Brian D. Warner

Construction and evaluation of a sensitive, inexpensive pH stat/titrator system

Abstract A sensitive, inexpensively constructed pH stat-autotitrator is described. In the pH stat mode of operation a digitally controlled buret adds titrant to a reaction mixture at a rate proportional to the differences between the solution pH and the stat pH. The digital buret employs inexpensive Hamilton glass syringes (250 μl → 2.5 ml) to deliver titrant at rates ranging from ∼ 100 nl/min to ∼ 1.5 ml/min. Both the volume of titrant and the pH are displayed digitally and are available as an analog signal for use by an external chart recorder. An equation relating reaction parameters (reaction volume, titrant normality, buffer capacity, and kinetic constants) to tracking accuracy is derived. The predictions of the derived relationship are of general importance to all p X -based kinetic analyses.

Construction and evaluation of a programmable gradient liquid chromatograph

Abstract A programmable gradient synthesizer has been constructed which is capable of forming flow-programs and gradients (linear and non-linear) of variable duration. The synthesizer is constructed from simple digital integrated circuits and is interfaced to an inexpensive two-channel high-pressure reciprocating pump. Other components necessary to complete the chromatograph are specified to provide high performance and flexibility at moderate cost. The application of the system to the analytical and preparative separation of some azodye reaction mixtures is presented. A new procedure for reproducible sample application in preparative liquid chromatography, employing flow-programming, is introduced.