Armando Alcaraz

Nuclear forensics in law enforcement applications

Over the past several years, the Livermore Forensic Science Center has conducted analyses of nuclear-related samples in conjunction with domestic and international criminal investigations. Law enforcement officials have sought conventional and nuclear-forensic analyses of questioned specimens that have typically consisted of miscellaneous metal species or actinide salts. The investigated activities have included nuclear smuggling and the proliferation of alleged fissionable materials, nonradioactive hoaxes such as “Red Mercury,” and the interdiction of illegal laboratories engaged in methamphetamine synthesis.

Analysis of tetrodotoxin

Abstract Law enforcement personnel interdicted an illegal shipment of a chemical suspected to be an illicit drug. However, literature within the package indicated that the substance was actually tetrodotoxin, a potent marine neurotoxin. Analyses of the questioned samples by gas chromatography–mass spectrometry revealed no evidence for the presence of illicit drugs, but this technique was ineffectual for the identification of tetrodotoxin. Direct-inlet-probe mass spectrometry was likewise unable to characterize the chemical identity of the subject material. Electrospray-ionization mass spectrometry was implemented to successfully identify the interdicted substance as tetrodotoxin.

Quantitative Analysis of Tetramethylenedisulfotetramine (Tetramine) Spiked into Beverages by Liquid Chromatography−Tandem Mass Spectrometry with Validation by Gas Chromatography−Mass Spectrometry

Tetramethylenedisulfotetramine, commonly known as tetramine, is a highly neurotoxic rodenticide (human oral LD(50) = 0.1 mg/kg) used in hundreds of deliberate and accidental food poisoning events in China. This paper describes a method for the quantitation of tetramine spiked into beverages, including milk, juice, tea, cola, and water, with cleanup by C8 solid phase extraction and liquid-liquid extraction. Quantitation by high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) was based upon fragmentation of m/z 347 to m/z 268. The method was validated by gas chromatography-mass spectrometry (GC-MS) operated in selected ion monitoring mode for ions m/z 212, 240, and 360. The limit of quantitation was 0.10 μg/mL by LC-MS/MS versus 0.15 μg/mL for GC-MS. Fortifications of the beverages at 2.5 and 0.25 μg/mL were recovered ranging from 73 to 128% by liquid-liquid extraction for GC-MS analysis, from 13 to 96% by SPE, and from 10 to 101% by liquid-liquid extraction for LC-MS/MS analysis.

Pancuronium Bromide (Pavulon) Isolation and Identification in Aged Autopsy Tissues and Fluids

The isolation and detection of pancuronium bromide was developed for aged autopsy samples to identify and confirm this compound in questioned tissue samples. A novel protocol was optimized for the isolation of the target drug in highly decomposed tissues. Solid-phase extraction (SPE) cartridges containing styrene-divinylbenzene were investigated. This polymer retained quaternary drugs and facilitated sequential elution upon washing with commonly available solvents. The semi-purified SPE samples were prescreened by pyrolysis GC-MS. A candidate specimen was then confirmed by microbore high-performance liquid chromatography/electrospray-ionization/mass spectrometry (microHPLC-ESI-MS/MS) with a triple-quadrupole mass spectrometer. The developed procedures provided a qualitative or semiquantitative (at best) basis for the investigation of difficult cases involving overdoses of polar drugs.

The application of pancuronium bromide (Pavulon) forensic analyses to tissue samples from an "Angel of Death" investigation.

The case report of a serial killer who worked at several hospitals as a respiratory therapist is presented. The suspect was initially labeled a benevolent Angel of Death who ended the suffering of elderly patients through mercy killing. However, his subsequently declared motive for homicide was very different from other similar cases in medical settings. The application of new analysis techniques for the detection of pancuronium bromide in a series of aged exhumation tissues gave positive results and led to the resultant conviction of the therapist.

Forensic Analyses of Suspect Illicit Nuclear Material

A small metal sample, alleged to be a substance that could substitute for highly enriched uranium in a nuclear weapon, was subjected to qualitative and quantitative forensic analyses using methods of materials science, radioisotopic chemistry, inorganic chemistry, and organic chemistry. The specimen was determined to be moderately pure Sc, likely derived from a uranium refining operation. Although no fissionable species or weaponization signatures were detected, the sample did exhibit some unusual properties. These anomalies included lanthanide fractionation, with concentrations of Dy, Ho, and Er elevated by factors greater than 100 over normal levels, and the presence of long, odd-chain fatty acids.

On-site Analysis of Explosives in Various Matrices

Lawrence Livermore National Laboratory (LLNL) has developed several different strategies and technologies for the on-site detection of explosives. These on-site detection techniques include a colorimetric test, thin layer chromatography (TLC) kit and portable gas chromatography mass spectrometer (GC/MS). The screening of suspicious containers on-site and the search for trace explosive residue in a post-blast forensic investigation are of great importance. For these reasons, LLNLs Forensic Science Center has developed a variety of fieldable detection technologies to screen for a wide range of explosives in various matrices and scenarios. Ideally, what is needed is a fast, accurate, easy-to-use, pocket-size and inexpensive field screening test for explosives.

On-Site Sample Work-Up Procedures to Isolate Chemical Warfare Related Compounds using Solid Phase Extraction and Solid Phase Microextraction Technology

The rapid preparation and accurate analysis in the field of suspect samples is most important for on-site investigations relevant to the planned Chemical Weapons Convention (CWC) inspections. Sample preparation becomes the limiting factor and one of the most critical aspects of the challenge inspection. The primary aim of the analysis is to detect the presence of undeclared chemicals subject to control by the Convention.

Real-time, on-line determination of carbon monoxide using charge exchange with krypton in a triple quadrupole mass spectrometer

A triple quadrupole mass spectrometer (TQMS) is used as an on-line analyzer for pyrolysis products from oil shale, tar sands, and coal. Besides determining many hydrocarbon as well as 10 sulfur-containing species, it is important to determine the major oxygen-containing products: H/sub 2/O, CO/sub 2/, CO, and COS. CO is a particular challenge. It is impractical to remove the ubiquitous contribution of hydrocarbons to the ion at m/z 28 when using the normal MS mode and the product fragment at m/z in 16 MS/MS mode is unsatisfactory. With the replacement of Ar with Kr as the collision gas in the TQMS, a charge transfer reaction takes place with the CO/sup +/ ion but not hydrocarbon fragment ions of mass 28. By use of MS/MS mode with m/z 28 precursors, the major isotope of Kr at m/z 84 was monitored; this charge exchange product was linearly proportional to CO/sup +/.

Assessing the reliability of the NIST library during routine GC-MS analyses: Structure and spectral data corroboration for 5,5-diphenyl-1,3-dioxolan-4-one during a recent OPCW proficiency test.

Revision of the NIST library spectrum for the compound 5,5-diphenyl-1,3-dioxolan-4-one is presented. After the synthesis and characterization (by NMR and MS) of 5,5-diphenyl-1,3-dioxolan-4-one, it was found that its mass spectral data did not match the one found in the NIST database. Herein, we present a revised version of the spectrum corresponding to the material and a comparative analysis to the previously published data.