Ultra-pure water extraction

Ultra-pure water extraction and bulk metal analysis results for a grade of PVDF can be seen in Tables 15.13 and 15.14. Important elements such as calcium, iron, potassium, and sodium are missing from the data in Table 15.13. 

Combine a 50-g soil sample with 200 mL of ultra-pure water in a 500-mL round-bottom flask. Seal and shake the mixture vigorously for 2 min. Measure the pH to ensure that the pH of the mixed solution is between 6 and 8. Connect the flask to a water-cooled condenser (ca 30-cm height) and reflux the mixture for 2 h. Cool the solution and transfer >100mL of the extract to a centrifuge tube of sufficient size. Centrifuge the extract for 15 min at 3500 rpm. Save a 100-mL aliquot portion of the supernatant for further cleanup. Adjust the pH to 6-8 with phosphate buffer (pH 7) if needed, add 1 mL of methanol to the extract aliquot portion and shake the solution well. 

Blank values. Ihe overall blank values of the analytical method, from weighing of the specimen to the prepeuation of the sample, are mainly caused by the added reagents, Le., the buffer solution, acids and bases, the dithiodicarbamate and, last but not least, the ultra-pure water if used instead of seawater for dilution or for the determination of the blank values. If no water of sufficient purity (ultra-pure water) is available, seawater extracted with Na-DBDTC is an accetable substitute. The use of reference seawater is another option (c.g., NASS and CASS reference material see Section 12.1.6). The blanks are derived firom the difference between the certified and the measmed values and should result in the same (similar) blank values from different reference materials. Typical blank values for Fe have been found to be between 100 and 150ng/L, for Zn between 60 and 90 ng/L, and for Cd and Pb below 10 ng/L. Variations depend on the stocks of chemicals employed. In particular the... 

As an alternative to the extraction procedure described above, small components can be sealed into a double-layered plastic bag made of polypropylene/ polyethylene together with 100 mL of ultra-pure water (SEMI standard method G52-90) and heated in a water bath to 95 °C for 30 minutes. After cooling it... 

Fluid handling systems and ultra-purity water (UPW) systems are flushed with UPW, acids, or bases to extract ions and remove the loose particles from surfaces. Diluted hydrofluoric acid is effective in leaching out metals from fluoroplastics. Ultra pure water removes anions and particles. It is not unusual to flush a system with several hundred liters of water. 

Resins and parts have been extracted with acids, such as nitric, hydrofluoric, and hydrochloric, and ultra-pure water at room or elevated temperatures for a period of a few hours to several days by both static and dynamic methods. A solvent such as/-propanol is usually added to the aqueous phase to improve the wetting of the fluoropolymer surface. Anions and TOC are extracted in ultra-pure water. Most of the available data are based on the static extraction method. 

SEMI has recently released provisional specifica-tions ] for particulate, anionic, and metallic contamination in parts. Specifications for particle release are not included in this document and are yet to be determined. Metallic extractables are based on leaching in ultra-pure water. Section 3.7 of this specification states that " The relative leach-out performance of polymer components in actual use with other chemicals (e.g., acids and bases) cannot be directly derived by using the UPW data. It is incumbent upon the user to determine if a component is suitablefor use based on these requirements. " For all practical purposes, the utility of the new SEMI specification is limited to ultrapure water. Table 15.6 shows a comparison of extraction/ leaching results (ICP-MS) for wet-bench plastics in different acids and ultra-pure water. The amounts of metals leached out of plastics by different fluids vary significantly hydrofluoric acid extracts 10-500 times more metal than nitric acid. 

Table 15.15 gives the metal extraction data for a filter cartridge that is a common device in the chemical distribution and ultra-pure water systems in fabs. The filter media is a PTFE membrane and the hardware is made of high-purity PFAt ] Two eonsecutive extractions were conducted in high-purity hydrochloric acid, each for the duration of 16 hours, followed by ICP-MS measurement of the metal eontent of the acid. The second extraction shows a decrease in the metal contamination, which is typical of most devices. Fluid handling components are flushed with relatively large volumes of acids and/or UPW to remove most of the extractable contaminants. 

