Strong Anion-exchange Cartridge Research Articles

Automated synthesis of [89Zr]ZrCl4, [89Zr]ZrDFOSquaramide-bisPh(PSMA) and [89Zr]ZrDFOSquaramide-TATE

BackgroundAutomated [89Zr]Zr-radiolabeling processes have the potential to streamline the production of [89Zr]Zr-labelled PET imaging agents. Most radiolabeling protocols use [89Zr][Zr(ox)4]4− as the starting material and oxalate is removed after radiolabeling. In some instances, radiolabeling with [89Zr]ZrCl4 as starting material gives better radiochemical yields at lower reaction temperatures. In this work, a fully-automated process for production of [89Zr]ZrCl4 is reported and its use for the synthesis of [89Zr]ZrDFOSq-bisPhPSMA and [89Zr]ZrDFOSq-TATE.ResultsA simple automated process for the isolation of [89Zr]ZrCl4 by trapping [89Zr][Zr(ox)4]4− on a bicarbonate-activated strong anion exchange cartridge followed by elution with 0.1 M HCl in 1 M NaCl was developed. [89Zr]ZrCl4 was routinely recovered from [89Zr][Zr(ox)4]4− in > 95% yield in mildly acidic solution of 0.1 M HCl in 1 M NaCl using a fully-automated process. The [89Zr]ZrCl4 was neutralized with sodium acetate buffer (0.25 M) removing the requirement for cumbersome manual neutralization with strong base. The mixture of [89Zr]ZrCl4 was used for direct automated radiolabeling reactions to produce [89Zr]Zr-DFOSquaramide-bisPhPSMA and [89Zr]ZrDFOSquaramide-TATE in 80–90% over all RCY in > 95% RCP.ConclusionsThis method for the production of [89Zr]ZrCl4 does not require removal of HCl by evaporation making this process relatively fast and efficient. The fully automated procedures for the production of [89Zr]ZrCl4 and its use in radiolabeling are well suited to support the centralized and standardized manufacture of multiple dose preparations of zirconium-89 based radiopharmaceuticals.

Determination of highly polar anionic pesticides in beehive products by hydrophilic interaction liquid chromatography coupled to mass spectrometry.

The analysis of highly polar pesticides is challenging due to their unique physicochemical properties, requiring specialized chromatographic techniques for their accurate and sensitive detection. Furthermore, the high level of co-extracted polar matrix components that can co-elute with the analytes can interfere with the analysis. Consequently, there is lack of pesticide monitoring data, as the European Food Safety Authority has pointed out. This article explores the overcoming of such difficulties in the analysis of these compounds. Analytical methodologies for the extraction, clean-up, and direct determination of 11 highly polar anionic pesticides, including glyphosate, glufosinate, ethephon, fosetyl-aluminium, and their related metabolites in complex food matrices such as honey and pollen by hydrophilic interaction liquid chromatography coupled to tandem mass spectrometry were successfully developed and validated. Solid-phase extraction and micro-solid-phase extraction employing strong anion exchange (SAX) cartridges were implemented for clean-up. The automation and miniaturization of SAX clean-up for these compounds were achieved for the first time. For method validation, SANTE/11312/2021 guideline was followed. Recoveries were between 70 and 120%, with RSDs below 20%. Limits of quantitation ranged from 0.005 to 0.020 mg kg-1. Linearity was evaluated from 0.002 to 0.200 mg kg-1. Matrix effects were assessed, showing medium to low signal suppression for most compounds. AMPA and glufosinate presented the highest signal suppression, but it was reduced after SAX clean-up. Analysis of real honey and pollen samples revealed the occurrence of the studied compounds in beehive products and showed the applicability of the validated methodologies for routine control of these complex samples.

