JPH06503162A - Sensor for peracetic acid-hydrogen peroxide solution - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Sensor for peracetic acid-hydrogen peroxide solution Background of the invention Expensive equipment used especially in medical and dental applications is cleaned and sterilized before reuse It has become generally accepted that the water needs to be recycled. like that Much of the equipment for the purpose is actually very specialized to ensure that it is sterile. Requires manual operation. The use of heating means to perform sterilization as described above is It is often impractical and therefore various chemical disinfectants have found use. Sterilization Applicable to materials that will be used for sterilization before they are actually used for sterilization. It is extremely important that there is a high degree of reliability to ensure that the mixture is mixed. messenger It usually starts with a concentrate of the active material to be used and the desired amount for the actual sterilization. dilute them with water to the desired extent. It is important that the active material is diluted accurately. be.

Peracetic acid-hydrogen peroxide type disinfectants have been known for a long time. Disinfectant is acetic acid and peroxide By mixing with hydrogen to obtain an equilibrated solution of peracetic acid, acetic acid and hydrogen peroxide. manufactured by When properly mixed and diluted, these solutions contain more than just bacteria. It has shown great utility in eradicating various other microorganisms. Peracetic acid for disinfection - There is a large body of literature and patent material dealing extensively with hydrogen peroxide solutions. exist. U.S. Patent Nos. 4,051,058 and 405 to Boeing No. 1059, but is not limited thereto.

For further background to the field of peroxide and hydrogen peroxide use on microorganisms, Text by Daniel Swern “Organic Peroxides J and M, G, C. Boldry r Microbicidal, bactericidal and sporicidal properties of hydrogen peroxide and peracetic acid Bacteriology JJ, AIIp, Bacteriology 54.417-423 Attention is also drawn to

A machine that cleans and sterilizes dialysis machines and allows them to be reused is U34517 It is described in No. 081. This machine will load each dialysis machine in a predetermined order. Includes means for passing a series of cleaning, disinfecting and rinsing solutions through the compartment. storage A predetermined dilution of the solution is achieved by storing a controlled amount of the solution in the liquid tank inside the machine. and a microprocessor-controlled manifold for introducing water. This is done in a liquid tank. Commercially available embodiments of the invention described above have both cleaning and sterilizing functions. Different concentrations of peracetic acid-hydrogen peroxide solutions are used for this purpose.

Peracetic acid-hydrogen peroxide solutions are inherently unstable and therefore degrade with aging. exposed to changes in the concentration of the active peroxide component. Very concentrated solutions are more stable It is. Conventional commercially available highly concentrated hydrogen peroxide solutions are Conveniently as a storage solution in machines such as those described in No. 4517081 It must be diluted manually before it can be processed.

Predilution cleans and sterilizes the dialysis machine in its dilution and for that purpose The final concentration and uniformity within the diluted concentrate of peracetic acid and hydrogen peroxide used for leading to the possibility of human error. If the diluted substance is too dilute, There remains a significant risk of residual viable bacteria. If it is too concentrated, remove the fungicide. may result in insufficient rinsing and may also damage the material being sterilized.

Conductivity measurements are measurements of solute concentration in a solvent and other measurements indicated by changes in liquid concentration. It has been widely used for the measurement of parameters. For example, blood conductivity measurements are US3985123, US4572206, US4380237 and Bour dil1on, etc., Med, & Biol, Eng.

As described in A. Camput, 17.323-329 (1979) It has been used to monitor cardiac output.

Also, conductivity measurements for monitoring the concentration of solutes in aqueous solutions are well known. Ru. Until now, such measurements have been used to monitor peroxide/peracetic acid solution concentrations. It is certain that it has not been used.

Summary of the invention Because of the potential for error in diluting the peracid-peroxide stock solution, the final solution may be dialyzed. The storage solution is not so strong that there is a risk of damaging the equipment or cleaning machinery; storage solutions so that the final solutions are not so weak that they lose their cleaning and disinfecting properties. There is a need to monitor The present invention achieves these objectives and The concentration and purified water must be combined prior to their actual use in cleaning and disinfection systems. Provide special electrodes and electronic systems to ensure proper mixing occurs .

