PRESENCE OF A MARKER MOLECULE IN A SOLUTION

Field of the invention The present invention relates to a detergent composition for use in a water utilizing appliance such that the detergent composition enables selection of an enhanced mode of operation of the appliance, and in a further aspect, the present invention relates to a method for detecting presence of a marker molecule in a solution of the detergent composition.

Background of the invention

Processes such as chemical processes or cleaning processes requiring chemical ingredients or formulations as their input raw material, depend significantly on the purity and compositional correctness of the chemical ingredients or formulations. When such processes are brought into the consumer domain in the form of devices and machines, it is important to ensure that the consumer uses only the formulations that are formulated specific to the process. In case the consumer uses a non-specific formulation in such processes, it could not only lead to the failure of the process but also to the damage of the device/machine (either reversible or irreversible damage), it may also potentially lead to unsafe situations for the consumer.

Therefore there is a need to provide a device to control the quality or composition of a formulation to initiate or stop a machine or process. One way to control the formulation is to incorporate a sensor in the machine or process to detect whether the appropriate formulation is used in the machine or not. Such sensor may be provided in the reservoir of the fluid formulation or in the passage between reservoir and the location in which process occurs.

US patent publication US 5,441 ,61 1 discloses a method for determining the concentration of an iodine or iodide-containing active substance in aqueous solutions. Electrodes are used to perform a potentiometric measurement, wherein the electrodes are arranged to behave selectively towards iodide ions. This requires specific electrodes which are only suitable for detection of a specific active substance. International patent publication WO 2016/030713 discloses an apparatus and method for detection and quantification of biological and chemical analytes. The apparatus uses two electrodes to which a holding voltage is provided such that an analyte in an analytical sample polarizes and diffuses towards one of the electrodes. Subsequently, a pulsating sweep voltage is applied to the two electrodes, and a current-voltage profile and/or a capacitance-voltage profile is measured. The analyte is then determined based on the measured current-voltage and/or capacitance-voltage profile.

U.S. patent publication US 2007/0235346 discloses methods and devices for determining the concentration of a constituent in a physiological sample. The physiological sample is introduced into an electrochemical cell having a working and counter electrode. At least one electrochemical signal is measured based on a reaction taking place at the cell. The preliminary concentration of the constituent is then calculated from the electrochemical signal. This preliminary concentration is then multiplied by a hematocrit correction factor to obtain the constituent concentration in the sample, where the hematocrit correction factor is a function of the at least one electrochemical signal.

Summary of the invention

The present invention seeks to provide a detergent composition for use in a water- utilizing appliance, that allows for selection of an enhanced mode of operation of the appliance, based on the detection of a marker molecule in the solution of the detergent composition, where the enhanced mode comprises treatment of waste water generated during use of the appliance. The present invention also provides a method of selecting an enhanced mode of operation in a washing machine and a sensor assembly for detecting the presence of a marker molecule in a solution of the detergent composition. According to the present invention, a detergent composition for use in a water utilizing appliance is provided, wherein the detergent composition comprises a marker molecule; and a surfactant, wherein the marker molecule is capable of being detected in a solution of the detergent composition by a sensor assembly in the appliance, wherein the appliance is arranged to select between a normal mode of operation and an enhanced mode of operation based on the detected absence or presence of the marker molecule in the solution of the detergent composition during the operation of the appliance, and wherein the enhanced mode of operation comprises treatment of waste water generated during use of the appliance. The marker molecule is capable of being reversibly reduced or oxidized in response to a plurality of applied potential levels.

In a further aspect, the present invention relates to a method of selecting an enhanced mode of operation in a washing machine during a laundry wash cycle comprising utilizing a detergent composition comprising a marker molecule; and a surfactant. The method further pertains to detecting the marker molecule in a solution of the detergent composition during the wash cycle. The marker molecule is capable of being reversibly reduced or oxidized in response to a plurality of applied potential levels. The marker molecule is detected by a sensor assembly in the washing machine. The sensor assembly detects the marker molecule by detecting a unique electrochemical signature generated by the marker molecule.

The sensor assembly of the present invention comprises of: a pulse generator unit (2) for generating a pulse train, a current measurement unit (3), at least two electrodes (8, 9) in contact with the solution of the detergent composition, and connected to the pulse generator unit (2) and the current measurement unit (3), the pulse generator unit (2) being arranged to supply a pulse train to the at least two electrodes (8, 9) during operation, the pulse train comprising at least two subsequent pulses, each having a pulse level (Vx, Vy), wherein the pulse levels (Vx, Vy) are selected from a plurality of pulse levels associated with marker molecule oxidation or reduction events, and the current measurement unit (3) being arranged to measure at least two total current responses (TR1 , TR2) during each of the associated pulses (Vx, Vy), to determine at least one ratio value (PR) of the at least two total current responses (TR1 , TR2).

