Isolation medium

AQA recipe; Cambridge AS & A Biology practical teacher  p 114

PHOSPHATE BUFFER

Dissolve 4.48g Na2HPO4.12H20 and 1.7g KH2PO4 in 500ml distilled water

ISOLATION MEDIUM

Dissolve 34.23g sucrose and 0.19g KCl in phosphate buffer solution (above) and make up to 250ml.

DCPIP

Dissolve 0.01g DCPIP and 0.93g KCl in phosphate buffer solution and make up to 250ml.

All solutions should be kept cool. 

I trialled it yesterday and it worked first time! Keep your spinach under light but cool for a few hours first. All solutions need to be kept cool. I think the key is to dilute the DCPIP to one sixth of the strength that they tell you to make it up to and you should see a colour change in the X tubes in about 2 minutes. The Y tubes with ammonium hydroxide should not change and the A tube in foil may change a bit (probably due to mitochondrial activity which is a different reaction than the one you are testing for).

mike wilson said: ↑

Keeping the solutions cold. Ideally, prepare the day before and overnight in fridge.

Letting the spinach see the light for an hour before use.

Using (relatively) fresh DCPIP to make up the solution.