A llquld chromatographic system, capable of selectlvely detecting individual phenolic compounds at 1-ppb levels in water, is described. A polymeric-cation-exchange resin column, acidic acetonitrile-water eluent, and an electrochemical detector containing a unique carbon-black/polyethylene tubular anode are employed. Various types of carbon electrodes have been evaluated, as well as elution order and detector sensitivities for numerous phenolic compounds. Applications of the system to water analyses are presented.Phenolic compounds, especially halogenated ones, are of concern in the environment because of their toxicity to fish and other aquatic life and their adverse affect on water and fish taste ( I ) . Colorimetric analysis with 4-aminoantipyrene usually is employed to measure total phenols (2). However, most para-substituted phenols will not respond adequately, and no information concerning identity is obtained. T o identify and quantitatively measure total phenols a t ppb levels, procedures generally involve solvent extraction and either extensive solvent concentration followed by gas chromatography/mass spectrometry (GC/MS) or selective derivatization and GC with electron capture detection ( 3 ) . Disadvantages of the GC methods are sample preparation time, cost of MS equipment, incomplete recoveries for most phenols, and the lack of detector selectivity when only phenols are desired.A variety of liquid chromatographic (LC) columns have been used to separate mixtures of phenols in water samples (4-8). A major consideration when choosing a column for waste stream analysis is long term stability. Experience in our laboratories (9, IO) and studies by Walton et al. (11,12) have shown that good chromatographic resolution can be obtained with styrene-divinylbenzene base cation-exchange resins. Also these resins are totally unaffected by repeated injections of strong acids, bases, or concentrated brine solutions. If necessary, the columns can be emptied, cleaned, and refilled easily.Electrochemical detection of phenols after LC separation was demonstrated in 1973 by Takata and Muto (7). Since then, numerous publications describing electrochemical cell constructions and applications have appeared in the literature and were reviewed by Kissinger through December 1977 (13-15). Until recently, the material of choice for oxidative working electrodes was carbon paste. It is inert, easily replaced when fouled, and yields a low and stable residual current. However, it is unsuitable for LC eluents containing appreciable methanol or acetonitrile because the organic binder of the paste dissolves. Thus, a more universally applicable anode material is required.Glassy carbon is presently the alternative anode material of choice. It performs well in an electrochemical detector once the surface has been rigorously polished (16). In our experience, the electrode will become passivated during wastewater analysis and provision must be made for renewing the surface when this occurs.We were searching for an anode material that possess...

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The title compounds are on the EPA priority pollutant list. Therefore, a sensitive method for their measurement is required. The liquid chromatographic method employs a LiChrosorb RP-2 column, 45% acetonitrile (pH 5) mobile phase, UV detection at 280 nm, and electrochemical detection at +0.70 volts applied potential. The three-electrode electrochemical cell described contains a tubular carbon-black/polyethylene working electrode that permits detection of sub-part-per-billion levels in a 50 microliter injection permits detection of 2 ppb benzidine and dichlorobenzidine. Recoveries from fortified wastewater of benzidine at 1 to 6 ppb and dichlorobenzidine at 3 to 12 ppb levels were 83% and 87%, respectively.

The analysis of multi-phase pharmaceuticals, particularly when similar structures are involved (i.e. polymorphs, salts or hydrates), can often be a difficult task. Historically, x-ray powder diffraction (XRD) and differential scanning calorimetry (DSC) have been utilized to study pharmaceutical samples. Relative to other materials, diffraction data for pharmaceuticals are often complex due to the large number of diffraction maxima caused by the size of the molecule and/or the molecular symmetry. Multi-phase mixtures tend to have a large number of overlapping peaks which can hinder the difftactionist's ability to identify phases and interpret the data. When similar structures are analyzed calorimetrically, their thermal events may severely overlap (as will be shown), preventing accurate interpretation of the data. In addition there are several types of thermal events which may not be related to structural transitions. A common one in pharmaceuticals is the loss of solvent or absorbed (versus molecular) water.

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