Differences In Retention Times Research Articles

Measurement Uncertainty and Validation for Quantification of Marijuana Metabolite: (−)-11-nor-9-Carboxy-Δ9-THC in Human Urine by GC-MS/MS

Background: Since the International Olympic Committee (IOC) was established, sports doping control analyses have revealed a high rate of positive cases for cannabinoids. Cannabinoids were banned in all sports where they were used in competition as per the Prohibited List published annually. Further, it was also included in the threshold drug category. Consequently, developing a reliable method for urine Cannabinoids metabolite quantification plays a pivotal role in sports dope testing. Objective: This work aimed to develop and validate a reliable, cost-effective, robust gas chromatography-tandem mass spectrometry method for detecting (−)-11-nor-9-Carboxy-Δ9- THC component in human urine samples, in compliance with ICH and WADA guidelines. Method: The sample preparation was done by enzymatic hydrolysis for deconjugation, further proceeded with solid phase extraction (SPE), liquid-liquid extraction (LLE), and using an XAD2 column, and N-methyl trimethylsilyl trifluoroacetamide (MSTFA) for derivatization. Results: The linearity was obtained in a range of 50–300 ng/mL, and the correlation coefficient was found to be higher than 0.99. Throughout the entire validation study, the difference in Retention Time (RT) for the analyte, including the Internal Standard (IS), was shown to be less than 1.0%. The quantification limit (LOQ) was calculated at a level of 50 ng/mL in human urine samples for the 3 most abundant ion transitions. The detection limit (LOD) was established at 4 ng/mL. Conclusion: The accuracy, precision, linearity, recovery, quantification limit, and selectivity by GC-MS/MS technique were found acceptable and well satisfactory while following the ICH guidelines. The developed method has been proven to be fit for purpose in accordance with the enforced Guidelines of WADA.

GRable Version 1.0: A Software Tool for Site-Specific Glycoform Analysis With Improved MS1-Based Glycopeptide Detection With Parallel Clustering and Confidence Evaluation With MS2 Information

High-throughput intact glycopeptide analysis is crucial for elucidating the physiological and pathological status of the glycans attached to each glycoprotein. Mass spectrometry-based glycoproteomic methods are challenging because of the diversity and heterogeneity of glycan structures. Therefore, we developed an MS1-based site-specific glycoform analysis method named "Glycan heterogeneity-based Relational IDentification of Glycopeptide signals on Elution profile (Glyco-RIDGE)" for a more comprehensive analysis. This method detects glycopeptide signals as a cluster based on the mass and chromatographic properties of glycopeptides and then searches for each combination of core peptides and glycan compositions by matching their mass and retention time differences. Here, we developed a novel browser-based software named GRable for semi-automated Glyco-RIDGE analysis with significant improvements in glycopeptide detection algorithms, including "parallel clustering." This unique function improved the comprehensiveness of glycopeptide detection and allowed the analysis to focus on specific glycan structures, such as pauci-mannose. The other notable improvement is evaluating the "confidence level" of the GRable results, especially using MS2 information. This function facilitated reduced misassignment of the core peptide and glycan composition and improved the interpretation of the results. Additional improved points of the algorithms are "correction function" for accurate monoisotopic peak picking; one-to-one correspondence of clusters and core peptides even for multiply sialylated glycopeptides; and "inter-cluster analysis" function for understanding the reason for detected but unmatched clusters. The significance of these improvements was demonstrated using purified and crude glycoprotein samples, showing that GRable allowed site-specific glycoform analysis of intact sialylated glycoproteins on a large-scale and in-depth. Therefore, this software will help us analyze the status and changes in glycans to obtain biological and clinical insights into protein glycosylation by complementing the comprehensiveness of MS2-based glycoproteomics. GRable can be freely run online using a web browser via the GlyCosmos Portal (https://glycosmos.org/grable).

Systematic Preparation of a 66-IgG Library with Symmetric and Asymmetric Homogeneous Glycans and Their Functional Evaluation.

