An efficient,rapid and microwave-accelerated dispersive liquid–liquid microextraction method for extraction and pre-concentration of some organophosphorus pesticide residues from aqueous samples

In this paper, microwave-accelerated dispersive liquid–liquid microextraction has been developed for the extraction/preconcentration of some organophosphorus pesticides from aqueous samples prior to their analysis by gas chromatography–flame ionization detection. In this method, temperature of a high volume of aqueous sample is elevated by a microwave oven and then a mixture of extraction and disperser solvents is rapidly injected into the aqueous phase. After cooling to room temperature, the phase separation is accelerated by centrifuging. The main experimental factors affecting performance of the method including type and volume of the extraction and disperser solvents, temperature, pH, and salt addition were investigated and optimized. Under the optimum extraction conditions, the method resulted in low limits of detection and quantification within the ranges of 0.65–1.3 and 2.2–4.5 μg L⁻¹, respectively. Relative standard deviations were in the range of 2–7% (C = 40 or 100 μg L⁻¹) for intra-day (n = 6) and inter-day (n = 4) precisions. Finally, the proposed method was successfully applied to analysis of the target analytes in surface water and well water and fruit juice samples; diazinon was determined at μg L⁻¹ level in apple juice.     

A rapid method for simultaneous determination of nitrate,nitrite and thiocyanate in milk by CZE-UV using quaternary ammonium chitosan as electroosmotic flow inverter

This paper proposes a rapid method for the simultaneous determination of nitrate, nitrite and thiocyanate in different milk samples (cow, goat and soy) using capillary zone electrophoresis. The separations were conducted in a fused silica capillary dynamically coated with quaternary ammonium chitosan, with a total length of 48.5 cm (40 cm effective x 75 μm internal diameter) and direct detection in the UV region at 210 nm. The background electrolyte (BGE) was composed of 30 mmol L⁻¹ of aminocaproic acid and 24 mmol L¹ of perchloric acid (pH 3.85).A typical anodic electroosmotic flow of -31 × 10^-9 m² V⁻¹ s⁻¹ was observed at the pH of the separations. Bromate was used as the internal standard. The samples were injected by hydrodynamic pressure (50 mbar, 40 s) and the separation voltage was −30 kV. The proposed method was validated and presented good linearity (R²> 0.99) in the linear range of 0.1–4.0 mg L⁻¹. The ranges of the limit of detection (LOD) and limit of quantification (LOQ) were 0.03-0.04 and 0.05–0.07 mg L⁻¹, respectively. The intra-day and inter-day precision values were better than 4.2 and 8.7 %, respectively. Recovery values ranged from 85 to 104% for the different samples of milk. The proposed method was applied in 12 commercial samples with run times of less than 2 min. The good analytical performance indicates that the method proposed is a promising alternative for the determination of nitrate, thiocyanate and nitrite in milk samples.     

Selective extraction of Cu+ and Cu2+ ions from mushroom and lichen samples prior to analysis by micro-volume UV-Vis spectrophotometry: Application of a novel poly (SMIm)-Tris-Fe3O4 nanocomposite

In this study, a novel poly (SMIm)-Tris-Fe₃O₄ nanocomposite was prepared for selective extraction of Cu⁺ and Cu²⁺ ions by ultrasound assisted-cloud point extraction (UA-CPE). The nanocomposite was characterized by analysis of ATR-FT-IR, ¹H NMR and XRD. After optimization of the extraction conditions, the copper ions were independently detected against sample blank at 347 nm by micro-volume UV–vis spectrophotometer. Under the optimal conditions, good linear relationship was obtained in the ranges of 0.3−150 and 10−350 μg L⁻¹ for each ion at pH 7.0 and pH 5.0, respectively, with a better regression coefficient than 0.992. The method detection limits, accuracy and precision were 0.095 and 3.03 μg L⁻¹, 91.5−96.0 % and 93.0−98.5 %, and 2.5–4.5 and 3.8–7.1 % (n:5, 25 and 100 μg L⁻¹) for Cu⁺ and Cu²⁺ ions, respectively. A preconcentration of 70-fold was obtained from 35-mL of sample. After validation, the method was successfully applied to determination of total Cu levels in lichen and mushroom samples after pre-reduction at pH 7.0, and the recoveries in the range of 90−96 % were obtained by two calibration approaches after spiking with 10 μg L⁻¹. The results were also statistically compared with those obtained by FAAS analysis to ensure accuracy and precision.     

