Dionex instrument

Fig. 2.18 Ion chromatograms obtained with Dionex instrument using (anodic) AMMS and CMMS micromembrane suppression (a) monoprotic organic acids by anion exchange (b) diprotic organic acids by anion exchange...

The directions are based on a Dionex instrument. However, the following descriptions are presented so any instrument can be adapted. 

To operate the ion chromatograph, read the operator s manual. Alternatively, your instructor may have a written procedure. For purposes of illustration, we list below a procedure used in our lab. A Model 2000 (Dionex) instrument interfaced to a PC via a 900 (PE-Nelson) interface is available ... 

Many instrumentation companies have commercialized complete or modular CE systems. The principal vendors are Beckman Instruments, Inc. (Fullerton, CA) Bio-Rad Laboratories (Hercules, CA) Dionex Co. (Sunnyvale, CA) Hewlett Packard (Palo Alto, CA) ISCO, Inc. (Lincoln, NE) Otsuka, Ltd. (Tokyo, Japan) Perkin-Elmer -ABI (Foster City, CA) Thermo-Separation Products (Fremont, CA) and Waters Associates (Milford, MA). 

Based on Table 3.2, we can deduce from the available flow rates that some manufacturers clearly optimized their systems for 2.1 mm inner diameter (ID) columns, namely the Jasco X-LC, the Thermo Accela, and the Waters Acquity. By sacrificing flexibility in column ID, these systems have been completely optimized to these 2.1 mm columns. Achieving that will be explained below. The instruments of Agilent and Dionex mentioned in Table 3.2 involve a more flexible approach. The higher flow rate limits of their systems allow the use of columns with larger Ids. Users benefit from the better efficiency obtained with 4.6 or 3.0 mm ID columns instead of 2.1 mm ID columns of similar length and their systems are fully compatible with existing conventional methods. 

The first commercial CE instruments were introduced in 1988 by Applied Biosystems (Foster City, CA) and Beckman Coulter (Fullerton, CA). The main challenge during these days was to find out how to overcome poor reproducibility and improve separation efficiency. In the early 1990s, many instrument-building companies introduced CE systems (e.g. Isco (Lincoln, NE), Bio-Rad (Hercules, CA), Waters (Milford, MA), Applied Biosystems, ThermoQuest (Santa Fe, NM) and Dionex (Sunnyvale, CA)), but at the end of the decade only Beckman Coulter... 

Today nearly all of the major HPLC companies offer a pHPLC system or at least the possibility to modify a standard instrument to accept micro-bore columns. In our laboratory, we routinely use the pHPLC systems Ultimate from Dionex/LC Packing (Ligure 3.2), the Extreme Simple 4-D... 

Analysis. The solution in each bubbler was transferred to a 25 mL volumetric flask and diluted to volume with the collection medium (10 3 M Na2C03). In the case of samples collected from diluted diesel exhaust, an excess (3 mL) of this solution was flushed through a 100 yL sample loop of Dionex Model 14 ion chromatograph. The sample was analyzed on the anion system with instrumental conditions presented in Table I. 

Dionex Corporation 1228 Titan Way P.O. Box 3603 Sunnyvale, CA 94088-3603 Pulsed amperometric detector cells and instrumentation... 

Automated amino acid analyzers are available from a number of manufacturers (e.g., Beckman, Biotronik, Dionex, LKB, Pickering). These are integrated systems in which the column resin, buffer system, and various instrumentation parameters have been co-optimized for that particular system. All are reported in the literature to perform very well. The advantage to purchas-... 

Tomlinson and Caruso [28] also performed the speciation of Cr(III) and (VI) using a Dionex AS-11 anion-exchange microbore column and 6 mM 2,6-PDCA-8.6 mill lithium hydroxide mobile phase. A thermospray source was used as the interface between LC and ICP-MS. Absolute limits of detection were at the pg level for both species using this instrument assembly. 

Shown in Fig. 2.8 is a schematic diagram of the Dionex ion exchange liquid chromatograph used by Smee et al. [40], The instrumentation consists essentially of a low capacity anion exchange column, the separator , a high capacity cation exchange column, the suppressor and the detection system, a high sensitivity conductivity meter and recorder. 

Dionex 2010i ion chromatograph, Dionex electrochemical detector, Houston Instrument Omniscribe chart recorder. 

