Anal. Chem. 1983, 55, 1647-1648
the loop (and filtration device), and load the filtered sample into the loop. Analytical precision for DISFA appeared to be independent of sample loop size. Relative standard deviations of peak heights for replicate injections of samples containing between 10 and 100 ng of N03-N mL-l of nitrate were less than 1% each for various injection loops ranging from 0.1 to 1.0 mL in volume and ranged from less than 1%to 4% for the samples containing low levels of nutrients (5-40 ng of N03-N or P04-PmL-l) injected with a 0.2-mL loop (Figure 4). DISFA thus representri a compromise between FIA and SFA but provides desirable features of both techniques. Although DISFA requires larger sample volumes and has slower sample throughput than FIA, it provides greater analytical sensitivity and can be used for sample manipulations having relatively slow reaction times (e.&;.,cadmium reduction of nitrate to nitrite). Sample volumes for filtration and analysis are reduced from those generally required for SFA. DISFA is used routinely in our laboratory to measure nitrate and phosphate in natural and experimental water samples. In addition, we have interfaced the DISF'A system with a flow cell and a liquid chromatograph controlleir (Altex 420) to automatically monitor phosphate release by individual small aquatic invertebrates over successive 10-min intervals (16). The DISFA system can also serve as a compound- or element-specific detector for aqueous liquid chromatography if steps are included to liberate the analyte from the fractionated components during SFA analysis. For example, we have developed a phosphorus detection system by including ultraviolet oxidation (15 min) and acid hydrolysis (12 min) steps in the SFA flow scheme [after the manual procedure described by Gloosen and Kloosterboer (17)]. The flow injectioin valve provides a low-dead-volume interface compatible with liquid chromatographic plumbing
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and provides an accurate way to determine exact residence time for the DISFA detection system.
ACKNOWLEDGMENT We thank B. J. Eadie, P. F. Landrum, D. Scavia, and S. J. Tarapchak for reading the manuscript, D. James for illustrations, and J. M. Kelley for editorial assistance. Registry No. Nitrate, 14797-55-8;phosphate, 14265-44-2; water, 7732-18-5. LITERATURE CITED Snyder, L.; Levine, J.; Stoy, R.; Conetta, A. Anal. Chem. 1978, 48, 942A-956A. Benerldge, D. Anal. Chem. 1978, 5 0 , 832A-846A. Snyder, L. R. Anal. Chim. Acta 1980, 114, 3-18. Ruzicka, J.; Hansen, E. H. "Flow Inlection Analysis"; Wiley-Interscience: New York, 1981. Ranger, C. B. Anal. Chem. 1981, 53, 21A-32A. Margoshes, M. Anal. Chem. 1977, 49, 17-19. Ruzicka, J.; Hansen, E. H.; Mosbaek, H.; Krug, F. J. Anal. Chem. 1977, 49, 1858-1861. Monola, H. A. Anal. Chem. 1981, 53, 1312A-1316A. Margoshes, M. Anal. Chem. 1982, 5 4 , 678A-679A. Ruzicka, J.; Hansen, E. H. Anal. Chlm. Acta 1975, 78, 145-157. Armstrong, F. A. J.; Sterns, C. R. R.; Strickland, J. D. H. Deep-sea Res. 1967, 74, 381-389 (Technlcon Procedure No. 158-71W). Murphy, J.; Riley, J. P. Anal. Chlm. Acta 1982, 27, 31-36 (Technicon Procedure No. 155-7 1W). Gardner, W. S.; Vanderploeg, H. A. Anal. Chem. 1982, 5 4 , 2129-2 130. Ruzicka, J.; Hansen, E. H. Anal. Chim. Acta 1978, 9 9 , 37-78. Van Den Berg, J. H. M.; Deelder, R. S.;Egerink, H. G. M. Anal. Chim. Acta 1980, 114, 91-104. Scavia, D.; Gardner, W. S. Hydrabialagla 1982, 9 6 , 105-111. Gloosen, J. T. H.; Kloosterboer, J. G. Anal. Chem. 1978, 5 0 , 707-7 11.
RECEIVED for review February 16, 1983. Accepted May 12, 1983. This is contribution No. 348 of the NOAA Great Lakes Environmental Research Laboratory.
Assay of Gold in Anlon Exchange Reslns N. E. Gabriel' and H. H. Law" Bell Laboratories, Murray Hill, New Jersey 07974
Anion exchange resin columns are commonly used t o recover gold from waste solutions. Before sending the resins to the refinery for gold recovery, it is necessary to determine the gold content of the resins. Despite rapid advances in analytical instrumentatlion, this analysis remains complex. The current accepted pirocedure involves prolonged drying of the resins, ashing in a1 muffle furnace, and dissolving the gold in aqua regia, after which the gold is finally recovered and weighed as the metal. Interest has been expressed for the devellopment of another method to analyze anion exchange resins for gold. From an analytical point of view it would be desirable to have a method that is less time-consuming and simpler. These features would save laboratory time and money as well as improve the accuracy of the results. Recent work has shown that gold in the form of gold cyanide complex can be removed rapidly and completely from Amberlite (Trademark of Rohm and Haas Co., Philadelphia, PA) IRA-400 and IRA-900 anion exchange resins (1, 2). The recommended treatment of the resins involves treating a packed bed column of gold containing resin with 4.88 M 'Present address: Department of Chemistry, MIT, Cambridge,
MA 02139.
KSCN in 50 vol YO dimethylformamide (DMF) (3). The objective of this work is to develop the guidelines for an analytical procedure for determining the gold content of anion exchange resins by using the results of the aforementioned study.
EXPERIMENTAL PROCEDURE The apparatus used to hold a 1.00-g resin sample is illustrated in Figure 1. The column is packed in this manner: a small piece of glass wool is placed above the value, the dry resin sample is added and packed with a glass rod, and another piece of glass wool is placed on top before 35 mL of eluent, 4.88 M KSCN in 50 vol % DMF, is added to the funnel. The valve is opened and all the eluent is allowed to drip through the column into a 25-mL graduated cylinder, which is changed when full. The volumes of the two samples are noted. The samples are analyzed for gold with atomic absorption spectrometry, and the gold content is calculated. Wet packing of resins should be considered if air pockets form. With the present apparatus and the Amberlite resins, wet packing was found to be not necessary. Amberlite IRA-400 resins of known gold content were prepared by adding the appropriate amount of potassium gold cyanide solution to 10 g (wet) of resin samples. The solutions were stirred for 15 min and allowed to stand overnight. They were then filtered, and the resins were placed in a 50 O C vacuum oven for 24 to dry. The fiitrate was analyzed for gold by atomic absorption
0003-2700/83/0355-1647$01.50/00 1983 American Chemical Society
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ANALYTICAL CHEMISTRY, VOL. 55, NO. 9, AUGUST 1983
and the
