SAX Cartridge Research Articles

Selective Quantification of Organic and Inorganic Arsenic in Kelp Thalli and Kelp-Based Products

Kelp can accumulate large quantities of arsenic compounds even in the absence of considerable environmental pollution. A substantial difference in toxicity between organic and inorganic arsenic compounds makes the form of arsenic relevant for the risk assessment of consuming kelp thalli and kelp-based products.The aim of the study was to develop an analytical procedure for the selective quantification of organic and inorganic arsenic in kelp thalli by inductively coupled plasma mass spectrometry and solid-phase extraction without scheduled precursors.Materials and methods. The authors studied samples of Laminaria saccharina and Laminaria japonica, spiking mixtures of chemical compounds containing arsenic in different oxidation states, and bioactive dietary supplements based on kelp thalli. Solid-phase extraction was performed using Maxi-Clean SAX cartridges. The arsenic content was determined using an Agilent 7900 inductively coupled plasma mass spectrometer.Results. Microwave-assisted extraction with deionised water ensures 91% recovery of arsenic-containing compounds from kelp thalli, and the addition of hydrogen peroxide to the extractant provides complete extraction. Solid-phase extraction with an eluent based on 3% H2O2 can extract the organic fraction from a mixture of organic and inorganic arsenic compounds without washing the inorganic fraction off the cartridge.Conclusions. The authors offer an effective analytical procedure for the selective quantification of organic and inorganic arsenic in kelp thalli and kelp-based products. This procedure allows for the isolation of arsenic-containing compounds from the organic matrix of kelp with 3% hydrogen peroxide. Solid-phase extraction with this extractant can effectively separate organic and inorganic fractions without prior neutralisation of the test solution.

Development and validation of a solid phase extraction-UPLC-MS/MS method for the determination of fifty-nine antimicrobials in commercial organic fertilizers and amended soils

Commercial organic fertilizers often contain high levels of antimicrobials that can be released into agricultural soils and pose potential ecological risks, and there is a significant need to quantify their occurrence in these products. However, the presence of high contents of organic matter, nutrient salts, and trace metals in commercial organic fertilizers pose significant challenges for the extraction and analysis of antimicrobials, especially when multiple compounds are targeted. This study developed a robust and sensitive multi-residue method for the determination of fifty-nine antimicrobials, belonging to four different classes, in commercial organic fertilizers and amended soils. The method was based on ultrasonic extraction with a mixture of EDTA-McIlvaine buffer/methanol/acetonitrile/acetone (5:2:2:1 by volume), solid phase extraction (SPE) using SAX and HLB cartridges in series, followed by UPLC–MS/MS analysis in the dynamic multiple reaction monitoring (MRM) mode. The performance of the optimized extraction method was good for fifty-nine antimicrobials with a median recovery rate of 46 and 84 % in commercial organic fertilizers and amended soils, respectively. The matrix effects were between 105 and 109 % in commercial organic fertilizers and 102–140 % in amended soils, which are indicative of the effectiveness of pretreatment procedures and the accuracy of instrumental analysis. The method had good linearity (R2 > 0.99), and the detection limits and method quantification limits for fifty-nine antimicrobials in commercial organic fertilizers were 0.002–0.206 ng/g (median 0.026 ng/g) and 0.006–0.684 ng/g (median 0.086 ng/g), respectively. This robust and practical method effectively eliminates the matrix effects of commercial organic fertilizer and could be used for routine determination of multiple classes of antimicrobial residues in commercial organic fertilizers and amended soils.

