Detection and Quantitative Analysis of Tin (Sn) in Plastic Components Using EDX Analysis

Two halogens (chlorine and bromine) and five RoHS elements (Br, Hg, Pb, Cd) are currently included in the EDX analysis of controlled substances for electrical and electronic instruments.

Tin (Sn) is expected to be included in this list as a controlled substance because of the existing rigorous regulations on organic tin compounds.

Organotin compounds cannot be determined and measured with EDX. However, their presence can be detected from a tin elemental analysis using EDX. This article discusses the application of EDX in the quantitative analysis of tin in plastic components.

Experimental Conditions

This experiment used four levels of tin-containing resin standards obtained from Sumika Chemical Analysis Service, as shown below:

Samples Sn Content (ppm)
(1) 0
(2) 310
(3) 700
(4) 1100

Resin Standards with Sn

Figure 1. Resin Standards with Sn

A tin internal-standard-corrected calibration curve plotted utilizing the four samples is illustrated in Figure 2, and the corresponding intensity profiles are presented in Figure 3. Table 1 summarizes the lower limit of detection and calibration curve accuracy of the EDX instruments.

Calibration Curve for Sn in Resin

Figure 2. Calibration Curve for Sn in Resin

Profile of SnKα

Figure 3. Profile of SnKα

Table 1. Accuracy and lower limit of detection for tin

Instrument EDX-LE EDX-GP (720)
Calibration curve accuracy 1.4 1.0
Lower Limit of Detection 7.5 8.2

The aforementioned internal-standard-corrected calibration curve technique was used to carry out 10 repeat measurements involving the 700ppm Sample (3). Table 2 summarizes the repeatability test results.

Table 2. Repeatability

Instrument EDX-LE EDX-GP (720)
Average (ppm) 704.0 697.9
Standard deviation (ppm) 13.8 9.7
Coefficient of variation (%) 2.0 1.4

Experimental Procedure

Revised analytical conditions were set for the seven elements and tin. Then the plastic sample was quantitatively analyzed (Figure 4). A part of the quantitative analysis results are presented in Table 3. Since the analytical conditions of tin and cadmium were the same, there was no change in the total analysis time when compared to the measurement of the initial five or six elements.

Image of plastic sample

Figure 4. Image of plastic sample

Table 3. Excerpt from analysis report for 7 elements

Element Content Unit Judgement
Cd 21.8 3.2 ppm OK
Pb 57.9 4.8 ppm OK
Cr 56.9 5.3 ppm OK
Hg 45.4 2.6 ppm OK
Br 192.6 5.0 ppm OK
Cl ND 27.2 ppm OK
Sn 290.3 15.5 ppm OK

A screening analysis can rapidly validate the correlation of the sample with the reference value relative to the material and product type, or whether the results lie between the gray zone (intermediate area). For that reason, screening analysis conditions were set in the EDX-LE for the seven elements including tin, and the plastic samples was subsequently analyzed.

The screening analysis determination results window is presented in Figure 6, showing the possibility of determining all seven elements, Sn, Cl, Br, Hg, Cr, Pb and Cd. The setting of the threshold values for the tin determination to OK ≤ 700ppm < GRAY < 1300ppm ≤ NG generated the determination result "OK," as expressed below:

Quantitation Value + 3σ= 278.1 + 17.1 = 295.2 < 700 → OK

Plastic Sample Screening Analysis - Determination Results Window

Figure 5. Plastic Sample Screening Analysis - Determination Results Window

Conclusion

The results demonstrate the ability of the EDX Series to perform quantitative analysis of tin at the ppm level in the same way as with the heavy elements, including Br, Hg, Cr, Pb and Cd.

In addition, there is no difference in throughput and total analysis time when compared to the traditional analysis performed under the RoHS analytical conditions. This means that the EDX Series can fully support the modifications of existing analytical conditions, making it suitable for a myriad of applications.

This information has been sourced, reviewed and adapted from materials provided by Shimadzu Scientific Instruments.

For more information on this source, please visit Shimadzu Scientific Instruments.

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