Columns Shorter and Narrower Packed with Small Particles

1 COLUMNS SHORTER AND NARROWER PACKED WITH SMALL PARTICLES 

FIPLC columns packed with high-purity, silica-based bonded phases continue to dominate the market. Modern columns yield more symmetric peaks for basic analytes (less silanophilic activity) and have better batch-to-batch reproducibility and longer lifetimes. Improved bonding chemistries have widened the usable pFI range from 2-8 to 1.5-10 or more. Although C8- and CIS-bonded phases remain the most common, other phases have become quite popular, including phenyl, cyano, and several polar-embedded phases (e.g., amide, carbamate). 

Modem pumps have higher reliability (longer seal life) and precision at lower flow rates ( 0.2mL/min) brought forth by innovations such as the dual pistons in series design, variable stroke mechanism, micro pistons, and better check valves. Low-pressure mixing quaternary pumps have become standard equipment in research laboratories for method development, while high-pressure 

The dual-beam variable wavelength I JV/Vis absorbance detector remains the primary detector for routine analysis. Sensitivity and linearity performance have improved significantly in recent years. Noise specifications of 0.25 x 1(L5 AU and linearity of upper limit exceeding 2 AU are achievable with newer models. Typical spectral bandwidth ranges from 5 to 8nm. The lifetime of the deuterium lamp has improved to 1,000-2,000 hours. Most detectors have features such as self-aligned sources and flow cells, leak sensors, and built-in holmium oxide filters for easy wavelength accuracy verification. Many have dual- or multiple-wavelength and ratio plot output capabilities. 

Mass spectrometry with its excellent sensitivity and specificity is emerging as a premier analytical technique. Two common LC/MS interfaces are elec- 

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