Acid washing and rinsing of glassware is important to remove bound metals. This is very important for metals like iron, and probably for magnesium, especially when making defined media with known amounts of metals.

Acid washing and rinsing of glassware is important to remove bound metals. This is very important for metals like iron, and probably for magnesium, especially when making defined media with known amounts of metals.

Acid wash of glassware was essential for some of our highly sensitive experiments with metals.

The general procedures of cleaning lab glass wares can be as follows. This is not a specific procedure, but a generalized one suitable in a biological/chemical lab:

1. Clean with tap water at least 3 times.

2. Apply specific detergent to all parts, and

3. Clean with tap water at least 3 times properly.

4. Rinse all sides with 1% HCl solution properly.

5. Rinse with tap water.

6. Finally rinse with distilled water properly.

7. Dry in a shelf equipped with light blower/heater.

According to my concept just washing with a mild detergent followed by rinsing in distilled water is sufficient.Continuous acid washing can hamper the glass wares.For specific purposes only we can use acid wash i.e like when you are doing experiments with metal salts.You can go for acid wash.I think routine wash in acid may not be good for the glasswares.

Thank you for your answers, but alas, I do not see a concrete answer how many times to rinse after washing we have to do to be sure in cleanliness  glassware. Dear Mr. Tek Bahadur Gurung, what do you mean "properly"? In accordance with the requirements of GMP, all glassware for experiments must be clean. Respectively, the cleansing procedure  must be validated. In case of machine washing everything is simple, but what to do with manual cleaning? I guess in order to prove the purity of laboratory glassware we need to set number of final rinsing by DI water or WFI. If parameters of rinsing water are within the allowable range that means laboratory glassware is clean. Am I mistaken?

Glassware cleaning procedures are typically specific to the method you are following.  For example, many organic analysis methods call for 3x rinse with DI water following washing. For example, see methods in 40 CFR Part 63.

Dear Ms. Jenia Tufts.

Excuse me for an indelicate question, but which subpart in 40 CFR Part 63 should I see?

Thanks for advance!

In many instances the stringency of the washing procedures is in part determined by the end use of the glassware.  For general microbiology and chemistry often I used a wash in gentle detergent follow by three rinses in tap water and three rinses in double distilled water and a final rinse in deionized water.

For work in biochemistry where contamination with heavy metal ions might be disruptive using higher quality glass with addition of acid washes were necessary following washes with high quality detergents certified low in metals, salts and phosphates.  Then rinses in MilliQ water or other suitably purified water was necessary.  

What we did to verify our procedure was follow the extraction or reaction method using empty glassware only the solvents, enzymes, buffers and reagents etc.and analyze the solution generated from contact with all the glassware used in the process for the presence of the known contaminants we would expect to interfere.

Once you have repeated the process sufficiently to document that your glassware is free or within acceptable limits of contaminants you are trying to avoid then you can say your process is validated.  You have established a procedure and verified the procedure works for your process.  If you are seeing contamination have your reagents verified by an independent laboratory or your own equipment if available for the contaminants your are seeing.

To ensure that the glassware is clean and there is no soap residu(that what all the rinsing is suppose to remove) a simple indicative test could be performed using a pH indicator die.  A few drop in of the dye (bromothymol blue) is added to the interior of the glassware- it react rapidely if it stay is orignal coulour (neutral) you rinces proprelly.  If coulour chages that you have a soap residu and your rince was incorrect.  After this initial wash if your method ask for a special treatement before use as a acid treatment , it could be apply to your clean glasseware.

I always rinse what ever substance/reagents I was using with distilled water twice from my glassware, then I soak them in Extran diluted in distilled water for an hour after which I rinse twice in distilled water before I dry in an oven.

Thanks all who added their answers. Dear Noliwe Lebani! Tell us please, how do you prove that after all your activities with laboratory glassware is really clean? Moreover, you did not specify what kind of  Extran has been used. I think that you are able to take any appropriate detergent (not Extran) but after using it you should rinse all glassware with DI water. Question is how many times? From my expirience I can assert that  double rinsing is not sufficient to make glassware clean. Unless, of course, you use an infinitely large amount of rinsing water and rinse glassware endlessly. From validation's point of view, glassware washed by your technique is not clean. In addition, I do not think, that drying some graduated measuring glassware in an oven is rational because of losing its calibration properties.

