AOAC-RI ERP Book - FAOM METHOD.pdf

AOAC RESEARCH INSTITUTE AOAC OFFICIAL METHODS OF ANALYSIS (OMA) OMAMAN-15 : Determination Of Polycyclic Aromatic Hydrocarbons (PAHs) In Seafood Using Gas Chromatography-Mass Spectrometry: A Collaborative Study* Study Director: Katerina Mastovska, Covance Laboratories Inc., Nutritional Chemistry and Food safety, 3301 Kinsman Boulevard, Madison, WI 53704, USA ER 1 The organizer took great effort setting up the procedures to allow for individual lab's choice of various instruments, columns, SPE vendors, and evaporation techniques, as long as the lab passed the performance requirements. The procedures are straight forward and not hard to follow. ER 2 Fairly easy method that requires significantly less sample preparation compared to other methods. Utilizes equipment and instrumentation that is widely available. Uses less flammable and toxic solvents than other methods. Sample handling is minimized which decreases the probability of environmental contamination. ER 3 Strengths include: 1. easy to follow criteria for sample preparation evaluation 2. easy to follow instructions for solution and calibration solution preparation 3. some allowance for environmental background of the naphthalene 4. importance of monitoring blank is clearly stated ER 4 The method is simple, fast, accurate, robust and is easy to follow. ER 5 Well written, encompasses analyses of PAH compounds deleterious to humans at low levels, the calculations outlines on pages 14-15 are well written. ER 6 A major strength is that the method is an isotope dilution (ID) GC-MS methods using C13 labeled internal standards for 13 of the 19 target PAHs. The sample preparation appears to be simplified compared to normal solvent extraction methods (Soxhlet, ACE, MAE). Another strength is the performance criteria required for the choice of GC column and the requirements to separate critical PAH isomers such as the benzofluoranthenes. ER 7 The method is simple, fast, and easy to use. High sample throughput with little lab ware needed. Applicable to a variety of seafood matrices. Overall method performance are acceptable. ER 8 no comment ER 1 Isotope-Labeled mixed standards may be expensive or could be unavailable occasionally. Precision of results (all three levels) may have some room for improvement. ER 2 Still requires some sample clean up, including a dry down step which if performed incorrectly could cause artificially low calculated concentrations for low molecular weight PAHs. Does not incorporate many alkyl homolog PAH compounds. These are often present at higher concentration in oil contamination and have similar toxicity to the PAHs. Addition of these compounds to the GC-MS method would increase the applicability and impact of the method. This could perhaps be done in the future ER 3 Weaknesses include: 1. Method scope of 1 ug/kg LOQ of BaP was not tested as a fortification level. As I read the method, the lowest fortification level for BaP was 2 ug/kg. 2. Polypropylene tubes used for extraction will likely cause users of the method issues with PAH contamination. Discussion of alternatives would be helpful. 3. PAH GC-MS analysis has significant differences than typical analysis of most other types of compounds. Guidance for GC-MS parameters would likely be helpful for users of the method. These include parameters like inlet temperature, transfer line temperature, ion source temperature, column loadability and efficient flow conditions. 4. There is no recommendation on how to report data on chrysene and triphenylene if the recommended, but not required, 50% valley separation is not met. Can chrysene and triphenylene be reported together? 5. Ion ratios are mentioned as a requirement for identification but there is no indication as to the RSD value that is acceptable or some other qualification. 6. When a linear calibration curve is not possible, allowance for a "well- characterized" quadratic formula is made but with no discussion of what "well-characterized" means. Some guidance would be useful because some user will not be accustomed using quadratic calibration curves. ER 4 A commercially available mix of standards suitable for the method is beneficial. ER 5 The Safety Section must be in the front of the method since safety is more important than any other part of the protocol. Method must be more specific. Under Degradation Issues on page 18, the discussion emphasizes the need for a Stability Study. 18.2 megaohm water should be used for any GC/MS method (page 9, Section C). Need a statement that documented calibrations/reference checks were performed on all analytical equipment and instrumentation used in the collaborative study. ER 6 A major weakness is that there is no validation using a certified reference materials for PAHs in seafood. Standard Reference Material (SRM) 1974b Mussel Tissue is mentioned as part of the qualification of the labs (p. 6) as a practice sample, but no data are reported using SRM 1974b for validation of the proposed method. The availability of SRM 1974c (which has replaced SRM 1974b) provided an excellent opportunity to use a CRM to validate an AOAC method. The use of only fortified/spiked samples for the method validation is a weakness. Spiked samples are sometimes the only option but in this Pros/Strengths Cons/Weaknesses