GB2396835A - External meniscus fluid bubble, leak prevention vial - Google Patents

Abstract

A test vial 10 has a closure configured to generate an external meniscus bubble 23 of fluid based on the surface tension effect, so as to prevent fluid contents from leaking out in the event of the tipping or inversion of the vial 10. Also disclosed is a test method in which a gas may be detected by passive surface exposure of a reagent indicator solution (19, fig. 1A). An aperture 16 in a membrane (15, fig. 1B) may provide the means on which the bubble may form. The membrane (15, fig. 1B) may permit the ingress of a gas into the vial 10, which may react with a reagent (19, fig. 1A) to give a result such as colour change. The vial 10 may be placed within a larger container 20 containing a sample 29, such as of biological material, which may give off gas which reacts with the reagent (19, fig. 1A). The apparatus may be used in the field testing of the levels of biological activity within a soil sample or similar. Alternative aperture 16 and membrane (15, fig. 1B) configurations are presented in fig.5.

Description

L

Spill-Resistant Testing This invention relates to testing and particularly to spill-resistant testing, such as for

robust, in-field use.

An example is determination of biological activity of soil, or decaying organic plant medium, lo compost.

All non-sterile materials contain microorganisms, and therefore have a certain biological activity.

Microorganisms perform diverse biochemical reactions, with various respiratory gas emissions, such as carbon dioxide.

Measurement of these emissions is a basis for assessing biological activity.

Gases such as carbon dioxide (CO2) can be detected by a reagent indicator, which changes colour in response to pH change.

Such tests have a role domestically, in commercial agricultural, or as general awareness-raising, educational aids.

Sample collection and transport to a remote test site risks sample degradation and contamination and is inconvenient.

Testing in the field in an exposed environment, and by relatively unskilled users - yet achieving a scientific test standard - also poses difficulties.

For example, colour testing might ideally use a sophisticated calorimeter or spectrophotometer in controlled laboratory conditions - which is inappropriate in the field, but whose accuracy and repeatability standards it is desired to emulate.

Thus, the in-field test methodology is desirably simple, intuitive and robust.

Similarly, the test apparatus should be rugged, reliable, and resistant to test disruption through inadvertent knocks or contents spillage.

This is to preserve reagent quantities and test outcome calibration when the apparatus is left unattended, to allow a reagent colour change to take effect - and which may take several hours.

Test reagent colour change attends a given sample condition, sample chamber size and configuration, and reagent quantity.

If reagent is spilled, exposure to it constrained, or contaminated by the sample, the colour change test outcome will also change - with misleading results.

An open-top container for test reagent is a simple, low-cost format allowing free contents access, but is vulnerable to spillage upon disturbance, with attendant loss of reagent contents.

Thus test apparatus resistant to contents spill, allowing free exposure of contents to a test atmosphere, yet simple and inexpensive to manufacture is desirable.

Prior Art

The Applicant has proposed, in GB2319837, a test kit with interconnected, even contiguous, sample and test reagent chambers, set against a colour reference scale.

The Applicant has also previously devised a portable, 'in-the-field', test kit of a sample chamber, a vial of test reagent, with a 'valve' head to allow exposure to a sample 1 0 atmosphere, but to inhibit reagent loss.

However, the valve represents a complication in manufacture and use.

Vessels or closures with non-spill features have been devised, but can inhibit contents exposure to a surrounding atmosphere, be ineffectual in inhibiting contents loss upon full inversion, or generally overly complex and expensive for a low cost in

1 5 field test.

Thus US6098850 features a bottle with an extended curved neck spout, but allowing for only partial tipping without liquid contents spill.

US5909827 shows a two-piece cap for a water bottle; a main cap with a depending stepped central well to receive a plug, movable vertically to open or close the bottle.

WO99/26001, US 5399971 and US5284261 employ pressure-equalisation valves for venting a flow of liquid from a container.

WO99/19225, CN1275955 and US5687865 feature bottle cap modifications for water dispensers; with a central conical well in the top of the cap formed with a scoreline, to receive a dispenser probe.

US5417336 shows a non spill medicine bottle, with multiple offset plates, movable to inhibit or allow flow of liquid contents as required.

