Instrumental Analysis, ChFE 5503Metals in a Juice-Type Drink(Rev. 1/27/04)Scope: This method describes the determination of Ca, Mg, Fe, K, Na, Snand Zn in fruit juices and similar drinks. The method may also beapplicable to other elements. Dry ashing or wet oxidation can be used toprepare the sample, however these methods are time consuming(sometimes requiring up to 2 days). The juice sample can be hydrolizedby a strong acid, which allows the preparation of many samples at onetime. The sample is acidified, filtered, washed, and made up to volumefor analysis by atomic absorption.TYPICAL ANALYTICAL PROCEDURESample Preparation: To 20 ml of juice in a 100 ml volumetric flask, add10 ml of concentrated HCl (37%) then make up to volume with deionizedwater. Note: always add acid to water and beware of excess heateven using that method. If solid particles are visible in the juice, filterthe sample ( using approximately 50 ml) prior to making up to 100 ml.Include all of the wash water in the final solution. Analysis: Dilution may be necessary for elements present in highconcentrations. Make dilutions so that the final solution contains 4-5%(v/v) HCl. The solution must also contain 0.5% La if calcium is beingdetermined. Prepare standards containing the same acid (and La)concentrations as the samples. Potassium standards should be madefrom KCl. Dissolve 1.907 g of potassium chloride in deionized water anddilute with deionized water to 1.00 liter in a volumetric flask. Betterresults for potassium may be realized if 0.1 % or more cesium or La isadded to the samples and standards.OTHER APPLICATIONSWine: The method above can also be used to determine metals in wines.Sodium and potassium can be determined by diluting the wine sample(the P.E. manual does not say how much dilution is required) andanalyzing using aqueous samples as described above. Cu and Zn may bedetermined by direct aspiration versus standards containing equalamounts of alcohol. (Note: a guess would be to dilute the wine 1:10 sothat the alcohol is about 1 %) Spirits: Copper and iron (plus some other elements) can be determinedin spirits, gin, whiskey, rum and similar beverages in the manner above.The samples are aspirated directly but some modifications in the flamemay be needed (e.g. lean, blue flame). Standards are made up in alcoholto match the contents of the particular sample.Beer: A method similar to the above can also be used to determine Na,K, Ca, Mg, Pb, Ni, Cu, Fe, and Zn in beer. Most elements are determineddirectly but if in high concentration, the sample can be diluted. Pb, Ni,and Fe may be very low which requires a solvent extraction procedure toconcentrate them. All beers must be decarbonated by shaking or rapidtransfer from beaker to beaker several times. Add 1-2 drops of octylalcohol to bottled beer to control foam if necessary. Standards shouldhave alcohol as mentioned in the wine and spirits analysis.Reference: AAnalytical Methods for Atomic Absorption Spectroscopy,@Perkin Elmer Instruments