Immunoglobulin G (IgG) antibodies possess a conserved N-glycosylation site in the Fc domain. In FcγRIIIa affinity column chromatography, unglycosylated, hemiglycosylated, and fully glycosylated IgG retention times differ considerably. Using retention-time differences, 66 different trastuzumab antibodies with symmetric and asymmetric homogeneous glycans were prepared systematically, substantially expanding the scope of IgGs with homogeneous glycans. Using the prepared trastuzumab with homogeneous glycans, thermal stability and antibody-dependent cellular cytotoxicity were investigated. In some glycan series, a directly proportional relationship was observed between the thermal unfolding temperature (Tm) and the calorimetric unfolding heat (ΔHcal). Antibody function could be deduced from the combination of a pair of glycans in an intact form. Controlling glycan structure through the combination of a pair of glycans permits the precise tuning of stability and effector functions of IgG. Overall, our technology can be used to investigate the effects of glycans on antibody functions.

Comprehensive two-dimensional gas chromatography using a miniaturized multiloop splitter-based non-cryogenic artificial trapping (M-SNAT) modulation device for analysis of cannabis samples

Multiloop splitter-based non-cryogenic artificial trapping (M-SNAT) modulation technique was developed, miniaturized and applied in comprehensive two-dimensional gas chromatography (GC×GC) for analysis of cannabis samples. The approach employed deactivated fuse silica (DFS) columns configured into multiple loop splitter system halving the perimeters of the progressively upstream loops. This splitter device was located between the first (1D) semi-nonpolar column outlet and a microfluidic Deans switch (DS). Each splitter loop splits a peak into two subpeaks having the same area with different void times. Three loops were then applied resulting in the number of the split subpeaks (nsplit) of 8 for each peak, and retention time differences between any two adjacent subpeaks (∆tR,split) were the same. By applying periodic heartcut event (H/C) within every artificial modulation period (PAM) of nsplit×∆tR,split, comprehensive split-and-trapped modulation profiles of analytes could be selectively transferred onto the second (2D) polar column (30 m) without cryogen consumption. This artificial modulation system was applied for analysis of cannabis samples with enhanced 2D peak capacity (2nc∼15). The established method was applied to analyse cannabis extracts using vegetable oils with or without frying process. This reveals 454 different peaks with 76, 92, 35 and 70 specific components specifically observed by using olive oil extraction (OE), fried OE, coconut oil extraction (CE) and fried CE, respectively.

Stability indicating for Quality Control Assessment of three antidiabetic molecules using HPLC technique: Stability Assessment of three antidiabetic molecules

Diabetes mellitus responds better to co-formulated tablet dosages of dapagliflozin (DFZN), metformin (MFMN), and vildagliptin (VDGN). For the purpose of studying stability and quantifying DFZN, VDGN, and MFMN in bulk forms and in dosage forms, an efficient and fast HPLC method of analysis is currently developed. The mobile phase featured 80:20 (v/v) 0.2 M, pH 3.0, ammonium acetate buffer and acetonitrile mixed together and Luna's HPLC C-18 column, named Phenyl hexyl, was utilised for DFZN, VDGN, and MFMN separation and its quantification. The PDA type detector operating at 235 nm wavelength was deployed. The “International Conference on Harmonisation” recommendations were strictly adhered throughout the validation process. A strong linear association between response and quantity in the range of 2.5–15 µg/ml (DFZN), 25–150 µg/ml (VDGN), and 125–750 µg/ml (MFMN) is supported by the regression information for the DFZN, VDGN, and MFMN calibration plots. The precision, selectivity, accuracy, sensitivity, ruggedness and robustness were satisfactory for the method. The tablet sample of DFZN, VDGN, and MFMN was subjected to acid, water, base, sodium bisulfite, light, dry heat and peroxide degradations. Significant differences in retention times were observed between the well-resolved peaks of the degradants and the primary peaks (DFZN, VDGN, and MFMN). Thus, the assay might be characterised as stability indicating. The contents of DFZN, VDGN, and MFMN in dosage forms were assessed precisely and accurately by currently developed HPLC technique. This technique may be applied to ensure the quality of formulation doses for DFZN, VDGN, and MFMN contents.

Weak geostrophic wind driven ventilation in street canyons with trees and green walls: Cooperating or opposing dispersions of airborne pollutants?

