Improving Efficiency in the Forensics Laboratory: Introducing a New Controlled Substances Analyzer

Improving Efficiency in the Forensics Laboratory: Introducing a New Controlled Substances Analyzer Application Note Authors Abstract Sarah Keeling and Francis Diamond Forensic chemists are faced with the challenge of analyzing a multitude of sample NMS Labs types to identify controlled substances and pharmaceuticals. Law enforcement Willow Grove PA depends on a laboratory’s ability to identify not only the major components of the Bruce Quimby samples, but also relevant compounds present at lower levels. These samples can Agilent Technologies, Inc. range from an unidentified white powder or botanical material to tablets, syringes, Wilmington DE or charred pipe residues. Typically, these analyses are performed by full scan GC/MS with library search reports generated by database searching. Because the evidence obtained by law enforcement can encompass an ever widening variety of analytes including closely related compounds such as isomers and possible analogs, greater attention to detail is required in the analysis. The new novel psychoactive substances (NPS) and synthetic cannabinoids that have hit the streets contain many new isomers and analogs that are not readily differentiated by routine searching methods. This system uses the following enhancements to increase the efficiency of analy - sis. Hydrogen is used as carrier gas to reduce operating costs. Retention time lock - ing (RTL) is used to maintain precise retention time matching between multiple sys - tems and the database. Backflush provides a mechanism to remove nonvolatile compounds by flow switching and redirecting them out the split vent. Finally, decon - volution reporting software (DRS) is used to identify drugs, even when present in complex mixtures or at trace levels. Results from the new system are compared to a typical helium system currently used for criminalistics analysis. Introduction Experimental Crime labs routinely use GC/MS as the definitive technique to Hardware configuration identify or confirm the presence of a controlled substance or The system is an Agilent 5975 GC/MS with an Agilent 7890A drug. The current financial environment of crime labs requires GC and an Agilent 7693 Automatic Liquid Sampler. It is config - forensic chemists to analyze for an ever expanding list of ured to run on a 220 V power supply. It uses a thermal insu - emerging drugs with fewer resources. Along with this finan - lated oven insert. It is configured using purified hydrogen as cial strain, labs are faced with the increasing price of helium, the carrier gas supplied from a cylinder (UHP). It is addition - with projected cost increases and scarcity rendering helium ally configured to use backflush with an AUX EPC module and too costly to use. Another strain on the criminalistics system a purged union (PUU). There is a restrictor to allow for proper is the increased prevalence of complex sample types, such as application of pressure to control carrier gas flow into the synthetic cannabinoids and other botanical mixtures. A more mass spectrometer. The injection port is deactivated. The cap - efficient means of analysis is required to circumvent these illary column is a 10 m DB-5 with a 0.250 mm internal diame - issues. ter and 0.25 µm film thickness. A diagram of the hardware is Using hydrogen as a carrier gas is a viable alternative, as it is shown in Figure 1. less expensive than helium and can be easily generated on site. To aid in shortening run time, the instrument is config - ured for fast oven ramp (using a 220 V power source) and an insert to reduce the volume of the oven, allowing for faster Liquid Injector AUX EPC temperature programming. Equipping the system with back - Vent 2.81 psig flush allows for the removal of nonvolatile material from the S/S inlet, head of the column at the end of each run, preventing ghost Ultra Inert peaks in subsequent chromatograms and reducing the need coating 0.81 m × 0.12 mm id for column maintenance. The use of DRS coupled with the precise retention time control of RTL allows for more efficient Agilent Column 5975 MSD PUU data processing and provides the capability to distinguish (Turbo) between closely related compounds and to identify trace Agilent 7890A GC amounts of drug even in complex samples. 