I. Introduction

Iron is a critical trace element in glass materials. Its concentration and valence state directly affect the optical properties, color characteristics, and product quality of glass. In the soda-lime-silica glass system, the iron content directly determines the appearance quality of the product: ordinary soda-lime glass exhibits a characteristic green tint due to its relatively high iron content (0.05%–0.3%), whereas ultra-clear glass required for applications such as photovoltaics and displays must meet national standards and industry specifications that strictly limit Fe₂O₃ content to no more than 0.015%. Therefore, accurate and rapid determination of iron content in glass has become a critical step in raw material screening, process control, and product grading.

II. Application of TXRF in the Detection of Fe Content in Glass

Traditional methods for determining Fe content in glass include Atomic Absorption Spectrometry (AAS) and Inductively Coupled Plasma Optical Emission Spectrometry(ICP-OES). However, these methods usually require complex sample preparation, involve long analysis cycles, and incur high costs. Total Reflection X-ray Fluorescence Spectrometry (TXRF), as an emerging trace element analysis technique, offers advantages such as minimal sample consumption, simple sample preparation, simultaneous multi-element analysis, and low detection limits.

For Fe element detection in glass, TXRF technology offers the following core advantages:

→Simple sample preparation: No high-pressure digestion vessel is required. Only a trace amount of sample and minimal pretreatment are needed before measurement.

→Trace analysis capability: The total reflection geometry enables detection limits as low as the ppb level, fully meeting the demand for accurate quantification of trace Fe (< 150 ppm) in ultra-clear glass.

→ Simultaneous multi-element analysis: In addition to Fe, information on other impurity elements in glass (such as Cr, Cu, Ni, Ti, etc.) can be obtained simultaneously.

→ Low operating cost: No large consumption of high-purity acids or auxiliary gases is required. The cost per single measurement is significantly lower than that of ICP-based methods.

III. Application Case

3.1 Test Samples

Ordinary soda-lime-silica glass: Fe content 1100 ppm

Ultra-clear soda-lime-silica glass: Fe content 150 ppm

3.2 Test Method

3.2.1 Direct Test Method — Semi-quantitative Analysis of Elements in Glass Samples

A glass piece with a flat surface and dimensions not exceeding 2 cm × 2 cm is cut and clamped onto the sample holder, then directly placed into the instrument for measurement. The test spectra of ordinary glass and ultra-clear glass are shown in the figures below.

Figure 2. Comparison of directly measured spectra of the two types of glass

Conclusion:

Under direct measurement conditions, the difference in iron (Fe) content between ultra-clear glass and ordinary glass can be clearly distinguished. This method offers high sensitivity and simple operation, making it suitable for rapid semi-quantitative analysis of trace elements in glass materials.

3.2.2 Determination of Iron (Fe) Content in Glass Powder by Suspension Method

Method Overview:

A suspension sample introduction–X-ray fluorescence spectrometry method was employed, using an internal standard element to correct for matrix effects and instrument drift, for the quantitative analysis of trace iron (Fe) content in glass powder. The sample was crushed, sieved, and prepared as a homogeneous suspension in dilute nitric acid medium, which was then directly introduced into the instrument for measurement.

Verification of Method Accuracy:

Three certified reference materials of quartz sand were selected and prepared as suspensions following the same procedure, and their Fe contents were determined. The measured values from multiple tests were compared with the certified values to validate the accuracy of the method. The results are shown below.

Verification Conclusion:

The measured values are in good agreement with the certified values, with relatively small deviations, indicating that this method is accurate and reliable.

Determination of Actual Samples:

The above-mentioned method was applied to the ultra-clear glass powder sample for multiple determinations. The test results are as follows:

Test Conclusion:

This method is simple to operate and requires no digestion. The validation results of certified reference materials are in good agreement with the certified values, and the repeatability of actual sample testing is satisfactory. It is suitable for the rapid and accurate determination of trace iron in glass powder and similar powder materials.

IV. Conclusion

In this study, two analytical methods for the determination of trace iron in glass materials were established: the direct test method and the suspension method.

The suspension method was validated using certified reference materials. The relative deviations between the measured values and the certified values were within 2.0%, indicating that the method is accurate and reliable, making it suitable for the quantitative analysis of trace iron in glass powder samples.

The direct test method allows for semi-quantitative analysis of trace elements in glass samples and can effectively distinguish between ordinary glass and ultra-clear glass. It is simple to operate and provides rapid results, making it suitable for rapid discrimination of glass samples.

The two methods complement each other and can meet the requirements for quality control and performance evaluation of glass materials.