JP2002340787A - Absorbance measurement device - Google Patents

Abstract

(57) [Summary] In a conventional liquid absorbance measuring device, the optical window of a flow cell gradually becomes dirty with the passage of time due to a substance contained in sample water, and accurate absorbance cannot be measured. There was a problem that it was necessary to clean the windows and it was troublesome. An object of the present invention is to provide a liquid absorbance measuring device which solves this problem. Kind Code: A1 A clean water flow system in which clean water flows only in the vicinity of a light projecting optical window and a light receiving optical window in a flow cell of an absorbance measuring device, for example, a pure water tank or a water filter and a pump. With the provision of the means, the absorbance can be measured stably for a long period of time without cleaning the optical window without cleaning.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an absorbance measuring device for analyzing the concentration of a substance dissolved or dispersed in a liquid.

[0002]

2. Description of the Related Art Generally, the absorbance of a sample water is an index of the concentration of a light absorbing substance contained in a specimen.
This is performed by placing sample water in an optical cell, irradiating a light beam, and measuring the amount of attenuation of transmitted light.If there is no turbidity between the concentration of the light absorbing substance and the absorbance, Beer's law holds.

Absorbance (OD) = − log I / log I ₀ = εCL where I ₀ : irradiation light intensity, I: transmitted light intensity, ε: absorption coefficient of substance, C: concentration of light absorbing substance, L: optical path length is there.
The extinction coefficient ε of a sample is generally unknown, but if a calibration curve is prepared for the concentration of the standard and the absorbance, then the absorbance of the sample is measured, and the absorbance of the sample is converted from the calibration curve to the concentration of the standard. And the concentration of the target sample can be calculated. Absorption coefficient ε
Since the wavelength varies depending on the wavelength of the projection beam, an advantageous wavelength is selected according to the absorption spectrum of the target substance.

When measuring the turbidity concentration of a sample water in which turbidity is dispersed in a solvent, it is assumed that the attenuation of transmitted light due to light scattering of the turbidity component obeys Lambert-Beer's law, The turbidity concentration can be quantified by the same calculation as the measurement. Transmitted light attenuation = −log I / log I ₀ = τTL where I ₀ : irradiation light intensity, I: transmitted light intensity, T: turbid concentration, L: optical path length, and τ: proportional constant.

[0005] Applicable devices for such absorbance measurement include a device for measuring the chromaticity and turbidity of tap water, an ultraviolet absorbance meter (UV meter) for measuring the amount of organic pollution, and a colorimeter for quantifying various chemical substances. and so on. For example, for a measuring device for the chromaticity of tap water and turbidity, the chromaticity is an index indicating the degree of coloring of tap water obtained from the measured absorbance at a wavelength of 390 nm, and the turbidity is determined from the measured absorbance at a wavelength of 660 nm. It is an index indicating the required degree of turbidity of tap water. Various devices for automatically measuring chromaticity and turbidity are already on the market, and the devices are basically a light emitting unit (light source), a flow cell, and a 39
Each optical filter transmitting 0 nm and 660 nm light,
A 390 nm and 660 nm light is sequentially transmitted through a flow cell comprising a light receiving unit (photoelectric converter) through which sample water flows continuously, and the absorbance is measured, and converted into chromaticity and turbidity from a conversion formula or conversion table. Output. For monitoring tap water, it is required to measure the chromaticity and turbidity of nearly transparent tap water for a long period of time without maintenance.In order to increase the measurement accuracy, an automatic zero point calibration function of the sensor is provided. There are many things. The calibration of the zero point can be performed, for example, by measuring clean water created by passing tap water through a water filter.

[0006]

In the conventional absorbance measurement technique, various substances contained in the sample water accumulate with time in the optical window of the flow cell, and when the optical window becomes dirty, the measured value is offset. In addition, there is a problem that accurate measurement of absorbance cannot be performed due to the influence of a narrow dynamic range. In such a case, maintenance is performed by cleaning the optical window. However, there is a problem in that considerable work is required, such as removing the optical window from the flow cell for cleaning.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a liquid absorbance measuring device that has a small amount of dirt on an optical window and is stable for a long period of time without performing cleaning maintenance. An object of the present invention is to provide a device capable of measuring absorbance.

