AOAC SPIFAN Nutrients ERP (December 7, 2022)

Amino-07 (Method) 10-2022 FOR ERP USE ONLY DO NOT DISTRIBUTE

6.3 = final volume of CS1–5 (mL) (e) Concentration of 13 C 2 15 N 1 taurine in calibration standards ( CS1–5 ): CS1–5 Tconc = SILSS Tconc × 0.3 6.3 where: CS1–5 conc = concentration of 13 C 2 15 N 1 taurine in CS1–5 ( μ g mL − 1 ) SILSS conc = concentration of 13 C 2 15 N 1 taurine in SILSS ( units : μ g mL − 1 ) 0.3 = volume of SILSS in CS1–5 (mL) 6.3 = final volume of CS1–5 (mL) (f) Determine the linear regression curve y = m x + c (using the "least squares" method) for the ratio of peaks areas (non-labelled taurine/stable isotope labelled taurine) vs. the ratio of concentrations (non-labelled taurine/stable isotope labelled taurine for five calibration standards with the y -intercept forced through zero. (g) The concentration of taurine in the sample is calculated as: Result = PA NLT PA SILT × SILSS conc × SILSS alqt S mass × 1 1 0 0 0 0 0 where: Result Taurine = taurine concentration in sample (mg hg − 1 )

PA NLT = peak area of taurine in sample (no units) PA SILT = peak area of SIL taurine in sample (no units) SILSS conc = concentration of 13 C 2 15 N 1 taurine in SILSS ( μ g mL − 1 ) L = slope of calibration curve (no units) SILSS alqt = volume of SILSS aliquot spiked to sample (mL) [0.3 mL];

1000 = concentration conversion factor (µg g − 1 to mg g − 1 ) 100 = concentration conversion factor (mg g − 1 to mg hg − 1 ) S mass = mass of sample (g)

(h) Report result as mg hg − 1 to 1 decimal place.