JP5423662B2 - Water quality analyzer - Google Patents

Description

  The present invention relates to a water quality analyzer for quantifying organic pollutants contained in sample water such as sewage, river water, and factory effluent.

As a water quality analyzer that analyzes the quality of water such as sewage, river water, and factory effluent, a total organic carbon measuring device (TOC meter) that measures total organic carbon (TOC) contained in the sample and total nitrogen (TN) ) And a total nitrogen measuring device (TN meter) for measuring both TOC and TN. In these devices, the collected sample water is introduced into the combustion section, the TOC meter oxidizes and decomposes the carbon component in the sample into CO ₂ , and the TN meter oxidizes and decomposes the nitrogen component in the sample to NO. The gas containing them is introduced into the detection unit cell.

In the detection unit, the TOC meter measures the absorbance derived from the CO ₂ concentration in the gas led to the cell, and the TN meter measures the light emission amount derived from the NO concentration in the gas led to the cell. The TOC or TN in the sample water is quantified by obtaining the peak area value of the detection signal data obtained by these measurements. In order to quantify TOC or TN, a calibration curve indicating the relationship between the TOC or TN and the peak area value of the detection signal data is prepared in advance, and the calibration curve is calculated from the peak area value based on the measured detection signal data. TOC or TN is quantified based on (see Patent Document 1).

  In order to obtain the peak area value of the detection signal data, the rising or falling angle (peak detection angle) of the peak for determining the start point and the end point of the peak is set. The peak detection angle is set for each of the peak start point and end point, and when the rising angle of the detection signal curve reaches the set angle, the peak start point and the falling angle are set. When it descends, it is recognized as the peak end point. These peak detection angles are fixed to those suitable for the range of the output signal of the detection unit and the measurement conditions of the calibration curve used for measurement.

Japanese Patent Laid-Open No. 11-352058

  The combustion section of the TOC meter or TN meter is one in which a combustion tube for introducing a sample is accommodated in the heating furnace. There are a plurality of types of combustion tubes, and these combustion tubes have different capacities, and the combustion tubes used may differ depending on the type or concentration of the sample. When a large-capacity combustion tube is used, the peak of the detection signal obtained by the detector has a gentler shape than when a small-capacity combustion tube is used. Therefore, if peak detection when using a large-capacity combustion tube is performed at the same peak detection angle as in the case of a small-capacity combustion tube, detection of the peak start point may be delayed or a small peak may not be recognized. There was a problem.

  Therefore, an object of the present invention is to provide a water quality analyzer capable of detecting a peak of a detection signal at a peak detection angle corresponding to the capacity of a combustion pipe of a combustion section.

  The present invention comprises a combustion tube and a heating furnace for heating the combustion tube, an oxidation reaction part for oxidizing and decomposing a specific component in the sample water introduced into the combustion pipe, and a specification oxidized and decomposed in the oxidation reaction part A detector for measuring a gas containing a component with an optical detector, a peak detector for detecting a peak waveform start point and an end point based on a preset peak detection angle from a detection signal obtained by the detector, and detection A water quality analyzer having a calculation unit including a calculation unit that calculates a peak area and calculates a specific component concentration of a sample based on the area, and a detection angle candidate holding unit that holds a plurality of peak detection angle candidates And peak detection angle setting means for setting one peak detection angle from among the peak detection angle candidates held in the detection angle candidate holding unit, and the peak detection means In peak detection angle set by the time setting means it is characterized in that it is configured to detect the start and end points of the peak waveform.

  In the water quality analyzer of the present invention, a detection angle candidate holding unit that holds a plurality of peak detection angle candidates, and one of the peak detection angle candidates held in the detection angle candidate holding unit, according to the capacity of the combustion tube. A peak detection angle setting means for setting a peak detection angle, wherein the peak detection means detects a start point and an end point of the peak waveform at the peak detection angle set by the peak detection angle setting means. Therefore, when the combustion tube in the oxidation reaction section is replaced, the peak detection angle suitable for the replaced combustion tube can be set as a parameter, and the peak is set with a parameter corresponding to the capacity of the combustion tube. Detection can be performed.

It is a schematic block diagram which shows an example of a TOC / TN meter. It is a block diagram which shows the structure of the calculating part of the Example. It is an example of a peak waveform when TC measurement is performed, (A) is a case where a combustion tube having a small capacity is installed, and (B) and (C) are cases where a combustion tube having a larger capacity than (A) is installed. .

