Metabolomics of natural samples: A tutorial review on the latest technologies

Metabolomics is the study of metabolites present in a living system. It is a rapidly growing field aimed at discovering novel compounds, studying biological processes, diagnosing diseases, and ensuring the quality of food products. Recently, the analysis of natural samples has become important to explore novel bioactive compounds and to study how environment and genetics affect living systems. Various metabolomics techniques, databases, and data analysis tools are available for natural sample metabolomics. However, choosing the right method can be a daunting exercise because natural samples are heterogeneous and require untargeted approaches. This tutorial review aims to compile the latest technologies to guide an early-career scientist on natural sample metabolomics. First, different extraction methods and their pros and cons are reviewed. Second, currently available metabolomics databases and data analysis tools are summarized. Next, recent research on metabolomics of milk, honey, and microbial samples is reviewed. Finally, after reviewing the latest trends in technologies, a checklist is presented to guide an early-career researcher on how to design a metabolomics project. In conclusion, this review is a comprehensive resource for a researcher planning to conduct their first metabolomics analysis. It is also useful for experienced researchers to update themselves on the latest trends in metabolomics.

Coral-like, self-assembled, and spatially bounded Ag nano-particles on franzinite zeolite composite sensor toward accurate, synergetic, and ultra-trace sulfadiazine detection

A coral-like Ag@FRA zeolite nanocomposite sensor reveals high sensitivity toward sulfadiazine (SDZ) in a dual detection of fluorescence and electrochemistry. The sensor has been as-synthesized in the hydrothermal condition through a one-pot self-assembly process in which the high crystalline Ag nanoparticles (NPs) are closely arranged and stacked on the nanosized surface cage window of the FRA (Franzinite) zeolite. Strong ultrasound can drive the coral-like composite release Ag nanoparticles whose distribution range mainly from 10 to 12 nm lead to the purple fluorescence in an emission spectrum. In sea water, the fluorescence increases linearly in the SDZ concentration range of 5 × 10-18-5 × 10-10 M. Furthermore, the LOD (limit of detection) reaches 1.4 × 10-22 M by the spatial confinement effect of the coral-liked FRA cage structure in CV (cyclic voltammetry) method at the characteristic potential peak position of 0.1 V vs. SCE. The theoretical calculation also confirms that the FRA cage structure matches well with the SDZ molecules. Further studies indicate the generation of a novel stable composite sensor with high specificity, good recovery and repeatability, which depends on the induction of silver ions upon the artificial synthesis of FRA.

Validation of a Modified QuEChERS Method for the Determination of Selected Organochlorine Compounds in Honey

Honey is considered to be a health-promoting food product. Therefore, it is assumed that it should be free of contaminants. Although the use of organochlorine pesticides (OCPs) was banned a few decades ago in developed countries, persistent organic pollutants (POPs) are still detected in various environmental and biological matrices, including food. These contaminants exhibit toxic properties and bioaccumulate in some food chains. The validation of a modified QuEChERS extraction method was successfully performed for o,p'-DDT, o,p'-DDE, o,p'-DDD, p,p'-DDT, p,p'-DDE, p,p'-DDD, heptachlor and dieldrin. 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153) was used as an internal standard. The modification involved changing the solvent from acetonitrile to n-hexane after extraction. Quantitation was carried out using gas chromatography with an electron capture detector (µECD). The mean recovery values for o,p'-DDT, o,p'-DDE, o,p'-DDD, p,p'-DDT, p,p'-DDE, p,p'-DDD and dieldrin, spiked at 2.9 ng/g and 20 ng/g, ranged from 64.7% to 129.3%, and, for heptachlor spiked at 5.6 ng/g and 20 ng/g, ranged from 68.0% to 88.3%. The relative standard deviation (RSD) for these concentrations did not exceed 20%, and the within-laboratory reproducibility was below 20%, except o,p'-DDE and p,p'-DDT, which were 25.2% and 20.7%, respectively. This modified QuEChERS extraction method for selected organochlorine compounds was demonstrated as effective for routine testing in honey.