[0008]

According to a first aspect of the present invention, there is provided an apparatus for measuring the absorbance of a sample water, comprising an optical window for projecting light and receiving light which is opposed to the sample water. A flow cell for water, a light emitting unit for irradiating the sample water with light from the optical window side of the flow cell, a light receiving unit for transmitting the sample water and receiving light emitted from the optical window for light reception of the flow cell, And a means for passing clean water through only the vicinity of the optical window for light projection and the optical window for light reception.

In the second device of the present invention, a pure water tank and a pure water tank are provided as a means for passing clean water in the first absorbance measuring device.
As a technical means, a liquid sending mechanism for sending pure water from the pure water tank to the vicinity of the light projecting optical window and the light receiving optical window in the flow cell is employed. In the third device of the present invention, as the clean water flowing means in the first absorbance measuring device, a water filter for removing turbidity components and soluble absorbance components of the sample water, and a filter water from the water filter are injected into the flow cell. The optical window for light and the liquid sending mechanism for sending the liquid to the vicinity of the optical window for light reception are employed as technical means.

The above-mentioned first to third means are provided with a clean water passage means for passing clean water only in the vicinity of the light transmitting optical window and the light receiving optical window in the flow cell. Water is always in contact with the optical window for
Since the sample water does not come into contact, various substances contained in the sample water do not deposit on the optical window of the flow cell. The clean water in contact with the optical window may be, for example, pure water as in the second means of the present invention, or a turbid component and soluble absorbance of the sample water through a water filter as in the third means of the present invention. Filter water from which components have been removed can be used, and since impurities are small, impurities do not deposit on the optical window. Therefore, the optical window can always be kept clean even when the measurement is performed for a long time, and the absorbance can be measured stably for a long time without performing maintenance for cleaning.

[0011] In a fourth apparatus of the present invention, in a sample water absorbance measuring apparatus, there is provided a flow cell having opposed light projecting and receiving optical windows for passing water through the sample water, and a flow cell from the light projecting optical window side of the flow cell. A light projecting unit that irradiates light to the sample water, a light receiving unit that transmits the sample water and receives light emitted from the light receiving optical window side of the flow cell, and a vicinity of the light projecting optical window and the light receiving optical window in the flow cell As technical means, a clean water flow means for passing clean water only through the flow path and a flow rate adjusting means for keeping the flow rates of the sample water and the clean water supplied to the flow cell constant are adopted.

In the fifth apparatus of the present invention, as the flow rate adjusting means in the fourth absorbance measuring apparatus, the supply of the sample water and the clean water which causes the sample water and the clean water to flow naturally to the flow cell so that the head difference is constant. Employ tanks as technical means. The fourth and fifth means are as follows.
Since the clean water flow means for flowing clean water is provided only in the vicinity of the light transmitting optical window and the light receiving optical window in the flow cell, the optical window can always be kept clean. At this time,
The optical path length of the light beam passing through the sample water is shorter by the optical path length of the light beam passing through the clean water, and when the flow ratio of the sample water and the clean water supplied to the flow cell changes, the light passing through the sample water changes. The optical path length of the beam changes, resulting in an error in the measured absorbance. However, the means of the present invention includes, for example, a sample supplied to the flow cell, such as a flow control valve or a pressure control valve, or a supply tank of sample water and clean water for allowing the head to flow naturally so that the head difference with respect to the flow cell becomes constant. Since the flow rate adjusting means for keeping the flow rates of the water and the clean water respectively constant are provided, the optical path length of the light beam passing through the sample water is always constant. Therefore, even when long-term measurement is performed, the optical path length of the sample water can be kept constant while the optical window is always kept clean, and the absorbance can be measured stably and with high precision for a long period of time without performing maintenance for cleaning. it can.

According to a sixth aspect of the present invention, in the sample water absorbance measuring device, there is provided a flow cell having opposed light projecting and light receiving optical windows for passing the sample water, and a flow cell from the light projecting optical window side of the flow cell. A light-emitting unit that irradiates light to the sample water, a light-receiving unit that receives light that has passed through the sample water and exits from the light-receiving optical window side of the flow cell, and only near the light-emitting optical window and light-receiving optical window in the flow cell Means for measuring the water pressure of the sample water based on the water pressure data measured by the water pressure measurement means for measuring the water pressure of the sample water and the clean water, respectively. The signal processing means for correction is adopted as technical means.