Development of a safer and improved analytical method for polycyclic aromatic hydrocarbons in creosote products

Polycyclic aromatic hydrocarbons (PAHs) in creosote products used for wood preservation are regulated in Japan. Although the analytical method for this regulation has been stipulated by law, two main problems have been highlighted, namely the use of dichloromethane, a potential carcinogen, as a solvent and inadequate purification. Therefore, an analytical method to solve these problems was developed in this study. Actual creosote-treated wood samples were examined, and it was found that acetone could be used as an alternative solvent. Purification methods using centrifugation, silica gel cartridges, and strong anion exchange (SAX) cartridges were also developed. It was found that the SAX cartridges strongly retained PAHs, and an effective purification method was developed using this phenomenon, in which contaminants were removed by washing with diethyl ether/hexane (1/9 v/v), which could not be achieved with a silica gel cartridge. This strong retention was attributed to cation–π interactions. The analytical method developed in this study yielded good recoveries (81.4–113.0%) with low relative standard deviations (<6.8%), and the limit of quantification (0.02–0.29 µg/g) was significantly lower than the current creosote product regulation. Therefore, this method can safely and effectively extract and purify PAHs from creosote products.

Enzymatic bioconversion of beechwood xylan into the antioxidant 2′-O-α-(4-O-methyl-D-glucuronosyl)-xylobiose

Acidic xylooligosaccharides (XOS), also called aldouronics, are hetero-oligomers of xylose randomly branched with 4-O-methyl-D-glucuronic acid residues linked by α(1 → 2) bonds, which display bioactive properties. We have developed a simple and integrated method for the production of acidic XOS by enzymatic hydrolysis of a glucurono-xylan from beechwood. Among the enzymes screened, Depol 670L (a cellulolytic preparation from Trichoderma reesei) displayed the highest activity (70.3 U/mL, expressed in reducing xylose equivalents). High-performance anion-exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD) analysis revealed the formation of a neutral fraction (corresponding to linear XOS, mainly xylose and xylobiose) and a group of more retained products (acidic XOS), which were separated using strong anion-exchange cartridges. The acidic fraction contained a major product, characterized by matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry and mono- and two-dimensional nuclear magnetic resonance spectroscopy (NMR) as 2′-O-α-(4-O-methyl-α-D-glucuronosyl)-xylobiose (X2_MeGlcA). Starting from 2 g of beechwood xylan, 1.5 g of total XOS were obtained, from which 225 mg (11% yield) corresponded to the aldouronic X2_MeGlcA. The acidic XOS exhibited higher antioxidant activity (measured by the ABTS·+ discoloration assay) than xylan, whilst neutral XOS displayed no antioxidant activity. This work demonstrates that it is possible to obtain a safe and natural antioxidant by enzymatic biotransformation of hardwood hemicellulose.

Trace level enrichment and clean-up of β-lactam antibiotic residues in edible chicken tissues and feathers by solid phase extraction for quantitative determination utilizing liquid chromatography

ABSTRACT. A simple analytical method for the extraction and determination of three β-lactam antibiotics in chicken tissues and feather samples was developed and validated using solid phase extraction (SPE) and liquid chromatography-ultraviolet, LC-UV, detection. The analytes were extracted with strong anion exchange (SAX) cartridges for the extract clean-up and enrichment before introduction into the LC system. The validation was carried out based on the recommendations from Commission Decision 2002/657/EC. Under optimised conditions, the proposed method offers correlation coefficients of r2 ≥ 0.9991 for all the studied analytes in both matrices. Percent recovery results were found to vary between 79.7-101.8% and 94.2-101.6% for chicken feathers and tissues, respectively, with the relative standard deviation, RSD &lt; 8.4%. The limits of detection (LOD) were in the range of 0.1-0.13 µg kg-1 and 0.1-0.15 µg kg-1 while the limits of quantification (LOQ) were in the range of 0.3-0.38 µg kg-1 and 0.3-4.5 µg kg-1 in chicken feathers and tissues, respectively. The proposed method offers good sensitivity and selectivity and all the results demonstrating that the method would be widely used for determination of β-lactam antibiotics and other trace level antibiotics residues having similar physical and chemical properties in the matrices of varying origins.&#x0D; &#x0D; KEY WORDS: Chicken tissues, Chicken feathers, β-Lactams, Solid phase extraction, LC-UV&#x0D; &#x0D; Bull. Chem. Soc. Ethiop. 2022, 36(3), 503-519. &#x0D; DOI: https://dx.doi.org/10.4314/bcse.v36i3.2

Automated synthesis of [18F]Ga-rhPSMA-7/ -7.3: results, quality control and experience from more than 200 routine productions