Simple and rapid method for 336 multiresidual pesticide analysis in saliva, determination of their chemical stabilities, and biomonitoring of farmers

Simultaneous multiresidual pesticide analysis of saliva samples was performed using scaled-down QuEChERS extraction with LC-MS/MS and GC-MS/MS. The optimum extraction procedure using acidified acetonitrile was applicable to 336 pesticides (287 for LC-MS/MS and 49 for GC-MS/MS). To determine pesticide multiresidues in saliva, 100 μL of the sample was extracted with 200 μL of 0.1% formic acid in acetonitrile, and the initial extract was partitioned with 40 mg of MgSO₄ and 10 mg of NaCl. The organic supernatants (120 μL) were then mixed with acetonitrile (30 μL) for matrix-matching (4:1, v/v), and the final extract solution was injected into the LC-MS/MS (4 μL) and GC-MS/MS (2 μL) systems. The established analytical method showed a good LOQs between 5 and 25 ng/mL with reliable accuracy/precision values and recovery results (50-140%) for the target pesticides. Under the two different storage conditions, most of the analytes did not undergo chemical changes in the saliva samples, whereas some pesticides were more stable in freeze-thaw processes than those left at room temperature. Biomonitoring of farmers (ten mixers and ten sprayers) was successfully applied using the validated method, and two carbamates (fenobucarb and propamocarb) were determined at trace concentrations (12.5-675.0 ng/mL from 11 positively detected samples).

Exploring a novel silicone surfactant-based deep eutectic solvent functionalized magnetic iron particles for the extraction of organophosphorus pesticides in vegetable samples

The current study discussed the use of silicone surfactant-based deep eutectic solvent as a surface modifier for magnetic iron particles (Fe₃O₄) to produce a novel adsorbent and its application for the extraction of organophosphorus pesticides (OPPs) in vegetable samples. A deep eutectic solvent (DES) was prepared using low toxic and inexpensive substances such as silicone surfactant (SS) and dodecanoic acid (DoAc). This new eco-friendly SS:DoAc based DES was explored as a substitution to traditional organic reagents for surface modification of Fe₃O₄ to increase the adsorption capacity and to reduce the matrix interferences, hazardous waste generation and environmental pollution. The newly synthesized SS:DoAc@Fe₃O₄ adsorbent was successfully characterized and applied in magnetic solid phase extraction (MSPE). Under optimized conditions, the proposed approach exhibited excellent linearity ranging from 0.1 to 200 µg/kg (R² ≥ 0.9970), low detection limit (0.03-0.1 µg/kg) and acceptable relative recovery (80-119 %) for the studied OPPs.

Rapid detection of sulfonamide antibiotics residues in swine urine by surface-enhanced Raman spectroscopy

Surface enhanced Raman spectroscopy (SERS) combined with rapid pretreatment technique was used to determine sulfonamide antibiotics (sulfadiazine and sulfathiazole) residue in swine urine. Au nanoparticles (AuNPs) were synthesized as Raman enhance substrate and the extraction of swine urine was purified with primary secondary amine (PSA), octadecyl silane (C₁₈) and graphitized carbon (GCB) to eliminate the interference of the matrix and different dosages of adsorbents (PSA, C₁₈, GCB) were investigated. The results showed that the treatment with C₁₈ of 150 mg, GCB of 200 mg and PSA of 200 mg were an excellent approach for rapidly detecting sulfonamide antibiotics residue in swine urine. Combined with density functional theory calculation (DFT), Raman characteristic peaks of 819, 1102, 1173, 1588 cm^-1 and 825, 1127 cm^-1 were selected for qualitative and quantitative assessment of sulfadiazine and sulfathiazole in swine urine, respectively. Based on raman characteristic peak of 819 cm^-1, a good linear relationship between sulfadiazine concentration and Raman intensity was developed with R² = 0.9912, and based on raman characteristic peak of 825 cm^-1, a good linear relationship between sulfathiazole concentration and Raman intensity was developed with R² = 0.9941. And recoveries for five unknown concentration samples predicted were 98.47 ∼ 105.18% with relative standard deviation (RSD) of 1.53% ∼ 5.18%. This study demonstrated that SERS coupled with a quick, easy, cheap, effective, rugged, and safe (QuEChERS) method could be employed to rapidly examine the sulfonamide antibiotics residue in swine urine towards its quality and safety monitoring.

