"before reaction" is a correct and usable part of a sentence in written English.
You can use it to explain the order of events. For example: "Before reaction, the chemicals were added together."
Before reaction, the autoclave was purged with nitrogen to remove air for five times.
Before reaction with the protein, any disulphide bridges must be reduced, and the reducing agent (DTT) removed by dialysis.
Before reaction (a,c, respectively) and after reaction (b,d, respectively) with EtBr molecules in aqueous solution.
Before reaction, the Ru on KY zeolite catalyst was presulfided in situ at 400°C either by a H2S/H2 mixture, or by dimethyl disulfide in n-heptane.
Before reaction catalysts were heated to request temperature of process (different temperatures, from 350 to 450 °C) in air (13 ml min−1 per channel) held in air flow for 2 h and then flushed with N2 for 30 min.
Before reaction termination with SDS sample buffer, the peptides were cleaved from the GST tag with thrombin protease (Amersham) at 25°C for 2 hr.
In other instances, thrombosis appears before reaction in the vein wall.
Equations 1 4 describe the main part of the sequence; reactions 2 and 3 are repeated many times before reaction 4 or some other reaction intervenes to break the chain.
The inset in a shows a bare Ti grid before reaction.
The absorbance at 450 nm (A450) was measured before reaction (A1).