The present invention also provides for the use of concentrates and water as a preliminary step in the actual sterilization of various accompanying equipment. Concerning the entire system for monitoring the formulation of. In more detail, it is peracid Found to be extremely suitable for hydrogen chloride-containing solutions and peracetic acid-hydrogen peroxide type disinfectants. used in combination with specific electrodes.

Therefore, as one aspect of the invention, for subsequent use as a cleaning agent and disinfectant, A device that automatically dilutes a stock solution of peracetic acid and hydrogen peroxide in a dilution tank for determine the value of the concentration-dependent parameter of the storage solution, and the value is predetermined. said equipment is equipped with concentration sensing and warning means to warn if the concentration is outside the specified range. The apparatus is disclosed including improvements therein.

In another aspect of the invention, a pair of spaced apart titanium electrodes, the electrodes being resistivity measuring means coupled to said electrode when in contact with a liquid, said measuring means An output indicating the resistivity of the solution is presented, and the resistivity display output is set within a predetermined range. and the resistivity display output is compared to the acceptable output and the resistivity display output is within the range of acceptable output. Peracetic acid-peroxide consisting of a comparison means to issue a warning signal if outside the range A sensor is provided for measuring resistivity of a hydrogen solution.

Brief description of the drawing Figure 1 is a schematic diagram of a dialysis membrane cleaning and sterilization device equipped with the sensor of the present invention. be.

FIG. 2 is a schematic diagram of a preferred embodiment of the resistivity measurement circuit.

Figure 3 shows the resistance of a solution of hydrogen peroxide in solution without a stabilizer useful in the present invention. Figure 2 is a graph shown as a function of percentage.

Figure 4 shows the plot of the change in resistivity of six different solutions of 21% dilution as a function of temperature. It is a cut.

Description of preferred embodiments Figure 1 shows how to automatically dilute a storage solution into a cleaning and disinfecting solution and circulating them for cleaning membranes or other medical or dental equipment Some of the preferred embodiments of the invention in which the resistivity sensor of the invention is used in a device is shown schematically.

The direction of liquid flow in FIG. 1 is indicated by arrows.

The hydrogen peroxide-peracetic acid stock solution is connected by conduit 15 to dilution tank 18. It is held in a container 10. Valve 30 and conduit 15 are actuated to open the dilution tank. Control the flow of storage solution into tank 1B.

The valve follows a predetermined program to control the circulation of liquid through the device. Therefore, it is controlled by a microprocessor which opens and closes the valve. within conduit 15 A probe 35 spaced upstream of the valve 30 detects the liquid passing therethrough. form a resistivity cell for detecting the resistivity of. Probe 35 is detailed below. to a resistivity measurement circuit 40 that provides an output to a microprocessor as described in electrically connected.

Tank 18 also includes a vacuum source 19, a liquid outlet in communication with the articles to be cleaned. 20 and a water inlet 22 are connected and provided. Although not shown, each A valve is also suitably placed at each inlet and outlet of the microcontroller. controlled by a computer. The output is also supplied to the microcomputer The tank is placed on the load cell 25. The load cell 25 is the dilution tank 18 The volume of liquid in the liquid can be monitored, resulting in pre-programmed dilution and and liquid circulation can be performed by a microcomputer. Construction of such a device For further details regarding and operation, reference is made to US 4,517,081.

The resistivity measurement circuit preferably utilizes a constant voltage source.

FIG. 2 represents the elements of the preferred circuit. Constant voltage source 41 is an IKHz sine wave oscillator from the bipolar electrode probe assembly 42 via the Wheatstone bridge 43 to be applied. Bipolar probe assembly 42 consists of two electrodes 35 in FIG. That is appropriate. The output of the Wheatstone bridge is given a gain of 10, The current detected in the bridge circuit is then applied to the probe assembly. It is supplied to a differential amplifier 44 which converts it into a voltage proportional to the resistance. The amplified signal is Bandpass filter 45, preferably with a center frequency of 1000 Hz and 500 and 15 Regulated by feeding through a 2-ball filter with an Sdb point of 00Hz be done. The conditioned signal is then sent to rectifier 46.

