Simultaneous derivatisation and preconcentration of parabens in food and other matrices by isobutyl chloroformate and dispersive liquid–liquid microextraction followed by gas chromatographic analysis

A simple, rapid and economical method has been proposed for the quantitative determination of parabens (methyl, ethyl, propyl and butyl paraben) in different samples (food, cosmetics and water) based on isobutyl chloroformate (IBCF) derivatisation and preconcentration using dispersive liquid–liquid microextraction in single step. Under optimum conditions, solid samples were extracted with ethanol (disperser solvent) and 200 μL of this extract along with 50 μL of chloroform (extraction solvent) and 10 μL of IBCF was rapidly injected into 2 mL of ultra-pure water containing 150 μL of pyridine to induce formation of a cloudy state. After centrifugation, 1 μL of the sedimented phase was analysed using gas chromatograph-flame ionisation detector (GC–FID) and the peaks were confirmed using gas chromatograph-positive chemical ionisation-mass spectrometer (GC–PCI–MS). Method was found to be linear over the range of 0.1–10 μg mL⁻¹ with square of correlation coefficient (R²) in the range of 0.9913–0.9992. Limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.029–0.102 μg mL⁻¹ and 0.095–0.336 μg mL⁻¹ with a signal to noise ratio of 3:1 and 10:1, respectively.     

A novel quantum dot-based fluoroimmunoassay method for detection of Enrofloxacin residue in chicken muscle tissue

A rapid indirect competitive fluorescence-linked immunosorbent assay (cFLISA) based on quantum dots (QDs) as the fluorescent marker has been developed for the detection of Enrofloxacin (ENR) in chicken muscle tissue. The end-point fluorescent detection system was carried out using QDs conjugated with goat anti-mouse secondary antibody. The cFLISA method allowed for ENR determination in a liner working range of 1–100 ng mL⁻¹ with the 50% inhibition value (IC₅₀) of 8.3 ng mL⁻¹ and the limit of detection (LOD) of 2.5 ng mL⁻¹. The recoveries for chicken muscle samples spiked with ENR at levels of 50–200 μg kg⁻¹ ranged from 81% to 94% with coefficients of variation (CV) of 10–13%. In real chicken tissue sample analysis, the results of cFLISA were similar to those obtained from an indirect competitive enzyme-linked immunosorbent assay (cELISA) to a high performance liquid chromatography method (HPLC), which indicated that cFLISA is suitable as screening method for the monitoring of veterinary drug residues.     

Rapid determination of formaldehyde and sulfur dioxide in food products and Chinese herbals

Simple, sensitive and rapid methods for the determination of formaldehyde and sulfur dioxide were developed. The formaldehyde determination is based on the reaction between formaldehyde and acetylacetone solution, producing yellow 3,5-diacetyl-l-1,4-dihydrolutidine. Sulfur dioxide was detected as the deoxidize of sulfurous acid by zinc in acidic medium, which produces sulfureted hydrogen that make lead acetate paper blackening due to lead sulfide formation. The detection limits were 0.8 μg mL⁻¹ and 6.0 μg mL⁻¹ for formaldehyde and sulfur dioxide, respectively. The linear range were 0.8–20.0 μg mL⁻¹ for formaldehyde and 6.0–100.0 μg mL⁻¹ for sulfur dioxide determination. The main advantages of the new analytical procedure are the low background level, high selectivity, and very little sample preparation for on-site analysis of formaldehyde and sulfur dioxide in food or Chinese herbal samples with reference color card for qualitative or semi-quantitative determination. The results from these methods correlated well with those obtained from the standard methods.     

