Non-instrumental immunochemical tests for rapid ochratoxin A detection in red wine

Gel-based and membrane-based flow-through immunoassay formats were investigated for rapid ochratoxin A (OTA) detection in red wine. The flow-through set-up consisted of an antibody containing gel or membrane placed at the bottom of a standard solid-phase extraction column (i.e. the flow-through column), combined with a clean-up column. Different clean-up methods were studied for red wine clarification and purification. The optimal method consisted of passing wine, diluted with an aqueous solution containing 1% polyethylene glycol (PEG 6000) and 5% sodium hydrogencarbonate, through strong anion exchange (SAX) silica. An immunoassay for OTA detection in red wine was optimized and a cut-off level at 2 μg L⁻¹ according to EU legislation was achieved with both formats. A more significant colour difference between blank and spiked samples was observed for the gel-based assay making this superior to the membrane-based assay. The proposed rapid gel-based test was compared with a standard immunoaffinity column - high-performance liquid chromatography - fluorescent detection (IAC-HPLC-FLD) method and a good correlation of the results was obtained for naturally contaminated wine samples.     

Monitoring of the non-steroid anti-inflammatory drug indomethacin: development of immunochemical methods for its purification and detection

The present research focused on the development of an immunoassay and an immunochemical sol–gel-based immunoaffinity purification (IAP) method for purification and detection of the non-steroid anti-inflammatory drug (NSAID) indomethacin (IMT). A polyclonal antibody (Ab) for IMT was generated, and two sensitive microplate assays for the detection of IMT were developed (termed OV and HRP formats), based on the enzyme-linked immunosorbent assay (ELISA) method. The limits of detection of the assays were 15 ± 1.25 ng mL⁻¹ (n = 50) and 12 ± 0.17 ng mL⁻¹ (n = 4) for the OVA and HRP formats, respectively. The Abs exhibited slight cross-reactivity with other NSAIDs. The Abs were also used to develop a sol–gel-based IAP method for clean-up and concentration of IMT. Several sol–gel formats with various amounts of antibodies were examined; the best and most reproducible format was at a TMOS:HCl molar ratio of 1:6 in which 120 μL of IMT Abs was entrapped. The binding capacity under these conditions was ca. 100 to 250 ng of IMT with very low non-specific binding (less than 5% of the applied amount). The sol–gel IAP method, combined with solid-phase extraction, successfully eliminated serum interference to a degree that enabled analysis of spiked serum samples by ELISA. The method was also found to be fully compatible with subsequent chemical analytical methods, such as liquid chromatography followed by mass spectrometry. The approaches developed in this study form a basis for analysis of IMT in biological samples in order to monitor their pharmacokinetic properties, and may be further used to study population exposure to IMT, and to monitor the occurrence of IMT contamination in water samples.     

Application of a new anti-zearalenone monoclonal antibody in different immunoassay formats

Monoclonal antibodies against zearalenone (ZEA) were raised in mice according to the hybridoma technology and applied in different immunochemical techniques. More specifically, three formats based on the competitive direct enzyme immunoassay principle were developed: an enzyme-linked immunosorbent assay (ELISA), a flow-through gel-based immunoassay column and a flow-through membrane-based immunoassay. In ELISA, the 50% inhibitory concentration (IC50) was 0.8 ng/mL, and the limit of detection for ZEA standard solutions was 0.1 ng/mL. The antibodies showed a high ZEA (100%) and α-zearalenol (α-ZOL) (69%) recognition, while cross-reactivities with α-zearalanol, zearalanone, β-zearalenol and β- zearalanol were 42%, 22%, <1% and <1%, respectively. For standard solutions, a cut-off level at 10 ng/mL could be established for the gel- and membrane-based enzyme immunoassays. Assay time of both non-instrumental tests was 25 min for 10 samples. By including a simple sample extraction procedure, the methods were applied to wheat with IC50s in ELISA of 80 and 120 μg/kg (dilution up to 5% and 15% (v/v) of wheat matrix, respectively). The cut-off level of the gel- and membrane-based immunoassays was established at 100 μg/kg. Potentials and limitations of the developed methods were compared. The possible application for multi-mycotoxin analysis of the ELISA method based on a single monoclonal antibody was investigated. Therefore, principal component analysis and partial least squares regression data modelling were used to separate the immunoassay responses of two cross-reactants (ZEA and α-ZOL).      

