Factors Affecting The Sterilization Effect Of Ethylene Oxide

Six major factors affecting ethylene oxide sterilization: temperature, pressure, humidity, ethylene oxide concentration, and sterilization time.

1. Temperature

The normal temperature limit is usually between 37℃ and 63℃, and the commonly used suitable temperature is 50±5℃. However, when the temperature is high enough to maximize the effect of the drug, the sterilization effect will no longer be enhanced if the temperature is raised.

The determination of the sterilization temperature is related to the following factors:

1) Product: material, physical and chemical properties;

2) Stacking: total load (<80%), the loaded items cannot touch the cabinet wall, and there is a certain distance between them;

3) Packaging: material, size, thickness, loading quantity;

4) Printing: It should be ensured that the printing quality will not be adversely affected by sterilization.

2. Pressure

The size of the pre-vacuum determines the amount of residual air, and the residual air can directly affect the ethylene oxide gas, heat, and moisture reaching the inside of the sterilized items, so the sterilization process, especially the vacuum degree before humidification, has a huge impact on the sterilization effect.

The pre-vacuum degree should consider the influence of the following factors:

1) The impact on the sterilized items and their packaging;

2) Negative pressure sterilization and positive pressure sterilization;

3) The impact on humidity;

4) The set vacuum degree and the time required to reach the vacuum degree;

5) Vacuum duration (pressure maintenance).

3. Humidity

The moisture content of the sterilized items, the dryness of the microorganisms themselves, and the relative humidity of the sterilization environment have a significant impact on the sterilization effect of ethylene oxide. After vacuuming and before adding drugs, the humidity in the sterilizer should be controlled within the range of 30%RH~80%RH.

4. Ethylene oxide concentration

300~1000mg/L is the commonly used condition today.

Our company's ethylene oxide solubility: 15kg/20m3=690~750mg/L

The following factors should be considered:

1) Product loading;

2) Time required for addition;

3) Residual ethylene oxide.

V. Sterilization time

The half-cycle method is used to verify microbial performance. When all other process parameters except time remain unchanged, the shortest effective action time (half-cycle) of EO without surviving bacteria is determined. The action time specified in the sterilization process should be at least twice the half-cycle.

6. Relationship between sterilization temperature, sterilization pressure and ethylene oxide concentration (ideal gas state equation)

PV=nRT

n=m/M

c=m/V=44*P/(RT)

P--pressure (kPa); 1kPa=0.0102kgf/cm2=0.102×103kgf/m2;

V--volume (L); 1L=1×10-3 m3

n--moles of gas (mol);

m--mass of gas (g);

M--molecular weight of gas, M=44;

R--gas constant (J/mol·K)=8.314; 1J=0.102kgf·m;

T--thermodynamic temperature of gas (K=℃+273.15)

c--concentration of gas (g/L=kg/m3).