Nutrient standards, reference materials

Sharpless KE, Gill LM, Margolis SA, Wise SA, Elkins E (1999) Preparation of standard reference material 2383 (baby food composite) and use of an interlaboratory comparison exercise for value assignment of its nutrient concentrations. J AOAC Inti 82 276-287. 

KE Sharpless, SB Schiller, SA Margolis, J Brown-Thomas, GV Iyengar, JC Colbert, TE Gills, SA Wise, JT Tanner, WR Wolf. Certification of nutrients in standard reference material 1846 infant formula. J AOAC Int 80 611-621, 1997. 

Colorimetric methods for the determination of DIP, nitrate, nitrite, ammonium, and silicate are well established, with both manual and automatic procedures well understood and able to provide adequate sensitivity for most purposes. These methods can readily be used at sea and in the future probably in situ. International intercalibration exercises have shown that many laboratories now have the analytical expertise to measure nutrient concentrations at ambient levels, but this is not true of all laboratories and the analysis still requires careful analytical procedures that recognize the importance of contamination control, blank correction, and the complications arising from the saltwater matrix. Although there have been a number of such intercalibration studies, there is no widely available standard reference material for nutrient analysis at present. 

LIBS was applied to quantify nutrients (Mg, Ca, Na, and K) in spinach and rice and to discriminate pesticide-contaminated products rapidly. Standard reference materials (spinach leaves and unpolished rice flour) were used to establish a relationship between LIBS intensity and the concentration of... 

Stoepplbr M and Zeisler R, eds. (1993) Biological environmental specimen banking. A collection of papers presented at the ist International Symposium on Biological Environmental Specimen Banking. Vienna, Austria, 22-25 September 1991. Sci Total Environ, Vols. 139 and 140. Tanner JT (1984) The FDA-IFC infant formula methods study and standards for organic nutrients. In Wolf WR, ed. Biological Reference Materials, pp 197-205. John Wiley Sons. 

Seawater reference materials are recommended for nutrients and for trace metals (especially iron). There is an urgent need for a certified reference material for nutrients. Completed global surveys already suffer from the lack of previously available standards, and the success of future surveys as well as the development of instruments capable of remote time-series measurements will rest on the availability and use of good nutrient reference materials. The reference materials for trace metals— though initially characterized only for the important micronutrient, iron— should ultimately be useful for the analysis of the other metals and some dissolved organic materials. The committee also recommends the devel-... 

Since certified reference materials for seawater nutrient analysis are currently unavailable, individual laboratories must prepare their own standard solutions for instrument calibration. Standard stock solutions are prepared at high concentrations (mM) so that they can be used for months without significant alterations in concentration. Working low-concentration standard solutions are unstable and need to be prepared daily by diluting stock solutions with distilled water or low-nutrient seawater. In this case, the accuracy of nutrient analysis at a given laboratory is highly dependent upon the accuracy of the daily preparation of the calibration solutions. 

In the 1970s, the Sagami Chemical Research Center in Japan provided nutrient reference material for the Cooperative Study of the Kuroshio Current (the so-called CSK standards). These solutions were not prepared in seawater, which limits their general utility (see below), however they are still distributed and widely used as a common reference. French and British scientists have conducted some studies on nutrient reference material (Aminot and Keroul, 1991, 1996 Zhang et al., 1999) with limited success. 

There is an urgent need for a certified reference material for these nutrients. Completed global surveys already suffer from the lack of previously available standards, and the success of future surveys as well as the development of instruments capable of remote time-series measurements will rest on the availability and use of good nutrient reference materials. 

These sources included, among others, the U. S. Pharmacopoeia and the Merck Index. Thus, the common data base would contain compounds known to be of interest to people in the health field, including drugs, antibiotics, hazardous materials, pesticides, nutrients, and food additives as well as inert compounds in such substances. Chemical Abstracts Service processed these sources against its registry system and added registrations as well as synonyms as they were found in these standard references. The data were delivered to FDA and NLM in a form suitable for processing in their machine systems. 

Table 19.3 Results of niacin determinations for milk samples. Niacin determinations by liquid chromatography-isotope dilution mass spectrometry (LC-IDMS) are compared to expected values for four milk samples. Expected niacin levels for milk are roughly 1 ppm, according to the USDA Nutrient Database for Standard Reference (US Department of Agriculture 2010) and results obtained for two commercial milk samples (Brands F and G) are a little under 1 ppm. The result for sample NFY0409F6 is about 30% lower, but is consistent with results obtained for other milk samples from the same source. In addition, the niaein level for NFY0409F6 was estimated by a standard additions experiment, the result from which is in agreement with the estimate from the normal LC-IDMS procedure. The level obtained for the reference material (RM) RM 8435 whole milk powder, reported on a dry mass basis, is in agreement with the reference value. Data are from Goldschmidt and Wolf (2007), with permission from the publisher.

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