Studies on analytical methods for determination of potassium bromate in foods

A high performance liquid chromatographic (HPLC) method for the determination of bromate in bread and flour has been developed. Bromate was extracted from samples with water. The extract was cleaned by the use of a LiChrolut SAX cartridge (perchlorate form) with 0.06 M sodium perchlorate solution (pH 3.5) as a fluent. Bromate was separated with Zorbax SAX column by using 0.06 M sodium perchlorate solution (pH 3.5) the mobile phase, and detected at 355 nm after derivatization in the post column 80°C. Recovery studies were performed using bread and flour samples each fortified with bromate at 0.2, 0.5 and 1 μg/ml separately. Recoveries were in the range of 80.0-86.1% with coefficients of variation under 1.9%. The limit of detection was 0.1 ppm. For purposes of comparison, a study on high performance ion chromatography for the determination of bromate in flour was performed. Sample solution was prepared in the same way as in HPLC method, except that the sample was passed through an OnGuard-Ag cartridge instead of a LiChrolut SAX cartridge to remove chloride. Bromate was analyzed with Dionex HPIC AS11 and AG11 column by using 0.25 mM sodium hydroxide solution as an eluent, in combination with a conductivity detector. Recovery studies were performed using flour samples fortified with bromate at 1, 2 and 5 μ g/ml. Recoveries were in the range of 79.7-86.3% with coefficients of variation under 3.9%. The limit of detection was 0.5 ppm. Forty bread and ten flour samples collected from various markets were analyzed. No bromate residue was detected in any samples tested.

Field-based application of developed solid phase extraction with inductively coupled plasma mass spectrometry for vanadium speciation analysis of groundwaters from Argentina

High levels of vanadium have been reported in groundwater (<0.05–5300μgL−1 V) from different parts of Argentina, yet no detailed study of vanadium speciation has been performed. A highly selective strong anion exchange – solid phase extraction (SAX-SPE) method was used (in-situ) for vanadium speciation analysis of groundwater samples from La Pampa - LP (General San Martin and Eduardo Castex) and Buenos Aires - BA (San German) provinces in Argentina. In this method both vanadyl (VIV) and vanadate (VV) were trapped by the complexation with disodium ethylenediaminetetraacetic acid on a pre-conditioned SAX cartridge. In the laboratory, vanadium species were separated at different eluent pH levels. VIV was eluted at pH 4 using methanol and tetrabutylammonium hydroxide. VV was eluted at pH 8 using dihydrogen ammonium phosphate. The eluted species were analysed by inductively coupled plasma mass spectrometry (ICP-MS). This method was validated using an inter-analytical method comparison with HPLC-ICP-MS. A Paired t-test revealed that there was no significant difference (probability, P<0.05) between the two methods. VV was found to be predominate species in both sample collection areas (LP: 69 – 100%, BA: ‎33 – 89% of species) over the range of 158.0 – 4748.0μgL−1 in LP and 88.5 – 504.0μgL−1 in BA. VIV was found at higher levels (29.0−301.0μgL−1) in Buenos Aires compared to General San Martin groundwater (4.4 – 161.0μgL−1). The results enhance the potential knowledge of the speciation of vanadium in terms of water quality and human health.

Method for the Determination of Benzene Metabolite t,t-Muconic Acid in Urine by HPLC-UV with an Ion Exclusion Column

The benzene metabolite trans,trans-muconic acid (tt-MA) is widely used as a biological indicator of exposure to this xenobiotic. An analytical method was developed and validated for the determination of urinary tt-MA using solid phase extraction onto a Strata SAX cartridge. The analysis was performed by HPLC with an Aminex HPX-87H ion exclusion column and a UV diode array detector. The sample preparation conditions were optimized using a 24−1 factorial design. Comparison of the slopes of standard analytical curves prepared in aqueous solution and urine showed that the biological matrix suppressed the tt-MA signal by around 50%, so the analytical curves were prepared with tt-MA standard at low concentrations in pooled urine. The analytical curves in the range of 5–500 μg·L−1 showed determination coefficients values (R2) &gt; 0.99 for tt-MA standard in water and R2 &gt; 0.98 for tt-MA standards in pooled urine. The coefficients of variation obtained using seven replicates were lower than 3.6%, and recoveries of tt-MA from solutions containing 5, 25, 50 and 100 μg·L−1 of the analyte were in the range 85%–90%, demonstrating the satisfactory precision and accuracy of the method. The limits of detection and quantification were 0.11 and 0.36 µg ·L−1, respectively. The benefits of this new method developed is the possibility of complete chromatographic peak separation for the determination of tt-MA at baseline, without matrix components’ interference as normally found in the C18 column. This is the first time that this chromatographic column has been used for the analysis of tt-MA in urine.