Tetracycline residues in royal jelly and honey by liquid chromatography tandem mass spectrometry: validation study according to Commission Decision 2002/657/EC

A specific, sensitive and robust liquid chromatography tandem mass spectrometry method for determining oxytetracycline, tetracycline, chlortetracycline and doxycycline in royal jelly and honey samples is presented. Extraction of drug residues was performed by ammonium acetate buffer as extractant followed by a clean-up with metal chelate affinity chromatography and solid-phase extraction. Tetracycline analysis was performed using liquid chromatography–electrospray ionisation–tandem mass spectrometry. The presented method is the first validated for royal jelly and in accordance with the requirements set by Commission Decision 2002/657/EC. Recoveries of the methods, calculated spiking the samples at 5.0, 10.0, 20.0 and 30.0 μg kg⁻¹, were 79% to 90% for honey and 77% to 90% for royal jelly. The intra-day precision (RSD) ranged between 8.1% and 15.0% for honey and from 9.1% to 16.3% for royal jelly, while inter-day precision values were from 10.2% to 17.6% and from 10.6% to 18.4% respectively for honey and royal jelly. Linearity for the four analytes was calculated from 5.0 to 50.0 μg kg⁻¹. The decision limits (CCα) ranged from 6.2 to 6.4 μg kg⁻¹ and from 6.1 to 6.5 μg kg⁻¹ for honey and royal jelly, respectively. Detection capabilities values (CCβ) ranged between 7.2 and 7.7 μg kg⁻¹ and from 7.3 to 7.9 μg kg⁻¹ respectively for honey and royal jelly. The developed method is currently in use for confirmation of the official control analysis of honey and royal jelly samples.     

Multiplex dipstick immunoassay for semi-quantitative determination of Fusarium mycotoxins in cereals

A multiplex dipstick immunoassay based method for the simultaneous determination of major Fusarium toxins, namely zearalenone, T-2 and HT-2 toxins, deoxynivalenol and fumonisins in wheat, oats and maize has been developed. The dipstick format was based on an indirect competitive approach. Four test lines (mycotoxin–BSA conjugates) and one control line were located on the strip membrane. Labelled antibodies were freeze-dried within the microwell. Two matrix-related sample preparation protocols have been developed for wheat/oats (not containing fumonisins) and maize (containing fumonisins) respectively. The use of a methanol/water mixture for sample preparation allowed recoveries in the range 73–109% for all mycotoxins in all tested cereals, with relative standard deviation less than 10%. The optimized immunoassay was able to detect target mycotoxins at cut off levels equal to 80% of EU maximum permitted levels, i.e. 280, 400, 1400 and 3200 μg kg⁻¹, respectively, for zearalenone, T-2/HT-2 toxins, deoxynivalenol and fumonisins in maize, and 80, 400 and 1400 μg kg⁻¹, respectively, for zearalenone, T-2/HT-2 toxins and deoxynivalenol in wheat and oats. Analysis of naturally contaminated samples resulted in a good agreement between multiplex dipstick and validated confirmatory LC–MS/MS. The percentage of false positive results was less than or equal to 13%, whereas no false negative results were obtained. Data on the presence/absence of 6 mycotoxins at levels close to EU regulatory levels were obtained within 30 min. The proposed immunoassay protocol is rapid, inexpensive, easy-to-use and fit for purpose of rapid screening of mycotoxins in cereals.     

