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United States Department of Agriculture

Agricultural Research Service

Title: Determination of Niacin in Infant Formula by Solid Phase Extraction and Anion Exchange Liquid Chromatography Pvm

Authors
item Lacroix, Denis
item Wolf, Wayne

Submitted to: Association of Official Analytical Chemists Peer Verified Method
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 31, 2000
Publication Date: March 30, 2001
Citation: Lacroix, D.E., Wolf, W.R. 2001. Determination of niacin in infant formula by solid phase extraction and anion exchange liquid chromatography- pvm. Association of Official Analytical Chemists Peer Verified Method. J. AOAC International 84(3) 789-804.

Interpretive Summary: A peer-verified, solid-phase extraction/anion exchange liquid chro- matograph (LC) method for the determination of niacin in milk-based and soy-based infant formula is presented. Sample digestion utilizes a standard AOAC digestion procedure that involves autoclaving in H2SO4 to free endogenous niacin from protein and to convert added niacinamide to niacin. Solid-phase extraction (spe) of niacin is accomplished by passing an aliquot of the digest solution over an Aromatic Sulfonic Acid-spe (ArSCX-spe) column and eluting with NaAc/HOAc buffer. LC separation is accomplished using an anion-exchange polystyrene-divinylbenzene column with a NaAc/HOAc buffer and detected by absorption at 260-nm wavelength. The following mean and rsd values were obtained for the NIST SRM 1846-Infant Formula with a certified value for niacin of 63.3 +/-7.6 ug/g. Submitting laboratory: 59.7 +/- 4.0 ug/g => 6.7 % rsd, n = 27. Collaborating laboratory: 56.6 +/- 6.6 ug/g =>11.7 % rsd; n = 10. This method will be included as an AOAC Peer Validated Method for use by government and private sector food testing and analysis laboratories in place of the presently laborious AOAC Official Method of Analysis for niacin, which is a microbiological method.

Technical Abstract: A peer-verified, solid-phase extraction/anion exchange LC method for determination of niacin in milk-based and soy-based infant formula is presented. Sample digestion utilizes a standard AOAC digestion procedure that involves autoclaving 121 degree C for 45 min in (1+1) h2so4 to free endogenous niacin from protein and to convert added niacinamide to niacin. Adjusting the digest solution to pH 6.5 with 7.5 N NaOH and acidification to pH <1.0 with (1+1) H2SO4 precipitates protein. Solid-phase extraction (spe) of niacin is accomplished by passing an aliquot of the digest solution over an Aromatic Sulfonic Acid-spe (ArSCX-spc) column. After washing the column with methanol and demineralized water to remove extraneous materials, the niacin is eluted using 0.25 M NaAc/HOAc buffer at pH=5.6. LC separation is accomplished using an anion-exchange polystyrene-divinylbenzene column with a 0.1 M NaAc/HOAc buffer at pH=4.0. Niacin is deleted by UV detection at 260-nm wavelength. A standard curve is prepared by passing known amounts of niacin over the ArSCX-spc columns used for niacin extraction. The following mean and rsd values were obtained for the NISR SRM 1846-Infant Formula with a certified value for niacin of 63.3 +/-7.6 ug/g. Submitting laboratory: 59.7 +/-7.6 ug/g => 6.7 % rsd, n = 27. Collaborating laboratory: 56.6 +/- 6.6 ug/g =>11.7 % rsd; n = 10.

Last Modified: 12/24/2014
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