A Century of Chromatography — Gas Analysis in the First 50 Years

GC CONNECTIONS A Century of Chromatography — Gas Analysis in the First 50 Years John V. Hinshaw, Serveron Corp., Hillsboro, Oregon, USA. Although many decades intervened between the beginnings of chromatography as a liquid–solid adsorption technique and the formal invention of gas–liquid-phase chromatography, those years were full of advances in gaseous chemical separations. This month in “GC Connections,” John Hinshaw reviews the developments before 1952 that established the basis for the modern practice of gas chromatography. The date 21 March 2003 marked the twenty-first century separation scientists, Gas Adsorption passage of 100 years since Mikhail Tswett between gas- and liquid-based Modern chromatographers are familiar (1872–1919) presented a lecture to the chromatography separations; they worked with gas chromatography (GC) column Biological Section of the Warsaw Society of in entirely different disciplines with packings that are the direct descendents of Natural Scientists on his 1901–1903 divergent goals. Not until the 1940s did charcoal. These packings include investigations of liquid–solid adsorptive some begin to draw the analogy between Carbopack-B (Supelco-Sigma-Aldrich, separations of plant pigments at Warsaw their work with gaseous separations and Bellefonte, Pennsylvania, USA), which University.1 This lecture is generally separations with a liquid mobile phase. Yet, contains a surface area of 100 m2 — recognized as the first public disclosure of various separation techniques based upon roughly equal to the area of my laboratory the chromatographic technique, although gas adsorption, which scientists now floor — in 1 g. Adsorption is the primary the term chromatography, which Tswett consider to have been forms of physical effect used in the various gas coined, did not appear in print until several chromatography, gained significance in the separation techniques discussed in this years later in 1906. Tswett pursued his expanding petroleum industry and related column, including gas–solid studies in Russia and Poland and made chemical endeavours of the 1920s and 1930s. chromatography (see the accompanying lecture trips to Germany, France, Belgium Separations based upon gas–solid sidebar “How Do Adsorption and and the Netherlands, so his work was not adsorption and desorption preceded Absorption Differ?”). Absorption, however, unknown to scientists in Western Europe. gas–liquid partition chromatography by occurs in gas–liquid partition Several pioneering researchers in Europe decades, although much of the equipment chromatography when solute molecules and in the United States extended Tswett’s used before the 1940s might be dissolve into the stationary liquid phase. work during his lifetime, but liquid unrecognizable to modern gas Gas–liquid partition chromatography can chromatography (LC) separations in chromatographers. However, these encompass adsorption in addition to general languished until the 1930s, when precedents had already established much absorption when an adsorptive support is the scientific world began to understand of the theoretical and practical basis for coated with a liquid phase to generate a the significance of LC separation and apply gas–liquid partition chromatography by the specific mixed-separation effect. Today, it to various chemical separation and time that A.T. James and A.J.P. Martin adsorptive separations constitute a small analysis problems.2 began their experimental work with liquid- fraction of GC methods, although they At the same time, but largely unknown coated stationary supports in 1950 at the play a very important role in the chemical to those scientists involved with Tswett’s National Institute for Medical Research and petroleum industries. work, different researchers investigated gas (London, UK). Two recent publications by The strong adsorption of gaseous adsorption on solid substances, which was L.S. Ettre3,4 describe the evolution of gas components such as hydrogen, methane, important to mining and associated adsorption chromatography until 1952 in ethane, propane and higher hydrocarbons, businesses at the start of the twentieth more detail than is possible to include carbon dioxide and sulphur dioxide onto century. Certainly, there was little prospect here. I am indebted to Ettre for much charcoal was well known at the beginning for anyone of that time to make the of the information that appears in this of the previous century: miners who noted connection, which is so familiar to “GC Connections” column. that charcoal would sweeten mine gas 2 LC•GC Europe November 2003 GC Connections might have discovered it. Scientists of the primarily for analytical problems only later vapours would be a pariah, but at the time began to incorporate adsorption– in