Urban high-rise buildings and dense street canyons significantly disrupt synchronised wind flows, potentially exacerbating urban heat island effect. Fortunately, urban heat island effect can be mitigated by the green infrastructure in cities, particularly through the presence of roadside trees and green walls. However, the combined mechanisms of tree resistance, shading effects, and cooling effect, along with sensible thermal buoyancy flows within canyon ventilation and pollution dispersion, remain undisclosed. This study employs refined computational fluid dynamics numerical simulations to analyse airflow and pollutant dispersion within urban street canyons. Air exchange rate and pollutant retention time are employed to evaluate ventilation and pollutant dispersion, respectively, inside the street canyons.In scenarios with leeward green wall layout, higher tree canopy spread and trunk height lead to a shift in high pollutant concentrations from the region near the windward side to that near the leeward side of the typical canyon (H/W = 1). Conversely, in deep canyons (H/W = 5), most pollutants are retained near the bottom leeward side. Moreover, differences in pollutant dispersion between typical and deep canyons increase with with rising tree canopy spread. Additionally, higher tree canopy spread and trunk height values result in longer pollutant retention time, which are unfavourable for pollutant removal, and particularly limiting pollutant dispersion as street canyon depth increases. Similarly, increasing tree canopy spread reduces the difference in air exchange rate between windward and leeward green wall layout patterns. Regarding Richardson number variations —indicating thermal buoyancy effects—lower Richardson number values lead to reduced differences in pollutant retention time between typical and deep canyons. Furthermore, ventilation performance of the windward green pattern surpasses that of the leeward pattern. This research provides valuable insights for implementing green infrastructure to locally mitigate urban air pollution.

Effect of sequential gemcitabine and epirubicin therapy on high-risk non-muscle invasive bladder cancer following transurethral bladder tumour resection

Purpose: To investigate the efficacy of sequential gemcitabine and epirubicin therapy on high-risk non-muscle invasive bladder cancer (NMIBC) after transurethral resection of bladder tumour (TURBT). Methods: The records of 100 high-risk NMIBC patients, who underwent TURBT at the Tongling People's Hospital, Tongling City, China between January 2020 and March 2023 were retrospectively analyzed. A total of 46 patients, treated with epirubicin after operation, were assigned to control group, while 54 patients, treated with both gemcitabine and epirubicin, were included in the study group. DKK-1 and YKL-4 levels were assayed by immunomagnetic bead‐based liquid chip technology and enzyme-linked immunosorbent assay, respectively. Furthermore, treatment efficacy was determined and compared between the two groups. Results: There were no significant differences in the pre-treatment DKK-1 and YKL-40 levels between the two groups (p > 0.05). However, both groups experienced a significant drop in post-treatment levels, with significantly lower post-treatment levels in the study group (p < 0.05). There were no significant differences in catheter retention time and hospitalization time between the two groups (p > 0.05). The study group achieved a significantly better overall response rate than the control group. The pre-treatment SF-36 scores of the two groups were similar, while their post-treatment SF-36 scores increased significantly (p < 0.05). Conclusion: Sequential therapy with gemcitabine and epirubicin is effective in the therapy of high-risk NMIBC after TURBT. It significantly lowers DKK-1 and YKL-40 levels, improves postoperative quality of life and reduces the postoperative recurrence rate without increasing adverse reactions and affecting the catheter retention and hospitalization times. A more comprehensive analysis is required to obtain improved outcomes.

Stereoselective Amine-omics Using Heavy Atom Isotope Labeled l-and d-Marfey's Reagents.

Biological amines and amino acids play essential roles in many biochemical processes. The chemical complexity of biological samples is challenging, and the selective identification and quantification of amines and amino acid stereoisomers would be very useful for amine-focused "amino-omics" studies. Many amines and amino acids are chiral, and their stereoisomers cannot be resolved on achiral media without chiral derivatization. In prior studies, we demonstrated the use of Marfey's reagent─a chiral derivatization reagent for amines and phenolic OH groups─for the LC-MS/MS resolution and quantification of amines and amino acid stereoisomers. In this study, a heavy atom isotope labeled Marfey's reagent approach for the stereoselective detection and quantification of amines and amino acids was developed. Heavy (13C2) l-Marfey's (Hl-Mar) and heavy (2H3) d-Marfey's (Hd-Mar) were synthesized from 13C2-l-Ala and 2H3-d-Ala, respectively. Both light and heavy Marfey's reagents were used to derivatize standard amine mixtures, which were analyzed by LC-QToF-HRMS. Aligned peak lists were comparatively analyzed by light vs heavy Mar mass differences to identify mono-, di-, and tri-Marfey's adducts and then by the retention time difference between l- and d-Mar derivatives to identify stereoisomers. This approach was then applied to identify achiral and chiral amine and amino acid components in a methicillin-resistant Staphylococcus aureus (MRSA) extract. This approach shows high analytical selectivity and reproducibility.

