CN111257252A - A kind of method for detecting oxysulfate in water with integrated photometric method of heating and separation - Google Patents

Abstract

The invention relates to a method for detecting oxysulfate in water by an integrated photometric method of heating and separation. The digestion tube was used as the only container for sample acidification, heating and separation. The outstanding features of this method are: the detection of water samples does not require complex processing, the determination process is simple, the amount of reagents used is small, and the analysis time is short, and it is especially suitable for rapid batch processing and analysis, with good reproducibility and high accuracy.

Description

A kind of method for detecting oxysulfate in water with integrated photometric method of heating and separation

technical field

The invention relates to a method for detecting oxysulfate in water by an integrated photometric method of heating and separation.

Background technique

The current methods for the determination of sulfate in water mainly include barium chromate spectrophotometry, ion chromatography, barium sulfate turbidimetry and gravimetric analysis. Although ion chromatography has high precision, it has high requirements for water samples, and the instrument is expensive. , need daily management and maintenance; the gravimetric analysis method is cumbersome and time-consuming; the turbidimetric method is greatly affected by the operating conditions, the working curve is not fixed, and the reproducibility of the results is poor; the barium chromate spectrophotometry (HJ/T342) uses the instrument The price is low, no routine maintenance is required, and the results are reproducible, but the operation of filtration and constant volume is complicated, and the detection limit is as high as 5mg/L. Due to the different determination principles, the determination methods of sulfite are different from sulfate ions, mainly iodometric method and pararosaniline hydrochloride spectrophotometry. Oxysulfate in water usually exists in the form of sulfate and sulfite (including SO ₃ ^2- , S ₂ O ₄ ^2- and S ₂ O ₆ ^2- , etc.), and there is no direct determination of the total amount of oxysulfate at present. method, if a fast, low detection limit, high accuracy and good reproducibility of barium chromate spectrophotometry for total sulfate radicals is established, combined with barium chromate spectrophotometry for sulfate radicals, the reducing properties can be rapidly obtained. The content of sulfite can greatly reduce the amount of reagents and pollution, and realize the rapid determination of sulfate and sulfite.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method for the detection of oxysulfate in water by a heat-separation integrated photometric method, which can increase the linear range of detection, shorten the test time, improve the sensitivity and accuracy of the spectrophotometry, and greatly increase the detection limit. reduce.

The scheme adopted by the present invention to solve the above-mentioned technical problems is:

A method for detecting oxysulfate in water by an integrated photometric method of heating and separation, comprising the following steps:

(1) Prepare a series of sulfate radical standard solutions of different concentrations in the digestion tube, add acid solution to the digestion tube in turn, shake well, then add barium chromate suspension and shake well, place it in a digestion apparatus for heating and cooling After adding ammonia solution, shake well, place the digestion tube in a centrifugal device to centrifuge to separate solid and liquid;

(2) absorb the supernatant obtained in step (1) and measure the absorbance in a spectrophotometer cuvette or colorimetric tube, then linearly regress the standard solution concentration C and the corresponding absorbance A to obtain a linear equation between A～C;

(3) According to the same processing conditions of step (1), absorb the supernatant liquid after processing the water sample to be tested and measure the absorbance A in a spectrophotometer cuvette or colorimetric tube, and calculate the corresponding content in the water sample according to the linear equation. Oxysulfate ion concentration.

Preferably, in step (1), the volume of the digestion tube is 10 mL, and the volume of the sulfate standard solution is less than or equal to 7 mL; the volumes of the acid solution and the ammonia water are both 0.1-0.3 mL, and the concentrations are both 1-8 mol/L; the volume of the barium chromate solution is 0.2-0.5mL, concentration ≤40g/L; heating temperature not lower than 100℃, time 5-10min; centrifugal speed ≥1800r/min, centrifugation time 3-5min.

Preferably, the acid solution in step (1) is hydrochloric acid. After adding hydrochloric acid and shaking, the digestion tube is placed in a digestion apparatus and heated for 5-10 min under the condition of ≥100°C, and then the barium chromate suspension is added. Continue the follow-up operation of step (1), and finally measure the sulfate ion content in the water.

Preferably, the acid solution in step (1) is nitric acid, and the total sulfate ion content in the water is finally measured.

Preferably, the total sulfate ions include sulfate and sulfite (including SO ₃ ^2- , S ₂ O ₄ ^2- and S ₂ O ₆ ^2- , etc.).

