Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
  • G01N31/22—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators
  • G01N31/221—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators for investigating pH value
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration or pH-value ; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid or cerebral tissue
  • A61B5/14539—Measuring characteristics of blood in vivo, e.g. gas concentration or pH-value ; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid or cerebral tissue for measuring pH
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F13/00—Bandages or dressings; Absorbent pads
  • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
  • A61F13/42—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators with wetness indicator or alarm
  • A61F2013/427—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators with wetness indicator or alarm pH indicator
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
  • G01N21/77—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
  • G01N21/78—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator producing a change of colour
  • G01N21/80—Indicating pH value
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
  • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
  • G01N27/416—Systems
  • G01N27/4163—Systems checking the operation of, or calibrating, the measuring apparatus
  • G01N27/4165—Systems checking the operation of, or calibrating, the measuring apparatus for pH meters

Definitions

• pH measurements are important in, for example, medicine, biology, chemistry, agriculture, forestry, food science, environmental science, oceanography, civil engineering, chemical engineering, nutrition, water treatment and water purification.
• the pH of water is routinely tested.
• the pH of drinking water is routinely monitored to ensure that it is safe to drink, whereas the water in swimming pools is routinely tested to ensure that it is safe to swim in.
• Monitoring alterations in the pH of fish ponds or river water can be indicative of environmental pollution.
• knowledge of the pH of the soil is not only instructive in the selection of suitable crops but also discerns whether there are local environmental issues, such as pollution.
• maintaining a proper pH range is essential in many of the physical and chemical reactions that take place during food and drink processing.
• Monitoring the pH of bodily fluids can be a useful diagnostic. For example, it has been demonstrated that the pH of saliva can predict susceptibility to a range of diseases, including cancer, heart disease and osteoporosis.
• a device for determining pH of a fluid sample.
• the device preferably includes a surface configured to contact the fluid and a pH indicator covalently immobilised thereon, wherein the pH indicator has a first colour prior to contact with the fluid and changes colour along a colour spectrum as a function of the pH of the fluid.
• the pH indicator changes colour in response to change in pH and this colour change is detectable at, for example, intervals of about a 0.1 unit, about 0.2 unit, about 0.3 unit about 0.4 unit or about 0.5 unit interval of pH. It is envisaged that the detection level will vary based on the type of detection means utilised.
• an electronic detector such as a colour meter capable of detecting changes in colour of light, has the capability to detect a 0.1 unit change in pH.
• the human eye is only capable of visually detecting a colour change which is associated with about a 0.5 unit change in pH.
• the pH indicator utilised in the device is able to detect the pH between about pH 0 and about pH 14 and indicates changes in pH by way of a colour change along a colour spectrum, with each colour in the spectrum being associated with a particular pH.
• the pH indicator is able to detect a pH between about pH 5.0 and about pH 10.0.
• the pH indicator is able to detect a pH between about pH 5.5 and about pH 9.5. More particularly the pH indicator is able to detect a pH between about pH 6.5 and about pH 9.5.
• Suitable pH indicators include phenylazo compounds such as those listed in Table 1 which are available from Fraunhofer EMFT,
• GJM-546 1 -hydroxy-4 - [4 [(hy droxyethylsulphony 1) - phenylazo]-napthalene-2-sulphonate
• GJM-534 4-[4-(2-hydroxyethylsulphonyl)-phenylazo]- 2,,6-dimethoxyphenol
• the pH indicator is a triarylmethane dye. In some embodiments, the pH indicator is a fluorescent dye.
• the pH indicator comprises a combination of compounds which allows a broader pH range to be detected than can be detected by use of a single compound.
• the pH indicator comprises a combination of phenylazo compounds.
• the combination comprises at least two phenylazo compounds selected from the group listed in Table 1.
• the combination comprises at least three phenylazo compounds selected from the group listed in Table 1.
• the combination comprises at least one phenylazo compound selected from the group listed in Table 1 and at least one compound that is not a phenylazo compound.