US3319836 shows a spill-proof closure to dispense liquid contents upon bottle wall squeeze. A uni-directional valve disc has a central bore overlying a deformable valve plate with an arcuate aperture.

In-field test kits are also known in which a reagent is impregnated into a 'gel' substrate but these are generally not re-usable, and tend to employ alkali absorption methods, in which sodium or potassium hydroxide (NaOH or KOH) absorbs atmospheric CO2.

This alkali absorption method of measuring pH provides inaccurate assessment of CO2 emission rates, because the alkali absorbs CO2 from the test atmosphere (including the normal atmospheric amount of 300 ppm) likely to cause a change in environmental conditions during the test.

An example is US 5,320,807 (Brinton et al), in which card mounted Noble agar gel acts as a carrier for the CO2 absorbing sodium hydroxide reactant material.

In addition to depleting the test atmosphere of CO2, the gel is likely to dehydrate during storage, thereby losing the ability to absorb CO2.

Generally, the art represents an over-elaboration of valve and sampling architecture and test methodologies, inappropriate for robust, repeated in-field use.

Statement of Invention - Test Apparatus

According to one aspect of the invention, a (reagent) test vial, has a 'self-seal' or 'anti-spill' action, (upon tilt or tip over), the vial comprising a closure, an aperture in the closure, configured for liquid bubble formation, 1 5 through surface tension effect, upon vial re-orientation, to bring (liquid) reagent over the aperture, and thereby to inhibit (reagent) contents spillage.

Thus the reagent liquid itself is deployed to achieve an automatic sealing valve effect overall, an elegantly simple, yet effective, approach.

In practice, a reagent chamber may stand upright or lie somewhat inclined during a test - in either case care being taken to ensure a prescribed reagent surface area exposure.

A reagent chamber could be disposed, along with a sample under test, within a sealed test chamber.

Alternatively, the sample and the test reagent(s) in respective individual chambers, each with an aperture cap according to the invention, could be located in a shared sealed environment, such as a larger container with closure.

The cap aperture action inhibits spillage, through reagent liquid bubble formation, but otherwise interconnects test atmosphere and reagent.

Aperture shape and size - and attendant edge profile and material thickness and coatings - along with disposition in relation to overall container profile, are contrived - say, by empirical trial and experiment: À to preserve sufficient exposure to a test sample atmosphere; yet À to inhibit container contents spill and loss upon inadvertent tip over.

This is achieved through surface tension effects for a particular reagent liquid and access aperture.

The aperture may be disposed in a discrete (and so replaceable) 'restrictor membrane', so that different aperture profiles may be used for optimal results, according to the viscosity of the liquid contents.

The 'restrictor' can be changed to suit different liquids.

A meniscus bubble readily forms - and acts as a temporary seal, inhibiting contents egress.

Such a bubble seal can withstand minor casual handling or impact.

The bubble seal thus remains intact, unless, say, abruptly knocked or vigorously shaken, by deliberate action or intervention - or contaminated with surfactant such as oils or greases (even from skin contact), which alters the surface tension effect.

If the reagent chamber is (inadvertently) tipped over, reversion to its original (upright or inclined) state causes the meniscus bubble to disperse, allowing reagent (re-) exposure to the test atmosphere.

In practice, pressure equalization may burst the bubble with a characteristic popping sound.

In the event that the meniscus bubble fails to burst upon reversion of the vial to its untipped' state during a test, handling the test chamber warms the contents, the air pressure within the vial increases, and the meniscus bubble bursts.

The aperture is thus cleared for the test to proceed, without having to open the sealed test chamber, which would affect the results.

A convenient vial configuration is a tall, slender cylindrical jar or bottle, of glass or synthetic plastics - such as a proprietary form used for a dropper bottle - and with a synthetic plastics screw closure cap.

The cap incorporates a central aperture (such as originally intended for a dropper spout) and an internal restrictor membrane is located between cap and bottle rim.

The restrictor is conveniently a stiff or semi-rigid, thin wafer of synthetic plastics material, such as PTFE.

(Resiliently deformable) washer seals may be fitted above and below the restrictor membrane.

