Detector traces

In practice, the absence of some form of noise on a detector trace is unusual, particularly when high-sensitivity detection is employed. There are two components of noise, namely the short-term random variation in signal intensity, the noise level , shown in Figure 2.5(b), and the drift , i.e. the increase or decrease in the average noise level over a period of time. 

The analysis of organosulphur compounds has been greatly facilitated by the flame photometric detector [2], Volatile compounds can be separated by a glass capillary chromatographic column and the effluent split to a flame ionization detector and a flame photometric detector. The flame photometric detector response is proportional to [S2] [3-6]. The selectivity and enhanced sensitivity of the flame photometric detector for sulphur permits quantitation of organosulphur compounds at relatively low concentrations in complex organic mixtures. The flame ionization detector trace allows the organosulphur compounds to be referenced to the more abundant aliphatic and/or polynuclear aromatic hydrocarbons. 

Figure 10. A Plot of thickness vs time in developer derived from a laser end-point detector trace. The thickness change between maxima is a function of the laser wavelength and the index of refraction of the resist at that...

To experimentally determine the response factors A.., generally, the homopolymers of the components are monitored by the appropriate detector at several concentrations(62,65) The slope of the detector response (area under the appropriate SEC/detector trace) concentration (grams), which should be linear, is then the response factor A... 

In operation, the viscometer of Figure 2 will generate two separate signal detector traces for recording. The differential log-anplifier will generate a viscosity (In hi) trace vdiile the concentration detector will generate a concentration (c) trace. 

Detector traces for the removal of high-activity fission products in the wash step and elution of "Tc are shown in Figure 9.4. "Tc is present at much lower activities than the more abundant fission products that pass unretained through the column and detector flow cell. Nevertheless, during elution of the column with the 6 M HN03, the "Tc is readily seen in the vertically expanded inset. The SI separation procedure provided a decontamination factor of 104 for removal of 137Cs or 90Sr from the "Tc. 

In this radiometric detection approach, the detection limit could be lowered by using a stopped-flow procedure that captured 89% of the eluted "Tc within a 2.5-mL flow-through counting cell. Continuous-flow and stopped-flow detector traces are... 

FIGURE 9.5 Continuous- and stopped-flow detector traces for the automated SI separation Of "Tc(VII) on a TEVA-Resin column. (Adapted from Egorov, O. B., O Hara, M. J., Ruzicka, J., and Grate, J. W., Anal. Chem., 70, 977-984, 1998. Copyright 1998 Am. Chem. Soc. With... 

FIGURE 8 Displacement histogram and UV detector trace for a selective displacement process. (A) Displacement separation of a three-component protein mixture using streptomycin sulfate A as a displacer. Column 100 X 5 mm i.d. strong cation exchange (8 m) carrier 30 mM sodium phosphate buffer, pH 6.0 feed 1.6 mL of 0.392 mAI ribonudease A, 0.42 mM horse cytochrome c and 0.34 mM lysozyme in the carrier. Total column loading 12.7 mg/mL column displacer 25 mM streptomycin sulfate A flow rate 0.2 mL/min fraction size 200 /iL. (Kundu et al.43) (B) UV detector trace monitored at 280 nm for the displacement separation shown below. 

Figure 3. Simulated detector tracings from light-scattering, viscosity, and refractive index detectors for a narrow MWD polymer. (Reproduced with permission from reference 15. Copyright 1993 Elsevier)...

Figure 5. Light-scattering and refractive index detector tracings for a hypothetical MWD containing a small amount of high-molecular-weight material. (Reproduced with permission from reference 3. Copyright 1995 Marcel Dekker)...

SEC System. A Spectra Physics IsoChrom pump controlled the THE flow in the SEC part of the 2D instrument. Two SDV 5-jLtm SEC columns with 1000 and 10 A porosity (PSS) were used for size separation of the HPLC fractions. UV (SP 8450, Spectro Physics) and RI (Shodex SE 61, Diisseldorf, Germany) detection allowed lor conventional or multiple-detection data processing of detector traces. Eor the polyester analysis the SEC columns (50 and 100 A) were operated in acetone as eluent. 

The selectivity of the technique was measured by Feldman and Batistoni by chromatography of a silylized mixture of phenylarsonic acid, nonanoic acid, undecanoic acid and three aliphatic hydrocarbons. In each case a flame ionization detection trace was obtained simultaneously with the glow discharge detector trace. The selectivity of a given Si or As line was defined as the ratio of the peak height obtained per gram atom of carbon in the form of the interfering compound tested. 

By use of different detectors trace amounts of metals ranging from 10 to 10 g can be determined (Tables l.l/II, 1.2). Polyfluorinated 3-diketones as ligands give more highly volatile derivatives and above all allow the use of the electron capture detector (ECD) which has low detection limits for fluorinated compounds. Nevertheless decompositions can also appear in this class of substances. In addition thioketones and amino derivatives are used as chelating agents for quantitative gas-chromatography. 

A few examples of where it is possible are the following Use of a refractive index detector, trace analysis of related substances (impurities) in pharmaceutical products, with UV detection at very low wavelength, when the accuracy of the result is of little interest [1] (e.g., when chromatography is used to monitor a chemical reaction), and when a relative value is enough. In this situation, the simplified relationship (3) is sufficient, but the analyst must not forget that the proportions found in this way are not the true proportions. 

Figure 6.3. Example chromatograms of two target compounds isolated by the high-throughput purification system shown in Figure 6.2. Chromatograms illustrate the performance of fast gradient analysis (ELSD and UV detector trace before purification). Reprinted with permission from reference 12.

FIGURE 7.7 Didactic representation (upper) and flow diagram (lower) of a flow system with zone trapping relying on the use of an injector-commutator. S = sample R = reagent C = sample carrier stream L = sampling loop IC — injector-commutator Rc = coiled reactor D = detector traced line = alternative Rc position shaded area — alternative IC position solid arrows = sites where pumping is applied. 

Comparison of Grades of CMC. The Isotachopherograms of four grades of CMC with nominal DS of 0.7 examined by ITP for differences in substitution are shown In Figure 2. The detector traces show that differences in distribution exist unong the grades although the major portion of each sample has the same mobility and, consequently, a slmll u DS. 

Figure 3. Detector traces illustrating equilibrium Tc sensing using Tc standards in 0.02M nitric acid. The sample volume is 100 mL flow rate is 1 mUmin. Plateau response region corresponds to attainment of equilibrium conditions between the sensor column and sample solution.

The tandem PID/FID combination detector system is available commercially and incorporates the photoionization and flame ionization detectors. With both detectors in tandem, dual detector traces for benzene, toluene, ethyl benzene, and xylenes are possible, eliminating the need for two sepa-... 

Figure 8.37 shows the normalized response (based on chloride peak height) for the conductivity versus the charge detector trace. With charge detection, weak acids such as fluoride, acetate, and oxalate as well as multivalent ions... 

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