The need for chromatographic techniques that provide increased resolution, molecular structure elucidation, sensitivity, and separation power, along with decreased analysis times and detection limits, has become critical for applications ranging from environmental analyses, chemical syntheses, polymer characterizations to toxicological investigations, pharmaceutical, and especially in areas of textile research. To meet this need, techniques that combine various chromatographic methods, as well as ones that incorporate analytical (primarily spectroscopic) techniques into traditional chromatography systems, have evolved. The result of this wide range of pairings is a new world of separation and analysis technology that is simultaneously as flexible, efficient, and precise as any specific application may necessitate.
What is Chromatography?
Chromatography is a non-destructive process for resolving a multi-component mixture of traces, minor or major constituents into its individual fractions. Chromatography may be applied to both quantitative and qualitatively. It is primarily a separation tool.
Principle Underlying Chromatography
It is based on Partition Coefficient in which a compound describes the way in which it is distributed itself between two immiscible phases.
Concentration in Solvent A / Concentration in Solvent B = Kd
Kd --- Partition Coefficient (or) Distribution Coefficient
Theories of Chromatography
It is based on two important theories-
1. Plate Theory
2. Rate Theory
Development of Chromatogram
It is based on three categories �
a. Frontal Analysis
b. Elution Analysis
c. Displacement Analysis
Basic Classification of Chromatographic Techniques
� Paper Chromatography
� Column Chromatography
� Ion Exchange Chromatography
� Thin Layer Chromatography
� Gel Permeation Chromatography
� Adsorption Chromatography
� Gas Chromatography
HPLC (High Performance/Pressure Liquid Chromatography)
Identified Areas of Application in Textiles �
a) Chromatography in Dye Testing:
Expert�s first need to place an item historically by understanding the fibers and dyes involved. Then conservators rely on analytical tools to assess the makeup and age of a piece of cloth, and then consider the safest methods for conservation. Dye testing is one of the methods used to understand the provenance of a textile. When natural dyes are suspected, samples of the fiber are subjected to analysis to find out the dyes used and then compared to a standard database of dyes.
Other methods are Thin Layer Chromatography and High Pressure Liquid Chromatography (HPLC) is also used.
b) Analysis of the Swelling and Pore Structure of Lyocell Fibers:
Lyocell yarns are treated with NaOH, liquid ammonia, high pressure steam, and polycarboxylic acids, and then dyed with five reactive dyes. The degree of swelling and the micropore structure of the swollen samples in water are analyzed using size exclusion chromatography. The water content of the samples is also measured by centrifugal and chromatographic techniques.
c) HPLC in the Analysis of Dyed Textiles:
Separation and quantitative determination of anthraquinones is achieved by high performance liquid chromatography (HPLC) in mixtures of methanol, water and formic acid on a reversed-phase stationary phase. The products are identified by retention time and, more accurately, by standard additions and UV-visible spectroscopy. This methodology has been applied to extracts of plant roots and insects, commonly used in earlier times as the source of red dyestuffs for dyeing textiles. Quantitative evaluation of the anthraquinone derivatives present in ancient red dyes was carried out after acid hydrolysis of 0.2 to 2.0mg of textile fibre. Due to the great sensitivity of the method, important minor constituents, such as kermesic acid in cochineal, can be detected.
d) HPLC in the Dye Analysis of Pre-Columbian Peruvian Textiles:
Series of textiles belonging to various pre-Columbian civilizations as well as a series of present-day Peruvian natural dyes were analyzed using high-performance liquid chromatography and diode-array detection. The analytical results were classified according to the composition of known dyes or to specific compositional patterns of unknown dyes. The analysis of the complex yellow dyes may be useful for the determination of early Peruvian dye.
e) HPLC in the Characterization of Dyes in Environmental Samples:
Thermo spray HPLC/MS is used to characterize azo, diazo, and anthraquinone dyes in wastewater and gasoline. Thermo spray analysis of these dyes primarily produced [M + H] + ions with few fragments. �Filament on� Operation of the interface aided in the production of fragment Ions for the azo dyes is analyzed. The commercial diazo and anthraquinone dyes analyzed by HPLC/MS proved to be very complex mixtures of nearly 40 alkyl-substituted dye components, making monitoring and identification of a particular dyestuff very difficult. Thermo spray HPLC/MS methods are used to detect dyes down to 10 ppt (parts per trillion) in wastewater, 100 ppb in soil, and 1 ppm in gasoline. The �filament on� operation of the thermo spray interface provided additional fragment ions, aiding the structural elucidation of these dyes.