The detection of the unique electrochemical signature generated by the marker molecule by the sensor assembly comprises matching the at least two total current responses (TR1 , TR2) and the at least one ratio value (PR) with predetermined characteristic values associated with the marker molecule in the solution. The washing machine selects between a normal mode of operation and an enhanced mode of operation based on the detected presence of the marker molecule in the solution of the detergent composition. The enhanced mode of operation comprises treatment of waste water generated by the use of the appliance. The present invention embodiments allow to provide a highly accurate, robust and reliable detection of a marker molecule in a solution, allowing application of enhanced operating modes in many appliances, such as washing machines.

Figures (short description)

Fig. 1 shows a schematic drawing of an appliance, for e.g., a washing machine having a sensor assembly according to an embodiment of the present invention;

Fig. 2A-2C show timing diagrams of a pulse train as used in various embodiments of the present invention. Figs. 3A-3B demonstrate the specificity achieved by the methods disclosed herein. Fig. 3A shows the voltametric profile of 200 ppm of Kl (blue) and 200ppm of triethanolamine(TEA). Fig. 3B compares the electrochemical signal (current response) generated in response to multiple potentials applied for detergent (alone), detergent with 200ppm of Triethanolamine (TEA), detergent with 600 ppm of TEA, and detergent with 200 ppm of Kl.

Detailed description of the invention

According to the present invention embodiments, a specific detergent composition for use in a water utilizing appliance is provided. The detergent composition comprises a marker molecule; and a surfactant. The marker molecule is capable of being detected in a solution of the detergent composition by a sensor assembly in the appliance, wherein the appliance is arranged to select between a normal mode of operation and an enhanced mode of operation based on the detected absence or presence of the marker molecule in the solution of the detergent composition during the operation of the appliance. The enhanced mode of operation comprises treatment of waste water generated during use of the appliance.

In a further aspect, the present invention relates to a method of selecting an enhanced mode of operation in a washing machine during a laundry wash cycle comprising utilizing a detergent composition comprising a marker molecule; and a surfactant. The method further pertains to detecting the marker molecule in a solution of the detergent composition during the wash cycle. The marker molecule is capable of being reversibly reduced or oxidized in response to a plurality of applied potential levels. The marker molecule is detected by a sensor assembly in the washing machine. The sensor assembly detects the marker molecule by detecting a unique electrochemical signature generated by the marker molecule.

Additionally, the present invention pertains to a specific sensor assembly and method for detecting presence of a marker molecule in a solution. The marker molecule may be selected based upon the specific application where the invention embodiments are applied. E.g. in detergents used in washing machines, potassium iodide (Kl) may be added as marker molecule, without negative effect on the detergent itself. By applying the present invention embodiments, detecting the marker molecule in the detergent solution may be executed in a reliable and robust manner.

With reference to the schematic drawing of Fig. 1 (discussed in more detail below), a sensor assembly is provided in a first embodiment of the present invention, which comprises comprising a pulse generator unit 2 for generating a pulse train, a current measurement (and integration) unit 3, and at least two electrodes 8, 9 connected to the pulse generator unit 2 and the current measurement unit 3. The pulse generator unit 2 is arranged to supply a pulse train to the at least two electrodes 8, 9 during operation, the pulse train comprising at least two subsequent pulses each having a pulse duration and a pulse level Vx, Vy, wherein the pulse levels Vx, Vy are each associated with a different reduction or oxidation event of the marker molecule in the solution.

It is noted that the redox event is either an oxidation event or a reduction event, depending on the marker molecule in the solution and further characteristics of the solution. Further, the present invention utilizes marker molecules that are capable of undergoing at least two reduction or oxidation events at two different pulse levels. The current measurement unit 3 is arranged to measure at least two total current responses TR1 , TR2 during the associated pulses (Vx, Vy), to determine at least one ratio value PR of two of the at least two total current responses TR1 , TR2, and to match the at least two total current responses TR1 , TR2 and the at least one ratio value PR with predetermined characteristic values associated with the marker molecule in the solution, which comprises the unique electrochemical signal of the marker molecule. In combination such a sensor assembly 1 may be referred to as a multiple pulse chrono amperometry unit.

