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nitrate. If fresh silver nitrate is not able to gain an acceptable range, replace the electrolyte of the electrode and check the condition of the dosing unit. G. Analysis Titrate the prepared sample solution on the titrator. Place the washing solution in special washing position of the auto sampler, and use fresh washing solution every 10 or 11 single titration tests. The sample titration conditions are the same as the system suitability analysis in Table 2015.07 . H. Calculations Calculate silver nitrate concentration (SNC) in moles per liter for system suitability verification and report to four decimal places: where m 1 = weight in milligrams of sodium chloride used to prepare the standard solution, m 3 = total weight in milligrams of prepared NaCl SS, V 1  = silver nitrate consumption volume in milliliters up to titration end point, 5.844 = sodium chloride weight in micrograms corresponding to 1 mL of 0.1 mol/L silver nitrate, and 10 = mass conversion from titer to the concentration of titrant. Calculate chloride content in sample (CL) and report to three significant digits: CL (mg/100g) = 35.5× × 2 × ×100 4 where m 4 = sample weight in grams, c = certified concentration in moles per liter of silver nitrate titrant, V 2 = silver nitrate consumption volume in milliliters up to titration end point, f = dilution factor, 35.5 = chloride weight in micrograms corresponding to 1 mL of = weight in milligrams of NaCl SS, m 2 SNC (mol/L) = 1 5.844 × 2 3 × 1 1 × 1 10

1 mol/L silver nitrate, and 100 = mass conversion to milligrams per 100 g. See refs. 1–3 for more detail. References: (1) GB 5413.24-2010, National Food Safety

Standard Determination of Chlorine in Foods for Infants and Young Children, Milk and Milk Products, http://www.moh.gov.cn/zwgkzt/psp/201005/47460. shtml (2) GB/T 6682-2008, Water for Analytical Laboratory Use—Specification and Test Methods, http://www.sac.gov.cn/SACSearch/ search?channelid=97779&templet=gjcx jg_detail.jsp&searchword=STANDARD_ CODE=%27GB/T%206682-2008%27&XZ=T (3) GB/T 601-2002, Chemical Reagent— Preparations of Standard Volumetric Solutions, http://www.sac.gov.cn/SACSearch/search? channelid=97779&templet=gjcxjg_detail. jsp&searchword=STANDARD_CODE=%27GB/T% 20601-2002%27&XZ=T J. AOAC Int . 99 , 198(2016) DOI: 10.5740/jaoacint.15-0143 AOAC SMPR 2014.015 J. AOAC Int . 98 , 1079(2015) DOI: 10.5740/jaoac.int.SMPR2014.015

Posted: February 19, 2016

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