Comparison of the chemical composition of British and Continental European bottled waters by multivariate analysis

The elemental composition of 37 bottled waters from the UK and continental Europe has been determined. Ca, K, Mg, Na, Al, As, Ba, Cd, Cr, Co, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Sr, U, V and Zn were determined by ICP-OES and ICP-MS, in addition to inorganic and total organic carbon. The composition of all the waters analysed fell within the guideline values recommended by the World Health Organization. Na, Ca, Sr and Ba showed the widest variation in concentrations, ranging over two orders of magnitude. Levels of Fe were below the limit of detection (30 μg L⁻¹) in all samples analysed. Waters produced in the UK generally showed lower levels of most major elements and trace metals, with the exception of Ba (up to 455 μg L⁻¹). Italian waters showed the highest concentrations of Sr (3000–8000 μg L⁻¹) and U (8–13 μg L⁻¹), whereas waters produced in Slovakia and the Czech Republic showed the highest levels of Pb (0.7–4 μg L⁻¹). The use of multivariate analysis reveals an association between high alkaline metal content and high concentrations of As and Cr. There also appears to be a correlation between high Ca and Sr content and high levels of U. Analysis of variance (ANOVA) indicates that the composition of bottled water can be distinguished primarily by the country of origin, over other factors including the geological environment of the source. This would suggest that composition reflects, and is biased towards, consumer preferences.     

Ultra-high-pressure liquid chromatography–solid-phase clean-up for determining aflatoxins in Egyptian food commodities

In this work, we determined the content of regulated aflatoxins (ATs) B1, B2, G1, and G2 in food commodities using solid-phase extraction (SPE) and ultra-high-pressure liquid chromatography with fluorescence detection without derivatization. We extracted ATs from the ground samples by mixing in NaCl and 80% (v/v) methanol. The sample was enriched and cleaned up by SPE technique using Bakerbond^® C18 cartridges. The extract that we obtained was immediately analyzed using isocratic elution with a mobile phase consisting of acetonitrile, methanol and deionized water in a ratio of 64:18:18. Method validation was carried out by determining these ATs in a quality control material consisting of almond T02445QC and with the add-found test. The results provided satisfactory recovery within the range of 89.6–103.3%. Repeatability and intermediate precisions were assessed as RSD (%) which were found in the range of 1.1–11.3% and 1.5–12.0%, respectively. The limit of detection (S/N = 3) was 0.03, 0.02, 0.04, and 0.02 μg kg⁻¹ for B1, B2, G1 and G2, respectively. Finally, the method was successfully applied to determine ATs in raw Egyptian food commodities, namely maize, popcorn, pistachio, corn, peanuts, chilli, wheat, green coffee and almond, and the corresponding RSD did not exceed 11%.     

Determination of furfural and hydroxymethyl furfural from baby formula using dispersive liquid–liquid microextraction coupled with high performance liquid chromatography and method optimization by response surface methodology

A simple, rapid and efficient method was developed using dispersive liquid–liquid microextraction (DLLME) coupled with high performance liquid chromatography (HPLC) for extraction and determination of furfural (F) and hydroxymethyl furfural (HMF) in baby formula. The effects of different variables on the extraction efficiency such as the volume of extraction and disperser solvents, pH and salt effect were studied and optimized simultaneously using (RSM) based on central composite design (CCD). Under optimum conditions, a mixture of ethanol (disperser solvent) and 1-octanol (extraction solvent) was rapidly injected in to the sample solution (after adding 2 g salt and adjusting pH to 6.5). Limit of detection for F and HMF were 0.7 and 1.8 ng g⁻¹, respectively. The inter-day relative standard deviation (RSD%) were 4.9 for HMF and 3.9 for F and also inter-day RSD% were in the range of 5.2–8%. The results showed that DLLME-HPLC is a very fast, simple, sensitive and accurate analytical method for the determination of F and HMF in baby formulas. Finally, The ability of the proposed method to determine F and HMF in different baby formulas in Iran was studied and suitable result was obtained.     