Determination of melamine by flow injection analysis based on chemiluminescence system

In this paper, based upon the phenomenon that melamine can obviously enhance the CL signal of the luminol–H₂O₂ system in basic medium, a simple, rapid and sensitive flow injection chemiluminescence (FI-CL) method for the determination of melamine has been developed. Under the optimum conditions, the linear range for the determination of melamine was 0.2–80 μg mL⁻¹ with a detection limit of 0.12 μg mL⁻¹ calculated as proposed by IUPAC and a relative standard deviation of 3.26% for 11 solutions of 10 μg mL⁻¹ melamine on the same day. The proposed method was satisfactorily applied to determine melamine in milk-based products and satisfactory results were obtained without interferences from the sample matrix. Moreover, one assay produce takes only 25 s and the minimum sampling rate is about 120 samples h⁻¹, which indicated that the FI-CL method was suitable for high throughput and real-time melamine analysis.     

Effect of modifiers for As,Cu and Pb determinations in sugar-cane spirits by GF AAS

Palladium plus magnesium nitrates with and without Ir, Ru and W were evaluated for the simultaneous determination of As, Cu and Pb in cachaça by graphite furnace atomic absorption spectrometry. For 20 μL of sample, 5 μL Pd(NO₃)₂ and 3 μL Mg(NO₃)₂ dispensed together onto the Ir-coated platform of the THGA, analytical curves in the 0–30.0 μg L⁻¹ As, 0–1.50 mg L⁻¹ Cu and 0–60.0 μg L⁻¹ Pb were built up and typical linear correlation coefficients were always better than 0.999. The limit of detection was 1.30 μg L⁻¹ As, 140 μg L⁻¹ Cu and 0.90 μg L⁻¹ Pb. As, Cu and Pb contents in 10 cachaça samples agreed with those obtained by ICP-MS. Recoveries of spiked samples varied from 96% to 106% (As), 97% to 112% (Cu) and 92% to 108% (Pb). The relative standard deviation (n = 12) was typically 2.7%, 3.3% and 1.9%.     

Double-antibody based immunoassay for the detection of β-casein in bovine milk samples

The concentration of casein (CN) is one of the most important parameters for measuring the quality of bovine milk. Traditional approach to CN concentration determination is Kjeldahl, which is an indirect method for determination of total nitrogen content. Here, we described a double-antibody based direct immunoassay for the detection of β-CN in bovine milk samples. Monoclonal antibody (McAb) was used as capture antibody and polyclonal antibody (PcAb) labelled with horseradish peroxidase (HRP) as detection antibody. With the direct immunoassay format, the linear range of the detection was 0.1–10.0 μg mL⁻¹. The detection limit was 0.04 μg mL⁻¹. In addition, the concentration of β-CN in real bovine milk samples has been detected by the developed immunoassay. There was a good correlation between the results obtained by the developed technique and Kjeldahl method from commercial samples. Compared to the traditional approach, the advantage of the assay is no need of time-consuming sample pretreatment.     

Residue levels of food-grade antioxidants in postharvest treated in-pod peanuts during five months of storage

In order to investigate residue levels of butylated hydroxyanisole (BHA), propyl paraben (PP) and butylated hydroxytoluene (BHT) during storage, eight-hundred kilograms of bulk peanuts were treated with the following antioxidant emulsions: BHA (1802 μg g⁻¹), BHA–PP (1802 μg g⁻¹ + 1802 μg g⁻¹) M1 and BHA–PP–BHT mixtures (1802 μg g⁻¹ + 901 μg g⁻¹ + 2204 μg g⁻¹) M2 and (1802 μg g⁻¹ + 1802 μg g⁻¹ + 2204 μg g⁻¹) M3. Residues were determined in peanut pod and seed tissues at 1-month intervals during the storage. While the reduction levels of BHA and PP in pods at the end of the storage period ranged from 66% to 76%, BHT levels were decreased extensively (86%). Twenty-four hours after peanuts were treated, antioxidant emulsions effectively seeped into the seeds and low levels of these chemicals were detected during the assay. Residues of PP in seeds were lower (62%) than the other antioxidants. Although the doses used were higher than those approved for food-grade antioxidants in stored peanuts, the residue levels in seeds (32.8–0.02 μg g⁻¹) did not exceed the maximum residue limits during the storage period.     

