Challenge for use ND as limits

We are currently working on some enviromental monitering program for Amoxicillin. PLS help me with a few questions:

  1. Recovery factor: what level should we spike on surface?
  2. Consider Area to noise ratio 3:1 as detected. How to determine the Noise. Blank injection or spl injction? How far from each side of active peak.
    3.As envirenmental spl can contain any unknows, how to investigate if we have a positive results as LOD level?

Dear b0b,

For answering your question I am making few assumptions (1) that you have a dedicated facility for the production of penicillin antibiotics (amoxicillin), (2) that your reason for carrying out sampling of amoxicillin (i.e. environmental monitoring) is to know if any cross-contamination occurs between penicillin production area and non-penicillin production areas, and (3) that your company have a well-defined program for the prevention of cross-contamination (if you don’t have, please make sure you have one as environmental monitoring for penicillin residues is not a part of cleaning validation program).

In its guideline relating to cGMP (21 CFR 211.176, Penicillin Contamination), FDA clearly states that “If a reasonable possibility exists that a non-penicillin drug product has been exposed to cross-contamination with penicillin, the non-penicillin drug product shall be tested for the presence of penicillin. Such drug product shall not be marketed if detectable levels are found when tested according to procedures specified in Procedures for Detecting and Measuring Penicillin Contamination in Drugs”.

Guide to Inspections of Dosage form Drug Manufacturer’s states that “If penicillin and non-penicillin products are manufactured on the same premises, whether non-penicillin products are tested for penicillin contamination” (


Similarly, in its guide “Recommendations on Validation Master Plan, Installation and Operational Qualification, Non-Sterile Process Validation, Cleaning Validation”, PIC/S (under section 7.11 Establishment of Limits) states that “For certain allergenic ingredients, penicillins, cephalosporins or potent steroids and cytotoxics, the limit should be below the limit of detection by best available analytical methods. In practice this may mean that dedicated plants are used for these products.”

Based on available guidelines few things are very clear:

  1. The analytical method should be the best available method for detecting amoxicillin residues (i.e. specific and sensitive). The bioassay referenced in 21 CFR 211.176 has a LOD of 0.006 ppm (as Penicillin G using S. Lutea) and a violative detection amount of 0.03 ppm. The method is limited to the detection of Penicillin G and ampicillin in a limited number of products listed in the referenced method, not including other beta-lactam antibiotics. This means that the method should be able to detect as low as 0.006 ppm of residue, although technologies are available which can detect residues even at lower levels. I would recommend you to use LC-MS for this purpose. Check out these references:
  • Carter, G.G; A Review of Procedures for the Detection of Residual Penicillins in Drugs, (Nov. 1977) FDA By-Lines 8, 119-137 (available at )
  • Dr. Ralf Wottrich, Jose Colon and Tim Wortley; Cross contamination control in Pharmaceutical Environments using Ion Trap Mobility Spectrometry; GE White Paper ( )
  1. The amount of residue detected in non-penicillin product or non-penicillin production area should be lower than the set LOD.

  2. As a part of prevention of cross-contamination program, not only a firm should have an environmental monitoring program but also a program to check the presence of penicillin residues in non-penicillin products.

Now coming back to your query (I hope that you have the validated analytical method which could give you expected results), I have summarized my answers as follows:


  • [b]Performing recovery studies[/b]: In order to perform recovery studies you have to spike the amount of amoxicillin on to the surface at LOD level i.e. for example, if the LOD of the method is 0.006 ppm, you need to spike the surface with 0.006 ppm of amoxicillin. The problem with spiking at LOD level is that if the recovery of sampling method is low, you might not be able to detect the residue in the sample. In that case, you need to perform spiking at 100%, 200%, 300%, 400% and 500% level of LOD (include replicates). Select the lowest % recovery as recovery factor. Try to develop sampling method in such a manner that you are able to recover >70% of the amount spiked (based on the available literature it has been proven that the sampling methods could achieve recovery more than 70%). If you need to simplify the whole procedure then you may spike at concentration 170% of LOD, assuming that a recovery of 70% is considered acceptable as per company policy (you may spike at others levels depending on what you feel is acceptable as there is no guideline specifying the recovery factors for such studies).
  • [b]Developing analytical method[/b]: Both your questions (2) & (3) are related to the analytical method (i.e. related to analytical method development). Developing a method where one has to determine the traces of amoxicillin residues in non-penicillin products is fairly easy as the possible interferences are known. When developing an analytical method which involves analysis of samples from production areas (environmental monitoring samples), where the potential interferences are unknown, is difficult. Hence, it becomes necessary to develop a method that is specific for the residue concerned. In order to check possible interferences by unknowns (or to determine noise), take few blank samples (may or may not contain amoxicillin residues) from worst case locations of the production area (using the same sampling solvent) and spike with known amount of residue. Analyze and evaluate. It would then be easy to determine any possible unknowns eluting at the same retention time. When trying to determine LOD, use spiked concentrations of these blank samples rather then using standard solution. Once developed, validate the method. Some useful references: [LIST=1]
  • Hakimipour, Fred, “[b]Penicillin Decontamination Procedures for Pharmaceutical Manufacturing Facility[/b],” Pharmaceutical Technology, June 1984.
  • Hisao Takahashi, PE, Hiroshi Sakai, and Dr. Daniel H. Gold; “[b]Case Study: Beta-Lactam Decontamination and Cleaning Validation of a Pharmaceutical Manufacturing Facility[/b],” Pharmaceutical Engineering, November/December 2008, Vol. 28 No. 6.
  • Naoto Fukutsu, Takao Kawasaki, Koichi Saito, and Hiroyuki Nakazawa, “[b]An Approach for Decontamination of b -Lactam Antibiotic Residues or Contaminants in the Pharmaceutical Manufacturing Environment[/b],” Chem. Pharm. Bull. 54(9) 1340—1343 (2006).
  • Dear Ovais
    Thank you so much for your answer. It is very helpful. We do have a separate building for Amoxicillin. It is well controlled for cross contamination. Our current analytical method is using HPLC, swabbed as LOQ Level (2µg/100cm²). LOD=0.2µg/100cm²(neat solution). Just wonder