IntroductionThe radiohybrid (rh) prostate-specific membrane antigen (PSMA)-targeted ligand [18F]Ga-rhPSMA-7 has previously been clinically assessed and demonstrated promising results for PET-imaging of prostate cancer. The ligand is present as a mixture of four stereoisomers ([18F]Ga-rhPSMA-7.1, − 7.2, − 7.3 and − 7.4) and after a preclinical isomer selection process, [18F]Ga-rhPSMA-7.3 has entered formal clinical trials. Here we report on the establishment of a fully automated production process for large-scale production of [18F]Ga-rhPSMA-7/ -7.3 under GMP conditions (EudraLex).Methods[18F]Fluoride in highly enriched [18O]H2O was retained on a strong anion exchange cartridge, rinsed with anhydrous acetonitrile and subsequently eluted with a solution of [K+ ⊂ 2.2.2]OH− in anhydrous acetonitrile into a reactor containing Ga-rhPSMA ligand and oxalic acid in DMSO. 18F-for-19F isotopic exchange at the Silicon-Fluoride Acceptor (SiFA) was performed at room temperature, followed by dilution with buffer and cartridge-based purification. Optimum process parameters were determined on the laboratory scale and thereafter implemented into an automated synthesis. Data for radiochemical yield (RCY), purity and quality control were analyzed for 243 clinical productions (160 for [18F]Ga-rhPSMA-7; 83 for [18F]Ga-rhPSMA-7.3).ResultsThe automated production of [18F]Ga-rhPSMA-7 and the single isomer [18F]Ga-rhPSMA-7.3 is completed in approx. 16 min with an average RCY of 49.2 ± 8.6% and an excellent reliability of 98.8%. Based on the different starting activities (range: 31–130 GBq, 89 ± 14 GBq) an average molar activity of 291 ± 62 GBq/μmol (range: 50–450 GBq/μmol) was reached for labeling of 150 nmol (231 μg) precursor. Radiochemical purity, as measured by radio-high performance liquid chromatography and radio-thin layer chromatography, was 99.9 ± 0.2% and 97.8 ± 1.0%, respectively.ConclusionThis investigation demonstrates that 18F-for-19F isotopic exchange is well suited for the fast, efficient and reliable automated routine production of 18F-labeled PSMA-targeted ligands. Due to its simplicity, speed and robustness the development of further SiFA-based radiopharmaceuticals is highly promising and can be of far-reaching importance for future theranostic concepts.

Tetrabutylammonium tosylate as inert phase-transfer catalyst: The key to high efficiency SN2 radiofluorinations

Here we describe use of the tetrabutylammonium p-toluenesulfonate (TBAOTs) as an inert phase transfer catalyst allowing high efficient aliphatic radiofluorination of labeling precursors for the preparation of common radiotracers using only 0.2–1.2 mg of the substrates. With operational convenience (no need for azeotropic drying) and compatibility with the common types of strong anion-exchange cartridges (QMA), this method has a high potential for routine application in various automated synthesizers and offers significant costs reductions due to less precursors used.

Analysis of folic acid in white rice by ultra-fast liquid chromatography

The method of analysis was standardized, and the folic acid content was determined in samples of fortified white rice (Z, G and D) and unfortified (E and O). The analysis was performed in triplicate in samples of 2.0000 g, hydrolysis was performed with phosphate buffer pH 8.82 for one hour and then lowered to pH 7.00 for enzymatic treatment with takadiastase at 65°C. The extracts were filtered by gravity, purified with nylon syringe filters and ion exchange cartridges (solid phase extraction using strong anion exchange cartridges). The concentration in mg folic acid/kg of rice, in each extract was determined by ultrafast liquid chromatography, with average values for Lot1 of the fortified rice samples, of 44.03, 51.95, 38.08, and unfortified samples of 31.51 and 21.94, and with respect to Lot2 of 41.26, 41.27, 34.54 for fortified ones and 24.92 and 20.94 for non-fortified ones, respectively. The concentration of folic acid obtained by filtration through syringe filters was higher than in the extracts purified by solid phase extraction using strong anion exchange cartridges, evidencing loss of the analyte. The recovery of folic acid in the samples doped and purified by syringe filters was around 65.00%, while by solid phase extraction using strong anion exchange cartridges 43.00%. There is evidence of variation in the folic acid content between different batches of rice of the same brand.

