LOW PRESSURE ANION EXCHANGE CHROMATOGRAPHY-TURBIDIMETRIC METHOD FOR SIMULTANEOUS ONLINE ANALYSIS OF TRACE SULFIDE AND CHLORIDE IN WATER SAMPLES

Abstract

The present invention provides a low pressure anion exchange chromatographyturbidimetric method for simultaneous online analysis of trace S.sup.2 and Cl.sup. in water samples using an apparatus comprising a low pressure pump, a sample valve, a sample loop, a low pressure anion chromatographic column, a reactor, an optical flow cell, an optical detector, a computer system, a mixer, a sample flow path, a propelling solution flow path, and a color developer solution flow path, the method comprising: (a) mapping a baseline; (b) mapping spectrogram of S.sup.2 and Cl.sup. in test samples; (c) mapping standard working curves; and (d) calculating the concentrations of S.sup.2 and Cl.sup. in the test samples based on the peak heights of S.sup.2 and Cl.sup. in the spectrogram and the regression equations of standard working curves. In this method, a chromatography method is combined with a turbidimetric method for the first time to realize simultaneous online analysis of trace S.sup.2 and Cl.sup. in water samples, and the method is endowed with the advantages of fast analysis speed, high analysis efficiency and low analysis costs.

Claims

1. A low pressure anion exchange chromatographyturbidimetric method for simultaneous online analysis of trace S.sup.2 and Cl.sup. in water samples using an apparatus comprising a low pressure pump (1), a sample valve (2), a sample loop (3), a low pressure anion chromatographic column (4), a reactor (5), an optical flow cell (6), an optical detector (7), a computer system (8), a mixer (9), a sample flow path, a propelling solution flow path, and a color developer solution flow path, the method comprising: (a) setting the apparatus in sample injection state, in which a blank sample (S.sub.0) is driven by the low pressure pump (1) to enter the sample loop (3) through the sample flow path and the sample valve (2); and then setting the apparatus in analytical state, in which a color developer solution (R) is driven by the low pressure pump (1) to enter the mixer (9) through the color developer solution flow path, a propelling solution (C) is driven by the low pressure pump (1) to enter the sample loop (3) through the propelling solution flow path and the sample valve (2), the propelling solution brings the blank sample (S.sub.0) in the sample loop (3) to enter the mixer (9) through the low pressure anion chromatographic column (4), they are mixed with the color developer solution in the mixer (9), then the mixture enters the optical flow cell (6) through the reactor (5), and signals produced via the optical detector (7) are transferred to the computer system (8) for processing to obtain a baseline; (b) setting the apparatus in sample injection state, in which a test sample (S.sub.1) is driven by the low pressure pump (1) to enter the sample loop (3) through the sample flow path and the sample valve (2); and then setting the apparatus in analytical state, in which the color developer solution (R) is driven by the low pressure pump (1) to enter the mixer (9) through the color developer solution flow path, the propelling solution (C) is driven by the low pressure pump (1) to enter the sample loop (3) through the propelling solution flow path and the sample valve (2), the propelling solution brings the test sample (S.sub.1) in the sample loop (3) to enter the low pressure anion chromatographic column (4), S.sup.2 and Cl.sup. in the test sample (S.sub.1), after being separated in the low pressure anion chromatographic column (4), is brought by the propelling solution to enter the mixer (9) successively, where they are mixed with the color developer solution (R) respectively to form a first mixed solution and a second mixed solution, which enter the reactor (5) successively and form a first reaction solution and a second reaction solution upon color development reactions, the first reaction solution and the second reaction solution enter the optical flow cell (6) successively, and signals produced via the optical detector (7) are transferred to the computer system (8) for processing to obtain spectrogram of S.sup.2 and Cl.sup. in the test sample (S.sub.1); (c) repeating steps (a) and (b) except for replacing the test sample (S.sub.1) with a series of standard samples (S.sub.2) in which the concentrations of S.sup.2 and Cl.sup. are known, to obtain spectrogram of S.sup.2 and Cl.sup. in the standard samples, and mapping standard working curves with the concentrations of S.sup.2 and Cl.sup. in the standard samples being abscissa and the peak heights of S.sup.2 and Cl.sup. in the spectrogram of S.sup.2 and Cl.sup. in the standard samples being ordinate; and (d) calculating the concentrations of S.sup.2 and Cl.sup. in the test sample (S.sub.1) by substituting the peak heights of S.sup.2 and Cl.sup. in the spectrogram of S.sup.2 and Cl.sup. in the test sample (S.sub.1) into the regression equations of the standard working curves obtained in step (c), respectively; wherein the test sample (S.sub.1) and the standard samples (S.sub.2) comprise NaOH in a concentration of from 10.sup.5 mmol/L to 10.sup.3 mmoL/L; the blank sample is an aqueous solution of NaOH in a concentration of from 10.sup.5 mmol/L to 10.sup.3 mmol/L; the propelling solution (C) is a mixed solution of nitric acid, sodium nitrate and deionized water; and the color developer solution (R) is a mixed solution of silver nitrate, polyvinylpyrrolidone K-30, gelatin, nitric acid and deionized water.

