Rapid Analysis of Illegal Cationic Dyes in Foods and Surface Waters Using High Temperature Direct Analysis in Real Time High-Resolution Mass Spectrometry

Rhodamine and related substances in food: Recent updates on pretreatment and analysis methods

Rhodamine, a colorant prohibited in various consumer products due to its demonstrated carcinogenic, mutagenic, and toxic properties, necessitates the development of a straightforward, efficient, sensitive, environmentally friendly, and cost-effective analytical method. This review provides an overview of recent advancements in the pretreatment and determination techniques for rhodamine across diverse sample matrices since 2017. Sample preparation methods encompass both commonly used pretreatment techniques such as filtration, centrifugation, solvent extraction, and cloud point extraction, as well as innovative approaches including solid phase extraction, dispersive liquid-liquid microextraction, hollow fiber liquid phase microextraction, magnetic solid phase extraction, and matrix solid phase dispersion. The analytical techniques encompass high performance liquid chromatography, surface-enhanced Raman scattering, and sensor-based methods. Furthermore, a comprehensive examination is conducted to offer insights for future research on rhodamine regarding the advantages, disadvantages, and advancements in various pretreatment and determination methodologies.

Recent advances in the application of direct analysis in real time-mass spectrometry (DART-MS) in food analysis

Direct analysis in real time-mass spectrometry (DART-MS) has evolved as an effective analytical technique for the rapid and accurate analysis of food samples. The current advancements of DART-MS in food analysis are described in this paper. We discussed the DART principles, which include devices, ionization mechanisms, and parameter settings. Numerous applications of DART-MS in the fields of food and food products analysis published during 2018-2023 were reviewed, including contamination detection, food authentication and traceability, and specific analyte analysis in the food matrix. Furthermore, the challenges and limitations of DART-MS, such as matrix effect, isobaric component analysis, cost considerations and accessibility, and compound selectivity and identification, were discussed as well.

Facile fluorescence detection of malachite green in fish using molecularly imprinted polymers doped CdTe quantum dots based system

Malachite green (MG) possesses high toxicity, therefore, the detection of MG in fish tissues is of vital importance. A novel core-shell MIPs doped CdTe quantum dots coated silica nanoparticles (CdTe-MIP/SiO2 NPs) were synthesized via a simple one-pot strategy. The materials were characterized carefully. The resulting CdTe-MIP/SiO2 NPs were coated on the thin layer chromatography plate, and coupled with miniaturized fluorimeter for fluorescence detection of MG in fish samples. The resulting CdTe-MIP/SiO2 NPs based system possessed good linearity (0.01 ∼ 20 μmol/L), high recoveries (98.36 %∼101.45 %) and low detection limit (3.7 nmol/L) for MG. Furthermore, CdTe-MIP/SiO2 NPs based system were employed to measure fish samples spiked with MG, meanwhile, HPLC was utilized to evaluate the accuracy and reliability. And the paired t-test was conducted to evaluate differences between fluorescence method and HPLC, P > 0.05 means no significant difference was observed, the results demonstrated that both fluorescence method and HPLC are suitable for MG analysis.

Direct analysis in real time of high-quality extra virgin olive oils for the rapid and automatic identification of origin trademark

BACKGROUND

Following our previous research on the differentiation of Italian extra virgin olive oils (EVOOs) by rapid evaporative ionization mass spectrometry coupled to a tandem high resolution mass analyser, the present study deals with the evaluation of another direct mass spectrometry (direct-MS) approach for the rapid and automatic discrimination of EVOOs. In particular, direct analysis in real time (DART-MS) was explored as an ambient MS (AMS) source for the building of a top-quality Italian EVOOs database and fast identification of unknown samples. A single quadrupole detector (QDa) was coupled with DART, taking advantage of a cost-saving, user-friendly and less sophisticated instrumental setup. Particularly, quickstrip cards, located on a moving rail holder, were employed, allowing for the direct analysis of 12 EVOO spots in a total analysis time of 6 min. The aim was to develop a reliable statistical model by applying principal component and linear discriminant analyses to clusterize and classify EVOOs according to geographical origin and cultivar, as main factors determining their nutritional and sensory profiles.

