In order to discover the compounds in PA responsible for reducing silver ions to zero-valent silver, AgNPs solutions were centrifuged, and the supernatant subjected to CG-MS. Initially, a PA solution containing 282.0 mL of water +9.0 mL of AP + 9.0 mL of NaOH (1.0 mol L−1) was set as the standard to be compared with the supernatant of AgNPs. 300 mL were taken from both the PA solution and supernatant and had their pH adjusted to 5. Afterwards, 5 mL of dichloromethane were added to both aliquots to extract the organic compounds, with 2 mL of the organic phase reserved for GC-MS analysis.
CG-MS experiments were carried out in a SHIMADZU GC-2010-PLUS spectrometer equipped with a SH-Rtx-5MS column (30 m × 0.25 mm) under the following parameters: ultrapure helium (99.9995%) as carrier gas at 1.0 mL min−1; sample volume of 1 μL at a split ratio of 1:100; inlet temperature = 280 °C; ion source temperature = 230 °C; column temperature = 40 °C; heating rate of 5 °C min−1 until 180 °C, where kept for 2.0 min; heating rate of 7 °C min−1 until 260 °C, where kept for 5 min.
CG-MS experiments were carried out in a SHIMADZU GC-2010-PLUS spectrometer equipped with a SH-Rtx-5MS column (30 m × 0.25 mm) under the following parameters: ultrapure helium (99.9995%) as carrier gas at 1.0 mL min−1; sample volume of 1 μL at a split ratio of 1:100; inlet temperature = 280 °C; ion source temperature = 230 °C; column temperature = 40 °C; heating rate of 5 °C min−1 until 180 °C, where kept for 2.0 min; heating rate of 7 °C min−1 until 260 °C, where kept for 5 min.