Nanofluid extraction of Ochratoxin A in food

Monitoring of Ochratoxin A (OTA), a toxic and carcinogenic metabolite of fungi, requires accurate and precise analytical methods. Quantitative determination of OTA at trace level in raisin samples was evaluated by nanofluid extraction coupled with HPLC–FLD. The experimental parameters affecting the extraction efficiency of OTA were investigated and optimized. The validated method has low detection and quantification limit (0.2 and 0.5 ng g⁻¹). Moreover, under optimum conditions, the repeatability of the method expressed as the relative standard deviation for intra-day and inter-day precision (RSD %) was below 15 % (n = 3). This method has also been successfully applied to the analysis of trace amounts of OTA in real samples with satisfactory relative recoveries in the range of 70.3–84.7 %.     

Assessing sialic acid content in food by hydrophilic chromatography-high performance liquid chromatography

We have established a novel hydrophilic chromatography (HILIC)-high performance liquid chromatography (HPLC) method to assess sialic acid content in food products. Single-factor and response surface methodologies (RSM) were used to systematically optimize the hydrolysis conditions of the food samples to extract the maximum amount of sialic acid. Chromatographic conditions were also adjusted. In foods containing sialic acid, we observed a strong linear relationship between sialic acid and peak area, ranging from 5 to 100 μg/mL (R² = 0.9998). The lowest detectable sialic acid concentration (RSN = 3) was 0.2 μg mL⁻¹, and the method detection limit was 0.02mg kg⁻¹. Sample recovery ranged from 95.85% to 99.78%, with an RSD of 1.46% (n = 6). Thus, the described method can be applied to the study of sialic acid content in foods.     

Spectrophotometric method for determination of aluminium content in water and beverage samples employing flow-batch sequential injection system

A sensitive, precise and reliable flow-batch method for the determination of aluminium (Al) was developed using a sequential injection-monosegmented flow system incorporating a mixing chamber unit. Eriochrome cyanine R (ECR) was used as a chromogenic reagent in the presence of N,N-dodecyltrimethylammonium bromide (DTAB). The Al-ECR complex at pH 6 gave a maximum absorption at 584 nm. In-line single standard calibration and a standard addition procedure were developed employing the monosegmented flow technique. Under the optimum conditions, a linear calibration graph in the range of 0.0075–0.625 mg L⁻¹ Al was obtained with limits of detection and quantitation of 0.0020 and 0.0070 mg L⁻¹, respectively. Relative standard deviations were 0.8 and 1.3% for 0.010 and 0.025 mg L⁻¹ Al (n = 11), respectively. A sample throughput of 24 h⁻¹ using an in-line standard calibration approach and 6 h⁻¹ using four standard addition levels was achieved. The developed system was successfully applied to water samples and beverage samples. The results agreed well with those obtained from the ICP-AES method. Good recoveries between 85 and 104% were obtained.     

Application of deep eutectic solvent as a disperser in reversed-phase dispersive liquid-liquid microextraction for the extraction of Cd(II) and Zn(II) ions from oil samples

A new, sensitive, and safe pretreatment method for the analysis of Cd(II) and Zn(II) ions in oil samples prior to flame atomic absorption spectrometry was developed. For the first time, a deep eutectic solvent is used as a disperser in reversed-phase dispersive liquid-liquid microextraction procedure. For this purpose, a deep eutectic solvent with low viscosity and miscible with both aqueous and organic phases is prepared by mixing glycolic acid and mandelic acid at a molar ratio of 2:1. The variables involved in this process were studied to provide high enrichment factors. Under optimized conditions, the linear ranges of calibration curves for Cd(II) and Zn(II) ions were obtained 0.30−20 and 0.50−30 μg L⁻¹, respectively. The obtained detection limits and enrichment factors were 0.12 and 0.18 μg L⁻¹; and 32.7 and 32.2 for Cd(II) and Zn(II), respectively. Repeatability of the proposed method, expressed as relative standard deviation, ranged from 2.7 to 4.1 % (n = 6, C = 1 μg L⁻¹ of each cation). Finally, the proposed method was successfully applied for the determination of Cd(II) and Zn(II) concentrations in various oil samples.     