Biosym Technologies, Inc. Bristol-Myers Squibb Brookhaven National Laboratory Dionex Corporation Du Pont Merck Pharmaceutical Co. Finnigan MAT Fisons Instruments Hewlett-Packard Co. 

The accelerated solvent extraction (ASE) system introduced by Dionex uses standard solvents at elevated temperatures and pressures to increase extraction efficiency. Samples are placed in stainless-steel extraction vessels that are loaded into the ASE that has been programmed for the extraction protocol. The instrument allows for the unattended extraction of 24 samples. The initial units allowed for solvent blending by premixing solvents before they were placed into the ASE. Recent modifications allow solvent blending to be accomplished in-line. There has been some controversy about the use of the name ASE because it points to instrumentation from one company and other companies have introduced competing products. It has been proposed that the ASE technology be more correctly referred to as pressurized fluid extraction because ASE denotes a commercial device. 

Supercritical fluid extraction can be performed effectively with very simple systems. Figure 5 displays the basic components of an effective analytical SFE device. There are relatively few commercial suppliers of dedicated supercritical fluid extraction instrumentation. Table 7 shows the companies that promote SFE instrumentation as of the writing of this chapter. Some of the more traditional instrument manufacturers such as Hewlett-Packard (7680T SFE), Dionex (SFE 723), and Supelco (SFE-400) have discontinued their SFE lines. Dionex has invested quite heavily into high-temperature/high-pressure solvent extraction devices, and this will be described in the next section. For most purposes, inexpensive and efficient extraction units can be assembled using the basic components shown in Figure 5. 

The HPLC-GFAA instrumentation and analyses condition have been described previously (see references 25-28). The AA detection of arsenic was at 193.7 nm. The HPLC column was a Dionex anion exchange column with 0.2M (NH ) CO in aqueous methanol as the eluting solvent. The GC-MS analyses were accomplished using a Finnigan 4023 mass spectrometer system with a 30 m x 0.3 mm DB-5 (J W) capillary column, conditions 55° 3 min.) - 300°/min. 

A recent advance is accelerated solvent extraction (ASE), a method that uses high temperature and pressure to push an organic solvent through a solid material and to collect the eluent in a vial (Fig. 9.2). The instrument, made by Dionex, is automated and may run 30 samples at once. The instrument can process one sample every 15 min with extraction efficiencies equal to that produced by Soxhlet extraction in 12 h (Dionex, Product Literature, Appendix). The extraction does not use supercritical fluids but consists of using elevated... 

Shortly after the invention of suppressed ion chromatography, commercial instruments for its use were made available by the Dionex Corporation. Ion chromatography became an almost overnight sensation. It now became possible to separate mixtures such as F, CF, Br", NOs and S04 in minutes and at low ppm concentrations. Analytical problems that many never knew existed were described in an avalanche of publications. 

Major manufacturers of HPLC instruments include Waters, Agilent (formerly Hewlett Packard), and Shimadzu, PerkinElmer, Thermo, Beckman, Varian, Hitachi, Jasco, Dionex, Gilson, Scientific Systems (SSI), and Isco. The Internet addresses of these companies can be found in the reference section. HPLC is a mature technology and most manufacturers have highly reliable products with sufficient performance and feature sets to be competitive in the market place. However, there can still be significant differences between the vendors on these performance characteristics on systems (dwell volume, dispersion), pumps (low flow, seal life), autosamplers (carryover, speed, sample capacity, minimum sample volume), and detectors (sensitivity, gradient baseline shift). 

Since pressurized fluid extraction (PFE), also known as accelerated solvent extraction (ASE ), is a relatively new technique, the commercial availability of PFE instruments is limited. A commercial PFE system ( ASE 200 ) currently available is a fully automated sequential extractor developed by the Dionex Corporation, USA. This mainly consists of a solvent-supply system, extraction cell, oven, collection system and purge system, all of which are under computer control. A schematic diagram of a PFE system is shown in Figure 7.15. This system (ASE 200) can operate with up to 24 sample-containing extraction vessels and up to 26 collection vials, plus an additional four vial positions for rinse/waste collection. 

The authors would like to acknowledge the support from Dionex Corporation (Salt Lake City, Utah) for making a Dionex ASE 200 instrument available, and Dr. Reglero for supplying this project with samples and the Ministerio de Educacidn y Cultura of Spain (Postdoctoral Fellowship to FJS) is gratefully acknowledged. 

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