These inhibit liquid contents leakage, at the restrictor periphery, and protect the restrictor from damage by the vial rim or cap.

Surface graduations or level markings provide a reference for reagent fill level.

Statement of Invention

Test Methodology / Reagent According to another aspect of the invention, a gas is detected by (passive) surface exposure of a reagent indicator solution.

In the case of a (visible) colour change, colour change over a prescribed test period is measured against a colour reference chart, or by calorimetry.

If the gas (such as CO2) produces a pH change in the reagent solution, this can be measured by electrodes in a pH meter - alone, or in conjunction with colour measurement.

In practice, indicator solutions, such as phenol red in solution with sodium bicarbonate, or so-called Universal Indicator Solution, may be used with test apparatus and methodology according to the invention.

A particular example test reagent indicator solution, for gaseous emissions, such as CO2, comprises: À 5 mM sodium bicarbonate; À 100 mM potassium chloride; and À 40 ppm phenol red; in de-ionised water.

{where mM or mMol = milk Moles} It is known to use this solution by bubbling test gas through the solution, and measuring the resultant colour change due to changes in pH.

However, the Applicant has found that this solution can be used satisfactorily by passive' surface exposure, such as to atmospheric CO2 When testing gases in this way, the initial colour change occurs at the indicator solution surface, but rapidly spreads throughout the body of the solution, thus achieving a uniform overall colour change.

Assessment of colour change, say in relation to a colour reference chart, gives a quantitative indication of pH, and therefore CO2 emitted.

This in turn reflects biological activity, for given sample and reagent volume, over a certain time.

For greater test accuracy, it is envisaged that testing of particular gas(es) released from a sample could be combined with testing of other environmental variables which affect the test results, such as temperature, moisture content, and the test period.

Data upon these variables may be downloaded into a computer for analysis and calibration.

Thus multiple vials with different reagents could share a common test environment with a test sample.

By lowering the concentration of bicarbonate in the solution, the sensitivity of the indicator is increased.

In practice, a range of 0.5-5 mM can be used.

If the bicarbonate solution is present in excess, the concentration of CO2 is proportional to pH.

The concentration of phenol red may also be varied; higher concentrations giving more intense colours.

The potassium chloride maintains a constant ionic strength in the indicator solution.

This solution is particularly suitable for test environments, as it engenders equilibration' of atmospheric CO2 with the bicarbonate solution.

That is CO2 is not depleted from a (test) atmosphere.

Moreover, the reaction is reversible.