Isomeric Separation of α2,3/α2,6-Linked 2-Aminobenzamide (2AB)-Labeled Sialoglycopeptides by C18-LC-MS/MS.

Determination of the relative expression levels of the α2,3/α2,6-sialic acid linkage isomers on glycoproteins is critical to the analysis of various human diseases such as cancer, inflammation, and viral infection. However, it remains a challenge to separate and differentiate site-specific linkage isomers at the glycopeptide level. Some derivatization methods on the carboxyl group of sialic acid have been developed to generate mass differences between linkage isomers. In this study, we utilized chemical derivatization that occurred on the vicinal diol of sialic acid to separate linkage isomers on a reverse-phase column using a relatively short time. 2-Aminobenzamide (2AB) labeling derivatization, including periodate oxidation and reductive amination, took only ∼3 h and achieved high labeling efficiency (>90%). Within a 66 min gradient, the sialic acid linkage isomers of 2AB-labeled glycopeptides from model glycoproteins can be efficiently resolved compared to native glycopeptides. Two different methods, neuraminidase digestion and higher-energy collision dissociation tandem mass spectrometry (HCD-MS2) fragmentation, were utilized to differentiate those isomeric peaks. By calculating the diagnostic oxonium ion ratio of Gal2ABNeuAc and 2ABNeuAc fragments, significant differences in chromatographic retention times and in mass spectral peak abundances were observed between linkage isomers. Their corresponding MS2 PCA plots also helped to elucidate the linkage information. This method was successfully applied to human blood serum. A total of 514 2AB-labeled glycopeptide structures, including 152 sets of isomers, were identified, proving the applicability of this method in linkage-specific structural characterization and relative quantification of sialic acid isomers.

Development of an optically induced dielectrophoresis (ODEP) microfluidic system with a virtual gel filtration chromatography (GFC)-inspired mechanism for the high-performance sorting and separation of microparticles based on their size differences

Size-based sorting and separation of microparticles is critical for many applications. Conventional techniques might not be suitable for this task particularly when sample is limited. Integration of optically induced dielectrophoresis (ODEP) in microfluidic system for the task is believed promising. However, its utilization can be limited by the influence of the friction force acting on microparticles. In this situation, the microparticles might not be effectively sorted and separated. To address this challenge, this study presented an ODEP-based virtual gel filtration chromatography (GFC)-inspired mechanism. By mimicking the concept of GFC, this study proposed to use a circular light image array to maximize the retention time difference among various microparticles when they flowed through such an array. In this study, the array design and its operational conditions were determined. Additionally, its performance for sorting and separation of polystyrene (PS) microbeads with 4 different sizes was evaluated. Results demonstrated that the proposed method was capable of sorting and separating microbeads in a high-performance manner (e.g., purity range: 92–100%). This could be beyond what is currently possible using the current ODEP-based method. Overall, this study presented a new ODEP technique that could solve the problems commonly encountered in ODEP-based microparticle sorting, and separation.

Water quality performance assessment of two stormwater detention basins located in the recharge zone of a karst aquifer

Stormwater detention basins are used to minimize peak discharges and improve water quality mainly through sedimentation; however, limited studies have evaluated the water quality performance of detention basins located over karst aquifers. Karst aquifers are vital sources of drinking water for many regions of the world and their recharge areas are susceptible to contamination from surface water resources. In this study, an analysis of two stormwater detention basins (namely, Kyle and TPC) located in the recharge zone of one of the most prolific karst aquifers in the world (Edwards Aquifer, San Antonio, Texas), were conducted over a period of one year to quantify the water quality and hydrologic performance of the basins. Automated samples were collected during the storm events and analyzed for nitrate (NO3−-N), nitrite (NO2−-N), ammonia (NH3–N), total dissolved nitrogen (TDN), phosphorus (PO43−), total suspended solids (TSS), total dissolved solids (TDS), total carbon (TC), total organic carbon (TOC), and chemical oxygen demand (COD). Both basins reduced NH3–N, TSS and COD concentrations significantly while NO3−-N and PO43− concentrations exhibited a net export. Furthermore, TPC showed greater reductions in NO2−-N, TOC and TC concentrations compared to Kyle. Higher TSS removal was observed at TPC due to differences in retention time. A volume reduction of 44% and 64% was observed in TPC and Kyle, respectively. The results of this study demonstrate that stormwater detention basins located over the Edwards Aquifer effectively remove particulate pollutants while also being a potential source of dissolved pollutants such as nitrate. Overall, the results presented here have important implications for operation and maintenance of stormwater basins constructed over recharge zones of Edwards Aquifer.