In the sixth means, first, a clean water flow means for flowing clean water is provided only in the vicinity of the optical window for light emission and the optical window for light reception in the flow cell. Can be kept clean. When the water pressure of the sample water and the clean water supplied to the flow cell changes due to the long-term measurement and the flow ratio changes, the optical path length of the light beam passing through the sample water changes, and an error occurs in the measured value of the absorbance. However, the means of the present invention is based on water pressure measurement means for measuring the water pressure of sample water and clean water, and on the basis of the water pressure data measured by the water pressure measurement means, calculates the change in the optical path length and measures the absorbance of the sample water. Is provided, the absorbance can be measured without being affected by the change in the optical path length of the sample water while the optical window is kept clean at all times, and stable and accurate absorbance measurement can be performed for a long period of time.

In the seventh apparatus of the present invention, the clean water flowing means for flowing the clean water only in the vicinity of the optical window for light projection and the optical window for light reception in the flow cell is arranged such that the inlet of the sample water is located at the center of the flow cell. The pure water inlet is located at two locations near the optical window for light emission and the optical window for light reception at both ends of the flow cell, and water is passed. Is disposed on the opposite side farthest from the entrance of the pure water in the vicinity of the optical window for light emission and the optical window for light reception, and sending the sample water and the pure water at a flow rate that maintains a laminar flow is employed as technical means.

The seventh means is that the pure water flows in the vicinity of the light emitting optical window and the light receiving optical window, and the pure water and the sample water are sent at a flow rate that maintains a laminar flow. The pure water only comes into contact with the optical window for light emission and the optical window for light reception, and the sample water does not come into contact with the optical window for light emission and the optical window for light reception.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As a first embodiment of the present invention, a pure water tank and a pure water tank for preventing a dirt on an optical window in a flow cell are provided. FIG. 1 shows an absorbance measuring device which is a liquid sending mechanism for sending the liquid to the vicinity of a light receiving optical window. The light from the LED light source 1 (light projecting unit) is selected in wavelength by the interference filter 2, passes through the light projecting optical window 3, passes through the flow cell 4, and passes through the light receiving window 5 with the amount of light transmitted through the photodiode 6. (Light receiving unit). The sample water 7 is passed by the pump 8 to the flow cell 4 from the position A in the figure. Also, pure water 9
The vicinity of the optical window for light projection (position B in the figure) and the vicinity of the optical window for light reception (position C in the figure) to the flow cell 4 by the clean water flow means 12 including the pure water tank 10 and the pump 11 (liquid sending mechanism). Water is passed from two places. Since the pure water and the sample water are each sent at a flow rate that maintains a laminar flow, they do not mix in the flow cell, and only the pure water comes into contact with the light projecting optical window 3 and the light receiving optical window 5, and the sample water comes into contact therewith. There is no. The value of the zero point can be obtained from the amount of transmitted light when the flow cell is filled with pure water alone. The transmitted light amount signal of the sample water and pure water photoelectrically converted by the photodiode 6 is sent to the signal processing unit 13. The absorbance is calculated. At this time, the optical path length of the sample water is a length obtained by subtracting the optical path length of pure water near the optical window from the cell length. In the absorbance measurement apparatus of this embodiment, since the sample water does not come into contact with the optical window, the optical window can always be kept clean even when the measurement is performed for a long time, and can be performed for a long time without performing the maintenance of the optical cleaning. Absorbance can be measured stably.

As a second embodiment of the present invention, FIG. 2 shows an absorbance measuring apparatus in which the clean water flow means is a liquid filter and a liquid sending mechanism for sending filter water to the vicinity of an optical window for light emission and light reception in a flow cell. Show. In this figure, the same components as those shown in FIG. 1 indicate the same components. The difference between the apparatus of the present embodiment and the apparatus of the first embodiment is that
A water filter 14 for removing the turbidity component and the soluble absorbance component of the sample water; and a pump 8 (a sample water feed pump and a sample water feeding pump) for sending the filter water from the water filter 14 to the vicinity of the optical window for light projection and the optical window for light reception in the flow cell. Since the sample water does not come into contact with the optical window similarly to the apparatus of the first embodiment, the optical window can always be kept clean even if measurement is performed for a long period of time. Absorbance can be measured stably for a long period of time without performing cleaning maintenance.