Highlight of the Advancements
1) Supercritical Fluid Chromatography (SFC):
Packed column supercritical fluid using Chromatography CO and polar modifiers has the potential to be a powerful tool for the analysis of a variety of textile chemicals and dyestuffs. To date, the development of SFC methods for these applications has been significantly hampered by the lack of a suitable detector. Since many textile chemicals lack strong chromophores or would require the use of heavily modified CO, UV-Vis and Flame ionization detectors (FID) are not practical. However, with evaporative light scattering detector (ELSD) being directly interfaced to a packed column SFC, we have now achieved chromatographic resolution, efficiency and selectivity comparable to that from capillary SFC.
2) Investigations of Ultrasonic Effects in Textile Wet Processing:
Although a number of fundamental studies on the effects of ultrasound in various physicochemical processes have been conducted, little mechanistic work has been done for textile processes. Some research is going on to determine the mechanisms responsible for the effects of ultrasound in textile wet processing and establish the relative importance of phenomena occurring in the bulk solution and in the fiber.
The mechanisms under investigation include:
� increasing fiber swelling in water
� reducing glass transition temperature of the fiber (dilation of polymeric amorphous regions)
� increasing the diffusion coefficient of dye in the polymer
� increasing the fiber/dyebath partition coefficient
� enhancing transport of the dye to the fiber surface by reducing the boundary layer thickness
� breaking up of micelles and high molecular weight aggregates into uniform dispersions in the dye bath.
3) Tandem Chromatography
Tandem methods, used in all manner of organic and inorganic syntheses, are increasingly used in the biotechnology and textile fields. The total range of applications is too lengthy and diverse to summarize.
4) Hyphenated Chromatography
Hyphenated methods, like their tandem counterparts, may be conducted either on- or off-line. Just as off-line methods originally predominated in coupled systems, they were also the original option of choice for hyphenated techniques. However, the regular need for cold trapping the fractional eluates before analysis proved to be a significant limitation. As a result, on-line processing of textile samples became the norm, and numerous instrument companies now produce machines in which the coupled technologies are packaged, interfaced, and sold as a single unit.
Gas Chromatography (GC) is one of the most widely used quantitative analytical methods because of its ease of use, discriminating power, and ability to use a wide range of stationary phases. It is not surprising, therefore, that the first hyphenated method was GC-MS. GC has limitations, however (compounds may have similar retention times, only volatile substances can be analyzed, thermo labile compounds may not be separated, etc.), and GC-MS necessarily suffers from the same inherent deficiencies. As a result, the introduction of the LC-MS in 1972 was an obvious next step; the advent of the LC-MS not only overcame the GC-MS�s limitations but also avoided the problems of analyte derivitization while allowing for the direct determination of peak purity.
The ability to separate completely and identify the components in a mixture of chemical compounds is a key to chemistry and central to the field of chromatography. Since their conception in the 19th century, chromatographic techniques have improved, advanced, and been used in different areas.
By general agreement, however, single-column chromatographic techniques, and even multidimensional methods, have reached their theoretical limits of utility; no substantive advances in these fields have occurred within the past 15 years or so. As a result, it is increasingly rare to find examples in the area of textiles.
Hyphenated methods continue to develop and are regularly featured for their novelty and utility. Many of the latest innovations include coupling chromatographic systems with electrochemical methods (amperometry, paleography, coulometery, etc.) and various other instruments that measure optical activities, refractive indices, and chemical conductivities have paved a way in satisfying the need of the hour.
The number and complexity of chromatographic systems are staggering and imply that the world of separation and analysis technology remains in its infancy and will continue to help all fields, especially the textile field that make the people.
1. Gurdeep Chatwal, �Instrumental Methods of Chemical Analysis�
2. Jan Wouters, Noemi Rosario-Chirinos, �Journal of the American Institute for Conservation�, Vol. 31, No. 2 (summer, 1992), pp. 237-255.
3. Jan Wouters, �Studies in Conservation�, Vol. 30, No. 3 (Aug., 1985), pp. 119-128
4. V.K. Srivatsava, �Introduction to Chromatography�
5. www.pbs.org/obp/history detectives/techniques/textile.html
About the author:
I am M. Parthiban, completed my M.Tech in Textile Technology at A.C.College of Technology, Anna University during May 2005.I did my B. Tech in Textile Technology at Bannari Amman Institute of Technology, Sathyamangalam and passed out in First Class with Distinction during the year 2002.Worked as Design Engineer in Sharada Terry Products for the period of nine months.Settled my life in the filed of teaching.So far published 10 articles in National and International Journals. So far, presented 4 papers in National and International Conferences. Currently working as lecturer in the department of textile chemistry, SSM College of Engineering.
M. Rameshkumar is the Faculty of Textiles, SSM College of Engineering, Komarapalayam-638 183.TamilNadu. Email: firstname.lastname@example.org
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