As mentioned above, the sensor assembly 1 may be used as part of a washing machine 10, as schematically shown in Fig. 1. The washing machine 10 (or more general an appliance 10) comprises a process chamber 1 1 (i.e. the washing drum) and a solution reservoir 12, which in operation comprises a solution 13 (e.g. a detergent in solution). The sensor assembly components as described above (pulse generator unit 2 and current measurement unit 3) are also shown in this schematic view, as are the electrodes 8, 9 which are directly connected to the pulse generator unit 2. The current measurement unit 3 may be interfacing with the electrodes 8, 9 directly, or via the connection leads to the pulse generator unit 2, as indicated by the arrow 5 as input to the current measurement unit 3. The process chamber 1 1 of the washing machine 10 is controlled by a data processing unit 4, e.g. using a control signal 6 for a process initiation (e.g. starting a specific part of a washing cycle). In the embodiment shown, the process chamber 1 1 provides a control signal 7 to the pulse generator unit 2 in order to allow initiation of the sensor assembly 1 . It is noted that the data processing unit 4 may be a stand-alone unit with the indicated interfaces, it may be part of the washing machine 10 itself, or it may be part of the sensor assembly 1 (e.g. as part of the current measurement unit 3). Furthermore, the control signalling between the machine 10 and the sensor assembly 1 may be physically different, e.g. by having all of the control signals 6, 7 being routed via the data processing unit 4.

More generally, the present invention embodiments in further aspects relate to an appliance 10 comprising a sensor assembly 1 according to any one of the present invention embodiment, wherein the appliance 10 is arranged to select between a normal mode of operation and an enhanced mode of operation based on a detected presence or absence of the marker molecule in the solution. In a specific embodiment, the appliance 10 is a washing machine, and the enhanced mode of operation comprises treatment of wastewater, e.g. by flocculation or coagulation, intended for re-using (part) of wastewater in washing machine 10. The sensor assembly 1 according to the present invention embodiments may be used for controlling an appliance (a machine or a process) by controlling the quality of a fluid formulation to be introduced in the appliance. The sensor assembly 1 comprises electrodes 8, 9, which may be positioned inside the reservoir 12 that holds the solution (or fluid formulation) or in a passage between the reservoir 12 and the location in which the process occurs, i.e. process chamber 1 1 . The combination of pulse generator unit 2, current measurement unit 3 and data processing unit 4 (as described with reference to Fig. 1 ) provides the required input parameters to the electrodes 8, 9 of the sensor assembly 1 and also receives/measures the output of the electrodes 8, 9, in order to allow analysis of the output of the electrodes 8, 9 and decision making to initiate the chemical process or not.

In an actual implementation, the sensor assembly 1 is used to detect the presence of a marker molecule, e.g. potassium iodide (Kl) in a detergent to control specific washing cycle applications in a washing machine 10. E.g. when using the correct detergent type, the washing machine 10 may have the capability to execute a specific washing cycle under the right conditions for flocculation to occur for recycling water. If an incorrect detergent type were to be used with that washing cycle, the desired effect (flocculation) may not occur, and worse, it could possibly lead to irreversible damage of the washing machine 10. A different type of application would be in a washing machine 10 allowing spot stain removal using a spray technique, provided that the correct detergent is used. Usage of an inappropriate detergent type could then even lead to an inhalation safety issue. An even further alternative or additional application would be a (washing) machine 10 having a water recycling capability, provided a specific type of detergent (solution) is used.

In the present invention embodiments, the detection of the presence (or absence) of a marker molecule in a solution used in the machine 10, is based on amperometry, in a specific application. In the art a marker detection technique is known based on single pulse chrono amperometry (SPCA). In SPCA, a pulse with an amplitude that matches with the oxidation potential of iodide (the marker molecule) is applied across the sensor electrodes. The sensor was arranged to differentiate between detergent liquids with and without iodide. However, this known SPCA technique possesses an inherent disadvantage in terms of specificity. Any component in the sample that possesses an oxidation potential less than or equal to that of iodide could be wrongly sensed by the sensor as iodide. As shown in the timing diagram of Fig. 2A, at initiation of a test sequence (control signal 7 to pulse generator unit 2) before allowing initiation of a special process part or feature of the machine 10, the pulse generator unit 2 sends a pulse train to the electrodes 8, 9 having (at least) two subsequent pulses each having a pulse duration (as indicated one from to-ti and the next from ti-t.2) and a (constant) pulse level Vx, and Vy, respectively. The current measurement unit 3 is continuously monitoring the current flowing between the electrodes 8, 9. The data processing unit 4 acquires the current values and sums up these values during a measurement interval (i.e. an integration calculation), which is within each pulse duration, to obtain the respective total current responses TR1 , TR2. Further calculation is performed to obtain the ratio value PR. Each of these values TR1 , TR2 and PR are then matched to predetermined threshold values characteristic for the specific marker molecule. If the values match, the data processing unit 4 sends the control signal 6 for process initiation to the process chamber 1 1 for allowance of the special process in the machine 10. In a further embodiment, the current measuring unit 3 is further arranged to measure the at least two total current responses by applying an integration of a measured current value over a predetermined part of the pulse duration. It is e.g. possible to not use the full pulse durations to-ti and t-i-t.2, but only a characterizing part thereof, e.g. summing with a sampling interval (e.g. 0.2 sec) over a part of the pulse period (e.g. 5 sec). This allows to focus on the specific characteristic parts of the measured signal, or it would also allow time for performing further calculations.