Field-amplified sample injection and sweeping micellar electrokinetic chromatography in analysis of glyphosate and aminomethylphosphonic acid in wheat

Glyphosate, a widely used herbicide, has been classified as probably carcinogenic to humans by the International Agency for Research on Cancer (IARC). In the present study a method based on Field-Amplified Sample Injection and Sweeping Micellar Electrokinetic Chromatography (FASI sweep-MEKC) has been developed and validated for determination of glyphosate and its microbial metabolite aminomethylphosphonic acid (AMPA) in wheat flour. The method involved a preliminary solid phase extraction for cleanup of the aqueous extracts from wheat flour, based sequentially on C18 and strong anion exchange cartridges, followed by derivatization using 9-fluorenylmethylchloroformate. Optimization of sample cleanup and derivatization procedure was carried out by a HPLC-UV method, whereas FASI sweep-MEKC was applied for achieving the sensitivity necessary for analysis of real samples. To this regard, optimum conditions involved the use of an extended path fused-silica capillary (80 cm total length, 50 μm, i.d.) filled with a high concentration buffer (sodium phosphate 100 mM, pH 2.2). Electrokinetic sampling was carried out at −10 kV with injection time of 700 s and the separation of the loaded analytes was performed under MEKC conditions using sodium phosphate buffer 50 mM at pH 2.2, supplemented with sodium dodecyl sulfate, 100 mM. The method was validated for linearity, precision, accuracy and sensitivity, showing that using conventional UV detection (210 nm) the achieved limit of quantitation (LOQ) values for both the analytes were widely lower than those set by Authorities. In particular, LOQ for glyphosate and AMPA were found to be 5 and 2.5 ng/mL, respectively, corresponding to 0.1 and 0.05 mg/kg, in wheat flour. The method, applied to commercially available real samples (wheat flour from different manufacturers) and to an experimental sample obtained by cv. Svevo wheat, can be considered as a convenient alternative to the existing approaches in analysis of complex matrices.

Total determination of residual flutolanil and its metabolites in livestock products and seafood using liquid chromatography-tandem mass spectrometry

ABSTRACTWe have developed a simple and sensitive LC-MS/MS analytical method for the determination of residual flutolanil and its principal metabolites, including α,α,α-trifluoro-3′-hydroxy-o-toluanilide (M-4) and its conjugates, in livestock and seafood products. Both flutolanil and its metabolites contain the 2-(trifluoromethyl)benzoic acid (2-TFMBA) moiety. In this method, flutolanil and its metabolites are converted to 2-TFMBA by hydrolysis. The method involves direct hydrolysis with sodium hydroxide at 200°C, acidification, partitioning into a mixture of ethyl acetate-n-hexane (1:9, v/v), clean-up using a strong anion exchange cartridge (InertSep SAX), and then quantification using LC-MS/MS. The optimal conditions for the complete hydrolysis of flutolanil to 2-TFMBA are an incubation time of 6 h and a temperature of 200°C. The developed method was evaluated using seven types of food: bovine samples of muscle, fat, liver and milk, as well as egg, eel, and freshwater clam. Samples were spiked both at 0.01 mg/kg and at the Japanese maximum residue limit (MRL) established for each food type. The validation results show excellent recoveries (88–107%) and precision (< 10%) for flutolanil and M-4. The limit of quantification (S/N ≥ 10) of the developed method is 0.01 mg/kg. The developed method is applicable to the definition of residual flutolanil for animal-based food commodities and MRLs established by the Codex Alimentarius, and will be useful for the regulatory monitoring of residual flutolanil and its metabolites in food products.

Automated concentration of [18F]fluoride into microliter volumes

Concentration of [18F]fluoride has been mentioned in literature, however, reports have lacked details about system designs, operation, and performance. Here, we describe in detail a compact, fast, fully-automated concentration system based on a micro-sized strong anion exchange cartridge. The concentration of radionuclides enables scaled-up microfluidic synthesis. Our system can also be used to provide highly concentrated [18F]fluoride with minimal water content. We demonstrate how the concentrator can produce varying concentrations of [18F]fluoride for the macroscale synthesis of N-boc-5-[18F]fluoroindole without an azeotropic drying process, while enabling high starting radioactivity. By appropriate choice of solid-phase resin, flow conditions, and eluent solution, we believe this approach can be extended beyond [18F]fluoride to other radionuclides.

