Column fast analysis

A major disadvantage of gradient elution in terms of fast analysis remains the time to adequately equilibrate the chromatographic column between two experiments. However, Carr et al. recently demonstrated an excellent repeatability ( 0.002 min in retention time) obtained with two column volumes of re-equilibration instead of the usual 10 column volumes when a small amount of ancillary solvent (1-3% of 1-butanol or 1-propanol) is added to the mobile phase [45, 58]. 

Figure 1.15 Fast analysis of a test mixture on a 10 cm x 4.6 mm I.D. column packed with 3 micrometer octa< ecylsilanized silica with a mobile phase flow rate of 3.4 mi. i.n (acetonitrile-water 7 3) and operating pressure of ca. 340 atmospheres. Peaks 1 uracil, 2 phenol, 3 - nitrobenzene, 4 - toluene, 5 -ethylbenzene, 6 - isopropylbenzene, and 7 - tert.-butylbenzene. (Reproduced with permission from ref. 222. Copyright Friedr. Vieweg 6 Sohn).

Zeng H., Deng Y., and Wu J., 2003a. Fast analysis using monolithic columns coupled with high-flow online extraction and electrospray mass spectrometric detection for the direct and simultaneous quantitation of multiple components in plasma. J Chromatogr B 788 331. 

FIGURE 14.3 Fast analysis of control drugs and metabolites using a 15 cm x 300 fim inner diameter capillary column packed with 3 /tin C18 particles (Micro-Tech Scientific MC-15-C18SS-320-EU) operated at 10 /tL/min gradient flow rate. UV at 278 nm. (Source Drug Enforcement Administration, Southwest Laboratory, Vista, California and S. DiPari.)... 

This instrument features five detectors (Table 1.7). In the flame ionization detector, the high-speed electrometer, which ensures a very low noise level, is best suited to trace analysis and fast analysis using a capillary column. 

The relationships between Rs, a, and N are given in Figure 5.4. When a is small, a large N is required for a good separation. However, the use of a longer column should be avoided for fast analysis even if a longer column provides excellent plate numbers. An improvement in the value of a can be estimated for a good separation. 

Hoke et al. [60] demonstrated fast analysis of ultratrace drugs in biomatrixes using packed column SFC tandem mass spectrometry (SFC/MS/MS). Compared to an LC-MS/MS method, the SFC separation provided a roughly threefold reduction in... 

Each fragment is focussed and pulsed to column 2 for fast analysis. Because modulation is a mass-conservative process, the peak height increases to accommodate the reduction in peak width thus, greater analytical sensitivity is obtained. Provided that column 2 can resolve the substances focussed by the... 

The use of supercritical fluid chromatography for carotene separation has been examined and optimized, especially in regard to temperature, pressure, and organic modifiers in the supercritical fluid (71). With an RP column it was possible to resolve an a-carotene-cis isomer from an all-trans carotene as well as two cis isomers of /3-carotene from an all-trans /3-carotene. As with HPLC, only polymeric C,8 columns were able to resolve the cis isomers of a- and /3-carotene from the all-trans isomers. Supercritical fluid chromatography offers the advantage not only of an efficient separation but also of fast analysis. Indeed, the use of SFC with ODS-based columns for the analysis of carotenoid pigments affords a threefold reduction of analysis time compared to HPLC (72). The elution order of carotenoids and their cis isomers was found to be the same as in RP-HPLC. The selectivity of the system could further be increased by adding modifiers (e.g.,... 

Veuthey, J. L., Souverain, S., and Rudaz, S. (2004). Column-switching procedures for the fast analysis of drugs in biologic samples. I her. Drug. Monit. 26 161-166. 

An oven temperature in the range of 200°C and detector and injector temperatures around 300°C and 250°C, respectively, should give good separation, sharpness of peaks, and fast analysis time. Electron capture detector (ECD) is the most commonly used detector for trace level analysis of PCBs by gas chromatography (GC), exhibiting a response to an amount below 0.1 ng PCBs. Thus, on a capillary column, an IDL in the range of 5 pg/L can be achieved. With proper sample concentration steps, a detection level several-fold lower to IDL may be obtained. Other halogen-specific detectors such as Hall electrolytic conductivity detector can also be used to analyze PCBs. 

Cough Syrup Ethinamate HPLC Fast analysis column (bio Rad) RI See USP 23 [5] for GC methods [661] [462]... 

Figure 8. Fast analysis of proteins. Column Hy-Tach micropellicular C-18 silica, 30x4.6mm eluent A, 0.1% (v/v) TFA in water, eluent B, 95% (v/v) ACN in water containing 0.1% (v/v) TFA flow rate, 4.0 ml/min. temp., 80°C. Initial column inlet pressure, 260 bars sample, 15 pi of a mixture containing =1 pg each of ribonuclease A (1), cytochrome C (2), lysozyme (3) and P-lactoglobulin A (4). Elution was carried out with a gradient 20 to 50% B in 0.5 min and return to starting conditions in 0.1 min. The dotted line represents gradient profile of ACN. The analysis was carried out with the house built protein analyzer described under Figure 7.

In the reality of LC practice, eqn.(4.38), which is based on a different optimum particle size for a different required number of plates, will not usually be realistic. For LC the truth may be somewhere in between the two extremes described by eqn.(4.36) (constant flow rate and particle size) and eqn.(4.38) (constant pressure drop). Relatively long columns with 10 pm particles may be used for difficult separations, requiring relatively large numbers of plates. For more convenient separations, somewhat shorter 5 pm particle columns may be used, and for relatively simple separations requiring modest numbers of plates 3 pm particles packed in very short columns may provide fast analysis. 

If the required number of plates is moderate (say several thousands), then short capillary columns may be used to provide fast analysis of the sample. The required column length and retention time can easily be calculated from eqns.(7.3) and (7.6). For example, if we operate a capillary column with a diameter of 200 pm at a reduced velocity of 5 with a reduced plate height of 1.5, then 2000 theoretical plates require a column with... 

TLC is the more popular of the two planar techniques. It is used for fast screening of mixtures and for surveying methods for use in columns. Quantitative analysis is better accomplished by column LC, but quantitative TLC is increasing in popularity as the instrumentation improves. Table 4 contains a summary of the advantages and disadvantages of the planar methods. 

The properties of the column are as follows Hewlett-Packard HP 5790A, 12 m x 0.2 mu cross-linked methyl silicone (fast analysis) column, programmed from 35 to 140°C at 3°C/min. 

Wernly P, Thormann W (1991) Analysis of illicit drugs in human urine by micellar electrokinetic capillary chromatography with on-column fast scanning polychrome absorption detection. Anal Chem 63 2878-2882. 

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