires would be transferred to the substrate and form on it a sample streak having substantially constant liquid volume per unit length of the streak. Such an applicator could only form one streak at a time and had to be cleaned before reuse to form the next required adjacent streak on the substrate.
Obviously the use of such a simple applicator would be tedious and time-consuming especially if several runs on each sample were to be performed on several substrates simultaneously. Kohn U.S. Pat. No. 3505858 discloses an applicator for the purposes discussed above which avoids the difficulties in use and the disadvantages of the above-described simple parallel wire applicator, the applicator the subject of the said Patent comprising an elongated plate-like body provided in one longitudinal edge thereof with a plurality of cutouts which separate said longitudinal edge into a plurality of longitudinally spaced discrete castellations, said castellations having elongated edge-elements disposed in longitudinal alignment, said edge-elements being provided with liquid-holding channels of uniform crosssection extending longitudinally in the edge-elements.
Applicators constructed in accordance with the said Patent have proved very convenient and simple to use and their use has been found to be conducive to the easy obtainment of highly reproducible results in the various analytical techniques involving their use.
In such an applicator, the edge-elements are intended to reproduce, functionally, the spaced parallel wires of the simple previously proposed applicator discussed above. Thus, the liquid-holding channels in the edgeelements are broadly equivalent in function to the gap between the spaced parallel wires of the simple applicator and retain liquid by capillarity. The channels may be formed by grooves in the face of elements of the applicating edge or they may be constituted by gaps formed between spaced pairs of parallel members defining the edge-elements.
For most purposes, the edge-elements and their liquid-holding channels of an applicator constructed as taught by the said Patent serve reliably to pick-up a reasonably standard quantity of sample liquid and to transfer this to a substrate against which the applicating edge is lightly touched. However, for some purposes and with some sample liquids, notably haemoglobin extracted from whole blood, the performance of such an applicator is not entirely satisfactory and better reproducibility of performance would be desirable. An object of the present invention is, therefore, to provide a modification of the applicator of the said U.S. Pat. No. 3505858 which, for the purposes indicated, avoids at least substantially the abovediscussed performance limitations of the applicator of the said Patent.
THE INVENTION An applicator in accordance with the present invention is based upon the concept of utilising a single linear strand, such as a wire or a thin, narrow strip, as an edge-element, it having been found that in the case of the sample liquids under consideration, such as haemoglobin, an isolated linear strand when dipped into such a liquid will pick-up a coating that is substantially uniform along the length of the strand and will release such coating or a proportion thereof uniformly to a substrate against which the strand is lightly pressed.
An applicator in accordance with the present invention thus comprises a body and supporting an array of colinear spaced-apart applicating strands of similar dimension spaced from the body and freely suspended therefrom by support members engaging solely the ends of the strands.
In presently preferred embodiments of the invention each applicating strand is formed as a part of an integral assembly including a pair of end support members by which the strand is attached to the said body. Thus, for example, each said strand may consist of the reduced-width central portion of the length of an elongated strip, the end portions of which are bent parallel to one another at right angles to the strand-constituting central portion. Conveniently integral strands and support member assemblies of this form are made of stainless steel strip.
When the individual strands are integrally formed with end support members, each assembly of strand and end support members may be arranged for individual mounting on the said body so as to allow for positional adjustment of individual assemblies and for replacement of damaged assemblies should this become necessary. Thus, for instance, the body may comprise a stainless steel or similar blade which may or may not be provided with finger pieces or other means to facilitate its handling, this strip being fitted adjacent to one long edge thereof with a mounting block formed with pairs of apertures to receive, as a push fit, the end support members of integral strand and support member assemblies. The mounting block may conveniently be formed of plastics material, for instance methylmethacrylate or the like, and desirably the apertures therein consist of through-bores to facilitate thorough cleansing of the individual strands and their support members.
Preferably, however, the said body comprises an elongated rectangular section block of, e.g., a suitable plastics material having a rectangular slot to receive a set'of mounting blocks each fitted with an individual strand and its end support members, the mounting blocks being a sliding fit in the body and abutting against resilient means therein so that relative movement of the mounting blocks may occur to align the several strands in the plane of a substrate when pressed thereagainst.
To aid retention of the support members, of integral strand and support member assemblies, in common or individual mounting blocks, the support members may have barbed or serrated edges.
The dimensions of the strands of an applicator in accordance with the invention determine its performance and, in particular, the amount of liquid which such a strand will pick-up and transfer to a substrate; moreover, the nature of the liquid will affect the amount thereof picked-up and transferred by a strand of given dimensions. It has been found that for haemoglobin extracted from whole blood, a strand formed from stainless steel strip having a thickness of 0.005 inch and a width of 0.010 inch is suitable, a strand of length 0.200 inch between support members at right angles thereto being suitable to transfer appropriate amounts of haemoglobin samples to a substrate to form a streak of negligible width thereon.
THE DRAWING The drawing illustrates, by way of example, a preferred embodiment of the invention. In the drawing:
FIG. 1 is a front threequarter perspective view of an applicator, in accordance with a preferred embodiment of the invention, with parts broken away to show internal details; I
FIG. 2 is a rear threequarter perspective view of the applicator, on a reduced scale; and
FIG. 3 is a plan view of a blank from which an integral strand and support assembly is formed for the applicator of FIGS. 1 and 2.
