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- Retrieve an empty nutrient rack from the lab fridge
if needed and record the color key on the sample log sheet.
- Tubes are inverted when empty and should not be
turned over until filled
- Never touch the inside of the cap or tube since
residue from your fingers can contaminate the sample – soap
contain phosphates. If unavoidable – rinse several
times.
- Nutrients are normally drawn from the middle valve
– fill the tube with ~25mls, cap loosely, shake then
dump. Repeat three times.
- Double check the tube number matches the rosette
bottle number.
- Fill the tube completely then flick out several mls
so the sample reaches the base of the neck/threads. Cap
tightly.
- Draw one sample per rosette bottle (except on the
surface bottle). If tube 24 is not needed, draw a duplicate
surface sample.
- Once all the nutrient samples are drawn:
- Carefully tip the nutrient rack until you can see
the sample through the cap of each tube – if a tube is empty
and not inverted, double-check the sample log and fill if necessary.
- fill out a sample label (from the sample log
clipboard) with the time, your initials, total number of samples
- Wrap the label
around tube #1 and carefully re-insert into rack – be sure to
include the extra surface sample to the sample count by listing it as
“+1”
- return the filled rack to the nutrient fridge right
away.
- add your initials to the bottom of the sample
log’s nutrient column
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Common mistakes
are empty tubes that shouldn’t be; missing duplicate surface
sample; contaminated samples; and duplicate draws – two
sample tubes filled from the same bottle
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