The determination of lysergide (LSD) in urine by high-performance liquid chromatography-isotope dilution mass spectrometry (IDMS)

The use of isotope dilution mass spectrometry (IDMS) has been investigated for the forensic confirmation of lysergic acid diethylamide (LSD) in urine by LC-MS. The advantages of using a deuterated analog of LSD as an internal standard over methysergide are discussed. This study includes a comparison of the electrospray mass spectra of LSD, LSD-d3 and methysergide, and discusses the choice of suitable ions for use in selected ion monitoring (SIM) mode. An IDMS method is presented for the LC-MS confirmation of LSD in urine, with a limit of quantification (LOQ) of 0.5 ng/mL, reflecting the forensic requirement at this laboratory. Under some circumstances the LOQ can be improved to 0.1 ng/mL. This method is linear in the range tested (up to 10 ng/mL LSD in urine) and has been validated in terms of accuracy and precision.     

"PUBLICITY" AS A PROBLEM IN THE INTERNAL VALIDITY OF TIME SERIES QUASI-EXPERIMENTS

Scholars who work with time series quasi-experiments have identified "publicity" as a problem in the interpretation of such research designs. The present study utilizes three examples of the role of publicity in three social interventions: the Romanian abortion restriction of 1966; the British breathalyzer crackdown; and, the 1978 Georgia Status Offender Act. The authors conclude that publicity is most likely to be a problem in internal validity when (1) the intervention is not truly abrupt and (2) a broad "policy" is evaluated as opposed to a "program."     

A novel method for STR-based DNA profiling using microarrays

We describe a novel method for rapidly identifying and distinguishing between different DNA sequences using short tandem repeat (STR) analysis and DNA microarrays. The method can be used to deduce identity, length, and number of STRs of the target molecule. We refer to this technique as the "variable-length probe array" method for STR profiling (VLPA). The method involves hybridization of the unknown STR target sequence to a DNA microarray displaying complementary probes that vary in length to cover the range of possible STRs. A post-hybridization enzymatic digestion of the DNA hybrids is then used to selectively remove labeled single-stranded regions of DNA from the microarray surface. The number of repeats in the unknown target is then deduced based on the pattern of target DNA that remains hybridized to the array. This DNA profiling technique is useful for performing forensic analysis to uniquely identify individual humans or other species.