Targeted analysis of tert-butyldimethylsilyl neurotoxin hydrolyzate derivatives by selective one-dimensional or two-dimensional gas chromatography-mass spectrometry (2023)

Chromatography Journal A

bend 1501,

June 9, 2017

, str 99-106

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Targeted analytical method for sensitive and differential determination of hydrolyzates of neurotoxins, alkylmethylphosphonic acids, as theiruncle-Butyldimethylsilyl (TBDMS) derivatives are prepared using optional 1D and 2D (1D/2D) GC-MS and applied to the analysis of samples with significant interference matrices. After the samples were dried, alkylmethylphosphonic acid and methylphosphonic acid (MPA) were added by addingN-methyl-Yes-(uncle-Butyldimethylsilyl)trifluoroacetamide is heated and subjected to1D/2DGC-MS. The instrument consists of an initial low thermal mass column DB-5 and a second column DB-17 and a quadrupole electron ionization mass spectrometer, which enables the GC-MS system. use1D/2D GC-MS, analytes that do not co-elute with matrix components can also be separated1D Single GC mode. It is necessary to transfer and separate only those chromatographic fractions that are negatively affected by the co-elution of matrix components2DGC. Quantification can be achieved by a combination of separation and mass spectrometric detection. The TBDMS derivatives ethyl, isopropyl, isobutyl, pinacol and cyclohexyl MPA (cHMPA) and MPA itself were well separated and determined within 3 min1D GC-MS mode, detection limit ~10 ng/mL reaction mixture (except for cHMPA derivatives whose mass spectra contain noisy background peaks). to exist2D-GC–MS mode, elution window date every 0.04 minutes1D GC is cardiac (H/C) and is transferred to the second column after washing the first column. A cHMPA-TBDMS derivative peak was isolated and gave a clear mass spectrum within 6 min. Recycle all derivatives2D GC-ovi1D GC estimated to be over 66% with a detection limit of approximately 10 ng/mL reaction mixture. The target compound was not detected as a separate peak in the presence of urine extract1D GC-MS mode (except isobutyl-MPA) and quantification based on extracted ion monitoring are not possible. However,2D GC-MS of the H/C fraction of the target derivatives showed a single peak with a well-defined mass spectrum, and the recovery of the derivatives was over 70%, except for cHMPA (31% at 1.25 μg/mL). Phosphonic acid can be detected below 60 ng/ml. Sulfuric acid and phosphoric acid also adversely affect the determination of the alkylmethylphosphonic acid derivative TBDMS1D The peaks of the GC-MS and MPA-TBDMS derivatives are completely obscured by the large peak of the sulfuric acid derivative. However in1D/2Basic separation of MPA derivatives and sulfuric acid derivatives was achieved under D-GC-MS conditions, and a very sensitive MPA detection of 20 ng/mL was achieved.


Nerve agents are a class of chemical warfare agents [1], [2] that are extremely toxic to humans due to their organophosphate anticholinesterase activity. Their use, production and storage are prohibited [3], so they are considered compounds of choice in the prevention of chemical warfare/terrorism. In the Matsumoto subway attacks in Tokyo in 1994 and 1995, the doomsday cult organization Aum Shinrikyo used sarin gas on vulnerable groups, causing many deaths and injuries [4]. In the Syrian war, many people died from sarin bombs[5]. In incident management, pathogenic toxic substances must be identified by complex laboratory techniques, and methods of instrumental analysis and sample preprocessing have been developed to determine chemical warfare agents and related compounds [6], [7], [8], [9]. Neurotoxins are unstable and are easily converted into alkylmethylphosphonic acid (AMPA) by hydrolysis between the phosphorus atom and the leaving group [10]. AMPA is finally converted into methylphosphonic acid (MPA) by hydrolysis of the alkoxy functional group (Figure 1). Such hydrolyzed compounds can be analyzed using recently developed liquid chromatography-mass spectrometry (LC-MS) techniques [11], however, due to their hydrophilic nature, the sample matrix may interfere with them. As a purification method, we previously developed a strong cation exchange and strong anion exchange (SAX) solid phase extraction (SPE) method [12], [13], [14]. The advantage of this SPE method is the complete recovery of not only AMPA, but also MPA from complex matrix samples [15], [16]. It has been reported that zirconium SPE can be used to purify AMPA [17], but it is not sufficient to recover MPA. The determination of MPA is important because it is a key component that can be formed from synthetic byproducts and precursors of nerve agents. As a validated method for neurotoxin exposure [18], serum butyrylcholinesterase (BuChE) neurotoxin adducts were analyzed [19] and a highly sensitive method including detection of protease digestion by LC-tandem-MS of adducted peptides was developed [20]. ], [21], [22] and fluoride gas chromatography (GC)–MS [23], [24]. We have also developed a method involving chymotrypsin digestion (LC-MS) combined with procainamide affinity purification and preparative polyacrylamide gel electrophoresis [25].

