Experimental Poly(3-hydroxybutyrate) (P3HB, M n = 2.6 × 10 5 g mol −1 , ĐM=2.7) was from Sigma Aldrich (St. Louis, MO,USA). All other chemicals and solvents were from Wako pure chemicals (Osaka, Japan) unless otherwise mentioned. 1 μL of P3HB in THF at 1 mg mL −1 was drop-casted on a disposable MALDI target plate (Hudson Surface Technology, New Jersey, USA) to form a polymer thin layer. 1 μL of sodium hydroxide in methanol (10 mg mL −1 ) was deposited on the sample layer and left to air-dry for 5 min. The excess amount of alkaline reagent was washed with distilled water. After drying, 1 μL of 2,4,6-trihydroxyacetophenone (THAP, Protea Biosciences, West Virginia, USA) in THF (20 mg mL −1 ) was applied on the sample spot as matrix. Mass spectra were recorded with a JMS-S3000 SpiralTOFTM mass spectrometer. Plots were computed using msRepeatFinder 3.0 from the peak list exported using msTornado.