On-fiber Derivatization Research Articles

Automated method using direct-immersion solid-phase microextraction and on-fiber derivatization coupled with comprehensive two-dimensional gas chromatography high-resolution mass spectrometry for profiling naphthenic acids in produced water

Naphthenic acids (NAs) are naturally occurring organic acids in petroleum and are found in waste waters generated during oil production (produced water, PW). Profiling this class of compounds is important due to flow assurance during oil exploration. Compositional analysis of PW is also relevant for waste treatment to reduce negative impacts on the environment. Here, comprehensive two-dimensional gas chromatography coupled with high-resolution mass spectrometry (GC×GC–HRMS) was applied as an ideal platform for qualitative analysis of NAs by combining the high peak capacity of the composite system with automated scripts for group-type identification based on accurate mass measurements and fragmentation patterns. To achieve high-throughput profiling of NAs in PW samples, direct-immersion solid phase microextraction (DI-SPME) was selected for extraction, derivatization and preconcentration. A fully automated DI-SPME method was developed to combine extraction, fiber rinsing and drying, and on-fiber derivatization with N-methyl-N‑tert-butyldimethylsilyltrifluoroacetamide (MTBSTFA). Data processing was based on filtering scripts using the Computer Language for Identifying Chemicals (CLIC). The method successfully identified up to 94 NAs comprising carbon numbers between 6 and 18 and hydrogen deficiency values ranging from 0 to -4. The proposed method demonstrated wider extraction coverage compared to traditional liquid-liquid extraction (LLE) – a critical factor for petroleomic investigations. The method developed also enabled quantitative analysis, exhibiting detection limits of 0.5 ng L−1 and relative standard deviation (RSD) at a concentration of NAs of 30 µg L−1 ranging from 4.5 to 25.0%.

FORMALDEHYDE ANALYSIS BY SPME ON-FIBER DERIVATIZATION: A STUDY OF THE KINETIC MODELS OF ADSORPTION FOR DIVINYLBENZENE

Solid-phase microextraction (SPME) via on-fiber derivatization with O-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine (PFBHA) and gas chromatographic determination is considered a technique of choice in many analytical fields for formaldehyde (FA) monitoring. Vapor phase adsorption models of experimentally loaded PFBHA on porous divinylbenzene (DVB) SPME were investigated at 60 °C, 35 cm s-1 of air velocity, in a 1-64 min range: with the fiber completely exposed, loaded PFBHA was about 276 µg. Among the models tested, i.e. heat transfer, pseudo-second-order (PSO), Elovich, intra-particle diffusion, extra-particle diffusion and Langmuir, PFBHA adsorption was best fit by the PSO model, showing agreement with experimental data (272 µg). The sampling rate of FA in our conditions, obtained with a permeation tube system, was in agreement with literature (17.4 and 18.3 mL min-1, respectively). Thus, an overall standardization of the sampling phase is presented, leaving the sampling time as the most crucial parameter to be set for future applications.

Automated method for short-chain aldehydes emission measurement by dynamic solid-phase microextraction on-fiber derivatization GC-MSD coupled with a flow-cell

A novel automated method was developed to test short-chain aldehyde emissions using a chamber and a flow-cell coupled with a dynamic solid-phase microextraction (SPME) on-fiber derivatization technique. Calibration curves of short-chain aldehydes were developed for quantitation of target analytes, including formaldehyde, acetaldehyde, propionaldehyde, and acrolein emitted from the chamber outlet. The linearity range for the aldehydes was 0.8 to 2130.0 µg/m3. The limits of quantitation (LOQ) for various aldehydes ranged from ∼0.2 – 1.9 µg/m3. By using this method, emission rate curves are measured with an automated system. Compared with a traditional 2,4-dinitrophenyl hydrazine (DNPH)-high performance liquid chromatography (HPLC) method for aldehyde emission measurement, this method provided an automated technique to study the emission of short-chain aldehydes from multiple samples in one experiment. Furthermore, by using dynamic SPME coupled to an on-fiber derivatization technique, the repeatability and sensitivity of the method is comparable and even better than traditional techniques.