Comparison of Enrichment Methods for Intact N- and O-Linked Glycopeptides Using Strong Anion Exchange and Hydrophilic Interaction Liquid Chromatography.

Heterogeneity of protein glycosylation poses great challenges for analysis that is key to understand structure and function of glycoproteins. Resolving this conundrum requires efficient and specific enrichment of intact glycopeptides for identification and quantitation. To this end, hydrophilic interaction chromatography (HILIC) has been commonly used to enrich intact N- and O-linked glycopeptides. However, its effectiveness to enrich isobarically labeled glycopeptides remains unclear. Here, we studied three different enrichment methods for enrichment of N- and O-linked glycopeptides. It was found that removal of N-glycans prior to enrichment of O-linked glycopeptides by HILIC improved identification of O-linked glycopeptides by mass spectrometry. We also compared the enrichment of intact N- and O-linked glycopeptides using other chromatography methods and found that using cartridges containing materials for strong anion exchange (SAX) chromatography increased yield and identification of N- and O-linked glycopeptides. The enrichment of O-linked glycopeptides was further improved when a Retain AX cartridge (RAX) was used. In particular, isobaric tag labeled glycopeptides after C18 desalting could be readily enriched by SAX and RAX cartridges but not by HILIC to enable quantitative glycoproteomics. It is anticipated that the use of SAX and RAX cartridges will facilitate broad applications of identifications and quantitation of glycoproteins.

Comprehensive determination of macrolide antibiotics, their synthesis intermediates and transformation products in wastewater effluents and ambient waters by liquid chromatography–tandem mass spectrometry

Macrolide antibiotics are a prominent group of emerging contaminants frequently found in wastewater effluents and wastewater-impacted aquatic environments. In this work, a novel analytical method for simultaneous determination of parent macrolide antibiotics (azithromycin, erythromycin, clarithromycin and roxithromycin), along with their synthesis intermediates, byproducts, metabolites and transformation products in wastewater and surface water was developed and validated. Samples were enriched using solid-phase extraction on Oasis HLB cartridges and analyzed by reversed-phase liquid chromatography coupled to electrospray ionization tandem mass spectrometry. The target macrolide compounds were separated on an ACE C18 PFP column and detected using multiple reaction monitoring in positive ionization polarity. The optimized method, which included an additional extract clean-up on strong anion-exchange cartridges (SAX), resulted in high recoveries and accuracies, low matrix effects and improved chromatographic separation of the target compounds, even in highly complex matrices, such as raw wastewater. The developed method was applied to the analysis of macrolide compounds in wastewater and river water samples from Croatia. In addition to parent antibiotics, several previously unreported macrolide transformation products and/or synthesis intermediates were detected in municipal wastewater, some of them reaching μg/L levels. Moreover, extremely high concentrations of macrolides up to mg/L level were found in pharmaceutical industry effluents, indicating possible importance of this source to the total loads into ambient waters. The results revealed a significant contribution of synthesis intermediates and transformation products to the overall mass balance of macrolides in the aquatic environment.

Development and Validation of a Cost-Effective HPLC-FLD Method for Routine Analysis of Fumonisins B1 and B2 in Corn and Corn Products

Fumonisins, a type of mycotoxins produced by Fusarium species, can cause fatal diseases in animals and humans. Therefore, regulatory limits for food and feed were established in many countries. Herein, a sensitive, valid, cost-effective, and easily transferable analytical method for quantitative determination of the relevant fumonisins B1 (FB1) and B2 (FB2) in corn and corn products was developed. The final method is based on reversed-phase high-performance liquid chromatography with fluorescence detection (RP-HPLC-FLD). Derivatization of analytes was simplified by establishing an automated precolumn derivatization method by using an autosampler. Strong anion exchange (SAX) cartridges were used instead of widespread immunoaffinity chromatography (IAC) approaches. Analytes and matrix signals were chromatographically separated in a total run time of 25 min by means of a C8 column and a gradient elution using methanol and phosphate buffer. The limits of detection (LODs) for FB1 and FB2 were 29.2 and 17.5 μg/kg, respectively. Obtained recoveries ranged from 79.4 to 94.5 % for FB1 and from 79.9 to 98.0 % for FB2. Positive confirmation of the developed method was achieved by participating in an interlaboratory proficiency testing. Nineteen samples of sweet corn and corn products were analyzed to demonstrate the applicability of the method.