As an example of the water quality analyzer, a TOC / TN meter capable of measuring both TOC and TN will be described with reference to FIG.
A flow path for discharging a part of the sample to the drain outlet 12 through the branch part 3 in the TOC / TN meter main body is connected to the water sampling tube 1 through which a sample such as environmental water continuously flows. One port of the 8-port valve 14 of the sample injection mechanism 18 is connected to the branch unit 3 in order to guide the collected sample to the analysis unit.

The sample injection mechanism 18 includes an 8-port valve 14 and a microsyringe 16 connected thereto, and the microsyringe 16 is connected to a common port so that it can be connected to any port of the 8-port valve 14. Each port of the 8-port valve 14 has, in addition to the branching portion 3, an acid addition portion 20 added to make the sample acidic when measuring inorganic carbon (IC), a standard solution 22 for calibration, dilution, Dilution water 24 for use in cleaning, off-line sample 26, sample injection part 34 of oxidation reaction part 32 having a catalyst for converting all the carbon components in the sample into CO ₂ and converting the nitrogen component into NO, unnecessary A drain outlet 28 for discharging an unnecessary gas and a drain outlet 12 for discharging an unnecessary liquid are connected to each other.

  A gas purification / flow rate control unit 40 is provided to remove a carbon component from the air taken in from the air inlet 42 to generate a purified gas, and to send out the gas by adjusting the flow rate. At the gas outlet of the gas purification / flow rate control unit 40, the purified gas generated by the gas purification / flow rate control unit 40 is supplied to the microsyringe 16 as a sparge gas or carrier gas, and to the oxidation reaction unit 32 as a carrier gas. A flow path 41b to be supplied and a flow path 41c to supply purified gas to the ozone generator 50 are connected.

The oxidation reaction unit 32 converts a carbon component in a sample into CO ₂ and a combustion tube 36 filled with an oxidation catalyst that converts a nitrogen component into NO, and a sample injection unit that introduces the sample and a carrier gas into the combustion tube 36. 34 and a heating furnace 38 for heating the combustion tube 36.
The downstream side of the combustion pipe 36 is connected to an infrared gas analysis unit 46 that detects CO ₂ through a dehumidifier / gas processing unit 44 equipped with a dehumidifier for removing moisture and a halogen scrubber for removing halogen components. The infrared gas analyzer 46 is a non-dispersive infrared spectrometer (NDIR). Downstream of the infrared gas analyzer 46 is connected to a chemiluminescence analyzer 48 for detecting NO. Ozone is supplied from the ozone generator 50 to the chemiluminescence analyzer 48. A downstream portion of the chemiluminescence analysis unit 48 is connected to a drain outlet 54 via an ozone killer 52.

  The output of the infrared gas analysis unit 46 and the output of the chemiluminescence analysis unit 48 are input to the calculation unit 56. A keyboard 60 and a recorder 62 are connected to the calculation unit 56. The calculation unit 56 is connected to the control unit 58, and the control unit 58 controls the operations of the 8-port valve 14 and the microsyringe 16.

  The calculation unit 56 and the control unit 58 are realized by a CPU (Central Processing Unit) and a storage device. As shown in FIG. 2, the calculation unit 56 includes an information storage unit 2, a peak detection angle setting unit 4, a peak detection unit 6, and a calculation unit 8.

  A plurality of types (for example, two types) of combustion tubes are prepared as the combustion tubes 36 of the oxidation reaction section 32, and the respective combustion tubes have different capacities. The combustion tube 36 is exchanged by the analyst according to the type and concentration of the measurement sample. When the capacity of the combustion tube 36 installed in the oxidation reaction unit 32 is changed, the detection peak shape by the detectors of the infrared gas analysis unit 46 and the chemiluminescence analysis unit 48 is changed. Specifically, the peak shape of the detection signal obtained by the detector becomes smoother when a large capacity combustion tube is installed than when a small capacity combustion tube is installed. Therefore, a plurality of peak detection angle candidates corresponding to the types of combustion tubes that can be installed in the oxidation reaction unit 32 are prepared in the information storage unit 2, and are parameters at the time of peak detection by the peak detection angle setting unit 4. The peak detection angle can be selectively set. In addition, the information storage unit 2 also stores a calibration curve for converting the peak areas of detection signals obtained by the detectors of the infrared gas analysis unit 46 and the chemiluminescence analysis unit 48 into TC, TOC, and TN.

