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Chemical Analysis in Environmental and Toxicological Chemistry
Published in Stanley E. Manahan, Environmental Chemistry, 2022
Various kinds of chromatographic analysis are used for determining pollutants, especially those in water. First described in the literature in the early 1950s, gas chromatography has played an essential role in the analysis of organic pollutants in water, air, and wastes. Gas chromatography is both a qualitative and quantitative technique; for some analytical applications of environmental importance, it is remarkably sensitive and selective. Gas chromatography is based on the principle that when a mixture of volatile materials transported by a carrier gas is passed through a column containing an adsorbent solid phase or, more commonly, an absorbing liquid phase coated on a solid material, each volatile component will be partitioned between the carrier gas and the solid or liquid. The length of time required for the volatile component to traverse the column is proportional to the degree to which it is retained by the nongaseous phase. Since different components may be retained to different degrees, they will emerge from the end of the column at different times. If a suitable detector is available, the time at which the component emerges from the column and the quantity of the component are both measured. A recorder trace of the detector response appears as peaks of different sizes, depending on the quantity of material producing the detector response. Both quantitative and (within limits) qualitative analyses of the sought-for substances are obtained.
Gas Chromatography
Published in Ernő Pungor, A Practical Guide to Instrumental Analysis, 2020
Gas chromatography is a method suitable for the separation, identification, and quantitative determination of the components of gas mixtures or substances which can be volatilized without decomposition. Commercially available devices can be applied to the solution of diverse problems. The nature of the column to be applied is dependent on the nature of substances to be separated. The detectors used are mostly based on ionization (e.g., hydrogen flame ionization, argon ionization, electron capture) and on heat conductivity. The electrical signal provided by the detector and recorded as a function of time is called the chromatogram, which is a recording of the result of separation. Each peak in the series of peaks represents a substance. The time elapsed from the introduction of the sample until the appearance of the maximum (retention time) or the volume of carrier gas passed through the system (retention volume) during this time is characteristic of the nature of the substance, whereas the peak area (the integral of the curve with respect to time) is in correlation with the amount of substance.
Gas Chromatography
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
Yuwen Wang, Mochammad Yuwono, Gunawan Indrayanto
There are two types of GC: gas–liquid chromatography (GLC) and gas–solid chromatography (GSC). When a capillary column is used for the separation, the system is called capillary GC. High-resolution gas chromatography is the term for GC using high-resolution fused silica open tubular columns.
Flammability and Explosion Risk of Post-explosion CH4/air and CH4/coal dust/air Mixtures
Published in Combustion Science and Technology, 2021
Song Lin, Zhentang Liu, Jifa Qian, Xiaoliang Li, Qiming Zhang
A Gas chromatograph (GC-9790) and hydrogen detector (GDX-H2) were used for gas analysis. The gas chromatograph is composed of a carrier gas system, a sampling system, a chromatographic column, a monitoring system, and recording and data processing systems. The detected gas was quantitatively analyzed by external standard quantitative method, and the detection resolution is 1 × 10−6. The accuracy of temperature control is less than ± 0.1°C and the temperature is increased at 0.1 to 30°C min−1. Hydrogen was unable to be measured by the gas chromatograph. The hydrogen detector detects hydrogen by electrochemical principle with a detection resolution of 1 × 10−6. The accuracy of the gas analyzer was verified by testing a gas mixture which was prepared to a known composition.
Synthesis and characterization of Salicornia bigelovii and Salicornia brachiata halophytic plants oil extracted by supercritical CO2 modified with ethanol for biodiesel production via enzymatic transesterification reaction using immobilized Candida antarctica lipase catalyst in tert-butyl alcohol (TBA) solvent
Published in Cogent Engineering, 2019
Adewale Johnson Folayan, Paul Apeye Lucky Anawe, Augustine Omoniyi Ayeni
The fatty acid compositional analysis was done by using Agilent, HP 6890 Gas Chromatograph with Flame ionization detector and 6890 Auto Sampler that connects with a controller box (Figure 2). Gas chromatography technique is used for separation and detection of various molecular weight compounds in the gas phase. The HP 6890 gas chromatograph equipped with flame ionization detector has a robust mechanism for correct analysis of fatty acids present in the Salicornia oil samples. It has an electronic pneumatic control system for all gas pressures and flow rates and an on-board sensor that compensate for ambient temperature changes in the range of +4–450°C. The automatic injector system and oven cryocooling gives room for exact measurement of retention attributes of volatile compound for accurate estimation of their physical properties.
Friction and Wear Phenomena of Vegetable Oil–Based Lubricants with Additives at Severe Sliding Wear Conditions
Published in Tribology Transactions, 2018
Adli Bahari, Roger Lewis, Tom Slatter
Zinc may also play this role on the counterface in order to minimize metal-to-metal contact. This is shown by the detection of zinc from the result of EDX analysis (Table 5) on the worn specimens for ZD:PO and ZD:SBO lubricants. In order to determine that the wear improvement was solely due to the ZDDP additive, a test of fatty acid composition on PO, SBO, ZD:PO, and ZD:SBO oils was performed by gas chromatography (Fig. 6). In a gas chromatography test, the sample solution is injected and carried by a moving gas into a separation tube known as the column. The fatty acid components of the solution that exit from the column at different times are then identified by the detector and can be compared with the result of a standard solution. It was noted that there was no significant difference found in the fatty acid composition of vegetable oil–ZDDP mixtures compared to their pure oil state. This indicates that the fatty acid compositions in the vegetable oil were not influenced by the existence of ZDDP.