Analyte protectant approach to protect amide-based synthetic cannabinoids from degradation and esterification during GC-MS analysis.

The forensic analysis of amide-based synthetic cannabinoids (SCs) in seized materials is routinely performed using gas chromatography-mass spectrometry (GC-MS); however, a major challenge associated with GC-MS is the thermolytic degradation of substances with sensitive functional groups. Herein, we report the comprehensive thermal degradation and ester transformation of amide-based SCs, such as AB-FUBINACA, AB-CHMINACA, and MAB-CHMINACA, during GC-MS analysis and their treatment with analyte protectants (APs). These SCs were found to undergo thermolytic degradation during GC-MS in the presence of non-alcohol solvents. Using methanol as an injection solvent resulted in the conversion of the amide group to an ester group, producing other SCs such as AMB-FUBINACA, MA-CHMINACA, and MDMB-CHMINACA. Degradant and ester product formation has been interpreted as the adsorption of target SCs on glass wool via hydrogen bonding interactions between the active silanol and amide groups of the SCs, followed by an addition and/or elimination process. The factors found to influence the thermal degradation and/or esterification of the amide functional group include residence time, activity of glass wool, and injection volume. This report presents the fragmentation patterns of all compounds that were produced by degradation and esterification. Using 0.5 % sorbitol (AP) in MeOH as an injection solvent resulted in complete protection and improvement of the chromatographic shape of the compounds. This method has been successfully confirmed in terms of sensitivity, linearity, accuracy, and precision for standard solutions and tablet extraction using 0.5 % sorbitol in MeOH. Using AP increased the sensitivity by ten times or more compared to the use of only MeOH. The limit of detection for all analytes was determined as 25 ng/mL, and the calibration curves were linear over the concentration range of 50-2000 ng/mL. The values of accuracy error were below 11 %, and precision was less than 13 %. The effects of phytochemicals of herbal products, tablet ingredients, and biological matrices on the degradation and/or esterification and APs performance have also been evaluated in this work.

Accuracy improvement of determination of seven minor tobacco alkaloids in mainstream cigarette smoke using analyte protectants by gas chromatography-mass spectrometry.

Tobacco alkaloids are important precursors of carcinogenic tobacco-specific nitrosamines. Therefore, accurate quantification of tobacco alkaloids is highly important. This study investigates the compensation effects of novel analyte protectants (APs) for matrix effects (MEs) to determine seven minor tobacco alkaloids (nornicotine, myosmine, anabasine, anatabine, nicotyrine, 2,3'-bipyridine, and cotinine) in mainstream cigarette smoke with high accuracy and robustness. By comparing the heights and shapes of the chromatographic peaks before and after the addition of APs to standard solutions prepared in dichloromethane and cigarette smoke solutions, the compensation effects of 12 APs and their combinations on the MEs of seven minor tobacco alkaloids were evaluated, and the best combination of 2-pyridylethylamine (2 mg/mL)+1,2-decanediol (1 mg/mL) was identified. This AP combination could effectively improve the shapes and increase the heights (by 7-371%) of chromatographic peaks for standard solutions prepared in dichloromethane and cigarette smoke solutions. Before the addition of this AP combination, the slope ratios of the calibration curves for two types of standard solutions of the seven target chemicals were 71.4-159.8%, while they were 87.4-105.6% after the addition, indicating that this AP combination reduced the matrix difference between pure solvent and cigarette smoke solution. After adding the AP combination, the standard curves of solutions prepared in dichloromethane showed good linearity (r2 ≥ 0.999), the spiked recoveries were between 80.9% and 119.6%, and the inter- and intraday precisions were between 1.5-9.5% and 3.1-8.5%, respectively. Three commercial cigarette samples and one mixed standard solution were also tested under four different instrument working conditions to verify the long-term accuracy and ruggedness of the approach in routine real-world analysis of the method. The results showed that the RSD values were higher (3.5-25.4%) without the AP combination than that (<6.7%) with the AP combination. Because of its high accuracy, precision, and robustness, this method has good practical prospects.

Thermal desorption gas chromatography-mass spectrometric analysis of polycyclic aromatic hydrocarbons in atmospheric fine particulate matter.

Thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) is used to analyze polycyclic aromatic hydrocarbons (PAHs) in atmospheric fine particulate matter. However, despite the high sensitivity of TD-GC-MS, the recovery rate of PAHs is greatly influenced by active sites in the equipment. PAHs are decomposed or adsorbed at active sites, decreasing quantitative accuracy. Also, the thermal extraction of PAHs is easily affected by the matrix in PM2.5 samples, decreasing the thermal extraction efficiency. Herein, the analytical sensitivities of PAHs were improved by adding analyte protectant (AP) and thermal desorption aid (TDA) as an auxiliary agent. The combination of 2 µL of 0.5 w/v% D-sorbitol (as AP) and 2 µL of 10 w/v% Tween®20 (as TDA) was found to be most effective in improving the analytical sensitivity of PAHs. The sensitivities of 5-6-ring PAHs with high boiling points increased most when analyzing blank filter papers added with PAHs standard sample or real samples of PM2.5 compared with the samples without the auxiliary agent. When analyzing real samples of PM2.5, the peak areas of 5-ring and 6-ring PAHs in the PM2.5 sample added with the optimized auxiliary agent were 1.40 and 1.96 times that without the auxiliary agent. It is considered that AP in the auxiliary agent covered active sites and protected PAHs undergoing decomposition or adsorption. TDA improved the thermal extraction rate of high boiling point PAHs. When using alternative heat sampling equipment to analyze low concentrations of high boiling point components, the auxiliary agent proposed herein can increase the analytical sensitivity toward the target compounds.

A modified quick, easy, cheap, effective, rugged, and safe method with hydrophobic natural deep eutectic solvent as extractant and analyte protectant for analyzing pyrethroid residues in tomatoes.

In this work, a novel quick, easy, cheap, effective, rugged, and safe technique with hydrophobic natural deep eutectic solvent as both extractant and analyte protectant was developed and combined with gas chromatography-tandem mass spectrometry to analyze pyrethroid residues in tomatoes. Eight hydrophobic natural deep eutectic solvents were first evaluated as analyte protectants and those with decanoic acid or lactic acid as hydrogen bond donor were demonstrated to be effective in compensating for the matrix effects of pyrethroids in the gas chromatography system. Hence, they were added to solvent standards for correcting the quantitation errors instead of matrix-matched calibration standards. Then the abilities of these acid-based deep eutectic solvents to extract pyrethriods from tomatoes were evaluated. Results showed the recoveries of all pyrethroids reached to over 80% with only 5 mL menthol:decanoic acid (1:1) used, and good phase separation was easily achieved without the addition of inorganic salt in the extraction step, indicating hydrophobic natural deep eutectic solvent could be a green substitute for acetonitrile in the quick, easy, cheap, effective, rugged, and safe extraction. Compared with the conventional method, the proposed protocol improved the recoveries, reduced the matrix effects, and simplified the extraction step, demonstrating to be an effective, fast, and green method.

Buprofezin dissipation and safety assessment in open field cabbage and cauliflower using GC/ITMS employing an analyte protectant.

An analytical method for the determination of buprofezin residues in cabbage and cauliflower was developed and validated using gas chromatography with ion trap mass spectrometry. The analyte protectant d-sorbitol was used at a concentration level of 0.5 mg mL-1 in acetonitrile instead of in matrix for constructing the calibration curves of the buprofezin standard. The average recoveries ranged from 91.3 to 96.8%, with an RSD of ≤2.7%. The limits of detection and quantitation of the method in cabbage and cauliflower were 1.3, 1.7 and 4.3, 6.2 µg kg-1 , respectively. The residual levels and dissipation kinetics of buprofezin 25% wettabe powder in cabbage and cauliflower cultivated under open field conditions was investigated at the single (T1) and double (T2) recommended rates of application. Half-life periods were found to be 1.73 and 2.1 days in cabbage, whereas in cauliflower, these values were 1.85 and 2.36 days at T1 and T2, respectively. Based on the dissipation study, and the maximum residue limit value of 0.05 mg kg-1 , the proposed pre-harvest interval of buprofezin in cabbage was 3-6 days and that in cauliflower was 4-10 days. The results showed that buprofezin is safe for application at both recommended application rates.

Problems and solutions of polyethylene glycol co-injection method in multiresidue pesticide analysis by gas chromatography-mass spectrometry: evaluation of instability phenomenon in type II pyrethroids and its suppression by novel analyte protectants.

