Five factors affecting ethylene oxide sterilization: temperature, pressure, humidity, ethylene oxide concentration, sterilization time

 

1. Temperature

 

The conventional limit of temperature is usually 37℃～63℃, and the commonly used suitable temperature is 50±5℃. But when the temperature is high enough to maximize the effect of the drug, if the temperature is increased, the bactericidal effect will no longer be strengthened.

 

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

 

1) Products: materials, physical and chemical properties;

 

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

 

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 pre-vacuum degree determines the amount of residual air, and the residual air can directly affect the ethylene oxide gas, heat, and moisture to reach the inside of the sterilized item, so the sterilization process, especially the vacuum degree before humidification, has an impact on the sterilization effect huge.

 

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) Influence on humidity;

 

4) Set the vacuum degree and the time required to reach the vacuum degree;

 

5) Vacuum duration (holding pressure).

 

3. Humidity

 

The water content of the sterilized items, the drying degree of the microorganism itself, and the relative humidity of the sterilization environment all have a significant impact on the sterilization effect of ethylene oxide. After vacuuming and before adding medicine, the humidity in the sterilizer should be controlled within the range of 30%RH～80%RH.

 

Fourth, the concentration of ethylene oxide

 

300～1000mg/L are commonly used conditions today.

 

Our company's ethylene oxide concentration: 15kg/20m3=750mg/L, 5kg/6m3=833mg/L.

 

The influence of the following factors should be considered:

 

1) The loading capacity of the product;

 

2) The time required to join;

 

3) Residual amount of ethylene oxide.

 

Five, sterilization time

 

The semi-period method is used to verify the microbial performance. Under the condition that all other process parameters except time remain unchanged, the shortest effective time of EO without viable bacteria (half-period) is determined. The action time specified by the sterilization process should be at least twice the half cycle.

 

6. The 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-the number of moles of gas (mol);

 

m-the mass of the gas (g);

 

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

 

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

 

T——The thermodynamic temperature of the gas (K=℃+273.15)

 

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