Small Volume Of Methanol Research Articles

Determination of phenolic acids and flavonoids from Myrciaria cauliflora edible part employing vortex-assisted matrix solid-phase dispersion (VA-MSPD) and UHPLC-MS/MS

In the present study, for the first time, vortex-assisted matrix solid-phase dispersion (VA-MSPD) is used to determine phenolic compounds in the edible part of Myrciaria cauliflora combined with ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) analysis. Under the optimized extraction conditions, the VA-MSPD method used a small amount of sample (25 mg), C18 (100 mg) as a solid support, a small volume of methanol (6 mL) as elution solvent and reduced time of grinding and vortex agitation (90 s). The proposed method showed good linearity (r ≥ 0.99) for all compounds, with detection limits in the range of 0.9˗99 μg kg−1. The matrix effect was between ˗0.8 and +52 %. This method allowed the quantification of four phenolic acids (4-hydroxybenzoic acid, gallic acid, p-coumaric acid and ellagic acid) and four flavonoids (myricetin, (+)-catechin, naringenin and quercetin) in M. cauliflora edible part harvested in different years. Ellagic acid was found with the highest abundance ranging from 470 to 709 mg kg−1. These results support the high potential of VA-MSPD to be applied in the determination of the phenolic compounds of fruit matrices, as well as, requiring a low solvent volume, a small amount of sample and solid support and features easy handling and short analysis time.

Novel deep eutectic solvent-based ultrasounds-assisted dispersive liquid-liquid microextraction with solidification of the aqueous phase for HPLC-UV determination of aromatic amines in environmental samples.

In this study, a green and efficient sample preparation method using a deep eutectic solvent-based ultrasounds-assisted dispersive liquid–liquid microextraction with solidification of the aqueous phase (DES-UA-DLLME-SAP) followed by HPLC-UV was developed for preconcentration and determination of aromatic amines in aqueous environmental samples. In the proposed method, a novel deep eutectic solvent (DES) characterized by low density was prepared by mixing trihexyl(tetradecyl)phosphonium chloride and decanol at a molar ratio of 1:2. Ultrasounds were used to disperse the extractant in the aqueous phase of the sample. Then, the phases were separated by centrifugation, after which the aqueous phase was frozen and the surface DES phase was dissolved in a small volume of methanol before injection into the chromatograph. Various factors, including the selection of extractant and its volume, pH of the sample, duration of ultrasounds treatment, the time and rate of centrifugation and salt addition, were investigated and optimized. Under optimal conditions (40 µL of DES, pH = 12, 60 s of ultrasound use, 10 min/4500 rpm of centrifugation, 40 mg of NaCl), the proposed method allowed to achieve good precision (n = 6) between 2.9 and 6.2% at 0.4, 5.0 and 40.0 ng mL−1 levels, respectively. The preconcentration factors were equal to 119, 116 and 121 for 2-chloroaniline, 4-chloroaniline and 1-naphthylamine, respectively. The limits of detection were equal to 0.07 ng mL−1 for 2-chloroaniline, 0.11 ng mL−1 for 4-chloroaniline and 0.08 ng mL−1 for 1-naphthylamine. The proposed method was successfully applied for determination of aromatic amines in aqueous environmental samples with a good recoveries in the range of 85.1–99.9%

Efficient removal of perfluorinated compounds from water using a regenerable magnetic activated carbon