2. The method according to claim 1, wherein the propelling solution (C) comprises nitric acid in a concentration of 1-10 mmol/L, and sodium nitrate in a concentration of 1.0-10.0 g/L.

3. The method according to claim 1, wherein the color developer solution (R) comprises nitric acid in a concentration of 0.10-0.50 mol/L, silver nitrate in a concentration of 0.10-0.50 g/L, polyvinylpyrrolidone K-30 in a concentration of 0.10-0.50 g/L, and gelatin in a concentration of 0.50-1.0 g/L.

4. The method according to claim 2, wherein the color developer solution (R) comprises nitric acid in a concentration of 0.10-0.50 mol/L, silver nitrate in a concentration of 0.10-0.50 g/L, polyvinylpyrrolidone K-30 in a concentration of 0.10-0.50 g/L, and gelatin in a concentration of 0.50-1.0 g/L.

5. The method according to claim 1, wherein the detection wavelength of the optical detector is 420 nm.

6. The method according to claim 2, wherein the detection wavelength of the optical detector is 420 nm.

7. The method for simultaneous online analysis of trace S.sup.2 and Cl.sup. in water samples according to claim 3, wherein the detection wavelength of the optical detector is 420 nm.

8. The method according to claim 4, wherein the detection wavelength of the optical detector is 420 nm.

9. The method according to claim 1, wherein the test sample (S.sub.1) is filtrated by a microporous membrane and subjected to decolorization by macroporous adsorption resin before entering the low pressure pump (1).

10. The method according to claim 2, wherein the test sample (S.sub.1) is filtrated by a microporous membrane and subjected to decolorization by macroporous adsorption resin before entering the low pressure pump (1).

11. The method according to claim 3, wherein the test sample (S.sub.1) is filtrated by a microporous membrane and subjected to decolorization by macroporous adsorption resin before entering the low pressure pump (1).

12. The method according to claim 4, wherein the test sample (S.sub.1) is filtrated by a microporous membrane and subjected to decolorization by macroporous adsorption resin before entering the low pressure pump (1).

13. The method according to claim 5, wherein the test sample (S.sub.1) is filtrated by a microporous membrane and subjected to decolorization by macroporous adsorption resin before entering the low pressure pump (1).

14. The method according to claim 6, wherein the test sample (S.sub.1) is filtrated by a microporous membrane and subjected to decolorization by macroporous adsorption resin before entering the low pressure pump (1).

15. The method according to claim 7, wherein the test sample (S.sub.1) is filtrated by a microporous membrane and subjected to decolorization by macroporous adsorption resin before entering the low pressure pump (1).

16. The method according to claim 8, wherein the test sample (S.sub.1) is filtrated by a microporous membrane and subjected to decolorization by macroporous adsorption resin before entering the low pressure pump (1).