Pesticide residues in fruits and vegetables in Indonesia: findings of five-year proficiency testing

The first proficiency testing of pesticides in fruits and vegetables in Indonesia is reported. This report covers the findings of five-year proficiency testings. Every year, from 2016 to 2020, 18-25 laboratories join the proficiency testings and analyze 5-11 pesticides in tomato, orange, lettuce, brown rice, strawberry respectively. The number of laboratories participating in the proficiency testings tends to increase, although only 38 % of the laboratories are able to report all pesticides. More than 72 % of participants use QuEChERS or its modifications for sample preparation, all participants use gas chromatography or liquid chromatography for separation, at least 20 % of participants still rely on detectors other than mass spectrophotometer for detection, and 20 %-60 % of participants use matrix-matched calibration for quantification. The performance of laboratories is evaluated as z-score with an average of 90.8 % achieves satisfactory results while 3.3 % and 5.9 % achieve questionable and unsatisfactory results correspondingly. Overall, the performance of laboratory participants during proficiency testings is good. However, improvement is still needed, especially for the number of target pesticides for multi-residue pesticide analysis. Moreover, unsatisfactory z-scores are likely to be resulted from laboratories which use conventional solvent extraction, use detectors other than mass spectrometers, and are not accredited.

Isolation and Purification of Organophosphorus Hydrolases Secreted from Acetone-acclimated Phosphorus Accumulating Organisms and Study of Their Properties for Hydrophobic Organophosphorus Sensor

The present work studied an acclimation method for phosphorus accumulating organisms (PAOs) with a high content of acetone in culture solutions to develop microbial-based enzyme sensors for highly hydrophobic organophosphorus (OP) pesticides. Through three steps of cultivation and acclimation, only rod-shaped bacteria survived among the various PAOs. The extracellular enzymes released from the acclimated PAOs were salted out by using ammonium sulfate, then purified by a dialysis membrane and a DEAE-Sepharose FF anion exchange column. Two enzyme components were successfully separated-both of which showed hydrolase activity on disodium p-nitrophenyl phosphate (enzyme I, 1.57 μmol/(min·μg); enzyme II, 0.88 μmol/(min·μg) at 45°C). Further, SDS-PAGE gel electrophoresis results showed that the molecular weights of enzymes I and II were about 15.11 and 11.98 kDa, respectively. On this basis, the applicability of the enzyme in hydrophobic OP biosensors was demonstrated.

Recent developments in sample preparation techniques combined with high-performance liquid chromatography: A critical review

This review article compares and contrasts sample preparation techniques coupled with high-performance liquid chromatography (HPLC) and describes applications developed in biomedical, forensics, and environmental/industrial hygiene in the last two decades. The proper sample preparation technique can offer valued data for a targeted application when coupled to HPLC and a suitable detector. Improvements in sample preparation techniques in the last two decades have resulted in efficient extraction, cleanup, and preconcentration in a single step, thus providing a pathway to tackle complex matrix applications. Applications such as biological therapeutics, proteomics, lipidomics, metabolomics, environmental/industrial hygiene, forensics, glycan cleanup, etc., have been significantly enhanced due to improved sample preparation techniques. This review looks at the early sample preparation techniques. Further, it describes eight sample preparation technique coupled to HPLC that has gained prominence in the last two decades. They are (1) solid-phase extraction (SPE), (2) liquid-liquid extraction (LLE), (3) gel permeation chromatography (GPC), (4) Quick Easy Cheap Effective Rugged, Safe (QuEChERS), (5) solid-phase microextraction (SPME), (6) ultrasonic-assisted solvent extraction (UASE), and (7) microwave-assisted solvent extraction (MWASE). SPE, LLE, GPC, QuEChERS, and SPME can be used offline and online with HPLC. UASE and MWASE can be used offline with HPLC but have also been combined with the online automated techniques of SPE, LLE, GPC, or QuEChERS for targeted analysis. Three application areas of biomedical, forensics, and environmental/industrial hygiene are reviewed for the eight sample preparation techniques. Three hundred and twenty references on the eight sample preparation techniques published over the last two decades (2001-2021) are provided. Other older references were included to illustrate the historical development of sample preparation techniques.

