Fast Discrimination of Marijuana using Automated High-throughput Cannabis Sample Preparation and Analysis by Gas Chromatography-Mass Spectrometry.

In the United States, federal law and many state laws differentiate between marijuana and industrial hemp through delta-9-tetrahydrocannabinol (THC) levels, whereby the latter is defined as ≤0.3 percent THC on a dry weight basis. Many traditional cannabis identification methods employed by crime laboratories cannot accurately determine total THC quantities in accordance with federal and state regulations, or do so with increased time, labor, and risks of instrument damage. In order to quickly distinguish positive marijuana samples, a method was developed to identify plant material with a total THC level >1%. This novel, automated dispersive pipette extraction (DPX) method uses tip-based technology and an automated liquid handler to enable fast, hands-free selective isolation of THC and its precursors for downstream gas chromatography-mass spectrometry (GC-MS) analysis. The workflow proceeds with no repetitive manual effort and reduced need for instrument maintenance while enabling crime labs to legally identify marijuana through the detection of total THC above 1%. Recovery of THC using the DPX extraction method was 93% at 30 µg/mL and 78% at 500 µg/mL. Similarly, THCA-A recovery was 100% at 30 µg/mL and 74% at 500 µg/mL. Samples evaluated in a blind study (proficiency, hemp, and nonprobative case samples) were all accurately identified as greater than or less than 1% THC, with samples containing <1% THC being identified as "cannabis" and subjected to more discriminative analysis as needed.

Scanning laser polarimetry reveals status of RNFL integrity in eyes with optic nerve head swelling by OCT.

PURPOSE: Optical coherence tomography (OCT) shows retinal nerve fiber layer (RNFL) thickening in optic nerve head (ONH) swelling, but does not provide information on acute axonal disruption. It was hypothesized that scanning laser polarimetry (SLP) compared with OCT might reveal the status of axon integrity and visual prognosis in acute RNFL swelling. METHODS: Threshold perimetry, OCT, and SLP were used to prospectively study eyes with papilledema (24), optic neuritis (14), nonarteritic anterior ischemic optic neuropathy (NAION) (21), and ONH swelling (average RNFL value by OCT was above the 95th percentile of controls at presentation). Regional RNFL was judged reduced if the quadrant measurement was below the fifth percentile of controls. RESULTS: At presentation, average RNFL by OCT was similar for eyes with papilledema and NAION (P = 0.97), and reduced for optic neuritis. Average RNFL by SLP was slightly increased for papilledema and optic neuritis, and reduced for NAION (P = 0.02) eyes. The RNFL by SLP was reduced in at least one quadrant in 1 eye with papilledema, 1 eye with optic neuritis, and in 13 eyes with NAION. In NAION eyes, quadrants with reduced SLP had corresponding visual field loss that did not recover. By one month, eyes with NAION showed RNFL thinning by OCT (7/17 eyes) and by SLP (14/16 eyes) in contrast to optic neuritis (by OCT, 0/12, P = 0.006; and by SLP, 1/12, P = 0.0004). CONCLUSIONS: OCT and SLP revealed different aspects of RNFL changes associated with ONH swelling. OCT revealed thickening due to edema. SLP revealed a decrease in retardance in eyes with axonal injury associated with visual field loss, which is unlikely to recover.