Analysis of testosterone esters by tandem mass spectrometry.

The electron ionization (EI) and chemical ionization (CI) mass spectra of 12 representative testosterone esters were examined to explore the various analytical options available for identification and confirmation of the esters. Using EI, a number of fragment ions indicated the identification of the testosterone moiety, but structural confirmation of the individual esters often required the observance of the molecular ion at very low relative abundance ratios. The acceptable analytical method involved CI/tandem mass spectrometry based on the production of the 2 generic product ions derived from the protonated molecule ion.

Confirmation of trace level residues in the food supply.

With the recent proliferation of mass spectrometric methods available for the identification and confirmation of various compounds in different environmental matrices, it is timely to address the criteria desirable in a regulatory sample case. The emphasis of this review is on the experimental process of confirmation at concentration levels in the range of low parts per million (ppm) to parts per trillion (ppt). At such levels, various data manipulations or alternate choices of approaching the analytical problem of confirmation must be employed to ensure an acceptable result. The problems experienced when dealing with nanogram levels in analysis are much more complex than when recording a mass spectrum of an ample supply of a reference standard. This review reflects an interpretation of the developing status of confirmation since there does not yet exist "accepted criteria".

Potential misidentification of trichlorophenylethanol in imported peppers.

During regulatory analyses for the determination of pesticide residues on agricultural commodities, a frequently encountered trichlorinated compound was misidentified by the NBS library search routine. This case history illustrates the need for more rigorous confirmation criteria when dealing with multi-chlorinated compounds where fragmentation can be dominated by methyl loss followed by loss of CO and HCI.

Screening by tandem mass spectrometry for trace levels of alkylbenzenes.

Product ion spectra derived from molecule ions as the precursor ions for 14 alkylbenzenes have been studied under electron ionization and methane chemical ionization. The data have provided a satisfactory screening method for both detection and confirmation of such compounds at low parts per million levels.

Residue characterization of triadimefon in grapes by gas chromatography and mass spectrometry/mass spectrometry.

A field study of the use of the new fungicide triadimefon (Bayleton) on grapes has indicated that residue levels of 0.01 ppm may be expected on the ripe fruit in spite of the 60-75 day interval from spray to harvest. Triadimefon and its primary metabolite triadimenol (Baytan) have been characterized by gas chromatography and mass spectrometry to provide identification down to a detection level of 0.001 ppm. Recovery studies on these fungicides have indicated that they are completely extracted by the single multi-residue analytical methodology presently in use for monitoring fresh produce.

Characterization of benzyl isothiocyanate and phenyl acetonitrile from papayas by mass spectrometry.

Two unidentified analytical responses in a papaya extract were structurally determined by mass spectrometry to be benzyl isothiocyanate and phenyl acetonitrile. Both these compounds have previously been shown to result from degradation of benzylglucosinolate that occurs naturally in the seeds of the fruit. Characterization by mass spectrometry has now provided a convenient mechanism to detect both these degradation compounds in extracts resulting from routine pesticide residue analysis.

Structural determination of testosterone esters in oil injectables by thermospray mass spectrometry.

In the absence of analytical reference standards, the combination of thermospray and collision-activated dissociation mass spectrometry has been utilized to separate and identify the presence of several esters of testosterone in imported oil injectables. Structural identifications were based on generic daughter ions considered diagnostic of the steroidal ring structure of these anabolic steroids as well as daughter ions representative of the ester alkyl or aryl side chains.

Pesticide confirmation by triple stage quadrupole mass spectrometry: etrimfos and dimethoate.

