Detectors in superheated water chromatography

Superheated water also offers some novel advantages in detection because the absence of an organic solvent reduces low-wavelength spectroscopic absorption, eliminates the solvent peaks from NMR spectra, and eliminates the solvent signal from flame detectors. This has enabled a wide range of unique HPLC detection methods to be employed. 

UV and fluorescent spectroscopy can be employed down to 190 nm because there is no solvent interference. Mass spectrometry is easy because the water provides good ionization. Flame ionization detection (FID) is of particular interest because potentially it offers a sensitive and universal detector. A number of different interfaces have been used, including heated capillaries, which have been examined by Miller and Hawthorne [62], Ingelse et al. [63], and others [64, 65], who separated a range of analytes including alcohols, amino acids, and phenols. An alternative method employing a cold nebuliza-tion of the eluent has been introduced by Bone et al. [66]. They were able to detect both aliphatic and aromatic alcohols, polymers, carbohydrates, parabens, and steroids. 

One attraction of SHW is that it can be used for reversed-phase separations and is therefore readily applicable to a wide range of pharmaceutical compounds including barbiturates, sulfonamides, analgesics and steroids (Table 18-2), and anticancer drugs, including 5-fluorouracil, methotrexate, and 

TABLE 18-2. Pharmaceutical Compounds Separated Using Hot and Superheated Water 

Analyte Mobile Phase Column Temperature Reference 

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