• derivatives or modifications of the phenylazo compounds listed in Table 1 are envisaged.
• the device is a cellulosic material, for example a cellulose pad.
• the device is a non-woven mesh or perforated film.
• the fluid is a liquid. Non-limiting examples includes water.
• the fluid is a gas, for example for use in a face mask.
• the fluid is a moisture.
• Non- limiting examples include the moisture associated with a soil sample.
• the fluid is a bodily sample.
• Non- limiting examples include, saliva, urine, blood, sweat/ perspiration.
• a device for determining pH of a fluid sample.
• the device preferably includes: (a) a fluid-contacting surface, (b) an opposing non-fluid contacting surface, (c) a pH indication zone comprising a pH indicator covalently immobilised therein which indicates the pH of a fluid, wherein the colour of the pH indicator changes in response to a change in the pH of the fluid, and (d) at least one conduit for directing fluid towards the pH indication zone.
• the conduit helps direct fluid toward the pH indicator without materially altering the pH en route to the indicator.
• the material of the conduit contains no acid or base functionality, that is to say, it is neutral and can not remove any acid or base entities from the fluid until it reaches the pH indicating system.
• the device has an outer surface and the pH indication zone is located at or near the outer surface.
• the device has a peripheral edge extending between the fluid contacting surface and the opposing non-fluid contacting surface and pH indication zone is located at or near to this peripheral edge.
• the conduit directs fluid laterally towards the pH indication zone.
• the pH indicator changes colour in response to change in pH and this colour change is detectable at, for example, intervals of about a 0.1 unit, about 0.2 unit, about 0.3 unit about 0.4 unit or about 0.5 unit interval of pH. It is envisaged that the detection level will vary based on the type of detection means utilised. For example, an electronic detector such as a colour meter has the capability to detect a 0.1 unit change in pH. In comparison, the human eye is only capable of visually detecting a colour change which is associated with about a 0.5 unit change in pH.
• the pH indicator utilised in the device is able to detect the pH between pH 0 and 14 and indicates changes in pH by way of a colour change along a colour spectrum, with each colour in the spectrum being associated with a particular pH.
• the pH indicator is able to detect pH between about pH 5 and about pHlO.
• the pH indicator is able to detect pH between about pH 5.5 and about pH 9.5.
• the pH indicator is able to detect pH between about pH 6.5 and about pH 9.5.
• Suitable pH indicators include phenylazo compounds such as those selected from the group listed in Table 1.
• the pH indicator comprises a combination of compounds which allows a broader pH range to be detected than can be detected by use of a single compound.
• the pH indicator comprises a combination of phenylazo compounds.
• the combination comprises at least two phenylazo compounds selected from the group listed in Table 1.
• the combination comprises at least three phenylazo compounds selected from the group listed in Table 1.
• the combination comprises at least one phenylazo compound selected from the group listed in Table 1 and at least one compound that is not a phenylazo compound.
• derivatives or modifications of the phenylazo compounds listed in Table 1 are envisaged.
• a formulation is provided for indicating pH of a fluid.
• the pH indicator is covalently immobilised within the formulation and is therefore not washed away by the fluid upon contact.
• the formulation preferably includes a dye that functions as a pH indicator.
• the dye may include a phenylazo compound, where the colour of the phenylazo compound changes in response to a change in the pH of the fluid.
• the pH dye changes colour in response to a 0.5 unit interval change in pH.
• the pH indicator has a different colour for each 0.5 unit interval change in pH.
• the pH indicator utilised in the device is able to detect the pH between pH 5 and 10, particularly between pH 5.5 and 9.5 and more particularly between pH 6.5 and 9.5.
• Suitable pH indicators include phenylazo compounds such as those selected from the group listed in Table 1.
• the pH indicator comprises a combination of compounds which allows a broader pH range to be detected than can be detected by use of a single compound.
• the pH indicator comprises a combination of phenylazo compounds.
• the combination comprises at least two phenylazo compounds selected from the group listed in Table 1.
• the combination comprises at least three phenylazo compounds selected from the group listed in Table 1.
