Harold T. McKone Saint Joseph College West Hartford. Connecticut 061 17
Detection of Butylated Hydroxyanisole (BHA) in Cooking Oils
The trend toward relevance in the undergraduate laborator\. has resulted in the oublication of numerous articles invoiving "real-world" materials (1-4). In this context, experiments employing thin layer chromatography are particularly useful: they demonstrate an important analytical technique, thev often require a minimum amount of time, chemicals, and equipment, and they can be used to advantage in analyzing for trace components in drugs and foods (5-7). For the three years chave been teaching a course in Environmental Science to nonscience majors. The latter portion of this c o m e is consumer oriented, emphasi~in~focds, drugs, and additives. The lahoratory experiment described here was develo~edwith three obiectivesin mind: (1)to exoose the nonsciencemajor to a faciie analytical methbd fo; detecting a trace amount of a substance: (2) to teach basic concepts of solubility and extraction; and (3) to develop student awareness of incidental and intentional food additives.
Butylated hydroxyanisofe, BHA (I), and butylated hydroxytoluene, BHT (II), are two fat preservatives found in a large number and variety of foods. Tens of thousands of pounds of these two antioxidants are used annually in foods as diverse as salad dressings, cereals, chewing gum,vegetable oils, pet foods, potato chips, rice, nutmeats, and candy. Both BHA and BHT are on the GRAS list; their amount in a food product is limited to 0.02% of the fat content of the food. In spite of the wide-spread use of both BHA and BHT, there is some question as to whether they are needed in all of the food products in which they are found. For example, several brands of vegetable oil which do not contain synthetic antioxidants are as economical as, and seem to have the same shelf life as, competing vegetable oils containing BHA and BHT. Furthermore, although both BHA and BHT are classified as "Generallv. Regarded as Safe" bv the Food and Drug .. Administration, they can rause severe reactions in allergic orrsons. Surprisinglv, the soecificantioxidant olaced in a food is not alwayB listedm theiahel but is someti&es designated as a "freshness preservative" or an "oxmen interceptor." Also, ingredients in foods such as mayonnaise and salad dressings do not have t o be listed on the label and both HHAand RH'I' are allowed in these foods (8). Cooking oils were chosen for the test samples for several reasons: (1)the technique involved in separating the synthetic antioxidants from cooking oils is relatively simple; (2) a wide varietv of cookine oils is readilv available: (3) several of these on the la"bels, some'stke "no preservaoils list '~BHAIBHT~ tives added," some contain preservatives different from BHA/BHT, while still others are vague as to whether a synthetic antioxidant has been added. Because of this last reason, there is real student interest in "finding the answer" and in comparing results. The procedure outlined below is specific I Precoated Silica Gel tlc plates may be obtained from Brinkmann Instruments, Ine., Westbury, New York 11590.
800 / Journal of Chemical Education
for BHA. BHT can be detected in a similar manner but the procedure is more difficult and time consuming. Experimental Separation of BHA from Cooking Oil A mixture of 25 ml of the cooking ail and 25 ml of n-hexane are extracted with 3 X 15-mlportions of 7296 ethanol. The combined alfunnel concohol extracts are then laced in a 5Ci-ml seoaratonr ~. .~~~~ taioing 300 ml of water. ?his mixture is now extracted with 3 X 25-ml portions of n-hexane. The comhined n-herane ertracm are dried (NR~SO,)and evaporated over a steam bath to approximately 1 ml.
Detection of BHA by Thh Layer Chromatography A Silica Gel plate' is spotted with a drop of the above extract and is developed with chloroform. After development, the slide is dried, sprayed with phasphomolybdicacid (20%solution in ethanol),dried, and exposed to ammonia vapors. The last step can be accomplished by placing the slide in a jar, the inside cover of which has an ammonia-soaked ball of cotton taped to it. If BHA is present, a blue spot will appear at an R, of 0.60. Visualization of BHA can also be accomplished by exposing the developed slide to uv light. Discusdon Students with minimal laboratory experience, working in pairs, are able to complete this experiment in one 2-hr lahoratory period provided two conditions are met: (1) that there aresufficient steam bath set-ups in order to avoid waiting in long lines to evaporate the n-hexane; (2) that the students have had some previous experience with thin layer chromatography. Some students may have problems understanding the theory involved in the extraction portion of the experiment; however, this was not found to he a serious drawback to the generally high student interest in the experiment. Standard samnles of BHA can be obtained from mmt maior chemical suppl; houses. A thin layer chromatogram o i a standard BHA sample yielded two components: a major one a t R, 0.60 due to BHA structure (I);a minor one a t Rl0.90 due to a trace amount of a structural isomer of BHA. Several students attempted to use this procedure for determining BHA in other oil-containing products. The results indicated that this procedure is satisfactory for mayonnaise and some salad dressings but is not satisfactory for cereals, cake mixes, and solid shortening. This experiment has generated student interest in cons u m e r i m h a s increased student awareness of f w d additives in ~eneral,and haa demonstrated that trace amounts of a substance can he detected in a short period of time with minimum equipment. Acknowledgment The author wishes to thank Mr. A1 Wickrosky of the Connecticut Experimental Station, New Haven, Conn., for providing information on BHA/BHT analysis. Thanks are also extended to the students of Chemistrv 130 for their helo in perfecting this experiment. Finally, the author wishes toacknowledge the work of Ms. Gloria Nelson who helped develo~ and coordinate this lab, as well as several other consumeroriented experiments. Literature Cited
(5) Chaaa.,D. W., and T0th.G. B.. J. CHEM. EDUC.,S1.487 (1974). 16) Chsnar, D. W., and Tath, G.B.,J. CHEM. EDUC., 51.22 (1974).
0 1 Pav1ik.J. W , J. CHEM. EDUC.50.134 (1973. 18) Nelaan. G., M.A. Thwis. Saint Jweph College, 1973
Volume 53,Number 12, December 1976 / 801
