EP0664883A1

EP0664883A1 - Process for determining the concentration of an active agent containing a tracer in active agent solutions

Info

Publication number: EP0664883A1
Application number: EP93921908A
Authority: EP
Inventors: Thomas Müller-Kirschbaum; Alfred Laufenberg; Thomas VIENENKÖTTER; Mike Varpins; Alfred Werner-Busse; Friedhelm Siepmann
Original assignee: Henkel AG and Co KGaA
Current assignee: Henkel AG and Co KGaA
Priority date: 1992-10-13
Filing date: 1993-10-04
Publication date: 1995-08-02
Also published as: DE4234466A1; FI951710A0; WO1994009357A1; FI951710A; JPH08502359A

Abstract

The invention relates to a process for determining the concentration of an active agent containing a tracer in aqueous or non-aqueous solutions of active agents. The concentration is measured via a determination of its tracer contents. The tracer used is a fluorescent colorant which measures the fluorescent colorant in the solution photo-optically and determines the agent's concentration correspondingly from the measurement obtained. The active agent concentration and any eventual subsequent dosage can be determined reliably, accurately, rapidly, continuously and with few breakdowns.

Description

"Method for determining the concentration of an active substance containing a tracer in active substance solutions"

The invention relates to a method for determining the concentration of an active ingredient containing a tracer in aqueous or non-aqueous active ingredient solutions, in particular for cleaning or disinfecting containers such as bottles, kegs, boxes and tanks and / or pipelines in the food processing industry and be used for industrial cleaning in continuous washing systems, the concentration of the active ingredient in the solution being measured by determining its tracer content.

Such methods are preferably used in continuous cleaning systems in which the objects to be cleaned pass through cleaning solutions or disinfectant solutions, e.g. in bottle cleaning machines, container washing machines, cleaning systems for cleaning closed systems, such as pipes and tanks (ClP systems), and cleaning systems for metallic parts and textiles.

When using detergents and disinfectants in the commercial economy, it is desirable for ecological and economic reasons to overdose avoid, but underdosing leads to an insufficient cleaning result. A solution to this problem is made even more difficult if the objects to be cleaned continuously pass through cleaning and / or disinfecting baths, as is often the case in commercial cleaning, for example bottle, barrel, keg and container cleaning and commercial cleaning of metal parts or textiles is the case. With the cleaned or disinfected objects, cleaning agents or disinfectants are dragged out of the bath, so that the cleaning or disinfection bath is filled continuously or discontinuously with fresh water. The gradually decreasing concentration of detergent or disinfectant is measured and replenished if necessary.

In cleaning systems for closed systems (ClP systems) in which the cleaning and disinfection solution is used several times, dilution effects also occur, for example, due to mixed phases in the pre-rinsing and post-rinsing. In addition, when stacking used cleaning solutions, which are usually pushed out of the pipelines with fresh water, it is necessary to control up to what point in time or whether the returning solution is fed into the stacking container and from when the concentration of cleaning or disinfectant in the rinse water Collecting is no longer worthwhile and, above all, from what rinsing time the system can be refilled with food without fear of contamination with cleaning or disinfection chemicals. This process in CIP cleaning is referred to as "phase separation".

In these operating modes, the precise measurement of the cleaning agent and disinfectant concentration in the cleaning or disinfecting solution or in the rinse water is of paramount importance. For the reasons mentioned, the active substance concentrations in cleaning should be kept within narrow limits. For example, when cleaning refillable PET bottles (PET "polyethylene terephthalate), concentrations that are too high lead to stress corrosion cracking; if concentrations are too low, the bottles are also attacked and the cleaning result is insufficient. In the ClP process, the last step is often a disinfection step. In particular, contamination of foodstuffs with the frequently toxic disinfectants must be avoided and the rinsing process must therefore be monitored particularly carefully.