Enhancement of Chemiluminescence Intensity of S2* in Non-premixed Hydrogen Microjet Flame in the Photometric Detector for Sulfur Detection

A transparent quartz rod (q) placed vertically on top of a non-premixed hydrogen microjet flame in a flame photometric detector (qFPD) was developed and evaluated for sulfur detection. The microjet flame burned around the quartz rod because of Coanda effect, forming an extended downstream flame zone with a relatively low temperature between 550 and 650 °C, which is favorable to the formation of S₂*. The emission intensity of S₂* and the signal-to-noise ratio (SNR) of sulfur response were enhanced 2.6- and 2.1-fold, respectively. It was found that the quartz rod of diameter 4 mm with a tip shape of semicircle placed 6 mm above the nozzle yielded the highest SNR. The limits of detection (LOD) for seven kinds of tested sulfur-containing compounds of qFPD were 0.3-0.5 pg S s^-1, which is 5-7 times better than that of commercially available FPD detectors (LOD: 1.6-2.8 pg S s^-1). The selectivity of sulfur over carbon was 10⁵ on qFPD when the SNR for the mass flow rate of S and C atoms was ∼3 times. It was the first time that a quartz rod was used vertically on top of a microjet hydrogen-rich flame in FPD to enhance the chemiluminescence of S₂* and improve the LOD down to 0.3-0.5 pg S s^-1.

Optimization of QuEChERS extraction for detection and quantification of 20 antidepressants in postmortem blood samples by LC-MS/MS

In this study, a comprehensively optimization of QuEChERS (quick, easy, cheap, effective, rugged and safe) method using design of experiments (DOE) was conducted to evaluate the best conditions to obtain the most effective extraction. Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) analysis was performed to identify and quantify the antidepressants, with electrospray ionization acquired in positive mode. The method was validated for all analytes; the calibration curves were linear from 10-1000ng/mL, with R²>0.98, and with LOD and LOQ defined as 10ng/mL. Method imprecision and bias were less than 14.3% and 18.9%, respectively. Neither carryover nor interferences were observed. Overall, the optimized method was applied in postmortem real sample analysis to quantify the antidepressants. This study showed a viable method that can be applied for routine forensic analysis, with a quick and easy sample preparation and a rapid total run time of 8min for each analysis.

Miniaturized vortex assisted-dispersive molecularly imprinted polymer micro-solid phase extraction and HPLC-MS/MS for assessing trace aflatoxins in cultured fish

A dispersive micro-solid phase extraction approach using a molecularly imprinted polymer as an adsorbent has been developed for pre-concentrating aflatoxins from cultured fish. Aflatoxins were first isolated from fish muscle and liver by an ultrasound assisted extraction procedure using a 60 : 40 acetonitrile/0.1 M KH2PO4 aqueous buffer (pH 6.0) mixture. Polymeric adsorbent beads were synthesized using 5,7-dimethoxycoumarin as a dummy template, methacrylic acid as a functional monomer, divinylbenzene as a crosslinker, and 2,2'-azobisisobutyronitrile as an initiator. Parameters affecting the steps of extraction procedure, including the sample (fish extract) pH, adsorption stirring speed and time, desorption stirring speed and time, elution solvent ratio, and polymer capacity, were investigated and optimized. The limit of detection was found to vary from 0.29 to 0.61 μg kg-1 for the several aflatoxins. The proposed method was shown to be accurate and precise. Intraday and inter-day relative standard deviations were lower than 20%, and intraday and inter-day analytical recoveries were within the 80-100% range. The prepared adsorbent in the dispersive micro-solid phase extraction format was re-usable, and the pre-concentration procedure was found to be simple, rapid and highly selective and sensitive to identify/quantify AFs in fish.

Simultaneous quantification of three tropane alkaloids in goji berries by cleanup of the graphene/hexagonal boron nitride hybrids and ultra-high-performance liquid chromatography tandem mass spectrometry