Monoclonal antibody based electrochemical immunosensor for the determination of ochratoxin A in wheat

Competitive electrochemical enzyme-linked immunosorbent assays based on disposable screen-printed electrodes have been developed for quantitative determination of ochratoxin A (OTA). The assays were carried out using monoclonal antibodies in the direct and indirect format. OTA working range, I₅₀ and detection limits were 0.05-2.5 and 0.1-7.5 μg L⁻¹, 0.35 (±0.04) μg L⁻¹ and 0.9 (±0.1) μg L⁻¹, 60 and 100 μg L⁻¹ in the direct and indirect assay format, respectively. The immunosensor in the direct format was selected for the determination of OTA in wheat. Samples were extracted with aqueous acetonitrile and the extract analyzed directly by the assay without clean-up. The I₅₀ in real samples was 0.2 μg L⁻¹ corresponding to 1.6 μg/kg in the wheat sample with a detection limit of 0.4 μg/kg (calculated as blank signal −3σ). Within- and between-assay variability were less than 5 and 10%, respectively. A good correlation (r = 0.9992) was found by comparative analysis of naturally contaminated wheat samples using this assay and an HPLC/immunoaffinity clean-up method based on the AOAC Official Method 2000.03 for the determination of OTA in barley.     

Multi-mycotoxin analysis of maize silage by LC-MS/MS

This paper describes a method for determination of 27 mycotoxins and other secondary metabolites in maize silage. The method focuses on analytes which are known to be produced by common maize and maize-silage contaminants. A simple pH-buffered sample extraction was developed on the basis of a very fast and simple method for analysis of multiple pesticide residues in food known as QuEChERS. The buffering effectively ensured a stable pH in samples of both well-ensiled maize (pH < 4) and of hot spots with fungal infection (pH > 7). No further clean-up was performed before analysis using liquid chromatography–tandem mass spectrometry. The method was successfully validated for determination of eight analytes qualitatively and 19 quantitatively. Matrix-matched calibration standards were used giving recoveries ranging from 37% to 201% with the majority between 60% and 115%. Repeatability (5–27% RSD_r) and intra-laboratory reproducibility (7–35% RSD_IR) was determined. The limit of detection (LOD) for the quantitatively validated analytes ranged from 1 to 739 μg kg⁻¹. Validation results for citrinin, fumonisin B₁ and fumonisin B₂ were unsatisfying. The method was applied to 20 selected silage samples and alternariol monomethyl ether, andrastin A, alternariol, citreoisocoumarin, deoxynivalenol, enniatin B, fumigaclavine A, gliotoxin, marcfortine A and B, mycophenolic acid, nivalenol, roquefortine A and C and zearalenone were detected.     

An SPR biosensor for the detection of microcystins in drinking water

A surface plasmon resonance (SPR) biosensor for the detection of microcystins (MCs) in drinking water has been developed. Several assay formats have been evaluated. The selected format is based on a competitive inhibition assay, in which microcystin-LR (MCLR) has been covalently immobilized onto the surface of an SPR chip functionalized with a self-assembled monolayer. The influence of several factors affecting sensor performance, such as the nature and concentration of the antibody, the composition of the carrier buffer, and the blocking and regeneration solutions, has been evaluated. The optimized SPR biosensor provides an IC₅₀ 0.67 ± 0.09 μg L⁻¹, a detection limit of 73 ± 8 ng L⁻¹, and a dynamic range from 0.2 to 2.0 μg L⁻¹ for MCLR. Cross-reactivity to other related MCs, such as microcystin-RR (88%) and microcystin-YR (94%), has also been measured. The SPR biosensor can perform four simultaneous determinations in 60 min, and each SPR chip can be reused for at least 40 assay–regeneration cycles without significant binding capacity loss. The biosensor has been successfully applied to the direct analysis of MCLR in drinking water samples, below the provisional guideline value of 1 μg L⁻¹ established by the World Health Organization for drinking water.     

Quantitative trace analysis of a broad range of antiviral drugs in poultry muscle using column-switch liquid chromatography coupled to tandem mass spectrometry

A liquid chromatography–tandem mass spectrometry method for the analysis of seven antiviral drugs, zanamivir, ribavirin, oseltamivir, oseltamivir carboxylate, amantadine, rimantadine and arbidol, in poultry muscle is reported. The antiviral drugs were extracted from the homogenized poultry muscle sample using methanol. The extract was purified using tandem solid-phase extraction combining a cation exchange cartridge and a phenylboronic acid cartridge. To prevent excessive matrix effects, the analytes were separated from the matrix constituents using a column-switch liquid chromatography system combining a reversed-phase and a Hypercarb analytical column. Detection was carried out using tandem mass spectrometry. The method was fully validated according to 2002/657/EC [1] and proved to be adequate for quantification and confirmation of zanamivir and ribavirin at 10 μg kg⁻¹, oseltamivir, oseltamivir carboxylate, amantadine and rimantadine at levels below 1.0 μg kg⁻¹ and for qualitative confirmatory analysis of arbidol at levels below 1 μg kg⁻¹.     

