Dear Sir. Concerning your issue about how to clean stained quartz cuvette cell of UV spectrophotometer. Before we start the list of cleaning solutions, these are just a few tried and try solutions for cleaning various types of samples such as aqueous, organic, etc:

CUVETTE CLEANING SOLUTION 1:  GOOD FOR AQUEOUS SOLUTIONS

Use this procedure for cleaning microcells, but it can be used on any size cuvette. 

50% 3M HCl and 50% ethanol measured by volume. 

CUVETTE CLEANING SOLUTION 2:  GOOD FOR HARD-TO-REMOVE DEPOSITS

Another recommendation from Beckman on a great solution to remove deposits.

Equal parts by volume ethanol and 3N HCl. Rinse the cell immediately with distilled water, air dry and store. Do not soak the cell in this solution for more than 30 seconds.

CUVETTE CLEANING SOLUTION 3:  GOOD FOR AQUEOUS SOLUTIONS

Wash with nitric acid, 50% is good too, for 10 minutes. Carefully remove the acid. Then wash three times with purified water. Finally rinse with acetone, remove excess and let the cuvette air dry. 

CUVETTE CLEANING SOLUTION 4:  GOOD FOR PROTEINS

To remove protein which is still sticking in the cuvette you might want to use trypsin (I just use the left over trypsin from a cell culture); incubate over night at room temperature, wash the cuvette with H20 and finally flush it with ethanol.

CUVETTE CLEANING SOLUTION 5:  GOOD FOR HEAVY METALS AND STUBBORN CONTAMINANTS

Soak cells in 50% sulfuric acid 2M and 50% DI water.  Cells can be safely be soaked for 20 minutes.  Remove cells from bath and thoroughly rinse with water.  Let air dry.  Also, aqua regia can be used for heavy metals.

CUVETTE CLEANING SOLUTION 6: GOOD FOR ORGANIC MOLECULES

Concentrated HNO3 or 2M HCl for 10 min, then rinse with DI water, and absolute ethanol or HPLC-grade acetone for a final rinse.

CUVETTE CLEANING SOLUTION 7:  GOOD FOR CIRCULAR DICHROISM (CD) CUVETTES

This one is only for quartz cuvettes.  Immerse the cuvette in concentrated nitric acid (68%) at room temperature and let it sit overnight.  This is great for sticky proteins.  Rinse cells with ultra pure water to remove any excess nitric acid.

NOTES ABOUT USING ETHANOL AND ACETONE TO CLEAN PROTEINS:

It's not recommended to start washing cuvettes with ethanol after using it with solutions containing protein. Glass gets stained with protein precipitate which may be hard to remove. It's best to use ethanol for the final rinse after washing the cuvette with a good amount of deionized H2O. Same thing with acetone. It will cause residual salts from the buffer solution to precipitate on the glass, which does not make it cleaner.

NOTES ON WHAT SOLVENTS TO USE:

The purity of solvents used for quartz cuvette cleaning is important for the protection of cells.  Try to find solutions that are spectrophotometric grade.  For rinsing use only pure water such as distilled, RO, or deionized water.  Lastly, try to find detergents with a neutral, or as close to neutral pH.  These detergents should be free of any suspended materials containing no lanolin or oils.

 I think the following below links may help you in your analysis:

http://www.fireflysci.com/news/2015/8/4/quartz-cuvette-cleaning-find-the-best-cleaning-for-your-application

http://www.fireflysci.com/news/2015/9/17/quartz-cuvette-tips-and-tricks

http://www.starnacells.com/d_tech/tech01.html

Thanks

Thank you very much Sir for timely guidance and exhaustive suggestions which are practically helpful...

You may want to check previous RG discussions on cleaning quartz cuvettes: https://www.researchgate.net/post/What_is_the_best_method_to_clean_a_quartz_cuvette https://www.researchgate.net/post/How_do_you_clean_your_platinum_crucible_1_and_your_quartz_cuvettes_2 https://www.researchgate.net/post/Cleaning_polymerized_material_from_a_quartz_cuvette https://www.researchgate.net/post/What_is_the_best_way_to_wash_a_quartz_cuvette_used_with_n-octanol

Thank you Dr. Carlos Araújo Queiroz sir...