Tag Archives: acid-base

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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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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Extraction and Analysis of Gingko Leaves

You may know that there is a growing interest in the ginkgo tree because herbal supplements using extracts of ginkgo are believed to aid in fighting memory loss.  A recent paper [Lang, G.; Wai, C. M. Anal. Chem. 1999, 71, … 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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Solubility of Milk of Magnesia

Milk of Magnesia, or MOM, is a suspension of Mg(OH)2.  One method for determining the amount of Mg(OH)2 in MOM is to precipitate the Mg2+ as MgNH4PO4.  Because this precipitate includes a weak acid, NH4+, and a weak base, PO43-, … Continue reading

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