Question: Does commercial low-grade acid need purification before cleaning?
Answer: No.
Our Acid Cleaner has applied a sub-boiling technique that is widely used in acid purification. High purity freshly distilled vapor is guaranteed for as long as sub-boiling is maintained. For some applications which require only ppb or high ppt level cleaning, boiling may be considered.
Question: Is the Pre-cleaning step necessary?
Answer: No.
Pre-cleaning via rinsing the labware with DI-water helps leach high concentration metal elements and is ideal for the flame AAS method. However, acid vapor cleaning is the key step for trace level decontamination.
Question: For the acid cleaning step is it better to run the program longer?
Answer: It depends.
Normally, the contaminant level will drop to low ppt after 4-5 hours of acid cleaning, however you can adjust the cleaning period based on your needs.
Question: What factors control the length of the acid cleaning cycle in order to reach specific cleanliness?
Answer: Except for the guaranteed sub-boiling condition, the material and shape of the labware also are important for the desired cleanliness level. Typically, it is easier to decontaminate PTFE labware than glassware. Also, wider and shorter labware is easier to clean than those that are longer and narrower. Similarly, cylinder-shaped containers are easier to clean than those that are cone-shaped.
Question: After the rinse cycle does the acid residue seem higher compared to manual rinsing?
Answer: The purpose of rinsing is to bring down the acid residue for safety reasons and to help with subsequent drying. Achieving an extremely low acid residue level is not necessary for trace element analysis as long as the level is low enough to be safe. In our method for ideal efficiency, the auto-rinsing process uses about 250 mL DI-water. This uses much less water consumption compared to manual rinsing. Furthermore, Teflon liners are known to absorb some of the acids during the high-pressure environment of a microwave.
Question: Is the rinsing process still needed since it does not help with leaching metal elements?
Answer: Yes.
It helps with the auto-drying process by lowering the acid residue during the auto-rinsing.
Question: Why are some of the labware not completely dry after the hot air-drying cycle?
Answer: The drying period varies with the type and amount of vessels. Similar to the acid cleaning process, it takes more time to dry vessels that are narrower and longer than those that are shorter and wider. Lab technicians should adjust the drying period based on their needs.
Question: How much water and acid are needed for the acid vapor cleaning process?
Answer: When there is a 1:1 ratio mixing of acid and water, in most cases a total of 400mL is sufficient.
Question: What is the acid consumption?
Answer: For most users, nitric acid is the common cleaning media. To achieve desired cleanliness, concentrated acid is not required with our instrument. We suggest diluting the concentrated acid with the same amount of DI-water. 400-600mL of the diluted nitric acid is required for a single cleaning cycle. Our data suggests that 500mL diluted nitric acid will guarantee the contaminant residue be decreased to ppt level.
Question: What is required for acid purity?
Answer: A low ppt level of contaminant is desired for most users. To achieve this high purity acid is required by other acid cleaning apparatus. Using the RTC technique, Amerlab, without the use of expensive commercial high purity acid, guarantees the sub-boiling process. This generates the ultra-pure acid vapor. Moreover, with the OWV technique, the waste acid is directly drained from the cleaning chamber which avoids cross-contamination. With these two unique techniques, Amerlab achieves much better cleaning results compared to rivals.
Question: Is the waste acid recyclable?
Answer: The waste acid is drained to the waste acid bottle after each cleaning cycle. If the desired contaminant residue level is moderate the waste acid may be reused several times. There is no unique answer as to how many times the acid can be recycled. It all depends upon individual needs. The user should experiment on how many times the acid can be reused; This can be done by taking a blank sample from the cleaned vessels. If the user wishes to reach the ppt level we suggest not recycling the acid.
Question: Is the waste acid vapor collected?
Answer: There is acid vapor escaping from the top of the lid to ensure pressure balance within the cleaning chamber. Also, the vacuum pump assisting in the draining of the waste acid will pump out some acid vapor from the waste acid bottle. The acid vapor from both paths will be collected and neutralized by our built-in scrubber. The lid of the cleaner is sealed with threads to the main body so as to avoid leaking any acid vapor. The rinsing and drying process will aid in getting rid of most of the acid residue. After drying when you open the lid there is no acid vapor rising from the chamber. Overall, the fully automated model automates everything for you.
Question: What is the average cleaning time?
Answer: The total cleaning time varies by type of vessel, the degree of contamination and desired contaminant residue level. For example, volumetric flasks and Erlenmeyer flasks will need a longer time to clean compared to microwave digestion liners. Heavily contaminated vessels will take longer to clean. Attempting to reach a lower contaminant residue level will also take longer to clean. The typical acid cleaning process takes 1-4 hours and the rinsing process takes 1-2 hours. The drying time varies among different types of vessels. For example, the cleaning duration of the shorter and wider 100mL digestion liners take 1-hour less than the longer and thinner 55mL liners.
Question: What is the cleaning performance?
Answer: The cleaning result depends on the extent of contamination as well as the purity of the cleaning acid. Typically, the contaminant concentration will decrease by 1000 times with ppm-level contamination, 100-1000 times or more with ppb level contamination and 10-100 times or more with ppt level contamination.