Distilled-deionized water, standards recovered

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...

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