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High-efficiency sample preparation with dimethylformamide for multi-element determination in pharmaceutical materials
Qiang Tu1, Tiebang Wang, Vincent Antonucci
1Merck Research Laboratories, Merck & Co, Inc, RY818-C102, PO Box 2000, 126 E Lincoln Ave, Rahway, NJ 07065, United States. qiang_tu@merck.com
Journal of Pharmaceutical and Biomedical Analysis
|February 4, 2010
Summary
A new "dilute-and-shoot" method using N,N-dimethylformamide (DMF) simplifies sample preparation for ICP-AES analysis in pharmaceutical development. This approach significantly reduces analysis cycle times by up to 90% for challenging samples.
Area of Science:
- Analytical Chemistry
- Pharmaceutical Analysis
Background:
- Pharmaceutical process development requires faster sample analysis cycles.
- Current ICP-based analyses are often limited by slow sample preparation, particularly the digestion of organic compounds.
- A universal diluent for organic matrices is needed to streamline sample preparation.
Purpose of the Study:
- To develop a simplified sample preparation method for ICP-AES analysis using N,N-dimethylformamide (DMF) as a universal organic diluent.
- To optimize an interface for introducing organic solvents into ICP-AES without organic loading.
- To evaluate the stability, sensitivity, and precision of multi-element solutions in DMF for pharmaceutical metal analysis.
Main Methods:
- Utilized N,N-dimethylformamide (DMF) as a universal organic diluent for a "dilute-and-shoot" procedure.
- Implemented an optimized interface with a membrane desolvation unit for introducing organic solvents into ICP-AES.
- Investigated the stability of 15 elements in multi-element DMF solutions with and without stabilizing agents (EDTA) and internal standards (yttrium).
Main Results:
- Addition of EDTA was necessary for physical stability of elements (0.10-0.50 microg/mL) in DMF solution for 2 weeks (recovery >95%).
- Internal standards (yttrium) were crucial for compensating signal drift and matrix effects.
- Achieved a 2-10 fold increase in sensitivity, RSD <3% precision, and 91-111% recoveries.
- Obtained LOQs <10 microg/L in solution, translating to <5 microg/g or microg/mL in pharmaceutical samples.
Conclusions:
- The developed "dilute-and-shoot" method using DMF significantly simplifies sample preparation for ICP-AES analysis.
- This technique reduces analytical cycle times by 60-90% for difficult-to-dissolve pharmaceutical samples.
- Enables enhanced sample handling and automation for metal analysis in pharmaceutical process development.
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