The previously known methods for determining the concentration have disadvantages. The conductivity measurement is carried out as an online measurement method. So that fluctuations in the conductance However, the safe implementation of this method requires a relatively high conductance of the active substance solution of at least 3 to 4 mS in the tap water, which only requires strongly alkaline, strongly acidic or high concentrations of others to result in measurement errors Solutions containing electrolytes is achieved. The lack of suitable online measurement methods for largely neutral or low-salt active ingredient solutions, such as, for example, disinfectants based on guaternary ammonium compounds or biguanides, makes their use for CIP cleaning in the food industry considerably more difficult. If the conductivity is used in bottle cleaning machines as a measure of the active ingredient concentration, the values obtained pretend that the active ingredient concentration is too high, since the conductivity of the alkali gradually increases due to the introduction of carbon dioxide and salts obtained, for example, from the dissolution of aluminum foil increases.

Another type of metering of active ingredient concentrates which is customary in practice is metering proportional to the bottle throughput. This method is based on the consideration that each bottle with the bottle cell carries a constant amount of cleaning solution out of the bath. Depending on the petrification of the bottle cells, the foam behavior of the solution and the control of the liquid flows between the different baths of industrial bottle cleaning machines changes this amount however. From operational practice it is known that when dosing according to the methods mentioned, the actual detergent concentration can deviate from the target concentration by 50% or more within a few days. If there are technical defects in the metering device, these can only be recognized and corrected after the complex manual concentration determination carried out at intervals of 1 to 5 days. In these cases, fluctuations in concentration occur in practice by a factor of up to about 40.

Other determination methods, with which the content of active substance is determined by chemical analysis, work more precisely than the conductivity measurement. However, these methods are time-consuming, can only be carried out manually and cannot continuously detect the concentration. In the case of iodine / iodide as active ingredients containing tracers, their concentration in the active ingredient solution can be determined by determining the iodine present in the solution. The wetting agent is removed from a sample of the active ingredient solution by means of activated carbon filtration. The iodine ions present in the solution are oxidized, and the existing protein is bound by adding copper sulfate. After extracting the iodine in chloroform or methylene chloride, the iodine content is determined photometrically. The active substance concentration can be determined from this via a calibration curve. - be shared. In addition to the disadvantages mentioned, this method is very time-consuming and has a high susceptibility to faults. Another disadvantage is the need to use chlorine-containing solvents.

The object of the invention is therefore to create a solution with which a determination of the active substance concentration and, if necessary, a subsequent dosing is possible reliably, precisely, quickly, with little susceptibility to faults and continuously.

This object is achieved according to the invention with a method of the type described at the outset in that a fluorescent dye is used as the tracer and the fluorescent dye concentration in the solution is measured optically and the concentration of the active ingredient is determined accordingly from the measured values obtained.

With this procedure, it is surprisingly possible to carry out a reliable, accurate and fast continuous determination of the active substance concentrations. In addition, the use of a fluorescence tracer has the great advantage over other tracer substances, such as, for example, potassium iodide, because of a greater chemical similarity, for example with regard to the molecular size, of the compounds which are active in cleaning and disinfection (surface-active) Substances) or the defoamers Behavior with regard to distribution, diffusion, absorption and thus drag-out. By using a fluorescent dye, the concentration can be determined by fluorescence spectrometry using an optical system, the concentration of the fluorescent dye correlating directly with the concentration of the active substances, and a dosage control to avoid overdosing and underdosing is thus possible.

It is preferably provided that the fluorescent dye concentration is measured with the aid of an inline fluorescence sensor system and that the fluorescent dye concentration in the solution is between 0.01 and 10,000 ppm, in particular between 0.1 and 2,500 ppm.

In a particularly advantageous embodiment of the invention, it is provided that the turbidity of the solution is determined simultaneously with the measurement of the fluorescent dye concentration, which is immediately possible.

In an advantageous embodiment of the invention it is provided that the fluorescence measurement is carried out with the aid of a fiber optic directly in the solution to be measured or with the aid of a part of the solution which is continuously removed in the side stream. When using fiber optics for fluorescence and turbidity measurement, it is preferably provided that the incident light contains only the wavelength of the excitation spectrum which is backscattered in the solution and by at least two filters in the proportion of the backscattered light with the excitation wavelength and the proportion of the light is divided with the emission wavelength, the portion of the backscattered light of the excitation wavelength being used for measuring the turbidity and the portion of the backscattered light of the emission wavelength being used for measuring the active substance concentration.