A modified quick, easy, cheap, effective, rugged and safe method was established for simultaneous determination of atropine, anisodamine, and scopolamine in goji berries by using ultra-high-performance liquid chromatography with tandem mass spectrometry. The graphene/hexagonal boron nitride hybrids were prepared and first applied as a cleanup adsorbent. Compared to classical cleanup adsorbent (C₁₈ ), the graphene/hexagonal boron nitride hybrids as adsorbent had better extraction efficiency for the detection of analytes. Under the optimal conditions, the proposed analytical method achieved satisfactory linearity (R²  > 0.995), and obtained desirable recoveries ranged from 77.4 to 94.0% with the relative standard deviation of 1.2-6.1% at the concentration levels of 3.2-13.4 µg/kg. The limits of quantitation of atropine, anisodamine, and scopolamine were, respectively, 3.2, 4.6, and 4.5 µg/kg with linearity ranged from 3.2 to 25.4 µg/kg. The modified quick, easy, cheap, effective, rugged, and safe sample preparation with ultra-high-performance liquid chromatography and tandem mass spectrometry method was successfully applied to evaluate the safety of goji berries collected from 30 plant areas in China, suggesting its applicability and suitability for the routine analysis of three tropane alkaloids in goji berries.

A flame photometric detector with a silicon photodiode assembly for sulfur detection

A flame photometric detector with a silicon photodiode assembly instead of a photomultiplier tube for sulfur detection was developed and evaluated. The photosensitive area of photodiode, the optical design, and band-pass filters, were optimized. It was found that the optimal photosensitive area of the photodiode was 100 (mm)², and three focus lenses combined with a broad band-pass filter of 378/52 nm and a QB21 glass yielded the best result. This design fully utilized the wide emission spectrum of S₂*, the response characteristics of silicon photodiode, and effective absorption of strong emission spectrums of OH* at wavelength around 310 nm by QB21 glass. The limits of detection for nine kinds of sulfur containing compounds were between 5.8 × 10^-12 to 9.5 × 10^-12 g s^-1. This mode provided a linear response of 3 orders of magnitude for compounds being tested and a selectivity of sulfur over carbon of 10⁵. It is demonstrated for the first time that the overall performance of the flame photometric detector integrated with a silicon photodiode assembly work at room temperature was comparable to a conventional detector coupled with a photomultiplier tube, with advantages of short equilibration time, robust to electromagnetic interference and vibration, and low cost. The new detector can find wide application in gas chromatography and on-line monitoring instruments for sulfur measurement.

A beta-cyclodextrin-functionalized magnetic metal organic framework for efficient extraction and determination of prochloraz and triazole fungicides in vegetables samples

A β-cyclodextrin-functionalized magnetic zinc-metal organic framework (M-MOF/β-CD) was synthesized via a facile one-pot reaction. M-MOF/β-CD was used as a magnetic porous absorbent for the extraction and determination of prochloraz and three triazole fungicides in vegetable samples. M-MOF/β-CD was prepared by creating MOF layers on the surface of a Fe₃O₄-graphene oxide (GO) nanocomposite and bonding them with β-CD molecules. Characterization suggested that a 3D porous structure was formed, with M-MOF/β-CD exhibiting high superparamagnetism and a large surface area. As a new strategy, integrating MOFs with Fe₃O₄-GO could improve their water-resistance and mechanical strength by providing a rigid nanosupport interface. Combining M-MOF and β-CD resulted in excellent selective adsorption capacities for prochloraz and three triazole fungicides. The static adsorption process was evaluated and the results were in good agreement with the Freundlich model. Subsequently, M-MOF/β-CD was applied to extracting prochloraz and triazole fungicides from tomato and lettuce vegetables, followed by HPLC-MS/MS determination. The limits of detection for the above fungicides were found to be 0.25-1.0 μg/L at a signal-to-noise ratio of 3, with spiked recoveries of 74.13%-119.83%, indicating that M-MOF/β-CD was promising for application to the extraction and determination of fungicides in complex matrices.

Untargeted metabolic profiling of dogs with a suspected toxic mitochondrial myopathy using liquid chromatography-mass spectrometry

