6. AOACSPIFANMethods-2018Awards

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1124  Joseph et al. : J ournal of AOAC I nternational Vol. 98, No. 3, 2015

high standard required in mL; V 2 solution in mL. ( 2 )  Internal standard .— 13 C 2 D 2 fluoroacetic acid standard (50 mg/L) .—Dilute 2.5 mL (calculate exact volume based on concentration of secondary standard using Equation 2) of 13 C 2 D 2 fluoroacetic acid secondary standard (500 mg/L) to 25 mL with water in a calibrated volumetric flask. Use a calibrated positive displacement pipet. Dispense aliquots of the standard into 15 mL polypropylene tubes. Store in the freezer at –10°C or below. ( d )  Working solutions (WS) .—( 1 )  Analyte .—( a )  WS1 (1.0 mg/L) .—Dilute 1000 µL fluoroacetic acid intermediate standard (50 mg/L) to 50 mLwith deionized water in a calibrated volumetric flask. Dispense aliquots of the WS1 standard into 15 mL polypropylene tubes. Store in the freezer at –10°C or below. A thawed and opened tube WS1 can be stored for up to 2 months in a refrigerator between 2–8°C provided it is resealed and immediately refrigerated after each use. ( b )  WS2 (0.1 mg/L) .—Dilute 10 mL of WS1 (1.0 mg/L) to 100 mL with deionized water in a calibrated volumetric flask. Dispense aliquots of the WS2 standard into 15 mL polypropylene tubes. Store in the freezer at –10°C or below. A thawed and opened tube WS2 can be stored for up to 2 months in a refrigerator between 2–8°C provided it is resealed and immediately refrigerated after each use. ( c )  WS3 (0.01 mg/L) .—Dilute 500 µL of WS2 (0.1 mg/L) to 5 mL with deionized water in a calibrated volumetric flask. Transfer into a 15 mL polypropylene tube. Make fresh daily. ( 2 )  Internal standard .— Internal standard working solution (ISWS; 0.5 mg/L) .—Dilute 1000 µL of 13 C 2 D 2 fluoroacetic acid intermediate standard (50 mg/L) to 100 mLwith deionized water in a calibrated volumetric flask. Pipet aliquots of the ISWS into 15 mL polypropylene tubes. Store in the freezer at –10°C or below. A thawed and opened tube of ISWS can be stored for up to 2 months in a refrigerator between 2–8°C provided it is resealed and immediately refrigerated after each use. Table 2015.02D. Instrument parameters for AB Sciex LC-MS/MS system Parameter Value HPLC column Agilent XDB-C18, 100 × 4.6 mm × 1.8 µm Column temperature 60°C Autosampler temperature 10°C Flow rate 1 mL/min Injection volume 5 µL Run time 4 min Ionization mode Electrospray Polarity Negative Curtain gas (CUR) 30 psi Source temp. (TEM) 750°C Ion source gas 1 (GS1) 60 psi Ion source gas 2 (GS2) 60 psi Ion spray voltage (IS) –4500 V Collision gas (CAD) Medium (8) Entrance potential (EP) –10 V = total volume of diluted

Table 2015.02C. HPLC solvent gradient

% A (10 mM NH 4

% B

Time

Ac in H 2

O)

(10 mM NH 4

Ac in 97% ACN)

0

80

20

2.50 3.00 3.01 4.00

0 0

100 100

80 80

20 20

D. Standards ( a )  Primary standards .—Primary standards are stored in a refrigerator between 2–8°C in the dark. Subsequent solutions should be corrected for purity, moisture, and salt (if applicable). Wear appropriate PPE when weighing out the primary material. ( 1 )  Analytes .—Sodium fluoroacetate (CAS No. 62-74-8). ( 2 )  Internal standard .— 13 C 2 D 2 sodium fluoroacetate. ( b )  Secondary standards .—( 1 )  Analytes .— Fluoroacetic acid (1000 mg/L) .—Weigh approximately 12.9 mg sodium fluoroacetate into a calibrated 10 mL volumetric flask. Add deionized water, make to volume, and mix until solid is completely dissolved. Transfer to a 15 mL polypropylene screw cap test tube and cap tightly. Store in a freezer at less than –10°C. Calculate exact concentration correcting for purity, moisture (if applicable), and salt using Equation 1. C = [( m × P × Mo )/ V ] × [ MW / MW (salt) ] (1) where C = concentration of standard solution in mg/L; m = exact mass of primary standard weighed in mg; P = purity of standard expressed as a decimal equal to % purity/100; Mo = additional purity correction for moisture/water (if applicable). Expressed as a decimal equal to (100 – % moisture)/100; V = volume of solution in L; MW = molecular weight of target analyte; MW (salt) = molecular weight of analyte as salt. ( 2 )  Internal standard .— 13 C 2 D 2 fluoroacetic acid (500 mg/L) .—Weigh approximately 7.2 mg (corrected for chemical and isotopic purity) of 13 C 2 D 2 labeled sodium fluoroacetate into a calibrated 10 mL volumetric flask. Add deionized water, make to volume, and mix until solid is completely dissolved. Transfer to a 15 mL polypropylene screw cap test tube and cap tightly. Store in the freezer at –10°C or below. Calculate exact concentration correcting for purity, moisture (if applicable), and salt using Equation 1. ( c )  Intermediate standards.— ( 1 )  Analyte .— Fluoroacetatic acid intermediate standard (50 mg/L) .—Dilute 2.5mL(calculate exact volume based on concentration of secondary standard using Equation 2) of fluoroacetic acid secondary standard (1000 mg/L) to 50 mL with deionized water in a calibrated volumetric flask. Use a calibrated positive displacement pipet. Dispense aliquots of the standard into 15 mL polypropylene tubes for frozen storage. Store in the freezer at –10°C or below. C 2 = ( C 1 × V 1 )/ V 2 (2) where C 2 = concentration of required diluted solution in mg/L; C 1 = concentration of high standard in mg/L; V 1 = volume of