If the fluorescence measurement is carried out in a side stream, it is preferably provided that the incident light at the long-wave end of the spectrum contains at most the excitation wavelength of the fluorescent dye, that only the wavelength range from the light emitted at right angles from the solution is used. in which the emission wavelength represents the minimum or contains only the emission wavelength itself, and that the opacity of the solution is determined by transmitted light without or after filtering to exclude the wavelength above the excitation wavelength with the aid of intensity measurements.

In principle, substances with an excitation wavelength and emission wave ^" 3 -

length in the ultraviolet and visible wavelength range. Salicylic acid or its salts, in particular sodium salicylate, alkylbenzenesulfonates, e.g. Isopropylbenzenesulfonate, optical brighteners from the field of detergent production, fluorescein or sodium 3-oxypyrenetrisulfonic acid have been found to be advantageous.

It is advantageously provided that the concentration of the active substance is determined from the measured intensity by means of a calibration curve which has been determined by measured intensities of at least two different concentrations of the active substance in the solution to be monitored.

It is particularly advantageously provided that the active substance containing the fluorescent dye is metered or metered in aqueous or non-aqueous active substance solution, the metering or metering being controlled by a regulating device which verifies the actual concentration determined with a predetermined target concentration ¬ is the same.

In a further advantageous embodiment, it is provided that pre-rinse and rinse water in cleaning systems for closed systems (ClP system) are separated from the aqueous or non-aqueous active ingredient solutions in which the phase - J o -

Separation is controlled by a device which compares the determined concentration of the active ingredient with a predetermined target concentration and controls control devices, for example valves, for phase separation in accordance with the comparison result.

The method can be used advantageously for measuring the active substance concentration in the caustic baths and water zones of industrial bottle cleaning machines, for measuring the active substance concentration of cleaning or disinfectant solutions for closed systems (ClP systems) in the food industry or for measuring the active substance Use substance concentrations in industrial continuous washing plants, in particular for the cleaning of metal sheets or textiles, the objects to be cleaned, which run through, carry out a part of the active substance solution from the active substance baths.

The invention is explained below with reference to the drawing and two exemplary embodiments, for example. The drawing shows in

1 is a schematic diagram of a device for carrying out the method according to the invention, Fig. 2 shows another device for performing the method and in the

3 to 5 different representations of measurement results.

Example 1:

In the case of a direct, fiber-optic determination, which is shown in FIG. 1, light is radiated into a solution via an optical fiber bundle 3, the wavelength spectrum of which contains only the narrow section of the excitation wavelength of the dye. This is achieved in that the light from a light source 1, which contains the excitation wavelength of the fluorescent dye, reaches a filter 2, which only passes the excitation wavelength (bandpass).

The light is then guided to a measuring head 4 via the fiber optics 3. With a second fiber bundle, backscattered light is guided via a rapidly rotating filter wheel 5 onto a light-sensitive electronic component 6, for example a photodiode. The filter wheel contains on the one hand a filter which corresponds in wavelength to the excitation wavelength of the dye, and on the other hand contains a filter which has a wavelength in a spectral range the emission wavelength. The filters and the dye must be selected so that the wavelength ranges of the filters do not overlap and the absorption and emission wavelengths of the dye are sufficiently far apart.

The intensity received by the light-sensitive sensor from the wavelength range of the absorption spectrum corresponds to the backscattered portion of light in the solution and is a measure of the cloudiness and thus contamination of the cleaning or disinfecting solution. The intensity in the range of the emission wavelength, on the other hand, is a direct measure of the concentration of the fluorescent dye in the cleaning or disinfecting solution and correlates with the active substance content to be tracked. The arrangement with an optical fiber optic has, in addition to the above-mentioned basic advantages of using a fluorescence marker, the additional advantage that the measuring head 4 can be used at any point within closed pipe systems directly in the pipe within the liquid flow. - I -

Example 2:

If the sample is to be taken in the side stream, which is also possible at any point in the entire pipeline and container system, the structure shown in FIG. 2, which is mounted in a housing 14, can be used as an example. The cleaning or disinfection solution flows in from below through a flow-through cell 10 and flows out at the cuvette head, so that air and foam bubbles that have been introduced are in any case easily discharged from the inside of the cuvette with the liquid flow directed against gravity.

