18
Flushing Microtip after Use
The Microtip should be thoroughly flushed after each session. Place a 1ml syringe containing
distilled water in each valve in the lower row, turn the valve, and press in the plunger firmly.
Repeat this three times. Finish by passing air through the Microtip and disconnecting. Store it
coiled up and flat to avoid bending of the tip.
Always wear protective goggles when handling caustic
materials
Protein Coatings of Microtip
Certain proteins may have a tendency to coat the inside of a microtip. This may cause the air
bubble (that is used to separate the protein sample from the water in the microtip) to become
stuck or to break up. Tips that are coated with protein can be cleaned by flushing first with 1 M
NaOH, then with buffer solution to get rid of the alkali. If this procedure does not work, try conc.
HCl mixed with an equal volume of methanol (again followed with buffer to remove the acid).
Blockages
Keep syringes in all valves when not in use to avoid the ingress of dust. Never allow precipitant to
come into contact with tubing that has previously contained protein unless it has been cleaned
using alkali or acid – see above. Filter all solutions using a 0.45
m
m filter or equivalent, and
refilter any solutions that become cloudy or contain debris.
Unblocking Microtips
1. First try forcing the debris out of the tip with high pressure. This method is only possible when
the Microtip is full of liquid. Fill a 100
m
l gas-tight syringe with water. Attach a pointed 0.7 mm
needle to it (this is the type of needle that spare syringes come with). Push this into the blocked
bore of the Microtip at the End-Fitting. Press in the plunger of the syringe. Up to 100
atmospheres can be generated by this method.
If this does not work we recommend that the tip is replaced with a new tip
Chemical Inertness
All surfaces that come into contact with solutions are chemically inert fluorocarbon polymers
including FEP and PTFE. Only water comes into contact with the stainless steel needles of the
gas-tight syringes.
Tubing Connections
The needles of the gas-tight syringes are connected to the FEP tubing by enlarging the bore at
the end of the tubing and pressing onto the needle. If any syringes need to be replaced retain the
special needles.
All other connections are made using gripper fittings. These are fitted as follows:
