Simultaneous pre-concentration of Pb and Sn in food samples and determination by atomic absorption spectrometry

A cloud point extraction (CPE) method has been developed for the pre-concentration and simultaneous determination of lead [Pb(II)] and tin [Sn(II)] using Acridine Orange as complexing reagent and mediated by nonionic surfactant (Triton X-114) by flame atomic absorption spectrometry (FAAS). The main factors affecting analytical performance of CPE have been investigated in detail. The extracted surfactant-rich phase was diluted with (1.0 mol L^?1) nitric acid in methanol, prior to subjecting FAAS. The calibration graphs obtained from Pb(II) and Sn(II) were linear in the concentration ranges of 5–1,000 and 10–5,000 μg L^?1 with detection limits of 1.40 and 2.86 μg L^?1, respectively. The relative standard deviations for 10 replicates containing 25 μg L^?1 of Pb(II) and Sn(II) were 2.15 and 2.50 %, respectively. The analytical procedure was verified by the analysis of the standard reference materials NWTMDA-61.2 (water-trace elements) and NIST SRM 1548a (typical diet). The developed method has been applied to the simultaneous determination of total Pb and Sn in canned food samples including juices, tomato paste, corn, and green pea.     

Optimized Dispersive Liquid–Liquid Microextraction and Determination of Sorbic Acid and Benzoic Acid in Beverage Samples by Gas Chromatography

A new rapid method for direct determination of trace levels of sorbic and benzoic acids was developed by dispersive liquid–liquid microextraction and gas chromatography with flame ionization detection. In the proposed approach, the separation procedure of sorbic and benzoic acids was performed on a general chromatographic column without any prior derivatization processes. Some effective parameters on the microextraction recovery were studied and optimized utilizing multilevel factorial and central composite experimental designs. The best concurrent extraction efficiency acquired using ethanol and chloroform as dispersive and extraction solvents. Central composite design (CCD) resulted in the optimized values of microextraction parameters as follows: 1.0 mL of dispersive and 0.1 mL of extraction solvents, ionic salt concentration of 50 g?L^?1 at pH 4. Under optimum conditions, the calibration curve was linear over the range 0.5–20 mg L^?1. Relative standard deviation was 11% and 13% for five repeated determinations for sorbic and benzoic acids, respectively. Limits of detection were acquired as 0.2 mg L^?1 for sorbic acid and 0.5 mg L^?1 for benzoic acid. The average recoveries were 31% and 39% for sorbic and benzoic acids, respectively. The method was successfully applied to the determination of sorbic and benzoic acids as preservatives in beverage samples.     

Preconcentration and Trace Determination of Chromium Using Modified Ionic Liquid Cold-Induced Aggregation Dispersive Liquid–Liquid Microextraction: Application to Different Water and Food Samples

An efficient microextraction procedure based on modified ionic liquid cold-induced aggregation dispersive liquid–liquid microextraction (M-IL-CIA-DLLME) was developed for trace determination of chromium in water and food samples by flame atomic absorption spectrometry (FAAS), and it was used for speciation of Cr(III) and Cr(VI) in water samples by using Na₂SO₃ as the reducing agent. A mixture of water-immiscible 1-hexyl-3-methylimidazolium hexafluorophosphate ([Hmim][PF₆]) ionic liquid (IL) (microextraction solvent) and ethanol (disperser solvent) were directly injected into a heated aqueous solution containing bis(2-methoxy benzaldehyde) ethylene diimine as a Schiff’s base ligand (chelating agent), hexafluorophosphate (NaPF₆; as a common ion) and Cr(III). Afterwards, the solution was placed in an ice-water bath and a cloudy solution was formed due to a considerable decrease of IL solubility. After centrifuging, the sedimented phase containing enriched analyte was determined by FAAS. Under the optimum conditions, the calibration graph was linear over the range of 2–50 μg?L^?1 with limit of detection of 0.7 μg?L^?1. The accuracy of the present methodology was tested by recovery experiments and by analyzing a certified reference material. Relative standard deviation (RSD %) was 2.7 % for Cr(III). The proposed method was successfully applied for trace determination of chromium in water and food samples.     

