A fully validated isotope dilution HPLC-MS/MS method for the simultaneous determination of succinylcholine and succinylmonocholine in serum and urine samples

An Accessible Yarn-Based Sensor for In-Field Detection of Succinylcholine Poisoning

Succinylcholine (SUX) is a clinical anesthetic that induces temporary paralysis and is degraded by endogenous enzymes within the body. In high doses and without respiratory support, it results in rapid and untraceable death by asphyxiation. A potentiometric thread-based method was developed for the in-field and rapid detection of SUX for forensic use. We fabricated the first solid-contact SUX ion-selective electrodes from cotton yarn, a carbon black ink, and a polymeric ion-selective membrane. The electrodes could selectively measure SUX in a linear range of 1 mM to 4.3 μM in urine, with a Nernstian slope of 27.6 mV/decade. Our compact and portable yarn-based SUX sensors achieved 94.1% recovery at low concentrations, demonstrating feasibility in real-world applications. While other challenges remain, the development of a thread-based ion-selective electrode for SUX detection shows that it is possible to detect this poison in urine and paves the way for other low-cost, rapid forensic diagnostic devices.

Simultaneous determination of succinylcholine and its metabolite in animal-derived foods by solid-phase extraction combined with ultra-performance liquid chromatography/mass spectrometry

RATIONALE

Succinylcholine has been increasingly used in the theft of animals. Because of the presence of residual levels of succinylcholine in poisoned animals, it is harmful for people to eat foods derived from these animals. Therefore, a method should be immediately established to determine succinylcholine and its metabolite in animal-derived foods.

METHODS

A fast, highly sensitive method, combining solid-phase extraction (SPE) with ultra-performance liquid chromatography/electrospray ionization tandem mass spectrometry (UPLC/ESI-MS/MS), was developed for the determination of succinylcholine and its metabolite in animal-derived foods. The sample was initially extracted with heptafluorobutyric acid and then further cleaned up using an SPE cartridge. Succinylcholine and its metabolite were separated using acetonitrile: 0.1% formic acid in 5 mmol L^-1 ammonium acetate as the mobile phase. Quantitative results were based on positive ion ESI multiple reaction monitoring mode.

RESULTS

The results show good linearity over a wide range with correlation coefficients of determination of more than 0.998. Both the limits of detection of succinylcholine and succinylmonocholine are 0.2 μg kg^-1 . The intra- and inter-day accuracies of the method are in the range 91.4%-104.6%, and the intra- and inter-day precisions are in the range 2.5%-6.6%.

CONCLUSIONS

This method can be used for the determination of succinylcholine as an illicit drug in animal-derived foods. It was successfully applied to the identification and quantification of succinylcholine and succinylmonocholine in animal-derived foods collected from a local farmers market in Jilin Province of China.

Survival following intentional succinylcholine injection for self-harm

Succinylcholine is a short-acting depolarizing neuromuscular blocking agent. We describe a case where the above drug was employed for self-harm by a health-care worker. The patient, a 28-year-old female, was brought to the emergency department (ED) in impending respiratory arrest and altered mental status. On arrival, she had hypoxia, bradycardia, and hypotension. Although the cause for rapid deterioration in this patient was unknown, the ED physician still went ahead by resuscitating the patient's airway, breathing, and circulation. During the course of resuscitation, information was received that an empty ampoule of succinylcholine was recovered from her bathroom. Further clinical examination and laboratory investigations led the treating physicians to suspect deliberate intravenous injection of succinylcholine. She was mechanically ventilated and monitored in the critical care unit. Targeted temperature management was initiated in the ED and was continued for 24 h. The patient was discharged from the hospital without any neurological deficits after 4 days. Patients with acute poisoning are one of the major encounters in ED, and this case highlights the possibility of anesthetic drug misuse in any health-care workers coming to the ED with sudden cardiac arrest, altered sensorium, or abnormal vitals. This is the first report describing the survival of a patient following intentional succinylcholine injection for self-harm.

