A Sensual Separation Science Experiment Solvent Extraction and Chromatographic Separation of Menthol Utilizing Various Consumer Products Kenneth G. Furton and Maria I. ~ e r e z ' Florida International University, University Park, Miami, FL 33199 particle size ranges of these detergents were evaluated to We have recently reported a detailed evaluation of the determine the optimum mesh range to use in the columns. use of commercially available detergents as general purA 100-g sample of each was dried overnight a t 120 "C to pose column packings for gas chromatography ( I ) . Comremove water andmost of the perfume from each detergent. mercially available laundry detergents make inexpensive, The detergents were sieved for approximately 20 min using reproducible packings that provide an interesting way to 13-cm Fisher Mesh series sieves (Springfield, NJ) in six teach the concepts of gas chromatography (GC).The majordifferent mesh ranges. Alist of all of the detergents studied ity of commercially available detergents contain anionic surfactants. which act as the active GC stationary ihase, although some deterDetergent Types and Sieve Analysis gents contain nonionic surfactants. For the present study, we evaluated the Detergent Type' Weight Percent of Total After Sieving 20 Minutes utility of all the commercially available laundry detergents we found in the Mesh Size Miami area (20) to test the general applicability of this type of experiment. In the experiment we have developed, the sample (analyte), the sample prepara- Ajax tion procedure, and the chromato- All graphic packing all use inexpensive Arm & Hammer consumer products. The analysis involves the extraction of menthol from Arrow blue afiershave using charcoal lighter fluid, Arrow white followed by chromatographic separa- Bold tion using a column packed with laundry detergent. Additionally, the analy- Cheer sis of menthol allows students to c~o'rox "detect" the analyte by smell in addi- Dash tion to the usual recorder presentation of the output of a thermal conductivity Drefi detector. We have found that the incor- Dutch poration of consumer products and a Fab sensual demonstration stimulates student interest and discussion of this Gain powerful technique. Ivory Lilac Column Preparation Sears All of the different available detergents from several Miami area stores surf (20 total) were studied in an attempt to determine the general applicability of Tide commercial laundry detergents as GC Trend packings. It is important to note that Wintree N 18.7 39.7 23.4 7.7 3.4 7.1 even detergents with the same name *A = contains anionic surfactants;N =containsnonianic surfactants;U =unspecified surfactanttype. brand may vary in composition depending on the area in which they are purchased. One of the main differences is and the results of the sieve analysis are summarized in the the weight percentage of phosphorus, which in the authors' table, along with the types of surfactants specified by the area (Miami, Florida) must be less than 0.5%; whereas, in manufacturer. other locations, the weight percentage can be as high as -10%. These differing compositions could, in principle, The largest fraction was generally found in the 20140 result in different physical and chromatographicproperties mesh range, although in some cases the 40160 mesh fracdepending on where the detergent was purchased. The tion was greater. The smaller particle size fraction, 40160, was chosen since it yielded more efficient (narrower peak 'NSFYoung Scho ar ACS Project SEED S~mmerSt~dent. Present widths) packed columns than the larger, 20140, particle aodress: Mam Senior rlign School. 2450 SW 1st Street. M am , FL fraction. Sieved packings (40160 mesh) were packed into 33135. nickel columns with the aid of vacuum suction and vibra-
946
Journal of Chemical Education
tion with a Burgess Vibro-Graver (Melrose, MA). The columns were constructed from 118-in. 0.d. nickel tubing (0.083 in id). The tubing was cut into 3-m lengths, coiled into 7-in. diameter coils and fitted with Swaeelock (Solon. OH) tube fittings. Each column held from 5 8 g of 40160 mesh packing, dependingon the detergent. The cost forthis amount of detergent was generally less than 4 cents. All analyses were performed on a Hewlett-Packard 5890-Series I1gas chromatograph equipped with a thermal conductivity detector using helium as the camer gas. The maximum operating temperature for the detergents was generally up to about 180 OC, determined by the volatility of the surfactant, rather than thermal decomposition. Van Deemter Plots for these wlumns indicate an ootimum flow rate of about 15 mumin ( I ) . Solutes used to determine McRevnolds constants (2). as well as menthol, were injected into each column to determine whether all of the commercial deterpent types would provide acceptable chromatographic perf&ma
