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Preface THE RENAISSANCE IN PARTICLE SIZE DISTRIBUTION ANALYSIS was discussed in the preface for Particle Size Distribution, written on November 5, 1985,fromthree perspectives: 1. commercialization of instrumental methods used previously in a few academic and industrial laboratories by skilled individuals, 2. revitalization of older instrumental methods, and 3. evolution of research-grade instrumentation into low-cost equipment that requires a minimum of skill to use. A fourth perspective can be added: 4. instrumental methods that fail in the marketplace. Hydrodynamic chromatography (HDC) was invented by Hamish Small in an industrial laboratory andfirstreported in 1976. The technology was licensed to an instrument company for commercialization. Five years ago HDC was in the process of trying to gain a foothold in the marketplace. In 1991, HDC is not a viable commercial instrument. It failed in the marketplace, primarily because the separation mechanism, which required fractionation and separation of particles in a packed column, had a flaw that was not fully overcome: During thefractionationprocess some of the particles being separated would deposit on the column packing. Recovery of the injected sample was less than 100%. The basic concept of HDC was a good one. Since 1986, a new chromatographic technique for particle size distribution analysis, capillary hydrodynamicfractionation(CHDF), has become a commercial reality. In this technique, separation andfractionationof