Development of a colloidal gold-based lateral-flow immunoassay for the rapid simultaneous detection of zearalenone and deoxynivalenol

A multianalyte lateral-flow technique using colloidal gold-labeled monoclonal antibodies was developed for the rapid simultaneous detection of deoxynivalenol (DON) and zearalenone (ZEA). The results of this qualitative one-step test were interpreted visually. A very simple and fast sample preparation was used, and the assay procedure could be accomplished within 10 min. When applied to spiked wheat samples, the technique gave accurate and reproducible results. Cut-off levels of 1500 and 100 μg kg⁻¹ for DON and ZEA, respectively, were observed. The described multianalyte format can be used as a reliable, rapid and cost-effective on-site screening technique for the simultaneous determination of mycotoxins in grain samples.     

Effect of organic load on the performance and methane production of an AnSBBR treating effluent from biodiesel production

Currently, there is an increasing demand for the production of biodiesel and, consequently, there will be an increasing need to treat wastewaters resulting from the production process of this biofuel. The main objective of this work was, therefore, to investigate the effect of applied volumetric organic load (AVOL) on the efficiency, stability, and methane production of an anaerobic sequencing batch biofilm reactor applied to the treatment of effluent from biodiesel production. As inert support, polyurethane foam cubes were used in the reactor and mixing was accomplished by recirculating the liquid phase. Increase in AVOL resulted in a drop in organic matter removal efficiency and increase in total volatile acids in the effluent. AVOLs of 1.5, 3.0, 4.5 and 6.0 g COD L⁻¹ day⁻¹ resulted in removal efficiencies of 92%, 81%, 67%, and 50%, for effluent filtered samples, and 91%, 80%, 63%, and 47%, for non-filtered samples, respectively, whereas total volatile acids concentrations in the effluent amounted to 42, 145, 386 and 729 mg HAc L⁻¹, respectively. Moreover, on increasing AVOL from 1.5 to 4.5 g COD L⁻¹ day⁻¹ methane production increased from 29.5 to 55.5 N mL CH₄ g COD⁻¹. However, this production dropped to 36.0 N mL CH₄ g COD⁻¹ when AVOL was increased to 6.0 g COD L⁻¹ day⁻¹, likely due to the higher concentration of volatile acids in the reactor. Despite the higher concentration of volatile acids at the highest AVOL, alkalinity supplementation to the influent, in the form of sodium bicarbonate, at a ratio of 0.5–1.3 g NaHCO₃ g COD_fed⁻¹, was sufficient to maintain the pH near neutral and guarantee process stability during reactor operation.     

Simultaneous extraction of polycyclic aromatic hydrocarbons and polychlorinated biphenyls in agricultural soils by pressurized liquid extraction and determination by gas chromatography coupled to tandem mass spectrometry

A simple and rapid method based on pressurized liquid extraction has been validated for the simultaneous extraction of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) from agricultural soil samples. Effective extraction was carried out in less than 17 min for all the studied compounds, and good recoveries were obtained for PAHs and PCBs, ranging from 70% to 112%, when blank samples were spiked at 2.5 μg kg⁻¹, except for naphthalene with recoveries close to 40%. The separation and determination were performed by gas chromatography coupled to tandem mass spectrometry using a triple quadrupole mass analyzer. The target compounds were detected by electron impact with selected reaction monitoring, and mass spectrometric conditions were optimized in order to increase selectivity and sensitivity. The developed method was validated, and matrix-matched calibration was used for quantification purposes. Repeatability and interday precision ranged from 0.9% to 16.8% and from 1.6% to 22.3%, respectively. Limits of quantification ranged from 0.07 to 2.50 μg kg⁻¹. The proposed method was applied to the analysis of agricultural soil samples collected from Almeria (Spain), and PAHs and PCBs were detected in some samples at concentrations ranging from 0.1 to 210 μg kg⁻¹.     