Quantitation of 5-Methyltetrahydrofolic Acid in Dried Blood Spots and Dried Plasma Spots by Stable Isotope Dilution Assays.

Because of minimal data available on folate analysis in dried matrix spots (DMSs), we combined the advantages of stable isotope dilution assays followed by LC-MS/MS analysis with DMS sampling to develop a reliable method for the quantitation of plasma 5-methyltetrahydrofolic acid in dried blood spots (DBSs) and dried plasma spots (DPSs) as well as for the quantitation of whole blood 5-methyltetrahydrofolic acid in DBSs. We focused on two diagnostically conclusive parameters exhibited by the plasma and whole blood 5-methyltetrahydrofolic acid levels that reflect both temporary and long-term folate status. The method is performed using the [2H4]-labeled isotopologue of the vitamin as the internal standard, and three steps are required for the extraction procedure. Elution of the punched out matrix spots was performed using stabilization buffer including Triton X-100 in a standardized ultrasonication treatment followed by enzymatic digestion (whole blood only) and solid-phase extraction with SAX cartridges. This method is sensitive enough to quantify 27 nmol/L whole blood 5-methyltetrahydrofolic acid in DBSs and 6.3 and 4.4 nmol/L plasma 5-methyltetrahydrofolic acid in DBSs and DPSs, respectively. The unprecedented accurate quantification of plasma 5-methyltetrahydrofolic acid in DBSs was achieved by thermal treatment prior to ultrasonication, inhibiting plasma conjugase activity. Mass screenings are more feasible and easier to facilitate for this method in terms of sample collection and storage compared with conventional clinical sampling for the assessment of folate status.

An enhanced procedure for measuring organic acids and methyl esters in PM&amp;lt;sub&amp;gt;2.5&amp;lt;/sub&amp;gt;

Abstract. A solid-phase extraction (SPE) pretreatment procedure allowing organic acids to be separated from methyl esters in fine aerosol has been developed. The procedure first separates the organic acids from fatty acid methyl esters (FAMEs) and other nonacid organic compounds by aminopropyl-based SPE cartridge and then quantifies them by gas chromatography/mass spectrometry. The procedure prevents the fatty acids and dimethyl phthalate from being overestimated, and so allows us to accurately quantify the C4–C11 dicarboxylic acids (DCAs) and the C8–C30 monocarboxylic acids (MCAs). Results for the extraction of DCAs, MCAs, and AMAs in eluate and FAMEs in effluate by SAX and NH2 SPE cartridges exhibited that the NH2 SPE cartridge gave higher extraction efficiency than the SAX cartridge. The recoveries of analytes ranged from 67.5 to 111.3 %, and the RSD ranged from 0.7 to 10.9 %. The resulting correlations between the aliphatic acids and FAMEs suggest that the FAMEs had sources similar to those of the carboxylic acids, or were formed by esterifying carboxylic acids, or that aliphatic acids were formed by hydrolyzing FAMEs. Through extraction and cleanup using this procedure, 17 aromatic acids in eluate were identified and quantified by gas chromatography/tandem mass spectrometry, including five polycyclic aromatic hydrocarbon (PAH): acids 2-naphthoic, biphenyl-4-carboxylic, 9-oxo-9H-fluorene-1-carboxylic, biphenyl-4,4´-dicarboxylic, and phenanthrene-1-carboxylic acid, plus 1,8-naphthalic anhydride. Correlations between the PAH acids and the dicarboxylic and aromatic acids suggested that the first three acids and 1,8-naphthalic anhydride were secondary atmospheric photochemistry products and the last two mainly primary.