Table 15.10. Detection Limit of Purity Tests for Extraction by Ultra-pure Water ...

Measurement - Dilute, using piston-type pipettes or a diluting apparatus with polythene tips the standard series, the blanks and the sample extracts 1 + 19 (v/v) with ultra pure water in polycarbonate test tubes and mix. Measure in the standard series, the blanks and the sample extracts the SI concentration with the ICP-OES at a wavelength of 251.61 nm. 

The refining area has five steps 1) ammonia removal, 2) NaCl concentration and removal, 3) hydrazine-water distillation to reach azeotropic concentration, 4) extractive distillation with aniline to break the azeotrope and 5) distillation to separate hydrazine from aniline. Sometimes 50% caustic replaces aniline in the extractive distillation. If ultra pure hydrazine is needed, freeze crystallization is used to remove the supernatant fluid. Assays between 99.5% and 99.99% have been achieved. 

All solvents and chemicals were HPLC grade. Organic solvents, sodium carbonate (anhydrous), and sodium bicarbonate were purchased from Fisher Scientific (Fair Lawn, NJ, USA). Carbonate buffer, pH = 10.0, was prepared using the sodium carbonate (anhydrous), and sodium bicarbonate. A solution of 0.1 % triethylamine in methanol was made for the elution solvent. Diethylcarbamazine citrate was obtained from Sigma, and used to make stock solutions (St. Louis, MO, USA). The internal standard, 1-diethylcarbamyl-4-ethylpiperazine (E-DEC) was synthesized by the Division of Medicinal and Natural Products Chemistry at the University of Iowa, College of Pharmacy. Ultra-pure analytical grade Type I water was produced by a Milli-Q Plus water system (Millipore Corporation, Bedford, MA, USA). For the extraction of DEC and of its internal standard, Alltech Extract - Clean C18 cartridges, 500 mg with a 2.8 mL reservoir, and a SPE vacuum manifold (Alltech, Deerfield, IL, USA) were used. 

To minimize contamination, all glassware was cleaned with soap and water, rinsed with distilled water, heated in an oven at 550 C for 8 h to combust any traces of surficial organic matter, and finally rinsed twice each with ultra-pure methanol and methylene chloride. The KOH used for saponification was extracted three times with n-hexane and once with methylene chloride in a separatory funnel to remove organic interference. 

A crude lactide stream produced in the lactide synthesis reactors contains lactic acid, lactic acid oligomers, water, meso-lactide, and further impurities. Two main separation methods, distillation and crystallization, are currently employed for lactide purification. Crystallization may be carried out either by solvent crystallization or melt crystallization. The most used method for production of ultra-pure lactide in laboratory is by repeated recrystallization of a saturated lactide solution in mixtures of toluene and ethyl acetate [15, 23, 24]. Lactide purification using C4-12 ethers [25], and an organic solvent that is immiscible with water to extract the solution with water [26] are also reported. Melt crystallization is more practical in industry for lactide purification. Several types of equipment are described in the literature for melt crystallization [17, 27-30]. This method uses the differences in the melting points of L-, D-, and meso-lactide for separating the different lactides from each other. In a distillation process, the crude lactide is first distilled to remove the acids and water, and then meso-lactide is separated from lactide [11, 31]. Different methods are reported in the literature for distillation purification of lactide [32, 33]. In... 

AU equilibrium extractions were carried out at room temperature with 1 1 ionic liquid to aqueous phase ratio. The ionic hquid in its pure state absorbs a small amount of water depending on the initial nitric acid concentration that can vary from 17000 to 25000 ppm for 0.01 to 3 M nitric acid concentration, respectively. In the experiments a solution of 30 % (v/v) TBP in ionic liquids was prepared and equilibrated with the nitric acid solution at the required concentration by mechanical shaking at various time lengths. Saturation was confirmed by measuring the viscosity for both pure and saturated ionic liquid with a digital Rheometer DV-III Ultra (Brookfield). It was found that the ionic liquid was saturated after about 45 min shaking. Then, the two phases were separated and the pre-equihbrated... 

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