Infrared Identification of Microgram Quantities of Heroin Hydrochloride SIR: I n a recent publication Lerner ( I ) described a new color test for the identification of heroin. That procedure was intended as a field test. For court use where positive identification is required, Lerner's procedure has been modified so that infrared spectra may be obtained. The modification makes possible the positive identification of heroin hydrochloride in samples containing as little as 6 to 10 fig. The following is a description of the apparatus and procedure used: EXPERIMENTAL
Apparatus. Perkin-Elmer Model 21, double beam recording spectrophotometer equipped with a n ordinate scale expander. T h e scale expander is used for extremely small samples (about 25 pg. or less). Ultra RIicro 1Iull holder, manufactured by the Connecticut Instrument Corp. The holder mounts directly into the Perkin-Elmer Model 21 and transmits about 30% of the energy. The slit
of the holder was filed vertically to increase the energy transmitted to 85%. Micro Mull Plate. The Micro Mull Plate \\-as prepared b y covering one surface with a paraffin wax. The \vas was removed from the hot spot of the plate bv scraping, and a drop of water was added to this area. The water was blotted and the procedure was repeated until a satisfactory groove was obtained-one which would contain a drop of chloroform. The remainder of the 11-ax was removed to make the plate ready for use. Plastic ?\licrofunnel. Fisher catalog #lo-371-25 (24-mm.). The upper third of the funnel is removed by means of a 1/2-incli punch held in a chuck of a lathe and turned against a mandrel in the tail stock. Procedure. Place 5 t o 10 nig. of t h e heroin seizure (containing 1% or more heroin) in t h e plastic microfunnel containing a pledget of cotton in the stem. Hold t h e plastic funnel over a sink and add 0.3 ml. of l , l , l trichloroethane into the funnel. Stir the mixture with a paper clip. Press dcwn on the top of the funnel n-ith the
thumb, forcing the liquid out of the stem into the sink. This step removes by solution impuritieq N hich n ould otherivise interfere n i t h the infrared spectrum. Heroin remains in the funnel. -kid 0.3 nil. of chloroform to the funnel, dissolving the heroin as heroin hydrochloride. Stir the mixture and press donn on the top of the funnel n i t h the thumb, forcing the liquid out of the stem into a 1-ml. beaker. Transfer the chloroform to the micro mull plate containing the groove with a dropper. Evaporate each drop a t room teniperature before adding the nest drop. Run the spectrum of the sample a t 5x expanqion. RESULTS
An infrared spectrum of as little as 6 pg. of heroin hydrochloride is readily
obtained. LITERATURE CITED
(1) Lerner, M., ANAL. CHEW 32, 198
(1960).
ALBERTL. MILLS U. S. Customs Laboratory Baltimore, Rld.
Evaluation of Reaction Rates from Transmittance-Time SIR: Evaluation of reaction rates by spectrophotometry involves conversion of phototube output, equivalent t o transmittance ( T ) , to the physically significant quantity, absorbance. This requires taking the logarithm of the reciprocal of the transmittance. Either an additional stage of instrumentation or tedious replotting of data is required. Rates can be determined directly from zero-time intercept and initial slope of automatically recorded transmittance us. time traces. The kinetics of the reaction commonly used for analysis of Cr was studied by this method ( I ) . A Beckman DU with an Energy Recording Attachment and a Varian 11 recording potentiometer n-ere employed. Use of the relationships derived below greatly simplified computations. Consider a reaction involving i specie; with stoichiometric coefficients S,,absorptivities a, (unit cell length), and concentrations C,:
Ti =
exp ( - aiCi)
From the chemical equation
z
K i t h information concerning the stoichiometry of the reaction and absorptivities, it is possible to evaluate the rate from the valuesof T and dT/ dt a t any time. At the start of a reaction
T=IITi z
If Beer's law holds 416
ANALYTICAL CHEMISTRY
nhere g is the constant S,jZa,S,, z, denotes the kinetic order with respect to the i t h species and k is the rate constant. (Competing reactions assumed absent.)
Traces
I n the system to uhich 17-e applied this method, it n a s possible to choose a wavelength at which none of the products and only one of the reactants absorbed significantly. A number of other reactions of analytical interest have 5imilar characteristics. I n this case, increase of T n it11 time compensates for decrease in dT,'dt so that the recorded trace is linear for about one half time. The quantities needed for computation of rate can be determined m-ith precision directly from the trace and the knonn initial conditions. The method is also applicable, although perhaps le3q convenient, in more complicated caqes, LITERATURE CITED
( 1 ) Baloga, M., Earley, J., J . Am. Chem. Soc., 83, 4906 (1961).
MICHAELBALOGA' JOSEPH EARLEY Department of Chemistry Georgetown University Washington, D. C. 1 Present address: Pigments Department, E. I. du Pont de Nemours and Co., Inc., Chestnut Run, Del.
This n-ork was carried out under Yational Science Foundation Grant 12883.
