Before commencing any work, don a laboratory coat along with nitrile gloves
and safety glasses.
For this task the workspace should be well ventilated and free from any distractions.
Pour some cold tap water into a large Nalgene® laboratory beaker.
Arrange the ‘F/A’ samples on the work surface.
Group them by field batch and place them in numerical order, and in rows of up to seven.
For a new field batch, take a bottle of nitric acid from its Safepak® and write the field
batch, your initials and date on the label.
Ensure you are using the correct acid bottle for each field batch.
The dispenser can accommodate up to seven samples for each refill, therefore it is ideal
to remove the caps from one row of seven bottles at a time.
Take the auto-pipette from its box.
You will need one new 5 mL combitip for each field batch acid bottle you use.
Open the sealed polybag containing a new combitip without removing it from the bag
or handling the tip.
The combitip loads into the auto-pipette in a straight, steady motion with even pressure
and audibly clicks into place.
Ensure the display reads “600 µL”.
If necessary, adjust the dial until this quantity is shown.
Check that the display is neither flashing nor has an error code.
Carefully remove the cap from the acid bottle, taking care not to inhale any vapour that
may be released.
Place the combitip into the bottle and fill by firmly and swiftly drawing up the lower
lever as far as it will go.
Now hold the auto-pipette over the laboratory beaker and push down the upper lever once
to prepare it for dispensing.
The top right corner of the display should now say “steps 0”.
You are now ready to start acidifying the samples.
Place the auto-pipette above each sample bottle and dispense a single measure of acid into
each by pushing the upper lever once.
Ensure that the tip does not touch the water sample or the sample bottle.
The steps number in the top right corner of the display should increase by one each time
a measure is dispensed.
After seven measures have been dispensed, the auto-pipette should be refilled with acid,
without the need to expel what remains in the combitip,
so long as the same acid bottle is used.
Always ensure the auto-pipette is kept upright when a tip is inserted.
If tilted, acid could enter the mechanism and damage it.
Ensure the tip does not come into contact with any sample, or any other surface.
If it does, discard and use a new one.
Use a fresh combitip for each day and for each field batch you are working on.
When all the samples in a batch have been acidified, dispense any remaining acid into
the laboratory beaker by pushing the bottom lever down as far as it will go.
Never return acid to the acid bottle.
Eject the combitip into the laboratory beaker by pressing down the top lever.
The priority is to carefully close the acid bottle and return it to the Safepak®.
Now replace the caps on each of the stream water sample bottles.
Place the acidified samples in the labelled ‘F/A’ bags, carefully ensuring that the
numbers on the bottles correspond to the range of numbers on the bag.
To finish, place the laboratory beaker in the sink and rinse any used combitips.
Run the cold water tap and empty the combitips and diluted water and acid solution
into the sink.
Ensure the laboratory beaker is well rinsed after use.
To safely dispose of the combitips, hold them in one hand and use your other hand to pull
a glove over them.
Repeat this process with the other glove.
Now the gloves and combitips can be disposed of in a normal waste bin.
When all the ‘F/A’ samples have been bagged, they must be refrigerated for storage.