• the combination comprises at least one phenylazo compound selected from the group listed in Table 1 and at least one compound that is not a phenylazo compound.
• derivatives or modifications of the phenylazo compounds listed in Table 1 are envisaged.
• the formulation is applied to a device for use in detecting pH at the point of manufacture.
• the formulation is an adhesive.
• the adhesive is a low tack adhesive, for example a silicon adhesive.
• the formulation is a gel, for example, a conformable semi-rigid or rigid gel, that does not disintegrate upon contact with the fluid to be tested.
• the formulation can be used in a device according to the first and/or second aspect.
• a method for monitoring the pH of a fluid preferably comprises the steps of: (a) providing a device comprising a surface configured to contact the fluid, said surface having a pH indicator covalently bound thereto, wherein the pH indicator has a first colour prior to contact with the fluid and changes colour as a function of the pH of the fluid, (b) contacting the device with the fluid, (c) assessing the colour of the pH indicator. It is envisaged that the method can be utilised in numerous applications in which the knowledge of the pH of a fluid sample is paramount to determining quality control or safety.
• Non-limiting examples of potential applications include: food storage; packaging spoilage indicators; wine; brewing; analysis of drinking water, swimming pool water, river water or fish ponds; agriculture and horticulture; clothing, for example perspiration analysis; in-line monitoring of processes, gases, liquids; skin care - medical (dermatology) or cosmetic; coatings of containers and surfaces to detect changes/inconsistencies; monitoring drug release or stability.
• a device comprises a fluid contacting surface having a pH indicating means covalently bound thereto, wherein the pH indicating means has a first colour prior to contact with a fluid and changes colour as a function of the pH of the fluid.
• a device comprises a pH indicating means, wherein the pH indicating means has a first colour prior to contact with a fluid and changes colour as a function of the pH of the fluid and a conduit means for directing the fluid towards the pH indicating means.
• Figures 1A and IB are side cross-sectional views of an illustrative device having a pH indicator, the colour of which changes as a result of alterations in the pH of a fluid.
• Figures 2A and 2B are side cross-sectional views of an illustrative device in which a fluid is guided via a conduit to a pH indication zone which includes a pH indicator, the colour of the indicator changes as an indication of the pH of the fluid.
• Figure 3 is a photograph of a Post-Op sample dyed with GJM-514, illustrating changes in colour of the dye in response to solution changing pH along a pH unit interval scale.
• Figures 4A-F are graphic representations of colour pen measurements for the
• Figure 5 is a photograph of a Post-Op sample dyed with a first combination of dyes, illustrating changes in colour of the dye combination in response to a solution changing ⁇ along a pH unit interval scale.
• Figures 6A-D are graphic representations of colour pen measurements for the
• Figure 7 is a photograph of a Post-Op sample dyed with a second combination of dyes, illustrating changes in colour of the dye combination in response to a buffered solution changing pH along a pH unit interval scale.
• Figures 8A-E are graphic representations of the colour pen measurements for the
• Figure 9 is a photograph of a Post-Op sample dyed with a third combination of dyes, illustrating changes in colour of the dye combination in response to a buffered solution changing pH along a pH unit interval scale.
• FIG. 10A-F are graphic representations of the colour pen measurements for the
• Figure 1 1 is a photograph of a Post-Op sample dyed with a fourth combination of dyes, illustrating changes in colour of the dye combination in response to a buffered solution changing pH along a pH unit interval scale.
• Figures 12A-E are graphic representations of the colour pen measurements for the
• Figures 13 A-F are photographs of pH sensitive gauze in ex- vivo wound model with alternating pH 5 and pH 8 horse serum being pumped in.
• Figure 13A is a photograph of pH5 after 2.5 hours approx.
• Figure 13B is a photograph of pH5 after 5.5 hours approx.
• Figure 13C is a photograph of pH 8 after 8 hours approx.
• Figure 13D is a photograph of pH 5 after 3.5 hours approx.
• Figure 13E is a photograph of pH 5 after 5.5 hours approx. with the flow rate of horse serum increased at 3.5 hours.