Preferably, the volume of the water sample added in step (3) is the same as the volume of the sulfate standard solution added in step (1).

Preferably, the sources of the water samples to be tested include: natural water bodies, circulating cooling water, industrial wastewater and desulfurization wastewater.

The invention adopts the digestion tube to conduct integrated heating and centrifugation of the system to be tested. The digestion tube itself is resistant to high temperature and has a small volume, which can reduce the amount of reagents. The use of trace reagents for detection not only does not reduce the linear range of detection, but increases the linear range. The synergy with the integrated heating technology not only simplifies and shortens the test time, making it suitable for batch determination of samples, but also improves the sensitivity of the method and The accuracy is greatly improved, the detection limit is greatly reduced, and the application is more accurate and convenient. The method of the present application can be used for the integrated detection of total sulfate in water by oxidation, heating and separation of nitric acid, the integrated detection of sulfate in water by acidification, heating and separation of hydrochloric acid, and the calculation of sulfite content by subtraction.

Description of drawings

Fig. 1 is the comparison of the working curve obtained in Example 1 of the present invention and the working curve obtained by HJ/T342-2007.

Detailed ways

For better understanding of the present invention, the following examples are further descriptions of the present invention, but the content of the present invention is not limited to the following examples.

Determination of sulfate ion content

Example 1

1) Prepare 7mL of sulfate radical standard solutions of different concentrations in a 10mL digestion tube;

2) Add 0.1 mL of hydrochloric acid solution to the standard solution and shake it up, place the digestion tube in the digestion apparatus and heat it at 120°C for 5 minutes;

3) Take out a little cooling and add 0.3 mL of barium chromate suspension, shake well, place it in a digestion apparatus, heat it at 110°C for 5 minutes with a lid, and then cool to room temperature;

4) Add 0.2 mL of ammonia solution, shake well, place in a centrifuge and centrifuge for 3 minutes at 1800 r/min;

5) draw the supernatant liquid obtained by centrifugation and measure the absorbance A at the wavelength of 420 nm in the spectrophotometer colorimetric tube;

6) Linearly regress the standard solution concentration C and the corresponding absorbance A to obtain a linear equation between A and C.

7) Add 7 mL of natural river water to the 10 mL digestion tube, add 0.1 mL of HCl solution, shake well, and place in the digestion apparatus at 120°C for constant temperature heating for 5 minutes. Take out a little cooling, add 0.3 mL of barium chromate suspension, shake well, and place it in the digestion apparatus at 110 °C for constant temperature heating for 5 min. When cooled to room temperature, add 0.2 mL of ammonia solution, shake well, and place it in a centrifuge at 1800 r for 3 min. Absorb the supernatant in a colorimetric tube to measure the absorbance at 420 nm. Using a linear regression equation, the sulfate concentration in the water sample is calculated to be 55.1 mg/L, the recovery rate was 99.1%.

With the same sulfate radical standard solution as Example 1, adopt the method in HJ/T342-2007 to linearly regress the A～C linear equation, and compare the working curve obtained by it with the working curve obtained in Example 1 of the present application, and the results are as follows: As shown in Figure 1, comparing the slope (sensitivity) and the correlation coefficient of the working curve, it can be seen that the correlation coefficient of one experiment of this method is 0.9999... (4 to 5 9s).

Example 2

1) Prepare 7mL of sulfate radical standard solutions of different concentrations in a 10mL digestion tube;

2) Add 0.2 mL of hydrochloric acid solution to the standard solution, shake well, place the digestion tube in the digestion apparatus and heat at 120°C for 5 minutes;

3) Take out the slightly cooled barium chromate suspension and add 0.3 mL, shake well, place it in a digestion apparatus, heat it at 120°C for 5 minutes with a lid, and then cool to room temperature;

4) Add 0.2 mL of ammonia solution, shake well, place in a centrifuge and centrifuge for 3 minutes at 1800 r/min;

5) draw the supernatant liquid obtained by centrifugation and measure the absorbance A at the wavelength of 420 nm in the spectrophotometer colorimetric tube;

6) Linearly regress the standard solution concentration C and the corresponding absorbance A to obtain a linear equation between A and C.

