If the measurement is delayed the next day, specimens should be stored at 5 ± 4 °C. If the analytical system fails, specimens and any partially-prepared / extracted samples can be stored at 5 ± 4 °C until the analytical system is again operational. Studies indicate THC is very stable when stored at varying temperatures, during freeze/thaw cycles, and in different matrices, which allows for repeat analysis. 3.5 Special equipment Blood specimens are collected from subjects in standard blood collection tubes. 4.0 Reagents or Media 4.1 Reagents and sources Reagents and sources used during the development and validation of this method are listed in Table 2. Specific part numbers and manufacturers are listed only as examples and other sources can be used for purchasing these reagents as long as the quality meets or exceeds the established standards listed in this SOP. All chemicals and solvents are used without further purification. All solid state reagents/standards are acceptable for use for 10 years from the date of open when stored as recommended by the manufacturer unless otherwise indicated through stability studies or by the manufacturer. All liquid state reagents and standards are acceptable for use for 1 year from the date of open when stored as recommended by the manufacturer unless otherwise indicated through stability studies or by the manufacturer. Table 2. Chemicals and sources Reagent Grade Source * Part Number Formic Acid Optima-LC/MS Fisher Scientific, Fairlawn, NJ A117-50 Type 1 Water Deionized 18 MΩ water Millipore n/a Ammonium Formate Optima-LC/MS Fisher Scientific, Fairlawn, NJ A115-50 Methanol Optima-LC/MS Fisher Scientific, Fairlawn, NJ A456-4 Methyl tert-butyl ether (MTBE) 99.9% Acros Organics, Fairlawn, NJ 378720025 Hexanes Optima Fisher Scientific, Fairlawn, NJ H303-4 Acetonitrile Optima-LC/MS Fisher Scientific, Fairlawn, NJ A955-4 * Or equivalent. 4.2 Reagent Preparation
At the time of preparation, all reagents should be labeled with name (or initials) of person preparing the solution, expiration date, and contents of solution. Reagents are prepared as needed. Records of all preparations are kept in the Reagent Preparation Spreadsheet and are noted in the laboratory notebook. Instructions listed in the following sections (4.2.1 – 4.2.5) are provided as example calculations and care should be taken to ensure final concentrations remain consistent. For example, stock concentrations of purchased materials may vary between vendors, and therefore, dilutions and final protocols have to be adjusted accordingly. All prepared reagents are stored at room temperature unless otherwise indicated. HPLC mobile phases 100% Water with 0.1% Formic Acid (Mobile Phase A): Spike 1 mL of formic acid into 1000 mL type-1 water. This solution is good for 1 month. 100% Acetonitrile with 0.1% Formic Acid (Mobile Phase B): Spike 1 mL of formic acid into 1000 mL acetonitrile. This solution is good for 1 month. 0.1% Aqueous Formic Acid Add 1000uL formic acid to 1000 mL type 1 water. This solution is good for 1 month. Needle Rinse Solution – 75% MeOH Add 750 mL MeOH to 250 mL type 1 This solution is good for 1 month. Native Standards The standards are pre-laced in wells of a 48-well plate and purchased from Cayman Chemical. The standards are stored at ≤ °C. Other equivalent standards may be purchased from another vendor, if necessary, and the plates can be made by hand. Isotopically labeled internal standards The labeled internal standards are pre-laced in wells of a 48-well plate and purchased from Cayman Chemical. The plates are stored at ≤ -20 °C. Other equivalent standards may be purchased from another vendor, if necessary, and the plates can be made by hand. QC Material QC Material are pre-laced and dried in wells of a 48-well plate and purchased from Cayman Chemical. The plates are stored at ≤ -20 °C. Other equivalent standards may be purchased from another vendor, if necessary, and the plates can be made by hand. 4.3 Preparation of Standards 20 -