Comparison of Two Analytical Methods for the Determination of Traces of Veterinary Antibiotics and Steroid Hormones in Soil Based on Pressurised Liquid Extraction (PLE) and Quick, Easy, Cheap, Effective, Rugged, Safe (Modified-Quechers) Extraction

Veterinary antibiotics and steroid hormones can be present at low levels in soil. Analytical methodologies are therefore necessary to analyse these compounds at the trace level in such a complex matrix. The goal of this work was to compare Pressurised Liquid Extraction (PLE), which is usually used to extract drugs from soil, and a modified-QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method. Furthermore, several clean-up methods were evaluated. Selective Pressurised Liquid Extraction (SPLE) and Dispersive Solid Phase Extraction (dSPE) used after PLE and QuEChERS, respectively, were tested. These techniques permit a fast and simple purification step. SPE, which is frequently used, was also evaluated. To perform this comparison, both recoveries and matrix effects were compared and the analyses were performed using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). SPLE and dSPE did not significantly decrease matrix effects. A tandem SPE using SAX and Strata-X cartridges offered the best efficiency. Regarding the comparison between PLE and QuEChERS, the modified-QuEChERS led to better recoveries for certain substances. No significant differences were noted in term of matrix effects. Therefore, the modified-QuEChERS method is recommended.

Determination of alcohol sulfates and alcohol ethoxysulfates in wastewater samples by liquid chromatography tandem mass spectrometry

The work develops a liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for the identification and quantification of alkyl homologues of alcohol sulfates (AS) and ethoxymers of alcohol ethoxysulfates (AES) in wastewaters. The method involves isolation and preconcentration of the analytes from the samples using solid-phase extraction (SPE) with SAX cartridges prior to their quantification by LC–MS/MS with electrospray (ESI) interface in negative mode. The limits of detection (LOD) found were 0.1μgL−1 for AS, and ranged from 0.2 to 0.5μgL−1 for AES. The limits of quantification (LOQ) ranged from 0.3 to 0.4μgL−1 for AS, and from 0.5 to 1.5μgL−1 for AES. The accuracy of the method was studied in terms of trueness and precision. Trueness was evaluated by using a spike recovery assay with spiked blank samples. Recoveries ranged from 96.0 to 102.8% for AS and from 93.4 to 105.1% for AES. Precision (in terms of inter- and intra-day RSD) was lower than 5% for AS and AES. Finally, the method was satisfactorily applied to the quantification of compounds in wastewater samples collected from a wastewater treatment plant (WWTP) located in the city of Granada (Spain). Data obtained showed that AS are present in concentration levels from 0.7 to 39.4μgL−1 in influent waters and from 1.1 to 8.1μgL−1 in effluent waters. As for AES, the amounts (sum of ethoxymers) found ranged from 0.7 to 24.0μgL−1 in influents and from 1.9 to 2.5μgL−1 in effluents.

A fast chemoenzymatic synthesis of [11C]-N5,N10-methylenetetrahydrofolate as a potential PET tracer for proliferating cells