10 m × 0.25 mm, 0.25 µm DB-5MSUI 220 V Oven with high speed oven insert (pillow) Traditional library searching involves simple search routines based on a large amount of a relatively pure substance being Figure 1. Diagram of hydrogen carrier gas GC/MS system configuration. present in the chromatogram; however as samples become more complex in nature and contain multiple components, more labor intensive processes are required to perform the requisite identification. This involves more personnel time, Software configuration greater training, and allows for subjective data manipulation that may be done in an inconsistent fashion. DRS is an auto - MSD Productivity Chemstation software was used for data mated method of analyzing data for the presence of specific acquisition and data analysis. Additionally, DRS was used for compounds in a defined database. A report can be generated data processing. A database of compounds was generated using predetermined set points to allow for consistency in consisting of drugs and controlled substances typically seen data processing, reducing the possibility of human error and in case work. This database was compiled with data acquired bias. This results in a more efficient analysis and a timelier using hydrogen as a carrier gas. reporting of results. 2 Data analysis settings in -house database. The standards were acquired on the RTL Various set points were evaluated, including flow, tempera - method, so precise retention times were recorded in the data - ture, liner configuration, and injection mode. Using the results base. The mass spectra in the database were the extracted of the evaluation, a data acquisition method was optimized. spectra generated using the AMDIS program. The use of Once in place, this method was used for retention time AMDIS deconvolution results in clean spectra with interfer - locking (RTL) and all subsequent data analyses. ences from column bleed and overlapping impurities removed. Each entry was added to the database with the CAS# when RTL was employed to ensure that reproducible retention times available, the chemical formula, the precise retention time (in were achieved every day of operation, even after column clip - minutes), and the compound name and synonyms. The reten - ping or replacement. It also allowed precise matching of tion time in seconds was entered as the retention index entry retention times with other instruments that were similarly in the database, as required by DRS. The database contains configured and locked to the same compound. 461 compounds. A database of mass spectra was generated on the hydrogen Data acquisition parameters system by extracting a series of reference standards. The Table 1 lists the experimental conditions comparing the spectra were verified by comparison to NIST11 and an hydrogen and helium systems used. Table 1. Experimental Conditions Comparing the Hydrogen and Helium Systems Used Helium Hydrogen Inlet EPC split/splitless EPC split/splitless (deactivated) Mode Constant pressure Constant flow Injection type Splitless Pulsed splitless Injection volume 1.0 µL 1.0 µL Injection dispense speed 6,000 µL /min 6,000 µL /min Inlet temperature 265 °C 265 °C Pressure 19.973 psi 6.6078 psi Total flow 55.452 mL/min 54.952 mL/min Septum purge flow 3 mL/min 3 mL/min Purge flow to split vent 50 mL/min at 0.3 minutes 50 mL/min at 1 minute Injection pulse pressure 11 psi until 0.3 minutes Sample overlap Off 1.5 minutes before end of GC run Gas type Helium Hydrogen Oven Voltage (VAC) 240 V 220 V Initial oven temperature 50 °C 50 °C Initial oven hold 0 minutes 1 minute Ramp rate 30 °C/min 60 °C/min Final temperature 340 °C 325 °C Final hold 6.83 minutes 4 minutes Total run time 16.497 minutes 9.5833 minutes Equilibration time 0.1 minutes 0.5 minutes 3 Table 1. (continued) Column #1 (separation column) Type DB-1 DB-5 Length 12 m 10 m Diameter 0.200 mm 0.250 mm Film thickness 0.33 µm 0.25 µm Flow 2.4515 mL/min 1.9522 mL/min Pressure 19.973 psi 6.6078 psi Average velocity 90.224 cm/sec 54.454 cm/sec Backflushing flow –12.906 mL/min Column #2 (MS restrictor) Type Deactivated fused silica Length 0.81 m (0.17 in transfer line) Diameter 0.120 mm Film thickness 0 µm Pressure 2.8091 psi Flow 2 mL/min Average velocity 321.77 cm/sec Flow 1 minute post run 9.428 mL/min MSD Acquisition mode Scan Scan Solvent delay 1.50 minutes 2.30 minutes EMV mode Relative Gain Factor Relative voltage 0 Gain factor 1 Low mass 40.0 amu 40.0 amu High mass 550.0 amu 570.0 amu Threshold 250 50 Sample number 11 A/D samples 22 Vacuum pump Performance turbo Performance turbo Quad temperature 150 °C 200 °C Source temperature 230 °C 300 °C Transfer line temperature 300 °C 300 °C 4 Study protocol smaller window to be selected for individual compounds or Three hundred eighty-four case samples originally analyzed for all compounds in the database. Additionally, searches can on the helium system were reanalyzed on the hydrogen be performed in Simple mode, which does not penalize for system to generate comparison data. These vials were evapo - mismatched retention times. Overloads are readily identified rated at room temperature to dryness and reconstituted with in a TIC and addressed accordingly. This is commonly seen ethyl acetate to the same volume. The reason for this was when compounds are present in a sample at disproportionate that the samples were originally dissolved in methylene chlo - amounts or because street samples are of unknown ride, which, if injected on the hydrogen system, may produce concentrations, aliquot volumes may be miscalculated.

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