Separation Sequential analysis

Figure 12.11 Coupled SEC-RPLC separation of compound Chemigum mbber stock (a) SEC ti ace (b) RPLC trace of fraction 1, dibutylphthalate (c) RPLC trace of fraction 2, elemental sulfur. Coupled SEC conditions MicroPak TSK 3000H (50 cm) X 2000H (50 cm) X 1000 H (80 cm) columns (8 mm i.d.) eluent, THE at a flow rate of 1 mL/min UV detection at 215 nm (1.0 a.u.f.s.) injection volume, 200 p-L. RPLC conditions MicroPak MCH (25 cm X 2.2 mm i.d.) column flow rate, 0.5 mL/min injection volume, lOpL gradient, acetonitrile-water (20 80 v/v) to 100% acetonitrile at 3% acetonitrile/min UV detection at 254 nm (0.05 a.u.f.s.). Reprinted from Journal of Chromatography, 149, E. L. Jolmson et al., Coupled column cliromatography employing exclusion and a reversed phase. A potential general approach to sequential analysis , pp. 571-585, copyright 1978, with permission from Elsevier Science.

A sequential analysis protocol includes three steps (1) extraction in water or other appropriate solvent for the colorant, (2) purification or concentration of the colorant, and (3) separation coupled with detection of the target molecule. Different methods of extracting synthetic colorants from foods have been developed using organic solvents followed by SPE protocols using as adsorption support RP-C18, amino materials, or Amberlite XAD-2. Eor qualitative evaluations, the easiest option for separating colorant molecules from unwanted ingredients found in an extract is SPE on polyamide or wool. 

Exclusion chromatography is also useful in the separation of small molecules from interfering matrices of larger molecules, for example in foods or other samples of biological origin. It can be used as the first step in the sequential analysis of complex unknown organic mixtures, which are first separated on a size basis by exclusion, then the collected fractions can be further separated by normal or reverse phase chromatography, where the separation is based on chemical differences. 

Egorov, O. B., O Hara, M. J., Farmer, O. T., Ill, and Grate, J. W., Extraction chromatographic separations and analysis of actinides using sequential injection techniques with on-line inductively coupled plasma mass spectrometry (ICP MS) detection, Analyst, 126, 1594-1601, 2001. 

Sample calculations in reports, 462 Saran, 437, 440-442 Sawing for equipment fabrication, 447 Scale formation in evaporators, 355-360 Scaling for equipment cost estimation, 169-171 Scaling factors for heat transfer, 586-587 Scale-up for equipment specifications, 36-39 Schedule number for pipe, 493 Screen, cost of 567 Self insurance, 264-265 Sensitivity of results for pipe sizing, 367-368 Separators, cost of 559-561 Sequential analysis, 771-772 Series compound-amount factor, 227... 

Various types of column can be combined. Sequential analysis with liquid chromatography can first pass the sample through a gel to separate constituents according to their molecular size, followed by some form of affinity chromatography using partition or adsorption. A two-column GLC system for steroid analysis has been described (H22), in which the sample is first introduced to a high-capacity low-resolution column for a preliminary separation. After a suitable time, the flow of gas is re-... 

X-ray fluorescence spectroscopy is a widely used analytical method for automated sequential analysis of major and trace elements in metals, rocks, soils, and other usually solid materials. The advantage of this method is that no separation is necessary. The sample is irradiated with an x-ray beam that causes secondary fluorescence in the sample that can be measured at a certain wavelength to determine the concentration of the element in the sample [92]. However, methods that do not require separation before analysis have a drawback in common interelemental effects. 

The Stepwise SPC Chart is a method that combines the functions of the CUSUM Chart and the Shewhart Control Chart. A sequential analysis is used to estimate the current mean of the process. Shewhart Control Charts are then constructed about the step functions representing the current mean. Figure 1 illustrates the Stepwise Control Chart. The step functions, based on sequential analysis, respond to process drift the same way as the CUSUM Chart. Each segment of the control chart then helps to identify the interruptions, in the same way as the Shewhart Control Chart does. With the proper choice of parameters, the Stepwise SPC Chart can effectively separate the three types of variations drift, fluctuations and interruptions, and thus help us to monitor and analyze the quality of the product. Refer to EWMA Chart. 

Separation of phenylthiohydantoin (PTH) amino acid derivatives, which are produced in the sequential analysis of proteins by the Edman degradation, is required. Ashraf-Khorassani etal. showed [21] how SFC on a cyanopropyl-modified silica column allowed the separation of more than twenty PTH-amino acids if an ion-pairing reagent (tetramethylammonium hydroxide) was present at low concentration in the methanol-modified CO2 mobile phase. 

The second is to heartcut successive or desired fractions into a range of parallel traps (Figure 4D) over the course of the development of the separation, and then elute the contents of each of the traps into the column as discrete events. Note that the above two methods involve discrete or sequential analysis of the selected heartcuts under essentially... 

Automated radioanalytical chemistry can provide near real time monitoring of reprocessing plant operations (O Hara et al. 2009). A sequential injection chromatography system for the separation and analysis of Am, Pu, and Np isotopes is integrated in a modular system that automates the complete sample analysis process, from initial sample preparation to final data reporting. 

The sequential analysis of alkaline-earth metals, which elute in the order Mg " < Ca " < Sr < Ba on strong acid cation exchangers, can also be performed using both conductivity detection modes. An eluent mixture of hydrochloric acid and 2,3-diaminopropionic acid is used for suppressed conductivity detection ethylenediammonium ions are suitable for nonsuppressed conductivity detection. Figure 4.56 shows a separation of alkahne-earth metals on Shimpack IC-Cl obtained with this eluent Because of the high elution power of the mobile phase, all monovalent cations present in the sample are eluted as one peak within the void volume of the column. As an alternative to strong eluents, shorter separator columns may be employed to reduce the retention of cations that have high affinities toward the stationary phase. 

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