Cumulative Neutral Loss Model for Fragment Deconvolution in Electrospray Ionization High-Resolution Mass Spectrometry Data.

Clean high-resolution mass spectra (HRMS) are essential to a successful structural elucidation of an unknown feature during nontarget analysis (NTA) workflows. This is a crucial step, particularly for the spectra generated during data-independent acquisition or during direct infusion experiments. The most commonly available tools only take advantage of the time domain for spectral cleanup. Here, we present an algorithm that combines the time domain and mass domain information to perform spectral deconvolution. The algorithm employs a probability-based cumulative neutral loss (CNL) model for fragment deconvolution. The optimized model, with a mass tolerance of 0.005 Da and a scoreCNL threshold of 0.00, was able to achieve a true positive rate (TPr) of 95.0%, a false discovery rate (FDr) of 20.6%, and a reduction rate of 35.4%. Additionally, the CNL model was extensively tested on real samples containing predominantly pesticides at different concentration levels and with matrix effects. Overall, the model was able to obtain a TPr above 88.8% with FD rates between 33 and 79% and reduction rates between 9 and 45%. Finally, the CNL model was compared with the retention time difference method and peak shape correlation analysis, showing that a combination of correlation analysis and the CNL model was the most effective for fragment deconvolution, obtaining a TPr of 84.7%, an FDr of 54.4%, and a reduction rate of 51.0%.

Identification of Acid Red 73 (CI 27290) in Cosmetic Hair Dye Preparations by High-Performance Liquid Chromatography – Photo Diode Array

Acid Red 73 (CI 27290) is a prohibited component in cosmetics, particularly in hair color formulations. The purpose of this investigation is to discover the coloring additive Acid Red 73 in cosmetic hair dye formulations. Acid Red 73 (CI 27290) is a sulfonated azo dye that is manufactured to be more hazardous than other colors and is damaging to the body. Based on variations in polarity and solubility, Acid Red 73 (CI 27290) is separated from the sample matrix and identified using High Performance Liquid Chromatography-Photo Diode Array (HPLC-PDA). The findings obtained from the tested samples satisfied the criteria since they did not include Acid Red 73 (CI 27290), as indicated by the difference in retention time and wavelength between the sample, the standard solution, and the spiked sample solution on the chromatogram.

Chatbot-assisted therapy for patients with methamphetamine use disorder: a preliminary randomized controlled trial.

Methamphetamine (MA) use disorder is associated with a large public health burden. Despite the therapeutic effects of psychosocial interventions based on current evidence, finding an approach to retain patients in treatment remains a real-world challenge. The rapid development of mobile health (mHealth) systems suggests the potential to provide real-time personalized care at any time and from any location, minimize barriers to treatment, maximize use, and promote the dissemination of accessible therapeutic tools in at-risk populations. Our study aimed to investigate the feasibility and effectiveness of chatbots for the treatment of MA use disorder. The inclusion criteria were (a) a diagnosis of MA use disorder as defined by the DSM-5, (b) age between 18 and 65 years, (c) no acute exacerbation of severe mental illness during the initial assessment, such as schizophrenia or bipolar I disorder, (d) willingness to participate in standard outpatient treatment for ≥ 6 months, and (e) an Android phone. Participants were randomly allocated to either a chatbot-assisted therapy via smartphone (CAT) group or a control group following simple randomization procedures (computerized random numbers) without blinding. All participants were followed up for 6 months. Treatment retention and monthly urine test results were analyzed as outcome measures. Participants' satisfaction with CAT was also assessed. In total, 50 and 49 participants were allocated to the CAT and control groups, respectively. There were no significant differences in retention time between the two treatment groups (df = 1, p = 0.099). The CAT group had fewer MA-positive urine samples than the control group (19.5% vs. 29.6%, F = 9.116, p = 0.003). The proportion of MA-positive urine samples was positively correlated with the frequency of MA use (r = 0.323, p = 0.001), severity of MA use disorder (r = 0.364, p < 0.001), and polysubstance use (r = 0.212, p = 0.035), and negatively correlated with readiness to change (r = -0.330, p = 0.001). Totally 55 participants completed the study at the 6-month follow-up and 60% reported relative satisfaction. Participants in this study had favorable acceptance and generally positive outcomes, which indicates that chatbot is feasible for treating people who use MA.