INNOVATIVE GAS CHROMATOGRAPHIC DETERMINATION OF FORMALDEHYDE BY MINIATURIZED EXTRACTION AND ON-FIBER DERIVATIZATION, VIA SPME AND SPME ARROW

Formaldehyde (FA) is a carbonyl compound, ubiquitous in the environment and among the most widespread pollutants: it has exhibited toxic properties and is classified as a human carcinogen. FA is released from several sources, both temporary (e.g., combustion processes) and permanent (e.g., building products). This work proposes an innovative fully-automated application of headspace solid-phase microextraction (SPME) with on-fiber derivatization for the analysis of airborne FA emitted from liquid solutions or solid manufacts, in static mode, via gas chromatography-mass spectrometry. The method was tested in a wide range of airborne FA concentrations, using SPME and SPME Arrow fibers: the inter-day LOD and LOQ for SPME and SPME Arrow were evaluated, resulting in 0.072 and 0.215 ppm and 0.014 and 0.042 ppm, respectively. Moreover, other conventional detectors, such as Electron Capture Detector (ECD), Thermoionic Specific Detector (TSD), Photoionization Detector (PID), and Flame Ionization Detector (FID), were tested to set an analytical method to meet different requirements. The sensitivity and linearity of PID, FID and MS were comparable, while TSD and ECD were not suitable for the developed method, due to issues of response or linearity. MS results to be the most suitable and perfoming detector, however PID and FID result to be cheaper valid alternatives.

Headspace solid-phase microextraction and on-fiber derivatization for the determination of 3-/2-MCPDE and GE in breast milk and infant formula by gas chromatography tandem mass spectrometry

The presence of fatty acid esters of 3-monochloropropane-1,2-diol (3-MCPDE), 2-monochloropropane-1,3-diol (2-MCPDE) and glycidyl (GE) in foods is a potential concern due to their toxicity, especially for infants. This study proposed a rapid, sensitive and environmentally friendly method for simultaneous determination of the 3-/2-MCPDE and GE in breast milk and infant formula using headspace solid-phase microextraction (SPME) and on-fiber derivatization combined with gas chromatography-tandem mass spectrometry (GC-MS/MS). The approach proved high sensitivity with detection limits of 0.10 μg/L and 0.15 μg/kg for MCPDEs in breast milk and infant formula, respectively. Mean recoveries were obtained ranging from 79.9 to 111.2% for breast milk and from 82.1 to 106.7% for infant formula, with relative standard deviation (RSD) of less than 9.5%. According to the levels of 3-MCPDE and GE determined in 30 breast milk and 23 infant formulas, the exposure to 3-MCPDE and GE may pose a potential health risk for infants from birth to <12 months fed by breast milk and infants from birth to 6 months fed by infant formula.

Headspace analysis of ammonium nitrate variants and the effects of differing vapor profiles on canine detection

Canines continue to be one of the most frequently deployed tool in the detection of explosives, and particularly homemade explosives (HMEs), in part, due to the ease in training to new HME materials as threats arise. The majority of HMEs encountered contain ammonium nitrate (AN), and previous research has measured the release of ammonia from AN, and found that the ammonia vapor concentration varies with form, purity, and environment, but this is has not been correlated to canine detection proficiency. In this research, the headspace analysis of AN variants was carried out using solid phase microextraction (SPME) with gas chromatography/mass spectrometry (GC/MS). Ammonia vapor from the AN was extracted using on-fiber derivatization, while the presence of other volatiles in the headspace of these variants were also characterized by a traditional SPME extraction. These results were correlated to canine testing, where canines previously trained in odor detection were provided laboratory-grade AN for odor imprinting, after which they were to locate other AN variants in a series of simple detection tasks. Headspace analysis showed variations in both the amount of ammonia as well as other volatile compounds in the headspace of the various AN samples, as well as changes in the vapor profiles due to changing environmental conditions. Canine data indicated that the differences in the headspace profiles of the samples may confound detection when canines were trained on laboratory-grade AN alone, while increased ammonia vapor availability from certain samples may have improved detection by this group of canines.

Gas Chromatography-Mass Spectrometry Paired with Total Vaporization Solid-Phase Microextraction as a Forensic Tool.