Adsorption by powder activated carbon (PAC) is recognized as an efficient method for the removal of perfluorinated compounds (PFCs) in water, while the poor separation of spent PAC makes it difficult for further regeneration, increasing the treatment cost significantly. In this study, an ultrafine magnetic activated carbon (MAC) consisting of Fe3O4 and PAC was prepared by ball milling to remove PFCs from water efficiently. Increasing the percentage of Fe3O4 and balling milling time decreased its adsorption capacity for perfluoroctane sulfonate (PFOS), whereas increased the magnetic separation property to some degree. The optimized MAC was prepared with a Fe3O4 to PAC mass ratio of 1:3 after ball milling for 2 h, and the adsorption equilibriums of all the four PFCs on the optimal MAC were reached within less than 2 h, with the adsorption capacities of 1.63, 0.90, 0.33 and 0.21 mmol/g for PFOS, perfluorooctanoic acid (PFOA), perfluorohexane sulfonate (PFHxS) and perfluorobutane sulfonate (PFBS), respectively. Increasing the solution pH hindered the adsorption of PFOS significantly when the pH was less than the zero potential point (around 6) of the MAC, due to the decreased electrostatic attraction. The spent MAC could be easily separated with a magnet and regenerated by a small volume of methanol, and the regenerated MAC could be reused for more than 5 time and remain stable adsorption capacity for PFOS after 3 cycles. This study provides useful insights into the removal of PFCs by separable magnetic PAC in wastewater.

Magnetically responsive textile for a new preconcentration procedure: Magnetic textile solid phase extraction

A new preconcentration procedure named “Magnetic textile solid phase extraction” was developed. A piece of nonwoven textile (fabric) was used for the immobilization of copper phthalocyanine dye and employed for the adsorption of crystal violet and safranin O from large volumes of sample. The bound dye was eluted into small volume of methanol. The limit of detection and limit of quantification values for safranin O were 2.66 µg/L and 8.87 µg/L, while for crystal violet these values were 2.17 µg/L and 7.23 µg/L, respectively. Linearity in the range 5–100 µg/L was observed. In order to prepare magnetically responsive adsorbent, an iron-based standard staple was inserted in the textile material using an office stapler. The developed procedure can be easily adapted for the detection of large variety of analytes in biochemistry, biotechnology, environmental technology, and forensic analysis.

Low-parachor solvents extraction and thermostated micro-thin-layer chromatography separation for fast screening and classification of spirulina from pharmaceutical formulations and food samples

The goal of this paper is to demonstrate the separation and detection capability of eco-friendly micro-TLC technique for the classification of spirulina and selected herbs from pharmaceutical and food products. Target compounds were extracted using relatively low-parachor liquids. A number of the spirulina samples which originated from pharmaceutical formulations and food products, were isolated using a simple one step extraction with small volume of methanol, acetone or tetrahydrofuran. Herb samples rich in chlorophyll dyes were analyzed as reference materials. Quantitative data derived from micro-plates under visible light conditions and after iodine staining were explored using chemometrics tools including cluster analysis and principal components analysis. Using this method we could easily distinguish genuine spirulina and non-spirulina samples as well as fresh from expired commercial products and furthermore, we could identify some biodegradation peaks appearing on micro-TLC profiles. This methodology can be applied as a fast screening or fingerprinting tool for the classification of genuine spirulina and herb samples and in particular may be used commercially for the rapid quality control screening of products. Furthermore, this approach allows low-cost fractionation of target substances including cyanobacteria pigments in raw biological or environmental samples for preliminary chemotaxonomic investigations. Due to the low consumption of the mobile phase (usually less than 1 mL per run), this method can be considered as environmentally friendly analytical tool, which may be an alternative for fingerprinting protocols based on HPLC machines and simple separation systems involving planar micro-fluidic or micro-chip devices.

Simple, high throughput ultra-high performance liquid chromatography/tandem mass spectrometry trace analysis of perfluorinated alkylated substances in food of animal origin: Milk and fish

