Grantee Research Project Results
1999 Progress Report: Field-Usable Compact Capillary Based Liquid/Ion Chromatographs - Real Time Gas/Aerosol Analyzers
EPA Grant Number: R825344Title: Field-Usable Compact Capillary Based Liquid/Ion Chromatographs - Real Time Gas/Aerosol Analyzers
Investigators: Dasgupta, Purnendu K.
Institution: Towson University
EPA Project Officer: Hahn, Intaek
Project Period: October 15, 1996 through October 14, 1999
Project Period Covered by this Report: October 15, 1998 through October 14, 1999
Project Amount: $333,141
RFA: Analytical and Monitoring Methods (1996) RFA Text | Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Environmental Statistics , Air Quality and Air Toxics , Water , Air , Land and Waste Management
Objective:
Ion and liquid chromatography are two of the most widely used techniques in environmental analysis, but both remain relegated to the laboratory due to the lack of truly portable and robust equipment. The objectives of the present project are to construct capillary liquid and ion chromatographs, with appropriate detectors, that will be easily portable and useable in the field. All operational control and data acquisition will be provided by a laptop personal computer. The chromatographic efficiencies will rival those of present day conventional-sized benchtop instruments.
Progress Summary:
In summary, a gradient-capable pumping system for capillary RPLC has been developed. The use of pure water as a nonpolar eluent at elevated temperatures has been explored. The use of pure water as an eluent will enable the coupling of the capillary RPLC system to more powerful detection systems.
A completely portable capillary scale ion chromatograph (IC) system was developed and coupled to a micro-scale wet denuder. Its viability as a trace gas analyzer was demonstrated. A gradient-capable pumping system was designed to enable reverse-phase separations to be performed in the field. To reduce analysis time and increase system performance, the upper pressure limit was increased to 14,000 psi. Column heating also was explored as a method of increasing system performance. High-speed gradient separations were performed at 250°C. Studies also were conducted using only water as a reverse-phase eluent at sub-supercritical and supercritical temperatures.
An inexpensive, compact, parallel-plate diffusion denuder coupled capillary IC system was demonstrated for the determination of soluble ionogenic atmospheric trace gases. The active sampling area (0.6 x 10 cm2) of the denuder is formed in a novel manner by thermally bonding silica gel particles to the surface of plexiglass plates. The effluent liquid from the parallel-plate diffusion denuder is collected and preconcentrated on a capillary preconcentrator column before analysis with a capillary ion chromatograph. Using SO2 as the test gas, collection efficiency is essentially quantitative at air sampling rates up to 500 mL/minute. The system provided a limit of detection (LOD) of 1.6 parts per trillion for SO2 over a 10-minute sampling period.
The initial low pressure work in IC allowed the use of commercial glass syringes; however, the pressure requirements of a competitive reverse-phase system demands a pumping system that is capable of operating at much higher pressures. To solve this problem, stainless steel syringes were designed and constructed in-house. The syringes were developed using a displacement design, allowing the teflon seal to be placed at the end of the syringe. The addition of a high-pressure injection system allows this setup to operate at pressures of up to 14,000 psi. The maximum peak efficiency during gradient operation was observed for toluene, which exhibited 168,500 theoretical plates. The average peak efficiency for the 10 components during the gradient run was 111,000 theoretical plates, correlating to an average of 14,000 plates per minute.
To further increase system performance, the effect of operating temperature was studied. The system is capable of operating at temperatures as high as 250°C, and at pressures of up to 14,000 psi. Due to the reduction of the eluent viscosity and enhanced mass transport at elevated temperatures, the optimum flow rate is much higher than at ambient temperatures. Performance limitations due to poor mass transport at flow rates higher than the optimum are greatly reduced. The high-pressure capability of the system then allows operation at unusually high flow rates, enabling high-speed gradient separations with excellent performance on temperature stable zirconia- and titania-based packings. This configuration allowed the separation of eight alkylbenzene derivatives in less than 2 minutes.
The use of varying organic modifiers in reverse phase liquid chromatography (RPLC) greatly complicates the use of more advanced detection methods, such as flame ionization detection (FID) or mass spectrometry (MS). At elevated temperatures, the dielectric constant of water decreases to the point that organic modifiers are not needed. The constructed system uses water as the eluent while operating at temperatures from 100°C up to 400°C. Derivatives of alkyl benzenes up to butyl benzene have been separated.
Future Activities:
Work is currently being performed in an effort to couple the hot water eluent system with an FID detector along with a mass spectrometer.
Journal Articles on this Report : 5 Displayed | Download in RIS Format
| Other project views: | All 15 publications | 7 publications in selected types | All 7 journal articles |
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Boring CB, Dasgupta PK, Sjogren A. Compact, field-portable capillary ion chromatograph. Journal of Chromatography A 1998;804(1-2):45-54. |
R825344 (1999) R825344 (Final) |
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Boring CB, Poruthoor SK, Dasgupta PK. Wet effluent parallel plate diffusion denuder coupled capillary ion chromatograph for the determination of atmospheric trace gases. Talanta 1999;48(3):675-684. |
R825344 (1999) R825344 (Final) |
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Kephart TS, Dasgupta PK, Alexander JN. An affordable high-performance pumping system for gradient capillary liquid chromatography. Journal of Microcolumn Separations 1999;11(4):299-304. |
R825344 (1999) R825344 (Final) |
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Kephart TS, Dasgupta PK. Hot eluent capillary liquid chromatography using zirconia and titania based stationary phases. Analytica Chimica Acta 2000;414(1-2):71-78. |
R825344 (1999) R825344 (2000) R825344 (Final) |
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Sjogren A, Boring CB, Dasgupta PK, Alexander IV JN. Capillary ion chromatography with on-line high-pressure electrodialytic NaOH eluent production and gradient generation. Analytical Chemistry 1997;69(7):1385-1391. |
R825344 (1999) R825344 (Final) |
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Supplemental Keywords:
ion chromatography, capillary chromatography, trace gas measurement., RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Air, Engineering, Chemistry, particulate matter, Environmental Chemistry, Monitoring/Modeling, National Center for Atmospheric Research, aerosols, field portable monitoring, ambient aerosol, environmental monitoring, ambient particle properties, environmental measurement, real-time monitoring, optical detectors, aerosol analyzers, analytical chemistryRelevant Websites:
http://www.ttu.edu/~chem/faculty/dasgupta/dasgupta.html ExitProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.