Gas Chromatography - Mass Spectrometry (GC-MS) is a frequently used technique for the analysis of numerous analytes of forensic interest, including controlled substances, ignitable liquids, and explosives. GC-MS can be coupled with Solid-Phase Microextraction (SPME), in which a fiber with a sorptive coating is placed into the headspace above a sample or immersed in a liquid sample. Analytes are sorbed onto the fiber which is then placed inside the heated GC inlet for desorption. Total Vaporization Solid-Phase Microextraction (TV-SPME) utilizes the same technique as immersion SPME but immerses the fiber into a completely vaporized sample extract. This complete vaporization results in a partition between only the vapor phase and the SPME fiber without interference from a liquid phase or any insoluble materials. Depending upon the boiling point of the solvent used, TV-SPME allows for large sample volumes (e.g., up to hundreds of microliters). On-fiber derivatization may also be performed using TV-SPME. TV-SPME has been used to analyze drugs and their metabolites in hair, urine, and saliva. This simple technique has also been applied to street drugs, lipids, fuel samples, post-blast explosive residues, and pollutants in water. This paper highlights the use of TV-SPME to identify illegal adulterants in very small samples (microliter quantities) of alcoholic beverages. Both gamma-hydroxybutyrate (GHB) and gamma-butyrolactone (GBL) were identified at levels that would be found in spiked drinks. Derivatization by a trimethylsilyl agent allowed for conversion of the aqueous matrix and GHB into their TMS derivatives. Overall, TV-SPME is quick, easy, and requires no sample preparation aside from placing the sample into a headspace vial.

SPME-GC–MS for the off-gassing analysis of a complex museum object

The identification of volatile organic compounds (VOCs) emitted by a complex museum object, composed of materials of different nature, has been optimized by solid-phase microextraction coupled to gas chromatography-mass spectrometry (SPME-GC–MS). The performance of two fiber coatings and four sampling times were tested and compared in order to define the best sampling conditions. The method allowed a fair extraction of volatile and semivolatile compounds emitted naturally by the object, without any type of accelerating aging. In addition, on-fiber derivatization was applied to improve the extraction efficiency and reduce the sampling time of harmful carboxylic acids emitted by the object. The results obtained are of prime importance to show the off-gassing activity of a valuable museum object in order to take further decisions related with its storage and display conditions.

Detection of ɣ-hydroxybutyric acid (GHB) and ɣ-butyrolactone (GBL) in alcoholic beverages via total vaporization solid-phase microextraction (TV-SPME) and gas chromatography-mass spectrometry.

Total Vaporization Solid-Phase Microextraction (TV-SPME) relies on the same technique as standard SPME but completely vaporizes a sample extract, and analytes are sorbed directly from the vapor phase. On-fiber derivatization may also be performed using TV-SPME, where the fiber is first exposed to the headspace of a vial containing the derivatization agent, then exposed to a new vial containing the sample. ɣ-Hydroxybutyric acid (GHB) and ɣ-butyrolactone (GBL) are drugs of concern in that they may be used in drug facilitated sexual assault by surreptitiously spiking them into a victim's beverage. These drugs cause sedation, memory loss, and are difficult to detect in biological samples. One challenge in their analysis is that they can interconvert in aqueous samples, which was demonstrated in samples allowed to stand at room temperature for long periods. A volume study of GBL in water was performed with volumes ranging from 1 to 10,000µl to compare the efficacy of TV-SPME, headspace SPME, and immersion SPME. Lastly, water, beer, wine, liquor, and mixed drinks were spiked with either GHB or GBL with realistic concentrations (mg/ml) and microliter quantities were analyzed using a TV-SPME Gas Chromatography-Mass Spectrometry method. The GBL volume study demonstrated an increased sensitivity in GBL detection when TV-SPME was utilized. Additionally, GHB and GBL were identified in various beverages at realistic concentrations. Overall, TV-SPME is beneficial because it requires no sample preparation and uses smaller sample volumes than immersion and headspace SPME.

Automated Derivatization and Identification of Controlled Substances in Solution Via Total-Vaporization Solid-Phase Microextraction (TV-SPME)

Total-vaporization solid-phase microextraction (TV-SPME) with on-fiber derivatization can simplify sample preparation for a variety of analytes compared to traditional methods for gas chromatography-mass spectrometry (GC-MS) analysis. Microgram quantities of drugs such as amphetamine, ephedrine, methamphetamine, 2C-I, 25I-NBOMe, 25I-NBOH, and gamma-hydroxybutyric acid (GHB) were analyzed in solution using TV-SPME. Derivatization can allow for analytes that cannot normally be detected by GC-MS to be identified and can improve chromatographic performance and sensitivity. TV-SPME also simplifies the process of derivatization by allowing it to take place on the fiber, which can be automated using a robotic autosampler. This technique also displays great versatility in decreasing sample preparation for a variety of sample matrices.

