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2025

Determination of DPY dye intermediate content by potentiometric titration

1. Preface

DPY dye intermediates are an important component in the dye manufacturing process, including aromatic hydrocarbon derivatives used for the production of dyes and organic pigments. At present, the application of fuel intermediates has expanded to the pharmaceutical industry, pesticide industry, pyrotechnic and explosive industry, information recording materials industry, as well as the production sectors of additives, surfactants, fragrances, plastics, synthetic fibers, etc. In the dye manufacturing process, the selection, content and reaction conditions of dye intermediates determine the performance and application of the final dye.

In this paper, the determination method of the content of DPY dye intermediates was improved by potentiometric titration, and the results were accurate and reliable.

2 Instruments and reagents

2.1 Instruments

JH-T7 fully automatic potentiometric titrator, double platinum electrodes.

2.2 Reagents

Potassium bromide, 0.1 mol/L sodium nitrite standard titration solution, p-aminobenzenesulfonic acid, hydrochloric acid.

3 Experimental Methods

3.1 Experimental Procedures

Calibration of the standard titration solution: Accurately weigh 0.1g (accurate to 0.0001g) of anhydrous p-aminobenzenesulfonic acid into the titration cup and dissolve it in ammonia water. Add 30mL of ice water and 20mL of hydrochloric acid, and titrate with a standard sodium nitrite titration solution.

Sample testing: Accurately weigh 0.5g (accurate to 0.0001g) of the sample and transfer it to a 250mL beaker; Add 150 ml of distilled water and ice cubes, then add 10 ml of hydrochloric acid and 1g of potassium bromide, and stir at a uniform speed. Titrate with standard sodium nitrite solution.

3.2 Parameter Settings

Calibration parameter Settings for sodium nitrite:

Titration type: Permanent stop titration		Method name: Sodium nitrite calibration
Burette volume: 10mL		Sample measurement unit: g
Working electrode: Double platinum electrode		Reference electrode: None
Stirring speed: 6.		Stirring speed: 6.
Sensitivity: 0.01μA		Rapid drop volume: 0.2mL
Slow drop volume: 0.02mL.		End volume: 10mL
Terminal current: 100		Pre-control point: 80
nt: 100; Pre-control point: 80		Result unit: mol/L

Parameter Settings for titrating DPY dye intermediates with sodium nitrite:

Titration type: Permanent stop titration	Method name: Sodium nitrite titration DPY
Burette volume: 10mL		Burette volume: 10mL
Working electrode: Double platinum electrode		Reference electrode: None
Stirring speed: 7.		Pre-stirring time: 10 seconds
Sensitivity: 0.01μA		Rapid drop volume: 0.1mL
Slow drop volume: 0.02mL		End volume: 10mL
Terminal current: 30.		Pre-control point: 8
Delay time: 30		Correlation coefficient: 0.287
Titrant name: Sodium nitrite		Theoretical concentration: 0.0809

4 Results and Discussion

4.1 Experimental Results

After analysis and testing, the calibration results of sodium nitrite are as follows:

Sample Name	Sampling Quantity /g	Titration Sample volume V1/mL	Titrate the blank volumeV2/mL	c(NaNO2)/mol/L	c(NaNO2)/mol/L
P-aminobenzenesulfonic acid	0.1044	7.580	0.02	0.0795	0.0809
	0.0971	6.940		0.0808
	0.0983	6.880		0.0825

After analysis and testing, the determination results of DPY dye intermediates are as follows:

Sample Name	Sampling Quantity /g	c(NaNO2)/mol/L	Titration Sample volume V1/mL	Titrate the blank volume V2/mL	Content /%	Average value/%	RSD/%
DPY dye Material intermediate	0.50578	0.0809	7.140	0.02	32.68	32.14	1.68
	0.52028		7.100		31.60
	0.52281		7.260		32.15

4.2 Titration spectrum

Sodium nitrite calibration spectrum

Titration pattern of DPY dye intermediate

4.3 Conclusion

This paper establishes a potentiometric titration determination method for DPY dye intermediates, avoiding errors caused by color determination. The results are more accurate and reliable, providing a certain reference basis for the content determination of DPY dye intermediates.

Precautions

The dosage of hydrochloric acid affects the calibration of sodium nitrite. Reducing the dosage of hydrochloric acid leads to a sudden slowdown in the current, making it difficult to determine the endpoint. It is recommended to add hydrochloric acid dropwise according to the national standard dosage.

2. In several types of permanent stop titration, reversible pair titration cannot achieve pre-control during reversible pair titration, and the reaction endpoint cannot be accurately determined.

When titrating reversible electric pairs with irreversible electric pairs, abnormal spectra will occur, affecting the peak output. Therefore, only reversible pair titration of irreversible pair reactions can be carried out.

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