The present study documents development and validation of a novel approach for determination of 23 perfluorinated alkylated substances (PFASs) in food of animal origin represented by milk and fish. The list of target analytes comprises four classes of PFASs, both ionic and non-ionic: 11 perfluorocarboxylic acids (PFCAs), 4 perfluorosulphonic acids (PFSAs), 5 perfluorosulphonamides (FOSAs) and 3 perfluorophosphonic acids (PFPAs). Fast sample preparation procedure is based on an extraction of target analytes with acetonitrile (MeCN) and their transfer (supported by inorganic salts and acidification) into the organic phase. Removing of matrix co-extracts by a simple dispersive solid phase extraction (SPE) employing ENVI-Carb and C18 sorbents is followed by an efficient sample pre-concentration performed by acetonitrile evaporation and subsequent dilution of residue in a small volume of methanol (matrix equivalent in the final extracts was 16 and 8 g mL −1, for milk and fish respectively). Using modern instrumentation consisting of ultra-high performance liquid chromatography (UHPLC) hyphenated with a tandem mass spectrometer (MS/MS), limits of quantification (LOQs) as low as 0.001–0.006 μg kg −1 for milk and 0.002–0.013 μg kg −1 for fish can be achieved. Under these conditions, a wide spectrum of PFASs, including minor representatives, can be determined which enables collecting data required for human exposure studies. The pilot study employing the new method for examination of milk and canned fish samples was realized. Whereas in majority of canned fish products a wide spectrum of PFCAs, perfluorooctanesulphonic acid (PFOS) and perfluoro-1-octanesulphonamide (PFOSA) was detected, only in a few milk samples very low concentrations (LOQ levels) of PFOS and perfluorooctansulphonic acid (PFDS) were found.

Activation of MAPK Kinase 9 Induces Ethylene and Camalexin Biosynthesis and Enhances Sensitivity to Salt Stress in Arabidopsis

Mitogen-activated protein kinase (MAPK) cascades play important roles in regulating plant growth, development, and responses to various environmental stimuli. We demonstrate that MKK9, an MKK, is an upstream activator of the MPKs MPK3 and MPK6 both in vitro and in planta. Expression of active MKK9 protein in transgenic plants induces the synthesis of ethylene and camalexin through the activation of the endogenous MPK3 and MPK6 kinases. As a consequence, transcription of multiple genes responsible for ethylene biosynthesis, ethylene responses, and camalexin biosynthesis is coordinately up-regulated. The activation of MKK9 inhibits hypocotyl elongation in the etiolated seedlings. MKK9-mediated effects on hypocotyl elongation were blocked by the ethylene biosynthesis inhibitor, aminoethoxyvinylglycine, and ethylene receptor antagonist, Ag(+). Expression of active MKK9 protein enhances the sensitivity of transgenic seedlings to salt stress, whereas loss of MKK9 activity reduces salt sensitivity indicating a role for MKK9 in the salt stress response. The results reported here reveal that the MKK9-MPK3/MPK6 cascade participates in the regulation of the biosynthesis of ethylene and camalexin and may be an important axis in the stress responses of Arabidopsis.

Combined use of supported liquid membrane and solid‐phase extraction to enhance selectivity and sensitivity in capillary electrophoresis for the determination of ochratoxin A in wine

This paper proposes a novel strategy to enhance selectivity and sensitivity in CE, using supported liquid membrane (SLM) and off-line SPE simultaneously. The determination of ochratoxin A (OA) in wine has been used to demonstrate the potential of this methodology. In the SLM step, the donor phase (either a 20 mL volume of a standard solution at pH 1 or a wine sample at pH 8) was placed in a vial, where a micromembrane extraction unit accommodating the acceptor phase (1 mL water, pH 11) in its lumen was immersed. The SLM was constructed by impregnating a porous Fluoropore Teflon (PTFE) membrane with a water-immiscible organic solvent (octanol). In the off-line SPE step, the nonpolar sorbent (C-18, 4 mg) selectively retained the target ochratoxin, enabling small volumes of acceptor phase (1 mL) to be introduced. The captured analytes were eluted in a small volume of methanol (0.1 mL). This procedure resulted in sample cleanup and concentration enhancement. The method was evaluated for accuracy and precision, and its RSD found to be 5%. The LODs for OA in the standard solutions and wine samples were 0.5 and 30 microg/L, respectively. The results obtained demonstrate that SLM combined with off-line is a good alternative to the use of immunoaffinity columns prior to CE analysis.