  The peak detection angle setting means 4 may be configured such that the analyst can change the peak detection angle used for measurement peak detection at an arbitrary timing, or automatically that the combustion tube has been changed. It may be configured to detect and notify or change the peak detection angle to the analyst. Further, when the combustion tube is replaced, the type of the combustion tube may be automatically recognized and automatically changed to a peak detection angle suitable for the combustion tube.

  FIG. 3 shows an example of the peak waveform of the detection signal. (A) is a peak waveform when a TC measurement is performed with a combustion tube having a small capacity, and (B) and (C) are the same sample measured by installing a combustion tube having a larger capacity than (A). It is a peak waveform when.

The measured value of TC is obtained based on the calibration curve from the area of the peak indicated by hatching. In order to obtain the peak area, the peak start point and end point must be determined. In this embodiment, peak detection angles (θ ₁ , θ ₂ ) (for example, θ ₁ = 300 μV / min, for installing and measuring a combustion tube having a small capacity (for example, 50 mL) shown in FIG. θ ₂ = 200 μV / min) and a peak detection angle (θ ′ ₁ , θ ′ ₂ ) (for example, θ) for installing and measuring a combustion tube having a large capacity (for example, 120 mL) shown in FIG. ' ₁ = 90 μV / min, θ ′ ₂ = 60 μV / min) are prepared in the information storage unit 2 as parameters. θ ₁ and θ ′ ₁ are peak start point detection angles, and θ ₂ and θ ′ ₂ are peak end point detection angles. The peak detection means 6 recognizes the peak start point when the rising angle of the detection signal obtained by the detector becomes θ ₁ or θ ′ ₁ , and recognizes it as the peak end point when the falling angle becomes θ ₂ or θ ′ _2. To detect the peak. The calculating means 8 calculates the area of the peak detected by the peak detecting means 6 and calculates TC using the calibration curve.

Here, when the measurement peak detection angle (θ ₁ , θ ₂ ) performed by installing a small capacity combustion tube is used for the measurement performed by installing a large capacity combustion tube, it is shown in FIG. As described above, the detection of the peak start point is delayed from the actual peak start point, and the peak end point is detected earlier than the actual peak end point. For this reason, there are portions that are truncated at both ends of the original peak waveform, which causes measurement errors. Therefore, when the combustion tube is changed to one having a larger capacity, the peak detection angle is also changed to (θ ′ ₁ , θ ′ ₂ ). Thereby, the detection of the peak start point can be accelerated and the detection of the peak end point can be delayed, so that the peak detection means 6 can recognize the points close to the actual peak start point and end point as the peak start point and end point. Become.

Table 1 shows that a combustion tube having a capacity of 120 mL is installed in the oxidation reaction section 32, a standard solution having a TC concentration of 0, 0.5, ₁ , ₂ , ₅ , ₁₀ mg / L is used, and a peak detection angle (θ ₁ , This shows data of the difference between the standard solution concentration and the measured concentration together with the peak area value and the measured concentration when TC measurement is performed using θ ₂ ) = (300 μV / min, θ ₂ = 200 μV / min). is there. Table 2 uses the same combustion tube and the same standard solution as Table 1, and performs TC measurement using peak detection angles (θ ′ ₁ , θ ′ ₂ ) = (90 μV / min, θ ′ ₂ = 60 μV / min). The data of the difference between the standard solution concentration and the measured concentration are shown together with the peak area value and the measured concentration.

  Comparing Table 1 and Table 2, the data in Table 1 shows a maximum error of 0.176 mg / L between the measured concentration and the standard solution concentration, whereas the data in Table 2 shows the measured concentration and the standard solution concentration. The error is only 0.054 mg / L at the maximum, indicating that the measurement accuracy is improved. In the data in Table 1, no peak was detected in the measurement of the standard solution at 0 mg / L. However, in actuality, the 0 mg / L standard solution contains a slight amount of carbon components. In the data in Table 2, the presence of such a small amount of carbon components is detected as a peak, and the peak detection accuracy is detected. It can be seen that is improved.

Returning to FIG. 1, operations of TC measurement, TN measurement, and TOC measurement in the embodiment will be described.
(TC measurement and TN measurement)
In response to a control signal from the control unit 58, the microsyringe 16 is connected to the branching unit 3 by the 8-port valve 14, and the microsyringe 16 is driven to sample a certain amount of sample into the microsyringe 16. When a predetermined dilution rate is set, the microsyringe 16 is connected to the dilution water 24 and a predetermined amount of dilution water is added to the sample in the microsyringe 16.