• Figure 13F is a photograph of pH 5 after 7.5 hours with the flow rate of horse serum increased at 3.5 hours and at 5.5 hours.
• Figures 14A to F are photographs of pH sensitive foam (V.A.C. WhiteFoam trade mark of KCI) in an ex- vivo wound model with alternating pH5 and pH 8 horse serum being pumped in.
• pH sensitive foam V.A.C. WhiteFoam trade mark of KCI
• Figure 14A is a photograph at pH 5 after 2.5 hours approx.
• Figure 14B is a photograph at pH 5 after 5.5 hours approx.
• Figure 14C is a photograph at pH 8 after 15 hours approx.
• Figure 14D is a photograph at pH 5 after 3.5 hours approx..
• Figure 14E is a photograph at pH 5 after 5.5 hours approx., with the flow rate of horse serum increased at 3.5 hours.
• Figure 14F is a photograph at pH 5 after 7.5 hours approx.., with the flow rate of horse serum increased at 3.5 hours and at 5.5 hours.
• Figures 15 A to E are photographs of pH sensitive gauze in an ex- vivo wound model with alternating basic and acidic water being pumped in.
• Figure 15A is a photograph at 8am Day 1 showing basic pH.
• Figure 15B is a photograph at 12:57 pm Day 1 (5 hours) showing basic pH.
• Figure 15C is a photograph at 08:03am Day 2 (24 hours) showing basic pH.
• Figure 15D is a photograph at 12:41pm Day 2 (5 hours) showing acidic pH.
• Figure 15E is a photograph at 15:06 Day 2 (7 hours) showing acidic pH.
• Figure 15F is a photograph at 16:47 Day 2 (9 hours) showing acidic pH.
• Figures 16A to F are photographs of pH sensitive foam in an ex- vivo wound model with alternating basic and acidic water being pumped in.
• Figure 16A is a photograph at 8am Day 1 showing basic pH.
• Figure 16B is a photograph at 12:57 pm Day 1 (5 hours) showing basic pH.
• Figure 16C is a photograph at 08:03 am Day 2 (24 hours) showing basic pH.
• Figure 16D is a photograph at 09:06 Day 2 (1 hour) showing acidic pH.
• Figure 16E is a photograph at 15:06 Day 2 (7 hours) showing acidic pH.
• Figure 16F is a photograph at 16:47 Day 2 (9 hours) showing acidic pH.
• Figures 17A to H are photographs of pH sensitive foam in a clear Perspex wound model with alternating basic and acidic water.
• Figure 17A is a photograph at 8am Day 1 showing basic pH.
• Figure 17B is a photograph at 12:56 Day 1 (5 hours) showing basic pH.
• Figure 17C is a photograph at 16:20 Day 1 (8.5 hours) showing basic pH.
• Figure 17D is a photograph at 8:02 am Day 2 (24 hours) showing basic pH.
• Figure 17E is a photograph at 09:05 am Day 2 (1 hour) showing acidic pH.
• Figure 17F is a photograph at 10:50am Day 2 (3 hours) showing acidic pH.
• Figure 17G is a photograph at 13:26 Day 2 (5.5 hours) showing acidic pH.
• Figure 17H is a photograph at 15:05 Day 2 (7 hours)showing acidic pH.
• Figure 1A depicts a device 100 having a fluid-contacting surface 102 and an opposing non-fluid-contacting surface 104.
• Figure IB depicts the device 100 being brought into contact with a fluid 106.
• the device 100 can be made of any material that is suitable for contact with the fluid without disintegrating.
• the device further includes a pH indicator 108 which is applied to one or both of surfaces 102 and/or 104.
• the pH indicator is covalently immobilised on or adjacent to the surface 102 and/or 104 so that it is not washed away by the fluid.
• the pH indicator is chemically bound to the surface 102 and/or
• the pH indicator is covalently bound directly to the surface 102 and/or 104.
• the surface 102 and/or 104 is provided within an adhesive and the pH indicator is covalently bound to reactive moieties within the adhesive.
