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ARS Home » Northeast Area » Beltsville, Maryland (BHNRC) » Beltsville Human Nutrition Research Center » Food Composition and Methods Development Laboratory » Research » Publications at this Location » Publication #105140
Title: DETERMINATION OF NIACIN IN INFANT FORMULA BY SOLID-PHASE EXTRACTION AND ANION-EXCHANGE LIQUID CHROMATOGRAPHY-PVM 1:2000.

Author
item Lacroix, Denis
item Wolf, Wayne

Submitted to: Journal of Association of Official Analytical Chemists International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/31/2000
Publication Date: 1/1/2001
Citation: Lacroix, D.E., Wolf, W.R. 2001. Determination of niacin in infant formula by solid-phase extraction and anion-exchange liquid chromatography-pvm 1:2000. 2001. Journal of Association of Official Analytical Chemists International. 84(3): 787-804.

Interpretive Summary: A solid-phase extraction/anion exchange liquid (LC) method for the determination of niacin in milk-based infant formula has been peer-verified by inter-laboratory collaborative study to meet defined Data Quality Objectives (DQO). Sample analysis is in four phases, sample digestion, detraction by extraction/cleanup and chromatographic LC separation and UV Vis absorption. 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 detection accomplished by UV 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. By integrating the DQO process with a readily available SRM, the user gains confidence in the accuracy of the resultant data. 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 Method for niacin, which is a microbiological method.

Technical Abstract: A solid-phase extraction/anion exchange LC method for the determination of niacin in milk-based infant formula has been peer-verified by inter-laboratory collaborative study to meet defined Data Quality Objectives (DQO). Sample analysis is in three phases, sample digestion, cleanup and liquid chromatographic (LC) analysis. Sample digestion utilizes a standard AOAC digestion procedure that involves autoclaving @121o 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- spe) column. After washing the column to remove extraneous material, the niacin is eluted using 0.25 M NaAc/HOAc buffer at pH=5.6. LC analysis is accomplished using an anion-exchange polystyrene-divinylbenzene column with a 0.1M NaAc/HOAc buffer at pH=4.0. Niacin is determined by UV detection at 260-nm wavelength. A standard curve is prepared by passing known amounts of niacin over the ArSCX-spe columns used for niacin extraction. 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.