Determination of Quercetin, Gallic Acid, Resveratrol, Catechin and Malvidin in Brazilian Wines Elaborated in the Vale do São Francisco Using Liquid–Liquid Extraction Assisted by Ultrasound and GC-MS

In this work, a fast and simple methodology has been applied for the determination of gallic acid, resveratrol, catechin and malvidin in Brazilian wines by gas chromatography–mass spectrometry. The procedure included a stage of ultrasound-assisted liquid–liquid extraction and subsequent derivatization with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and GC-MS analysis. The limit of detection varied from 0.41 to 1.18 mg?L^?1 in all the analytes. The relative standard deviations calculated for 8.0 and 20 mg?L^?1 were 1.90 and 0.82 % for gallic acid, 3.08 and 1.22 % for catechin, 1.30 and 0.44 % for malvidin, 1.50 and 0.53 % for resveratrol, and 1.41 and 0.61 % for quercetin. The developed methodology was applied for the analysis of red wine samples collected in the São Francisco region, Bahia state, Brazil. Quercetin concentration varied from 2.4 to 3.0 mg?L^?1, gallic acid 21.4–56.3 mg?L^?1, resveratrol 1.5–5.9 mg?L^?1, malvidin 15.3–32.2 mg?L^?1, and catechin 11.71–18.2 mg?L^?1. The obtained concentrations are in agreement with those reported in the literature.     

Phytochemical Polyphenol Extraction and Elemental Composition of Vitis labrusca L. Grape Juices Through Optimization of Pectinolytic Activity

Grape juice is a natural source of polyphenols with potential health benefits. The aim of this study was to assess the optimized basis of the pectinolytic activity through a multivariate design for the bioactive enrichment of polyphenols in grape juices and to evaluate the effect of pectinases on the extraction of minerals by ICP-MS and FAAS. Grape juices were treated with pectinases Everzym® Color and Rapidase® Smart at different conditions of enzyme concentration (0.16–1.84 g L^?1), temperature (14.8–83.6?ºC), and incubation time (9.6–110.5 min), and the effect on total phenolics, anthocyanin content, and antioxidant activity of juices were determined by employing a second-order central composite design in combination with response surface methodology. The different conditions showed significant variations in polyphenol levels of grape juices. For both of the enzymes, the increase of temperature and enzyme concentration led to a higher extraction of polyphenols, with a significant effect. Estimated effects depict a good correlation among dependent variables. For Rapidase, the optimized extraction of polyphenols was determined at an enzyme concentration of 1.57 g L^?1 and at a temperature of 54.8?ºC. For Everzym, higher concentrations of polyphenols were obtained at the enzyme concentration of 1.30 g L^?1 at 46.8?ºC. The extraction using the Rapidase enzyme significantly increased the levels of Na, K, Mg, and Fe in grape juices (p?<?0.05). The pectinolytic activity increased the polyphenol and mineral concentrations in grape juices. In addition, the optimal conditions of the pectinolytic treatment comprise a feasible alternative to improve the bioactive potential of grape juices.     

Carbon Nanotube–Ionic Liquid (CNT–IL) Nanocamposite Modified Sol-Gel Derived Carbon-Ceramic Electrode for Simultaneous Determination of Sunset Yellow and Tartrazine in Food Samples

