FS12.4 An analytical method for p‐tert‐butylphenol‐formaldehyde resin

p‐tert‐Butylphenol‐formaldehyde resin (PTBP‐F‐R) is frequently reported to give positive patch test reactions with uncertain clinical relevance. A possible explanation is deficient knowledge of the sources of exposure. An analytical method for PTBP‐F‐R could be used to investigate products in the patient’s environment. Most individual PTBP‐F‐R substance constitute less than 1% w/w of the resin contributing to analytical difficulties. Objective:  To develop an analytical method for PTBP‐F‐R and to use it to investigate some patients’ products. Methods:  10 identified PTBP‐F‐R substances in silylated form were used as reference substances in gas chromatography‐mass spectrometry (GC‐MS) analysis. Results:  The recording of ion chromatograms for the 3 largest mass peaks in the MS for each reference substance was used to avoid interference of disturbing substances. Demonstration of a PTBP‐F‐R substance was defined as the simultaneous detection the 3 defined mass peaks at the expected retention time and with the same relative intensities as found with the corresponding reference substance. A minimum criterion for the demonstration of PTBP‐F‐R was the demonstration of 3 PTBP‐F‐R substances. PRBP‐F‐R was demonstrated in watchstraps, shoes, glues and ECG‐electrodes. p‐tert‐Butylcatechol, a PTBP‐F‐R substance but also an antioxidant, was demonstrated in: an ECG‐electrode, watchstraps, a prosthesis, a protective mask, a glue, an oil for bikes and in a nail polish. Conclusion:  An analytical method for PTBP‐F‐R was developed, which when applied to products could show the presence of PTBP‐F‐R substances and PTBP‐F‐R in products and indicate contact of clinical relevance.