A light source 1 a, which emits a spectrum containing the excitation wavelength with sufficient intensity, is located in a light-tight housing 2 a, which contains a bushing for an electrical connection 3 a and a light outlet 4 a, which can be represented by a suitable lens. The propagating light cone or the light bundle parallelized by the lens passes through an optical filter 5a, which either passes only the wavelength range of the excitation (bandpass) or only a wavelength range that contains the excitation wavelength as the maximum wavelength (shortpass). - II -

The filtered light beam is converted into a parallel light beam by an optional aperture 6a, which is narrower in width than the cuvette. In the cuvette, light of the excitation wavelength is partially absorbed by the fluorescent dye present in the cleaning or disinfecting solution. For this purpose, the dye molecules emit light in all directions in accordance with the emission wavelength. Light is also deflected and scattered by turbidities present in the cleaning or disinfecting solution.

Through a diaphragm 7 arranged orthogonally to the direction of incidence, fluorescent light reaches a filter 8. This filter only allows light of the emission wavelength (bandpass) or a wavelength range in which the absorption wavelength represents the lower limit (longpass). This ensures that only fluorescent light is detected by the light-sensitive detector device 9 located behind the filter 8. Light emerging from the cuvette 10 in the direction of irradiation strikes a filter 12 through an aperture 11. This filter is optional and can be omitted with the advantage of the higher light intensity. If a filter is installed, a filter can be selected which transmits the excitation spectrum (bandpass) or in which the excitation wavelength corresponds to the upper limit of the transmission range (short pass). In a straight line you will notice the light-sensitive measuring device 13 light which has passed through the cuvette. Its intensity is determined by the cloudiness of the cleaning and disinfecting solution.

In the example (Figures 3 to 5), the dye pyranine is used. The excitation wavelength in the pH range above pH 7 is 450 nm, the emission wavelength is 520 nm. Filter 5a is a short pass with a cutoff wavelength of 450 nm, filter 8 is a long pass with a cutoff wavelength of 500 nm or a bandpass filter 520 nm and a specified spectral width of +/- 10 nm, the filter 12 and the lens 4a are omitted. The light source la is a halogen direct current lamp, the light-sensitive detectors 9, 13 are two structurally identical photodiodes which react in the spectral range from 250 to 1,100 nm to incident light with a proportional voltage signal.

The concentration of the dye can be less than 10,000 ppm (= 10 g / 1), with concentrations between 0 and 6 ppm being used in the example.

The light intensity is shown in the diode voltage. Test measurements relate to a typical cleaning bath and pure water as a solvent and a cleaning bath in which the dye solution is gradually diluted

Pure water was added to also change the turbidity.

3 and 4 show the measurement signal (diode voltage in volts) obtained perpendicular to the direction of irradiation with the diode 9 for the fluorescence component as a function of the concentration of the fluorescence tracer pyranine in ppm. The intensities are expected to be lower when using a bandpass filter, for example for a wavelength of 520 nm (FIG. 3) - about ten times as expected than when using a long pass filter, in the example for wavelengths above 500 nm (FIG. 4) in any case it can be seen that the different turbidity between water (marked by squares), the heavily cloudy cleaning bath (marked by circles) and the mixture of cleaning bath and the water added to the dilution (marked by triangles), which is varied in its turbidity, have no influence on the fluorescence Signal.

5 shows the measurement signal (diode voltage in volts) for the intensity of the transmitted light (transmitted light component) as a function of the concentration of the fluorescence tracer pyranine in ppm. The measured values for water are again marked with squares, those for strongly cloudy cleaning baths with circles and those for the cleaning bath diluted with water with triangles. The measurements clearly show the influence of turbidity on the transmitted light, which is measured with the diode 13. With increasing tracer content, the intensity decreases linearly in a straight line direction even with constant turbidity, because a growing proportion of the irradiated primary intensity is emitted in lateral directions. However, if the fluorescence intensity is known, the diode 9 can be used to convert the turbidity of the cleaning or disinfection solution without the fluorescent dye component (indicated in the diode voltage of the transmitted light signal) in a simple manner, as the surprisingly empirically found nutritional formula shows: - -

TRQ, L "TRθ, W ^• TRCF ^ / (TRQ, W - A ^• CF),

in which

TRQ ^: turbidity in the solution without fluorescent dye (in V),

TR _Q W ^: turbidity in pure water without fluorescent dye (in V),

TRcp £: turbidity in the solution with the concentration CF (in ppm) of the fluorescent dye (in V),

A: = 2.8 (empirical factor for the described arrangement),

CF: Concentration of the fluorescent dye (in ppm).