Carbon-ceramic electrode modified with multi-walled carbon nanotubes–ionic liquid (MWCNTs–IL) nanocomposite was constructed. This electrode was used for electrochemical determination of food dyes Sunset Yellow (SY) and tartrazine (Tz). The modified electrode based on high surface area and high ionic conductivity of nanocomposite exhibited electrocatalytic effect for oxidation of SY and Tz; also, oxidation peak potentials of SY and Tz effectively separated on modified electrode, and their simultaneous determination was possible. Operational parameters, such as the amount of MWCNTs in suspension, IL volume, solution pH, and scan rate, which affect the analytical performance of determination, were optimized. The present electrode behaved linearly to Sunset Yellow and tartrazine in the concentration range of 4?×?10^?7 to 1.1?×?10^?4?M and 3?×?10^?6 to 0.7?×?10^?4?M with a detection limit of 10^?7?M (0.045 mg?L^?1) and 1.1?×?10^?6?M (0.59 mg?L^?1), respectively. The proposed method was successfully utilized for simultaneous determination of SY and Tz in different food samples, and the obtained results were in good agreement to those obtained by HPLC method.     

A Rapid Quantification of β-Carotene in Fruits and Vegetables by Dispersive Liquid–Liquid Microextraction Coupled with UV–Vis Spectrophotometry: Optimized by Response Surface Methodology

A simple, fast, and efficient method consisted of optimized dispersive liquid–liquid microextraction (DLLME) followed by UV–vis spectrophotometry was developed for determination of β-carotene in fruits and vegetables. Chloroform and methanol were chosen as extraction and disperser solvents, respectively. The extraction process was optimized using a central composite design (CCD) with the optimum points of 115 μL for volume of extraction solvent and 6.5 % (w/v) for salt concentration. Under the optimal conditions, the relative standard deviation (RSD, C?=?500 μg L^?1, n?=?5), limit of detection (LOD), linear dynamic range (LDR), and coefficient of determination (R²) were 1.08 %, 2 μg L^?1, 50–1,500 μg L^?1, and 0.991, respectively. The present method consisted of a simple and fast sample preparation procedure without any antioxidant addition, saponification, and purification was used.     

Comparison of four analytical techniques based on atomic spectrometry for the determination of total tin in canned foodstuffs

Different techniques for the determination of total tin in beverages and canned foods by atomic spectrometry were compared. The performance characteristics of inductively coupled plasma-mass spectrometry (ICP-MS), hydride generation-inductively coupled plasma-atomic emission spectrometry (HG-ICP-AES), electrothermal atomisation-atomic absorption spectrometry (ETA-AAS) and inductively coupled plasma-atomic emission spectrometry (ICP-AES) were determined in terms of linearity, precision, recovery, limit of detection, decision limit (CCα) and detection capability (CCβ) (Decision 2002/657/EC). Calibration ranges were covered from ng?l^?1 to mg?l^?1 level. Limits of detection that ranged from 0.01, 0.05, 2.0 to 200?µg?l^?1 were reached for ICP-MS; HG-ICP-AES; ETA-AAS and ICP-AES, respectively. Precision, calculated according to ISO 5725-2 for repeatability and within-laboratory reproducibility and expressed as relative standard deviation (RSD), ranged from 1.6% to 4.9%; and recovery, based on Decision 2002/657/EC, was found to be between 95% and 110%. Procedures for the mineralisation or extraction of total tin were compared. Wet digestion, sequentially, with nitric acid and hydrogen peroxide provided the best results. The influence of possible interferences present in canned food and beverage was studied, but no interference in the determination of tin was observed. Since maximum levels for tin established by European Union legislation vary from 50?mg?kg^?1 in canned baby foods and infant foods up to 200?mg?kg^?1 in canned food, ICP-AES was chosen as the preferred technique for routine analysis thanks to its good precision, reliability and ease of use. The accuracy of this routine method was confirmed by participation in six proficiency test schemes with z-scores ranging from ?1.9 to 0.6. Several canned foodstuffs and beverage samples from a local market were analysed with this technique.     

