6. AOACSPIFANMethods-2018Awards

265

Very Low Standard: Conc. in mg/L = 100 mg/L x 0.2/50mL Conc. Of Very Low std = 0.400 mg/L Low Standard: Conc. in mg/L = 100 mg/L x 1mL/50mL Conc. of Low Standard = 2.00 mg/L Mid Standard: Conc. in mg/L = 100 mg/L x 5mL/50mL Conc. of Mid Standard = 10.00 mg/L

High Standard: Conc. in mg/L = 100 mg/L x 10mL/50mL Conc. of High Standard = 20.00 mg/L

b) Internal Standard (where indicated) (1) The 5-Methyl-DL-tryptophan weight from E.3.d is used in the calculations as the internal standard (IS) amount. Conversion to concentration is unnecessary. (2) Note: The use of different internal standard solution preparations for the standards and samples is acceptable as long as the actual respective weights or concentrations are applied to standards and samples and the two solutions are prepared using the same lot of 5-methyl-tryptophan. c) Tryptophan Concentration in Samples

Volume

TRP g

= (CTS – CTB) x

x 100g

100 g Sample Sample Weight (g) 1000mg/g

Where: CTS = Concentration of Tryptophan in Sample CTB = Concentration of Tryptophan in Blank Volume = Final volume in Liters i.e. 50 mL = 0.05L

2. Sample Calculation The following example shows a typical calculation performed when only an integrator is used for sample quantitation. When a Chromatography Software is used, the software will perform the calculation shown below. Once the software processing method is properly calibrated and appropriate factors applied, the sample results will be computed in the desired units. If a data station is used to compute mg/L concentration results for the sample and blank, the equation listed in c) above will suffice for completing the g/100g calculations. With some chromatography software, such as Empower, the blank subtraction and gram/100g computation may also be executed within the software. Consult your software instruction manual.