Rectifier 46 is a full wave rectifier circuit with a voltage gain of 2 and its gain temperature compensated. It is suitable to be.

The rectified signal then has an increment of 2 and a non-rectified signal with the capability of offset adjustment. The signal is supplied to an inverting amplifier 47. The signal then passes through an analog-to-digital converter 48. Therefore, we present an 8-bit digital converter code. The converted signal is finally sent to the microphone is sent to the computer 9 where a preprogram of acceptable signal values for the storage solution is sent. compared to the programmed range. Measured signal pre-programmed range If it is, the device will continue to operate normally. outside the acceptable range If so, a device error is displayed and a warning signal is issued. Hear warning signals inducing a sensory or visual warning 50 and also inducing automatic closing of the valve 30; to stop the flow of storage solution into the cleaning device.

In an attempt to develop peroxide/peracid-based resistivity sensors, electrode metals such as stainless steel and other metals, and indeed even conventional platinum or platinum black electrodes was also found to be rapidly corroded by this solution and therefore unsuitable. rotten Signs of eclipse appeared in about a few minutes. However, unexpectedly, titanium The metal electrodes are sufficiently inert and their use in relatively concentrated peroxide/peracid solutions It has been found that it is possible to use Titanium electrodes show signs of corrosion after several weeks of immersion. It showed no symptoms.

Preferably, the electrode is titanium having a round profile with a hemispherical end shape.

The electrodes typically have a diameter of 0.25" and may have a center-to-center spacing of about 1.0". .

The resistance of the solution is over a fairly wide temperature range, including normal room temperature of about 18-25°C. The rate of spread is constant.

As a result, it can be eroded little or not at all by normal temperature changes.

A verification test was attempted on the specific peracetic acid-hydrogen peroxide mixture used, and Concentration limits that may be used to set warning levels in computers It is recommended to establish a curve for

During operation, commercially available peracetic acid-hydrogen peroxide concentrates [e.g. It is a registered trademark Renalin (Renalin@) available from Minchitsuk Co., Ltd. ] is prediluted in container 10 to a stock solution. Renarin is Hlo, The nominal composition of the concentrate is approximately 23%, peracetic acid 5% and acetic acid balance H3O 9%. have

The dilution tank 18 is tared with a load cell 25.

Valve 30 is then opened and vacuum source 19 draws the stock solution into the dilution tank. Let it sink in. When the stored solution flow passes through the electrode 35, the resistance of the solution is computed. checked by the controller to ensure it is within a preprogrammed range of acceptable values. Check. If the predetermined amount is within an acceptable range, the load cell stored until flushed as directed by the valve 30, at which point the valve 30 is closed. Solution continues to flow into the dilution tank. Water enters the tank 18 through the water inlet 22 added and the stock solution is used for the initial cleaning or bacteria removal operation. 1 depending on the crab. Dilute to 7% or 3% hydrogen peroxide concentration.

When encountering a resistivity output that exceeds the output that has been certified as acceptable by a substantial deviation, If the dilution series a warning 50 which closes the valve 30 and alerts the operator to the error condition; emits. The stock solution can then be replaced, the dilution tank flushed, and the dilution tank flushed. The interpretation operation is started again.

The invention may be illustrated by the following non-limiting examples.

Example In the following examples, in cleaning and sterilizing dialysis membrane reuse equipment as described above, Suitable stock solutions for use include concentrates, such as renarin in highly purified water in the examples. (2 liters of The concentrate is diluted to 9.46 liters (2.5 gallons)). Resistance measurement is stored made to the solution.

Example I A stock solution is prepared from the concentrate as described above and the resistance is measured with the sensor of the invention. It was. Figure 3 is a plot of measured resistance as a function of initial peroxide concentration. Ru. The virtually linear sekiho is the resistance of a mixture of peracetic acid and peroxide concentrations in a complex solution. shows that the rate can be successfully monitored.

Example■ Temperature and aging dependence A hydrogen peroxide-peracetic acid stock solution was used in this example. The storage solution is Prepared for Ingredients: Renarin diluted to 21% concentrate to make stock solution . They are tested when freshly prepared and after standing for several days, and It was written as E-Fresh and E-Aged.