Next, the sample in the microsyringe 16 is injected into the combustion tube 36 through the sample inlet 34 of the oxidation reaction section 32, the carbon component in the sample is converted into CO ₂ , and the nitrogen component is converted into NO.
The CO ₂ and NO generated in the combustion pipe 36 are sent to the dehumidification / gas treatment unit 44 together with the supplied carrier gas from the gas purification / flow rate control unit 40 through the flow path 41b, and are cooled, dehumidified, and halogen-removed. Thereafter, CO ₂ is detected by the infrared gas analyzer 46, and subsequently NO is detected by the chemiluminescence analyzer 48. These detection signals are sent to the calculation unit 56, and the peak area value is obtained from the signal, and the TC concentration and the TN concentration are obtained based on the calibration curve.

(TOC measurement and TN measurement)
A certain amount of sample is collected in the microsyringe 16 in the same manner as in the TC measurement and the TN measurement. When a predetermined dilution rate is set, the microsyringe 16 is connected to the dilution water 24 and a predetermined amount of dilution water is added to the sample in the microsyringe 16.
Next, the microsyringe 16 is connected to the acid addition unit 20 and a small amount of acid is added to the sample in the microsyringe 16. Thereafter, the microsyringe 16 is connected to the drain outlet 28, and the purified gas is supplied to the microsyringe 16 through the flow path 41a from the gas purification / flow rate control unit 40, and the IC in the sample is removed.

Next, the sample in the microsyringe 16 is injected into the combustion tube 36 through the sample inlet 34 of the oxidation reaction section 32, the carbon component in the sample is converted into CO ₂ , and the nitrogen component is converted into NO.
The CO ₂ and NO generated in the combustion pipe 36 are sent to the dehumidification / gas treatment unit 44 together with the supplied carrier gas from the gas purification / flow rate control unit 40 through the flow path 41b, and are cooled, dehumidified, and halogen-removed. Thereafter, CO ₂ is detected by the infrared gas analyzer 46, and subsequently NO is detected by the chemiluminescence analyzer 48. These detection signals are sent to the calculation unit 56, and the peak area value is obtained from the signal, and the TOC concentration and the TN concentration are obtained based on the calibration curve.

(IC measurement, TOC measurement)
There is also a method for obtaining TOC by measuring IC and subtracting IC from TC obtained by the above method. In this method, a certain amount of sample is collected in the microsyringe 16 in the same manner as in the TC measurement and the TN measurement. When a predetermined dilution rate is set, the microsyringe 16 is connected to the dilution water 24 and a predetermined amount of dilution water is added to the sample in the microsyringe 16.

Next, the microsyringe 16 is connected to the acid addition unit 20 and a small amount of acid is added to the sample in the microsyringe 16. Thereafter, the microsyringe 16 is connected to the sample injection port 34, and the sparge gas is supplied from the gas purification / flow rate control unit 40 to the microsyringe 16 through the flow path 41 a. CO ₂ generated from the IC in the sample is sent to the dehumidification / gas treatment unit 44 through the combustion tube 36 together with the sparge gas, and after cooling, dehumidification and halogen removal, the infrared gas analysis unit 46 detects the CO ₂ . The detection signal is sent to the calculation unit 56, the peak area value is obtained from the signal, and the IC concentration is obtained based on the calibration curve.
In the calculation unit 56, the TOC concentration is also obtained from the difference between the TC concentration and the IC concentration.

2 Information storage unit 4 Peak detection angle setting means 6 Peak detection means 8 Calculation means

Claims (1)

An oxidation reaction section for oxidatively decomposing a specific component in the sample water introduced into the combustion tube, comprising a combustion tube and a heating furnace for heating the combustion tube;
A detector for measuring a gas containing a specific component oxidatively decomposed in the oxidation reaction unit with an optical detector;
Peak detection means for detecting the start point and end point of the peak waveform based on a preset peak detection angle from the detection signal obtained by the detection unit, and the area of the detected peak is obtained, and the specific component of the sample based on the area In a water quality analyzer equipped with a calculation unit having a calculation means for obtaining the concentration,
The oxidation reaction part can exchange the combustion pipe among a plurality of types having different capacities,
A detection angle candidate holding unit for holding a plurality of peak detection angle candidates;
Peak detection angle setting means for setting one peak detection angle according to the capacity of the combustion tube from among the peak detection angle candidates held in the detection angle candidate holding unit,
The water quality analyzer, wherein the peak detection means is configured to detect a start point and an end point of a peak waveform at a peak detection angle set by the peak detection angle setting means.

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