Stain | Stock solution | Staining procedure |
---|---|---|
PTA | 1% (w/v) phosphotungstic acid in water | Mix 30 ml 1% PTA solution + 70 ml absolute ethanol to make 0.3% PTA in 70% ethanol. Keeps indefinitely. |
 |  | Take samples to 70% ethanol. |
 |  | Stain overnight or longer. |
 |  | Change to 70% ethanol. Staining is stable for months. |
 |  | Scan samples in 70% – 100% ethanol |
IKI | 1% iodine metal (I2) + 2% potassium iodide (KI) in water | Dilute to 10% in water just before use. |
 |  | Rinse samples in water. |
 |  | Stain overnight. |
 |  | Wash in water. |
 |  | Can be scanned in water or dehydrated to alcohol. |
I2E, I2M | 1% iodine metal (I2) dissolved in 100% ethanol (I2E) or methanol (I2M) | Use at full concentration or dilute in absolute alcohol. |
 |  | Take samples to 100% alcohol. |
 |  | Stain overnight or longer. |
 |  | Wash in alcohol. |
 |  | Stain does not need to be completely washed out before scanning. |
Osmium tetroxide | standard EM post-fixation | Same as routine EM processing. |
 |  | Osmium-stained samples can be scanned in resin blocks, with some loss of contrast. |