• a conventional acrylic adhesive such as K5 (Smith & Nephew, Inc) used in the construction of wound dressings contains residues of 2-hydroxy-ethylmethacrylate, which provide a reactive functional hydroxyl (OH) group, pendant to the polymer backbone, to which the pH indicator can be covalently bound.
• suitable adhesives include acrylic-based adhesives with pendant OH or COOH groups.
• an indication for indicating which side the pH indicator is applied to may be provided. This indication allows the user to appropriately orient the device during placement on or in the fluid to ensure that the surface which has the pH indicator is correctly orientated and comes into contact with the fluid.
• the pH indicator may be applied across substantially the entire surface 102 and/or 104, to allow any variations in the pH at the meniscus of the fluid sample to be identified .
• the pH indicator may be applied to discrete areas of surfaces 102 and/or 104.
• the pH indicator exhibits a first colour prior to contact with a fluid and changes colour as a function of the pH of the fluid.
• the first colour of the pH indicator may be colourless.
• the pH indicator is capable of reversibly changing colour in response to pH.
• the pH indicator is a phenylazo compound.
• the phenylazo compound is selected from the group listed in Table 1.
• the phenylazo compound is not 2-[4(2-hydroxyethylsulfonyl)-phenyl]diazenyl]-4-methylphenol.
• the phenylazo compound is not hydroxy-4-[4[(hydroxyethylsulphonyl)- phenylazo]-napthalene-2-sulphonate.
• the phenylazo compound is not 2- fluoro-4-[4[(2-hydroxyethanesulphonyl)-phenylazo]-6-methoxy phenol. In some embodiments, the phenylazo compound is not 4-[4-(2-hydroxyethylsulphonyl)-phenylazo]-2 till6- dimethoxyphenol. In certain embodiments, the phenylazo compound is 2-[4(2- hydroxyethylsulfonyl)-phenyl]diazenyl]-4-methylphenol. In some embodiments, the pH indicator includes a plurality of phenylazo compounds.
• the pH indicator includes a combination of phenylazo compounds, for example a combination of phenylazo compounds selected from the group listed in Table 1. In some embodiments, the pH indicator includes a combination of two phenylazo compounds. In some embodiments, the pH indicator includes a combination of three phenylazo compounds. In some embodiments, 2- [4(2- hydroxyethylsulfonyl)-phenyl]diazenyl]-4-methylphenol is combined with at least one other phenylazo compound selected from the group listed in Table 1.
• the ratio of phenylazo compound may be 1 :1 , but other ratios are envisaged, for example, but in no way limiting, 0.5:1.5 or 1.5:0.5 or 1 :2 or 2:1 or 1 :0.1.
• the pH indicator includes at least one phenylazo compound, for example a phenylazo compound selected from the group listed in Table 1 and at least one other compound that is not a phenylazo compound. In certain embodiments, the pH indicator is not a phenylazo compound.
• FIG.2A shows a side cross-sectional view of a device 200 comprising an absorbent element 204, the lower surface of which is a fluid-contacting surface 206.
• the device also comprises a pH indication zone 208 which is located at or adjacent to the opposing non fluid-contacting surface 210.
• This pH indication zone includes a pH indicator (e.g., as disclosed herein) which is capable of reversibly changing colour in response to changes in pH.
• the pH indication zone 208 is disposed above the absorbent layer 204, so the pH indicator can be monitored over time without having to remove the device from any substrate that it is adhered to.
• a transparent layer 212 overlays at least part of the pH indication zone, which protects the integrity of the pH indicator but still allows the user to monitor the colour of the pH indicator over time.
• the device includes at least one conduit that is configured to direct fluid to the pH indication zone 206, ensuring that the pH of the fluid is not materially altered as it passes through the components of the device.
• One or a plurality of conduits could be used. As shown in Fig. 2 A&B, two conduits are used, although one or more other conduits could also be included.
• the two conduits 214 and 216 are oriented vertically and extend across the device.