Determination of Triazole Fungicides in Liquid Samples Using Ultrasound-Assisted Emulsification Microextraction with Solidification of Floating Organic Droplet Followed by High-Performance Liquid Chromatography

An ultrasound-assisted emulsification microextraction with solidification of organic droplet method followed by high-performance liquid chromatography with diode array detection for six triazole fungicide determination (diniconazole, fluquinconazole, flusilazole, myclobutanil, tebuconazole, and tetraconazole) was developed. After some preliminary experiments, undecanol was chosen as extracting solvent using 50 μL for 10 mL of liquid sample. A central composite design was performed to obtain the best experimental conditions for the following variables NaCl concentration (250 g L^?1), extraction time (18 min), and temperature (30 °C) in ultrasonic bath. After the ultrasound-assisted extraction, two steps considering centrifugation (4,200 rpm, 10 min) and solidification (5 min, 3 °C) were done. Following these conditions, the method showed linearity higher than 0.9930 with the concentration ranged from 20 to 890 μg L^?1. The limits of detection obtained using calibration curves were from 10.9 to 17.2 μg L^?1 and the intra- and inter-day repeatability at two levels showed RSD values between 1.9 and 10.6 %. The enrichment factors for the studied triazoles were between 226 (flusilazole) and 255 (tebuconazole). Recovery studies at two spiked levels in apple and grape juices gave values from 64 to 112 %.     

Enhancing Fluorescence LC Analysis of Biogenic Amines in Fish Tissues by Precolumn Derivatization with Naphthalene-2,3-dicarboxaldehyde

This work reports a sensitive high-pressure liquid chromatography method for the simultaneous determination of biogenic mono- and diamines in fish tissues. Highly fluorescent derivatives of the amines were obtained by precolumn derivatization with naphthalene-2,3-dicarboxaldehyde, in the presence of cyanide ion as the nucleophile and of heptylamine as the internal standard. The chromatographic separation was performed using a mobile phase of acetonitrile/methanol/10 % (v/v) acetone in water, delivered in gradient mode on an Inertsil ODS-3 column (250?×?4 mm i.d., 5 μm). The method was successfully applied to the analysis of fresh and canned tuna fish tissues, subjected to ultrasound-assisted liquid–liquid extraction. The variables affecting the derivatization yield as well as the extraction recovery of the analytes from the sample matrix were investigated. Results were quantified against the internal standard, according to the matrix-matched approach. Limits of detection between 2.5 and 330 mg kg^?1 sample were achieved. The precision and accuracy of assay in samples was satisfactory, yielding relative standard deviation and recovery values between 0.3 and 4.2 % and 81.0 and 102.5 %, respectively.     

Preconcentration and Simultaneous Analysis of Benzimidazole Anthelmintics in Milk Samples by Ultrasound-Assisted Surfactant-Enhanced Emulsification Microextraction and High-Performance Liquid Chromatography

The proposed ultrasound-assisted surfactant-enhanced emulsification microextraction (UASEME) coupled with high-performance liquid chromatography-photodiode array detection (HPLC-PDA) has been developed for the preconcentration and simultaneous analysis of five benzimidazole anthelmintics. Dichloromethane (extraction solvent) and Triton X-114 (emulsifier) was used for extraction of the target analytes. The parameters affecting the extraction efficiency were investigated and optimized. Under the optimum conditions, linearity was in the range from 10 to 150 μg?L^?1 with good coefficients of determination (R ²) higher than 0.994. Preconcentration factors were obtained up to 60, corresponding to limits of detection range of 1.8???3.6 μg?L^?1. Intra-day (n?=?5) and inter-day (n?=?4?×?3) precisions were obtained with relative standard deviation of retention time and peak area below 0.8 and 9.2 %, respectively. Good recoveries for the spiked target anthelmintics at different concentrations (e.g., 20, 50, and 100 μg?L^?1) of milk samples were obtained in 72.5–113.5 %. The results demonstrated that the proposed UASEME-HPLC-PDA can be used as an alternative powerful method for the simultaneous determination of the target analytes in milk samples.     