Improved LC–MS identification of short homologous peptides using sequence-specific retention time predictors

Peptides are an important group of compounds contributing to the desired, as well as the undesired taste of a food product. Their taste impressions can include aspects of sweetness, bitterness, savoury, umami and many other impressions depending on the amino acids present as well as their sequence. Identification of short peptides in foods is challenging. We developed a method to assign identities to short peptides including homologous structures, i.e. peptides containing the same amino acids with a different sequence order, by accurate prediction of the retention times during reversed phase separation. To train the method, a large set of well-defined short peptides with systematic variations in the amino acid sequence was prepared by a novel synthesis strategy called ‘swapped-sequence synthesis’. Additionally, several proteins were enzymatically digested to yield short peptides. Experimental retention times were determined after reversed phase separation and peptide MS2 data was acquired using a high-resolution mass spectrometer operated in data-dependent acquisition mode (DDA). A support vector regression model was trained using a combination of existing sequence-independent peptide descriptors and a newly derived set of selected amino acid index derived sequence-specific peptide (ASP) descriptors. The model was trained and validated using the experimental retention times of the 713 small food-relevant peptides prepared. Whilst selecting the most useful ASP descriptors for our model, special attention was given to predict the retention time differences between homologous peptide structures. Inclusion of ASP descriptors greatly improved the ability to accurately predict retention times, including retention time differences between 157 homologous peptide pairs. The final prediction model had a goodness-of-fit (Q2) of 0.94; moreover for 93% of the short peptides, the elution order was correctly predicted.Graphical abstract

Application value of image fusion technology in transcatheter aortic valve implantation

Objective: To analysis the application value of image fusion technology in transcatheter aortic valve implantation (TAVI). Methods: A total of 35 patients underwent trans-femoral TAVI using the first-generation VENUS-A valve in Heart Center of Henan Provincial People's Hospital from January 2020 to May 2021 were analyzed retrospectively. Among them, there were 21 males and 14 females, aged from 64 to 81 years, with a mean (SD) of (71.37±5.66) years. They were divided into conventional group (n=22) and fusion group (n=13), according to whether image fusion technology was used during operation. The preoperative general data, intraoperative data, differences of postoperative renal function and residence time in intensive care unit (ICU) were analyzed and compared between the two groups. The postoperative echocardiography and 12 lead ECG were observed. Results: All 35 patients in this study were with severe aortic stenosis, of which, 10 patients were complicated with moderate to severe regurgitation. Compared with the conventional group, the intraoperative fusion group had fewer angiography times [3.0 (3.0, 4.0) vs 5.0 (5.0, 6.0)], X-ray absorbed dose [342.0 (44.5) mGy vs 388.4 (71.0) mGy], and contrast dosage [(73.5±10.5) ml vs (90.3±10.3) ml], and shorter rapid pacing time [(14.0±1.6) seconds vs (16.5±2.0) seconds] (all P<0.05). There was no significant differences in X-ray irradiation time, operation time, sizing of the pre-dilated balloon, valve implantation depth and other indicators (all P>0.05). There was no significant differences in ICU retention time and postoperative renal function (all P>0.05). Postoperative echocardiography showed that the function of aortic valve was good, with mild perivalvular leakage in 2 cases in the conventional group and 1 case in the fusion group; and one patient was implanted with permanent pacemaker after TAVI in the conventional group. Conclusion: Image fusion technology simplifies the TAVI process, shortens the ventricular pacing time and reduces the dosage of X-ray and contrast, and has certain clinical application value.

Analysis of doping control samples using supercritical fluid chromatography-tandem mass spectrometry: Ready for routine use.

Supercritical fluid chromatography is proving to be a good separation and sample preparation tool for various analytical applications and, as such, has gained the attention of the anti-doping community. Here, the applicability of supercritical fluid chromatography hyphenated to tandem mass spectrometry for routine doping control analysis was tested. A multi-analyte method was developed to cover 197 drugs and metabolites that are prohibited in sport. More than 1000 samples were analyzed by applying a "dilute and inject" approach after hydrolysis of glucuronide metabolites. Additionally, a comparison with routinely used liquid chromatography-mass spectrometry was performed with 250 of the 1000 samples and a number of past positive anti-doping samples. It revealed some features where supercritical fluid chromatography-tandem mass spectrometry was found to be complementary or advantageous to liquid chromatography-mass spectrometry for anti-doping purposes, such as better retention of analytes that are poorly retained in reversed-phase liquid chromatography. Our results suggest that supercritical fluid chromatography-tandem mass spectrometry is sensitive (limit of detection <50% relevant minimum required performance level required by the World Anti-Doping Agency for anti-doping analysis), reproducible, robust, precise (analytes of interest area coefficient of variation <5%; retention time difference coefficient of variation <1%) and complementary to existing techniques currently used for routine analysis in the World Anti-Doping Agency accredited laboratories.

