Tag Archives: method development

HPLC Separation of Phenacetin, Salicylic Acid, Nicotine, Methylamphetamine, and Phenobarbatuic Acid

The graph shown below is a plot of retention time vs. pH for the reverse-phase HPLC separation of a mixture containing phenacetin, salicylic acid, nicotine, methylamphetamine, and phenobarbituic acid. Based on the structures of these compounds and their pKa values, … Continue reading

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Analysis of Anaerobic Sediments for Sulfides

A paper in the Journal of Chemical Education describes an experimental method for determining the concentrations of both insoluble metal sulfides, such as FeS2, and gaseous H2S in anaerobic sediments. Samples of sediment are placed in a flask along with … Continue reading

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Neocuproine Method: Analysis of Procedure

One method for determining copper is the “Neocuproine Method”. In this method, copper in a +1 oxidation state reacts with neocuproine (2,9-dimethyl-1,10-phenanthroline) to form a complex of Cu(neocuproine)2.  The complex is extracted into a chloroform-methanol mixture, giving a yellow solution … Continue reading

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Standards and Samples

The spectrophotometric methods for analyzing Mn and for analyzing glucose use a chemical reaction to produce a useful signal. In the analysis for Mn in steel, colorless Mn2+ is oxidized to give the purple MnO4– ion, while in the analysis for … Continue reading

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Gravimetric Method for Analysis of Phosphorous: Analysis of Procedure

Once upon a time, a common method for determining phosphorous was to convert it to phosphate, precipitate it as magnesium ammonium phosphate, MgNH4PO4, and ignite it to form magnesium pyrophosphate, Mg2P2O7.  The solubility reaction for MgNH4PO4 is MgNH4PO4(s) ↔ Mg2+(aq) … Continue reading

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Separating a Weakly Acidic Analyte from a Weakly Basic Interferent

Imagine  you have an aqueous sample containing a weak acid analyte, HA, and a weak base interferent, HI.  The following information about HA, HI, the method of analysis, and the sample are available to you: Ka,HA = 1.00 x 10-3 … Continue reading

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Selecting an Analytical Method

As part of the study of how humans age, there is an interest in learning how the chemical composition of tissues change as we grow older or as the result of disease. Suppose you are interested in determining the concentration … Continue reading

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