The production of a protonated molecular ion, MH+, for a pesticide under investigation is often preferred for primary identification purposes. However, the lack of fragment ions under such chemical ionization conditions can place the burden of proof on a single ion species for confirmation. Although a single ion representing the molecule at the correct retention time on a packed column or high-resolution capillary column might seem to have furnished sufficient evidence for unambiguous confirmation, in a number of cases additional specificity can improve the analytical result. With the introduction into commerce of triple stage quadrupole (TSQ) instruments, the possibility of improving the degree of specificity by chemical ionization has emerged for practical pesticide residue confirmation analysis. Use of collision-activated dissociation (CAD) experiments to form daughter ions from the protonated molecular ion of 2 representative organophosphorus pesticides has provided a second dimensional plane of characterization for confirmatory purposes at incurred residue levels.

Thermospray collisionally induced dissociation with single and multiple mass analyzers.

A thermospray discharge ionization source has been used to obtain a collisionally induced dissociation (CID) spectrum of nabilone (MW 372) using a single stage quadrupole mass spectrometer. The resulting CID-mass spectrometry (MS) data show only a few structural features. Since most of the important fragments are above mass 200, it is difficult to assign structural identities to the primary daughter fragments or the nabilone molecule. Further information was obtained by using the thermospray discharge ionization source with a triple stage quadrupole mass spectrometer. Selected primary daughter ions were subjected to a second stage of CID fragmentation. Many of the resulting granddaughter ions are now in the mass range of 50-150 daltons and confident structure assignments can be made. The CID-MS-CID-MS data on nabilone showed the following features: a C9 aliphatic chain with a branch giving a C6 chain; losses of masses 58, 86, and 100 suggesting a ketonic structure that can break with up to 6 aliphatic carbons; losses of masses 60, 61, and 102 suggesting an ether or alcoholic oxygen; presence of one aromatic ring with one or two phenolic oxygens; low mass fragments of masses 55, 69, and 83 indicative of rings or unsaturation. It is audacious to suggest that the information given here is sufficient to write the full structure of nabilone. Nevertheless, the granddaughter fragment information permits a reasonable reconstruction of possible structures that could not be made with the first-order collisional fragmentation.

Identification of prescription drugs in adulterated Chinese herbal medications.

Analytical difficulties involved in the detection of a wide range of suspected polar and nonpolar drugs in botanical matrices have been solved by adopting a multipronged approach. Preliminary screening of Chinese herbal medications can be accomplished by a combination of thin-layer chromatography and gas chromatography/mass spectrometry and/or the employment of liquid chromatography/mass spectrometry as a probe introduction technique.

Levels of plasticizer in the frequent plasma donor.

Di-2-ethylhexyl phthalate (DEHP), a commonly employed plasticizer reported to be carcinogenic in rats and mice, has been confirmed to leach from all plastic component parts of the equipment employed in plasma donation. Resident aqueous solutions of both sodium chloride and sodium citrate were found to contain only trace levels of DEHP (0.03 ppm), while stored plasma samples contained levels at least one order of magnitude higher (0.4 ppm). Since at least 5% of all plasma donations in the Los Angeles area are deemed to be of the high frequency classification, investigation into repeated red blood cell exposure to DEHP was considered imperative. However, there was no difference in the levels of DEHP found in the plasma of the frequent plasma donor (50-60 times per annum) relative to the first-time donor. It is concluded that there is no increased contamination threat to frequent plasma donation from migrating plasticizer via red blood cell exposure, at least during the collection process. Furthermore, there is no more risk to recipients of plasma products from frequent donors than from occasional donors. It would seem that the ambient level of DEHP to be expected in stored frozen plasma products averages no greater than about 0.5 ppm.

Chemical ionization mass spectrometry of dichlofluanid and its major metabolite.

Gas chromatographic/mass spectrometric techniques using chemical ionization have been employed to characterize the fungicide dichlofluanid and its major metabolite. The results have indicated some unusual fragmentation pathways for perhalogenmethylmercapto compounds. Use of deuterated ammonia as reagent gas has permitted a comparative assessment of protonation and exchangeable hydrogens within the major fragment ion structures. Resultant structural information has been employed to confirm residue findings in strawberries at the low part-per-million level.