Rapid Determination of Ethyl Carbamate in Chinese Liquor via a Direct Injection Mass Spectrometry with Time-Resolved Flash-Thermal-Vaporization and Acetone-Assisted High-Pressure Photoionization Strategy.

Ethyl carbamate (EC), a carcinogenic compound, is naturally produced in fermented foods and alcoholic beverages. Rapid and accurate measurement of EC is necessary and important for quality control and safety evaluation of Chinese liquor, a traditionally distilled spirit with the highest consumption in China, but it remains a great challenge. In this work, a direct injection mass spectrometry (DIMS) with time-resolved flash-thermal-vaporization (TRFTV) and acetone-assisted high-pressure photoionization (HPPI) strategy has been developed. EC was rapidly separated from the main matrix components, ethyl acetate (EA) and ethanol, by the TRFTV sampling strategy due to the retention time difference of these three compounds with large boiling point differences on the inner wall of a poly(tetrafluoroethylene) (PTFE) tube. Therefore, the matrix effect of EA and ethanol was effectively eliminated. The acetone-assisted HPPI source was developed for efficient ionization of EC through a photoionization-induced proton transfer reaction between EC molecules and protonated acetone ions. The accurate quantitative analysis of EC in liquor was achieved by introducing an internal standard method (ISM) using deuterated EC (d5-EC). As a result, the limit of detection (LOD) for EC was 8.88 μg/L with the analysis time of only 2 min, and the recoveries ranged from 92.3 to 113.1%. Finally, the prominent capability of the developed system was demonstrated by rapid determination of trace EC in Chinese liquors with different flavor types, exhibiting wide potential applications in online quality control and safety evaluation of not only Chinese liquors but also other liquor and alcoholic beverages.

Study of Efficiency of Capacity Gradient Ion-Exchange Stationary Phases

Highly efficient columns are necessary for the modern analytical applications of liquid chromatography. In this work, the separation efficiency of ion-exchange capacity gradient stationary phases combined with eluent concentration gradient was studied by a theoretical approach. In the course of our work three different scenarios of capacity gradients were used with different shapes (linear, convex and concave). The resolutions of different gradient columns were calculated for each scenario. As a reference, a uniform column was considered, which had the same analysis time as the non-uniform column. In the case of separation of ions with same charges, the gradient column offered only a marginal advantage compared to the uniform column due to the bandwidth compression caused by the capacity gradient. In the case of ions with different charges, however, the advantage of the gradient column was more significant. This was mainly due to the increased retention time difference of solutes. Ion-exchange capacity gradient columns may be a new way to separate ions more efficiently.

False Positive Identification of Pesticides in Food Using the European Standard Method and LC-MS/MS Determination: Examples and Solutions from Routine Applications

The latest standard method for pesticides in food and feed (EN 15662:2018) is now generally used in control laboratories. However, routine analyses of the combination of hundreds of compounds and food matrices highlighted that false positive identification of pesticides in particular food matrices does occur. The aim of the study was to show relevant precedents when thorough investigation was necessary to make a decision on possibly compliant/non-compliant samples. Examples include the pesticide/commodity combination of atrazine-desethyl in date seed coffee, mepanipyrim in parsley root, myclobutanil in white peppercorn, primisulfuron-methyl in herb extract, propham in elderberry, quinoclamine in fennel and tebufenpyrad in dried ginger. These examples, which were presented for the first time, indicated that the identification criteria for some pesticides in certain food matrices, according to the SANTE/11312/2021 guideline, might fail: the general criteria as stable retention time and ion ratio could lead to an incorrect qualification of pesticides. Standard addition was useful not only in compensating for the background during mass spectrometric detection under the confirmatory analysis, but also in the identification process when negligible retention time difference was observed between the analytes and the interfering matrix compounds.