Total solvent consumption

Concentration using aCi8 SPE Continuous-flow (methanol), high-temperature (65°C), sonicated extraction system to isolate APEO metabolites from sediment samples (low-power ultrasonic energy) sediment extraction was complete after 7 min with a total solvent consumption of 3.5 ml/sample two-step cleanup, normal-phase SPE, reversed-phase... 

Additionally there are fused-silica columns with i.d. ca. 0.2 mm. Representing all other small-bore techniques, Fig. 22.1 illustrates the performance of micro-HPLC using this kind of column. Fifteen bile acids which are vital to any assessment of possible liver disease were identified in body fluids. The total solvent consumption of 210 pi, the ability to mix a gradient in this small volume and reproduce it and the refined reaction detector already described in Section 19.9 are special features of this particular system. The following abbreviations are used UDC = ursodeoxycholic acid C = cholic acid CDC = chenodeoxycholic acid DC = deoxycholic acid LC = lithocholic acid G (prefix) = glycine conjugate T (prefix) = faurine conjugate. 

The total solvent consumption results from a mass balance over the entire cascade. If no solvent reflux from the extraction separation unit is fed back, (Fig. 6-24) it is... 

Most recently (Schneider 2006) an experimental source was used to conduct studies under conditions of total solvent consumption , with pneumatically assisted nebu-lization to stabilize the ESI process, a heated laminar flow chamber to enhance desolvation and ion production, and various atmosphere-to-vacuum aperture diameters to maximize ion transfer. The motivation for these experiments was to investigate the proposal that the reason for the much lower ionization sampling efficiencies at higher flow rates ( o,L.min and above) is that the electrosprayed droplets are much larger in view of the much larger ESI needle tip diameters required to maintain flow rates in this regime, and thus are much less efficiently evaporated down to the Rayleigh and/or ion evaporation limits than the droplets formed from the 1 (tm diameter tips nsed in nano-ESI (Juraschek 1999 Schmidt 2003). 

Figure 5.39 Modified nanoelectrospray source used to study ionization sampling efficiencies under conditions of total solvent consumption . The inset shows the modified curtain gas and heated laminar flow particle discriminator interface with the nebulizier assisted nano-ESl arrangement. Reproduced from Schneider, Rapid Commun. Mass Spectrom. 20, 1538 (2006), with permission of John Wiley Sons, Ltd.

There has been a great deal of discussion of matrix effects on ionization efficiency in previous chapters, particularly Section 5.3.6a. (Not being discussed here is matrix interference , i.e. direct contributions from matrix components to the analytical signals in the SIM or MRM channels used to monitor the analyte and SIS these interferences are easily detected in analyses of extracts of control matrix or incurred sample). Suppression of ionization efficiency by co-eluting matrix components is the more common, but enhancement is also observed (Section 5.3.6a). While it is true that operating under conditions of total solvent consumption , e.g. by using very low flow rates for ESI combined with additional heating, can reduce matrix... 

Dyes, Dye Intermediates, and Naphthalene. Several thousand different synthetic dyes are known, having a total worldwide consumption of 298 million kg/yr (see Dyes AND dye intermediates). Many dyes contain some form of sulfonate as —SO H, —SO Na, or —SO2NH2. Acid dyes, solvent dyes, basic dyes, disperse dyes, fiber-reactive dyes, and vat dyes can have one or more sulfonic acid groups incorporated into their molecular stmcture. The raw materials used for the manufacture of dyes are mainly aromatic hydrocarbons (67—74) and include ben2ene, toluene, naphthalene, anthracene, pyrene, phenol (qv), pyridine, and carba2ole. Anthraquinone sulfonic acid is an important dye intermediate and is prepared by sulfonation of anthraquinone using sulfur trioxide and sulfuric acid. 

Another critical instrument specification is the total extra-column dispersion. The subject of extra-column dispersion has already been discussed in chapter 9. It has been shown that the extra-column dispersion determines the minimum column radius and, thus, both the solvent consumption per analysis and the mass sensitivity of the overall chromatographic system. The overall extra-column variance, therefore, must be known and quantitatively specified. 

The cyclic steady state SMB performance is characterized by four parameters purity, recovery, solvent consumption, and adsorbent productivity. Extract (raffinate) purity is the ratio between the concentration of the more retained component (less retained) and the total concentration of the two species in the extract (raffinate). The recovery is the amount of the target species obtained in the desired product stream per total amount of the same species fed into the system. Solvent consumption is the total amount of solvent used (in eluent and feed) per unit of racemic amount treated. Productivity is the amount of racemic mixture treated per volume of adsorbent bed and per unit of time. 

The use of robotics can be adopted also in sample preparation steps, in particular on-line SPE [7], This necessity is particular evident when small quantity of starting materials is available and the target molecules are present at low concentration levels. With the advent of miniaturization and automated procedures for samples handling, treatments and analysis, the lost of analytes due to a laboratory steps can be reduced. The reduction of analyte losses and the possibility to analyze even a total sample (no loss) leads to lower limits of detection (and consequently lower limits of quantification). Smaller volumes bring to obtain adequate sensitivity and selectivity for a large variety of compounds. In addition, on-line SPE requires low solvent consumption without the need to remove all residual water from cartridges, since elution solvents are compatible with the separation methods. 

The analytical specifications must prescribe the ultimate performance of the total chromatographic system, in appropriate numerical values, to demonstrate the performance that has been achieved. The separation of the critical pair would require a minimum column efficiency and the number of theoretical plated produced by the column should be reported. The second most important requisite is that the analysis should be achieved in the minimum time and thus the analysis time should also be given. The analyst will also want to know the maximum volume of charge that can be placed on the column, the solvent consumption per analysis, the mass sensitivity and finally the total peak capacity of the chromatogram. The analytical specifications can be summarized as follows. 

Operating hours Charges cleaned Tonnage cleaned Solvent for recycling Net solvent consumption Total stabiliser consumption Energy consumption... 

As we discuss in the next section, the amount of solvent consumed per unit amount of purified product prepared is an important contribution to the total cost of production in many cases. The amount of solvent used during a cycle is the product of the cycle time and the flow rate. The amoimt produced per cycle is the product of the amount injected and the recovery yield. Thus the solvent consumption is given by... 

The solvent and energy costs are proportional to the production rate. Their contribution to the total product costs will be minimized by maximizing the specific production, i.e., by minimizing the ammmt of solvent needed to produce a unit amoimt of final product. The operating costs are proportional to the cost of the solvent (SC), the production rate, and the solvent consumption (CSj). Hence, it is inversely proportional to the specific production, and... 

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