Determination of Diphenylarsinic Acid in Plants and Biological Samples by HPLC/MS/MS Using a Stable Isotope Labeled Compound

A method for the determination of diphenylarsinic acid (DPAA) in plants and biological samples by high-performance liquid chromatography-tandem mass spectrometry (HPLC/MS/MS) using a stable isotope labeled compound as an internal standard is described. After the sample was decomposed in 2 M sodium hydroxide by heating, an internal standard (DPAA-13C12) was added to the solution. The decomposed solution was shaked with a mixture of chloroform and n -hexane (1 : 4). After centrifugal separation, the organic layer was discarded. The aqueous layer was then adjusted to ca. 0.5 M hydrochloric acid solution, and cysteine and potassium iodide were added in order to extract DPAA efficiently in the chloroform. Extraction was carried out twice, and the chloroform layers were combined and evaporated. The extracts were dissolved in methanol or water in case of plants. When a colored solution was obtained, it was purified by an Oasis HLB solid-phase cartridge. In biological materials, the extracts were dissolved in a small volume of methanol, and then 0.5% nitric acid solution was added. When the mixture got cloudy, it was passed through a 0.20 μm of membranfilter. DPAA in the final solution was analyzed by HPLC/MS/MS. HPLC separation was performed with an ODS column using a linear gradient elution of an acetonitrile-water system containing 0.1% trifluoroacetic acid as the mobile phase. MS/MS was used in multiple reaction monitoring (MRM), employing electrospray ionization. The proposed method could determine DPAA in plants and biological samples with an average recovery of 99.4%. The coefficient of variation was as low as 6%. The calibration curve was linear between 0 and 30 ng/ml.

In-Loop Solid-Phase Microextraction Coupled with High Performance Liquid Chromatography

A new in-loop solid-phase microextraction coupled with high performance liquid chromatography was developed for a fast and easy on line extraction, pre-concentration and LC analysis of moderately polar compounds from non-polar solvents. The inner surface of a long and small bore aluminum tube was electrochemically coated by Al2O3 and used as a new in-tube SPME device which can be also replaced to the injection loop in LC to achieve automated in-loop SPME-LC analysis. Large volume of n-hexane containing trace amounts of phenol and biphenyl was passed through the loop. The analytes were then desorbed by a small volume of methanol and introduced into chromatographic column. This technique was successfully used to analyses of different groups of moderately polar compounds. In this work, phenol and biphenyl were selected as the model compounds. Effect of various parameters affecting in-loop solid-phase microextraction and chromatographic procedure were investigated. Under the optimum conditions the calibration graph were linear in the range of 10–1000 ng mL−1 and 50–1500 ng mL−1 the detection limits were 2.5 and 8 ng mL−1 for phenol and biphenyl, respectively. The relative standard deviations (RSDs) were < 2.4 and < 4.9% for phenol and biphenyl respectively. Concentration factor obtained for these compounds were more than 100 folds. The prepared SPME capillary tube (loop) is sturdy, inexpensive, and durable, and can be easily coupled with LC.

Extraction and Separation of Cationic Surfactants from River Sediments: Application to a Spectrophotometric Determination of Cationic Surfactant in an Aquatic Environment Using Membrane Filters

The quantitative extraction of cationic surfactant (CS+) in river sediments was studied. Further, the developed method was applied to the spectrophotometric determination of CS+ in urban river sediment samples by solid-phase extraction with membranes. A mixture of methanol and hydrochloric acid was proposed as an eluent. Dried sediment was digested in the eluent under ultrasonic irradiation. After elution, the eluent was evaporated to almost dryness. The residue was dissolved in a small volume of methanol and diluted to a certain volume with water. The pH of the solution was adjusted to 4-5 to separate iron and some other metals as precipitates of hydroxides. The solution was passed through two-piled membranes: first glass-fiber and then polytetrafluoroethylene (PTFE) membranes. A small volume of methanol was passed through the membranes to elute any CS+ retaining on the membranes. After passing the methanol solution through a cationic exchange resin column, the retained CS+ was eluted with methanol containing a high concentration of sodium chloride. Water, Bromophenol Blue (BPB) and hydrochloric acid were added to the solution. The solution was passed through a mixed cellulose ester membrane filter to retain an ion associate of CS+.BPB-. The retained ion associate was dissolved in a small volume of N,N-dimethylformamide together with the membrane filter, followed by the addition of triethanolamine to make the solution alkaline. The absorbance due to BPB2- was measured at 603 nm against a reagent blank. This method was applied to the determination of CS+ in river water and sediment. A cationic surfactant in sediments at 10(-5) mol kg-1 levels was detected with satisfactory precision. It was found that CS+ was about 500-fold enriched in the sediment from water at the place where domestic wastewater was discharged.