RESULTS

Satisfactory results were achieved in terms of identification reliability of unknown EVOOs, as well as false positive risk, thus confirming that the use of AMS combined with chemometrics is a powerful tool against fraudulent activities, without the need for mass accuracy data, which would increase the analysis cost.

CONCLUSION

A DART ionization source with a compact and reliable QDa MS analyser allowed for rapid fingerprinting analysis. Furthermore, MS spectra provided quali-quantitative information successfully related to EVOO differentiation. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Real-Time Sniffing Mass Spectrometry Aided by Venturi Self-Pumping Applicable to Gaseous and Solid Surface Analysis

Based on the Venturi self-pumping effect, real-time sniffing with mass spectrometry (R-sniffing MS) is developed as a tool for direct and real-time mass spectrometric analysis of both gaseous and solid samples. It is capable of dual-mode operation in either gaseous or solid phase, with the corresponding techniques termed as R_g-sniffing MS and R_s-sniffing MS, respectively. In its gaseous mode, R_g-sniffing MS is capable of analyzing a gaseous mixture with response time (0.8-2.1 s rise time and 7.3-9.6 s fall time), spatial resolution (<80 μm), three-dimensional diffusion imaging, and aroma distribution imaging of red pepper. In its solid mode, an appropriate solvent droplet desorbs the sample from a solid surface, followed by the aspiration of the mixture using the Venturi self-pumping effect into the mass spectrometer, wherein it is ionized by a standard ion source. Compared with the desorption electrospray ionization (DESI) technique, R_s-sniffing MS demonstrated considerably improved limit of detection (LOD) values for arginine (0.07 μg/cm² R_s-sniffing vs 1.47 μg/cm² DESI), thymopentin (0.10 μg/cm² vs 2.67 μg/cm²), and bacitracin (0.16 μg/cm² vs 2.28 μg/cm²). R_s-sniffing is applicable for the detection of C₆₀(OCH₃)₆Cl^-, an intermediate in the methoxylation reaction involving C₆₀Cl₆ (solid) and methanol (liquid). The convenient and highly sensitive R-sniffing MS has a characteristic separation of desorption from the ionization process, in which the matrix atmosphere of desorption can be interfaced by a pipe channel and self-pumped by the Venturi effect with consequent integration using a standard ion source. The R-sniffing MS operates in a voltage-, heat-, and vibration-free environment, wherein the analyte is ionized by a standard ion source. Consequently, a wide range of samples can be analyzed simultaneously by the R-sniffing MS technique, regardless of their physical state.

Rapid characterization of drugs in a single hair using thermal desorption ionization mass spectrometry

Hair remains the most common type of physical evidence found in most crime scenes. However, the amount of hair found at a crime scene is limited and analysis of drugs in hair by gas chromatography mass spectrometry (GC-MS) or liquid chromatography tandem mass spectrometry (LC-MS/MS) is laborious and time-consuming. In this study, a rapid and simple method is developed using thermal desorption ionization mass spectrometry (TDI-MS) to analyze drugs directly in a single hair. A single hair is put onto a heated metal ceramic heater (MCH) and then a high voltage direct current and solvent are applied to the single hair. The drugs in the hair are thermally desorbed and ionized, and subsequently transferred to the MS inlet and detected. A typical hair analysis can be completed in a few minutes. This novel technique provides a new orientation for forensic scientists to study drugs in a single hair that is found at a crime scene, on a suspect, or on a victim.

Rapid fingerprint analysis for herbal polysaccharides using direct analysis in real-time ionization mass spectrometry

RATIONALE

Herbal polysaccharides have various potential medicinal values. Development of reliable analytical method for the fingerprint analysis of polysaccharides is critical for their quality assessment, origin identification, and authenticity evaluation.

METHODS

Mechanochemical extraction (MCE) was used to extract polysaccharide components from different herbal species. Intact polysaccharides were then directly analyzed by direct analysis in real-time mass spectrometry (DART-MS). Standard addition method with isotope-labeled internal standard was used to quantify polysaccharide amounts directly from liquid extract. Multivariate data analysis was further conducted for species classification.

