Extraction sequences

When extracting sequence information from mass spectra, not only is the m/z value at which the ions occur of importance since these provide an indication of the amino acid composition of the peptide giving rise to the ion, but so is the mass difference between adjacent ions. This indicates the particular amino acid residue that has been lost and thus provides the sequence information required. The mass differences arising from each of the amino acids are shown in Table 5.6. 

The pulp and paper industry is the largest industrial process water user in the U.S.5 In 2000, a typical pulp and paper mill used between 15,140 and 45,420 L (4000 to 12,000 gal) of water per ton of pulp produced. 1 2 3 4 General water pollution concerns for pulp and paper mills are effluent solids, biochemical oxygen demand (BOD), and color. Toxicity concerns historically occurred from the potential presence of chlorinated organic compounds such as dioxins, furans, and others (collectively referred to as adsorbable organic halides, or AOX) in wastewaters after the chlorination/ extraction sequence. With the substitution of chlorine dioxide for chlorine, discharges of the chlorinated compounds have decreased dramatically. 

TABLE 6.3. BCR Extraction Sequence for 1 g of Soil. Extraction is at Room Temperature Unless Otherwise Noted11... 

Step 1 simulates the readily available soil fraction, steps 2-4 indicate potentially available soil fractions, and step 5 yields the unextracted residue and completes the mass balance. Note that the solvent used becomes inaeasingly nonpolar during the extraction sequence. Summary data for the she studied compounds are presented in Fig. 8.48. 

Sample The standards are created with a plasma originally possessing no cyclosporin. Six different solutions are prepared by adding the necessary quantities of cyclosporin A to each in order to create solutions of 50 ng/ml, 100 ng/ml, 200 ng/ml, 400 ng/ml, 800 ng/ml, and 1000 ng/ml. 1 ml from each of these solutions is subjected to the same extraction sequence following the addition of 250 ng of cyclosporin D to each, as above. 

A comparative study was conducted by cleaning XAD-2 resin by ultrasonic and Soxhlet extraction procedures. Two batches of XAD-2 resins from the same lot of uncleaned resin were cleaned by backwashing with water and then were subsequently extracted with methanol, acetonitrile, and methylene chloride. The solvent-to-resin volume ratio for both methods was 5 1. The volumes of wet resin for the Soxhlet extraction and the ultrasonic bath were 100 mL and 50 mL, respectively. The ultrasonic cleaning procedure was done in a Teflon-lined screw-cap amber jar (250 mL) for 1 h in each solvent. The Soxhlet extraction sequence was 24 h in methanol, 24 h in acetonitrile, and 48 h in methylene chloride. 

The examination of alternative solvent extraction sequences in this experiment, Aliquot A versus E, showed the sequence from nonpolar to polar solvent to be more efficient in extracting mutagens from the sample (Table II). This result could explain the lower recoveries of mutagenic activity via the modified Hites procedure compared with the recoveries found with the milling procedure (Table I). The published Hites method (18, 19) was used in this study, that is, extraction with isopropyl alcohol followed by benzene. Therefore, the results from our experiment suggest that a nonpolar to polar solvent sequence gives better recoveries of mutagenic components from a sample. 

Table 2.2. Extraction sequences for the subdivision of the total metal content of soils...

According to these results, a recommendation was made to conduct the AIX separations in pure HC1 or HF solutions to try to observe the predicted sequence, Equation 32. Accordingly, the amine separations of the group-5 elements were systematically redone by W. Paulus et al. [177]. The reversed extraction sequence Pa > Nb > Db > Ta has been established exactly as theoretically predicted. That was the first time when predictions of extraction behavior of the heaviest elements based on quantum-chemical calculations were made, and also confirmed by specially designed experiments. 

The proximity in the Db behavior in the TiOA experiments to that of Pa was the reason for performing a series of extractions of Db into diisobutyl-carbinol (DIBC), a secondary alcohol which is a very specific extractant for Pa. The extraction from concentrated HBr solution in ARC A II was followed by the elution of a Nb fraction in 6 M HC1/0.0002 M HF, and of a Pa fraction in 0.5 M HC1. The number of 262Db decays observed in the Nb fraction indicated that less than 45% of the Db was extracted into DIBC, and the extraction sequence Db < Nb < Pa was established [46]. This suggests that the seeming similarity between Db and Pa concluded from the TiOA experiments is not a general phenomenon. 

Because phenol (CeHsOH) is less acidic than a carboxylic acid, it can be deprotonated by NaOH but not by the weaker base NaHCOa- Using this information, write out an extraction sequence that can be used to separate CeHsOH from cyclohexanol. Show what compound is present in each layer at each stage of the process, and if it is present in its neutral or ionic form. 

Rf (production cross section a k 5nb). Volatilities were found to be RfCl4 ZrCU > HfCU, and RfBr4 > HfBr4. Experiments with the automatic HPLC apparatus ARCA indicated similar behaviour of Rf and Th in HF solutions. The extraction sequence is Zr > Rf > Hf, and the distribution coefficients are approximately the same for Rf and Hf This proves the predicted inversion of the trend in the properties from the 5d to the 6d elements. Further experiments with Rf are in progress by use of Rf, produced by the reaction " Cm( Ne, a3n) Rf... 

A typical extraction sequence is similar to the traditional SPE, although 500 pL of the appropriate solvent is sufficient for disk conditioning and extraction of the analytes. Several types of disk extraction media are commercially available in different dimensions depending on the application and sample volume. The most prevalent are paper-based, membrane-based, glass fiber-based, and PTFE-based products. Commercially available products are Speediscs by Baker, Empore by 3M, Novo Clean by Alltech, and SPEC by Ansys Technol. 

Also selective extractions were carried out in order to obtain information about solid speciation of the elements. The results (Table 8.4) show that the metals concentration in the adsorbed, carbonade, organic and sulphide fractions are in the natural range. The values also show that the extraction sequence is, in general, in the order ... 

In the frame of the REHE project, the amine extractions of the group 5 elements were systematically revisited by Paulus etal. (1999). Pershina (1998b), by considering the competition between hydrolysis and halide complex formation, predicted the extraction sequence... 

Figure 6.5 Distribution coefficients of Pa, Nb and 7k in the system Aliquat 336/HO. The K for Db in 6 M HQ is also indicated. The system shows the inverse extraction sequence as compared with the TiOA/HCl/HF system as theoretically predicted. Reproduced with permission from Paulus et al. (1999). 1999 R. Oldenbourg Verlag.

The figure on the patent face page shows the flow sheet for the process. The left hand side of the flow chart shows the extraction sequence, and the right hand side, specifically, exuaction column and associated pumps and heat exchangers, the solvent-organic separation. By now the extraction side should be quite familiar. 

In connection with the problems arising from the disposal of solid wastes, particularly of dredged materials, extraction sequences have been applied which are designed to differentiate between the exchangeable, carbonatic, reducible (hydrous Fe/Mn oxides), oxidizable (sulfides and organic phases) and residual fractions (Engler et al., 1977). One of the more widely applied extraction sequences of Tessier and coworkers (1979) has been modified by various authors a version of Ker-sten Forstner (1986) differentiates easily and moderately reducible components (Table 3-4). 

---