7) Add 20 μL of desulfurization wastewater to a 10 mL digestion tube, add demineralized water to 7 mL, add 0.2 mL of HCl solution, shake well, and place in a digestion apparatus at 120°C for constant temperature heating for 10 minutes. Take out the slightly cooled solution, add 0.3 mL of barium chromate suspension, shake well, and place it in the digestion apparatus at 120°C for constant temperature heating for 5 minutes. When cooled to room temperature, add 0.2 mL of ammonia solution, shake well, and then place it in a centrifuge at 1800 r/min for 3 min, absorb the supernatant in a colorimetric tube to measure the absorbance at 420 nm, and use a linear regression equation to calculate the sulfate concentration in the water sample as 23.65g/L, the recovery rate is 101.1%.

Example 3

1) Prepare 7mL of sulfate radical standard solutions of different concentrations in a 10mL digestion tube;

2) Add 0.2 mL of hydrochloric acid solution to the standard solution, shake well, place the digestion tube in the digestion apparatus and heat at 120°C for 10 minutes;

3) Take out a little cooling and add 0.3 mL of barium chromate suspension, shake well, place it in a digestion apparatus, heat it at 110°C for 5 minutes with a lid, and then cool to room temperature;

4) Add 0.2 mL of ammonia solution, shake well, place in a centrifuge and centrifuge for 3 minutes at 1800 r/min;

5) draw the supernatant liquid obtained by centrifugation and measure the absorbance A at the wavelength of 420 nm in the spectrophotometer colorimetric tube;

6) Linearly regress the standard solution concentration C and the corresponding absorbance A to obtain a linear equation between A and C.

7) Add 1 mL of circulating cooling water to a 10 mL colorimetric tube, add demineralized water to 7 mL, add 0.2 mL of HCl solution, shake well, and place in a digestion apparatus at 120°C for constant temperature heating for 10 minutes. Take out the slightly cooled solution, add 0.3 mL of barium chromate suspension, shake well, and place it in the digestion apparatus at 110 °C for 5 min with a lid and constant temperature. When cooled to room temperature, add 0.2 mL of ammonia solution, shake well, and then place it in a centrifuge at 1800 r/min for 3 min, absorb the supernatant in a colorimetric tube to measure the absorbance at 420 nm, and use a linear regression equation to calculate the sulfate concentration in the water sample as 243.2 mg/L, the recovery rate was 101.8%.

Determination of total sulfate ion content

Example 4

1) Prepare 7mL of sulfate radical standard solutions of different concentrations in a 10mL digestion tube;

2) Add 0.1 mL of nitric acid solution to the standard solution and shake up, then add 0.3 mL of barium chromate suspension and shake up;

3) Place the digestion tube in the digestion apparatus, heat it at 110°C for 5 minutes, cool it to room temperature, add 0.2 mL of ammonia solution and shake it up;

4) The digestion tube is placed in a centrifuge and centrifuged for 3 minutes at a rotational speed of 1800 r/min;

5) Draw the supernatant and measure the absorbance A at the wavelength of 420 nm in the colorimetric tube of the spectrophotometer;

6) Linearly regress the standard solution concentration C and the corresponding absorbance A to obtain a linear equation between A and C.

7) Add 7 mL of natural river water to a 10 mL digestion tube, add 0.1 mL of HNO ₃ solution and shake well, add 0.3 mL of barium chromate suspension, shake well, and place it in the digestion apparatus at 110 °C for 5 min with a lid and a constant temperature. When cooled to room temperature, add 0.2 mL of ammonia solution, shake it up, and place it in a centrifuge at 1800 r/min for 3 min. Absorb the supernatant in a colorimetric tube to measure the absorbance at 420 nm. The linear regression equation is used to calculate the total sulfate concentration in the water sample as 75.2mg/L, the recovery rate was 99.3%.

Example 5

1) Prepare 7mL of sulfate radical standard solutions of different concentrations in a 10mL digestion tube;

2) Add 0.2 mL of nitric acid solution to the standard solution and shake up, then add 0.4 mL of barium chromate suspension and shake up;

3) Place the digestion tube in the digestion apparatus, heat it at 120°C for 10 min, cool it to room temperature, add 0.2 mL of ammonia solution and shake it up;

4) The digestion tube is placed in a centrifuge and centrifuged for 3 minutes at a rotational speed of 1800 r/min;

5) Draw the supernatant and measure the absorbance A at the wavelength of 420 nm in the colorimetric tube of the spectrophotometer;

6) Linearly regress the standard solution concentration C and the corresponding absorbance A to obtain a linear equation between A and C.