1 5 Embodiment(s) There now follows a description of some particular embodiments of the invention, by way of example only, with reference to the accompanying diagrammatic and schematic drawings, in which: Figure 1A shows an exploded side elevation of a reagent vial with a part cut-away cross-section of a bespoke closure cap, with restrictor; Figure 1 B shows a perspective view of the reagent vial of Figure 1 A with bespoke closure cap fitted; Figures 2A through 2D show the bespoke closure cap for the vial of Figures 1A and 1B; Thus, more specifically: Figure 2A shows an underside plan view of a cap, revealing the lower washer seal and a ('controlled exposure') restrictor membrane; Figure 2B shows an upper plan view of Figure 2A; and; Figure 2C shows a side elevation of the cap of Figures 2A and 2B; Figure 2D shows a perspective view of the cap of Figures 1 A through 2C being exchanged for a 'storage cap' without an aperture; Figures 3A and 3B show a sample test chamber, for a reagent vial of Figures 1A and 1B; Thus, more specifically: Figure 3A shows a side elevation of a test chamber and closure cap, with reagent vial and test sample in situ in a solid test sample medium, such as compost; Figure 3B shows the test chamber of Figure 3A with both reagent and liquid test sample (such as water), contained within separate vials; Figures 4A and 4B depict vial sealing through surface tension bubble formation effects of reagent liquid; Thus, more specifically: Figure 4A shows a vial of Figures 1A and 1B inverted to drive reagent liquid contents to the cap end and allow bubble formation at the cap aperture; Figure 4B shows a test chamber of Figures 3A and 3B with a vial tipped over, but reagent liquid spill inhibited; Figures 5A through 5H depict plan views of the top of the reagent vial, showing examples of some of the possible variations in aperture configuration and profile(s); Thus, more specifically: Figure 5A shows the circular aperture profile of the reagent vial as depicted in Figures 1A through 2D; Figure 5B shows a variant aperture configuration to that of Figures 1A through 2D, and 5A, having two apertures; Figure 5C shows a further variant configuration, with four apertures; Figure 5D shows a variant aperture, of oval profile; Figure BE shows a variant aperture, of arcuate profile; Figure 5F shows a variant aperture, of triangular profile; Figure 5G shows a variant aperture, of star shaped profile; Figure 5H shows a variant aperture, of square profile; Figures 6A through 6D show sectional cross sections of the top surface of the reagent vial, taken through line X-X of Figure 5A, and showing the cap, restrictor and aperture (washer seals not shown for simplicity), with variant cross sectional aperture profiles; Thus, more specifically: Figure 6A shows a square-edged aperture; Figure 6B shows a straight sloping edge aperture; Figure 6C shows a curved edge aperture; Figure 6D shows a stepped edge aperture with a tapered land; Figures 7A through 7C show test chambers fitted with support discs; Thus, more specifically: Figure 7A shows the test chamber of Figures 3A, 3B, and 4B fitted with a (mesh) support disc, incorporating apertures with radial slits to locate test vials over a test sample; Figure 7B shows a variant test chamber to those of Figures 3A, 3B, 4B and 7A, having a (mesh) support disc, and no base; Figure 7C shows the variant test chamber of Figure 7B driven directly into a solid sample, such as soil, to be tested; Figures 8A and 8B show a test chamber, with a variant support disc fitted to the vial; Thus, more specifically: Figure 8A shows the test chamber of Figures 3A, 3B, 4B and 7A, with a vial fitted with a support disc of smaller diameter than the internal diameter of the test chamber; Figure 8B shows the test chamber of Figure 8A, slightly tilted to demonstrate the stabilising action of the support disc on the vial; Figures 9A and 9B show a further variant test chamber, having an internal (spring clip) vial mount on the chamber floor, for added vial stability; Thus, more specifically: Figure 9A shows a perspective view of the test chamber with integral vial holder; Figure 9B shows the reagent vial inserted into the vial holder, as it would be during a test; Figures 1 OA and 1 OB show multiple vials - with respective holders; Thus, more specifically: Figure 1 OA shows a reagent vial and a somewhat larger diameter test sample vial in a common chamber; Figure 1 OB shows two reagent vials and a test sample vial in a common chamber; +++ Referring to the drawings, a test apparatus is configured as a robust 'in-the-field' test kit', such as for determination of soil biological activity.

Principal elements include: À a vial 10, configured as a transparent or translucent walled cylindrical bottle 1 0 11, with a removable cap 12, for a colour change reagent 19; and À a sample test chamber 20, comprising a jar 21, with a removable lid 22, for a sample 29, such as soil, under test.

As described later, along with a reagent vial, a test chamber may house a sample, or a sample housed within sample vial.

The relative volumetric capacities of vial 10 and sample chamber 20, along with the quantity of reagent 19 used, are carefully chosen for a prescribed test.

A prime test is for carbon dioxide (C02) emission - reflecting biological (micro-organism respiratory) activity of a (soil) sample 29.

The test can be used for decaying plant (eg vegetable) material in composting.

Reagent 19 quantity is determined by reference to a graduated level, incremental scale marking 18, engraved, etched, printed or transfer applied, on the (outer) side wall of the bottle 11.

Similarly, a graduated scale may also be marked on the sample chamber 20 (graduations not shown) to assist in determining appropriate sample quantity.

A certain time period is allowed for a test reaction, such a colour change in reagent.

The reaction may be reversible, depending on the indicator solution used, allowing repeated testing upon other samples.

The translucent side wall of the vial 10 allows a calorimetric comparison of the reagent 19 colour (change) with a colour reference standard chart or scale (not shown).

For security, the cap 12 is a screw closure.

Thus, internal threads 14 on the cap 12 engage an external threaded neck 13 on the vial bottle 11.

