BULLARD and COLLINS: IMPROVED METHOD TO ANALYZE TRIMETHYLAMINE 



Table 7.— Trimethylamine content in mg TMA-N/100 g flesh 

 from 9-d-old walleye pollock using four methods of analysis. 



to 0.139 A for 6.75 ^g DMA-N/ml by a simple ratio, 

 i.e., 0.327A/(15.9 ixg DMA-N/ml):X/(6.75 /xg 

 DMA-N/ml). An equivalent TM A value was calcu- 

 lated to be 0.75 mg TMA-N/100 g flesh from Equa- 

 tions (3) and (5). If corrected for DMA, the TMA 

 value from Table 71X2003) would be 10.29 - 0.75 

 = 9.54 mg TMA-N/100 g flesh. Similar calcula- 

 tions for the 25 and 45'7f KOH methods gave cor- 

 rected values of 9.45 and 9.59 mg TMA-N/100 g 

 flesh. The small contribution of DMA at -15°C 

 (0.015 A ) would be 0.05 mg TMA-N/100 g flesh and 

 give a corrected value of 9.01 for the cold method. 

 The TMA values obtained by the three methods of 

 analysis were in good agreement if corrected for 

 DMA. The cold method of extraction gave slightly 

 lower and more accurate values than the other 

 methods. Cold extraction reduced the release and 

 extractability of numerous other interfering sub- 

 stances discussed by Dyer (1945). 



Extraction of Fish Flesh with 

 Added TMA and DMA 



To determine the recovery of TMA and the 

 interference of DMA, varying amounts of both 

 were added to blended flesh of Pacific cod, Gadus 

 macrocephalus , extracted with TCA in the usual 

 way and analyzed for TMA content by four meth- 

 ods. The sample of flesh contained 3.25 mg DMA- 

 N/100 g by Dowden's method (1938). The amount 

 of amine added, the resulting TMA value, and the 

 percentage of the theoretical value (recovery) by 

 each method of analysis are given in Table 8. The 

 TMA values of cod flesh with added TMA (3, 6, 9, 

 and 12 mg) resulted in similar recoveries of TMA 

 by all methods. If 5, 15, 30, and 50 mg DMA were 

 added to the blended flesh, however, the TMA 

 values were unacceptably high by the 50*7^ K2CO3, 

 25^/c KOH, and 45% KOH methods. The cold 

 method gave acceptable values although the addi- 

 tion of 50 mg DMA-N increased the TMA value 

 from 1.59 to 2.12, i.e., 133% of theory If the same 

 quantities of DMA were added plus a small 

 amount of TMA (3 mg), only the cold method gave 

 acceptable TMA values. The other methods were 

 strongly influenced by the presence of DMA. 

 However, if larger amounts of TMA were added 

 (12 mg), along with DMA, the influence of DMA 

 was reduced considerably and the 25% KOH and 

 cold methods gave acceptable results. 



All methods gave about equal recovery of added 

 TMA provided the DMA content was low. Tri- 

 methylamine values by the three published meth- 

 ods were strongly influenced by the relative 



Table 8. — Trimethylamine values In mg TMA-N/100 g flesh of Pacific cod as affected by different methods of 

 analysis when varying amounts of the TMA- HCl and DMA- HCl salts were added to the flesh before extracting 

 with TCA. 



Levels of TMA 

 and DMA added 



Sample, as is 



SmgTMA 



6 mg TMA 



9mgTMA 



12mgTMA 



5 mg DMA 



1 5 mg DMA 



30 mg DMA 



50 mg DMA 



3mgTMA 

 3 mg TMA + 

 3mgTMA 

 3 mgTMA + 



12mgTMA 

 12mgTMA 

 12mgTMA + 

 12mgTMA 



5 mg DMA 

 15mg DMA 

 30 mg DMA 

 50 mg DMA 



5 mg DMA 

 15mgDMA 

 30 mg DMA 

 50 mg DMA 



471 