Preconcentration of trace levels of cadmium (ІІ) ion using <Emphasis Type="Italic">Descurainia Sophia</Emphasis> seeds as a green adsorbent for solid phase extraction followed by its determination by flame atomic absorption spectrometry

For the first time, Descurainia Sophia (DS) seeds as an efficient and green adsorbent were used in solid phase extraction for preconcentration of trace levels of cadmium prior to its determination by flame atomic absorption spectrometry (FAAS). By using a batch method, Descurainia Sophia seeds were used as adsorbent to retain cadmium (??) ions in the sample solution. After eluting the adsorbent with 3 mol L^?1 HCl, the retained cadmium (??) was determined by flame atomic absorption spectrometry. Different parameters affecting the extraction efficiency such as pH, amounts of adsorbent, type and concentration of eluent solvent, extraction and desorption time were investigated and optimized. Under the optimum conditions, the calibration curve was linear in the range of 5–300 µg L^?1 cadmium (??) with a correlation coefficient of 0.998. The limit of detection (LOD) was 1.0 µg L^?1 and the relative standard deviation (RSD, %) based on seven replicate analysis of 25 µg L^?1 cadmium (??) was 3.2%. The accuracy of the proposed method was checked by the analysis of certified reference material (CRM) and spike methods. The results show a good agreement with certified values. The proposed method was successfully applied to determination of trace levels of cadmium in different water and rice flour samples.     

Hollow Fiber Liquid Phase Microextraction Method Combined with High-Performance Liquid Chromatography for Simultaneous Separation and Determination of Ultra-Trace Amounts of Naproxen and Nabumetone in Cow Milk,Water, and Biological Samples

A simple and highly sensitive method based on hollow fiber liquid phase microextraction combined with high-performance liquid chromatography and fluorescence detection has been developed for simultaneous separation, preconcentration, and determination of naproxen and nabumetone from water, wastewater, milk, and biological samples. Parameters affecting the microextraction efficiency were evaluated and optimized. Under optimum conditions (extractant (14 μL of 1-undecanol), sample pH (3.0), extraction time (20 min), stirring rate (600 rpm), temperature (45 °C), potassium chloride concentration (4.0 %) and sample volume (9 mL)), the limits of detection based on (S/N?=?3) were 1.3 ng L^?1 for naproxen and 2.9 ng L^?1 for nabumetone. The intra- and inter-assay relative standard deviations for naproxen and nabumetone were in the ranges of 3.2–6.1 % and 6.5–9.5 %, respectively. The calibration curves were linear in concentration ranges of 4.0–300.0 ng L^?1 and 9.0–300.0 ng L^?1 for naproxen and nabumetone, respectively, with good coefficient of determination (r ²?>?0.999). The method was successfully applied to the determination of naproxen and nabumetone in cow milk, water, wastewater, human plasma, and urine samples.     

Simultaneous Determination of Nitrate and Nitrite in Fish Products with Improved Sensitivity by Sample Stacking-Capillary Electrophoresis

A fast and reproducible method for the simultaneous determination of nitrate and nitrite ions in canned fish samples by capillary zone electrophoresis has been developed. The sensitivity of the method was increased by applying a sample stacking technique. Optimal separation conditions were selected as 30 mmol L^?1 formic acid and 30 mmol L^?1 sodium sulfate at a pH of 4.0. The separation of nitrate and nitrite ions was achieved within 2.5 min. The limits of detection obtained at a signal-to-noise ratio of 3 for nitrate and nitrite were 0.55 and 0.82 μmol L^?1, while the relative standard deviations of intra-day corrected peak areas were 0.99 and 2.74 %, respectively. Recovery values ranged between 88.7 and 104 % for both ions. The method was successfully applied to canned fish samples, namely tuna, mackerel and sardine.     