A restrictor membrane 15 within the cap 12 contacts the edge rim of a threaded neck 13 of the vial bottle 11 when the cap 12 is tightened.

The overall closure is configured as a safety valve, to preserve reagent contents.

To this end a central circular aperture 16 in the cap 12 exposes an internal restrictor 15, which features a specially profiled aperture.

In particular, restrictor membrane aperture shape, size, thickness, edge profile, surface finish or treatment and material all contribute to promote a particular effect of liquid bubble formation through surface tension effect.

Thus, upon inversion or tipping of the vial 10, reagent liquid contents 19 flow to the cap 12 end, bridging the aperture 16 and triggering formation of a meniscus bubble 23 through surface tension effect.

This bubble 23 creates a temporary liquid seal, as depicted in Figures 4A and 4B; In practice, the aperture 16 must be of sufficient diameter for meniscus bubble 23 formation to prevent spillage upon vial inversion, yet to subsequently dissipate, allowing passage of test sample gases into the vial.

Optimal aperture form and other factors are determined empirically by trial and error. I Multiple apertures may be employed, as shown in Figures 5B and C, in order to increase total effective cap aperture size and thus exposure of reagent to test sample gas release, yet preserve - in this case multiple discrete - bubble seal formation.

Reagent contents calibration is adjusted accordingly.

At the risk of complication and expense in manufacture, the container could be segmented into isolated sub-divisions for different reagents, each in communication with a respective cap aperture.

The aperture(s) should also have a clean cut, smooth or nonjagged profile, to preserve surface tension, but need not necessarily be of circular profile.

Figures 5D through 5H show examples of non-circular aperture profiles.

The restrictor membrane 15 material, surface treatment, finish and freedom from contaminants are also material in meniscus bubble formation.

Examples of suitable restrictor materials include PTFE, wax coated materials, and some metals.

Restrictor (wafer) thickness must also be optimal for meniscus bubble formation and dissipation.

As a further safeguard against accidental spillage of vial contents during testing, the sample test chamber 20 could incorporate a circumferential stabiliser skirt.

This skirt comprises a mesh disc 31, as shown in Figures 7A through C, which could be a close fit with the inside of test chamber 20.

Vials 10 may be a close fit within apertures 33, having radial slits 34, in the disc 31 body.

Such close fits allows suspension of vials above a sample.

Alternatively, a looser fit would still provide vial stability, with vials in contact with a sample.

To allow free passage of gases from the test sample 29, to the vial aperture 16, the 1 0 disc 31 is conveniently a mesh material, as shown.

Figures 8A and 8B show a variant support disc 31, of smaller diameter than that of the test chamber 20, having an aperture 33, with radial slits 34, through which the vial 10 is slotted for increased stability.

Alternatively, a vial (base) mount or holder 25, may be fitted as shown in Figure 9A.

1 5 Figure 9B shows a vial 10 positioned in a (spring clip) mount 25 upon the base of a sample chamber 20.

The vial mount 25 could be of transparent or translucent material, so that reagent colour changes can still be seen.

The vial mount 25 could also have a waisted or part cut-away profile, for contents exposure, as shown in Figures 9A through 10B.

During testing, sample test material 29 may be placed directly in sample chamber 20, as shown in Figures 3A and 4B, or alternatively in a vial 10.

Figures 3B,1 OA and 1 OB illustrate the test material 29 contained within a vial 10, with gases released able to flow freely as illustrated by arrows 24, via aperture 16, and around sealed test chamber 20, including into reagent vial 10 and into contact with reagent 19.

Placing the test material 29 (be it a liquid or solid) in a vial 10 further reduces the risk of sample spillage, and reduces the likelihood of accidental direct mixing of sample 29 with reagent 19, which would adversely affect test accuracy.

Alternatively, a test chamber 20 having no base as shown in Figures 7B and C, may be placed over the test sample, and driven into the sample surface 32 (in the case of solids such as soil) so that any gases emitted from the sample are contained within the chamber 20.

This has the advantage of not having to 'collect' a test sample, thus minimising the risk of sample contamination. r

It may be desirable to test for the release of more than one gas produced by a sample, for example methane or ammonia gases.

