Nutrient analysed

Key Foods Setting Priorities for Nutrient Analyses, J Food Comp Anal 9 331-364 see also http //www.nal.usda.gov/fnic/foodcomp/Bulletins/keyfoods.htm. 

Table 5.31. Examples of accepted analytical variation in nutrient analyses of feeds. (From AAFCO, 2005.)...

Tropical storms, typhoons, or hurricanes, depending on their strength and geographical context, often deliver torrential rains. Increased river flow during such high intensity, low frequency rainfall events can transport a major portion of annual river N load to coastal systems. Historically, there has been a paucity of data on such events due to their irregular and extreme nature and the generally manual nature of water sample collection for nutrient analyses. However, with the use of in situ automatic water samplers and nutrient analysis systems, data from such events can now more readily be captured. 

In general, nutrient analyses are done either manually or using an autoanalyzer. Space limits preclude the presentation of detailed protocols. An excellent general review of nutrient analysis as well as detailed method descriptions and protocols can be found in Grasshoff et al. (1999) and Sparks et al. (1996). 

TTHE BENEFITS OF AUTOMATING NUTRIENT ANALYSES IN SEAWATER have been recognized and utilized for several decades. Automated analyses allow samples to be processed faster and generally with better precision and accuracy than is possible with most manual methods. The only technique that was available at a reasonable cost for the automated analysis of seawater nutrients, until recently, was segmented continuous-flow analysis (CFA). Segmented CFA is characterized by the use of air bubbles to segment the liquid in the reaction tube so that dispersion of the sample is limited. 

U.se of the Technicon AutoAnalyzer in Seawater Nutrient Analyses Ref. No. 71-72, Oregon State Uniy. Corvallis, Oreg., 1971 49 pp. 

The flow rate of the system was about 4 L/min, and the time for passage of a sample from the inlet to the point of sampling was about 4 min. The pump was lowered at a rate of 6-10 m/min, and data were acquired every 3 s, and this system gave a sampling rate of two or three data points per meter. Features in the water column can be resolved on a scale better than 2 m. Nutrient analyses were made by using a computer-controlled rapid-flow analysis (RFA, Alpkem) system. Lag times were updated frequently by holding the pump head and CTD at a specific depth for several minutes. 

Cyherska (1990). Trzosinska and Zhuravleva (1975). "Uncertainty data for nutrient analyses refer to the colorimetric manual methods evaluation between 1999-2004. Grasshoff (1976). Grasshoff et al. (1983. 1999). "Morris and Riley (1963). Koroleff (1970). Valderrama (1981). Murphy and Riley (1962). 

Until the development of the conductivity method for salinity determination considerable time and effort had to be expended in ensuring the precision and accuracy of the salinity titration until the automatic analyzers, and more recently, the microchip controllers, nutrient analyses, even if actually performed by biologists or biological technicians, were often under the watchful eye of the resident chemist. 

To avoid the potential problems of filtration, centrifugation immediately after sampling might be advantageous. Kerouel and Aminot (1987), for example, proposed a device whereby the subsample for nutrient analyses from the rosette sampler is collected in a polypropylene bottle and, without further handling, is centrifuged and injected directly into the... 

Commercial nutrient analysers as well as standardized components for laboratory-designed analyser setups are available from various manufacturers and dealers of laboratory equipment. 

All nutrient analyses in this book are performed by spectrophotometry, a well established analytical method which does not require repetition here. However, it is important to remember some of the particulars of the method and some implications of Beer-Lambert s law, which is the basis of spectrophotometric determinations. 

Subsamples for automated analysis should be taken directly from the water samplers into subsample bottles of the desired volumes, which can be acconunodated by the autosampling device of the nutrient analyser. 

As a matrix for standards and blanks in nutrient analyses three properties of an artificial seawater are important, as they may affect the analytical result ... 

The large amount of data produced by an automated analytical system has to be processed by an on-line computer. Owing to the miniaturization of analytical and electronic components multi-channel nutrient analysers may be designed as rather compact and handy units, even fit to be used on small vessels. However, they are very complex and by no means switch on-measure-switch off machines. Well trained personnel, skilled in analytical chemistry, mechanics and data processing, and a great deal of experience is required to reliably operate nutrient analysers. Automated analysis is most profitable in every day routine measurements of large sample numbers. A few occasional nutrient samples, however, are better analysed by manual methods. 

The critical task for any nutrient analyser software is the determination of the peak height representing the component concentration. The peak shape depends on the sample volume and the mixing in the manifold. 

Infant formula products and other nutritional formulas directed to the needs of hospital patients provide a multibillion dollar annual market for several manufacturers. These liquid formulas are complex suspensions of nutrients, the levels of which are carefully controlled. Regulation of these products, especially infant formulas, dictates the need for a complex array of nutrient analyses. 

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