Determination of total phenols in tea infusions,tomato and apple juice by terbium sensitized fluorescence method as an alternative approach to the Folin–Ciocalteu spectrophotometric method

A fast screening of total phenols in tea infusions, tomato and apple juice samples using terbium sensitized fluorescence is described. The proposed method is based on the fluorescence sensitization of terbium (Tb³⁺) by complexation with flavonols (quercein as a reference standard) (at pH 7.0), which fluoresces intensely with an emission maximum at 545 nm when excited at 310 nm. Quercetin and terbium cations (at pH 7.0) form a stable complex and the resulted emission at 545 nm can be used for the determination of the total phenols concentration expressed in terms of “quercetin equivalent”. Based on the obtained results, a sensitive, simple and rapid spectrofluorimetric method was developed for the determination of total phenols. In the optimum conditions, the calibration graph was linear from 0.01 to 2 μg mL⁻¹, with the limit of detection of 0.002 μg mL⁻¹. The relative standard deviation values were in the range of 0.75–2.3%. The total concentrations of quercetin equivalent in five tested samples were found in the range of 6.6–27.9 μg mL⁻¹ and the results compare favorably with those obtained by spectrophotometric method (r = 0.999).     

Tyrosinase inhibitory activity of native plants from central Argentina: Isolation of an active principle from Lithrea molleoides

Screening of 91 native plants from central Argentina was carried out with the aim of finding new sources of anti-tyrosinase compounds. Extracts obtained from Achyrocline satureioides, Artemisia verlotiorum, Cotoneaster glaucophylla, Dalea elegans, Flourensia campestris, Jodina rhombifolia, Kageneckia lanceolata, Lepechinia floribunda, Lepechinia meyenii, Lithrea molleoides, Porlieria microphylla, Pterocaulon alopecuroides, Ruprechtia apetala, Senna aphylla, Sida rhombifolia, Solanum argentinum, Tagetes minuta and Thalictrum decipiens exhibited more than 90% inhibition of tyrosinase monophenolase activity at 1000 μg ml⁻¹. D. elegans,L. meyenii and L. molleoides were the most potent with IC₅₀ values of 0.48, 10.43 and 3.77 μg ml⁻¹, respectively. D. elegans, L. molleoides and T. decipiens also showed more than 90% inhibition of diphenolase activity at 1000 μg ml⁻¹, with the first of these being the most effective (IC₅₀ = 49.27 μg ml⁻¹). (Z,Z)-5-(trideca-4,7-dienyl)-resorcinol (1) was isolated from L. molleoides as an effective tyrosinase inhibitor with l-tyrosine or l-DOPA as substrates (IC₅₀ = 0.49 and 14.94 μg ml⁻¹, respectively). Compound 1 was 37 times more active in monophenolase inhibitory activity than kojic acid used as a reference. Effective extracts as well as (Z,Z)-5-(trideca-4,7-dienyl)-resorcinol could prove to be promising preservative agents for use in the food industry.     

Effect of foliar application of selenium on its uptake and speciation in carrot

Carrot (Daucus carota) shoots were enriched by selenium using foliar application. Solutions of sodium selenite or sodium selenate at 10 and 100 μg Se ml⁻¹, were sprayed on the carrot leaves and the selenium content and uptake rate of selenium were estimated by ICP–MS analysis. Anion and cation exchange HPLC were tailored to and applied for the separation of selenium species in proteolytic extracts of the biological tissues using detection by ICP–MS or ESI–MS/MS. Foliar application of solutions of selenite or selenate at 100 μg Se ml⁻¹ resulted in a selenium concentration of up to 2 μg Se g⁻¹ (dry mass) in the carrot root whereas the selenium concentration in the controls was below the limit of detection at 0.045 μg Se g⁻¹ (dry mass). Selenate-enriched carrot leaves accumulated as much as 80 μg Se g⁻¹ (dry mass), while the selenite-enriched leaves contained approximately 50 μg Se g⁻¹ (dry mass). The speciation analyses showed that inorganic selenium was present in both roots and leaves. The predominant metabolised organic forms of selenium in the roots were selenomethionine and γ-glutamyl-selenomethyl-selenocysteine, regardless of which of the inorganic species were used for foliar application. Only selenomethionine was detected in the carrot leaves. The identity of selenomethionine contained in carrot roots and leaves was successfully confirmed by HPLC–ESI–MS/MS.     