Enzyme-linked immunosorbent assay and colloidal gold immunoassay for ochratoxin A: investigation of analytical conditions and sample matrix on assay performance

A polyclonal antibody against ochratoxin A (OTA) was produced from rabbits immunized with the OTA–BSA conjugate. A competitive direct enzyme-linked immunosorbent assay (cdELISA) and a membrane-base colloidal gold immunoassay in flow-through format were developed for the rapid detection of OTA in various food matrices. In the cdELISA, the concentration causing 50% inhibition was 0.07 ng mL⁻¹, and the effects of different chemical conditions (ionic strength, pH value, and organic solvent) were studied. The sensitivity of the assay was higher than those previously reported. A simple, rapid, and efficient extraction method was developed and 74–110% recoveries of spiked samples were obtained. Fifty percent methanol extracts of some food samples such as barley, wheat, oat, corn, rice, and raisins could be analyzed directly by immunoassay after dilution in PBS; grape juice and beer samples could be analyzed directly after dilution with PBS; for coffee samples, a more complex method was used to remove the matrix effect effectively. Membrane-based colloidal gold immunoassays had a visual detection limit of 1.0 ng mL⁻¹ for OTA with a detection time of less than 10 min. For the validation of the cdELISA and membrane-based colloidal gold immunoassay, samples were analyzed by high-performance liquid chromatography. The correlation between data obtained using the microwell assay and HPLC was good (R ² = 0.984). The developed immunoassay methods are suitable for the rapid quantitative or qualitative determination of OTA in food samples.     

Determination of fluoroquinolone residues in poultry muscle in Portugal

A total of 98 poultry samples, including chicken and turkey muscle, were analysed, using a sensitive and reliable analytical method based on liquid chromatography (LC) with spectrofluorimetric detection, for simultaneous determination of four fluoroquinolone (FQ) antibiotics, namely enrofloxacin (ENRO), ciprofloxacin (CIPRO), norfloxacin (NOR), and sarafloxacin (SARA). The method involved extraction with 0.15 mol L⁻¹ HCl and clean-up by solid-phase extraction using Oasis HLB cartridges. Chromatographic separation was carried out on a C₁₈ TSK gel column, in isocratic mode, with 0.025 mol L⁻¹ H₃PO₄ solution, adjusted to pH 3.0 with tetrabutylammonium hydroxide-methanol (78:22) as mobile phase. Good linearity over the investigated concentration range was observed, with mean values of correlation coefficients higher than 0.9989 for all the analytes studied. The limits of quantification (LOQ), expressed as the lowest fortification level with acceptable precision were 15 μg kg⁻¹ for ENRO, CIPRO, and NOR, and 30 μg kg⁻¹ for SARA; these values are in compliance with requirements for monitoring of maximum residues levels (MRLs). Overall recoveries from spiked samples ranged from 80% to 92% with relative standard deviations (RSD) lower than 6.1%. Of the chicken and turkey samples analysed, 44.2% and 37.8%, respectively, were contaminated. The levels found in the analysed poultry samples, collected from markets of Oporto and Coimbra, located in the north and central zones of Portugal, respectively, were lower than 114.2 and 87.6 μg kg⁻¹ in chicken and turkey muscle samples, respectively. One positive chicken sample was contaminated with ENRO at levels higher than the MRL.     