Thymidylate synthase and folate receptors are well-developed targets of cancer therapy. Discovery of a simple and fast method for the conversion of 11CH3Ito[11C]-formaldehyde (11CH2O) encouraged us to label the co-factor of this enzyme. Preliminary studies conducted on cell lines have demonstrated a preferential uptake of [11-14C]-(R)-N5,N10-methylene-5,6,7,8-tetrahydrofolate (14CH2H4folate) by cancerous cell vs. normal cells from the same organ (Saeed M., Sheff D. and Kohen A. Novel positron emission tomography tracer distinguishes normal from cancerous cells. J Biol Chem 2011;286:33872-33878), pointing out 11CH2H4folate as a positron emission tomography (PET) tracer for cancer imaging. Herein we report the synthesis of 11CH2H4folate, which may serve as a potential PET tracer. In a remotely controlled module, methyl iodide (11CH3I) was bubbled into a reaction vial containing trimethylamine N-oxide in N,N-Dimethylformamide (DMF) and heated to 70°C for 2 min. Formaldehyde (11CH2O) formed after the completion of reaction was then mixed with a solution of freshly prepared tetrahydrofolate (H4folate) by using a fast chemoenzymatic approach to accomplish synthesis of 11CH2H4folate. Purification of the product was carried out by loading the crude reaction mixture on a SAX cartridge, washing with water to remove unbound impurities and finally eluting with a saline solution. The synthesis and purification of 11CH2H4folate were completed within 5 min. High-performance liquid chromatography analysis of the product after SAX purification indicates that more than 90% of the radioactivity that was retained on the SAX cartridge was in 11CH2H4folate, with minor (<10%) radioactivity due to unreacted 11CH2O. We present a fast (∼5 min) synthesis and purification of 11CH2H4folate as a potential PET tracer. The final product is received in physiologically compatible buffer (100 mM sodium phosphate, pH 7.0 containing 500 mM NaCl) and ready for use in vivo.

LC-MS/MSによる畜水産食品中のクロメプロップおよびクロメプロップ酸分析法の開発

A method using liquid chromatography with tandem mass spectrometry has been developed for the determination of clomeprop and its metabolite clomeprop acid in livestock and seafood products. Clomeprop and clomeprop acid were extracted with acetone-n-hexane mixture under acidic conditions, and were defatted by liquid-liquid separation using acetonitrile and n-hexane, followed cleanup with SAX and PSA cartridges. The average recoveries from 10 kinds of food (bovine muscle, bovine fat, bovine liver, milk, yellowtail, salmon, eel, fresh water clam, egg and honey) spiked at the level of the MRLs or at uniform limits (0.01 ppm) were in the range of 81-97% for clomeprop and 93-101% for clomeprop acid. Repeatability was in the range of 2.1-14% for clomeprop and 1.3-4.0% for clomeprop acid. The quantitation limits were 0.002 mg/kg for clomeprop and 0.00154 mg/kg (0.002 mg/kg as clomeprop) for clomeprop acid.

Development of a high-performance liquid chromatography method for the simultaneous quantification of four organoarsenic compounds in the feeds of swine and chicken

A high-performance liquid chromatography (HPLC) method with UV detection was developed for the simultaneous determination of arsanilic acid, roxarsone, nitarsone, and carbarsone in the feeds of swine and chicken. Feed samples were extracted with methanol/1% acetic acid (90:10, v/v) in an ultrasonic bath and the protein was precipitated with 2% Cu 2SO 4. The samples were further purified by solid phase extraction (SPE) on SAX cartridges. Separation was performed on a Zorbax SB-Aq C18 HPLC column using an isocratic procedure with methanol and 1% acetic acid (3:97, v/v) at a flow-rate of 0.7 mL min −1, and the UV detector was set at a wavelength of 260 nm. The recoveries of organoarsenic compounds spiked at levels of 2, 20 and 200 μg g −1 ranged from 81.2% to 91.3%; the inter-day relative standard deviation values were less than 7.0%. The limits of quantification for four organoarsenic compounds were 1.0–2.0 μg g −1. This simple and fast method could be applied to the determination of multi-residues of organic arsenic compounds in animal feeds.

Comparison of Various Preparation Methods for Determination of Organic Acids in Fruit Vinegars with a Simple Ion-Exclusion Liquid Chromatography

An ion-exclusion liquid chromatography with mobile phase 0.005 mol L−1 H2SO4 and step flow rate gradient (0.2 mL min−1 in the first 40 min and 0.5 mL min−1 from 41 to 60 min) was used to determine 20 organic acids simultaneously at 17 °C within 51 min. The peak resolutions (Rs) were 0.45∼3.02 and separation factors (α) were all higher than 1. Impurities in fruit vinegar executed with direct injection or C18 cartridge clean-up for analysis would influence the glutaric and oxalic acid measurement; however, SAX cartridge extraction could reduce the interferences (organic acid recoveries were 93.93∼99.98%). Acetic, ascorbic, citric, malic, and malonic acids were the major organic acids in fruit vinegars (apple, apple sparkling, plum, cranberry, and grape).