17. The method according to claim 1, wherein the column filler of the low pressure anion chromatographic column is strongly basic quaternary ammonium anion exchange resin.

18. The method according to claim 17, wherein the particle size of the column filler is 30-35 m.

19. The method according to claim 18, wherein the exchange capacity of the column filler is 3-4 mmol/g.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 is a schematic illustration of the process flow diagram of the present method in the sample injection state and of the structure of the corresponding apparatus.

[0025] FIG. 2 is a schematic illustration of the process flow diagram of the present method in the analytical state and of the structure of the corresponding apparatus.

[0026] The symbols in the drawings are as follows: 1low pressure pump, 2sample valve, 3sample loop, 4low pressure anion chromatographic column, 5reactor, 6optical flow cell, 7optical detector, 8computer system, 9mixer, Cpropelling solution, Rcolor developer solution, S.sub.0blank sample, S.sub.1test sample, S.sub.2standard sample, Wwaste fluid.

[0027] FIG. 3 is the spectrogram of S.sup.2 and Cl.sup. from the experiment in which a color developer solution free of dispersant and suspending agent is employed in Example 1.

[0028] FIG. 4 is the spectrogram of S.sup.2 and Cl.sup. from the experiment in which a color developer solution containing dispersant and suspending agent is employed in Example 1.

[0029] FIG. 5 is the spectrogram showing the precision in the assay of standard samples of S.sup.2 and Cl.sup. in Example 2.

[0030] FIG. 6 is a diagram illustrating the standard working curves of standard samples of S.sup.2 and Cl.sup. mapped in Example 3.

DETAILED DESCRIPTION OF THE INVENTION

[0031] The present invention will be further illustrated below by way of examples and with reference to the accompanying drawings. These examples are meant to be only illustrations of the present invention and do not limit it.

Example 1: Effect of the Composition of the Color Developer Solution on the Assay of S.SUP.2 and Cl.SUP. by the Turbidimetric Method

[0032] The effect of the composition of the color developer solution on the assay of S.sup.2 and Cl.sup. by the turbidimetric method was studied.

1. Preparation of Standard Samples of Cl.sup. and S.sup.2

[0033] Standard stock solution of chlorine ions (1000 mg/L): 0.1667 g of sodium chloride was weighed and transferred into a 100-mL volumetric flask, and the volume was brought up to the graduation mark with deionized water. The solution was evenly mixed by shaking, and for use, an appropriate volume was taken and diluted stepwise with deionized water to desired concentrations.

[0034] Standard stock solution of sulfur ions (1000 mg/L): A certain amount of crystalline sodium sulfide nonahydrate was taken and placed into a 50-mL small beaker or a Buchner funnel, rinsed with deionized water repeatedly to remove impurities on the surface. Then the moisture was absorbed immediately by clean filter paper, and 0.7506 g of the resulting crystal was rapidly weighed and dissolved in a small amount of deionized water. The solution was transferred into a 100-mL brown volumetric flask, and the volume was brought up to the graduation mark with deionized water. The solution was evenly mixed by shaking, and was placed in a refrigerator at 4 C. and protected from light. For use, an appropriate volume was taken and diluted stepwise with deionized water to desired concentrations.

[0035] Standard sample of sulfur ions in a concentration of 5 mg/L (pH 9-11): 0.5 mL of the standard stock solution of sulfur ions was transferred into a 100-mL volumetric flask. The pH value was adjusted to 9-11 using a standard sodium hydroxide solution, and the volume was brought up to the graduation mark with deionized water.

[0036] Standard sample of chlorine ions in a concentration of 50 mg/L (pH 9-11): 5 mL of the standard stock solution of chlorine ions was transferred into a 100-mL volumetric flask. The pH value was adjusted to 9-11 using a standard sodium hydroxide solution, and the volume was brought up to the graduation mark with deionized water.

2. Preparation of a Blank Sample

[0037] The pH value of deionized water was adjusted to 9-11 using a standard sodium hydroxide solution to obtain the blank sample.