Analysis of Selected Staling Aldehydes in Wort and Beer by GC-EI-MS/MS Using HS-SPME with On-Fiber Derivatization

Quantification of staling aldehydes from wort and beer requires sensitive instrumental analysis. In the brewing industry, this is for the most part accomplished by gas chromatography-mass spectrometry (GC-MS) using headspace solid-phase microextraction (HS-SPME) and on-fiber derivatization (OFD) with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA). With respect to lipid oxidation products (e.g., (E)-2-nonenal) and minor Strecker aldehydes (e.g., methional), the sensitivity of GC-EI-MS might not be sufficient to ensure reliable quantification and long-term stability regarding method performance. To overcome these problems, an elaborate gas chromatography-electron impact-tandem mass spectrometry (GC-EI-MS/MS) methodology was implemented. GC-EI-MS/MS improved sensitivity and reduced matrix effects resulting from overlapping PFBHA-oximes (PFBOs). It enabled reliable quantification of 15 selected aldehydes in different matrices (wort, beer) across a wide concentration range (0.01 − 1000 µg/L). Extensive method validation and long-term stability testing proved excellent method performance. Lastly, direct comparison of GC-EI-MS/MS and GC-EI-MS revealed that the quantification of low abundant aldehydes via GC-EI-MS/MS is more reproducible and that lower limits of quantification were achieved.

Graphene Oxide-Ionic Liquid Used As Solid-Phase Microextraction Coating For Polyphenolic Compounds' Extraction And Determination With GC-MS After On-Fiber Derivatization In Wine

We describe the use of a home-made fiber coated by graphene oxide modified by an ionic liquid having methylimidazolium cation with an amino-functional group for the extraction of polyphenolic compounds (P.C.s). We then performed the determination by gas chromatography coupled with mass spectrometry after on-fiber derivatization. The authors optimized the main parameters influencing the extraction and derivatization processes. The on-fiber derivatization was employed within 15 min at 60 ºC using 20 µL of trimethylsilyl reagents. Under the optimized conditions, the calibration curves for 12 P.C.s were linear from 0.1 to 1000 µg/L, and the detection limits were between 0.02 and 0.1 µg/L. We determined the single fiber repeatability obtained for all calibration points and the fiber to fiber reproducibility for 100 µg/L to be &amp;lt; 14.82% and &amp;lt; 5.87%, respectively. The extraction efficacy of the home-made fiber due to high intermolecular and electrostatic attractions was much better than the commercial fibers. We successfully applied the method to the analysis of P.C.s in wine samples with the recoveries from 72.8 to 99.9%.

Sample pre-treatment and analytical methodology for the simultaneous determination of pharmaceuticals and personal care products in sewage sludge

This work describes the design, optimization and validation of an analytical method for the simultaneous determination of 14 pharmaceuticals and personal care products (PPCPs) in sewage sludge. A thorough optimization of the sample pre-treatment was carried out. As a result, microwave-assisted extraction (MAE) was combined with an in-situ clean-up stage and a filtration step. A combination of MilliQ® water/MeOH 95:5 (v/v) adjusted to pH 9 turned out to be the optimal solvent mixture for extraction. The instrumental part of the method presents a significant novelty based on a fully automated sample preparation for the analysis of PPCPs. It consisted of a direct immersion solid phase microextraction followed by on-fiber derivatization, online coupled to gas chromatography - mass spectrometry (DI-SPME-On-fiber derivatization - GC-MS). An isotope dilution approach was used for quantifying, which conferred high reliability to the method. This methodology was validated for 10 compounds with good analytical performance, limit of detection below 20 ng g−1 and absolute recovery in the range of 30–70% for most of the compounds. It supposes an ecological analytical alternative for many routine analysis laboratories around the world. The developed method was applied to different real samples generated in both a pilot-scale thermal hydrolysis treatment plant and an anaerobic digester operated in mesophilic conditions. Salicylic acid and naproxen were found at concentrations above 1000 ng g−1.