DESCRIPTION OF PREFERRED EMBODIMENT The applicator shown in the drawing comprises a body 1 in the form of a block of elongated rectangular section having a rectangular slot 2 formed by a recess in one large face of the block and extending into one narrow face thereof, so that for most of its length the block 1 is of inverted L" section. The recessed large face of the block I is covered by a mainplate 3 fixed to the block by means of setscrews 4. The mainplate 3 has a flange which covers the recessed narrow face of the block 1 and is slotted for a purpose to be described. The block 1 may be formed of metal or a suitable plastics material, e.g., polymethylmethacrylate, and the mainplate 3 may be formed of stainless steel.
A set of mounting blocks 5 is accommodated within the slot 2 in the block I, the blocks 5 being rectangular and dimensioned to be a sliding fit in the slot 2 defined by the recess and the mainplate 3. Each mounting block 5 has an individual spring 6 acting between the base of the slot and the block 5 to urge the latter towards the recessed narrow face of the block 1 and into abutment with the inner face of the flange of the mainplate 3.
Each mounting block 5 is fitted with a strand assembly comprising a stainless steel ribbon-like strand 7 integrally formed with a pair of end support members 8 extending parallel with one another and at right angles to the plane and length of the strand 7. Each strand assembly is formed by bending a blank of the configuration shown in FIG. 3. As shown, the blank, which is conveniently a stamping of stainless steel foil 0.005 inch thick, has a central portion constituting the strand 7 with a length of, e.g., 0.200 inch and a width of 0.010 inch and end portions constituting the end support members 8, the said end portions each having an overall length of about 0.400 inch and a width which increases over a distance of about 0.100 inch from the strand width of 0.010 inch to a nominal width of about 0.070 inch with sets of barbs 9 having an overall width of about 0.095 inch.
Each mounting block 5 has transverse slots (not shown) into which the barbed ends of the end support members 8 are pushed so that these members 8 support the strand 7 of the associated assembly substantially parallel with the recessed narrow face of the block 1. The slots in the flange of the mainplate 3 are disposed in register with the respective strand assemblies so that each projects through the mainplate flange.
A spring-loaded guard 10 of channel section with a slotted web straddles the recessed narrow face of the block 1 and overlies the strand assemblies projecting therefrom. The guard 10 is secured by plungers ll movable in bores in the block 1, springs 12 seating in counterbores and surrounding the plungers ll acting against the inside face of the guard 10 to urge this away from the block 1 into a position in which it encloses the strand assemblies.
The mainplate 3 is fitted with finger pieces 13 by means of which the applicator may be manipulated. The rear face of the block 1 is fitted with dowels l4 and a headed peg 15 by means of which the applicator may, if desired, be fitted to a holder, for instance the end of an arm hinged over a base plate having a movable table.
The illustrated applicator may be used in generally the same manner as the applicator of the said US. Pat. No. 3505858. Thus it may be used in conjunction with a pallet comprising a rectangular flat dish with a line of stations formed by recesses in one face, these recesses corresponding in size and position to the strands of the applicator so that the applicator strands may be introduced into the recesses simultaneously, each to pick-up a sample ofliquid from the individual recess into which it is introduced. With its strands charged with samples. the applicator may then be moved into light contact with a substrate so that each strand deposits a sample as a thin line on the substrate. Except when deliberately pressed against a substrate or a pallet, when it retracts to permit the strands 7 to project through the slot in its web, the guard 10 encloses the strands and protects these from inadvertent contamination or damage. The springs 6 of the mounting blocks 5 enable these to move as required for the strands 7 to align with a substrate when pressed thereagainst.
1. An applicator for forming on a substrate a number of spaced colinear liquid streaks each having substan' tially the same volume of liquid per unit length. comprising a body, an array of colinear spaced-apart liquidholding and applicating strands of similar dimension spaced from the body, and support members freely suspending the strands from the body and engaging solely the ends of the strands.
2. An applicator for forming on a substrate a number of spaced colinear liquid streaks each having substantially the same volume of liquid per unit length, comprising a body and an array of colinear spaced-apart applicating strands of similar dimenion, each of the strands being part of an integral assembly including a pair of end support members by which the strand is at tached to the body to be held spaced therefrom.
3. The applicator of claim 2, in which each said strand consists of the reduced-width central portion of the length of an elongated strip, the end portions of which are bent parallel to one another at right angles to the strand-constituting central portion.
4. The applicator of claim 3, in which in each assembly of strand and end support members is arranged for individual mounting on the said body.
5. The applicator of claim 4, in which said body comprises an elongated rectangular section block having a rectangular slot, a set of mounting blocks received in said slot, each said mounting block being fitted with an individual strand and end support member assembly, the mounting blocks being a sliding tit in the body and abutting against resilient means therein.
6. The applicator of claim 5, including a mainplate having a flange overlying said slot to retain said mounting blocks therein and itself slotted to permit the strands to extend through said flange.
7. The applicator of claim 6, including a springloaded guard overlying said strands and displacable to expose these for application to a substrate.