In an exemplary embodiment, the at least two subsequent pulses have a time period to- ti and t-i-t.2 of 0.1-15 sec. This would provide a measurable redox response in the solution with the marker molecule as a result of applying the pulse train to the electrodes 8, 9. To improve long term stability of the sensor assembly, the pulse generator unit 2 is, in a further embodiment, further arranged to supply the pulse train with a lead pulse preceding the at least two subsequent pulses, the lead pulse having a lead amplitude lower than the pulse levels Vx, Vy. This allows for electrochemical preparation of the electrodes 8, 9 of the sensor assembly, without initiating a first redox response by the marker molecule.

In an additional or alternative embodiment, the pulse generator unit is further arranged to supply the pulse train with a polarity reversal pulse after a last one of the at least two subsequent pulses, the polarity reversal pulse having an amplitude Vr opposite to the pulse levels Vx, Vy. An example of such a pulse train is shown in the timing diagram of Fig. 2C. The amplitude of the polarity reversal pulse has a magnitude (Vr) which is equal to the highest value of the pulse level (Vx, Vy) of the at least two subsequent pulses, in an even further embodiment. The polarity reversal pulse is applied to recondition the electrodes 8, 9 for a subsequent test sequence.

Fig. 2b shows a timing diagram of a pulse train generated by the pulse generator unit 2 of an even further embodiment. The pulse train here comprises three subsequent pulses of increasing amplitude Vi - V2 - V3. The detection method can then be made more robust, as even more data can be obtained and compared to characterising threshold values associated with a specific marker molecule. In an exemplary embodiment, the marker molecule is potassium iodide (Kl), and the pulse levels Vx, Vy are selected from the group of associated potassium iodide Kl oxidation events at different pulse levels. Depending on the circumstances such as pH level, and characteristics of the electrodes 8, 9, the different pulse levels for Kl are e.g. 0.6V, 1.1V, and 1.6V. The current measurement data TR1 , TR2 of two of the pulse levels may be used, e.g. the combinations for two pulses at 0.6V/ 1.1V; 0.6V/ 1 .6V; or 1 .1V /1 .6V. In an even further alternative all three pulse level responses TR1 , TR2, TR3 may be measured, and three pulse ratios may be calculated (TR1/TR2; TR2/TR3; TR1/TR3) and matched with predetermined threshold levels.

The potentials at which the redox events (i.e. oxidation or reduction) for a particular marker molecule occur, can be dependent on the following characteristics of the sensor assembly 1 : Electrode material, electrode system, solution conditions (like pH), etc. The electrode system may comprise two electrodes 8, 9 as described above, however it is also possible to measure the redox potential using a (more expensive) three electrode system (having a working electrode, reference electrode and auxiliary electrode). It is noted that it is possible to use the present invention embodiments in various detergent solution environments, e.g. having a pH value of at least 9 (typical for liquid detergents) up to even 10.8 or even 1 1 (powder detergents). The material of the electrodes 8, 9 may be chosen from conducting materials like metals, carbon, dimensionally stable anodes and mixed metal oxide coated anodes. The electrodes 8, 9 are e.g. made of carbon, platinum, palladium, titanium, gold, silver or platinised titanium. Electrodes 8, 9 that are chemically or enzymatically modified to increase specificity to the marker molecule can also be used.

In an exemplary implementation using a two electrode system with platinized titanium electrodes 8, 9 and potassium oxide Kl as marker molecule, and a solution having a pH level of 10.5, the value of the pulse levels Vx, Vy changes to 1 .1V, 1.4V and 1 .6V.