During the forensic investigation of the Aum Shinrikyo sarin attack, we detected isopropylmethylphosphonic acid (IMPA) and MPA in field samples, and subsequently detected IMPA in blood samples from the wounded by GC-MS of methylphosphonic acid (IMPA) and MPAuncle-Butyldimethylsilyl (TBDMS) derivatization [4]. The technical advantages of TBDMS derivatization are simple production, stable derivatives, characteristic mass spectra [26], [27] and successful application in the analysis of other chemical warfare agents [28], [29]. However, even with SAX-SPE pretreatment, it is difficult to detect low levels (sub-µg/mL) of MPA from complex matrix samples by TBDMS-derivatized GC-MS [11]. This may be due to strong interferences of the matrix components present in the samples.

Considering the toxicokinetics of nerve agents (Supplementary Data), AMPA can be detected in the blood immediately after exposure to nerve agents when ingested levels exceed 160 nmol, and also after exposure between 160 and 1000 nmol AMPA urinary excretion has been detected in the urine. In fatal cases, high levels of AMPA (possibly more than 2 nmol/ml blood) may be detected, and in toxic cases, moderate levels of AMPA (possibly <1 nmol/ml blood or urine) may be detected. In the absence of intoxication and simple exposure, low concentrations of AMPA can be detected (probably > 100 pmol/ml). Physiologically, AMPA cannot be metabolized to MPA in vivo, so MPA cannot be detected after neurotoxin exposure. However, if a crudely manufactured nerve agent (which may contain not only the nerve agent but also synthetic intermediates and by-products) is distributed on site and reaches humans, the presence of MPA in the source gas may be detected, as was the case with with sarin in Matsumoto [4] Gas attack. In the environment, neurotoxins are degraded by various reactions, and AMPA and MPA can be detected in environmental samples.

In the GC-MS method performed with TBDMS, the limits of detection (LOD) for AMPA and MPA were 60 ng/ml and 700 ng/ml of urine samples, respectively, due to severe matrix interferences [14]. However, significantly lower LOD (values ​​of 100 pmol/ml or values ​​of 10 ng/ml) are required for toxicological studies. Multidimensional gas chromatography (MDGC) is a powerful technique for excellent separation of volatile and semi-volatile compounds from complex samples [30], [31]. MDGC includes an overall profile analysis, the so-called comprehensive two-dimensional GC (GC×GC) [32] , [33] , and a more specific target analysis, the so-called Heart-cutting (H/C) MDGC [34] , [35] . For H/C MDGC, the narrow eluting fraction in the first GC (1D GC) transferred to another GC (2data center). Choice of 1D or 2D (1D/2D) GC-MS is a newer method in modern H/C-MDGC [36], [37], [38], [39]. with Choice1D or2D GC-MS can be performed without additional changes to instrument settings and the same mass spectrometer can be used for both1i2D analysis. This enables the use of spectral data from one-dimensional chromatograms of total "surveillance" ions. to exist1D/2D GC–MS is a Deans switching mechanism between low thermal mass (LTM) columns [40], which enables rapid high resolution separations using relatively simple hardware.

we have already reported on a1D/2D The GC-MS method has been successfully applied to taste and odor samples [41], [42], [43]. For targeted analysis, analytes that do not co-elute with matrix components or other analytes can be1Column D. Only those chromatographic fractions adversely affected by matrix components or coelution of other analytes must be transferred to the separator2Column D. Quantification is possible by GC and MS detection. This method is also successfully applied in the analysis of allergens [43]. Degradation products of organophosphorus pesticides such as neurotoxins have been analyzed by comprehensive two-dimensional gas chromatography with flame photometric detection [44]. However, neurotoxin hydrolysis products are not suitable for direct GC analysis, and derivatization reactions are inevitable for GC analysis.