3. Preparation of a Propelling Solution C

[0038] 1 g of sodium nitrate was dissolved in deionized water. 1 mL of a nitric acid solution (1 mol/L) was added, and then the volume was brought up to 1 L in a volumetric flask to obtain the propelling solution C.

4. Preparation of a Color Developer Solution R Free of Dispersant and Suspending Agent

[0039] 0.4 g of silver nitrate was weighed, and 400 mL of a nitric acid solution (1 mol/L) was added. The volume was brought up to 1 L with deionized water in a volumetric flask to obtain the color developer solution R free of dispersant and suspending agent.

5. Preparation of a Color Developer Solution R Containing Dispersant and Suspending Agent

[0040] 0.1 g of dispersant (polyvinylpyrrolidone K-30), 1 g of suspending agent (gelatin) and 0.4 g of silver nitrate were weighed, and 400 mL of a nitric acid solution (1 mol/L) was added. The volume was brought up to 1 L with deionized water in a volumetric flask to obtain the color developer solution R containing dispersant and suspending agent.

6. Experiment Conducted Using the Color Developer Solution R Free of Dispersant and Suspending Agent

[0041] The experiment was carried out using an apparatus as shown in FIGS. 1 and 2 except for the absence of the low pressure anion chromatographic column 4. In this apparatus, the low pressure pump 1 was a four-channel constant-flow peristaltic pump, with a pump capacity of 0.4-1.0 mL/min and a working pressure of 210.sup.5-310.sup.5 Pa; the sample valve 2 was a six-channel automatic sample valve, wherein the sample injection state of the six-channel automatic sample valve was adjusted using a time relay; the sample loop 3 was a polytetrafluoroethylene tube, the specific volume of which may be learned from calculation, wherein the inner diameter and length of the tube may be modified to adjust its volume; the reactor 5 was of a coil structure, and was made by winding polytetrafluoroethylene tubes having an inner diameter of 0.5 mm and a length of 3.0 m; the optical path of the optical flow cell 6 was 28 mm, and the detection wavelength of the optical detector 7 was adjusted to be 420 nm; the computer system 8 was a personal computer installed with an HW-2000 chromatographic workstation (Shanghai Qianpu Software Co., Ltd.); the optical flow cell of this apparatus was connected with a waste fluid container, and the sample was discharged into the waste fluid container after flowing through the optical flow cell.

[0042] (a) The apparatus was set in sample injection state. Driven by the low pressure pump 1, the blank sample S.sub.0 entered the sample loop 3 through the sample flow path and the sample valve 2 and filled the sample loop. The redundant sample was discharged into the waste fluid container in the form of waste fluid W. The color developer solution R free of dispersant and suspending agent entered the mixer 9 through the color developer solution flow path. The propelling solution C entered the mixer 9 through the propelling solution flow path and the sample valve 2 to be mixed with the color developer solution R free of dispersant and suspending agent and then entered the optical flow cell 6 through the reactor 5. Then the apparatus was switched to analytical state. Driven by the low pressure pump 1, the blank sample S.sub.0 was discharged into the waste fluid container in the form of waste fluid W after passing through the sample flow path and the sample valve 2. The color developer solution R free of dispersant and suspending agent entered the mixer 9 through the color developer solution flow path. The propelling solution C entered the sample loop 3 through the propelling solution flow path and the sample valve 2. The propelling solution brought the blank sample in the sample loop 3 to enter the mixer 9 where they were mixed with the color developer solution R free of dispersant and suspending agent. Then the mixture entered the optical flow cell 6 through the reactor 5. Signals produced via the optical detector 7 were transferred to the computer system 8 for processing to obtain a baseline.

