A new graphene oxide/polypyrrole foam material with pipette-tip solid-phase extraction for determination of three auxins in papaya juice

• Graphene oxide/polypyrrole foam materials.
• Pipette tip solid-phase extraction.
• High adsorption and purification capacity to auxins in papaya juice.
• Good sensitivity and effective extraction of auxins.

A new material, graphene oxide/polypyrrole (GO/Ppy), was synthesized by mixing graphene oxide and polypyrrole in a specific proportion. It possesses a unique structure similar to that of foam. A homemade pipette-tip solid-phase extraction (PT-SPE) device, which is more simple and convenient than traditional devices, was used for saving reagents and operation time. When GO/Ppy was used as the adsorbent of PT-SPE for determining three auxins (indole-3-propionic acid, indole-3-butyric acid, and 1-naphthaleneacetic acid) present in trace amounts in papaya juice, it showed high affinity and adsorption capacity for all the three auxins. GO/Ppy-PT-SPE also had a significant capacity for eliminating the interferences from the papaya juice matrix. Under optimized conditions, a good linearity of auxins was obtained in the range 16.3–812.5 ng g−1; the average recoveries at the three spiked levels of the three auxins ranged from 89.4% to 105.6% with the relative standard deviations ≤3.0%. Meanwhile, six papaya juice samples with different growth stages were analyzed under optimum conditions, and trace auxins in the range 18.3–100.6 ng g−1 were observed. Because of its high selectivity, simplicity, and reliability, the GO/Ppy-PT-SPE method developed herein can be potentially applied for determining trace auxins in complex biological samples.