• the conduits are preferably sealed, so as to not exchange fluid with the absorbent layer, but are in communication with the pH indication zone 208 and direct the fluid to the pH indication zone 208 located in the upper part of the device.
• the conduits may be in the form of narrow capillaries which transmit the fluid towards the pH indication zone 208.
• the conduits may incorporate or may be formed from wicking materials, for example, woven, non-woven, knitted, tows or fibres made of suitable materials to facilitate wicking of the fluid towards the pH indication zone 208.
• a pH indication zone is provided at or near a lateral edge 218 or 220 of the device and at least one conduit is provided within the device to direct the fluid laterally to the pH indication zone.
• the pH indication zone is provided in a layer of the device which forms an outer surface of the device and a transparent cover layer is not used.
• the conduits may take the form of a long strip or be of an elongated lozenge shape when viewed from the fluid-contacting surface. Alternatively, the conduit may be formed of crosses or quadrilateral shapes.
• a phenylazo pH indicating dye for example a phenylazo pH indicating dye selected from the group listed in Table 1 , is reacted with 140 ⁇ 1 concentrated sulphuric acid for 30 mins to form a dye solution.
• a third step 406 ⁇ of a 32% w/v solution of sodium hydroxide is added to the solution formed in the second step.
• a fourth step 25.45ml of a 2.36M solution of sodium carbonate is added to the solution formed in the third step.
• a material on which the pH indicating dye is to be bound is placed in the solution and left to react for approximately 1- 2 hours.
• suitable materials include, but are not limited to: TENCEL fibres of the Durafiber product, polyurethane foam of the Allevyn product, cellulose pad of the Opsite Post-op product, or K5 adhesive-coated polyurethane film, all available from Smith & Nephew, Inc. The material is then washed with distilled water until no dye is released. The material is then dried.
• a sample of the pad from an Opsite Post-Op dressing (Smith & Nephew, Inc) was prepared in different samples, and each sample was covalently bound with one or a combination of phenylazo dyes, selected from GJM-514, GJM-492, GJM-546, and GJM-534.
• the structures of these dyes are shown in Table 1. It was discovered that these dyes had colour-changing characteristics that varied according to changes in pH.
• the Post-Op samples were covalently bound with GJM-514 alone or with GJM-514 combined with one of GJM-492, GJM-546 and GJM-534 using the method as described above in relation to Figures 1-3.
• the Post-Op material was exposed to buffered solutions having a pH of 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9 and 9.5.
• Colour pen measurements include, but are not limited, to three different readings: the L*, a* and b* values.
• Table 2 illustrates the colour pen measurements (L*, a* and b*) of the colour of the GJM-514 dye over a pH range of pH 5 - pH 9.5.
• An optimal dye for use as a pH indicator is one which demonstrates a linear change in a measurement of a specific parameter of colour (for example L*, a* or b*) over a broad pH range. Outside of the linear region, the dye is either unable to change colour in response to a change in pH or the change in colour is so minimal that it is undetectable.
• Figures 4A and 4B illustrate the L* measurements taken of the GJM-514 dye with the colour pen presented graphically.
• the L* results of Figure 4A show that the L* value decreases from pH 5.5 to pH 9.5 as the luminosity of the dye decreases relative to the increasing pH.
• These results have also been plotted in Figure 4B and demonstrate a linear region between pH 7.5 and 9.5.
• the trend line has a gradient of -8.18 and an R 2 value of 0.9918.
• Figures 4C and 4D illustrate the a* measurements taken of the GJM-514 dye with the colour pen presented graphically.
• Figure 4C illustrates the a* measurements taken at various pH values between pH 5 - pH 9.5.
• Figure 4D illustrates the a* measurements at various pH values over the linear portion of the trend line, between pH 7.5 and 9. The trend line has a gradient of 10.94 and an R 2 value of 0.9997.
• Figures 4E and 4F illustrate a graphical representation of the b* measurements taken of the GJM-514 dye.
• Figure 4E shows the b* measurements taken at various pH values between pH 5 - pH 9.5.
