Modular HPLC systems

A Varian Unity Inova 600-MHz NMR instrument (Palo Alto, CA) equipped with a H C/ N pulse field gradient triple resonance microliow NMR probe (flow cell 60pL 3mm O.D.) was used. Reversed-phase HPLC of the samples was carried out on a Varian modular HPLC system (a 9012 pump and a 9065 photodiode array UV detector). The Varian HPLC software was also equipped with the capability for programmable stop-flow experiments based on UV peak detection. An LCQ classic MS instrument, mentioned in the previous section, was connected on-line to the HPLC-UV system of the LC-NMR by contact closure. The H resonance of the D2O was used for field-frequency lock, and the spectra were centered on the ACN methyl resonance. Suppression of resonances from HOD and methyl of ACN and its two C satellites was accomplished using a train of four selective WET pulses, each followed by a Bo gradient pulse and a composite 90-degree read pulse [41]. 

Figure 1.4 Modular HPLC system, (a) Labelled mobile phase reservoir mobile phase is degassed and filtered, (b) Pump capable of delivering pulse-free flow at pressures up to 6000psi. (c) Injection valve in industrial applications an autosampler would normally be used, (d) Column often with dimensions 250 x 4.6 mm i.d. (e) Detector most popular means of detection is by UV absorbance. (0 Labelled waste mobile phase reservoir, (g) Int ator or PC-based data handling of signal from detector.

A Varian Unity Inova 600 MHz NMR instmment (Palo Alto, CA), equipped with a H C/ N pulse field gradient triple resonance microflow NMR probe (flow ceU 60 pL 3 mm O.D.), was used. Reverse-phase HPLC of the samples was carried out with a Varian modular HPLC system (a 9012 pump and a 9065 photodiode array UV detector). The Varian HPLC software was also... 

The modular HPLC system used in this study included the following components a Model IlOA Altex pump (Beckman Scientific Instruments) or a System 4 Series programmable pump (Perkln-Elmer Corporation), an In-line filter, a Model 773 variable-wavelength DV detector (Kratos Scientific Instruments) fitted with a 12 pL flow cell, a Model 600 Series autosampler with a nominal volume of 20 pL (Perkin Elmer Corporation) and a two channel recorder (Kipp and Zonen). The chromatographic data were processed with the aid of a Model 3357 laboratory computer (Hewlett-Packard). 

Having established the fact that a wide range of HPLC column support materials and packed columns are currently available, the conditions under which the latter must be operated will now be discussed in general terms, so that the reader may be able to understand how the modern, modular HPLC system came to be developed. 

A simple system is comprised of an isocratic pump, a manual injector, a UV detector, and a strip-chart recorder. A schematic diagram of an HPLC instrument is shown in Fig. 15.4. This simple configuration is rarely used in most modern laboratories. A typical HPLC system is likely to consist of a multi-solvent pump, an autosampler, an on-line degasser, a column oven, and a UV/Vis or photodiode array detector all connected to and controlled by a data-handling workstation. Examples of modular and integrated systems are shown in Fig. 15.5. Some of the important instrumental requirements are summarized in Table 15.2. 

HPLC systems can be classified as modular or integrated. In a modular system, separate modules are stacked and connected to function as a unit, whereas in an integrated system, modules are built inside a single housing and often share a common controller board. These built-in modules cannot function outside the system solvent lines and electrical wires are inside the housing. Modular systems are considered easily serviceable since internal components are easily accessible, and the malfunctioning module can be swapped. Integrated systems provide... 

FIGURE 2 Examples of modular and integrated HPLC systems. Upper row (I to r) modular systems Agilent 1100 Series, Jasco LC-2000 Series Lower row (I to r) integrated systems Waters Alliance, Shimadzu LC-2010. 

The performance of an HPLC system can be evaluated by examining the key functions of the various modules that comprise the system, followed by holistic testing that challenges the performance of the HPLC components as an integrated system. The holistic testing is commonly referred to as the performance qualification (PQ). The holistic test can be as simple as running a frequently used HPLC method in the laboratory. Modular testing of various components, which is... 

Figure 3.1—Schematic of an HPLC system and example of a modular commercial HPLC. A modular system allows users to tailor the instrument to their needs and budget. The HP 1100 chromatograph equipped with an autosampler and a mass detector that allows continuous operation is shown (reproduced by permission of Agilent Technologies). Regulation of the temperature of the column greatly improves the reproducibility of the separation.

Behnke and Bayer published a similar approach for gradient elution PEC [51]. The schematic view is shown in Fig. 2.17. A gradient mixer and a HPLC pump were combined with a modular CE system. A post-injection splitter was used and sample introduced by a conventional HPLC six-port injector. A grounded stainless-steel T-piece was used to split both eluent and sample. The electrolyte reservoir on the inlet side of the separation capillary was connected to the splitter by a homemade interface. 

Abstract The determination of dichlorobenzene and naphthalene in commercial repellents used in Spain has been validated. This was done using an isocratic regime, to test the reverse -phase HPLC system with acetonitrile water 65 35 (v v) as the mobile phase, at 20 °C This technique is proposed for the modular validation of the HPLC... 

A simple and fast HP method for the determination of p-DB and N in mothrepellents manufactured in Spain has been validated. This was achieved by modular validation of the HPLC system. The results obtained show good agreement with the values provided by the manufacturers. 

Figure 4.2. Examples of modular and integrated HPLC systems. Modular systems (a) Agilent 1100 Series, (b) Jasco low-pressure mixing system. Integrated systems (c) Waters Alliance, (d) Shimadzu 2010.

Figure 3.1 Schematic of a modular HPLC instrument. A modular system allows users to adapt the Installation according to the applications to he carried out. The vertical assembly of the different modules affords an economy of space. Here the chromatograph, model HP 1200, comprises an auto-sampler that allows continuous operation and a thermostatically-controlled column to improve the reproducibility of the separations. (Reproduced courtesy of Agilent Technologies).

The LACCC and LAC experiments were conducted on a Hewlett-Packard (HP 1090) HPLC system using a diode array UV Detector and an evaporative light-scattering detector. SEC measurements were performed on a modular... 

Most HPLC systems have a modular design that provides flexibility and allows for many different combinations. In Fig. 2, the basic components of an HPLC are shown. In most miciofluidic HPLC systems, the column is miniaturized while the other compOTients are from a typical benchtop HPLC. 

Figure 1. Photograph and block diagram of a modem, automated modular HPLC analytical system (Kontron Instrumems-HPLC system 400). (1) The eluant delivery module (dual piston pumps) (2) sample application module (automated) (3) HPLC column module (4) analyte detector module (UV-VIS dual wavelength detector) (5) central control module (controls module 1 —4 and 6) (6) data output module (printer-plotter).

If a system comprises several modules, it is recommended that system tests be performed for parameters that are affected by multiple modules (holistic testing) rather than performing tests module by module (modular testing). Individual module tests should be performed if the parameter is affected by that module only (e.g., the wavelength accuracy of an HPLC variable-wavelength detector or the temperature accuracy of a column compartment). 

Furman et al. discussing the validation of computerised liquid chromatographic systems, present the concept of modular and holistic qualification. Modular qualification involves the individual components of a system such as pump, autosampler, column heater and detector of an HPLC. The authors make the point that ... 

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