Headspace analysis of potassium chlorate using on-fiber SPME derivatization coupled with GC/MS

Potassium chlorate is a powerful oxidizer salt that, when mixed with a fuel source, has been used as a homemade explosive (HME). As an inorganic salt, potassium chlorate has no appreciable vapor pressure under ambient conditions and requires temperatures exceeding 300 °C for decomposition. However, detection of potassium chlorate by trained canines has been demonstrated, implying that it exudes a vapor signature with one or more volatile compounds, although no such species have been confirmed to date. In this work, solid-phase microextraction with a novel on-fiber derivatization reaction was used to interrogate the headspace of several potassium chlorate samples of varying purity, as well as that of related chlorinated salts and explosive mixtures. This analysis showed the presence of few volatile species in the headspace of potassium chlorate other than vaporous chlorine, detected as the derivatized product, chloro-2-propanol. Relative amounts of chloro-2-propanol could be compared between potassium chlorate variants, and could be detected in the presence of other volatile species associated with the fuels.

Solid-phase microextraction and on-fiber derivatization for assessment of mammalian and vegetable milks with emphasis on the content of major phytoestrogens

A new solvent-free method for the simultaneous determination of some major phytoestrogens (equol, enterodiol, daidzein, genistein, glycitein) in different commercial milks (cow, goat and soy-rice) was developed. After solid phase microextraction, performed by direct immersion of a 65 μm-polydimethylsiloxane–divinylbenzene fiber in diluted (1:100 with 0.2% formic acid - 30% sodium chloride) milk samples (18 °C for 20 min under stirring), a direct on-fiber silylation with N,O-bis (trimethylsilyl)trifluoroacetamide) containing 1% trimethylchlorosilane (70 °C for 20 min) was performed prior to gas chromatography–mass spectrometry analysis. Since the target compounds were determined as aglycones, the hydrolytic removal of the aglycone from the glycosides was performed. The method permitted the determination of the target analytes in all the considered milk samples as well as the detection of some major amphipathic fats indicating that the approach could potentially be applied in the future for further applications, such as milk profiling.

Fast on-fiber derivatization and GC/MS analysis of phytohormones in wheat based on pencil-type coated carbon fibers

New coated carbon fibers (CCFs) have been synthesized, characterized and used as solid phase microextraction (SPME) matrix for the analysis of phytohormones (jasmonic acid, indole-3-acetic acid, and abscisic acid) in wheat samples. The SPME device, realized inserting CCFs in a pencil-type device, when coupled with gas chromatography-mass spectrometry, provides in few steps high recovery values (79–112%), fast on-fiber derivatization (30 s), good method reproducibility (RSD < 20%), low detection limits (0.5–2.1 ng g−1). The pencil-type CCFs-SPME device was successfully employed for the determination of phytohormone in wheat samples, allowing simple and quick extraction/derivatization/injection processes. The proposed device can be then considered as a promising and functional tool for fast and reliable extraction and preconcentration of analytes from real samples, allowing a simple derivatization procedure and direct injection in the chromatographic instrumentation.

High-Throughput Analysis of Selected Urinary Hydroxy Polycyclic Aromatic Hydrocarbons by an Innovative Automated Solid-Phase Microextraction.

High-throughput screening of samples is the strategy of choice to detect occupational exposure biomarkers, yet it requires a user-friendly apparatus that gives relatively prompt results while ensuring high degrees of selectivity, precision, accuracy and automation, particularly in the preparation process. Miniaturization has attracted much attention in analytical chemistry and has driven solvent and sample savings as easier automation, the latter thanks to the introduction on the market of the three axis autosampler. In light of the above, this contribution describes a novel user-friendly solid-phase microextraction (SPME) off- and on-line platform coupled with gas chromatography and triple quadrupole-mass spectrometry to determine urinary metabolites of polycyclic aromatic hydrocarbons 1- and 2-hydroxy-naphthalene, 9-hydroxy-phenanthrene, 1-hydroxy-pyrene, 3- and 9-hydroxy-benzoantracene, and 3-hydroxy-benzo[a]pyrene. In this new procedure, chromatography’s sensitivity is combined with the user-friendliness of N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide on-fiber SPME derivatization using direct immersion sampling; moreover, specific isotope-labelled internal standards provide quantitative accuracy. The detection limits for the seven OH-PAHs ranged from 0.25 to 4.52 ng/L. Intra-(from 2.5 to 3.0%) and inter-session (from 2.4 to 3.9%) repeatability was also evaluated. This method serves to identify suitable risk-control strategies for occupational hygiene conservation programs.