• Figure 4E illustrates the b* measurements at various pH values over the linear portion of a trend line. From Figure 4E it can be seen that the values are fairly consistent and steady between pH 5.5 and pH 7, and after pH 7 they start to decrease.
• Figure 4F shows that the results give a linear downward trend between pH 7.5 and pH 9, with a gradient of -14.34 and an R 2 value of 0.991.
• the most accurate working range for GJM514 is between pH 7.5 and pH 9.
• the linear trend line of the b* measurements has a steeper gradient (-14.34) than the a* measurements (10.94) and therefore b* would be used preferentially to give a more accurate indication of the pH of the dressing when using an optical reader rather than the human eye.
• Example 2 Post-Op Pad dved with GJM-514: GJM-492 (1 :1)
• Table 3 illustrates the colour pen measurements (L*, a* and b*) of the colour of the GJM-514 : GJM-492 dye combination over a pH range of pH 5 - pH 9.5.
• Figures 6A illustrates the L* measurements taken with the colour pen presented graphically.
• the L* results presented in Figure 6A show that the value for L* decreases over the range of pH 5.5 to pH 9.5 but does not follow a linear downward trend. The L* value is therefore not considered to be a reliable indicator of the colour change of this dye combination over the pH range tested.
• Figures 6B and 6C illustrate the a* measurements taken with the colour pen presented graphically.
• Figure 6B illustrates the a* measurements taken at various pH values between pH 5 - pH 9.5.
• Figure 6C illustrates the a* measurements at various pH values over the linear portion of a trend line.
• Figure 6D illustrates a graphical representation of the b* measurements taken with the colour pen. It can be seen that there is not a significant change in b* value, but there is a downwards trend.
• Table 4 illustrates the colour pen measurements (L*, a* and b*) of the colour of the GJM-514 : GJM-546 dye combination over a pH range of pH 5 - pH 9.5.
• Figures 8A and 8B illustrate a graphical representation of the L* measurements taken with the colour pen.
• Figure 8A shows all data points whilst Figure 8B is a re-plot of the data points in the linear region between pH 5 to pH 8.
• the trend line has a gradient of -6.3702 with an R 2 value of 0.9982.
• Figures 8C illustrate the a* measurements taken with the colour pen presented graphically over the pH 5 - pH 9.5 range. The results are too variable for the a* measurement to be considered of use in reliably measuring a colour change in the GJM 514:546 dye combination in response to changes in pH.
• Figures 8D and 8E illustrate a graphical representation of the b* measurements taken with the colour pen. Figure 8E shows the b* measurements taken at various pH values between pH 5 - pH 9.5 and it can be seen that the results follow a downward trend from pH 5 to pH 8, but it appears to plateau after pH 8.
• Figure 8E illustrates the b* measurements at various pH values over the linear portion of a trend line which has a gradient of -18.3 and an R 2 of 0.9997. As the b* results gave a steeper gradient it is believed that monitoring the b* value would give a more accurate reading of the pH from the dressing colour.
• the working range for this dye combination appears to be pH 6 to pH 7.5.
• Example 4 Post-Op Pad dved with GJM 514:534 ⁇ : 1)
• Table 5 illustrates the colour pen measurements (L*, a* and b*) of the colour of the GJM-514:GJM-534 dye combination over a pH range of pH 5 - pH 9.5
• Figures 10 ⁇ and 10B illustrate a graphical representation of the L* measurements taken with the colour pen.
• Figure 10A shows all data points whilst Figure 10B shows only those data points in the linear region.
• a general downward trend from pH 6 to pH 9 is observed.
• the trend line has a gradient of -8.8286 and an R 2 value of 0.9742.
• Figures IOC and 10D illustrate the a* measurements taken with the colour pen presented graphically.
• Figure IOC illustrates the a* measurements taken at various pH values between pH 5 - pH 9.5.
• Figure 10D illustrates the a* measurements at various pH values over the linear portion of a trend line. The results demonstrate an upwards trend between pH 6 to pH 9, with the trend line having a gradient of 6.6335 and an R 2 value of 0.9924.
