Polypropylene syringes (sizes 3, 5, 10, 20, and 50 mL) equipped with a porous polypropylene disc at the bottom (Krchnak, V. and Vagner, J. Peptide Res. 1990, 3, 182-193) are the simplest and least expensive disposable reaction vessel for solid-phase organic synthesis. Syringes enable to carry out solid-phase organic synthesis in virtually any laboratory. Plastic frits are cut from porous polypropylene sheet (porosity 70 micrones).

Handling syringes as reaction vessels is easy. Syringes were charged with resin, solvent used in the following reaction was added to make slurry, and the resin was washed with this solvent (typically 3 mL of solvent per 1 mL of swollen resin). To wash the resin, the solvent plus a small amount of air was drawn into the syringe, the syringe was shaken for half minute and solvent was discharged. An alternative washing procedure was used, when a large number of syringes was handled at the same time. The syringe piston was removed, the syringe was coupled to a needle connected to a vacuum flask, and the resin was washed in "continuous flow" manner with solvent from squeeze bottle (excessive air drawing should be avoided). However, the most convenient handling of syringes are achieved in Domino Blocks.

Syringes are typically kept on a tumbler during the reaction, they can be used at elevated temperature up to 80 - 100 oC, they can be sonicated or used in a microwave oven. However, polypropylene syringes do not tolerate prolonged (overnight) exposure to certain solvent including methylene chloride, tetrahydrofuran, and dioxan. The syringe barrel tends to swell and then the plunger does not provide leak-proof seal. This problem is solved by locking sleeves. Locking sleeve is a polypropylene ring that can be moved up and down the syringe barrel to "lock" the required volume. The locking sleeve contracts the swollen barrel and the plunger seals the syringe.

Five different sized of PP reaction vessels are available. The selection the proper size depends on the amount of resin. The following Table portrays maximum recommended load for typical polystyrene resin.

Syringe volume	Resin quantity
3 mL	100 mg
5 mL	300 mg
10 mL	500 mg
20 mL	1 g
50 mL	3 g

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