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ANALYTICAL CHEMISTRY, VOL. 50, NO. 14, DECEMBER 1978
Table IV. 3 1 P FT/NMR Analysis of Fenitrothion Formulationsarb, c sam-
ples
F
1
15.56 ( 1 4 . 7 ) d
0.15
2 3 4
9.85 ( 9 . 8 ) 1 1 , 7 5 (11.70)
0.16 0.12 0.18 0.10
5
16.25 (10.25) 12.60 (11.6)
BF
SMF SMBF 0.10 0.09
0.01
FO 0.12
0.05 0.07 0.05
F, fenitrothion; BF, bis(fenitrothi0n); SMF, S methylfenitrothion; SMBF S-methylbis(fenitr0Conditions; 33% emulsion in thion); FO, fenitrooxon. acetone-d6, 10 mg/mL CAA, 1 0 m g TPP standard, 10K 90" pulses, and 0.5-s repetition time. Composition wt %. GLC results in parentheses.
that the levels of S M F and ODMSMPT are much lower than in samples 1-5$which had been stored for a t least two years. This difference suggests that these two compounds result mainly from rearrangement on storage. Although HPLC did not detect T M P T , DMPTC, and ODMSMPT, it did detect cresol which also appears to increase on storage. In general, the amounts determined by NMR were higher than by HPLC for BF, and lower for SMF, SMBF, and FO. Fenitrothion formulations prepared from emulsifiable concentrates were also analyzed by 31PF T / N M R . Because of the dilution factor involved, iOK transients were necessary. The results are given in Table IV. All the samples analyzed contained both B F and SMF as contaminants. Sample 2 with the lowest amount of fenitrothion also contained some FO. The levels of fenitrothion were also determined by GLC, and varied from 0.5-3670 lower than by 31PFT/XNIR. No explanation could be found for the large discrepancy in sample 4?for which direct NMR analysis of formulation gave a value of 16.3'7%. Of the contaminants detected in technical grade fenitrothion, only SMF and FO are potent inhibitors of cholinesterase ( I O ) . However, FO and, in particular, SMF are also susceptible
to enzymatic hydrolysis by mammalian plasma and hepatic aryl esterases (11). Based on these facts and the amounts present in the technical material and formulations, it is thought that they do not represent any special hazard to personnel handling these materials. In summary, 31PF T / N M R is a rapid facile procedure for the analysis of phosphorus-containing contaminants present in organophosphorus pesticide technical material and formulation. In technical grade fenitrothion, the main contaminants found were BF, SMF, and ODMSMPT with traces of T M P T , SMBF, and FO. BF. SMPF, T M P T , FO, and some S M F and ODMSMPT appear to be byproducts of t h e manufacturing process. In stored samples the amounts of S M F and ODMSMPT were significantly greater than in recently prepared materials, suggesting that they were also formed on long term storage. This technique should find wide application both for rapid assay and detailed analysis of pesticide formulations in the future.
ACKNOWLEDGMENT .The authors thank M. A. LVilson for her technical assistance.
LITERATURE CITED Y. Takimoto, A. Murano, and J. Mjamoto, ResidueRev., 60, 11-28 (1976). W. D. Marshall, R. Greenhalgh, and V. Batora, Pestic. Sci., 5, 781-789 (1974). C.T. Burt, T. Glonek, and M. Barany, Soence, 195, 145-149 (1977). S. A. Sojka and R. A. Wolfe, Anai. Chem., 50, 585-587 (1978). I . K. O'Neil and M. A. Pringler, Anal. Chem., 49, 588-590 (1977). T W. Gurley and W. M. Ritchie, Anai. Chem., 48, 1137-1141 (1976). R. Greenhalgh and W. D. Marshall, J . Agric. FoodChem., 24, 708-712 (1976). P Yeagie, W. C. Hutton, and R. E.Martin, J Am. Chem. Soc.. 97, 7175-7 181 (1975). T. W. Guriey and W. M. Ritchie, Anai. Chem., 47, 1444-1448 (1975). J. Miyamoto. N. Mikami, K. Mihara. Y . Takimoto, H. Kohda, and H. Suzuki, J , Pestic. Sci., 3, 35-42 (1978). G. L. Myatt, D. J. Ecobichon. and R . Greenhalgh, Environ. Res., IO, 407-414 (1975).
RECEIVED for review June 22, 1978. Accepted September 8, 1978.
Microcomputer-Controlled Monochromator Accessory Module for Dual Wavelength Spectrochemical Procedures J. D. Befreese,' K. M. Walczak, and H. V. Malmstadt" s^chcol of Chemical Sciences, University of Il/inois at Urbana-Champaign, Urbana, Illinois 6 780 7
A relatively inexpensive microcomputer-controlled monochromator accessory module has been developed which provides split beam, dual wavelength capability as well as ratiometric compensation for source fluctuation at a single wavelength. The two wavelengths can be keyboard selected and are focused at exit slits widely separated in space. This wide spatial separation of the slits facilitates the attachment of the accessory module without any modification to the basic programmable monochromator. The microcomputer controls the selection of both wavelengths and also performs other control and computation functions for the spectrometer system. The versatility of the dual wavelength system is demonstrated by its application to a wide variety of analytical techniques.
*Present address, Department of Chemistry, University of Kansas, Lawrence, Kan. 66045. 0003-2700/78/0350-2042$01.00/0
LVhere commercial instruments have been either too expensive or not suited for the particular situation, various methods have been used in the laboratory to implement dual wavelength measurements. These methods have included modulation of a monochromator sine bar ( I ) , introduction of quartz refractor plates (2-4) and oscillating mirrors (5) into the optical path, vibration of the exit slit ( 6 ) ,etc. However, these instrumental modifications have generally been designed with one analysis problem in mind. Therefore, they do not represent versatile solutions to the wide range of analysis problems for which a dual wavelength approach would be advantageous. It is believed that the monochromator accessory module (MAM) described in this paper does represent such a significant solution because it is microcomputer controlled for maximum versatility and reproducibility, it has a wide wavelength programming range which is particularly useful for molecular spectrochemical methods, it offers the C 1978 American Chemical Society
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ANALYTICAL CHEMISTRY, VOL. 50, NO. 14, DECEMBER 1978
INSTRUMENT
INTER FACE ou
INCREMENTAL ENCODER
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MONOCHROMATOR STEPPER MOTOR LIMIT SWITCHES
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1 T ENTER
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MAM DC MOTOR
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ENTER NUMBER O F STANDARDS AND SAMPLES 1
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MICROCOMPUTER
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DC MOTOR DRIVER
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