Spectroscopic determination of succinylcholine in dosage forms using eosin Y

Two simple and sensitive analytical assay methods using spectrophotometry and spectrofluorimetry techniques were developed for the estimation of succinylcholine chloride (SUC) in pharmaceutical preparations. The suggested methods are based on the formation of an ion pair complex formed between the drug and eosin Y spectrophotometrically (Method I), or the suppressive effect of succinylcholine on the native fluorescence property of eosin Y (Method II). The spectrophotometric method (Method I) involves measuring the absorbance of the complex between succinylcholine and eosin Y at 550 nm in Britton Robinson buffer of pH 3. However, the spectrofluorimetric method (Method II) involves measuring the quenching effect of the studied drug on the native fluorescence property of eosin Y at the same pH at 550 nm after excitation at 480 nm. The absorbance versus concentration of the drug is rectilinear over the range of 0.5 to 15 μg/ml. The formation constant was 3.5 × 10⁴ and the Gibb's free energy change was -2.5 × 10⁴  J/mol. In Method II, the relative fluorescence intensity was directly proportional to SUC concentration over the range of 0.05 to 1 μg/ml. The proposed methods allowed a successful application to the estimation of succinylcholine ampoules. An explanation of the reaction pathway was postulated.

Nurse induced respiratory depression by succinylcholine--the 'hero syndrome'

A nurse administered the neuromuscular blocking agent succinylcholine (SUX) to at least one patient and gave first aid in the therapy of unexpected respiratory depression. SUX is regarded as an undetectable and thus perfect poison due to its short half-life and degradation to the endogenous compounds choline and succinic acid. However, SUX and especially its metabolite succinylmonocholine (SMC) were found in plasma and urine a few hours after administration by means of high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Compared to clinical studies, the window of detection was sufficient to gain definite proof; in other cases no samples were collected. The nurse enjoyed high reputation with the doctors. According to the court she wanted to present herself spectacularly as the first and decisive rescuer to demonstrate her special abilities and capacities, perhaps to receive a better job in the hospital. Considering the actual case, the hero syndrome is not limited to fire-fighters.

A novel solid-phase extraction for the concentration of sweeteners in water and analysis by ion-pair liquid chromatography-triple quadrupole mass spectrometry

A highly sensitive method for the simultaneous trace (ng/L) quantification of seven commonly used artificial sweeteners in a variety of water samples using solid-phase extraction and ion-pair high-performance liquid chromatography (HPLC) triple quadrupole mass spectrometer with an electrospray ionization source (ESI-MS) in negative ion multiple reaction monitoring mode was developed. Ten solid phase extraction (SPE) cartridges were tested to evaluate their applicability for the pre-concentration of the analytes, and their loading and eluting parameters were optimized. Satisfactory recoveries (77-99%) of all of the studied sweeteners were obtained using a Poly-Sery PWAX cartridge with 25 mM sodium acetate solution (pH 4) as wash buffer and methanol containing 1mM tris (hydroxymethyl) amino methane (TRIS) as eluent. The method is sound and does not require pH adjustment or buffering of water samples. The HPLC separation was performed on an Athena C18-WP column with water and acetonitrile, both containing 5mM ammonium acetate and 1mM TRIS as mobile phases, in gradient elution mode. The linearity, precision, and accuracy of the method were evaluated, and good reproducibility was obtained. Method quantification limits varied between 0.4 and 7.5 ng/L for different water samples. The post-extraction spike method was applied to assess matrix effects, and quantification was achieved using internal standard calibration to overcome the unavoidable matrix effects during ESI-MS analysis. The method was applied to the analysis of thirteen water samples from Tianjin, China, including wastewater, tap water, surface water, and groundwater. The method described here is time-saving, accurate and precise, and is suitable for monitoring artificial sweeteners in different water matrices.

Degradation and elimination of succinylcholine and succinylmonocholine and definition of their respective detection windows in blood and urine for forensic purposes

The muscle relaxant succinylcholine (SUX) evokes respiratory paralysis, and numerous cases of fatal SUX intoxication have been reported. Detection of SUX and its metabolite succinylmonocholine (SMC) is difficult, both due to their (bis-) quaternary structure and the extreme hydrolytic susceptibility of SUX, and data on degradation kinetics of SUX and SMC is scarce. The present study investigates the in vivo and in vitro degradation as well as elimination of both target analytes using authentic blood and urine samples from anesthetized patients. With a special focus on the urinary data and stabilization issues, this work intends to considerably enhance the forensic knowledge concerning SUX intoxications and to present the reader with practical analytical strategies to cope with such difficult cases. Eighteen subjects undergoing surgery and requiring arterial as well as bladder catheters were included in this study. Muscle relaxation was initialized with a bolus injection of 80-100 mg SUX. Blood and urine samples were either collected using paraoxonized (n = 15) or non-modified (n = 3) tubes. Sampling was performed within 6 h after SUX application following a pre-assigned schedule. Samples were processed according to a validated isotope dilution HPLC-MS/MS method using ion-pair solid-phase extraction. In blood, SUX was usually detectable for up to 10 min post-injection, while detection of SMC was possible over the whole observation period of 6 h. Effectiveness of organophosphate stabilization was proven for both analytes and is therefore recommended. In freshly secreted urine, detection windows of a minimum of 2 h as opposed to 6 h have been determined for SUX versus SMC, respectively. Considering SMC plasma kinetics, detection of the metabolite in blood and freshly secreted urine appears to be possible over a period of at least 8-24 h. Paraoxon did not enhance the stability of either target substance in urine, stabilization of urine samples is nonetheless recommended. In summary, SMC was proven to be the most promising target analyte in SUX analysis, with urine being the proposed matrix of choice for forensic applications. Furthermore, our work defines meaningful detection windows for SUX and SMC in blood and urine as routine matrices and presents sampling recommendations as well as guideline values for forensic toxicological analysis.