Comparison of the efficiency of different extraction methods for the simultaneous determination of mycotoxins and pesticides in milk samples by ultra high-performance liquid chromatography-tandem mass spectrometry

A rapid multi-analyte method has been developed for the simultaneous determination of pesticides and mycotoxins in milk by ultra high-performance liquid chromatography coupled to triple quadrupole mass spectrometry (UHPLC–QqQ–MS/MS). A variety of methodologies has been evaluated, including solid-phase extraction (SPE), “dilute-and-shoot” (liquid–liquid extraction-based procedures), and QuEChERS (quick, easy, cheap, effective, rugged, and safe)-based methods. The optimization and development process was carried out considering that the maximum residue level for aflatoxin M1 (AFM1) in milk in the European Union (EU) is set at 0.05 μg kg⁻¹, which is the lowest tolerance in the target compounds. The selected method consisted of an extraction by SPE using C18 as sorbent and methanol as elution solvent. The final determination was performed by UHPLC–QqQ–MS/MS. Matrix-matched standard calibration was used for quantification, obtaining recoveries in the range 60–120% with relative standard deviations <25%, at three spiking levels: 0.5, 10, and 50 μg kg⁻¹ (ten times lower for AFM1). Limits of quantification ranged from 0.20 to 0.67 μg kg⁻¹, which were always below or equal to the established tolerance levels by the EU. Finally, the selected method was applied to different types of milk.     

Analysis of captan, folpet, and captafol in apples by dispersive liquid–liquid microextraction combined with gas chromatography

A novel method was developed for the determination of captan, folpet, and captafol in apples by dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography–electron capture detection (GC–ECD). Some experimental parameters that influence the extraction efficiency, such as the type and volume of the disperser solvents and extraction solvents, extraction time, and addition of salt, were studied and optimized to obtain the best extraction results. Under the optimum conditions, high enrichment factors for the compounds were achieved ranging from 824 to 912. The recoveries of fungicides in apples at spiking levels of 20.0 μg kg⁻¹ and 70.0 μg kg⁻¹ were 93.0–109.5% and 95.4–107.7%, respectively. The relative standard deviations (RSDs) for the apple samples at 30.0 μg kg⁻¹ of each fungicide were in the range from 3.8 to 4.9%. The limits of detection were between 3.0 and 8.0 μg kg⁻¹. The linearity of the method ranged from 10 to 100 μg kg⁻¹ for the three fungicides, with correlation coefficients (r ²) varying from 0.9982 to 0.9997. The obtained results show that the DLLME combined with GC–ECD can satisfy the requirements for the determination of fungicides in apple samples. Figure Dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography–electron capture detection (GC–ECD) allows satisfactory determination of fungicides in apple samples     

Effect of various oxidants in a photocatalysis/filtration system for the treatment of contaminants

This study was conducted to investigate the effect of a photocatalysis/oxidant system for the treatment of humic acid and hazardous heavy metals in aqueous solutions. Hydrogen peroxide, ozone, and potassium peroxodisulfate were tested as oxidants. The effect of oxidant concentration was conducted with a pH of 7, a UV intensity of 64 W, and a TiO₂ dosage of 0.3 g L⁻¹. The oxidant addition in the UV/TiO₂ system enhanced the degradation efficiency of humic acid and hazardous heavy metals compared to no addition of an oxidant. The addition of oxidants over the amounts of H₂O₂ 50 mg L⁻¹, O₃ 20 g m⁻³, and K₂S₂O₈ 50 mg L⁻¹ inhibits the system efficiency. The negative effect of higher oxidant concentrations likely results from OH radical quenching caused by the excess oxidant. Therefore, the optimal dosages of oxidants such as a hydrogen peroxide, ozone, and potassium peroxodisulfate were found to be 50 mg L⁻¹, 20 g m⁻³, and 50 mg L⁻¹, respectively. The degradation efficiency of UV/TiO₂/oxidant systems for the removal of humic acid and hazardous heavy metals was much greater in the UV/TiO₂/H₂O₂ system using H₂O₂ as an oxidant.     

Production and analytical characterization of neopterin immunoreagents for biosensor developments