Determination of Rutin in Black Tea by Adsorption Voltammetry (AdV) in the Presence of Morin and Quercetin

This paper presents a sensitive method to rutin determination on a screen-printed multi-walled carbon nanotube electrode modified with poly(3,4-ethylenedioxythiophene) and ionic liquid (SMWCNT-PEDOT-IL). Several studies show that rutin may be absorbed onto the surface of electrodes modified with PEDOT. On the other hand, the presence of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF₄) on the surface of the modified electrode increased the oxidation current by nearly 30 % and facilitates the oxidation of rutin to values less positive potential compared with the modified electrode only with PEDOT. Cyclic voltammetry was used to quantify and characterize the modified electrode. pH and electrochemical parameters, potential adsorption, time adsorption, and scan rate were optimized based on the oxidation of rutin to obtain the following values: pH 6.0; Eads, ?0.10 V; tads, 80 s; and scan rate 50 mV s^?1. The detection limit (3σ) was 7.7?×?10^?8 mol L^?1 and the RSD was 1.5 %. The new method was used to quantify rutin in black tea samples in the presence of others flavones with consistent results.     

Application of Ion-Imprinted Polymer Nanoparticles for Selective Trace Determination of Palladium Ions in Food and Environmental Samples with the Aid of Experimental Design Methodology

A solid phase extraction method using Pd²⁺ ion-imprinted polymer (Pd²⁺-IIP) nanoparticles combined with flame atomic absorption spectrophotometry (FAAS) was developed for the preconcentration and trace detection of palladium ions. The Pd²⁺-IIP nanoparticles were obtained by precipitation polymerization of 4-vinylpyridine (the functional monomer), ethylene glycol dimethacrylate (the cross-linker), 2,2′-azobisisobutyronitrile (the initiator), Eriochrome Cyanine R (the lead-binding ligand), and palladium ions (the template ion) in acetonitrile solution. The parameters affecting adsorption and desorption steps were optimized by a Box–Behnken design through response surface methodology. Three variables (pH value, extraction time, and amount of the synthesized IIP) were selected as the main factors affecting sorption step, while four variables (type of eluent, volume of the eluent, concentration of the eluent, and elution time) were selected for desorption step in the optimization study. The optimized values by this optimization method were 30 mg, 15 min, 6.0, HCl, 4.0 mL, 1.8 mol L^-l HCl, and 14 min, for amount of polymer, retention time, pH of solution, type, volume, concentration of the eluent, and elution time, respectively. Under the optimized conditions, the detection limit for the proposed method was found to be 0.2 μg L^?1, while the relative standard deviation (RSD) for five replicate measurements was calculated to be <3 %. Finally, the introduced solid phase extraction technique was successfully applied for extraction and determination of Pd²⁺ ions in food and environmental samples.     

Novel Binary Solvents-Dispersive Liquid—Liquid Microextraction (BS-DLLME) Method for Determination of Patulin in Apple Juice Using High-Performance Liquid Chromatography

A simple and rapid binary solvents-based dispersive liquid–liquid microextraction (BS-DLLME) method has been developed for determination of patulin (PAT) in apple juice followed by high-performance liquid chromatography. This method involves the use of an appropriate mixture of miscible binary extraction solvents and disperser solvent to form fine droplets of extractant in a sample solution. Parameters affecting extraction efficiency such as the type and volume of high-density extraction solvent, the volume of ethyl acetate, the kind and volume of disperser solvent, and salt addition were investigated and optimized. The detection and quantification limits were 2.0 and 10.0 μg L^?1, respectively. The relative standard deviation for five measurements of 25 μg L^?1 of PAT was 3.8 %. The relative recoveries of PAT from apple juice samples at spiking levels of 25, 50, and 75 ng mL^?1 were in the range of 91.3–95.2 %.     

