Obtaining and Diluting Acetone for Use in Spectrophotometry

[klusener]

How do i get it or where do i get it? i need to use it to make an extract with a chlorophyll solution, so i can measure the optical density of the extract with a spectrophotometer...

 

[klusener]

this is the procedure i am planning to use:

Measuring the Concentration of Chlorophyll in a Leaf

For this work you will make use of aa spectrophotometer to measure the optical density of a chlorophyll solution in order to determine the concentration of chlorophyll in a leaf.

Measure 1 g of fresh leaf tissue and cut the leaves into small pieces (about 1 mm wide) with scissors or razor blade. Extract the pigment by grinding the cut tissue for 5 minutes in 100 ml of 85% acetone in a mortar and pestle.

Transfer the homogenate to a Buchner funnel fitted with Whatman No. 1 filter paper and filter the extract using the vacuum units as demonstrated by the instructor. Transfer the filtered extract to a 100-ml volumetric flask and make up to volume with 85% acetone.

Measure the optical density (absorbance) of the extract with the spectrophotometer. Measure optical density at both 663 nm and 644 nm. These are positions in the spectrum where maximum absorption by chlorophyll a and b occur. The concentration of chlorophyll a and b, in mg per g of tissue, is calculated by the formula:

mg chlorophyll a/g tissue = 1.07 (O.D. 663) - 0.094 (O.D. 644)

mg chlorophyll b/g tissue = 1.77 (O.D. 644) - 0.280 (O.D. 663)

The constants used in these calculations have been determined empirically (Arnon, D. I., "Copper enzymes in isolated chloroplasts; polyphenol-oxidase in Beta vulgaris," Plant Physiol. 24:1-15, 1949; Koski, V., "Chlorophyll formation in seedlings of Zea mays L.," Arch. Biochem. Biophys. 29:339-343, 1950).

 

[Evo]

I've seen acetone at the hardware store, but where you live, I wouldn't know.

 

[thunderfvck]

Yes, hardware store...About 98-99% pure or something.

 

[klusener]

k, if i get that, would i dilute it with water? Pardon my complete ignorance on this subject... but one of my friends said that pure acetone evaporates very quickly, but i guess my main question is if after i manage to get the pure acetone, to bring it down to 85%, i need to dilute it with water...

 

[cbass69187]

I would order it from a chemical supply company and then dilute with deionized, distilled water.

 

[ShawnD]

k, if i get that, would i dilute it with water? Pardon my complete ignorance on this subject... but one of my friends said that pure acetone evaporates very quickly, but i guess my main question is if after i manage to get the pure acetone, to bring it down to 85%, i need to dilute it with water...

Yes acetone evaporates extremely fast, and yes you can mix it with water. You can also just dump it down the sink since there are no real environmental regulations against doing so.
The hardware store acetone should be more than pure enough for what you are doing. Unless you're using some kind of fancy instrument like a GC, you don't really need chemistry grade supplies.