Dear all, I need your help because I am quite lost because one of our Subcontractor who must develop different N-nitro- API methods , he want us to change our limits. We are used to have the limit as the following : the AI ÷MDD with MDD is the quantity of API per day (we look for n-nitroso-API) but the subcontractor disagrees and what to apply the MDD as the mass of the tablet. What do you think ?“*When analyzing the active pharmaceutical ingredient (API), there is no issue, since the API itself is the material under analysis, and therefore the two expressions of the result coincide.
In contrast, when analyzing a finished product, the result is obtained on the finished product and can subsequently be expressed relative to the API; however, these two values differ, as they depend on the amount of API contained in the finished product.
Example: if a finished product contains 10% API, and we determine 20 ppb of nitrosamine in the finished product, this value can also be expressed relative to the API. In this case, 20 ppb of nitrosamine in the finished product corresponds to 200 ppb relative to the API, because the finished product contains only 10% API. Thus, the result expressed on the finished product is lower, while the result expressed on the API is higher.
Similarly, if the Maximum Daily Dose (MDD) refers to the API, and we assume in this case that the MDD is 100 mg API/day, then the maximum daily intake of the finished product would be 1 g FP/day. If we further assume that the acceptable intake (AI) for a nitrosamine is 400 ng/day, this translates into:
The content of the nitrosamine in a drug product should be reported with respect to the API using the label claim of the API.
The acceptable intake limit should be calculated considering the maximum daily dose of the drug substance.
To illustrate with your example, let’s say the maximum daily dose of the API is 100 mg/day and each tablet contains 50 mg of the active ingredient. The content of the nitrosamine in each tablet should be calculated considering the label claim (50 mg in this case) irrespective of the tablet weight. However, the overall results should be considered for the MDD (50 mg x 2) and correlated with the acceptable limit.
The nitrosamine limit is relative to the finished product. If the nitrosamine is solely derived from the API, the nitrosamine limit in the API is the same as that of the finished product. Whether it is the API or the finished product, the calculation is based on the API.
Dear all, It is still not clear. I’m coming back to my topic of limit and LOQ calculation to develop a method for analyzing N-nitroso API in the finished product. It appears that if we use the tablet weight to calculate the limits/LOQ, sometimes the limit is so low that it cannot be achieved. Sometimes, just by changing the working standard, we end up with results that are completely out of line and absurd. coming back to my topic of limit and LOQ calculation to develop a method for analyzing N-nitroso API in the finished product. It appears that if we use the tablet weight to calculate the limits/LOQ, sometimes the limit is so low that it cannot be achieved. Sometimes, just by changing the working standard, we end up with results that are completely out of line and absurd.
The limit for nitrosamines is often extremely low. For example, for NDEA the Acceptable Intake (AI) is 18 ng/day. If a product has a high Maximum Daily Dose (MDD), let´s say 1 g, this translates to a maximum concentration of:
Max concentration= 18ng / 1g = 0.018ppm
This is already a significant analytical challenge. But when developing a method, the goal is typically to achieve an LOQ at 10% of the AI, which in this case is:
10% of AI= 0.0018ppm
If your sample solution contains 50 mg API/mL, then the required LOQ in solution becomes:
LOQ= 0.0018ppm / 50 mg/mL = 0.036ng/mL
At such low levels, increasing sample concentration can improve sensitivity (since you don’t need extremely low ng/mL concentrations in your standards). However, this also increases the risk of matrix effects, which can lead to poor recovery and inaccurate quantification. This creates a delicate balancing act between sample concentration and matrix interference.
To mitigate these issues, sample cleanup techniques such as solid-phase extraction (SPE) or liquid-liquid extraction can be helpful. Try switching to different adducts (like sodium for example) if using LC/MS. This does the trick sometimes. Nevertheless, achieving these ultra-trace levels is challenging and often requires careful optimization of both extraction and detection steps.