We previously examined the performance of TBDMS derivatized GC-MS for four target compounds, namely ethylmethylphosphonic acid (EMPA), IMPA, pinacylmethylphosphonic acid (PMPA) and MPA [12], [13], [14]. [15], [16], [27]. In this article, we expanded the number of targets from four to six and evaluated the detection capability1D/2D GC–MS with AMPA and MPA in urine sample.

As far as we know, this is the first usage check1D/2D GC-MS analysis of silyl derivatives of hydrophilic compounds. Furthermore, we showed that sulfuric and phosphoric acids strongly interfere with the detection of AMPA and MPA as derivatives of TBDMS in GC-MS, and we evaluated1D/2D GC-MS for real acid-rich matrix environmental samples. Therefore, target compounds that are usually difficult to detect can be quantified1D/2D GC-MS sample of complex matrix. The AMPA and MPA-TBDMS derivatives mentioned above are very suitable candidates1D/2DGC-MS.

Cross-sectional view


Commonly used chemicals were of analytical reagent grade. MPA and EMPA were purchased from Sigma-Aldrich (St. Louis, MO, USA). cHMPA was obtained from Cambridge Isotope Laboratories (Tewksburg, MA, USA).N-methyl-Yes-(uncle-Butyldimethylsilyl)trifluoroacetamide (MTBSTFA) was purchased from GL Sciences (Tokyo, Japan). Bond Elut SAX Normal Type 500mg/3mL Strong Anion Exchange SPE cartridges were purchased from Agilent Technologies (Santa Clara, CA, USA).

IMPA is based on

1D GC-MS for matrix-free samples

pod, below1Under GC-MS conditions using a non-polar DB-5 LTM column, the five TBDMS derivatives of AMPA and MPA are clearly visible in the extracted ion chromatogram and well separated within 3 minutesrice/z153 irice/z267, although many other components in the derivatized reagents appeared in large numbers in the total ion chromatogram (Figure 3). The peak permeability at half height is very narrow, i.e. H. 0.008 min (MPA-TBDMS derivative), 0.01 min (EMPA, IMPA and PMPA).


Adequate isolation of target compounds and good separation from sample matrix components and derivatizing reagent peaks can be achieved by choosing appropriate analytical conditions. this one1D/2A D-GC-MS instrument consisting of a DB-5-LTM first column, a DB-17-LTM second column, and a Deans Switch was found to be effective in targeting AMPA and MPA-TBDMS derivative extracts and acid-enriched solutions. Although the LOD values ​​for


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      The acceptor phase obtained after PALME is sufficiently purified for direct injection into the LC-MS. In fact, it is worth noting that the DES-PALME method is applied directly to urine samples without any pre-treatment such as centrifugation, dilution or the use of expensive syringe filters, simplifying and significantly reducing the time and costs of the entire analysis process. All LOQs obtained were well below (8 to 1000 times lower by AMPA) the limit of detection (more than 40 ng/mL) required for the determination of neurotoxin hydrolysates in neurotoxin-exposed urine samples [52]. ]. Furthermore, the developed method can be used in a confidence-building exercise in the analysis of biomedical samples organized by the Organization for the Prohibition of Chemical Weapons (OPCW), in which participating laboratories are required to detect metabolites of chemical warfare agents in biomedical samples in the range of 0.5 to 100 ng/mL, depending on the type of compound of interest and the complexity of the sample being analyzed.

      Alkylmethylphosphonic acid (AMPA) is the main metabolite of organophosphate nerve poisons. A method for extraction from urine samples was developed and applied, which is based on the use of natural hydrophobic deep eutectic solvents as supporting liquid membranes in parallel artificial liquid microextraction (PALME) in combination with LC-MS/MS analysis.

      PALME is a microfluidic extraction method performed in a multi-well plate format, where the aqueous sample and aqueous receptor phases are separated by a flat membrane impregnated with an organic solvent. In this study, we investigated the possibility of replacing harmful conventional organic solvents with a new green solvent, a coumarin/thymol-based deep eutectic solvent, in order to improve the environmental acceptability of sample preparation methods.