Application of non-supervised pattern recognition techniques to classify Cabernet Sauvignon wines from the Balkan region based on individual phenolic compounds

Phenolic compounds in sixteen Cabernet Sauvignon wines from different wine-growing sub-regions in the Balkan region were investigated using HPLC with DAD and fluorescence detector and spectroscopic analysis, as well as statistical PC/F and cluster analysis. The HPLC analysis of investigated red wines showed that the content of total hydroxybenzoic acids, detected at 280 nm, was the highest in wines from Tikveš wine-growing subregion, Macedonia (127–140 mg L⁻¹). Total hydroxycinnamic acids, detected at 320 nm, were the highest in wines from Župa wine-growing subregion, Serbia (43–45 mg L⁻¹). The concentration of total flavonoids (flavan-3-ols, flavonols, flavons and flavanon), detected at 280, 360 and 322/275 nm, respectively, was the highest in wine from Katarzyna Estate wine-growing subregion, Bulgaria (167 mg L⁻¹). Finally, the concentration of total anthocyanins, detected at 520 nm, was the highest in wine from Šumadija wine-growing subregion, Serbia (1463 mg L⁻¹). The results of PCA and cluster analysis together confirmed that the content of phenolic compounds in Cabernet Sauvignon wines depends on agro-climatic factors, oenological practice in different wineries and the growing season in the Balkan region that were investigated. The areas in the Balkan region in this study with similar agro-climatic characteristics showed shorter clustering distance, indicating similar phenol profiling in the red wines tested.     

Zirconium nanoparticles based ligandless dispersive solid phase extraction for the determination of antimony in bergamot and mint tea samples by slotted quartz tube-flame atomic absorption spectrophotometry

A sensitive and effective analytical method was developed to preconcentrate antimony from the bergamot and mint tea samples for its determination at trace levels by slotted quartz tube-flame atomic absorption spectrophotometry (SQT-FAAS) system. The developed method was based on vortex assisted ligandless dispersive solid phase extraction (VA-LDSPE) using zirconium nanoparticles (Zr-NPs) as sorbent material for the adsorption of the target analyte. All variables involved in the DSPE method (pH value, nanoparticle amount, mixing and eluent type/volume) were optimized to boost the absorbance signal of antimony. Using the optimal parameters, the method provided satisfactory detection and quantification limits of 8.0 and 26.8 μg L⁻¹, respectively. A 180 folds enrichment factor was achieved by the developed method when compared with the detection power of the FAAS. Linear range of the proposed method was found to be 30–250 μg L⁻¹, with a coefficient of determination value of 0.9992. The established Zr-NPs-VA-LDSPE-SQT-FAAS method was successfully implemented to bergamot tea samples in order to check accuracy and applicability. The obtained recovery values ranged between 93–102%, and this demonstrated that the complex matrices tested did not affect the accuracy of quantifying antimony.     

Exposure to nickel through commercial premade baby foods: Is there any risk?

A study was performed to evaluate the risk regarding the presence of nickel in commercial premade baby foods: 26 ready meals, 31 fruits, 8 deserts and 20 paps. The analytical methodology used for the determination of nickel was dry ashing followed by graphite furnace atomic absorption spectrometry. Method detection limit (12.5 μg kg⁻¹) was obtained through a matrix matched calibration curve, using a nickel free commercial ready meal (meat).The results showed that 78 (91.8 %) samples contained nickel, with values up to 225.7 μg kg⁻¹. The group with the highest average concentration was the fruits (50.1 μg kg⁻¹) followed by the ready meals (40.2 μg kg⁻¹). Samples from organic farming presented higher detection frequency and average concentration (54.7 μg kg⁻¹) than the others. Using the average results, the tolerable daily intake proposed by EFSA (2.8 μg kg⁻¹ b.w.) was surpassed for the 2 year old age group, with daily ingestions up to 3.1 μg kg⁻¹ b.w.. This results highlight the risk promoted by the nickel present in commercial premade baby food.     