Determination of pyrethroids in porcine tissues by matrix solid-phase dispersion extraction and high-performance liquid chromatography

An effective matrix solid-phase dispersion (MSPD) extraction for determination of two pyrethroids (cypermethrin and deltamethrin) in porcine tissues (liver, muscle, heart and kidney) is described. A neutral alumina-based MPSD column was used for extraction of analytes. The high-performance liquid chromatography and ultraviolet detector was applied using a reverse-phase C₁₈ column and acetonitrile-water (85:15, v/v) was used as mobile phase. The good linear fit curve ranging from 0.05 to 50 μg mL⁻¹ for cypermethrin (CM) and deltamethrin (DM) was obtained with a regression coefficient (r) of 0.999. Recoveries at 0.2 and 0.5 μg g⁻¹ levels were between 83.5% and 109%. The limits of detection and quantification were: 0.01 and 0.026 μg g⁻¹ for CM, 0.017 and 0.056 μg g⁻¹ for DM, respectively. The proposed method was successfully applied to the determination of the pyrethroids in porcine tissues.     

Spectrophotometric determination of melamine in milk by rank annihilation factor analysis based on pH gradual change-UV spectral data

A new spectrophotometric method has been developed in this paper to determine melamine in milk by applying rank annihilation factor analysis (RAFA) based on pH gradual change-UV spectral data (pH-spectra). In the proposed method, the spectra of the sample solutions at different pH data points were recorded and the pH-spectra bilinear data matrix was generated. Based on these data, the RAFA was then applied to calculate the concentration of melamine in milk. The experiments have been conducted and the results were satisfactory. Under the optimised conditions, linearity of the proposed method was in the range of 0.04–4.0 μg mL⁻¹ for calibration samples, and 0.04–3.5 μg mL⁻¹ for the mixed solutions of melamine with the background milk components. The detection limit (DL) was 12 ng mL⁻¹. The relative predictive error (RPEs) and root mean square error of prediction (RMSEP) of applying RAFA were 0.91% and 0.0151, respectively.     

Trace element levels in honeys from different regions of Turkey

A survey of 25 honey samples from different botanical origin, collected all over the Turkey was conducted to assess their trace element contents. The aim of this study was to determine the levels of cadmium (Cd), lead (Pb), iron (Fe), manganese (Mn), copper (Cu), nickel (Ni), chromium (Cr), zinc (Zn), aluminium (Al) and selenium (Se) in honey samples from different regions of Turkey. Trace element contents were determined by a flame and graphite furnace atomic absorption spectrometry technique after dry-ashing, microwave digestion and wet-digestion. The accuracy of the method was corrected by the standard reference material, NIST-SRM 1515 Apple leaves. The contents of trace elements in honey samples were in the range of 0.23–2.41 μg g⁻¹, 0.32–4.56 μg g⁻¹, 1.1–12.7 μg g⁻¹, 1.8–10.2 μg g⁻¹, 8.4–105.8 μg kg⁻¹, 2.6–29.9 μg kg⁻¹, 2.4–37.9 μg kg⁻¹, 0.9–17.9 μg kg⁻¹, 83–325 μg kg⁻¹ and 38–113 μg kg⁻¹ for Cu, Mn, Zn, Fe, Pb, Ni, Cr, Cd, Al and Se, respectively. Iron was the most abundant element while cadmium was the lowest element in the Turkish honeys surveyed. The results showed that trace element concentrations in the honeys from different regions were generally correlated with the degree of trace element contamination of the environment.     