'Go Slow myopathy' (GSM) is a suspected toxic myopathy in dogs that primarily occurs in the North Island of New Zealand, and affected dogs usually have a history of consuming meat, offal or bones from wild pigs (including previously frozen and/or cooked meat). Previous epidemiological and pathological studies on GSM have demonstrated that changes in mitochondrial structure and function are most likely caused by an environmental toxin that dogs are exposed to through the ingestion of wild pig. The disease has clinical, histological and biochemical similarities to poisoning in people and animals from the plant Ageratina altissima (white snakeroot). Aqueous and lipid extracts were prepared from liver samples of 24 clinically normal dogs and 15 dogs with GSM for untargeted liquid chromatography-mass spectrometry. Group-wise comparisons of mass spectral data revealed 38 features that were significantly different (FDR<0.05) between normal dogs and those with GSM in aqueous extracts, and 316 significantly different features in lipid extracts. No definitive cause of the myopathy was identified, but alkaloids derived from several plant species were among the possible identities of features that were more abundant in liver samples from affected dogs compared to normal dogs. Mass spectral data also revealed that dogs with GSM have reduced hepatic phospholipid and sphingolipid concentrations relative to normal dogs. In addition, affected dogs had changes in the abundance of kynurenic acid, various dicarboxylic acids and N-acetylated branch chain amino acids, suggestive of mitochondrial dysfunction.

QuEChERS - Fundamentals, relevant improvements, applications and future trends

The Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method is a simple and straightforward extraction technique involving an initial partitioning followed by an extract clean-up using dispersive solid-phase extraction (d-SPE). Originally, the QuEChERS approach was developed for recovering pesticide residues from fruits and vegetables, but rapidly gained popularity in the comprehensive isolation of analytes from different matrices. According to PubMed, since its development in 2003 up to November 2018, about 1360 papers have been published reporting QuEChERS as extraction method. Several papers have reported different improvements and modifications to the original QuEChERS protocol to ensure more efficient extractions of pH-dependent analytes and to minimize the degradation of labile analytes. This analytical approach shows several advantages over traditional extraction techniques, requiring low sample and solvent volumes, as well as less time for sample preparation. Furthermore, most of the published studies show that the QuEChERS protocol provides higher recovery rate and a better analytical performance than conventional extraction procedures. This review proposes an updated overview of the most recent developments and applications of QuEChERS beyond its original application to pesticides, mycotoxins, veterinary drugs and pharmaceuticals, forensic analysis, drugs of abuse and environmental contaminants. Their pros and cons will be discussed, considering the factors influencing the extraction efficiency. Whenever possible, the performance of the QuEChERS is compared to other extraction approaches. In addition to the evolution of this technique, changes and improvements to the original method are discussed.

Recent advances of online coupling of sample preparation techniques with ultra high performance liquid chromatography and supercritical fluid chromatography

Ultra high performance liquid chromatography and supercritical fluid chromatography techniques are favored because of their high efficiency and fast analysis speed. Although many sample preparation techniques have been coupled with common liquid chromatography online, the online coupling of sample preparation with the two popular chromatography techniques have gained increasing attention owing to the increasing requirements of efficiency and sensitivity. In this review, we have discussed and summarized the recent advances of the online coupling of sample preparation with ultra high performance liquid chromatography and supercritical fluid chromatography techniques. The main sample preparation techniques that have been coupled with ultra high performance liquid chromatography online are solid-phase extraction and in-tube solid-phase microextraction, while solid-phase extraction and supercritical fluid extraction are the main techniques that have been coupled with supercritical fluid chromatography online. Especially, the strategies for online coupling of sample preparation with chromatography techniques were summarized. Typical applications and growing trends of the online coupling techniques were also discussed in detail. With the increasing demands of improving the efficiency, throughput, and analytical capability toward complex samples of the analysis methods, online coupling of sample preparation with chromatography techniques will acquire further development.

Clinical Mass Spectrometry in the Bioinformatics Era: A Hitchhiker's Guide

Mass spectrometry (MS) is a sensitive, specific and versatile analytical technique in the clinical laboratory that has recently undergone rapid development. From initial use in metabolic profiling, it has matured into applications including clinical toxicology assays, target hormone and metabolite quantitation, and more recently, rapid microbial identification and antimicrobial resistance detection by matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). In this mini-review, we first succinctly outline the basics of clinical mass spectrometry. Examples of hard ionization (electron ionization) and soft ionization (electrospray ionization, MALDI) are presented to demonstrate their clinical applications. Next, a conceptual discourse on mass selection and determination is presented: quadrupole mass filter, time-of-flight mass spectrometer and the Orbitrap; and MS/MS (tandem-in-space, tandem-in-time and data acquisition), illustrated with clinical examples. Current applications in (1) bacterial and fungal identification, antimicrobial susceptibility testing and phylogenetic classification, (2) general unknown urine toxicology screening and expanded new-born metabolic screening and (3) clinical metabolic profiling by gas chromatography are outlined. Finally, major limitations of MS-based techniques, including the technical challenges of matrix effect and isobaric interference; and novel challenges in the post-genomic era, such as protein molecular variants, are critically discussed from the perspective of service laboratories. Computer technology and structural biology have played important roles in the maturation of this field. MS-based techniques have the potential to replace current analytical techniques, and existing expertise and instrument will undergo rapid evolution. Significant automation and adaptation to regulatory requirements are underway. Mass spectrometry is unleashing its potentials in clinical laboratories.

