EBME Forums Forums Maintenance Technical Assistance Advise needed - Electrolyte Analyzer

We have MEDICA Easyelectrolyte Analyzer installed in our hospital Laboratory.

Recently we have noticed following defect in one of the analyzer. The control reading for the Sodium is always falling on the lower side of the target value. For example for the current batch of normal control, Target value is 140 + /- 5 we are always getting values from 137-139. Never more than 140 or 140 itself.

All the electrodes are recently installed ( one month old). Can you suggest some way to rectify the same.

Any help would be greatly appreciated

with Regards

Sunith

if all your electrodes are new and you are still getting such readings try cleaning the electrodes and any associated tubing /connections or try using a different supplier for your electrolytes.Maybe there is a blockage /dirt that is limiting the free flow of samples and electrolytes.

Hi Sunith,

Forgive my ignorance but I am not all that familiar with ion-sensitive electrodes - except for a little reading I have had to do in the past for "schoolwork" and having performed minimal, routine, QC for blood analysers in the past with a very limited knowledge of chemistry.

I guess the Na ion-specific electrode has a reference electrode seperated by a membrane - similar to a pH electrode in concept i.e. it is likely to be a glass type (but manufactured to be Na selective). If so it will be quite sensitive to temperature, pH and other interfering ions in the sample, in particular.

Have you tried changing the reagents including any buffer solutions or looked for possible sources of contamination in your sampling method or sample path? (as technologist suggests). Is everything, including the control and any sampling cuvettes, capillaries, etc, within their use-by date and been stored, prepared and used as recommended?

I remember that protein/bacterial build-up in the sample path is potentially a problem for electrodes and that enzymes and detergents can be used to remove these contaminants. Recommended cleaning solutions only, of course.......just trying to throw-in a few ideas, seeing as I'm not up to much else at the moment.

Is it possible some other component, i.e. electronics that affects operation/calibration, is faulty, rather than reagents or electrodes?

Guys
Thanks for the replies.
I am yet to figure out what is wrong with these machines. Yesterday I had a mail from equipment manufacturer MEDICA, suggesting that if the value of the control reading are coming within the range the machine is OK.

But how can it be true when all the readings are falling on one side of the mean or target value( in our case it is on lower side always)

Suggestions are welcome

I experienced same problem long time ago, I cleaned the electrodes and tubings. no cure. then I replaced tubings. no cure. then i swapped the electrode and cal solution to other machine. It was fine and got perfect readings. Finally i found bad contacts between elecrode and main board. Try this way and it might help.

Sodium always need conditionings instead of deproteinize. Do several times of conditioning process see can help or not?
How about the flow? is it normal or not?
Check all the tubing (Remove from machine and check using syringe) see wheather block or not.
My one is AVL 988-3.

Conditioning is very important for Na electrodes and it has to be done periodicaly quite often. Usualy after deproteinaizing. Check the expiary dates on all the reagents involved and at the end the connection cables or contacts towards the preamp board. The electrode it self could be causig problems even if it is "new".
good luck

the values of sample may varry for different relevant issues one of that is machine to machine . thats why tolerance is +_ 5 . As you are getiing values within the specified range ,why not it is acceptable .

ashoke
apollo

Control solution is used as part of the Quality Control checks to verify on-going calibration and give confidence in subsequent readings - ideally Na readings should consistently be as close to the Na values given for the control solution as possible. Over time, if the trend is for readings to drift, the calibration is, eventually, likely to shift outside these acceptable tolerances.

Better to discuss the cause for this shift now (whether it's due to variation in control, reagents, electronics, sampling or measurements system), while it's giving valid readings, rather than be left with an analyser out of calibration, i.e. unuseable and giving invalid readings, while you figure out what's causing the problem I suppose.

QC is generally used as a means of determining consistency of readings and any onset of calibration-related problems, i.e. trends in QC measurements (if they are performed routinely on a regular basis and records maintained). So taking notice of any drift or trends can allow QC to be used to flag when servicing or re-calibration, i.e. preventative maintenance, is likely to be required.

Dear friends
These MEDICA electrolyte analyser doesn,t has any deprotinizer or conditioner. Also the machine does its own calibration and cleaning. And there is not much of preventive maintenence to do.