Other formulations were made and tested with the following composition: A, 30% H, Ot, 12.85% HOAc, yielding a peracetic acid concentration of about 5%.

B, 27% HtOz, 12.85% HOAc + about 5% peracetic acid concentration was obtained. It will be done.

0.24% Hoot, 12.85% IOA, c, peracetic acid concentration of about 4% is obtained.

The resistance of the storage solution prepared as above was measured and the titanium Fresh storage solution and aged storage using a resistivity cell with electrodes Plotted as a function of temperature for both stock solutions. As can be seen in Figure 4 The resistivity plot, as measured, is essentially flat, with temperatures ranging from about 15°C to It shows virtually no temperature dependence over a room temperature range of 26.6°C. upper curve is for renarin concentrate as a starting point, and the lower curve is for formulation A. , for B and C.

Although the invention has been described above with respect to preferred embodiments, it is understood that the invention It will be readily apparent that this is not limited to. For example, the sensor may be used in dental or It can be extremely usefully used in machines for cleaning and sterilizing medical equipment and the like. skilled in the art These and other variations within the art include the following claim terms and their shall be considered within the scope of this invention to be limited only by legal equivalents thereof. be.

Submission of translation of written amendment (Article 184-8 of the Patent Law)

Claims (11)

[Claims] 1. Storage of peracetic acid and hydrogen peroxide for subsequent use as a cleaning agent and disinfectant In devices that automatically dilute solutions, the composition peroxide concentration of the stock solution meter and ensure that the value is outside the predetermined acceptable range. An improvement in which said device comprises concentration and detection means for emitting a mule warning signal. The apparatus comprising: 2. Claim in which the concentration and sensing means consist of a resistivity measuring cell with titanium electrodes. The device according to item 1. 3. Said concentration and sensing means are in communication with said electrode and have an output indicative of the resistivity of the solution. resistivity measuring means for presenting a force, receiving the resistivity display output within a predetermined range; and the resistivity display output is outside the acceptable range. 2. The device as claimed in claim 1, further comprising comparison means for issuing a warning signal in the event of an error. 4. The resistivity measuring means presents a signal that is sequentially provided via a differential amplifier. A constant voltage source that applies a constant voltage to the electrode through a bridge circuit, and a bandpass filter. a rectifier, a non-inverting amplifier and a digital signal indicative of the resistivity of the solution. 4. The apparatus of claim 3, further comprising an analog-to-digital converter. 5. The digital signal is the resistivity display output, and the comparing means is the resistivity display output. A microcomputer preprogrammed with a predetermined range of acceptable output signals. 5. The apparatus of claim 4, comprising a computer. 6. said warning procedure for interrupting operation of the device when said warning signal is issued; 2. The apparatus of claim 1, further comprising step-responsive deactivation means. 7. a storage solution tank for holding said storage solution before dilution, said dilution taking place; the dilution tank and the conduit between said tanks, to be closed in response to said warning signal. Claim 6 further comprising deactivation means comprising a valve in said conduit which is controlled to The device described. 8. To measure the resistivity of a peracetic acid-hydrogen peroxide solution consisting of a pair of titanium electrodes sensor. 9. resistivity measuring means in communication with said electrode and providing an output indicative of the resistivity of the solution; , comparing the resistivity display output to a predetermined range of acceptable outputs; and to issue a warning signal if the resistivity display output is outside an acceptable range; 9. The sensor according to claim 8, further comprising comparison means. 10. The resistivity measuring means provides a signal that is sequentially supplied via a differential amplifier. A constant voltage source that applies a constant voltage to the electrode through the bridge circuit shown in FIG. Obtain a digital signal indicative of the resistivity of the resistor, rectifier, non-inverting amplifier and said solution. 10. The sensor of claim 9 comprising an analog to digital converter for. 11. the digital signal is the resistivity display output, and the comparison means is the A microcontroller preprogrammed with a predetermined range of acceptable output signals. 10. The sensor according to claim 9, comprising a computer.