[0043] (b) The apparatus was set in sample injection state. Driven by the low pressure pump 1, the standard sample of sulfur ions entered the sample loop 3 through the sample flow path and the sample valve 2 and filled the sample loop. The redundant standard sample of sulfur ions was discharged into the waste fluid container in the form of waste fluid W. The color developer solution R free of dispersant and suspending agent entered the mixer 9 through the color developer solution flow path. The propelling solution C entered the mixer 9 through the propelling solution flow path and the sample valve 2 to be mixed with the color developer solution R free of dispersant and suspending agent and then entered the optical flow cell 6 through the reactor 5. Then the apparatus was switched to analytical state. Driven by the low pressure pump 1, the standard sample of sulfur ions was discharged into the waste fluid container in the form of waste fluid W after passing through the sample flow path and the sample valve 2. The color developer solution R free of dispersant and suspending agent entered the mixer 9 through the color developer solution flow path. The propelling solution C entered the sample loop 3 through the propelling solution flow path and the sample valve 2. The propelling solution brought the standard sample of sulfur ions in the sample loop 3 to enter the mixer 9 where they were mixed with the color developer solution R free of dispersant and suspending agent. Then the mixture entered the optical flow cell 6. Signals produced via the optical detector 7 were transferred to the computer system 8 for processing to obtain a spectrogram of the standard sample of sulfur ions.

[0044] The above steps (a) and (b) were repeated for 5 times in total. Then steps (a) and (b) were repeated for 5 times with the standard sample of sulfur ions being replaced with the standard sample of chlorine ions. The spectrogram as shown in FIG. 3 was obtained.

7. Experiment Conducted Using the Color Developer Solution R Containing Dispersant and Suspending Agent

[0045] The experiment was carried out with the color developer solution R free of dispersant and suspending agent in step 6 being replaced with the color developer solution R containing dispersant and suspending agent. The spectrogram as shown in FIG. 4 was obtained.

[0046] As can be seen from the comparison between FIG. 3 and FIG. 4, the peak heights of S.sup.2 and Cl.sup. in the spectrogram decreased gradually and the reproducibility was quite poor when the color developer solution is free of dispersant (polyvinylpyrrolidone K-30) and suspending agent (gelatin), while the peak heights of S.sup.2 and Cl.sup. in the spectrogram were stable, the reproducibility was significantly improved, and the analysis precision was remarkably increased when the color developer solution contains dispersant (polyvinylpyrrolidone K-30) and suspending agent (gelatin). This is because the colloidal solution of silver chloride and silver sulfide formed when the dispersant polyvinylpyrrolidone K-30 and the suspending agent gelatin were added into the color developer solution had very good stability and dispersibility.

Example 2: Precision of the Present Method

[0047] Standard samples were tested in order to study the precision of the present method, and the steps are as follows:

1. Preparation of Standard Samples Containing Cl.sup. and S.sup.2

[0048] A standard stock solution of chlorine ions (1000 mg/L) and a standard stock solution of sulfur ions (1000 mg/L) were prepared according to step 1 of Example 1.

[0049] Mixed standard sample of sulfur ions in a concentration of 5 mg/L and chlorine ions in a concentration of 50 mg/L (pH 9-11): 5 mL of the standard stock solution of chlorine ions and 0.5 mL of the standard stock solution of sulfur ions were transferred into a 100-mL volumetric flask. The pH value was adjusted to 9-11 using a standard sodium hydroxide solution, and the volume was brought up to the graduation mark with deionized water.

2. Preparation of a Blank Sample

[0050] The blank sample was prepared according to step 2 of Example 1.

3. Preparation of a Propelling Solution C

[0051] 10 g of sodium nitrate was dissolved in deionized water. 10 mL of a nitric acid solution (1 mol/L) was added, and then the volume was brought up to 1 L in a volumetric flask to obtain the propelling solution C.

4. Preparation of a Color Developer Solution R

[0052] 0.1 g of polyvinylpyrrolidone K-30, 1 g of gelatin and 0.4 g of silver nitrate were weighed, and 400 mL of a nitric acid solution (1 mol/L) was added. The volume was brought up to 1 L with deionized water in a volumetric flask to obtain the color developer solution R.