7) Add 20 μL of desulfurization wastewater to a 10 mL digestion tube, add desalinated water to 7 mL, add 0.2 mL of HNO ₃ solution and shake well, add 0.4 mL of barium chromate suspension, shake well, and place it in the digestion apparatus at 120°C with a lid Heating at constant temperature for 10min. When cooled to room temperature, add 0.2 mL of ammonia solution, shake well, and place it in a centrifuge at 1800 r for 3 min. Absorb the supernatant in a colorimetric tube to measure the absorbance at 420 nm. The linear regression equation is used to calculate the total sulfate concentration in the water sample to be 42.34 g. /L, the recovery rate was 102.5%.

Example 6

1) Prepare 7mL of sulfate radical standard solutions of different concentrations in a 10mL digestion tube;

2) Add 0.2 mL of nitric acid solution to the standard solution and shake up, then add 0.3 mL of barium chromate suspension and shake up;

3) Place the digestion tube in the digestion apparatus, heat it at 120°C for 10 min, cool it to room temperature, add 0.2 mL of ammonia solution and shake it up;

4) The digestion tube is placed in a centrifuge and centrifuged for 3 minutes at a rotational speed of 1800 r/mn;

5) Draw the supernatant and measure the absorbance A at the wavelength of 420 nm in the colorimetric tube of the spectrophotometer;

6) Linearly regress the standard solution concentration C and the corresponding absorbance A to obtain a linear equation between A and C.

7) Add 1 mL of circulating cooling water to the 10 mL digestion tube, add demineralized water to 7 mL, add 0.2 mL of HNO ₃ solution and shake well, add 0.3 mL of barium chromate suspension, shake well, and place it in the digestion apparatus at 120°C and cover The lid was heated at a constant temperature for 10 min. When cooled to room temperature, add 0.2 mL of ammonia solution, shake it up, and place it in a centrifuge at 1800 r/min for 3 min. Absorb the supernatant in a colorimetric tube to measure the absorbance at 420 nm. The linear regression equation is used to calculate the total sulfate concentration in the water sample as 276.8 mg/L, the recovery rate was 100.7%.

The above descriptions are only the preferred embodiments of the present invention, of course, it cannot limit the scope of rights of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, Several improvements and changes are made, and these improvements and changes are also regarded as the protection scope of the present invention.

Claims (6)

1. a method for the detection of oxysulfate in water by heating separation integration photometry, is characterized in that, comprises the steps: (1) Prepare a series of sulfate radical standard solutions of different concentrations in the digestion tube, add acid solution to the digestion tube in turn, shake well, then add barium chromate suspension and shake well, place it in a digestion apparatus for heating and cooling After adding ammonia solution, shake well, place the digestion tube in a centrifugal device to centrifuge to separate solid and liquid; (2) absorb the supernatant obtained in step (1) and measure the absorbance in a spectrophotometer cuvette or colorimetric tube, then linearly regress the standard solution concentration C and the corresponding absorbance A to obtain a linear equation between A～C; (3) According to the same processing conditions of step (1), absorb the supernatant liquid after processing the water sample to be tested and measure the absorbance A in a spectrophotometer cuvette or colorimetric tube, and calculate the corresponding content in the water sample according to the linear equation. Oxysulfate ion concentration. 2. method according to claim 1, is characterized in that, in step (1), the volume of digestion tube is 10mL, and sulfate radical standard solution volume≤7mL; Acid solution and ammoniacal volume are 0.1-0.3mL, and concentration is 0.1-0.3mL. It is 1-8mol/L; the volume of barium chromate solution is 0.2-0.5mL, the concentration is ≤40g/L; the heating temperature is not lower than 100℃, the time is 5-10min; the centrifugal speed is ≥1800r/min, and the centrifugal time is 3-5min. 3. method according to claim 1, is characterized in that, the acid solution described in step (1) is hydrochloric acid, after adding hydrochloric acid and shaking up, described digestion tube is placed in digestion apparatus and heated under the condition of ≥ 100 ℃ for 5 After -10min, the barium chromate suspension was added to continue the follow-up operation, and the sulfate ion content was finally measured. 4. method according to claim 1, is characterized in that, the acid solution described in step (1) is nitric acid, and finally measures total sulfate ion content. 5. The method of claim 4, wherein the total sulfate ions comprise sulfate and sulfite. 6 . The method according to claim 1 , wherein the sources of the water samples to be tested include: natural water bodies, circulating cooling water, industrial wastewater and desulfurization wastewater. 7 .

Images