An Integrated Air Monitoring Approach for Assessment of Formaldehyde in the Workplace.

The aim of this study is to validate an integrated air monitoring approach for assessing airborne formaldehyde (FA) in the workplace. An active sampling by silica gel impregnated with 2,4-dinitrophenylhydrazine, a passive solid phase microextraction technique using O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine as on-fiber derivatization reagent, an electrochemical direct-reading monitor, and an enzyme-based badge were evaluated and tested over a range of 0.020–5.12 ppm, using dynamically generated FA air concentrations. Simple linear regression analysis showed the four methods were suitable for evaluating airborne FA. Personal and area samplings in 12 anatomy pathology departments showed that the international occupational exposure limits in the GESTIS database were frequently exceeded. This monitoring approach would allow a fast, easy-to-use, and economical evaluation of both current work practices and eventual changes made to reduce FA vapor concentrations.

Multiresidue analytical method for pharmaceuticals and personal care products in sewage and sewage sludge by online direct immersion SPME on-fiber derivatization – GCMS

The work here presented aimed at developing an analytical method for the simultaneous determination of 22 pharmaceuticals and personal care products, including 3 transformation products, in sewage and sludge. A meticulous method optimization, involving an experimental design, was carried out. The developed method was fully automated and consisted of the online extraction of 17 mL of water sample by Direct Immersion Solid Phase MicroExtraction followed by On-fiber Derivatization coupled to Gas Chromatography – Mass Spectrometry (DI-SPME – On-fiber Derivatization – GC – MS). This methodology was validated for 12 of the initial compounds as a reliable (relative recoveries above 90% for sewage and 70% for sludge; repeatability as %RSD below 10% in all cases), sensitive (LODs below 20 ng L−1 in sewage and 10 ng g−1 in sludge), versatile (sewage and sewage-sludge samples up to 15,000 ng L−1 and 900 ng g−1, respectively) and green analytical alternative for many medium-tech routine laboratories around the world to keep up with both current and forecast environmental regulations requirements. The remaining 10 analytes initially considered showed insufficient suitability to be included in the final method. The methodology was successfully applied to real samples generated in a pilot scale sewage treatment reactor.

Assessment of occupational exposure to gaseous peracetic acid.

In order to assess short-term exposure to peracetic acid (PAA) in disinfection processes, the Authors compared 4 industrial hygiene monitoring methods to evaluate their proficiency in measuring airborne PAA concentrations. An active sampling by basic silica gel impregnated with methyl p-tolyl sulfoxide (MTSO), a passive solid phase micro-extraction technique using methyl p-tolyl sulfide (MTS) as on-fiber derivatization reagent, an electrochemical direct-reading PAA monitor, and a novel visual test strip PAA detector doped with 2,2'-azino-bis (3-ethylbenzothiazoline)-6-sulfonate were evaluated and tested over the range of 0.06-16 mg/m3, using dynamically generated PAA air concentrations. The linear regression analysis of linearity and accuracy showed that the 4 methods were suitable for PAA monitoring. Peracetic acid monitoring in several use applications showed that the PAA concentration (1.8 mg/m3) was immediately dangerous to life or health as proposed by the National Institute of Occupational Safety and Health, and was frequently exceeded in wastewater treatment (up to 7.33 mg/m3), and sometimes during food and beverage processes and hospital high-level disinfection operations (up to 6.8 mg/m3). The methods were suitable for the quick assessment of acute exposure in PAA environmental monitoring and can assist in improving safety and air quality in the workplace where this disinfectant is used. These monitoring methods allowed the evaluation of changes to work out practices to reduce PAA vapor concentrations during the operations when workers are potentially overexposed to this strong antioxidant agent. Int J Occup Med Environ Health 2018;31(4):527-535.