Identification of heroin and its diluents by chemical ionization mass spectroscopy

Abstract

Preprocessing technique Classification method Autoscale Weighted autoscale Optimum linear transformation I. Linear classifier a) Least-squares 83/83 83/83 83/83 b) Negative feedback 56/83 77/70 74/87 II. 3-Nearest Neighbor 80/60 89/80 92/97 III. Multiclass classifier a) Least-squares 91/87 91/87 91/87 b) Negative feedback 94/90 93/90 78/90method is invariant to all linear transformations, the results are the same for the three preprocessed sets of mass spectral data.The second classification method used in this study was the K-Nearest Neighbor Classification Rule (4) with K equal to three. This method is a multiclass method that does not depend upon linear separability. Hence, classification performance is improved in the last two sets of preprocessed data. The attributes and limitations of this method can be found in the chemical literature (4).The results of the multiclass classifier ( ) introduced in this paper are also found in Table I. Here again, the least squares procedure (a) and the error correction feedback procedure (b) were used to calculate the necessary weight vectors. The multiclass procedure performed very well. The overall performance indicates that the least squares procedure for calculating the weight vector is best. Again, note that least squares solutions are unique and are invariant to all linear transformations of the data. These attributes recommend the least squares multiclass procedure for applications which involve more than two classes. The method is at least as effective as other linear classifiers and comparable in accuracy to the more expensive K-Nearest Neighbor Rule.

Isobutane Made Practical as a Reagent Gas for Chemical Ionization Mass Spectrometry

“…Because isobutane reagent ions have a significantly higher proton affinity than methane reagent ions, analyte fragmentation upon proton transfer from a reagent ion is reduced or eliminated, and the abundance of the intact adduct ion is increased. Isobutane has been used for applications where it was critical to identify the analyte protonated molecule and for maximum sensitivity [10][11][12][13][14][15][16]. Isobutane is also more efficient at creating thermal electrons than methane [7] and has been used for increased EC-NCI analyte signal [17].…”

Determination of heroin by circular dichroism

“…Heroin would best be quantitated in HC1 solutions at 238 nm, [9] = +64. The [9] values for 6-MAM and morphine at the same wavelength are +270 and +311, respectively (12). In base, [9] for morphine at the band maximum at 253 nm is +458.…”

“…The [9] values for 6-MAM and morphine at the same wavelength are +270 and +311, respectively (12). In base, [9] for morphine at the band maximum at 253 nm is +458. The results from the four analytical procedures which involve CD, and the GC results are given in Table I as percent heroin free base by weight in the confiscates.…”

“…where [9] is the molar ellipticity coefficient and C is the molar concentration. This definition of [9] is a departure from that in the older literature, but in the context of CD being a modified absorption spectrum, we have preferred to define a quantity analogous to the e or molar absorption coefficient of UV spectrophotometry. Heroin would best be quantitated in HC1 solutions at 238 nm, [9] = +64.…”

“…In the case of heroin the standard accepted testing procedures include color spot-tests (1), microcrystalline tests (2), and a variety of instrumental methods (3) such as GC (4, 5), HPLC (6), IR and UV absorption spectrophotometry (1,7), and mass spectrometry (8,9) in its many forms such as CIMS, GEMS, MID, etc. Diluents, adulterants, and metabolites can mask the specificity of the tests for heroin, which is the motivation for their presence in the first place.…”