RESULTS

The intact and large polysaccharides were decomposed into small fragment ions less than m/z 350 instantaneously using DART ion source. Different polysaccharides showed distinguished fingerprint DART-MS spectra using both individual and mixed herbal species. The liquid supernatant from MCE was validated to be used as direct sample for DART-MS analysis. Quantitation was successfully achieved for polysaccharide contents in Dendrobium officinale from different locations.

CONCLUSIONS

A rapid fingerprint protocol in combination of MCE and DART-MS for herbal polysaccharides was developed. The whole process could be accomplished within a few minutes, from raw materials to final spectra, without requirements of pre-digestion and additional sample purification.

Minimizing transient microenvironment-associated variability for analysis of environmental anthropogenic contaminants via ambient ionization

The rapid and quantitative analysis of anthropogenic contaminants in environmental matrices is crucial for regulatory testing and to elucidate the environmental fate of these pollutants. Direct ambient mass spectrometry (AMS) methodologies greatly increase sample throughput, can be adapted for onsite analysis and are often regarded as semi-quantitative by most developed protocols. One of the limitations of AMS, especially for on site analysis applications, is the irreproducibility of the measurements related to the occurrence of transient microenvironments (TME) and variable background interferences. In this work we report an effective strategy to minimize these effects by hyphenating, for the first time, solid phase microextraction (SPME) arrow to mass spectrometry via a thermal desorption unit (TDU) and direct analysis in real time (DART) source. The developed method was optimized for the extraction and analysis of pesticides and pharmaceuticals from surface water. It was demonstrated that the hyphenation of the SPME and TDU-DART resulted in reduced background contamination, indicating the suitability of the method for onsite analysis even in variable and non-ideal environments. Model analytes were quantitated in the low μg/L range with a total analysis time of less than 5 min, linear dynamic ranges (LDR) and interday reproducibility for most compounds being 2.5-500 μg/L and lower than 10%, respectively. The developed approach provides an excellent analytical tool that can be applied for the onsite high-throughput analysis of water samples as well as air and aereosols. Considering the tunability of our extraction process, time-resolved environmental monitoring can be achieved onsite within minutes.

Applications of direct analysis in real time mass spectrometry in food analysis: A review

RATIONALE

Direct analysis in real time (DART) combined with mass spectrometry (MS) detection has become one of the most broadly used analytical approaches for the direct molecular characterization of food samples with regard to their chemical quality, safety, origin, and authentication. The major advantages of DART-MS for food analysis include high chemical sensitivity and specificity, high speed and throughput of analysis, simplicity, and the obviation of tedious sample preparation and solvents.

METHODS

The recent applications of DART coupled with different mass analyzers, including quadrupole, ion trap, Orbitrap, and time of flight, are discussed. In addition, sample pretreatment methods that have been coupled with DART-MS are discussed.

RESULTS

We summarize the applications of DART-MS in food science and industry published in the period from 2005 to this date. The applications and analytical characteristics are systematically categorized across the three major types of foods: solid foods, liquid foods, and viscous foods.

CONCLUSIONS

DART-MS has proved its high suitability for the direct, rapid, and high-throughput molecular analysis of very different food samples with minimal or no sample preparation, thus offering a high-speed alternative to liquid chromatography/mass spectrometry (LC/MS) and gas chromatography/mass spectrometry (GC/MS) approaches that are traditionally employed in food analysis.

Direct coupling of paper spray mass spectrometry and four-phase electroextraction sample preparation

This paper presents a novel coupling between a four-phase electroextraction (EE) system and paper spray mass spectrometry (PS-MS) for the extraction, pre-concentration, and direct analysis of target compounds in different samples. The approach, EE-PS-MS, is based on the sorption of analytes directly on the tip of a triangular-shaped chromatographic paper, with subsequent prompt analysis by PS-MS. Thus, no off-line extraction step is required before the PS analysis, improving the protocol efficiency and reducing the analysis time. In addition to functioning as a porous material to absorb the target compounds, the chromatographic paper also served as the support for one of the aqueous phases of the optimized four-phase electroextraction system. Extraction conditions, such as the composition of the donor and organic phases, applied electric potential, and extraction time, were optimized. Three different applications, involving biofluid, food, and water quality analysis, were evaluated as a proof-of-concept. These applications involved the determination of (i) cocaine and lidocaine in saliva, (ii) malachite green in tap water, and (iii) bisphenol A (BPA) in red wine. When compared with direct PS-MS, the novel EE-PS-MS protocol improved the sensitivities by factors ranging from 14 to 110, depending on the analyte and the sample. The electroextraction procedures were performed on a laboratory-built 66-well plate, which offered the functionality of simultaneous sample handling and, most importantly, improved analytical throughput.