      According to AMPA, the linear response is determined in the interval 0.5, 5 or 10-100 ng/mL with the coefficient of determination (R2s) ranging from 0.9751 to 0.9989 for the determination of untreated urine samples. Enrichment factors (EF) up to 12.65 were obtained with reproducibility ranging from 8.90 to 16.28% RSD (n=12). The limit of quantification (LOQ: S/N ≥ 10) ranged from 0.04 to 5.35 ng/mL throughout the assay. With good sensitivity, the proposed method allows the processing of 192 samples in 120 minutes (equivalent to 37.5 s/sample), which makes it ideal for biomonitoring of civilians or military personnel exposed to neurotoxins when they occur. One of the most powerful preparedness techniques for public health emergencies. In fact, the developed method combines sensitivity, high throughput, green color, simplicity and convenience for the determination of five acidic polar AMPAs in urine samples.

    • Methodological aspects of methylphosphonic acid analysis: Determination in river and coastal water samples

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      Various analytical methods are available for the determination of MPn in various sample matrices. Most of these methods are described in the context of chemical warfare analysis, since MPn is also a degradation product of organophosphate nerve agents [8], and most methods are based on gas chromatography (GC) [8-11] or liquid chromatography (LC) [12 -14] coupled with mass spectrometry (MS). MPn analysis by GC requires a derivatization step such as methylation or silylation [15] to ensure sufficient volatility for GC separation.

      Methylphosphonic acid (MPn) is thought to play an important role in aquatic systems such as rivers or the open ocean. In order to gain a deeper understanding of the meaning of MPn, e.g. B. for the phosphorus cycle in water, an analytical method for quantitative determination was developed. The method is based on the use of isotopically labeled internal standards and sample preparation including solid phase extraction (SPE). Instrumental detection by GC-MS after MPn derivatizationN-tert-butyldimethylsilyl-N-Methyltrifluoroacetamide (MTBSTFA). The study compared different isotopically labeled compounds as well as different SPE materials. A desalination process using electrodialysis was implemented because high salinity water samples would reduce the recovery of the selected SPE material. Finally, water samples from different water systems along the German Baltic Sea coast were analyzed to gain an initial understanding of the importance of MP in these systems. MPn concentrations were found in the low µg/L range.

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      In environmental chemistry, SPE-MDGC has been reported to be useful for the determination of SVOC pollution [74], emerging micropollutants [75,76], endocrine disruptors [77] and for the separation of naphthenic acid fractions from the oil sands process in body water [78]. ]].,79] and non-targeted assessment of steroid fate during wastewater treatment using commercial SPE [80] and MIP [81]. This technique has been reported in forensics for the targeted analysis of hydrolyzate derivatives of neurotoxins [82], anabolic agents [83] and urinary steroid compounds [84]. Furthermore, drug metabolites in hair were studied using MIP as a SPE material [85].

      When transferring an analytical method from one-dimensional gas chromatography (MDGC) to multidimensional gas chromatography (MDGC), certain parameters require special attention. Sample preparation (SP) and sample introduction are usually the least considered. However, even state-of-the-art MDGC methods cannot compensate for poor SP and injection. Therefore, it is definitely worth re-evaluating these analytical steps when the method is ported to MDGC. This chapter provides a brief overview of SP fundamentals and applications, as well as introductory techniques commonly used in MDGC. Additionally, the impact of these techniques on the chromatographic process and analytical results is discussed. The considerations presented here should be useful information for those new to MDGC.

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      Density functional theory (DFT) calculations were also performed to study the origin of debris within the PFB-RMPA source. MPA, EMPA, and PMPA (pinacylmethylphosphonic acid, a degradation product of soman) were obtained from Aldrich (Milwaukee, WI, USA), IMPA (isopropylmethylphosphonic acid, a degradation product of sarin), CHMPA (cyclohexylmethyl phosphonic acid, a degradation product of cyclohexylsarin) ), and iBuMPA (isobutylmethylphosphonic acid, RVX degradation product) were prepared in our laboratory [17]. Pentafluorobenzyl bromide was purchased from Tokyo Chemical Industry (Tokyo, Japan), and Bond Elut SAX cartridges (500 mg/3 ml, strong anion exchange SPE cartridges) were purchased from Agilent Technologies, Inc. (Santa Clara, CA, USA).