If this is desired, multiple vials 10 each containing a different reagent 19 may be placed in test chamber 20, together with sample 29 - either loose in chamber 20, or contained with a vial 10 - as shown in Figure 10B.

Test Methodology - Reagent Reagents such as so-called 'Universal Indicator' solution, display colour change according to changes in pH by, say, CO2 dissolving in a weak sodium bicarbonate solution.

This is a reversible reaction, the reagent solution gradually returning to its start colour upon being removed from the test chamber environment.

Once reagent has changed colour over a prescribed period in test conditions, it may be necessary to transport the vial to another location, for pH measurement, say by use of a colour reference chart, pH meter, or calorimetry.

In order to inhibit reagent returning to its start colour, the reagent test cap 12 may be replaced by the 'storage cap' 26 without an aperture as shown in Figure 2D.

This effectively 'freezes' the colour change, until any (pH) measurements have been made.

After the required measurements have been recorded, the storage cap 26 can be replaced by test cap 12, and left to equilibrate for, say, 24 hours in a normal (non test) environment.

The reagent is then ready for re-use.

When the reagent 19 has returned to its 'normal' start colour, the test cap 12 may be removed and replaced with the storage cap 26, in order to minimise reagent 19 evaporation from vial 10, ready for another test.

Some reagent evaporation may occur during and between tests, increasing concentration of reagent indicator solution, which would affect test results.

It is therefore envisaged that the reagent solution will require replacing approximately every 10 uses, in order to preserve test accuracy.

Component List 1 0 vial 1 1 bottle 1 2 cap 13 external threads 14 internal threads restrictor membrane 1 6 aperture 17 washer seals 18 scale markings 1 9 reagent sample test chamber 2 1 jar 22 test chamber lid 23 meniscus / bubble 24 gas released from sample 2 5 vial mounVholder 26 storage cap 27 nose of cap seal 29 sample 31 (mesh) disc 32 surface of test material 33 aperture 34 slit

Claims (2)

1. Claims 1.

   A (reagent) test vial (10), with a 'self-seal' or 'anti-spill' action, (upon tilt or tip over), the vial comprising a closure (12), an aperture (16) in the closure, configured for liquid bubble (23) formation, through surface tension effect, upon vial re-orientation, to bring (liquid) reagent over the aperture, and thereby to inhibit (reagent) contents spillage.
2. 2.

   A test vial, as claimed in Claim 1, with an aperture in a discrete restrictor membrane, interposed between a closure cap and a container neck rim; the aperture size, shape, edge profile, seal material, thickness and surface finish or treatment, co-operating to promote bubble formation.

   A test vial, as claimed in either of the preceding claims, with a plurality of discrete apertures (16), each configured for bubble formation. 4.

   A test vial, as claimed in any of the preceding claims, fitted with a circumferential skirt, to limit vial tilt or tip. 5.

   A test vial, substantially as hereinbefore described, with reference to, and as shown in, the accompanying drawings. 6.

   A test apparatus, including one or more test vials, as claimed in any of the preceding claims, locatable within a common test chamber (21), sealable by a closure cap (22). 7.

   A test apparatus, as claimed in Claim 6, with one or more vial mounts (25) . 8.

   A test apparatus, as claimed in Claim 7 or 8, with a closeable top, an open base, exposing lower peripheral edge, for sample penetration. 9.

   A test apparatus, substantially as hereinbefore described, with reference to, and as shown in, the accompanying drawings. 10.

   A test regime, for use with a test vial or test apparatus as claimed in any of the preceding claims, in which a gas (24) may be detected by (passive) surface exposure, of a reagent indicator solution (19). 1 1.

   A test regime, 1 0 as claimed in Claim 10, in which a visible colour change in the reagent solution (19), is measured against a colour reference chart, or by calorimetry. 12.

   A test regime, as claimed in either of Claims 10 or 11, in which the gas produces a pH change in the reagent solution (19), which may be measured by electrodes in a pH meter, alone, or in conjunction with colour measurement. 13.

   A test regime, as claimed in any of Claims 10 through 12, in which the reagent (19) comprises: 5 mM sodium bicarbonate, mM potassium chloride, and ppm phenol red, in de- ionised water.