As a third embodiment of the present invention, FIG. 3 shows an absorbance measuring apparatus provided with a flow rate adjusting means for keeping the flow rates of sample water and clean water supplied to a flow cell constant. The same components as those shown in FIG. 1 indicate the same components. The apparatus according to the present embodiment includes, in addition to the configuration of the apparatus according to the first embodiment, a flow rate adjusting unit 15 that keeps the flow rates of the sample water 7 and the pure water 9 (clean water) supplied to the flow cell 4 constant. The flow control valve 16 is added to the liquid supply pipe, and the flow control valve 17 is added to the pure water liquid supply pipe. The optical path length of the light beam passing through the sample water is shorter by the optical path length of the light beam passing through the clean water, and when the flow ratio of the sample water and the clean water supplied to the flow cell changes, the light passing through the sample water changes. The optical path length of the beam changes, resulting in an error in the measured absorbance.
However, since the apparatus of the present embodiment is provided with the flow rate adjusting means for keeping the flow rates of the sample water and the clean water supplied to the flow cell constant, the optical path length of the light beam passing through the sample water is always constant. ing. Therefore, even when long-term measurement is performed, the optical path length of the sample water can be kept constant while the optical window is always kept clean, and the absorbance can be measured stably and with high precision for a long period of time without performing maintenance for cleaning. it can.

As a fourth embodiment of the present invention, FIG. 4 shows an absorbance measuring apparatus which is a supply tank for sample water and clean water in which the flow rate adjusting means flows naturally so that the head difference becomes constant. The same components as those shown in FIG. 3 indicate the same components. The apparatus of the present embodiment is different from the apparatus of the third embodiment in that the flow rate adjusting means 15 is used to allow the sample water 7 and the pure water 9 (clean water) to flow naturally to the flow cell 4 so that the head difference is constant. A sample water tank 18 for supplying sample water,
And a pure water tank 19 for supplying pure water, so that the optical path length of the sample water is kept constant while the optical window is kept clean even when performing long-term measurement, as in the apparatus of the third embodiment. , And the absorbance can be measured stably and with high accuracy for a long period of time without performing cleaning maintenance.

As a fifth embodiment of the present invention, an absorbance measuring device comprising a water pressure measuring means for measuring the water pressure of sample water and clean water and a signal processing means for correcting the measured absorbance value of the sample water based on the measured water pressure data. The device is shown in FIG. The same components as those shown in FIG. 1 indicate the same components. The apparatus of the present embodiment is similar to the apparatus of the first embodiment, except that a pressure measuring means 20 (comprising a pressure gauge 21 and a pressure gauge 22) for measuring the water pressure of the sample water 7 and the pure water 8 (clean water) is provided. The provision of the signal processing means 13 for calculating the change in the optical path length of the sample water based on the water pressure data measured by the measuring means 20 and correcting the absorbance measurement value of the sample water allows the optical window to be constantly cleaned. The absorbance can be measured without being affected by the change in the optical path length of the sample water while maintaining the above condition, and stable and highly accurate absorbance measurement can be performed for a long period of time.

[0022]

The absorbance measuring device of the present invention is designed to prevent contamination of an optical window, which is a problem of the conventional device, and to measure the absorbance stably for a long period of time. By providing clean water flow means for passing clean water only in the vicinity of the window and the optical window for receiving light, sample water is prevented from coming into contact with the optical window, and the optical window is always kept clean even after long-term measurement. Since it can be maintained, the absorbance can be measured stably for a long period of time without performing cleaning maintenance.

[Brief description of the drawings]

FIG. 1 shows a pure water tank and a liquid sending mechanism for sending pure water to a vicinity of an optical window for light emission and an optical window for light reception in a flow cell. Schematic diagram of a certain first invention example

FIG. 2 is a schematic view of a second invention example in which the clean water flow means is a liquid filter and a liquid feed mechanism for sending filter water to the vicinity of optical windows for light emission and light reception in a flow cell.

FIG. 3 is a schematic view of a third embodiment of the present invention including a flow rate adjusting means for keeping the flow rates of sample water and clean water supplied to the flow cell constant.

FIG. 4 is a schematic view of a fourth invention example in which the flow rate adjusting means is a supply tank for sample water and clean water which is allowed to flow naturally so that the head difference is constant.

FIG. 5 is a schematic view of a fifth embodiment of the present invention including a water pressure measuring means for measuring the water pressure of sample water and clean water and a signal processing means for correcting the measured absorbance of the sample water based on the measured water pressure data.