    1. When you swab below LOQ level (100 to 500% of LOD), the result is not quantified, how to calculate the recovery factor?
    2. The 0.006ppm is used for check cross contamination from products. In terms of environmental (like floor), is that 0.2µg/100cm² as LOD good enough?
      3. The way how to investigate the positive results. As chemist we will report any peak within 3% Rt and above 3:1 ratio as DETECTED. It can be noise or unknowns; this will cause a lot of problems for company.

    Dear Mr b0b,

    Good to know that your company has a dedicated facility for the production of Amoxicillin and that the cross-contamination issue is taken care of. Analytical method is the most important factor when developing a cross-contamination program (environmental monitoring/residue testing in products) for penicillin products and is the focus of regulatory inspectors. For your information (you will be surprised to know), analytical methods are available which could detect penicillin (& related compounds) residues upto a level of 5-10 ppb (parts per billion) or even lower in non-pharmaceutical products such as meat, milk etc. Hence, same is expected of analytical methods used in pharmaceutical industry. The problem with most of HPLC methods (used for detection of penicillin & related compound residues) is that they are not able to achieve this sensitivity requirement. HPLC seems to work well for the quantitation of penicillins. However, many other substances are known to absorb at the wavelengths used for detection of penicillins making it difficult to deal with issues such as unwanted peaks and interferences. It is because of this reason, I suggested you in the previous post to use more specific method for the detection of penicillins. Like you said, the LOD level for analytical method is 2µg/100cm², which I believe is not sufficient enough to get through regulatory inspectors. If you refer to reference #2 of the previous post (available here,
    , in pdf format), you will see that the researchers are able to achieve a LOD level of 0.6 ng/cm2 (i.e. a LOD value of 60 ng/100cm²) using LC/MS/MS method. If you feel that LC/MS/MS is an expensive proposition then use microbiological assay method proposed by FDA (easier to justify).

    Coming back to your concerns, I try to answer them, one by one:

    1. When you swab below LOQ level (100 to 500% of LOD), the result is not quantified, how to calculate the recovery factor?

    When you are dealing with penicillin residues you need not to quantify, you need to detect. To make things easier, you may perform recovery studies by spiking coupons at LOQ level (as it is known the more is the amount of residue, the more difficult it is to pick the residue by a swab). Since the swab recovery decreases with increase in the amount of residue, the recovery factor obtained (by spiking at LOQ level) would be applicable in conditions when the residue is present at lower (<LOQ) levels. In order to verify the recovery, you may spike at LOD+(100-RF)%xLOD level (where RF = %Recovery) and check if you can detect the residue or not. For example, if you recovery factor is 80%, then you need to spike 100 cm2 coupon with 120% of LOD (i.e. in your case 0.24 µg), swab the surface, analyze the surface and check if you can detect the residue.

    1. The 0.006ppm is used for check cross contamination from products. In terms of environmental (like floor), is that 0.2 µg/100cm² as LOD good enough?

    LOD level of 0.2 µg/100cm² may be good enough provided you are testing your products for Amoxycillin residues on regular basis (where the amount of residue has been found to be lower than 0.006ppm or ND). It totally depends on the purpose for which you want to conduct environmental monitoring. If your purpose is to find areas which are highly (possibly/probably) contaminated with Amoxycillin residues or you want to investigate the route/source of contamination or you want to verify cleaning of premises then LOD level of 0.2 µg/100cm² is good enough. Testing of products & equipment surfaces for traces of Penicillins require LOD level far lower than that.

    1. The way how to investigate the positive results. As chemist we will report any peak within 3% Rt and above 3:1 ratio as DETECTED. It can be noise or unknowns; this will cause a lot of problems for company.

    I think I have discussed the issue already in the beginning itself. This is the disadvantage of using HPLC method for detection of Penicillin residues. Try to look for more specific method.

    Hope it clarifies the concerns . . . . . :slight_smile:


    Thank you so much for all your kindly help. The information is so helpful, Great stuff.

    Thank you for this topic.Makes my concerns easier to understand.

    What if a non pen product, a carbapenem is produced in same facility?Is it acceptable? Both are betalactams.If acceptable, shall same ND limits applies?Thank you very much.

    Latest FDA guidance clearly states that Penicillin manufacturers must have seperate facilities for different Penicillin Derived products or classes.
    That means
    Penicillin Derivatives like Ampicillin Etc

    all these classes must have decicated facilities. No manufacturing of one class of compound in another class.