Standards from distilled-deionized water

Materials. Aldicarb standards were obtained from the United States Environmental Protection Agency (USEPA), Quality Assurance Section and from Union Carbide Corporation. Crystalline samples of carbofuran and 3-hydroxycarbofuran were supplied by the Agricultural Chemical Group of FMC Corporation. Reference standards of methomyl (99% pure) and oxamyl (99% pure) were obtained from USEPA. HPLC grade methanol was purchased from Burdick and Jackson, Inc. Methylene chloride used for bulk extractions of the carbamate pesticides in solution was recovered, distilled and reused. Analytical reagent grade chemicals and solvents were used in all experiments. Doubly distilled deionized water was used for solution rate studies. Deionized distilled water (DDW) was used for dilutions in reactive ion exchange experim ts., , ... 

Figure 3. Standards recovered from 10 mL of distilled-deionized water on an ODS precolumn. Peak identities 4, 0.14 pg of caffeine 5, 0.20 pg of pentachlorophenol 7, 0.061 pg of m-nitroandine 8, 0.15 pg of atrazine 9, 0.40 pg of quinoline 10, 0.26 pg of 2,6-dichloroaniline 11, 0.14 pg of N-nitrosodiphenylamine and 12, 0.055 pg of pyrene. Conditions for concentration 10-mL sample enriched on an ODS-packed precolumn. Analytical separation was on Zorbax ODS, 250-mm by 4.6-mm i.d. column. Mobile-phase gradient was 100% pH 7,0.1 M acetate buffer for 2 min followed by ramp to 90% acetonitrile/10% pH 7, 0.1 M acetate buffer (v/v) in 20 min at 1.0-mL/min flow rate. Detection was at 254 nm. (Reproduced with permission from reference 18.)...

Figure 5. Standards recovered from 10 mL of distilled-deionized water on a strong-anion-exchanger packed precolumn. Peak identities 1, 0.87 pg of phenoxyacetic acid 2, 1.2 pg of p-chlorobenzoic acid 3, 0.33 pg of 2-naphthalenesulfonic acid and 12, 0.055 pg of pyrene. Conditions for concentration, analytical separation, mobile-phase gradient, and detection were the same as in Figure 3. (Reproduced with permission from...

Procedure Formaldehyde sample from the sampler was injected into the carrier stream where it was mixed with pararosaniline and then sulfite to form an alkylsulfonic acid chromophore which can be monitored spectrophotometrically at 570 nm For calibration, standard formaldehydes were sequentially introduced after a stable baseline was obtained At least five consecutively reproducible peaks were recorded for each concentration After each study or each day of operation, the FIA system was cleaned to remove any pararosaniline film, alkylsulfonic acid colored product, or particulate matters This reduced the scattered light in the absorption cell and the staining of the tubing walls. The clean-up procedure was initiated by running distilled deionized water through the system for five minutes followed by another five minutes washing with 0 1 N nitric acid and then flushing the unit for 30 minutes with deionized water The chromotropic acid method was used for comparative studies, and the analytical procedure for the chromotropic acid method was based on the procedure recommended by the American Public Health Association (12) ... 

All samples were dissolved in triple distilled, deionized water to a concentration of 1 mg/mL. Serial dilutions were made using a 10% run buffer in water. Individual peptide standards, the nine peptide standard mixture, and Dynotphin A fragment 1-13, were obtained from Sigma Chemical Co. (St. Louis, MO). A 0.1M phosphate buffer at pH 2.5 was used for all peptide separations. 

Water for injection (WFI) is the most widely used solvent for parenteral preparations. The USP requirements for WFI and purified water have been recently updated to replace the traditional wet and colorimetric analytical methods with the more modern and cost-effective methods of conductivity and total organic carbon. Water for injection must be prepared and stored in a manner to ensure purity and freedom from pyrogens. The most common means of obtaining WFI is by the distillation of deionized water. This is the only method of preparation permitted by the European Pharmacopoeia (EP). In contrast, the USP and the Japanese Pharmacopeias also permit reverse osmosis to be used. The USP has also recently broadened its definition of source water to include not only the U.S. Environmental Protection Agency National Primary Drinking Water Standards, but also comparable regulations of the European Union or Japan. 

Magnesium stock solution—using distilled or deionized water prepare six magnesium standards in 100 ml volumetric flasks of 0.1, 0.3, 0.4, 0.5, 0.6, and 0.8 pg mk concentration from the stock solution. Also prepare 250 ml of a 0.2 pg mpi magnesium standard. 

Water samples from various sources can also be analyzed (Parkinson et al., 1982) such as tap-water from patients on home dialysis. Water used to prepare dialysate solutions should be checked as a possible source for introducing aluminium into the dialysis system. Aluminium-free water for the preparation of standards, solutions and dilutions for analysis can be achieved by distilling, deionizing, passing through reverse osmosis, or a combination of the three. Analysis of this type of water should result in no detectable levels of aluminium (Smeyers-Verbeke et al., 1980). 

The electrodes are normally stored in distilled or deionized water and should be rinsed with deionized water before use. The electrodes can be dried by draining the excess water off onto a tissue. The electrode must be standardized by immersion in buffer solutions whose pH are well separated. The procedure is to immerse the electrodes in the buffer solution for a period of 1 min with continuous stirring and observe the value which is then adjusted to the buffer value by the pH or calibration control. The electrode is then rinsed and dried and immersed in the second buffer solution and allowed to equilibrate for 1 min with stirring and the second buffer value is read. If this differs from that which is expected then the slope control of the pH meter should be altered. This whole procedure is then repeated until the values obtained in the buffer solutions at each end of the pH range agree with those of the known buffer solution. 

Technical grade, distilled dichloromethane and deionized water were used. The bleach solution used was of technical grade (Stanchem, Poland). 2,2,6,6-Tetramethylpiperidinyl-l-oxyl (TEMPO) and NaBr were purchased from Acros. H NMR (300 MHz) and C NMR (75 MHz) were recorded on BmkerAvance 300 spectrometer in CDCI3 (with solvent residual signal as an internal standard). 

Stock Solutions and Standard Additions. One-liter, 10 M stock solutions were made by dissolving the appropriate amounts of copper, zinc, cadmium, and lead or their salts in nitric acid and diluting to volume. From these, two sets of standard solutions were prepared by dilution with deionized, quartz-distilled water a quadruple standard, used in the zinc analysis, containing 5.0 X 10 M copper, 2.5 X 10 M zinc, and 2.5 X 10" M cadmium and lead and a triple standard, 2.0 X lOr M in copper, 1.0 X 10 M in cadmium, and 2.0 X 10 M in lead, used in the analysis of these three metals. Additions of 100 /J. or multiples thereof were made to 100- or 200-ml seawater samples. 

Figure 4.31 Illustration of hypothesis that colloidal association interferes with the measurement of the antibacterial activity of ABDAC s in a MIC test ( ) CMC measured in deionized distilled water ( ) MIC values in CDM and the standard deviations (—) limiting solubility of the monomeric form of the quaternaries in CDM (i.e. critical micelle concentration in CDM) (- - - -) extrapolated line of the C8-C14 activity data of the ABDAC s. Shaded portion represents the amount of monomer required to be released from the micellar state before an effective equilibrium concentration is reached. From [212].

Standards of Sn species used for spiking were obtained from commercial sources. There was no cross-contamination of standards. All spiked levels were on a Sn basis. We prepared spiked solutions gravimetrically by weighing out known amounts of each Sn species, and then dissolving in a known, precise volume of deionized, distilled water. Spiked samples were prepared and analyzed within the same working day, together with external quantitative standards prepared and used on that same day. 

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