Determination of Ag, Te, U and Au in waters and in biological samples by FI–ICP-MS following on-line preconcentration

An on-line preconcentration system for Au, Ag, Te and U, using solenoid valves, a mini-column filled with C18 immobilized on silica to retain the complexes formed with the ammonium salt of O, O-diethyl dithiophosphoric acid and elution with methanol is proposed. All parameters of the preconcentration, such as sample flow rate, concentration of the complexing agent, acid nature and concentration and elution were optimized. Due to the difficulty of finding compromising conditions for all analytes, they were determined individually. Detections limits ranged from 0.05 to 2.24 pg ml −1 for U and Te, respectively, while the preconcentration factors ranged from 2.6 to 180 for U and Te, respectively. The precision was adequate for the low measured concentrations, with R.S.D. below 10%. Accuracy was assured by the analysis of standard reference enriched water, sea and riverine waters, milk powder, apple leaves and urine, after microwave-assisted digestion of the last three materials. The relatively small volume of methanol, diluted to 1+1, introduced into a conventional nebulizer, minimizes the problems associated with the introduction of organic solvent in the plasma.

Trace metal analysis of natural waters and biological samples by axial inductively coupled plasma time of flight mass spectrometry (ICP-TOFMS) with flow injection on-line adsorption preconcentration using a knotted reactor

Traces of Cu, Ni, Sb, Co, Ag, Cd, Mo, In and Pb in biological materials and natural water samples were determined by axial inductively coupled plasma time-of-flight mass spectrometry (ICP-TOFMS) with ultrasonic nebulization after flow injection (FI) on-line sorption/preconcentration in a knotted reactor (KR). The ability to collect complete mass spectra at a high frequency (more than 20 000 complete mass spectra per second) makes ICP-TOFMS nearly ideal for the detection of FI (transient) signals. The analytes were complexed with ammonium pyrrolidinedithiocarbamate (APDC) from acidic solutions in the flow system and sorbed onto the KR. The relatively small volume of methanol used as eluent, along with the employment of an ultrasonic nebulizer (USN) with membrane desolvation, minimizes the problems produced by the introduction of organic solvents into the plasma. Using a preconcentration time of 120 s and a sample flow rate of 2.8 ml min−1 an enhancement factor of 5 to 70 was achieved. The detection limits (3σ) varied from 0.5 ng l−1 for Sb to 26 ng l−1 for Pb. The precision (RSD) for 11 replicate determinations of 0.2 µg l−1 of each analyte was better than 5%. The accuracy of the method was demonstrated by the analysis of four certified reference materials: a synthetic freshwater (NIST SRM 1643d), a natural filtered coastal water (NRCC CASS-3) and two biological materials (BCR CRM 422 Cod muscle and BCR CRM 278R Mussel tissue) and by recovery measurements on spiked samples.