Applicability of succinylmonocholine as a marker for succinylcholine administration--comparative analysis of samples from a fatal succinylcholine-intoxication versus postmortem control specimens

Doubts concerning the applicability of succinylmonocholine (SMC) as a succinylcholine (SUX) marker have been issued. A comparative analysis of previously discussed tissues, i.e. brain, liver and kidney, was conducted to further elucidate this question by searching for diagnostically useful differences in analyte content in samples of SUX- versus non-SUX-associated fatalities. Furthermore, possible advantages of vitreous humor as a novel and promising target matrix for SUX analytics were assessed. Sample material of SUX-negative controls as well as the fatal SUX-intoxication was derived from frozen archive material and current autopsies. Samples were analyzed according to a modified protocol of a previously published and validated method employing ion-pairing solid-phase extraction and subsequent HPLC-MS/MS analysis. Standard addition was employed for quantification as well as an estimation of the analytical limits of the method. In all tested matrices, the method was proven to be sufficiently sensitive for the intended application. No indication of native SMC was found in controls of fresh tissues, nor in fresh or frozen vitreous humor. However, most of the samples were found to be positive for a previously reported interference with SMC's main ion transition, thereby falsely suggesting an SMC content of up to 139 ng/g, 126 ng/g, 165 ng/g and 93 ng/ml in brain, liver, kidney and vitreous humor, respectively. Contrasting the results for fresh sample material, SMC was detectable in some of the initially non-putrefied liver samples after long-term storage, as well as in massively decomposed SUX-negative control bodies. In this context, a microbial origin of the analyte may be assumed. All tissues as well as the vitreous humor of the fatal SUX-intoxication were negative for SUX and SMC. Just like serum, tissue and vitreous humor samples therefore do not allow a reliable diagnosis of a SUX-intoxication: in tissues this is due to the pronounced instability of both target analytes in these esterase-containing matrices, for vitreous humor an additional reason could be their insufficient incorporation into this medium.

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

The determination and quantitation of drugs in biological matrices using high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) is becoming increasingly popular in analytical toxicology, while at the same time a growing awareness for the limits of this technique can be observed. Our group previously developed a rapid HPLC/ESI-MS/MS method for the detection and quantitation of succinylcholine (SUX) and succinylmonocholine (SMC) using ion-pairing extraction of samples with subsequent separation by gradient chromatography on a Synergi Hydro RP C18 column (4 microm, 150 x 2 mm). Identification of analytes was achieved in the multiple reaction monitoring (MRM) mode, using two characteristic ion transitions each, the respective analytes' retention time as well as co-elution of stable isotopic analogues. In both native serum as well as urine an interference with the main MRM transition of SMC was found to co-elute with this analyte, thus severely compromising the identification and quantitation of this target analyte. The interference was further shown to be eliminated from serum and urine by exposure to alkaline conditions and hence proven to share a key physicochemical property with SMC. The observed absence of the second and third most intense ion transitions of SMC in the unknown substance was the only useful distinction between both compounds.The detailed presentation of selectivity problems encountered during method development is intended to initiate further discussion on this yet underrepresented issue in HPLC/MS/MS. The present work emphasizes the need to monitor more than just one ion transition to confidently rule out signal interferences, ensure correct analyte identification as well as quantitation, and thus avoid false-positive results. In this context, the employment of minor MRM transitions for the quantitation and identification of a given analyte is presented as a satisfactory solution to HPLC/MS/MS selectivity problems, and proposed as a possible alternative to previously published approaches.