Solvents for liquid chromatography

Some fairly broad generalizations can be made about the selection of certain preferred solvents for liquid chromatography from the relatively large number of liquids that might be employed as solvents. A suitable solvent will preferably have a low vi jslty, be compatible with the detection system, be readily available in a pure form, and if possible, have a low flammability and toxicity. Since detection in HFLC occurs on-line,... 

Modes of Liquid Chromatography Solvents for Liquid Chromatography Instability of HPLC Solvents... 

The ideal situation for a process analyzer is to have the detector/electrical components in an area physically isolated from the sample stream and any liquid components required for calibration or instrument operation (e.g., solvents for liquid chromatography or gel-permeation chromatography). In this arrangement, isolation of the electrical components ensures that a spark source or hot surface (such as a spectroscopic light source) will not cause a problem with flammable components (both sample stream components and solvents). Also, this isolation wiU limit instrument damage in case of a sample system leak or solvent leak. Although the ideal situation is often not realized in a practical application, one should make every effort to protect the delicate sections of the instrument. In one application of the authors, a fiber optic probe having a quartz window sealed on the end of the probe was installed in the reactor of a process that contained... 

Solvents for Liquid Chromatography 78 Ed. Removed data included in other tables on solvents... 

Radiative Transition Probabilities for X-Ray Lines Radioactive Tracer Diffusion Data for Pure Metals Recommended Daily Dietary Allowances Reduction of Barometer to Sea Level Refractory Materials Resistance of Wires Resistivity of Semiconducting Minerals Solvents for Liquid Chromatography Spark-Gap Voltages... 

Physical properties of some common solvents for liquid chromatography... 

Figure 4 Apparatus for solvent purification by frontal chromatography 1, glass column with cooling jacket 2, glass sinter 3, silica gel or alumina adsorbent 4, siphon-type injector 5, container for unpurified solvent 6, PTFE tube 7, moisture trap 8, valve 9, container for purified solvent. (Reproduced with permission from Buszewski B, Lodkowski R, and Trocewicz J (1987) Purification of solvents for liquid chromatography. Journal of High Resolution Chromatography and Chromatography Communications 10 527-528.)...

Properties of solvents for liquid chromatography including miscibilities... 

The solvents used for liquid chromatography are the commoner ones such as water, acetonitrile, and methanol. For the reasons just stated, it is not possible to put them straight into the ion source without problems arising. On the other hand, the very viscous solvents that qualify as matrix material are of no use in liquid chromatography. Before the low-boiling-point eluant from the LC column is introduced into the ion source, it must be admixed with a high-boiling-point matrix... 

For liquid chromatography, a sample of the mixture solution is injected through a loop injector which allows a quantity of the solution to be placed in a small tubular loop at atmospheric pressure. By manipulating a valve, the high-pressure flow of solvent to the column is diverted through the loop, carrying the sample with it (Figure 35.5). 

The packing material for liquid chromatography is produced from styrene and divinylbenzene dissolved in 50 to 300% by weight of organic solvent to both monomers. The constitution of divinylbenzene in the monomer mixture is not less than 60% by weight. In gel-permeation chromatography, the exclusive molecular weight is not less than 1 X 10 in terms of standard polystyrene (79). 

The //PLC system described in this chapter is equipped with 24 parallel columns for liquid chromatography, each with its own sample introduction port and exit port for connection to detectors of choice (UV absorbance and/ or fluorescence). Flow from a binary solvent delivery system is divided evenly across 24 channels and results in 1/24 of the programmed pump flow rate through each column (i.e., total flow of 300 /zL/ min will produce a flow of 12.5 /zL/ min in each column). Samples are introduced to the columns by a multichannel autosampler configured to sample from either 96-or 384-well SBS standard plates. Figure 6.2 depicts a general view of the system. 

Sample preparation for analysis by hyphenated methods requires some additional planning when compared to nonhyphenated methods. All steps, extraction, concentration, and final solvent selection must take into consideration and be compatible with all the components of the hyphenated instrumentation. For gas chromatographic methods, all the components in the mixture must be in the gaseous state. For liquid chromatography (LC) or high-performance liquid chromatography (HPLC), the samples of the analytes of interest can be solids or liquids, neutral or charged molecules, or ions, but they must be in solution. If the follow-on analysis is by MS, then each of the analytes may require a different method of introduction into the MS. Metals and metal ions may be introduced by HPLC if they are in solution but commonly are introduced via AAS or inductively coupled plasma (ICP). Other analytes may be directly introduced from HPLC to MS [2],... 

Like dissolves like is the basic concept for the selection of solvents in the eluent for liquid chromatography. Controlling the solubility of analytes is the key to success. If the selected solvent or mixture of solvents does not interfere with detection, it is a good eluent. The selection of a suitable solvent for low-wavelength absorption detection and post-column derivatization detection is important to obtain highly sensitive detection. The selection of a volatile solvent is the key for preparative-scale liquid chromatography and for mass spectro-metric detection. 

Future developments that may facilitate ocean measurements from vessels or buoys include miniaturization of chromatographic equipment (so less solvent is needed per analysis), new solvent transport systems, such as electrokinetic transport, to reduce power requirements on the pumps, and more sensitive detectors for liquid chromatography. Certain combinations of very short columns and flow injection analysis are also promising for real-time studies. 

Bean, M. F., Pallante-Morell, S. L., Dulik, D. M., and Fenselau, C. (1990). Protocol for liquid chromatography/mass spectrometry of glutathione conjugates using postcolumn solvent modification. Anal. Chem. 62 121-124. 

For liquid chromatography separation to take place, samples or sample extracts must be miscible with the mobile phase. The separation is possible due to specific interactions between the analyte molecules and the mobile and stationary phases. To decrease the time of analysis, gradient elution is applied, with the polarity of the mobile phase solvent increasing through analysis time. Up to four solvents of different polarities may be mixed to achieve the fastest and the most complete separation. 

Organic solvents used for liquid chromatography were from OmniSolv (MCB Manufacturing Chemists, Tnc., Cincinnati, OH) and water was distilled, deionized and filtered through a 0.2u nylon 66 membrane (Rainin). All chemicals with no source identified were of reagent grade. 

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