The Use of a Milli-whistle as a Detector in Gas Analysis by Gas Chromatography

This minireview introduces a general understanding of the use of a milliwhistle as a gas chromatography (GC) detector in gas analysis, including our research on the methodology and theory associated with a number of different related applications. The milliwhistle is connected to the outlet of a GC capillary, and when the eluted gases and the GC carrier gas pass through it, a sound with a fundamental frequency is produced. The sound wave can be picked up by a microphone or an accelerometer, and after a fast Fourier transform, the online data obtained for frequencychange vs. retention time constitute a new method for detecting gases. The first part of this review discusses the fundamentals of the milliwhistle. Some modifications are also discussed, including various types of whistles and an attempt to maximize the sensitivity and stability of the method. The second part then focuses on several practical applications, including an analysis of hydrogen released from ammonia borane, inorganic gases produced from fireworks, the CO₂/O₂ ratio from expired human breath and a purity test for alcohols. These studies show that the GCwhistle method has great potential for use as a fast sampling ionization method, and for the direct analysis of biological and chemical samples at under ambient conditions.