Determination of heavy metals by inductively coupled plasma mass spectrometry after on-line separation and preconcentration

A method for the determination of Cu, As, Se, Cd, In, Hg, Tl, Pb and Bi in waters and in biological materials by inductively coupled plasma mass spectrometry, after an on-line separation, is described. The matrix separation and analyte preconcentration is accomplished by retention of the analytes complexed with the ammonium salt of O,O-diethyl dithiophosphoric acid in a HNO 3 solution on C 18 immobilized on silica in a minicolumn. Methanol, as eluent, is introduced in the conventional pneumatic nebulizer of the instrument. In order to use the best compromise conditions, concerning the ligand and acid concentrations, the analytes were determined in two separate groups. The enrichment factors were in the range from 5 to 61, depending on the analyte. The limits of detection varied from 0.43 ng L −1 for Bi to 33 ng L −1 for Cu. The sample consumption is only 2.3 mL for each group and the sampling frequency is 21 h −1. The accuracy was tested by analysing five certified reference materials: water, riverine water, urine, bovine muscle and bovine liver. The agreement between obtained and certified concentrations was very good, except for As. The relatively small volume of methanol, used as eluent, minimizes the problems produced by the introduction of organic solvent into the plasma.

Preliminary Evidence for Phytoalexin Production by Eucalyptus urophylla Leaves as a Response to Inoculation with the Incompatible Pathogen Acidovorax avenae pv. avenae

AbstractLeaves of eucalyptus (Eucalyptus urophylla) were infiltrated with a cell suspension of the incompatible pathogen Acidovorax avenae pv. avenae and showed a typical hypersensitive response within 24h. Necrotic leaf areas were excised, vacuum infiltrated with 40% ethanol and left under continuous agitation at room temperature for 24h. The diffusate was concentrated, partitioned with ethyl‐acetate, concentrated to dryness and resuspended in a small volume of methanol. The biological activity of extracts was evaluated by an agar diffusion method against noncompatible bacteria (A. avenae pv. avenae and Xanthomonas axonopodis pv. manihotis) and fungi (Penicillium sp. and Aspergillus sp.). Inhibition haloes, when present, were always larger in extracts from leaves infiltrated with the incompatible bacterium than the water control. Thin layer chromatography resolution of crude extracts from leaves infiltrated with both incompatible pathogen cell suspension and water, followed by bioautography with Thieleviopsis paradoxa, consistently rendered, in both situations, a large, diffuse inhibition halo near the origin, assumed to be due to preformed antimicrobial substances. However, extracts from leaves infiltrated with the living cells of the incompatible pathogen gave rise to a smaller, second inhibition halo, near the front, that was interpreted as being one or several phytoalexins.

Determination of Small Dialkyl Organophosphonates at Microgram/L Concentrations in Contaminated Groundwaters Using Multiple Extraction Membrane Disks

Di-isopropyl methylphosphonate (DIMP) and dimethyl methylphosphonate (DMMP), which are manufacturing by-products of. and surrogate compounds for, the nerve agents Sarin (GB) and VX, respectively, are readily quantitated at microgram per liter concentrations in contaminated groundwaters. Aqueous samples (typically 1 L) are first fortified with triethylphosphate (TEP) as a surrogate, then passed through a “sandwiched” set of three preconditioned extraction disks consisting of the following (in filtration order): (a) glass fiber filter, to remove unwanted particulate matter; (b) C18-based extraction disk, to collect DIMP; and (c) carbon-based extraction disk, to collect DMMP. The glass fiber filter is discarded; the two extraction disks are dried and extracted with a small volume of methanol. After the extract is fortified with diethyl ethylphosphonate (DEEP) internal standard, it is analyzed using a gas chromatograph equipped with a nitrogen-phosphorus detector (NPD). Quantitation of DMMP, DIMP, and TEP is performed using the method of internal standards. The procedure was used to obtain statistically-unbiased reporting limits for a “regulatory” criterion of 0.39 μg/L and a “pump and treat” criterion of 2 μg/L for both analytes. Two standardized protocols were used to validate a detection limit of 0.20 μg/L for DMMP and 0.48 μg/L for DIMP when the regulatory criterion was used as the “target concentration.” When the “pump and treat” criterion was used as the “target concentration,” the detection limits for both DMMP and DIMP were both 2 μg/L using the same protocols as for the “regulatory” criterion. The method recovery is approximately 40–50%, based on synthetic groundwaters containing between 0.2–50 μg/L of each analyte. DIMP and DMMP are cleanly resolved from each other, the internal standard, the surrogate, and the potential interference trimethylphosphate (TMP).

