AOAC SPIFAN Nutrients ERP Review (March 14, 2019)

Fluor-03 (Feb. 2019) FOR ERP USE ONLY DO NOT DISTRIBUTE

(b) Mobile phase B - carbonate concentrate for dose-in gradient (37.5 mM Na 2 CO 3 and 3.75 mM NaOH, 2000 mL.).— Dilute 7950 mg sodium carbonate salt (C.a) and 750 µL sodium hydroxide (C.b) to 2000 mL UPW (C.f) and mix well on a stir plate. (c) Suppressor regenerant solution (0.5 M H 2 SO 4 , 1000 mL.).— Take 1000 mL 0.5 M H 2 SO 4 and mix well. (d) UPW for liquid handling and sample transfer.— Prepare two bottles with 2 L UPW for sample transfer (1) and liquid handling (2). (e) MeOH rinsing solution.— Prepare 100 mL of 100% methanol for rinsing in an opaque bottle. E. Preparation of stock solutions, calibration and check standards, and spiked UPW/matrix for LOD (a) Fluoride stock solutions (10 mL, 50 mL, Table 1 ).— Dilute 5 and 0.5 mL fluoride CRM (1000 mg/L, (C.e) to 50 mL UPW (C.f) to achieve the 100 and 10 mg/kg stock solutions. For the 1000 mg/kg stock solution, take the undiluted 1000 mg/L F - CRM (C.e).

Table 1 Preparation of stock solutions Concentration (mg/kg) Conc. stock solution (mg/L)

Vol. stock solution (mL)

Vol. UPW (mL)

Total vol. (mL)

1000

1000 1000 1000

10.0

0

10.0 50.0 50.0

100

5.0 0.5

45.0 49.5

10

(b) Fluoride calibration standards (5-1500 µg/kg, 50 mL., see Table 2).— Dilute fluoride stock solutions of 10, 100, and 1000 mg/kg (see E.a and Table 1 ) to 50 mL UPW (C.f) to achieve the 9 standards in a concentration range of 5 to 1500 µg/kg F - . Mix well. To achieve a higher accuracy the standards can be assigned to either the low (5-100 µg/kg F - ) or the high calibration (100-1500 µg/kg F - ) and used for an automatic signal-based intelligent data evaluation.

Table 2 Preparation of calibration standards

Concen- tration (µg/kg)*

Conc. stock solution (mg/kg)

Stock solution (g)

Vol. stock solution (µL)

Vol. UPW (g)

Total (g)

Std no

1 2 3 4 5 6 7 8 9

5

10 10 10

0.025

25 50

49.975

50 50 50 50 50 50 50 50

10 25 50

0.05

49.95

0.125 0.025

125

49.875 49.975

100 100 100

25 50

100 250 500

0.05

49.95

0.125 0.025

125

49.875 49.975

1000 1000 1000

25 50 75

1000 1500

0.05

49.95

0.075 50 * The standard concentrations refer to an analytical range of 10-3000 µg/ 100 g final product (based on calculation for the F - in µg/kg for a 50 mL mix with 2.5 g sample) (c) Fluoride check standards (5, 10, 160, and 500 µg/kg, 250 mL, see Table 3).— Dilute fluoride stock solutions of 10 and 1000 mg/kg (see E.a and Table 1 ) to 250 mL UPW (C.f) to achieve the 4 check standards for quality control (QC). 49.925

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