Synthesis and application of a new functionalized resin for use in an on-line,solid phase extraction system for the determination of trace elements in waters and reference cereal materials by flame atomic absorption spectrometry

The synthesis and characterization of the resin Amberlite XAD-4 functionalized with 2,6-pyridinedicarboxaldehyde and its application in an on-line system for the preconcentration of cadmium, cobalt, copper, lead and manganese prior to determination using flame atomic absorption spectrometry (FAAS) is proposed. Metal ions retained on the modified resin were eluted using 1.0 mol L⁻¹ HNO₃ solution and aspirated directly to the nebulizer–burner system of a FAAS instrument using a flow injection system. Detection limits (3σ) were determined to be 0.13 μg L⁻¹ for Cd, 0.29 μg L⁻¹ for Cu, 0.23 μg L⁻¹ for Mn, 0.58 μg L⁻¹ for Co and 2.19 μg L⁻¹ for Pb using a 10 mL of water sample loading volume. The limits of detection would be 100 times higher with units of μg kg⁻¹ for the solid samples in which their dilution ratios as (volume/weight) were 100. Enrichment factors ranged from 23.6 to 28.9 (for Co and Mn, respectively). The proposed method was successfully applied to determination of the analytes in natural water samples and certified reference materials.     

Flow injection analysis of total curcuminoids in turmeric and total antioxidant capacity using 2,2′-diphenyl-1-picrylhydrazyl assay

A simple flow injection analysis procedure is proposed for the determination of curcuminoids content in turmeric extracts. The method is based on the formation of a coloured complex between 4-aminoantipyrine and curcuminoids, in the presence of an oxidising reagent such as potassium hexacyanoferrate (III) in alkaline media. Conditions selected as a result of these trials were implemented in a flow injection analytical system in which the influence of injection volume, flow rate, reagent concentration and mixing coil length, was evaluated. Under the optimum conditions the total amount of curcuminoids could be determined within a concentration range of 5–50 μg mL⁻¹ which can be expressed by the regression equation y = 0.003x − 0.0053 (r² = 0.9997). The limits of detection and quantitation were found to be 0.6 μg mL⁻¹ and 1.8 μg mL⁻¹, respectively. The reproducibility of analytical readings was indicative of standard deviations <2%. The sample was extracted and analysed by using the proposed method. The percentage recoveries were found to be 94.3–108.0. The proposed system was applied to the determination of curcuminoids content in turmeric. The total curcuminoid contents in turmeric extract were found to be 0.9–4.3% (w/w). The development method is simple, economic, rapid and especially suitable for quality control in pharmaceutical plants.     

Phytochemicals content,antioxidant and hypoglycaemic activities of commercial nutmeg mace (Myristica fragrans L.) and pimento (Pimenta dioica (L.) Merr.)

Commercially dried powder of nutmeg mace (Myristica fragrans) and pimento (Pimenta dioica) spices was investigated for their high performance liquid chromatography phenolic profile and their antioxidant and hypoglycaemic properties by α‐amylase and α‐glucosidase inhibition tests. Generally, mace showed the most promising activity. An interesting protection of lipid peroxidation with an IC₅₀ value of 7.7 μg mL^?1 was found. A significant result was also obtained in ferric reducing ability power assay if compared to the positive control butylated hydroxytoluene (IC₅₀ value of 68.7 μg mL^?1 vs. 63.2 μg mL^?1, respectively). Mace also exhibited the highest carbohydrate‐hydrolysing enzyme inhibitory activity with IC₅₀ values of 62.1 and 75.7 μg mL^?1 against α‐amylase and α‐glucosidase, respectively. Overall, these results support the use of these spices not only as flavouring agent but also as food preservative and functional ingredients.     

Development of antipeptide enzyme‐linked immunosorbent assay for determination of gelatin in confectionery products

The gelatin sources have become a controversial issue with regard to religious and health concern. Thus, the aims of this study were to develop and evaluate the efficiency of polyclonal antibodies against peptide immunogen of collagen α2 (I) chain for determination of gelatin sources in confectionery products by competitive indirect enzyme‐linked immunosorbent assay (ELISA). Collagen α2 (I) chain protein showed resistance against heat treatment and detectable in certain commercial products when analysed by sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS‐PAGE). The established ELISA exhibited low cross‐reactivity to fish and chicken gelatin. The IC₅₀ value was 0.39 μg mL^?1, and the limit of detection (IC₁₀) was 0.05 μg mL^?1. There were no false‐positive results from forty‐eight commercially processed products. The present method is useful for determination of gelatin in confectionery products.     