Of course, the invention is not limited to the exemplary embodiments shown. Further configurations of the device for carrying out the method according to the invention are possible without departing from the basic idea.

Claims

- 19 claims:

1. A method for determining the concentration of an active ingredient containing a tracer in aqueous or non-aqueous active ingredient solutions, in particular for cleaning or disinfecting containers such as bottles, kegs, boxes and tanks and / or pipelines in the food processing industry and for industrial purposes Cleaning can be used in continuous washing systems, the concentration of the active ingredient in the solution being measured by determining its tracer content, characterized in that a fluorescent dye is used as the tracer and the fluorescent dye concentration in the solution is measured optically and accordingly from the The measured values obtained determine the concentration of the active ingredient.

2. The method according to claim 1, characterized in that the fluorescent dye concentration is measured using an inline fluorescence sensor system.

3. The method according to claim 1 or 2, characterized in - 13 -

that the fluorescent dye concentration in the solution is between 0.01 and 10,000 ppm, in particular between 0.1 and 2500 ppm.

4. The method according to claim 1 or one of the following, characterized in that the turbidity of the solution is determined simultaneously with the measurement of the fluorescent dye concentration.

5. The method according to claim 1 or one of the following, characterized in that the fluorescence measurement with fiber optics takes place directly in the solution to be measured or with the aid of part of the solution which is continuously removed in the side stream.

6. The method according to claim 5, characterized in that the incident light contains only the wavelength of the excitation spectrum, which is backscattered in the solution and by at least two filters in the proportion of the backscattered light with the excitation wavelength and the proportion of light the emission wavelength is divided, the proportion of the backscattered light of the excitation wavelength for measuring the turbidity and for measuring the active - HO -

Concentration of substances the proportion of backscattered light of the emission wavelength is used.

7. The method according to one or more of claims 1 to 5, characterized in that the incident light at the long-wave end of the spectra maxi al contains the excitation wavelength of the fluorescent dye that from the light emitted at right angles from the solution solution only the wavelength range is used in which the emission wavelength is the minimum or only contains the emission wavelength itself, and that the opacity of the solution is determined by transmitted light without or after filtering to exclude the wavelength above the excitation wavelength with the aid of intensity measurements.

8. The method according to claim 1 or one of the following, characterized in that as fluorescent dyes salicylic acid or its salts, in particular sodium salicylate, alkylbenzenesulfonates, e.g. Isopropylbenzenesulfonate, optical brighteners from the field of detergent production, fluorescein or sodium 3-oxydyrenetrisulfonic acid can be used.

9. The method according to claim 1 or one of the following, characterized in that that the concentration of the active ingredient is determined from the measured intensity by means of a calibration curve which has been determined by measured intensities of at least two different concentrations of the active ingredient in the solution to be monitored.

10. The method according to claim 1 or one of the following, characterized in that the active substance containing the fluorescent dye is metered or replenished in aqueous or non-aqueous solution of active substance, the metering or replenishment being controlled by a control device which zätit the actual concentration determined compares a predetermined target concentration.

11. The method according to claim 1 or one of the following, characterized in that pre-rinse and rinse water in cleaning systems for closed systems (ClP systems) are separated from the aqueous or non-aqueous active ingredient solutions, in which the phase separation is controlled by a device which compares the determined concentration of the active ingredient with a predetermined target concentration and controls control devices, for example valves, for phase separation in accordance with the comparison result. - Z ≥ -

12. The method according to claim 1 or one of the following, characterized in that it is used for measuring the active substance concentration in lye baths and water zones of industrial bottle cleaning machines.

13. The method according to one or more of claims 1 to 11, characterized in that it is used for measuring the active substance concentration of cleaning or disinfectant solutions for closed systems (ClP systems) in the food industry.

14. The method according to one or more of claims 1 to 11, characterized in that it is used for measuring the active substance concentrations in industrial continuous washing plants, in particular for cleaning sheets or textiles, the continuous objects to be cleaned being one Drag out part of the drug solution from the drug baths.