Extractables & Leachables

Extractables and Leachables are probably the two most notable regulatory-driven analyses associated with non-targeted screening. However, any analysis that involves detection of compounds in a sample without a-priori knowledge of their possible presence constitutes a nontargeted screen analysis.

What is an Extractable, a Leachable and Why is E&L Testing Needed?

Extractables and Leachables testing (E&L) of biomedical devices and their components are fundamental test protocols, based on requirements of ISO 10993-13 and 10993-18, performed to chemically characterize device materials, specifically the extractable chemical fraction (“residuals”).

• Extractables are the accepted term for all non-covalently bound materials present in device components.  Extraction solvents and extraction conditions are selected to provide “exhaustive”, i.e., complete, extraction of this fraction.
• Leachablesare residuals extracted by solvents and extraction conditions that simulate the physiological environment of the biomedical device - thus aqueous solvents such as phosphate-buffered saline at 35°C are typical conditions.

Every E&L Analysis Requires a Custom Analysis Plan.   What are the Key Steps in an Extractables Work Flow?

• EXTRACTION
• ANALYTICAL METHODS
• STUDY STANDARDS AND ON-THE-FLY METHOD VALIDATION
• DATA ANALYSIS
• QUANTIFICATION
• REPORTING

EXTRACTION

An extractables analysis plan starts with knowledge of the device component materials, an understanding of the potential residuals, and consideration of the data expected out of the analysis. From these follow the specification of extraction conditions including extraction process, solvent , temperature, duration, sample configuration, and extract volume.  Mass Spec Lab performs different extraction operations depending on the application.  Thus, a choice is made between Soxhlet extraction, reflux extraction, liquid-liquid extraction, mild controlled extended incubation, or thermoplastic polymer dissolution/precipitations for additives analysis.  Valid results, especially of trace residuals, require good experimental design and attention to preparation of solvent blank controls and inclusion of test sample replicates.

ANALYTICAL METHODS

Mass Spec Lab performs a battery of complementary analytical tests on recovered extracts or leachates with characterization of residual analytes as the ultimate goal.  Analytical tests can include gravimetry, UV/VIS analysis, UPLC/PDA-UV/qTof-MS, GC/MS, FTIR and GPC.   

• Gravimetry yields the residual fraction quantity defined as a percentage of the unextracted sample weight.
• UV/VIS spectrophotometry provides a non-selective screen of the extract for UVVIS active components.
• ATR-FTIR or microscopic FTIR of deposited films of the extract provide an IR fingerprint of the extract residual fraction that can be especially useful in identification of higher molecular weight polymeric components often detected in residual fractions.
• Chromatographic methods with mass spectrometric detectors are strategically applied to extracts for chemical identification and quantification of residual analytes.  
  • GC/EI-MS coupled with the NIST11 mass spectral library and APGC/qTof MS accurate mass instrumental methods are applied to volatile and semi-volatile analyte characterization.  
  • Non-volatile polar analytes are handled by UPLC/PDA-UV/qTof MS analysis.
  • GC and LC chromatographic and detector conditions are optimized for the extract solvent and anticipated residual components.
  • The qTof mass spectrometer provides analyte molecular ion and fragment ion accurate mass data (<5ppm) which are often sufficient for complete chemical characterization of even low intensity, i.e. ppm level, peaks.  Accurate ion masses can provide a short list of possible chemical formulas for low molecular weight analytes. Additional mass spectral information can lead to further refinement of the analyte structure is often possible.
  • Chemical characterization is enhanced by the UPLC/PDA-UV/qTof MS tandem detector setup which provides complementary PDA-UV spectral data and mass spectral data for detected analytes.
  • Gel permeation chromatography (GPC) can further characterize oligomeric/polymeric extractants through molecular weight distribution (MWD) analysis.

STUDY STANDARDS AND ON-THE-FLY METHOD VALIDATION

Suitable study standards are selected based on the material composition of the biomedical device components.  Often, monomers, solvents and additives used in device plastic components are selected.  Processing aids such as surfactants, cleaners, and solvents are also good study standard candidates.  Establishing method detection limits and response linearity for each of the study standards constitutes “on-the-fly” method validation which demonstrates the suitability, specificity, and sensitivity of the analytical methods for the analysis of study extract or leachate. 

DATA ANALYSIS, QUANTIFICATION AND REPORTING

Data analysis includes interpretation of the collective data set and critical evaluation of its validity. An objective of this phase is to determine whether the analytical data are self-consistent.  Mass Spec Lab acquires authentic standards of identified analytes for qualitative verification and quantification of extract concentrations.  Standard study reports submitted to our clients provide a comprehensive compiled data package with sample description, full disclosure of extraction and analytical test methods and validation data, reduced data in support of qualitative and quantitative characterization of the residual fraction, and a summary of results for clarity.