An analytical strategy for quaternary ammonium neuromuscular blocking agents in a forensic setting using LC-MS/MS on a tandem quadrupole/time-of-flight instrument

Abstract

An analytical strategy is described for analyzing quaternary ammonium neuromuscular blocking agents in a wide variety of biological specimens in a forensic setting. Neuromuscular blocking agents such as succinylcholine, pancuronium, and tubocurarine, often used as paralytic agents during surgery, are occasionally suspected as paralytic poisoning agents involved in suspected homicide and suicide cases. Because suspicion in such cases can develop slowly, the age, nature, and quality of available specimens varies greatly. The compounds are challenging analytically because of their simultaneous precharged yet lipophilic character. An analytical strategy has been devised for extracting these compounds from complex matrices using a combination of a modified Bligh and Dyer liquid-liquid extraction (used in reverse) followed by reverse-phase ion pairing solid-phase extraction using heptafluorobutyric acid as an ion pairing reagent. Final analysis is by LC-MS/MS using a tandem quadrupole orthogonal acceleration time of flight instrument (Q-TOF) with repetitive product ion scanning at high resolution. Native and spiked specimens are compared for both quantitative and especially qualitative purposes. The method has been applied to a wide variety of fluid and tissue specimen types, including numerous specimens from exhumation autopsies. For most specimens, detection limits are in the 2 to 10 ng/g range. Succinylmonocholine has been demonstrated to be present at low levels in normal posthumous kidney and liver. The Q-TOF is an excellent platform for forensic analytical investigations. This analytical strategy should also be applicable to other problematic analytes and sample matrices. (J Am Soc Mass

Succinylmonocholine analytics as an example for selectivity problems in high‐performance liquid chromatography/tandem mass spectrometry, and resulting implications for analytical toxicology

“…false-positive results, this special case additionally emphasizes the possible detrimental effects on scientific research: The fact that SMC was recently found in native post-mortem tissues, thus raising the question as to the existence of endogenous SMC, 15,16 could easily have mislead us to consider our preliminary results as supportive of this theory. This is especially true since the previously reported SMC tissue concentrations vary around 50 ng/ mL, 16 which closely resembles our mean serous interference concentration of 55.9 ng/mL SMC eq. Additionally, the discovery of similar physicochemical features of the interference compared to SMC, namely its likewise alkali-labile character, could have been mistaken as a further indication for the existence of native SMC.…”

“…Apart from the negative implications which an uncritical interpretation of such interference-prone data must have for toxicological case-work, i.e. false-positive results, this special case additionally emphasizes the possible detrimental effects on scientific research: The fact that SMC was recently found in native post-mortem tissues, thus raising the question as to the existence of endogenous SMC, 15,16 could easily have mislead us to consider our preliminary results as supportive of this theory. This is especially true since the previously reported SMC tissue concentrations vary around 50 ng/ mL, 16 which closely resembles our mean serous interference concentration of 55.9 ng/mL SMC eq.…”

Pharmacokinetic Properties of Succinylmonocholine in Surgical Patients

“…Comparably larger difficulties were met during the sensible modeling of the elimination processes: it is undisputed that for both SUX and SMC, peripheral elimination is possible or even probable [e.g., considering the observed instability of these substances in tissues (9,23)]. However, the extent of this elimination is totally unknown.…”

“…With SMC as a marker, the time frame for possible detection of an SUX application has ultimately been extended from a few minutes to [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] h, yet it is conceivable that forensic casework in alleged SUX intoxications remains critical. In contrast to the majority of substances subjected to a CYP-P450-based metabolism, degradation of SUX and SMC is independent of an intact cardiovascular system.…”

“…The fact that both SUX and SMC are analytically challenging compounds critically hampers forensic investigation. Additionally, the recent report on detection of the more stable SMC in SUX-negative postmortem control tissues began to question the metabolites' applicability as an SUX marker, which would severely shorten the detection window of this potential venom (8,9) and add to its image as a so-called "perfect poison".…”