5. Mapping of Spectrogram of Standard Samples

[0053] The experiment was carried out using the apparatus as shown in FIGS. 1 and 2. In this apparatus, the low pressure pump 1 was a four-channel constant-flow peristaltic pump, with a pump capacity of 0.4-1.0 mL/min and a working pressure of 210.sup.5-310.sup.5 Pa; the sample valve 2 was a six-channel automatic sample valve, wherein the sample injection state of the six-channel automatic sample valve was adjusted using a time relay; the sample loop 3 was a polytetrafluoroethylene tube, the specific volume of which may be learned from calculation, wherein the inner diameter and length of the tube may be modified to adjust its volume; the column filler of the low pressure anion chromatographic column 4 was strongly basic quaternary ammonium anion exchange resin, wherein the particle size of the column filler was 30-35 m, and the exchange capacity of the column filler was 3-4 mmol/g; the reactor 5 was of a coil structure, and was made by winding polytetrafluoroethylene tubes having an inner diameter of 0.5 mm and a length of 3.0 m: the optical path of the optical flow cell 6 was 28 mm, and the detection wavelength of the optical detector 7 was adjusted to be 420 nm; the computer system 8 was a personal computer installed with an HW-2000 chromatographic workstation (Shanghai Qianpu Software Co., Ltd.); the optical flow cell of this apparatus was connected with a waste fluid container, and the sample was discharged into the waste fluid container after flowing through the optical flow cell.

[0054] (a) The apparatus was set in sample injection state. Driven by the low pressure pump 1, the blank sample S.sub.0 entered the sample loop 3 through the sample flow path and the sample valve 2 and filled the sample loop. The redundant sample was discharged into the waste fluid container in the form of waste fluid W. The color developer solution R entered the mixer 9 through the color developer solution flow path. The propelling solution C entered the mixer 9 through the propelling solution flow path, the sample valve 2 and the low pressure anion chromatographic column 4 to be mixed with the color developer solution R and then entered the optical flow cell 6 through the reactor 5. Then the apparatus was switched to analytical state. Driven by the low pressure pump 1, the blank sample S.sub.0 was discharged into the waste fluid container in the form of waste fluid W after passing through the sample flow path and the sample valve 2. The color developer solution R entered the mixer 9 through the color developer solution flow path. The propelling solution C entered the sample loop 3 through the propelling solution flow path and the sample valve 2. The propelling solution brought the blank sample in the sample loop 3 to enter the mixer 9 through the low pressure anion chromatographic column 4. They were mixed with the color developer solution R in the mixer 9. Then the mixture entered the optical flow cell 6 through the reactor 5. Signals produced via the optical detector 7 were transferred to the computer system 8 for processing to obtain a baseline.

[0055] (b) The apparatus was set in sample injection state. Driven by the low pressure pump 1, the standard sample S.sub.2 entered the sample loop 3 through the sample flow path and the sample valve 2 and filled the sample loop. The redundant standard sample S.sub.2 was discharged into the waste fluid container in the form of waste fluid W. The color developer solution R entered the mixer 9 through the color developer solution flow path. The propelling solution C entered the mixer 9 through the propelling solution flow path, the sample valve 2 and the low pressure anion chromatographic column 4 to be mixed with the color developer solution R and then entered the optical flow cell 6 through the reactor 5. Then the apparatus was switched to analytical state. Driven by the low pressure pump 1, the standard sample S.sub.2 was discharged into the waste fluid container in the form of waste fluid W after passing through the sample flow path and the sample valve 2. The color developer solution R entered the mixer 9 through the color developer solution flow path. The propelling solution C entered the sample loop 3 through the propelling solution flow path and the sample valve 2. The propelling solution brought the standard sample S.sub.2 in the sample loop 3 to enter the low pressure anion chromatographic column 4. S.sup.2 and Cl.sup. in the standard sample S.sub.2, after being separated in the low pressure anion chromatographic column 4, is brought by the propelling solution to enter the mixer 9 successively, where they were mixed with the color developer solution R respectively to form a first mixed solution and a second mixed solution, which entered the reactor 5 successively and formed a first reaction solution and a second reaction solution upon color development reactions. The first reaction solution and the second reaction solution entered the optical flow cell 6 successively, and signals produced via the optical detector 7 were transferred to the computer system 8 for processing to obtain spectrogram of S.sup.2 and Cl.sup. in the standard sample S.sub.2.

