Determination of Hexavalent Chromium in Dyes Using a NovaChrom Chromatographic Column

Hexavalent chromium possesses high toxicity, carcinogenicity, and bioaccumulative potential. If the content of hexavalent chromium in dyes exceeds the permissible limit, it will not only contaminate the production environment and endanger the health of operators during textile dyeing and processing, but also, through end products such as garments and household articles, come into contact with skin or enter the food chain, thereby posing health risks including skin ulcers, respiratory diseases, and even cancer. Meanwhile, excessive hexavalent chromium discharged with wastewater can damage aquatic and soil ecosystems, inhibit microbial activity, and affect the growth of flora and fauna. Therefore, strict determination and control of hexavalent chromium content in dyes are necessary measures for implementing environmental regulations, ensuring product quality, and safeguarding public health and ecological balance.

In this article, a NovaChrom anion chromatographic column (HS‑5A‑Cr, 4.0×250mm) and Wayeal high performance liquid chromatograph were used to determine hexavalent chromium in dyes according to GB/T 47088‑2026, providing a reference for your determination of hexavalent chromium in dyes by HPLC.

Keywords: Ion chromatography column; dyes; GB/T 47088-2026; hexavalent chromium; high performance liquid chromatography; HS-5A-Cr.

1. Experiment

1.1 Main Instruments and Reagents

Liquid chromatograph: Wayeal high performance liquid chromatograph, equipped with a UV detector;

Anion chromatographic column: HS‑5A‑Cr, 4.0×250mm;

Anion guard column: HS‑5AG, 4×30mm;

Hexavalent chromium standard solution (1000mg/L);

Dipotassium hydrogen phosphate;

Anhydrous ammonium sulfate;

Ammonia solution;

Methanol;

Phosphoric acid;

C18 cartridge (SPE): 5g, 20mL.

Phosphate buffer solution: Weigh 22.8g of dipotassium hydrogen phosphate (K₂HPO₄·3H₂O, relative molecular mass 228), dissolve in 1000mL of water, adjust the pH to 8.0±0.1 with phosphoric acid, and degas in an ultrasonic generator. The phosphate buffer solution should be prepared freshly before use, or stored under refrigeration at 0–4 °C for up to 7 days; before use, bring it to room temperature and degas again.

Disposable syringe (20mL);

1.2 Solution Preparation

1.2.1 Preparation of Intermediate Stock Solution

Pipette 1mL of the hexavalent chromium standard solution (1000mg/L) into a 100mL volumetric flask, dilute to the mark with phosphate buffer solution, and obtain a hexavalent chromium standard stock solution of 10mg/L.

Pipette 1mL of the hexavalent chromium standard stock solution (10mg/L) into a 10mL volumetric flask, dilute to the mark with phosphate buffer solution, and obtain a hexavalent chromium standard working solution of 1mg/L.

1.2.2 Preparation of Series of Standard Working Solutions

Pipette 0.2mL, 0.5mL, 1.0mL, 2.5mL, and 5mL of the hexavalent chromium standard intermediate solution (1mg/L) into a set of 25mL volumetric flasks, fix the volume with phosphate buffer solution, and mix well; this prepares a standard series of five different concentrations. The mass concentration table for the standard curve series is shown in Table 1 below.

Table 1 Concentration Gradient Series for the Calibration Curve

1.3 Instrument Operating Conditions

Column temperature: 30 °C;

Eluent: 0.25mol/L ammonium sulfate aqueous solution, adjusted to pH 8.0±0.2 with ammonia water;

Flow rate: 1mL/min;

Injection volume: 50μL;

Detection wavelength: 372nm.

1.4 Pretreatment

1.4.1 Extraction

Weigh 1.0g of the test sample (to the nearest 0.0001g) into a 100mL ground-glass stoppered conical flask, accurately add 50.0mL of phosphate buffer solution, and perform ultrasonic extraction in an ultrasonic bath for 20 min. Filter the extract through a syringe filter and set aside for later use. If the test sample is completely dissolved, the filtration step may be omitted.

1.4.2 Clean-up

Mount the C18 cartridge on the solid phase extraction manifold, and condition the cartridge sequentially with 20mL of methanol, 40mL of water, and 40mL of phosphate buffer solution. Accurately transfer 10.0mL of the extract onto the cartridge, elute with 30mL of phosphate buffer solution, collect all the eluate, transfer the eluate to a 50mL volumetric flask, and make up to volume with phosphate buffer solution.

2. Result and Discussion

2.1 Calibration Curve Test

Fig 1 Overlaid Chromatograms of the Calibration Curve Test

Table 2 Linearity of Hexavalent Chromium

2.2 Detection Limit Test – Test at a Hexavalent Chromium Concentration of 0.004mg/L

Fig 2 Chromatogram of Hexavalent Chromium at 0.004mg/L

Table 3 Test Data for the Theoretical Detection Limit

2.3 Sample and Spiked Sample Test

Fig 3 Chromatogram of the Dye Sample.

Note: After pretreatment and instrumental analysis in accordance with the standard requirements, none of the three samples were detected.

Fig 4 Chromatogram of the Spiked Sample at 2.5mg/kg.

Table 4 Test Data for the Spiked Sample at 2.5mg/kg

Fig 5 Overlaid Chromatograms of 7 Consecutive Injections of the Spiked Sample at 2.5mg/kg.

Table 5 Test Data for 7 Consecutive Injections of the Spiked Sample at 2.5mg/kg

3. Conclusion

Using the NovaChrom anion chromatographic column HS‑5A‑Cr (4×250mm) for the determination of hexavalent chromium in dyes according to GB/T 47088‑2026, the method exhibited excellent linearity and satisfactory detection limits. Recoveries for spiked samples at 2.5mg/kg ranged from 95.8 % to 96.8 %, which fully comply with the requirements of the standard.