In a further exemplary embodiment, the marker molecule is gallic acid, and the pulse levels Vx, Vy are selected from the group of associated gallic acid oxidation events at different pulse levels. Gallic acid in a formulation solution at pH7 would exhibit two oxidation potentials Vx, Vy, one at 0.25V and other at 0.9V. Kl is well known to possess an oxidation potential at 0.6V and the same can be used to detect Kl if it is present in detergent formulations. However Triethanolamine (TEA), a molecule commonly used in detergent formulations, exhibits an oxidation event around 0.8V. This oxidation event can potentially be misinterpreted by a sensor as a signal for presence of Kl. Figure 3A shows the voltammetric profile of 200 ppm Kl (blue) and 200ppm TEA (Red). There could be many other molecules like TEA that can possess oxidation events around that of Kl and therefore leading to a possibility of the Kl sensor displaying a false positive for those molecules.

To provide specificity of detection, the present invention exploits the ability of Kl to udergo multiple oxidation events, at a plurality of applied patentials, apart from the 0.6V event. Kl is known to show oxidation peaks at 0.6V, 1 .1V and 1.6V. The methods disclosed herein verifies all the oxidation events associated with Kl not limiting to the event at 0.6V. By verifying the signature reduction or oxidation events specific to a molecule of interest, more specificity is built in for detection of the molecule.

In an exemplary implementation, the sensor is typically placed inside the formulation chamber (referred to as the sensor chamber). The sensor comprises of two electrodes (Electrode 1 and Electrode 2) connected to a pulse generator circuit. The electrodes are physically separated such that the formulation becomes the medium present between the electrodes, and acts as the medium of electrical conduction between the electrodes. The pulse generator is preprogrammed to generate a sequence of pulses, with the amplitude of each pulse corresponding to the respective redox potential of the marker molecule of interest. The current that flows across the electrodes through the formulation, during the application of each pulse is measured using a current measurement module.

Example 1

In an exemplary implementation employing Kl as the marker molecule in a detergent formulation, the test sensor set-up generates two pulses one at 0.6V and another at 1.1V. The measured value of current for the individual pulses (TR1 and TR2) are fed to the data processing unit which evaluates whether the measured values of current (i), along with their ratio (PR), matches with the expected predetermined values

characteristic of Kl, in other words which corresponds to that of Kl (the electrochemical signature for Kl). The data processing unit, thereafter sends a control signal to the process machine, whether to initiate the enhanced process or not.

The calculation of TR involves summation of current values measured after 100mS of the application of pulse (fc) until the end point of the pulse (tf). The data is collected after 100mS in order to eliminate the effect due to charging current.

PR is obtained from the ratio between TR1 and TR2. Example 2

To demonstrate specificity of the methods and compositions disclosed herein, four samples namely detergent alone (without Kl or TEA), detergent formulation containing 200ppm of Kl, 200ppm of TEA, and 600ppm of TEA were analysed one after the other using the above described set-up. Figure 3B shows the current response for the tested samples. The current response for detergent (blue) shows only the baseline current owing to the inherent primary conductivity within the detergent media. 200ppm of TEA (magenta) shows a significant current response only for the 2 ^nd pulse. To check if the response of TEA for the 1 ^st pulse increases at higher concentrations of TEA, the test was reconducted with a detergent sample containing 600ppm of TEA. Even in this case TEA did not show a current response for 1 ^st pulse. Kl on the contrary showed a current response for both 1 ^st & 2 ^nd pulse and the amplitude of the responses and their ratio was significantly different from that of TEA containing detergent. The above described embodiments may be generalized as applications or implementations of a generic method for detecting presence of a marker molecule in a solution, comprising generating a pulse train, supplying a pulse train to at least two electrodes 8, 9 in contact with the solution during operation, the pulse train comprising at least two subsequent pulses each having a pulse duration and a pulse level Vx, Vy, wherein the pulse levels Vx, Vy are each associated with a different redox event (i.e. an oxidation event or a reduction event) of the marker molecule in the solution, measuring at least two total current response TR1 , TR2 during the associated pulse duration, determining at least one ratio value PR of two of the at least two total current responses TR1 , TR2, and matching the at least two total current responses TR1 , TR2 and the at least one ratio value PR with predetermined characteristic values associated with the marker molecule in the solution.

The present invention has been described above with reference to a number of exemplary embodiments as shown in the drawings. Modifications and alternative implementations of some parts or elements are possible, and are included in the scope of protection as defined in the appended claims.