Chemiluminescent Determination of Oxamyl in Drinking Water and Tomato Using Online Postcolumn UV Irradiation in a Chromatographic System

High-performance liquid chromatography (HPLC) was used to separate oxamyl from other pesticides in drinking water and tomato paste. The eluate emerging from the column tail was mixed with an alkaline solution of Co²⁺ in EDTA and irradiated with UV light to induce photolysis of the carbamate in order to obtain free radicals and other reactive species that oxidize luminol and produce chemiluminescence (CL) as a result. The intensity of the CL signal was monitored in the form of chromatographic peaks. Under the optimum operating conditions for the HPLC-UV-CL system, the analyte concentration was linearly related to peak area. The limit of detection as determined in accordance with the IUPAC criterion was 0.17 mg L^-1. Oxamyl was successfully extracted with recoveries of 88.7-103.1% from spiked tomato paste by using a simple QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) sample preparation approach. Similar recoveries were obtained from drinking water samples spiked with oxamyl concentrations above the LOD. The proposed method is a simple, fast, accurate choice for quantifying this pesticide.

Simultaneous determination of furfural and its degradation products, furoic acid and maleic acid, in transformer oil by the reversed-phase vortex-assisted liquid-liquid microextraction followed by high-performance liquid chromatography

To explore why the use of furfural as a transformer oil-paper insulation aging characteristic is problematic in real world application, we developed a method for the simultaneous determination of furfural, furoic acid, and maleic acid in transformer oil by reversed-phase vortex-assisted liquid-liquid microextraction combined with high-performance liquid chromatography. The conditions for the proposed method were optimized, and the obtained extract can be directly analyzed by high-performance liquid chromatography. The detection limits (signal-to-noise ratio = 3) of the method ranged from 1.0 to 4.6 μg/L, the enrichment factors for furfural, furoic acid, maleic acid, and fumaric acid were 4.6, 25.1, 15.6, and 17.5, respectively, and the recovery rates for three analytes (fumaric acid was undetected) range from 82.1 to 106.2%. The contents of furfural, furoic acid, and maleic acid resulted from accelerated aging of transformer insulation oil-paper were measured using the present method for the first time, and the aging samples were analyzed by liquid chromatography with mass spectrometry for the identification of furoic acid and maleic acid in the aging transformer oil samples. Using the optimal method, the target products of samples at different aging time were tracked and measured.

Dynamic residual pattern of azoxystrobin in Swiss chard with contribution to safety evaluation

This study aimed at quantifying the residual amount of azoxystrobin in Swiss chard samples grown under greenhouse conditions at two different locations (Gwangju and Naju, Republic of Korea). Samples were extracted with acetonitrile, separated by salting out, and subjected to purification by using solid-phase extraction. The analyte was identified using liquid chromatography-ultraviolet detection. The linearity of the calibration range was excellent with coefficient of determination 1.00. Recovery at three different spiking levels (0.1, 0.5, and 4 mg/kg) ranged between 82.89 and 109.46% with relative standard deviation <3. The limit of quantification, 0.01 mg/kg, was considerably much lower than the maximum residue limit (50 mg/kg) set by the Korean Ministry of Food and Drug Safety. The developed methodology was successfully used for field-treated leaves, which were collected randomly at 0-14 days following azoxystrobin application. The rate of disappearance in/on Swiss chard was ascribed to first-order kinetics with a half-life of 8 and 5 days, in leaves grown in Gwangju and Naju greenhouses, respectively. Risk assessments revealed that the acceptable daily intake percentage is substantially below the risk level of consumption at day 0 (in both areas), thus encouraging its safe consumption.