Analysis of Metribuzin and Its Metabolites in Livestock Products and Seafoods by Liquid Chromatography-Tandem Mass Spectrometry

A method for simultaneous determination of metribuzin (MET) and three metribuzin metabolites in livestock products and seafoods by liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed. MET and its metabolites were extracted from a sample with acetonitrile, followed by InertSepC18 and BondElut SAX cartridge cleanup. The LC separation was performed on a C18 column using 0.01 mol/L ammonium formate-acetonitrile-methanol (70 :21 : 9) as the mobile phase and MS detection with both positive and negative ion electrospray ionization. The mean recoveries from 10 livestock products and seafoods were generally >60%, and the relative standard deviations were <20%

Solid Phase Extraction and High Performance Liquid Chromatography for Determination of Glyoxylic Acid in a Selective Oxidation Reaction

Currently, the development of a new method for the analysis of glyoxylic acid in selective oxidation of glyoxal system has become a key subject in its new industrial process development. Since solid phase extraction (SPE) could isolate and concentrate desired analytes from complex matrices, in this paper we tested the possibility of coupling SPE technique with HPLC for simultaneous determination of glyoxylic acid, formic acid, and oxalic acid in this complex chemical reaction system. Results demonstrated that the developed method could be successfully applied to this system, after samples were passed through SAX cartridges and yielded recoveries from 96.7% to 103%. The limits of detection were 2.6 × 10−6, 3.6 × 10−6, and 3.5 × 10−7 mol L−1, respectively; and their linear ranges between 1 × 10−6 and 1 × 10−2 mol L−1.

HPLC–MS analysis of iodotyrosines produced by sample hydrolysis: A simple method for monitoring iodinated casein in feed premixes

A new and simple HPLC–MS method was developed for monitoring iodinated casein in feed premixes. In this method, feed premixes were hydrolyzed, and the iodotyrosines thus released were analyzed. Sample pretreatment included precipitation of transition metals ions with Na 2S, hydrolysis with sodium hydroxide, and cleaning up with an Oasis SAX cartridge. Gradient elution was carried out on a C 18 column with water (containing 0.1% formic acid) and acetonitrile. Ion detection was performed using ESI positive SIM at m/ z 262, 308, 388, and 434. Iodinated casein levels were monitored by qualitative analysis of the iodotyrosines released upon sample hydrolysis and by quantifying the 3,5-diiodotyrosine released. The validation data demonstrated that the method was selective and sensitive (≤0.2 mg g −1) for iodinated casein and had acceptable accuracy (recoveries: 81.3–106.7%) and precision (RSD: 1.7–16.0%).

Purification of gangliosides by liquid-liquid partition chromatography

A liquid-liquid partition chromatographic technique was applied to separate amphiphilic glycolipids. A two-phase solvent system composed of n-butanol-t-butyl methyl ether-acetonitrile-water at a volume ratio of 3:1:1:5 was found to be suitable for separating the gangliosides from total lipids extracted from rat brain by liquid-liquid partition chromatographic systems, namely centrifugal partition chromatography (CPC) and high-speed counter-current chromatography. GM1 could be separated rapidly by using the upper phase as stationary phase for both systems. Moreover, various kinds of gangliosides (GM1, GD1a, GD1b, GT1b) could be separated individually by using the lower phase as stationary phase by CPC. The sample can be recovered without loss by these systems.