Development of a Headspace-Solid Phase Microextraction-Gas Chromatography/Mass Spectrometry (HS-SPME-GC/MS) Method for the Determination of Benzene in Soft Drinks

A method based on headspace-solid phase microextraction and gas chromatography with mass spectrometry has been developed and validated for the determination of benzene in soft drinks. The extraction step was optimized using a rotatable central composite design including the following experimental variables: extraction temperature, extraction time, sample weight, and salt concentration. The optimized procedure, which was carried out at 30 °C during 30 min by using a 75 μm carboxen-polydimethylsiloxane fiber, showed good linearity within the concentration range 0–25 μg?kg^?1 (r ² ?>?0.999), mean recoveries from 97.5 to 103.1 %, and coefficients of variation from 1.5 to 13.4 % for repeatability and from 1.5 to 15.7 % for within-laboratory reproducibility. Limits of detection and quantification were calculated at 0.02 and 0.08 μg?kg^?1, respectively. The method was applied to determine the concentrations of benzene in 77 samples of beverages from the Brazilian market. Levels from <0.08 to 10.84 μg?kg^?1 were obtained, which are comparable to those verified in other countries. Most of the samples (72.2 %) contained benzene up to 1 μg?kg^?1.     

Speciation of Inorganic Antimony in Food and Water Samples by Flow Injection On-line Nano γ-Alumina Micro-column Solid-Phase Extraction Coupled with Slotted Tube Atom Trapping Flame Atomic Absorption Spectrometry

Nano γ-alumina, with ultra-high specific surface area (387.2 m²?g^?1), has been synthesized and used as a promising adsorbent material in solid-phase extraction. A simple, sensitive, and economic method was developed for speciation of inorganic antimony by slotted tube atom trapping flame atomic absorption spectrometry (STAT-FAAS) after flow injection on-line nano γ-alumina micro-column solid-phase extraction. In this method, Sb(III)–diethyldithiocarbamate (DDTC) complexes produced on-line from DDTC and Sb(III) were adsorbed by the synthesized γ-alumina nanoparticles in a micro-column, then eluted by 1.0 mol?L^?1 HNO₃ in methanol, whereas Sb(V) remained in aqueous solution. The total inorganic Sb was determined by the same procedure after Sb(V) was reduced with thiourea. Under optimal conditions, the enrichment factor was 56.5 and the detection sensitivity was improved 40-fold for antimony by STAT-FAAS compared to conventional FAAS. The limit of detection was 6.0 ng?L^?1 for Sb(III) and 8.2 ng?L^?1 for Sb(V), respectively. The intra-day precision (RSDs, n?=?11) were 2.8 % for Sb(III) and 3.5 % for Sb(V), respectively, and the inter-day precision (n?=?3) were 7.1 % for Sb(III) and 8.4 % for Sb(V), respectively. The recoveries for the spiked samples were 93–107 %. The proposed method was applied to speciation of inorganic antimony in water and food samples successfully.     

Application and Optimization of Microwave-Assisted Extraction and Dispersive Liquid–Liquid Microextraction Followed by High-Performance Liquid Chromatography for the Determination of Oleuropein and Hydroxytyrosol in Olive Pomace

In the present study, a new method based on microwave-assisted extraction and dispersive liquid–liquid microextraction (MAE–DLLME) followed by high-performance liquid chromatography (HPLC) was proposed for the separation and determination of oleuropein (Ole) and hydroxytyrosol (HyT) from olive pomace samples. The effective factors in the MAE–DLLME process such as microwave power, extraction time, the type and volume of extraction, and dispersive solvents were studied and optimized with the aid of response surface methodology (RSM) based on a central composite design (CCD) to obtain the best condition for Ole and HyT extraction. At the optimized conditions, parameter values were 220 W microwave power, 12 min extraction time, 60 μL extracting solvent, and 500 μL dispersive solvent. The calibration graphs of the proposed method were linear in the range of 10–500,000 μg L^?1, with the coefficient of determination (R²) higher than 0.99 for Ole and HyT. Repeatability of the method, described as the relative standard deviation (RSD), was 4.12–5.63% (n?=?6). The limits of detection were 35 and 20 μg L^?1 for Ole and HyT, respectively. The recoveries of these compounds in the spiked olive pomace sample were from 93 to 98%. The proposed method, MAE–DLLME–HPLC–UV, was an accurate, rapid, and reliable method when compared with previous methods.