Determination of Underivatized Glyphosate Residues in Plant-Derived Food with Low Matrix Effect by Solid Phase Extraction-Liquid Chromatography-Tandem Mass Spectrometry

A method was developed for the determination of glyphosate residues in plant-derived food using a two-step solid phase extraction (SPE) combined with mixed-mode liquid chromatography-tandem mass spectrometry (LC-MS/MS). The samples were extracted with water. Then, the extracting solution was pretreated by a C18 cartridge to remove protein and weak-polar interferences and further directly extracted using a strong anion exchange (SAX) cartridge to remove neutral and basic substances. The obtained glyphosate residues from the SPE were separated on a hydrophilic interaction/weak anion-exchange (HILIC/WAX) column and detected by mass spectrometry with negative electrospray ionization (ESI-) in multiple reaction monitoring (MRM) mode. This approach was evaluated by five different kinds of plant-derived food (soybean, corn, carrot, apple, and spicy cabbage) matrices in terms of matrix effect and recovery. Results showed that two-step SPE and mixed-mode chromatography separation provided the method with a very low matrix effect, and the spiked recoveries of glyphosate were satisfied in the range of 83.1 to 100.8 % at three spiked levels. The limit of quantification (LOQ) and detection (LOD) of the method in different matrices were 0.016–0.026 and 0.005–0.008 mg kg−1, respectively. The procedure was validated and showed good accuracy and precision over a large linear range of 0.02–10 mg kg−1.

SPE speciation of inorganic arsenic in rice followed by hydride-generation atomic fluorescence spectrometric quantification

Due to high toxicity, inorganic arsenic (iAs) species are the focus of monitoring effort worldwide. In this work arsenic was first extracted from rice by microwave-assisted digestion in HNO3-H2O2, during which As(III) was oxidized to As(V). Silica-based strong anion exchange cartridges were used to separate As(V) from organic forms. After prereduction by iodide, iAs was quantified by hydride-generation atomic fluorescence spectrometry (HG-AFS). This method achieved 1.3 ng g(-1) limit of detection (LOD), and 94 ± 3% and 93 ± 5% recoveries, respectively, for As(III) and As(V) at 100 ng g(-1). Validation was performed using standard reference material NIST 1568a (102 ng g(-1)) and ERM BC211 (124 ng g(-1)) rice flour. By eliminating chromatography, SPE speciation gained throughput and cost advantages. HG-AFS, at 10% budget and operation cost of a typical inductively-couple plasma mass spectrometer (ICPMS), proved highly sensitive and specific for iAs quantification.

Inter-Laboratory Study of an LC-MS/MS Method for Simultaneous Determination of Fumonisin B&lt;sub&gt;1&lt;/sub&gt;, B&lt;sub&gt;2&lt;/sub&gt; and B&lt;sub&gt;3&lt;/sub&gt; in Corn

To validate an LC-MS/MS method using a strong anion exchange cartridge for simultaneous determination of fumonisin B1, B2 and B3 in corn, an inter-laboratory study was performed in 9 laboratories using one fumonisin-negative corn sample, three spiked corn samples (FB1: 100-1,000 μg/kg, FB2 and FB3: 10-100 μg/kg) and two naturally contaminated corn samples. The recoveries were in the ranges of 79.7-87.2% for FB1, 78.6-103.2% for FB2 and 80.1-92.8% for FB3. The relative standard deviations for repeatability (RSDr) ranged from 3.7 to 8.0% for FB1, from 2.6 to 15.3% for FB2 and from 4.3 to 9.7% for FB3. The relative standard deviations for reproducibility (RSDR) for FB1, FB2 and FB3 were in the ranges of 6.3-10.1%, 5.9-18.7% and 9.3-16.0%, respectively. The HorRat values for all analytes ranged from 0.2 to 0.9. The difference of the trueness between the two kinds of commercially available anion exchange cartridges used in this study was not significant (p>0.05). Surveillance for fumonisins in corn grits was performed using the validated method. All of the samples were contaminated with fumonisins and the mean concentrations for FB1, FB2 and FB3 were 118.1, 37.3 and 17.9 μg/kg, respectively. These results indicated that the method for simultaneous determination of FB1, FB2 and FB3 in corn was successfully developed and validated.