      In the work presented here, a screening method was developed for the detection and identification of RMPA (degradation product of a nerve agent) after pentafluorobenzylation using liquid chromatography tandem mass spectrometry (LC-MS/MS). Using this method, all RMPAs, including highly hydrophilic types such as methylphosphonic acid (MPA) and ethylmethylphosphonic acid (EMPA), are well retained on commonly used reverse-phase columns (retention times: 15.7 and 11.0 min), and there is greater determination efficiency of RMPA compared to conventional direct LC-MS/MS methods. Detection limits of RMPA using this method (<33 ng) were generally better than those observed by direct LC-MS/MS after pentafluorobenzylation (<74 ng) and gas chromatography-mass spectrometry (GC-MS) (< 1.1 μg). The applicability of the newly developed method on real samples was evaluated using urine/serum recovery tests and swab tests on different surfaces.

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    What is GC-MS analysis used for? ›

    Analyzing small and volatile molecules

    When combined with the detection power of mass spectrometry (MS), GC-MS can be used to separate complex mixtures, quantify analytes, identify unknown peaks and determine trace levels of contamination.

    What is two dimensional gas chromatography mass spectrometry? ›

    Two-dimensional gas chromatography (GC×GC) is a powerful separation technique, allowing to reach unique separation resolution. GC×GC is thus well suited for the characterization of complex volatile and semi-volatile mixtures. This high peak capacity results from the addition of an extra GC dimension.

    What is the basic principle of GC-MS? ›

    The GC works on the principle that a mixture will separate into individual substances when heated. The heated gases are carried through a column with an inert gas (such as helium). As the separated substances emerge from the column opening, they flow into the MS.

    What is the difference between GC-MS and LC-MS? ›

    The key differences between GC/MS and LC/MS systems are that the GC/MS uses a gas mobile phase and heat to transport the sample and separate the mixture. LC/MS uses a liquid mobile phase and ionization for separation. But, even with this difference in mind, the two methods are more alike than different.

    What are the advantages of GC-MS over LC-MS? ›

    One of the major advantages of GC-MS compared to LC-MS is the high reproducibility of generated mass spectra using EI. The electron impact ionization process, used in GC-MS, is a hard ionization that results in the production of very reproducible mass spectra from one instrument to another.

    What are three types of mass spectrometry? ›

    • 1.1 AMS (Accelerator Mass Spectrometry)
    • 1.2 Gas Chromatography-MS.
    • 1.3 Liquid Chromatography-MS.
    • 1.4 ICP-MS (Inductively Coupled Plasma-Mass spectrometry )
    • 1.5 IRMS (Isotope Ratio Mass Spectrometry)
    • 1.6 Ion Mobility Spectrometry-MS.
    • 1.7 MALDI-TOF.
    • 1.8 SELDI-TOF.

    What is the difference between HPLC and mass spectrometry? ›

    While liquid chromatography separates mixtures with multiple components, mass spectrometry provides spectral information that may help to identify (or confirm the suspected identity of) each separated component.

    Is mass spec the same as gas chromatography? ›

    Gas chromatography analysis separates compounds in complex mixtures, and mass spectroscopy analysis determines the molecular weight and ionic fragments of individual components, aiding in the identification of those compounds.

    Is GC-MS Qualitative or quantitative? ›

    The qualitative GC-MS analysis is conducted by matching the retention time of given unknowns and mass spectra of known chemicals, typically electron ionization (EI) mass spectra with known standards or libraries.

    How do you read a GC-MS report? ›

    The first page of an NDA GCMS report displays the gas chromatogram. Each peak of the graph corresponds to a specific essential oil constituent. The 'x' (horizontal) axis shows the retention time (RT), which, in other words, is the time taken (in minutes) for each separated compound to move to the end of the GC column.

    What does GC-MS stand for in drug testing? ›

    The most sophisticated drug-testing approach is gas chromatography coupled with mass spectrometry (GC/MS), which is regarded as a "gold standard"; it is used in confirmatory testing. Typically, GC/MS is preceded by a rapid immunoassay method to eliminate the majority of the "negative" samples.

    What data does GC-MS give? ›

    Data from a GC-MS is three-dimensional, providing mass spectra that can be used for identity confirmation or to identify unknown compounds plus the chromatogram that can be used for qualitative and quantitative analysis.

    Why is GC-MS better than HPLC? ›

    On the whole, GC is more cost-efficient than HPLC. This is because the solvents used in HPLC are more expensive than buying gas containers, and a pressure pump is needed to push the mobile phase through the column in liquid chromatography, which adds to the cost of equipment.


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