Lugol's solution is required to form the dye - iodine complex of Gram-positive bacteria. Stock solutions of I2 - KI in water are unstable. Iodine can be lost by evaporation and that can influence the result of the staining as well as affecting the working conditions in that area. Stainless steel parts of staining instruments can also be affected by the iodine in the Lugol's solution. If the concentration of iodine in the Lugol's solution decreases the bacterial smears may become more susceptible to decolourization. Therefore, I2 - KI solutions should always be stored in completely closed bottles.
The problem of iodine loss can be overcome by using polyvinylpyrrolidine (PVP) in the I2 - KI solution. PVP forms a complex with iodine. This complex is more stable and has a longer shelf life. The results of the material treated with Lugol's solution stabilized with PVP will give identical results with regard to differentiation of Gram-positive and Gram negative bacteria compared to the standard Lugol's solution.
Both Lugol's solutions are available - the standard type and the stabilized type. Suitable protocols are available on the internet or on demand.
|Product ||Presentation ||Cat. No. |
|Lugol's solution * || |
250 ml, 1 l
|Lugol's solution stabilized with PVP ** ||1 l ||100567 |
| || || |
| || |
|Gram color (contains Lugol's solution stabilized with PVP) ||5 x 500 ml ||1.11885.0001 |
|Gram-color modified, phenol-free (contains Lugol's solution stabilized with PVP) ||2 x 100 ml |
3 x 190 ml
For further information about the wide range of products available from Merck Millipore for bacteriologica stainings, please contact Merck Millipore (see details above) or EMD Chemicals in the USA or click the More Information link below.
*Cat. No. 109261
I2 3.4 g/l
Kl 6.8 g/l
1 l = 1.01 kg
** Cat. No, 100567
PVP-Iodine 50 g/l
KI 10 g/l
1l = 1.02 kg