The concentration of an analyte in solution will effect the wavelength absorption maximum for that compound. A anion exchange resin posses a negative charge. In gas chromatography, the detector is maintained several degrees cooler than the column temperature. A refractive index detector is susceptible to temperature effects from the atmosphere. Column temperature has only a minor effect on GLC separation.
Water activity is a good measure of the moisture content in foods.
Dry ashing is a good method for the more volatile elements. Gravimetric methods are an accurate means of determining the mineral contents of food samples. In gel filtration chromatography, the small compounds elute first. A 1 liter solution contains 2 moles of lactic acid and 1 mole of lactate ion. The pK of lactic acid is 3.86.