Neopterin is a valuable biomarker of cellular immunity associated with various pathological situations such as viral and bacterial infections, autoimmune, cardiovascular, neurodegenerative and malignant disorders. To produce specific antibodies against neopterin for a rapid multi-biomarker-based diagnosis, a novel hapten derivative was synthesized and attached to carrier proteins. The thoroughly characterized conjugates were used for immunization of BALB/c mice and rabbits. The produced monoclonal antibody reached in both direct and indirect enzyme-linked immunosorbent assay (ELISA) format LoD of 0.18 and 0.45 μg L⁻¹, respectively, and was a superior immunoreagent for further biosensor developments with regard to assay sensitivity and material availability. The best polyclonal antibody was somewhat more sensitive in direct ELISA with LoD of 0.05 μg L⁻¹. The optimized ELISA method was evaluated with blood samples collected from patients with renal insufficiency, patients with sepsis, patients without confirmed clinical diagnosis, and healthy volunteers. In plasma samples, neopterin concentrations ranging from 3.2 to 103 μg L⁻¹ could be determined with the monoclonal ELISA whereas twofold lower results were obtained with the polyclonal ELISA. A satisfactory correlation of results was found between the polyclonal ELISA and IBL Neopterin ELISA kit within the concentration range 0.5–16 μg L⁻¹ (R = 0.874; n = 40), and slightly lower correlation was found for monoclonal-based ELISA (R = 0.819; n = 40). These data show that the generated antibodies may be used as functional analytical reagents for the integration into multianalyte biochip detection systems.     

Determination of iodine in biological materials by pseudo-cyclic epithermal INAA using anti-coincidence gamma-ray spectrometry and estimation of expanded uncertainties

Epithermal instrumental neutron activation analysis (EINAA) technique in conjunction with anti-coincidence gamma-ray spectrometry (AC) has been applied for the determination of ppm to ppb levels of iodine in biological materials containing high levels of Al, Br, Cl, K, Mn, and Na. Both conventional EINAA-AC and pseudo-cyclic EINAA-AC (PC-EINAA-AC) methods using a combination of Cd and B filters have been developed using Dalhousie University SLOWPOKE-2 reactor (DUSR) facility. The expanded uncertainties (EU), at about 95% confidence level, for iodine in biological materials by EINAA-AC varied between 6 and 10%. The advantages of the non-destructive PC-EINAA-AC method has been successfully demonstrated by analyzing the NIST Pine Needles (SRM 1575) containing a low amount of iodine in presence of high quantities of Mn and other interfering elements where an iodine content of 92.8 μg kg⁻¹ with an EU of 6.1 μg kg⁻¹ and a detection limit of 40 μg kg⁻¹ has been obtained at the end of fourth cycle.     

Determination of low-level ink photoinitiator residues in packaged milk by solid-phase extraction and LC-ESI/MS/MS using triple-quadrupole mass analyzer

A confirmatory and quantitative method based on liquid chromatography–electrospray ionization tandem mass spectrometry (LC-ESI/MS/MS) has been developed for simultaneous determination of seven photoinitiator residues: benzophenone, (1-hydroxycyclohexyl)phenylketone (Irgacure 184), isopropylthioxanthone (ITX), 2-ethylhexyl-(4-dimethylamino)benzoate (EHA or EHDAB), 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone (Irgacure 907), (2,4,6-trimethylbenzoyl)diphenylphosphine oxide (TPO) and 2-benzyl-2-(dimethylamino)-1-(4-morpholinophenyl)-1-butanone (Irgacure 369) in packaged milk and related packaging materials. Residues of photoinitiators were extracted from milk using acetonitrile, and further enriched and purified on HLB solid-phase extraction cartridges prior to being analyzed by LC-ESI/MS/MS with selected reaction monitoring mode, while photoinitiators in packaging materials were extracted using the same solvent. Satisfactory recovery (from 80 to 111%), intra- and inter-day precision (below 12%), and low limits of quantification (from 0.1 to 5.0 μg kg⁻¹) were evaluated from spiked samples at three concentration levels (5.0, 10.0 and 25.0 μg kg⁻¹ for Irgacure 184 and 2.5, 5.0 and 25.0 μg kg⁻¹ for others). These excellent validation data suggested the possibility of using the LC-ESI/MS/MS method for simultaneous determination of low-level photoinitiator residues migrating from printed food-packaging materials into milk. The method has been successfully applied to the analysis of real samples of different fat contents ranging from 8 to 30 g L⁻¹. The photoinitiator residues were revealed to be higher in milk with higher fat content and the most important contaminations were benzophenone and ITX in concentration ranges of 2.84–18.35 and 0.83–8.87 μg kg⁻¹, respectively.