Polyethylene glycol 300 is commonly used as a base material for "analyte protection" in multiresidue pesticide analysis via gas chromatography-mass spectrometry. However, the disadvantage of the co-injection method using polyethylene glycol 300 is that it causes peak instability in α-cyano pyrethroids (type II pyrethroids) such as fluvalinate. In this study, we confirmed the instability phenomenon in type II pyrethroids and developed novel analyte protectants for acetone/n-hexane mixture solution to suppress the phenomenon. Our findings revealed that among the examined additive compounds, three lipophilic ascorbic acid derivatives, 3-O-ethyl-L-ascorbic acid, 6-O-palmitoyl-L-ascorbic acid, and 6-O-stearoyl-L-ascorbic acid, could effectively stabilize the type II pyrethroids in the presence of polyethylene glycol 300. A mixture of the three ascorbic acid derivatives and polyethylene glycol 300 proved to be an effective analyte protectant for multiresidue pesticide analysis. Further, we designed and evaluated a new combination of analyte protectant compounds without using polyethylene glycol or the troublesome hydrophilic compounds. Consequently, we obtained a set of 10 medium- and long-chain saturated fatty acids as an effective analyte protectant suitable for acetone/n-hexane solution that did not cause peak instability in type II pyrethroids. These analyte protectants will be useful in multiresidue pesticide analysis by gas chromatography-mass spectrometry in terms of ruggedness and reliable quantitativeness. Graphical abstract Comparison of effectiveness of the addition of lipophilic derivatives of ascorbic acid in controlling the instability phenomenon of fluvalinate with polyethylene glycol 300.

Evaluation of the matrix effect on gas chromatography--mass spectrometry with carrier gas containing ethylene glycol as an analyte protectant.

The consequences of matrix effects in GC are a major issue of concern in pesticide residue analysis. The aim of this study was to evaluate the applicability of an analyte protectant generator in pesticide residue analysis using a GC-MS system. The technique is based on continuous introduction of ethylene glycol into the carrier gas. Ethylene glycol as an analyte protectant effectively compensated the matrix effects in agricultural product extracts. All peak intensities were increased by this technique without affecting the GC-MS performance. Calibration curves for ethylene glycol in the GC-MS system with various degrees of pollution were compared and similar response enhancements were observed. This result suggests a convenient multi-residue GC-MS method using an analyte protectant generator instead of the conventional compensation method for matrix-induced response enhancement adding the mixture of analyte protectants into both neat and sample solutions.

Pepper leaf matrix as a promising analyte protectant prior to the analysis of thermolabile terbufos and its metabolites in pepper using GC-FPD.

During gas chromatography (GC), the matrix can deactivate the active site during the transport of the compound from the injector to the detector. This deactivation capacity varies among matrices, as it is dependant on the concentrations of the different constituent compounds of each matrix. During the analysis of terbufos and its metabolites, two of its metabolites were highly thermolabile, and were readily decomposed inside the GC system. As the matrix can mask the active site, we carried out a matrix-matched calibration in an effort to protect the analyte against decomposition. As a component of our analysis, the pepper matrix was the first to be matched; however, it failed to completely protect the metabolites. Subsequently, a variety of different compounds, including 3-ethoxy-1,2-propanediol, gulonolactone, and sorbitol at 10, 1, and 1mg/mL were tested; however, none of these generated the desired effect. We surmised that some of the compounds may have decomposed inside the injection port, so we introduced a carbofrit inlet liner, which is highly inert. But, this step did not improve the protective qualities of the matrices. Finally, pepper leaf matrix was added to the pepper matrix, and we observed a profound protective effect for almost all of the analytes tested. A selective detector (flame photometric detector with phosphorus filter) was used to facilitate a high matrix concentration without interaction with the analyte. After resolving the problem of these two metabolites, terbufos and its five toxic metabolites were analyzed in pepper and pepper leaf samples. The recovery rates for terbufos and its metabolites were 73-114.5% with a relative standard deviation of <12%. This method was successfully applied to field samples, and terbufos sulfone, terbufos sulfoxide, and terbufoxon sulfoxide were found as residues in the suspected pepper and pepper leaf samples.