GB/T 6730.22-2016 in English

Standard Background and Technological Evolution

Standard Revision Background: GB/T 6730.22-2016 replaces the 1986 version of "Chemical Analysis Method of Iron Ores-Determination of Titanium Content by Diantipyrine Methane Spectrophotometry". The main updates include:

• Modify the standard name to clarify that the detection object is the titanium content in iron ore.
• Add "Warning", "Normative Reference Documents", "Test Report" and other clauses to improve the standardization and safety of the standard.
• Introduce the sodium carbonate-boric acid mixed flux melting pretreatment method to enrich the sample pretreatment methods.
• Through the joint precision test between laboratories, the repeatability limit r and reproducibility limit R obtained by statistics are used to replace the "allowable difference" to improve the scientificity and accuracy of the standard.

Detection principle and process

Detection principle:Based on diantipyrin methane (DAP) spectrophotometry, quantitative analysis is performed using the absorption characteristics of titanium ions at specific wavelengths. The specific steps are as follows:

1. Sample pretreatment:After the sample is acid decomposed and then alkali-melted with the residue or sodium carbonate-boric acid mixed flux, it is acid leached.
2. Color reaction:In 1.2~2.5 mol/L hydrochloric acid medium, ascorbic acid reduces iron, and titanium ions react with diantipyrine methane to form a yellow complex.
3. Absorbance measurement:Measure the absorbance at a wavelength of 385 nm, and calculate the titanium content in the sample through the standard curve.

Implementation suggestions

Laboratory precautions:

• Strictly follow the standard operating procedures for sample pretreatment and color reaction to ensure that the purity of the reagents and experimental conditions meet the requirements.
• Regularly calibrate the spectrophotometer and use standard solutions to draw calibration curves to ensure the accuracy and traceability of the test results.
• For samples containing interfering elements such as barium, niobium, and chromium, corresponding measures (such as using sulfuric acid to dissolve salts) need to be taken to eliminate interference.
• It is recommended to conduct blank tests and verification tests to ensure that the experimental process is correct and compare with standard samples.

Precision analysis

Repeatability and reproducibility: Eight laboratories conducted joint tests on five samples with different levels of titanium content, and the following precision data were obtained:

Result acceptance: The analysis value is compared with the standard value of the standard sample (CRM or RM). If the deviation is within the range of 0.7R, the result is considered consistent; otherwise, the experimental process needs to be rechecked.