the development of gas chromatography. time it was one of the fastest and most desorption phenomena into chemical Today, elution is the way in which accurate means for determining the processing and analysis, activities that practically all chromatographic separations contents of natural gas, despite the 8 h formed the basis for many modern are performed. With these categories in analysis time. To the manufacturer’s credit, processing techniques. mind, I’ll provide a brief overview of the later versions substituted organic vapours Permanent gas adsorption onto charcoal major developments in gas for the mercury displacer. Figure 1 is fine if the objective is air purification, but chromatography before 1952. illustrates the appearance of a when testing gas mixtures and the chemical chromatogram from this instrument.6 processing of larger quantities of materials Displacement Each of the plateaus represents the period is the goal, researchers need a way to recover In the displacement development of emergence of a pure gas. them from the adsorbent bed. Today, technique, an adsorbent-filled tube is A number of individuals augmented chromatographers classify the possibilities charged with a known gas sample volume, displacement development of adsorbed for desorption from an organized adsorbent usually enough so that nearly the entire gases to meet various analytical challenges. bed into three broad categories: displacement, bed is saturated with each gas in the One technique, attributed to Paul frontal development and elution. Strictly mixture. Then a displacer substance — Schuftan7 (1896–1980) of Gesellschaft für speaking each of these categories glycerol, mercury vapour or any of various Lindes Eismaschinen (Hollriegelskreuth, constitutes a form of chromatography. This heavy organic vapours — is introduced Germany), used a continuous flow of commonality was not formalized, however, gradually into one end of the tube. As the carbon dioxide across a charcoal bed to until many years later. displacer progresses along the bed, it enhance displacement of lighter gases by In the first part of the twentieth century, pushes all of the adsorbed gases off the higher fractions. This technique could be the displacement of weakly adsorbed gases charcoal surfaces it encounters. Moving described as an early form of elution with a strongly adsorbed substance was along the bed, each of the gas development. Other researchers, such as the primary means for recovering gases components displaces all less-strongly Stig Claesson8 (1917–1988) of Uppsala from the sorbent beds used in the chemical adsorbed gases in turn, which results in a University (Uppsala, Sweden) and and natural gas industries. Frontal progression of purified gases exiting the Courtenay Phillips9 (born 1924) of Oxford development, in which the sample itself bed in order of increasing adsorption University (Oxford, UK), developed complex served as a displacer, was also known, but strength. The purified gases are collected devices and accessories to better control it is better for selective purification than for volumetrically or measured with a thermal- the temperatures, pressures and flows of analysis because it results in a gas mixture conductivity detector. their analytical systems. These mechanical exiting the bed. Frontal development won’t Displacement was the basis for the embodiments, unfamiliar to modern be discussed further in this column. so-called natural gas charcoal test used analysts, were marvellous constructions that In elution, a carrier gas conducts in the 1920s and later,5 and was available presaged most of the controls routinely substances along a sorbent bed, but the in the 1940s and early 1950s as an found in present-day GC instrumentation. amount of each substance is limited instrument that was produced by at least Ultimately, however, displacement because users can place only a small one company, the Burrell Corp. (Pittsburgh, development was itself displaced portion of a mixture at the beginning of Pennsylvania, USA).6 Today, an instrument completely by the meteoric rise of elution the adsorbent bed. Elution was used such as this one that used boiling mercury gas–liquid partition chromatography Figure 1: Displacement chromatography Figure 2: Schematic of the GC system used in Erika Cremer’s laboratory in Innsbruck recording from the Turner-Burrell (1946–1949).15 adsorption fractometer, circa 1943. Total time: ϳ8 h; detector: thermal conductivity; sample: 5 L dry natural gas; displacer: mercury vapour; column: 6 ft ϫ 0.75 in. at the entrance, tapering to 0.1875 in. at the exit, packed with Hydrogen 3 charcoal. 4 A 7 3 678 5 12 Vacuum 8 6 4 pump 1 2 Signal 5 6 Time Plateaus: 1 ϭ air, 2 ϭ methane, 3 ϭ carbon 1 ϭ permanganate scrubber, 2 ϭ concentrated

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