Investigation of amino acids in wolfberry fruit (Lycium barbarum) by solid-phase extraction and liquid chromatography with precolumn derivatization

The aim of this work is to present a simple and sensitive reverse-phase liquid chromatography method for the determination and investigation of amino acids in wolfberry fruit (Lycium barbarum) after solid-phase extraction-derivatization. The method linearity, calculated for each amino acid, had a correlation coefficient higher than 0.9950, in concentrations ranged from 9.60 to 3.33 × 10³ μmol L⁻¹. The detection limits of amino acids were between 2.42 and 6.51 μmol L⁻¹. The calculated recoveries for amino acids in wolfberry fruit were from 87.3% to 97.1% and relative standard deviations were from 2.62% to 5.22%. The investigation illustrated that each tested wolfberry fruit contained at least 16 amino acids and the main amino acids were glutamic acid, aspartic acid, proline, alanine, serine, glycine, lysine, and tyrosine. The levels of amino acid in wolfberry fruit were varying from different areas.     

Assessment of hydroxymethylfurfural and furfural in commercial bakery products

A survey was conducted on the presence of hydroxymethylfurfural (HMF) and furfural in bread and bakery products; for this purpose a reliable extraction procedure followed by high performance liquid chromatography (HPLC) was applied. The performance of the method was evaluated in terms of linearity (r always > 0.99); detection limits (0.001 mg L⁻¹ for furfural and 0.006 mg L⁻¹ for HMF); recovery percentages (98.5–100.5% for HMF and 94.9–98.9% for furfural); intraday precision (<4.65%) and interday precision (<7.51%). Two batches of a wide variety of products commercially available were analysed (a total of 88 samples). HMF and furfural levels presented high variability between products and batches of the same product. Cake/pastry samples showed the lowest HMF content (3.0 mg kg⁻¹ fw) while biscuits showed the highest content (7.8 mg kg⁻¹ fw) (p < 0.05). Regarding furfural, bread samples presented the highest furfural content (5.3 mg kg⁻¹ fw) (p < 0.05), cake/pastry and biscuits showed the lowest content (1.9 and 3.0 mg kg⁻¹ fw, respectively). Chocolate containing samples presented higher amounts of furfural (>20 mg kg⁻¹). These results indicate that special attention should be given to furfural content of bread (due to its daily high consumption) and re-evaluation of dietary exposure.     

A rapid and sensitive method for the determination of dibutyl phthalate in wine by flow-injection chemiluminescence analysis

A sensitive method for the determination of picogram level dibutyl phthalate (DBP) in wine by flow-injection chemiluminescence (FI–CL) analysis is presented for the first time, which was based on the quenching effect of DBP on the luminol–myoglobin (Mb) CL system. The decrement of CL intensity was linearly proportional to the logarithm of DBP concentration in the range of 0.1–100 pg mL⁻¹ with the detection limit of 0.03 pg mL⁻¹ (3σ). At a flow rate of 2.0 mL min⁻¹, a complete determination of DBP including sampling and washing could be accomplished in 0.5 min, giving the maximum sample throughput of 120 h⁻¹. The proposed method was successfully applied to the determination of DBP in wine, human serum and urine samples with the relative standard deviations (RSDs) of less than 3.0% (n = 5). The molecule docking results showed that DBP interacted with the amino acid residues near the heme moiety of Mb. The possible CL mechanism of luminol–Mb–DBP reaction should be that the binding of Mb with DBP forming a 1:1 complex (binding constant K = 1.55 × 10⁴ L mol⁻¹) led to the conformational change of Mb and resulted in the quenching of CL intensity.     

Determination and health risk assessment of heavy metals in imported rice bran oil in Iran

In this current study, the contents of heavy metals including Pb, As, Cr, Cd, Zn, Cu, and Mn in imported rice bran oil in Iran were investigated with microwave digestion method based on an inductively coupled plasma optical emission spectrometry system (ICP-OES). The concentrations range of Pb, Cr, Cd, As, Zn, and Cu in rice bran oil samples were measured as 0.066–0.30, 0.008–0.014, 0.005–0.01, 0.047–0.01, 0.025–0.74 and 0.01–0.096 μg/g, respectively. A significant difference (p-value < 0.05) in the mean concentration of Pb in imported rice bran oils samples was observed. The sum of incremental lifetime cancer risk (ILCR) for heavy metals for children and adults were 2.6 × 10⁻⁴ and 2.4 × 10⁻⁵, respectively, which an acceptable level proposed values (10⁻⁴–10⁻⁶) by U.S. EPA. Moreover, the target hazard quotients (THQs) of As, Pb, Cr, Cd, Cu, and Zn for children were limited to between 1.17 × 10^-5 and 9.49 × 10⁻⁹, and in adults were limited to 2.33 × 10⁻⁷and 6.82 × 10^-7, which were lower than the acceptable limit (THQ < 1). There have been concerns regarding heavy metals since past up to now in all foodstuffs. We demonstrated in this study that there are traceable concentrations of heavy metals in six brand of rice bran oils.     

