Recommended cleaning method for PFA utensils——trace analysis, medicine, semiconductor----Nanjing Binglab

PFA meltable polytetrafluoroethylene is widely used in semiconductor, geology, biotechnology and other fields due to its excellent chemical properties. How to effectively clean PFA utensils and avoid cross-contamination is very important.

Initial cleaning and cleaning procedures after each use of new PFA labware, including all types of bottles, vary by application, especially if PFA labware is used for sample preparation or sample pretreatment for trace metal analysis.

Nanjing Binglab has been engaged in the R&D and production of PFA vessels for nearly 30 years. Its PFA laboratory products are distributed in thousands of laboratories around the world and used in many different applications. It has rich practical experience. Some cleaning methods of PFA utensils are summarized here for your reference.

PFA series experimental utensils

The PFA vessels used in the cleaning methods mentioned in this article were all supplied by Nanjing Binglab. It should be noted that the cleaning method mentioned below is not the only effective cleaning method for PFA utensils. Each experimenter can use this method as a basis and improve the method according to their own needs to suit the purpose of the current experiment. The following methods are not only applicable to PFA, but also applicable to FEP material containers.

NOTE: Remember not to use brushes or abrasives to clean any PFA labware – these can scratch the surface, which can trap metal and organic contaminants and prevent effective cleaning.

A. Initial cleaning of PFA labware before first use after purchase

a) Applicable object: routine laboratory, all kinds of PFA vessels

Procedure: 1. Thoroughly rinse the labware inside and out with deionized water (DIW) to remove any surface contamination; 2. If desired, a more thorough cleaning can be achieved by soaking in a solution of mild alkaline cleaner (eg: 1% Micro 90) and heating to 100°C to remove any organic residue. Let it cool and rinse off with DIW.

b) Applicable object: trace metal laboratory, PFA reagent bottle

In trace metal laboratories, PFA reagent bottles are usually used as containers for solutions and standards. The PFA reagent bottle can also be used as a collection bottle of the SCH series acid purification system. Additionally collection bottles are often used to store the high purity acid produced by the acid purifier. When used for ultra-trace (low PPT level) metals, such as storage of high-purity acid, it should be thoroughly cleaned before first use. The recommended method is as follows:

1. Rinse the bottle thoroughly with deionized water (DIW)

2. Fill with a mixed solution of 2% high-purity HNO3+1% high-purity HF (if there is no HF, you can use HNO3 alone), tighten the bottle cap and seal

3. Store the bottle at 50°C for at least 48 hours (preferably 7 days)

4. Empty the bottle and rinse thoroughly with DIW

5. Repeat steps 2-4

6. Cleaning is complete and the bottle is now ready for ultra-trace use.

B. Cleaning of PFA labware after each use

Ideal for: PFA vials for geochemical sample digestion

Digestion of geological samples prior to isotope analysis by TIMS or MC-ICP-MS is one of the most challenging ultra-trace applications for PFA labware. Stringent cleaning procedures must be followed for the PFA vials used in the digestion step. Every lab has its own cleaning procedures, and they all vary slightly. Below are two typical examples of cleaning procedures for PFA vials and caps.

Method A

1. Clean the vial mechanically by gently wiping the inside of the vial with a solution of laboratory lint-free tissue and an acidic cleaner/detergent (eg: 2% Citranox) to remove digestive residue – be careful not to scratch the surface

2. Immerse the vial in 50% aqua regia in the Savillex Vial Cleaning System. Heat to about 90°C for at least 24 hours

1. Remove from the vial cleaning system and repeat step 2, but this time use DIW for soaking

2. Remove from the vial cleaning system and repeat step 2, but this time use 50% HNO3 for soaking

3. Repeat step 3

4. Remove from canister and rinse thoroughly with DIW.

CAUTION: Under certain conditions, washing PFA with HCl and HNO3 at elevated temperatures can lead to the formation of white deposits on the surface of the PFA. This can cause the PFA to take on a cloudy appearance. To avoid this, use HNO3 instead of aqua regia.

Method B

1. Mechanically clean the vial by gently wiping the interior with a lab lint-free tissue – be careful not to scratch the surface

2. Immerse the vial in a dilute solution of mild alkaline detergent (eg 1% Micro 90) from the Vial Wash System. Heat to 100 °C to remove any organic residues. Let it cool and rinse with DIW.

1. Immerse the vial in 6M HNO3 in the vial wash system. Heat to about 100°C for 6 hours

2. Remove from vial wash system and rinse thoroughly with DIW

3. Add 3-4 mL of high-purity 6M HNO3 to each vial and tighten the cap to seal. Place on a graphite-resistant electric heating plate and heat gently until needed (the longer the better – even days if possible).

Graphite corrosion resistant electric heating plate

6. Empty and rinse thoroughly with DIW.

For PFA labware that is used in medical/biopharmaceuticals, not only thorough cleaning is required, but strict sterilization is also required. For the cleaning and sterilization of PFA laboratory utensils used in medical/biopharmaceuticals, please refer to the following scheme:

C. Cleaning and sterilization of PFA laboratory ware for medical/biopharmaceutical

a) Initial cleaning: Initial cleaning of PFA labware for medical/biopharmaceuticals

1. Thoroughly rinse the labware interior and exterior with DIW to remove any surface contamination

2. If desired, a more thorough cleaning can be achieved by soaking in a solution of a mild alkaline cleaner (eg: 1% Micro 90) and heating to 100°C to remove any organic residue. Let it cool and rinse off with DIW.

3. 
   

b) Sterilization: Sterilization of PFA labware for medical/biopharmaceuticals

1. Put the labware in the autoclave, remove the airtight lid and leave it open (this is important to avoid damaging the labware)

2. Autoclave at 121°C for 90 minutes and allow to cool

   
   

NOTE: PFA labware can be sterilized by all conventional methods except gamma radiation and electron beam.