Performance characteristics of reversed-phase bonded silica cartridges for serum bile acid extraction.

The quantitative extraction of bile acids and their conjugates from serum was investigated using different commercially available reversed-phase bonded silica cartridges. Serum was diluted with 0.1 M sodium hydroxide or 0.5 M triethylamine sulphate, pH 7.0, and heated at 64 degrees C for 20-30 min prior to application to the cartridge. Bile acids were adsorbed to the bonded silica particles, and recovered by elution with a small volume of methanol. Dilution of serum with triethylamine sulphate gave quantitative extraction of bile acids from serum using Bond-Elut C18 cartridges, but the milder conditions of the applied sample compared with dilution with sodium hydroxide permitted re-use of the cartridges with no loss in performance, and gave relatively clean extracts. Large variations in the recovery of bile acids were observed using sorbents from different manufacturers. These studies highlight the need to evaluate critically the performance characteristics of solid-phase cartridges when the manufacturer or batch lot is changed.

Supercritical fluid extraction as a sample preparation technique for the direct isolation of drugs from plasma prior to analysis

Supercritical carbon dioxide was used for the direct extraction of drugs from plasma prior to analysis. The supercritical fluid was directly passed through plasma samples spiked with either a neutral (flavone) or an acidic (ketorolac) drug. The addition of an antifoam agent to the plasma prior to extraction was required to avoid restrictor plugging caused by denaturation of the plasma proteins by the supercritical fluid. The effluent from the extraction cell was bubbled through a small volume of methanol or into an empty tube to trap the extracted drug. The effect of extraction pressure and time on absolute recovery were examined. The absolute recovery, selectivity, precision and accuracy of the supercritical fluid extraction approach was compared to conventional liquid—liquid extraction using reversed-phase HPLC with ultraviolet detection.

A Rapid Horizontal TLC Method for Detecting Drugs of Abuse

We present a rapid, low-cost method for detecting opioids, cocaine and amphetamine in the urine of drug abusers. Rapid solid phase extraction of 2 mL of urine using octadecylsilane cartridges (Bond Elut C18) concentrates compounds of interest (including the polar metabolite of cocaine, benzoylecgonine), in a small volume of methanol, which is easily dried down. Four microlitres of aliquots of samples and standards are spotted on to 5 cm square polyester-backed silica gel plates, and developed (8-10 min) in a Desaga H-Chamber. Rf values of all relevant compounds are presented for two mobile phases using an iodoplatinate spray. The sensitivity of the method is not the same for all drugs but is always at least 1 microgram/mL urine. A number of investigations can be performed on a single extract from 2 mL of urine including confirmatory tests using different solvent systems or sprays.

Detection and determination of aflatoxins using affinity chromatography

SummaryAflatoxins B1, B2, G1 and G2 can be easily and rapidly detected in aqueous solutions using an affinity chromatography column coupled to a monoclonal antibody specific for the toxin molecules. Water: methanol extracts of food uncontaminated with aflatoxins were spiked with aflatoxins, diluted with water, and passed through the affinity matrix. The monoclonal antibody is bound to the aflatoxin, which can then be released by using a small volume of methanol. This results in both concentration and separation of the aflatoxin present in solution. As little as 5 ng of aflatoxin can be visualized in the methanol eluate if passed over a small florisil tip under ultraviolet light, while 0.5 ng can be detected in the methanol eluate if analysed by high performance liquid chromatography (HPLC). Thus, this system can be used to test for aflatoxins in contaminated samples by spot testing (&gt; 5 ng) or as a means of HPLC clean‐up for quantitative analysis at subnanogram levels. The advantages of this immunological assay in relation to other immunoassays and traditional methods are discussed.