[Explanation of symbols]

 1: LED light source (light emitting part) 2: interference filter 3: light emitting optical window 4: flow cell 5: light receiving optical window 6: photodiode (light receiving part) 7: sample water 8: pump 9: pure water (clean) Water) 10: Pure water tank 11: Pump (liquid sending mechanism) 12: Clean water flow means 13: Signal processing means 14: Water filter 15: Flow control means 16, 17: Flow control valve 18: Sample water tank 19: Pure water tank 20: Pressure measuring means 21, 22: Pressure gauge

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Sanyo Ikutaka 1-1, Tanabe-Nitta, Kawasaki-ku, Kawasaki, Kanagawa Prefecture Inside Fuji Electric Co., Ltd. (72) Inventor Tokio Oto 1, Tanabe-Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture No. 1 Fuji Electric Co., Ltd. (72) Inventor Hiroshi Tada 1-1, Tanabe Nitta, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture F-term (reference) 2G057 AA01 AB01 AB03 AB06 AC01 BA05 DA15 GA01 JA02 2G059 AA01 BB04 BB06 BB09 CC19 EE01 FF04 GG02 HH02 HH03 HH06 JJ03 KK01 LL02 MM12 MM14 NN07

Claims (7)

[Claims] A flow cell having opposed optical windows for light emission and light reception and through which sample water flows, a light projecting unit for irradiating the sample water with light from the light emission optical window side of the flow cell; A light-receiving unit that receives light transmitted therethrough and emitted from the light-receiving optical window side of the flow cell; and a clean water flowing means that allows clean water to flow only in the vicinity of the light-emitting optical window and the light-receiving optical window in the flow cell. Absorbance measurement device provided. 2. The absorbance measuring apparatus according to claim 1, wherein the clean water flow means includes a pure water tank and pure water from the pure water tank in the vicinity of the light projecting optical window and the light receiving optical window in the flow cell. An absorbance measuring device consisting of a liquid sending mechanism. 3. The absorbance measuring apparatus according to claim 1, wherein the clean water flow means includes a water filter for removing a turbid component and a soluble absorbance component of the sample water, and a filter water from the water filter in the flow cell. An absorbance measuring device comprising an optical window for light and a liquid sending mechanism for sending the liquid near the optical window for light reception. 4. A flow cell having opposed optical windows for light emission and light reception and allowing water to flow through the sample water, a light projecting unit for irradiating the sample water with light from the optical window for light emission of the flow cell; A light-receiving unit that receives light that is transmitted and emitted from the light-receiving optical window side of the flow cell, and a clean water flowing unit that allows clean water to flow only in the vicinity of the light-emitting optical window and the light-receiving optical window in the flow cell. An absorbance measuring device comprising: flow rate adjusting means for keeping the flow rates of sample water and clean water supplied to the flow cell constant. 5. The absorbance measuring apparatus according to claim 4, wherein the flow rate adjusting means is a supply tank for the sample water and the clean water that allows the sample water and the clean water to flow naturally to the flow cell so that the head difference is constant. Absorbance measurement device. 6. A flow cell having opposed optical windows for light emission and light reception and allowing water to flow through the sample water, a light projecting unit for irradiating the sample water with light from the optical window for light emission of the flow cell; A light-receiving unit that receives light transmitted therethrough and emitted from the light-receiving optical window side of the flow cell; a clean water flow means that allows clean water to flow only in the vicinity of the light-emitting optical window and the light-receiving optical window in the flow cell; An absorbance measuring device comprising: a water pressure measuring means for measuring water pressures of water and clean water; and a signal processing means for correcting a measured absorbance value of a sample water based on water pressure data measured by the water pressure measuring means. 7. The absorbance measuring apparatus according to claim 1, wherein the clean water flow means for flowing clean water only in the vicinity of the light projecting optical window and the light receiving optical window in the flow cell. The inlet of the sample water is placed near the center of the flow cell to allow water to flow, and the inlets of pure water are placed at two positions near both ends of the flow cell, near the light emitting optical window and near the light receiving optical window. Then, the outlets of the sample water and the pure water are arranged near the optical window for light emission and the optical window for the light reception on the opposite side farthest from the inlet of the pure water, and each of the sample water and the pure water is sent at a flow velocity that maintains laminar flow. Absorbance measurement device.