Determination of lead and cadmium in food samples by the coprecipitation method

In this study, the coprecipitation method developed using a combination of 2-mercaptobenzothiazole (MBT) as a chelating reagent and copper as coprecipitate carrier was used for the determination of trace lead and cadmium in various food samples by graphite furnace atomic absorption spectrometry (GFAAS). The method was applied for the determination of Pb(II) and Cd(II) in salami, sausage, chicken, anchovy, spinach, cabbage, onion, dill, parsley, lettuce, tea and rice samples. The matrix modifiers were added as 50 μg NH₄H₂PO₄ + 3 μg Mg(NO₃)₂ for both Pb(II) and Cd(II). The signals were measured as peak area. The concentrations of Pb(II) and Cd(II) in the food samples were found to be in the range of 6.63 ng g⁻¹ (anchovy) −3.30 μg g⁻¹ (spinach) and 2.67 ng g⁻¹ (salami) −0.51 μg g⁻¹ (lettuce), respectively.     

A simple and highly sensitive spectrophotometric determination of Cr(VI) in food samples by using 3,4-dihydroxybenzaldehydeisonicotinoylhydrazone (3,4-DHBINH)

A simple, rapid, sensitive and inexpensive method has been developed for the determination of trace amounts of chromium(VI) using 3,4-dihydroxybenzaldehydeisonicotinoylhydrazone (3,4-DHBINH). The metal ion gives a yellow coloured complex with 3,4-DHBINH in acetate buffer of pH 5.5 with 1:1 (metal:ligand) composition. The complex shows a maximum absorption at 400 nm. Beer’s law is obeyed in the range 0.5–7.7 ppm of Cr(VI). The molar absorptivity, Sandell’s sensitivity and detection limit were found to be 1.35 × 10⁴ L mol⁻¹ cm⁻¹, 0.0075 μg cm⁻² and 0.0045 μg mL⁻¹, respectively. The correlation co-efficient and regression co-efficient of the Cr(VI)–3,4-DHBINH complex were 0.99 and 0.12, respectively. Major cations and anions did not show any interference. The developed method has been successfully applied for the analysis of Cr(VI) in food samples (leafy vegetables), comparing the results simultaneously with those obtained using an Atomic Absorption Spectrophotometer, whereby the validity of the method has been tested.     

Antioxidant and antiacetylcholinesterase activities of five plants used as Portuguese food spices

In the present work, we report the results of a study aimed at evaluating the antiradical activity, the antioxidant activity and the acetylcholinesterase (E.C. 3.1.1.7.) inhibitory capacity of essential oils, ethanol and boiling water extracts from five aromatic herbs growing wild in Portugal and used in traditional food preparations: fennel (Foeniculum vulgare), mint (Mentha spicata), pennyroyal (Mentha pulegium), rosemary (Rosmarinus officinalis) and wild thyme (Thymus serpyllum). The water extracts of M. spicata and M. pulegium showed the highest radical-scavenging activity (DPPH test) values (IC₅₀ = 5.7 ± 0.4 and 8.9 ± 0.2 μg ml⁻¹ respectively). This activity was higher than that found with the standard antioxidant BHT. The ethanol extracts of M. spicata, T. serpyllum and F. vulgare showed the highest antioxidant activities measured by the β-carotene/linoleic acid assay, IC₅₀ = 36.9 ± 0.1, 41.2 ± 0.1 and 68.7 ± 0.1 μg ml⁻¹, respectively. The inhibition of AChE was higher in the essential oil fraction. The highest activity was found for R. officinalis with an IC₅₀ = 69.8 ± 0.1 μg ml⁻¹.