Rapid high‐yield N‐acylation of aminothiols: N‐acetylglutathione and N‐acetylhomocysteine and their thiol pKa values

Methodology for the rapid N-acylation of aminothiols in aqueous solution using procedures commonly employed in biochemical studies is described here. Glutathione disulfide (GSSG) and homocystine were diN-acetylated in ~100% yield in 0.1 M aqueous NaHCO3 (pH 8.5) at room temperature by 2.5 equiv of the activated ester, N-hydroxysulfosuccinimidyl acetate, an efficient water-soluble acetylating reagent. Following acetone precipitation, diN-acetylGSSG was further purified and desalted on a strong anion-exchange (SAX) cartridge. DiN-acetylhomocystine was simultaneously purified and desalted on a C18 cartridge. The N-acetylated aminothiols were generated using gel-immobilized tris(2-carboxyethyl)phosphine as a reductant, which obviated the need for further purification. Alternatively, disulfide exchange with dissolved dithiothreitol yielded N-acetylglutathione, which was purified on the SAX cartridge. pH titrations of N-acetylglutathione (8.99) and N-acetylhomocysteine (9.66) as well as those of commercially available N-acetylcysteine (9.53) and N-acetylpenicillamine (10.21) yielded pK(a) (SH) values of importance for biological studies.

Determination of fumonisins B1 and B2 in Chinese rice wine by HPLC using AQC precolumn derivatisation

Fumonisins are a group of naturally occurring mycotoxins produced by various Fusarium species that commonly infect maize and other cereals, including sorghum and rice. In this study a sensitive and selective method was developed for the determination of fumonisins B₁ and B₂ (FB₁ and FB₂) in Chinese rice wine. The method is based on high-performance liquid chromatography and fluorescence detection following precolumn derivatisation with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC). FB₁ and FB₂ in Chinese rice wine were extracted and purified using strong anion exchange cartridges and derivatised with AQC at room temperature. The AQC derivatives were stable for 5 days. Optimal fluorescence was obtained at an excitation wavelength of 246 nm and an emission wavelength of 390 nm. Chromatography was performed using a C18 column and gradient elution at 1 mL min⁻¹ with methanol and 0.05 mol L⁻¹ phosphate buffer at pH 4. The limit of detection was 6 µg L⁻¹ for both FB₁ and FB₂. The method was successfully applied to the determination of FB₁ and FB₂ in Chinese rice wine, with recoveries of 87.5-94.5% being obtained. The established method was stable and sensitive for the determination of FB₁ and FB₂ in Chinese rice wine.

Simultaneous extraction and determination of fluoroquinolones, tetracyclines and sulfonamides antibiotics in soils using optimised solid phase extraction chromatography-tandem mass spectrometry

An analytical method was developed for the simultaneous extraction and determination of 18 fluoroquinolones (FQs), tetracyclines (TCs) and sulfonamides (SAs) antibiotics from soils using solid phase extraction and liquid chromatography-tandem mass spectrometry. The soils were extracted by different solvents with the help of mechanical shaking and ultrasonic treatment at 59 kHz, followed by a strong anion exchange (SAX) cartridge to clean up soil samples and a hydrophilic lipophilic balance (HLB) cartridge as enrichment. The method was evaluated by testing the following variables: extraction solvents, the type of SPE cartridges, solvent volumes, initial spiking levels and soil types (silty clay loam and clay loam soils). The soil extraction method was validated using these two types of soils, representing two typical agricultural soils in northern China. For 2 g soil, the extraction steps with the mixture of potassium phosphate buffer and acetonitrile (ACN) (1/1, v/v, pH 3.2) provided satisfactory recoveries. In the clay loam soil, the recoveries of all the compounds were from 56% to 89% at the spiking level of 50 µg kg−1 soil, and from 69% to 97% at the spiking level of 200 µg kg−1 soil, respectively. Recoveries in silty clay loam soil were similar to that in clay loam. The method was successfully employed using soil samples collected from a farmland and afforestion area irrigated with sewage in northern China. The result indicates that trace antibiotics in sewage may accumulate in soil irrigated by river water containing sewage.