[0056] The above steps (a) and (b) were repeated for 10 times in total. The spectrogram as shown in FIG. 5 was obtained. When a mixed standard sample of 5 mg/L of sulfides and 50 mg/L of chlorides was measured using the present method, the relative standard deviation of the peak heights of chlorine ions in the spectrogram was 2.30%, and the relative standard deviation of the peak heights of the sulfur ions in the spectrogram was 0.96%. This indicates that the method of the present invention has good precision.

Example 3: Mapping of a Standard Working Curve

[0057] Standard working curves were mapped, and the steps were as follows:

1. Preparation of a Standard Sample and a Blank Sample

[0058] (1) A standard stock solution of chlorine ions (1000 mg/L) was prepared according to step 1 of Example 1.

[0059] (2) A standard stock solution of sulfur ions (1000 mg/L) was prepared according to step 1 of Example 1.

[0060] (3) Preparation of standard sample series of chlorine ions: the standard stock solution of chlorine ions prepared in step (1) was diluted with deionized water, and the pH value was adjusted to 9-11 using sodium hydroxide, to prepare standard sample No. 1 to No. 9, in which the concentrations of chlorine ions were 0 mg/L, 5 mg/L, 10 mg/L, 25 mg/L, 50 mg/L, 75 mg/L, 100 mg/L, 125 mg/L and 150 mg/L, respectively, and the pH values of standard sample No. 1 to No. 9 were all 9-11.

[0061] (4) Preparation of standard sample series of sulfur ions: the standard stock solution of sulfur ions prepared in step (2) was diluted with deionized water, and the pH value was adjusted to 9-11 using sodium hydroxide, to prepare standard sample No. 10 to No. 18, in which the concentrations of sulfur ions were 0 mg/L, 0.2 mg/L, 0.5 mg/L, 1 mg/L, 5 mg/L, 7.5 mg/L, 10 mg/L, 12.5 mg/L and 15 mg/L, respectively, and the pH values of standard sample No. 10 to No. 18 were all 9-11.

[0062] (5) A blank sample was prepared according to step 2 of Example 1.

2. Preparation of a Propelling Solution C

[0063] The propelling solution C was prepared according to step 3 of Example 2.

3. Preparation of a Color Developer Solution R

[0064] The color developer solution R was prepared according to step 4 of Example 2.

4. Mapping of Spectrogram of Standard Samples

[0065] Steps (a) and (b) according to Step 5 of Example 2 were performed using each of standard sample No. 1 to No. 18 instead of the standard sample S.sub.2 in Example 2 to obtain spectrogram of S.sup.2 and Cl.sup. of each standard sample. The standard working curve of chlorine ions was mapped with the concentrations of chlorine ions (mg/L) in the standard samples being abscissa and the peak heights (mV) of chlorine ion in the spectrogram being ordinate, and the standard working curve of sulfur ions was mapped with the concentrations of sulfur ions (mg/L) in the standard samples being abscissa and the peak heights (mV) of sulfur ions in the spectrogram being ordinates. When the concentration of chlorine ions was within the linear range of 5-150 mg/L and the concentration of sulfur ions was within the linear range of 0.2-15 mg/L, the standard working curves were as shown in FIG. 6. The regression equation obtained from the standard working curve of chlorine ions was H=0.863C-1.613, R.sup.2=0.998; and the regression equation obtained from the standard working curve of sulfur ions was H=9.978C+1.292, R.sup.2=0.998 (wherein H is the peak height (mV); C is the concentration (mg/L) of substances to be assayed in the standard sample). Based on the baseline noise of the apparatus, a three-fold signal-noise ratio was taken as the quantitative detection limit, and the quantitative detection limits of the present method for Cl.sup. and S.sup.2 were calculated to be 3.47 mg/L and 0.04 mg/L, respectively.