Synchronous Construction of Hierarchical Porosity and Thiol Functionalization in COFs for Selective Extraction of Cationic Dyes in Water Samples

Pore size and functionalization are two critical factors for covalent organic frameworks (COFs) as effective adsorbents. However, due to the low crystallinity of COFs, it is a grand challenge to accomplish pore diameter adjustment and functionalization at the same time. In this work, we developed a simple and ingenious strategy, cutting off linkage, to synchronously construct hierarchical porosity and modify thiol groups in COFs under mild conditions. The hybrid COFs containing disulfide bonds were designed and synthesized, and then the disulfide bonds were cleaved by glutathione, resulting in the formation of thiol groups as well as the increase in pore size caused by skeleton defects. The pore diameter of thiol-functionalized hierarchical porous COFs (denoted as HP-TpEDA-SH) was concentrated at 2.6 and 3.5 nm. Thanks to the electrostatic attraction of thiol groups to cationic dyes and the higher number of available adsorption sites, the maximum extraction amounts of methylene blue (MB), malachite green (MG), and crystal violet (CV) by HP-TpEDA-SH were 2.6, 2.1, and 3.3 times those of microporous COFs under optimal extraction conditions, respectively. The proposed analytical method (solid-phase extraction-high-performance liquid chromatography/ultraviolet (SPE-HPLC/UV)) with HP-TpEDA-SH as the adsorbent showed low detection limits of 1.3, 0.13, and 0.12 μg·L^-1 for MB, MG, and CV, respectively. The recoveries of three spiked water samples ranged from 81.5 to 113.8%, with relative standard deviations (RSDs) less than 9.7%. This work not only opened a new avenue for the preparation of functionalized hierarchical porous COFs but also established an effective method for detecting trace cationic dyes in fishery water.

Microfluidic Chip-Based Induced Phase Separation Extraction as a Fast and Efficient Miniaturized Sample Preparation Method

Induced phase separation extraction (IPSE) is an efficient sample clean-up technique that can replace liquid-liquid extraction (LLE). The purpose of this study was to miniaturize IPSE by carrying it out in a microfluidic chip. An IPSE chip was designed and evaluated for its ability to separate and purify samples on a microscale. The 5 × 2 cm chip was fed with a solution of polar to non-polar model compounds in acetonitrile-water (1:1). In the 100 µm wide and 40 µm deep microchannels, the sample solution was efficiently separated into two immiscible phases by adding a hydrophobic solvent as inducer. Analytes present in the sample solution each migrated to their own favorable phase upon phase separation. After optimization, extraction and fractionation were easily and efficiently achieved. The behavior of analytes with a pH-dependent partitioning could be influenced by adjusting the pH of the sample solution. Scutellaria baicalensis extract, used in Traditional Chinese Medicine (TCM), was successfully separated in aglycones and glycosides. In this microscale system, the sample and solvent consumption is reduced to microliters, while the time needed for the sample pretreatment is less than one minute. Additionally, the extraction efficiency can reach up to 98.8%, and emulsion formation is avoided.

Quantification of artificial sweeteners in alcoholic drinks using direct analysis in real-time QTRAP mass spectrometry

Artificial sweeteners have been widely used as replacements for sugars in foods. Rapid determination of artificial sweeteners contained in various foods are highly desirable for the routine analysis. Here, we report a robust approach based on direct analysis in real time coupled with QTRAP mass spectrometry to screen and quantitate simultaneously seven artificial sweeteners, including aspartame, saccharin, acesulfame-K, neotame, sucralose, cyclamate and alitame in alcoholic drinks. The detection method merely involved a simple sample pretreatment process, with a good linearity, low limit of quantification, satisfied recovery and relative standard deviation for each target compound. More importantly, the approach is highly sensitive and accurate in monitoring the seven artificial sweeteners in whisky, Chinese liquors, beer and wines obtained from the supermarket. The results demonstrated that the approach described here could be suitable for large-scale application in routine quality control analysis of artificial sweeteners.