Heterocyclic aromatic amines in grilled beef: The influence of free amino acids,nitrogenous bases,nucleosides, protein and glucose on HAAs content

The aim of the study was to determine the content and profile of heterocyclic aromatic amines (HAAs) formed during the process of grilling beef under various conditions and involving different cuts of beef meat. 4,8-DiMeIQx was the most prevalent (4.50–7.55 ng g⁻¹) the next were: MeIQx (1.10–7.20 ng g⁻¹), MeIQ (1.70–5.30 ng g⁻¹), and IQ (0.38 2.00 ng g⁻¹). Changes in HAAs content, depending on the chemical composition of beef meat, were investigated; the compounds under analysis included free amino acids, glucose and protein as well as free nitrogenous bases and their nucleosides. It was demonstrated that HAAs formation strongly correlates with the presence of various amino acids in raw beef as well as that of glucose and protein (correlation coefficient 0.84–0.93). It was also demonstrated that free purine bases, pyrimidine bases and their nucleosides, which had never previously been studied in terms of their role as substrates for HAAs synthesis, correlate very strongly with HAA formation in grilled beef (correlation coefficient 0.78–0.99). The influence of thermal processing at high temperatures on the thermal decomposition of aminoimidazoazaarenes has not been corroborated by the present study.     

Determination of clothianidin in food products by using an automated system with photochemically induced fluorescence detection

A flow-through system based on the integration of solid-phase spectroscopic detection implemented with photochemically induced fluorescence (PIF) is proposed for the determination of clothianidin (a non-fluorescent neonicotinoid insecticide) through a multicommutated method. The pesticide is injected into the carrier stream (0.015 mol L⁻¹C₂H₄O₂/NaC₂H₃O₂, pH = 5.0) and flows towards a homemade photoreactor, which consists of a PTFE tubing loosely coiled around a low-pressure mercury lamp (15W). After the photochemical reaction of clothianidin, the generated fluorescent photoproduct is transported to a flow cell packed with Sephadex-SP C-25 where it is retained and monitored (λ_ex = 357 nm/λ_em = 418 nm). The method presents a detection limit of 1.5 ng mL⁻¹, a sample throughput of 23 h⁻¹ and inter-day relative standard deviation lower than 3%. The described system has been satisfactorily applied to the determination of clothianidin in samples of drinking water, rice and honey. Taking into account that the maximum residue limit specified in the Codex Alimentarius Commission for rice grains is 0.5 mg kg⁻¹, recovery experiments have been carried out for clothianidin concentrations in the 0.3-10.0 mg kg⁻¹ range.     

Distribution of essential and non-essential elements in rice located in a Protected Natural Reserve “Marjal de Pego-Oliva”

Anthropogenic agronomic practices could negatively affect the agricultural soil which is the main source for inorganic arsenic (i-As) contamination in rice fields due to flooding. The presence of essential elements could be impacted by food industry units operations. The aim of this study was to evaluate the effect of husking and polishing on mineral essential elements and inorganic As species in rice from Protected Natural Reserve “Marjal de Pego-Oliva”. The amount of all studied elements was significantly affected by husking (a decrease of Ca, Na and Pb, 360 to 101 mg kg⁻¹, 202 to 46.9 mg kg^-1 and 17.9 to 5.70 μg kg⁻¹, respectively) and by polishing (a reduction of Na, Mg, P, K, Ca and Cu, 46.9–26.8 mg kg⁻¹, 1600 to 481 mg kg⁻¹, 4050 to 1530 mg kg⁻¹, 2780 to 882 mg kg⁻¹, 101 to 53.7 mg kg⁻¹, and 3600 to 2840, μg kg⁻¹, respectively).The replacement of white rice (WR) to brown rice (BR) could enhance the daily dietary intake of essential elements to reach the dietary reference values and the maximum i-As (40.9 and 44.9 i-As μg kg^-1 for BR and WR, respectively) was below the maximum level recently established by European Food Safety Agency.