ANALYTICAL CHEMISTRY, VOL. 57, NO. 14, DECEMBER 1985
2997
Table I, N-Nitrosodimethylamine Recoveries by GC-TEA
NDMA concn, sample
n
size range, g
blood liver kidney brain
6
0.8-1.2
6
1.2-1.6 0.4-0.7 0.3-0.7
6 6
ppb 2.3 3.0 3.6 4.2
& 1.3
f 0.3 f 0.9 f 1.5
I
3
recovery range, 70 94 95 93 97
f f f f
2
1 I 0
2
1
a sharp interface without emulsion formation. These dimensions were established by experiment and are not simply a reduction of the original device. Samples. Male strain A/J mice from the Jackson Laboratory, Bar Harbor, ME, or A/JCr mice from the Animal Production Area of the Fredrick Cancer Research Facility were sacrificed and samples of blood, liver, kidney, and brain were placed in small plastic cryotubes, frozen in liquid nitrogen, and shipped in dry ice to the laboratories of the Chemistry Department of Temple University for NA analysis. Sample Preparation Technique. Each sample was weighed and placed in 100-mL round-bottom flask with 1 g of sulfamic acid, 0.5 mL of concentrated H2S04,1g of Antifoam B emulsion, 100 p L of morpholine, and 25 mL of water. N-Nitrosodi-npropylamine (NDPA) was added as an internal standard. The flask was attached to the higher arm of the apparatus. Another 100-mL round-bottom flask containing 50 mL of methylene chloride was attached to the lower distillation arm. Boiling chips were added to each flask, and each was heated via a heating mantle to the boiling point of the respective solvent for 15-16 h. After cooling for 30 min, the contents of the flask with methylene chloride were poured through a pad of anhydrous sodium sulfate into a Kuderna-Danish evaporator. The pad was washed three times with 10-15 mL of methylene chloride. The methylene chloride was concentrated to 2.0-2.5 mL, and 25-30 pL of the concentrate was analyzed for NAs via GC-TEA. R E S U L T S AND DISCUSSION The apparatus involves simultaneous distillation and extraction. The samples, blood or tissue, are digested during the boiling process. The volatile NAs are distilled along with water and methylene chloride into the condenser. The mixed condensate flows into the capillary tubing to the bottom of the apparatus where the methylene chloride, now containing the NAs, returns to the methylene chloride flask and the water, to the sample flask. After the apparatus was run for 15-16 h, the NAs originally in the sample flask have been transferred to the methylene chloride flask. Small samples of blood and tissues were prepared, and sample results with recoveries are given in Table I. Recoveries for N-nitrosodimethylamine (NDMA) added at the start of the procedure by direct spiking and/or injection into organs averaged 93.5%. These recoveries show an improvement over those from previously published methods (3, 6) for similar samples, along with decreased contamination from added water. No N-nitrosomorpholine was found in the extracts. It has been documented that NAs can form in deionizing cartridges (7). The original apparatus requires 250 mL of
I
I
I
4
8
12
i 16
Minutes Flgure 2. Chromatograms of reagent blanks: curve I, unmodified apparatus showing peaks for NDMA (1) and unidentified compound (2) (see text) from water contamination; curve 11, modified apparatus showing absence of contaminatlon. Peak 3 is the internal standard, NDPA.
water in the sample side. Water containing 0.01 ppb NDMA contributes 2.5 ng of NDMA when 250 mL are used. When a 1-g sample is then analyzed, a significant error from NDMA contamination is introduced that is on the order of 2.5 ppb, based upon sample size. However, the modified extractor requires the addition of only 25 mL of water, one-tenth of the water needed in the commercially available apparatus. Figure 2 shows duplicate blank samples, one processed via the commercially available extractor and the other by the modified extractor. Contamination from the water has been eliminated with the reduced volume apparatus. Curve I shows a peak (1)from NDMA in the water plus a peak (2) due to an unidentified non-N-nitroso compound. The latter was established by the photolysis procedure of Doerr and Fiddler (8). The extractor unit provides the investigator with a better choice over the mineral oil distillation. The latter involves seven separate operations whereas this procedure consists of only three. Minimal handling is, of course, critical in trace analysis. Where sample size is not critical, the larger apparatus can be used with the same minimal sample handling, and the results are superior when compared to other techniques. Registry No. N-Nitrosodimethylamine, 62-75-9. LITERATURE C I T E D (1) Magee, P. N.; Barnes, J. M. Br. J. Cancer 1956, 7 0 , 114-122 (2) Fine, D. H. In “Nitrosoamlnes and Human Cancer”; Magee, P. N., Ed.; Cold Spring Harbor Lab: New York, 1982; Banbury Report Series, No. 12, pp 199-210. (3) Hotchkiss, J. H. J. Assoc. Off. Anal. Chem. 1981, 6 4 , 1037-1054. (4) Fine, D. H. I n “Nitrosamines and Human Cancer”; Magee, P. N., Ed.; Cold Spring Harbor Lab: New York, 1982; Banbury Report Series, No. 12, pp 185-174. (5) Fine, D. H.; Rufeh, F.; Lieb, D.;Rounbehler, D. P. Anal. Chem. 1975, 47, 1188-1191. (6)Havery, D. C.; Fazio, T.; Howard, J. W. J . Assoc. Off. Anal. Chem. 1978, 67, 1374-1378. (7) Kimoto, W. I.; Dooley, J.; Carre, J.; Fiddler, W. Wafer Res. 1980, 74, 869-876. (8) Doerr, R. C.; Fiddler, W. J. Chromatogr. 1977, 740, 284-287.
RECEIVED for review May 24,1985. Accepted August 12,1985. This investigation was supported, in part, by Grant No. CA18618, awarded by the National Cancer Institute, DHEW.
CORRECTION Photoelectroanalytical Chemistry: Electrochemical Detection of a Photochemically Active Species, Tris(2,2’-bipyridine)rut henium( 11)
J. M. Elbicki, D. M. Morgan, and S. G. Weber (Anal. Chem. 1985, 57, 1746-1751).
In Table I, under the heading Q, the last two labels have been reversed. The correct order going from top to bottom [Co(NH3)&1I2+,Co(cysS03)t-, and should be [CO(C,O~)~]~-, Co(gly),. The numbers are correct in their positions as published.