Our discussion is ongoing!

Regards

In order to determine whether your procedures are effectively suitable for your studies, you should compare to a standard, or in your case where you cannot find one, create one. It depends on what you intend to use the glassware for. If, in example, one was to use the glassware for mass spec, then you could use your results in mass spec with brand new, freshly rinsed glassware, to compare other glassware. Compare it to your worst results and create a procedure in which all of glassware, once cleaned, can obtain suitable results to the standard.  There is no grand standard because each lab uses it's glassware differently for different purposes, even within the lab itself to the individual researchers. 

You could even setup quick detection methods with solvents and such if you were so inclined.  Hope this was clear enough.

Acid washing, solvent washing, and detergent washing are most prevalent methods used in chemical laboratories. The cleanliness in a chemical laboratory not depends on rinses but depends on solubility and exposure time or treatment time then wasing method. For microbiology purpose number of rinses (5 cycles) provides only one standard  but for a chemical laboratory two rinses are much enough to find any vessel free of contamination, dust or dirt. Hence, there is no grand standard was made for chemical laboratory. A glassware cleanliness depends on individual researchers or laboratory usable method.

Thank you, two sirs, for yours detailed answers. Nevertheless, yours answers have generated several questions. Here they are.  

Dear Mr. John Goodson. If you used a brand new freshly rinsed glassware, then you should have proved its cleanliness. As far as I can determine from your reply, you accept a new glassware as a standard of cleanliness. But how do you prove that  rinsing of that glassware does not lead to its contamination? And how do you set the number of times you need to rinse? And who can assure you that the new glassware needs only a rinse (how many times)? According to requirements of «The Rules Governing Medicinal Products in the European Union. Volume 4. EU Guidelines to Good Manufacturing Practice Medicinal Products for Human and Veterinary Use  Part II: Basic Requirements for Active Substances used as Starting Materials» p.11 Laboratory Controls:11.11 There should be documented procedures describing sampling, testing, approval or rejection of materials, and recording and storage of laboratory data. So we have a written SOP on cleaning (preparing) lab glassware for both manual and mashine.  Dear Dr. Ravi Kant Upadhyay. Procedure of preparation of laboratory glassware, as you have written above, includes washing glassware either acid or a detergent or other suitable solvent, depending on the potential contamination. Further glassware washed in tap water to get rid of the above mentioned solvents. Finally, glassware needs rinsing with pure water (DI or purified or WFI). However I do not agree with you that cleanliness does not depends on rinses. If you claim so, then please give a link or references. In the experiments we have found that number of  rinses directly affects the purity of the glassware. In the critical case, we took a lot of different glassware contaminated with different substances. We used acid (chromic) washing, and then washed in tap water to remove visible residue of chromic mixture.  Then we washed glassware in a detergent solution, after that we rinsed in running water (5 times each unit of glassvare), and only then rinsed with purified water. The number of rinses required for cleaning glassware from pollutants taking equal to the number, after which the performance of treated water met the acceptance criteria for purified water. Experimental data were collected and recorded. At the moment I have prepared the manuscript, but I wonder which journal it is better to send. Could you give me some examples?

Thanks in advance.

It would appear that this thread is dead but I see that you had asked for more clarification regarding rinses and how many. I can give you more specifics from my own experiences as it would pertain to certain instances and how we qualified our methods in regard to specific purposes. However as many have stated you may have to develop your own standards of clean based on your specific needs or purpose purpose.

Clean by some standards might be lacking for one instance while for others are well beyond the scope required. However, this is often very specific to the ultimate goal and use of glassware. RNA/DNA extraction and purification can require highly pure standards when growing bacteria in a petri dish might be towards the other end of the spectrum as far as making broths and culture medium which will be sterilized via autoclave before use.