Development of Ultra-Performance Liquid Chromatography-Mass Spectrometry Method for Simultaneous Determination of Three Cationic Dyes in Environmental Samples

Lower dye concentrations and the presence of several dyes along with other matrices in environmental samples restrict their determination. Herein, a highly sensitive and rapid ultra-performance tandem mass spectrometric method was developed for simultaneous determination of cationic dyes, namely methylene blue (MB), rhodamine B (RB) and crystal violet (CV), in environmental samples. To preconcentrate environmental samples, solid-phase extraction cartridges were developed by using hydrogen peroxide modified pistachio shell biomass (MPSB). The surface morphological and chemical functionalities of MPSB were well characterized. The developed method was validated considering different validation parameters. In terms of accuracy and precision, the %RSD for all three dyes at all four concentration points was found to be between 1.26 and 2.76, while the accuracy reported in terms of the recovery was found to be 98.02%-101.70%. The recovery was found to be in the range of 98.11% to 99.55%. The real sample analysis shows that MB, RB, and CV were found in the ranges of 0.39-5.56, 0.32-1.92 and 0.27-4.36 μg/mL, respectively.

Rapid determination of chemical composition in the particulate matter of cigarette mainstream smoke

Particulate matter from mainstream smoke (MSS) is significantly hazardous when inhaled into the human body. An ambient ionization mass spectrometric method, direct analysis in real time mass spectrometry (DART-MS), was applied to rapidly and simultaneously measure multiple particulate components in MSS. A variety of compounds were obtained in seconds, where different types of cigarettes and different solvent extracts generated distinct chemical constituents as validated by principle component analysis. Chemical formula assignment and compound identification were based on accurate m/z values with mass errors <10 ppm. Quantitation of nicotine was achieved using an isotope internal standard with DART-MS. Method validation with chromatographic-MS analysis further proved the advantages of DART-MS with respect to analysis speed and operational simplicity for the direct evaluation of complex samples. DART-MS is feasible for the rapid acquisition of cigarette fingerprints for quality control as well as for quantitative assessment of carcinogens for harm reduction.

Direct analysis in real time coupled with quadrupole-Orbitrap high-resolution mass spectrometry for rapid analysis of pyrethroid preservatives in wooden food contact materials

A methodology is presented for the determination of four pyrethroid (PYR) preservatives in wooden food contact materials (FCMs) using direct analysis in real time (DART) coupled with quadrupole-Orbitrap high-resolution mass spectrometry (Q-Orbitrap HRMS). The sampling mode and critical parameters of the DART-Q-Orbitrap HRMS protocol were systematically investigated. Good linearity was achieved for the four analytes with correlation coefficients all greater than 0.99. The limits of detection (LODs) and limits of quantitation (LOQs) of the method were in the range of 0.04-0.20 mg kg^-1 and 0.10-0.50 mg kg^-1, respectively. The mean recoveries ranged from 72.1% to 82.7% with relative standard deviations (RSDs) from 5.2% to 11.8% at three spiked levels. The developed method was proved to be suitable for rapid screening of PYRs in complex wooden FCM samples to ensure product safety and consumer health.

Colorimetric and fluorescent sensing of rhodamine using polymethacrylate matrix

This is a description of the tracer analysis method involving colorimetric and fluorescent measurements based on solid phase extraction of rhodamine into transparent polymethacrylate matrix. Concentration of rhodamine in PMM is measured as spectrophotometric absorption level at 535 nm and fluorescence at 554 nm. The calibration graphs are linear within the ranges 0.02-0.10 mg∙L^-1 and 0.002-0.06 mg∙L^-1 and detection limits 0.014 mg∙L^-1 and 0.0005 mg∙L^-1 are calculated for colorimetric and fluorescent measurements, respectively. The method has been successfully used for determination of rhodamine in groundwater.