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Until recently liquid chromatography has been a somewhat neglected branch of science. However, the availability of precision equipment, and even complete instruments, has made…
Abstract
Until recently liquid chromatography has been a somewhat neglected branch of science. However, the availability of precision equipment, and even complete instruments, has made possible liquid chromatography separations of a more advanced nature. For example, suitable detectors have been developed, and pumps are available which deliver accurate volumes of solvent under pressure.
For the separation and isolation of simple chemical compounds, the molecular weights of which in general do not exceed 600, gas chromatography offers one of the most flexible and…
Abstract
For the separation and isolation of simple chemical compounds, the molecular weights of which in general do not exceed 600, gas chromatography offers one of the most flexible and adaptable analytical techniques available in the modern laboratory. It is only just over 25 years ago that the first successful applications of this technique were reported by James and Martin, yet modern commercial gas chromatographs exhibit a high degree of refined engineering applied to the separation procedures themselves which, when combined with microprocessor control and other recent developments in the field of electronic data handling, offer to the analyst considerable scope for the examination of even the most intractable samples. In the paint industry the facilities offered by gas chromatography are being fully exploited in the analysis of raw materials, notably solvents, monomers, oils and fats; in the analysis of finished paints and in the control of the working environment as demanded by present‐day health and safety regulations. This article presents a review of the analytical procedures that are possible using modern gas chromatography techniques.
Yasamin Soleimanian, Mohammad A. Sahari and Mohsen Barzegar
The purpose of this study was to investigate the efficiency of low temperature fractional crystallization to increase polyunsaturated fatty acid (PUFA) content of fish oil…
Abstract
Purpose
The purpose of this study was to investigate the efficiency of low temperature fractional crystallization to increase polyunsaturated fatty acid (PUFA) content of fish oil. Effects of temperature, stages of crystallization, rate of cooling, agitation and addition of primary nucleus on separation efficiency were evaluated. Low temperature crystallization of triacylglycerols (TAGs) was used to increase PUFA content of fish oil (initial PUFA content ∼30 g/100 g oil).
Design/methodology/approach
To optimize the fractionation process, the effect of fractionation temperature (7, 5, 0 and −5°C), crystallization procedures, cooling rate, agitation and addition of primary nucleus on PUFA content was evaluated.
Findings
The best relationship between PUFA concentration (45.8 g/100 g oil) and PUFA yield (51.5 per cent) was attained by performing two-stage crystallization of TAGs at the final temperatures of 5 and 0°C under slow cooling rate (3°C h−1 for first fractionation procedure and 0.7°C h−1 for second stage, until the final fractionation temperature, 0°C, was reached) and slow agitation (3 rpm) and in the presence of primary nucleus, which resulted in 50 per cent increase in PUFA content over the original fish oil.
Practical implications
Determination of iodine and saponification values, refractive index, solid fat content, melting point, cholesterol content of original oil and final fractionated product with the highest PUFA ratio showed that fractionation significantly alters physical and chemical properties of the fraction.
Originality/value
Comparison of iodine value, saponification value, refractive index, solid fat content, melting point and cholesterol content of original oil and the final fractionated product (with the highest PUFA ratio) showed that the fractionation process significantly alters mentioned properties of the initial oil.
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Kathy Holley, Mark Pennington and Paul Phillips
Introduces gas chromatography (GC) a key analytical technique inthe food industry. It enables complex organic substances to be separatedand identified quickly and cheaply…
Abstract
Introduces gas chromatography (GC) a key analytical technique in the food industry. It enables complex organic substances to be separated and identified quickly and cheaply. Substances to be analysed by GC must be volatile, i.e. readily pass into the gas phase. The substance to be analysed is vaporized and moved through a long column by an inert carrier gas. The column is filled with a packing material covered with an involatile liquid. The molecules of each substance in a mixture will become distributed between the gas and the liquid. The more volatile a substance the longer it will be moving with the carrier gas, and the quicker it will emerge from the column. Some substances must be extracted from the food analysis by GC, e.g. fatty acids from triglycerides. Others, such as alcohols, can be injected directly into the column.
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In view of the changes which have taken place in this field in recent years, it is perhaps a suitable time to review the fundamentals of the subject, in order that the…
Abstract
In view of the changes which have taken place in this field in recent years, it is perhaps a suitable time to review the fundamentals of the subject, in order that the significance of recent developments might not be lost for the surface coatings analyst.
The majority of binders used in paint manufacture are either highly‐viscous or solid materials in their own right. The identification of their chemical constituents has been…
Abstract
The majority of binders used in paint manufacture are either highly‐viscous or solid materials in their own right. The identification of their chemical constituents has been reported by Haken (71) using infrared spectroscopy at liquid nitrogen temperature. However, the procedure proved to be very expensive since a great deal of breakage of the equipment occurred owing to the need to keep cooling and then reheating to room temperature. A better procedure was considered to be fragmentation of the initial polymer samples to give volatile fractions better suited to GC examination, which was just as accurate as the spectroscopic approach and far simpler and cheaper to carry out.
Shu-An Hsieh and Jared L. Anderson
This paper aims to study the mass loss of three-dimensional (3D) printed materials at high temperatures. A preconcentration and analysis technique, static headspace gas…
Abstract
Purpose
This paper aims to study the mass loss of three-dimensional (3D) printed materials at high temperatures. A preconcentration and analysis technique, static headspace gas chromatography-mass spectrometry (SHS-GC-MS), is demonstrated for the analysis of volatile compounds liberated from fused deposition modeling (FDM) and stereolithography (SLA) 3D printed models under elevated temperatures.
Design/methodology/approach
A total of seven commercial 3D printing materials were tested using the SHS-GC-MS approach. The printed model mass and mass loss were examined as a function of FDM printing parameters including printcore temperature, model size and printing speed, and the use of SLA postprocessing procedures. A high temperature resin was used to demonstrate that thermal degradation products can be identified when the model is incubated under high temperatures.
Findings
At higher printing temperatures and larger model sizes, the initial printed model mass increased and showed more significant mass loss after thermal incubation for FDM models. For models produced by SLA, the implementation of a postprocessing procedure reduced the mass loss at elevated temperatures. All FDM models showed severe structural deformation when exposed to high temperatures, while SLA models remained structurally intact. Mass spectra and chromatographic retention times acquired from the high temperature resin facilitated identification of eight compounds (monomers, crosslinkers and several photoinitiators) liberated from the resin.
Originality/value
The study exploits the high sensitivity of SHS-GC-MS to identify thermal degradation products emitted from 3D printed models under elevated temperatures. The results will aid in choosing appropriate filament/resin materials and printing mechanisms for applications that require elevated temperatures.
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