• Figures 10E and 10F illustrate a graphical representation of the b* measurements taken with the colour pen.
• Figure 10E shows the b* measurements taken at various pH values between pH 5 - pH 9.5 and it can be seen that the results follow a downward trend until pH 9.
• the trend line illustrated in Figure 10F has a gradient -16.314 and an R 2 value of 0.9925 between pH 6 and pH9- From the colour pen measurements the working range of this dye combination is between pH 6 and pH 9, and the b* value could be used to accurately measure the pH from the material colour.
• Example 5 Post-Op Pad dved with GJM 514:534 (1 :0.5091
• Table 6 illustrates the colour pen measurements (L*, a* and b*) of the colour of the GJM-514:GJM-534 dye combination over a pH range of pH 5 - pH 9.5
• Figures 12A illustrates a graphical representation of the L* measurements taken with the colour pen. A general downward trend from pH 6 to pH 9.5 is observed.
• Figures 12B and 12C illustrate the a* measurements taken with the colour pen presented graphically.
• Figure 12B illustrates the a* measurements taken at various pH values between pH 5 - pH 9.5.
• Figure 12C illustrates the a* measurements at various pH values over the linear portion of a trend line. The results demonstrate a linear upwards trend between pH 6.5 to pH 8.5, with the trend line having a gradient of 8.72 and an R 2 value of 0.9987.
• Figures 12D and 12E illustrate a graphical representation of the b* measurements taken with the colour pen.
• Figure 12D shows the b* measurements taken at various pH values between pH 5 - pH 9.5 and it can be seen that the results follow a downward trend between pH 6 and pH 8.5.
• the trend line illustrated in Figure 12E has a gradient 15.9 and an R 2 value of 0.9833. Taking into account the colour pen results and the photographs of the samples, the working range of this dye combination is between pH 6 and pH 8.5, and the b* value could be used to accurately measure the pH from the material colour. Examples 6 and 7
• a sample of a gauze (Kerlix Trademark of Covidiene) and polyvinyl alcohol foam (V.A.C. WhiteFoam, trade mark of KCI) were covalently bound with the dye GJM-546 and 492 in a ratio 1 :3.92 as described thoughout this disclosure.
• NGWT Negative Pressure Wound Therapy
• Using a scalpel create 2 wounds each approximately 50mm in diameter and 25mm deep in the tissue (and at least 2cm apart), by removing the skin/fat/muscle, with a relatively fiat bottom and minimal tissue flaps.
• the pH sensitive gauze and VAC foam were washed after the first meat model experiment and then used in an additional wound model, with pH adjusted water.
• the extra piece of pH sensitive dyed gauze was placed in a clear Perspex wound model and fluid pumped through.
• the foam was orange in colour when it was loaded into the wound, but the gauze was more of a red colour. It is believed the gauze is red in colour due to the presence of PHMB on the gauze which would make it basic.
• the experiment was started by pumping pH 5 horse serum into the wound filler for approximately 2.5 hours before fluid started to appear in the canister and the material started to change colour. After approximately 5.5 hours the pH 5 horse serum solution was changed to pH 8 horse serum and this was run overnight. In the morning the solution was then changed back to pH 5 horse serum and was pumped in for several hours (due to time restrictions the flow rate was increased to 80 ⁇ 1/ ⁇ after 3.5 hours).
• the basic aqueous solution was used first and was left pumping into the model overnight. The next morning the solution was then changed to an acidic aqueous solution and left pumping for several hours.
• the experiment was also carried out using the pH sensitive dyed gauze in a clear Perspex wound model to be able to visualise the colour change throughout the wound.
• the fluid was not pumped in from the bottom on this occasion but from the left hand side of the wound as seen on the images in Figures 17A to H.
• Both the pH sensitive dyed VAC foam and gauze changed colour as they were exposed to different pH solutions.
• the colours for indicating the different pH's were clearly visible, and the colour could be reversed by addition of the other pH solution to the wound.

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