Example 4: Analysis of Practical Environmental Water Samples

[0066] The method of the present invention was employed to analyze Cl.sup. and S.sup.2 in practical environmental water samples. The Methylene Blue National Standard Method (GB/T16489-1996) was employed to analyze sulfur ions in practical environmental water samples, and the ion chromatography conductivity method was employed to analyze chlorine ions in practical environmental water samples. Five practical environmental water samples, which were identified as test sample A, B, C, D and E respectively were assayed. The steps of analysis were as follows:

1. Preparation of a Propelling Solution C

[0067] The propelling solution C was prepared according to step 3 of Example 2.

2. Preparation of a Color Developer Solution R

[0068] The color developer solution R was prepared according to step 4 of Example 2.

3. Processing of Test Samples

[0069] Nitric acid or sodium hydroxide was added into test sample A, B, C, D and E that had been filtered by medium-speed filter paper, to adjust the pH value of each test sample to 9-11. After the pH value of each test sample was well adjusted, each test sample was filtered using an aqueous microporous membrane with a pore diameter of 0.45 m, and then decolorization was conducted using a macroporous absorption resin column.

4. Preparation of a Blank Sample

[0070] The blank sample was prepared according to step 2 of Example 1.

5. Mapping of Spectrogram of Test Samples

[0071] Steps (a) and (b) according to Step 5 of Example 2 were performed using each of test sample A, B, C, D and E that had been processed in step 3 instead of the standard sample S.sub.2 in Example 2 to obtain spectrogram of S.sup.2 and Cl.sup. of each of test sample A, B, C, D and E.

6. Assaying Results

[0072] The peak heights of S.sup.2 and Cl.sup. in the spectrogram of each test sample mapped in step 5 were substituted into the regression equations of the standard working curves of sulfur ions and chlorine ions obtained in Example 3 to calculate the concentrations of S.sup.2 and Cl.sup. in each test sample. The assaying results and the recovery rate of standard addition were shown in Tables 1 and 2.

TABLE-US-00001 TABLE 1 S.sup.2 Assay Measured Value/ (mg .Math. L.sup.1) Recovery rate/% Standard Methylene Methylene Addition/ Present Blue Present Blue No. (mg .Math. L.sup.1) Method Method Method Method A 0 0 0 5 4.51 0.1 4.16 90.2 83.2 10 9.44 0.2 9.88 94.4 98.8 B 0 0.530 0.05 0.500 5 5.76 0.07 5.25 105 95.0 10 10.8 0.6 10.3 103 97.7 C 0 2.13 0.2 2.02 5 6.77 0.3 6.89 92.8 97.4 10 11.6 0.4 11.3 94.3 93.2 D 0 0.220 0.1 0.250 5 4.86 0.3 5.13 92.8 97.6 10 9.28 0.1 9.91 90.6 96.6 E 0 0.820 0.1 0.890 5 5.33 0.9 5.01 90.2 82.3 10 9.83 0.7 10.6 90.1 96.8

TABLE-US-00002 TABLE 2 Cl.sup. Assay Measured Value/ (mg .Math. L.sup.1) Recovery rate/% Standard Ion Chroma- Ion Chroma- Addition/ Present tography Present tography No. (mg .Math. L.sup.1) Method Method Method Method A 0 15.6 0.86 15.9 50 67.8 1.3 65.7 104 99.6 100 121 0.72 114 106 98.1 B 0 46.8 0.76 47.5 50 103 1.1 95.4 112 95.7 100 152 1.2 146 105 98.9 C 0 4.04 0.57 4.17 50 49.5 0.86 47.5 90.8 96.7 100 97.3 0.95 98.3 93.3 94.3 D 0 8.55 0.41 8.60 50 53.1 0.72 48.8 89.0 80.5 100 109 1.3 101 100.9 92.0 E 0 18.8 0.49 19.4 50 62.9 1.0 60.3 88.2 81.7 100 110 1.5 110 91.5 90.6