Influência do hábito de fumar na excreção urinária do ácido trans, trans-mucônico

O hábito de fumar é considerado a maior fonte individual de benzeno para indivíduos não expostos ocupacionalmente e, em vista de sua comprovada carcinogenicidade, este solvente representa sério risco, tanto para a população em geral quanto para os trabalhadores. Um dos bioindicadores mais utilizados para avaliar a exposição benzênica é o ácido trans,trans-mucônico (AttM) em urina, o qual apresenta sensibilidade suficiente para a monitorização biológica da exposição a baixos níveis de benzeno. O objetivo deste trabalho foi verificar a influência do hábito de fumar na excreção urinária do AttM. A identificação e quantificação do analito foram realizadas por meio de cromatografia líquida de alta eficiência, utilizando-se coluna de fase reversa e detecção a 264 nm, após prévia extração em fase sólida. O método foi previamente validado demonstrando linearidade, no intervalo de 0,006 a 10,0 µg mL-1 (r= 0,996), limites de detecção e de quantificação de, respectivamente, 1,41 x 10-3 µg mL-1 e 6,0 x 10-3 µg mL-1 e coeficientes de variação de 1,79 a 2,91% (precisão intracorridas) e, de 3,53 a 18,37% (precisão intercorridas). Foi observada correlação positiva entre a excreção do AttM e o hábito de fumar, comparando o grupo de fumantes e o de não-fumantes (p= 0,005388). Contudo, o número de cigarros fumados por dia não influenciou significativamente a excreção deste produto de biotransformação do benzeno.

Rapid Separation of Gangliosides Using Strong Anion Exchanger Cartridges

A method utilizing strong anion exchanger cartridges (InertSep SAX) was developed to separate gangliosides. Total lipids extracted from rat brain is able to be rapidly separated into neutral and acidic lipids rapidly. Neutral lipids were passed through the SAX cartridge while acidic lipids adsorbed onto the cartridge and were eluted by chloroform/methanol/4.0 M aqueous ammonium acetate (5:10:1, by volume). Moreover, various kinds of gangliosides (GM1, GD1a, GD1b, GT1b) were separated individually according to their characteristics by elution with increasing concentration of ammnonium acetate (0 - 4.0 M). The gangliosides yield of this procedure was higher than 95%.

Fumonisin production in rice cultures of Fusarium verticillioides under different incubation conditions using an optimized analytical method

Fumonisin B 1 (FB 1) and fumonisin B 2 (FB 2) are the main members of a family of mycotoxins produced by various fungal species belonging to the Gibberella fujikuroi complex. The present work shows the results of a comparative study of various clean-up and derivatization procedures for analysis of fumonisins in rice cultures. Fumonisins were extracted from rice with acetonitrile/water (50/50, v/v). For clean-up, three solid-phase extraction procedures were assayed (C 18 cartridge, SAX cartridge, and a combination of both). Two reagents ( o-phthaldialdehyde and 4-fluoro-7-nitro-benzofurazan) were studied comparatively for formation of fluorescent derivatives. The separation was carried out by LC using a fluorescence detector. The best procedure for analysis of fumonisins in rice involved clean-up with C 18 cartridge and derivatization with o-phthaldialdehyde. The limit of detection was 0.010 mg kg −1 for both toxins. In the 10–500 mg kg −1 spiking level range, the recovery rates for FB 1 and FB 2 in rice varied from 94.6% to 103.6% and from 96.3% to 101.9%, respectively. The optimized analytical method for determination of fumonisins in rice was applied to the study of FB 1 and FB 2 production by four isolates of the G. fujikuroi species complex in rice cultures carried out at different temperatures and water activities to establish the influence of strain and environmental conditions on fumonisin production in this cereal. In general, fumonisin production was the highest at 20 °C and lowest at 37 °C. Four of the five assayed water activity ( a w) values (0.97, 0.98, 0.99, and 1.0) did not affect significantly fumonisin accumulation but fumonisins were not detected in cultures when a w was 0.96.