Resonance Rayleigh scattering spectra of tetracycline antibiotic–Cu(II)–titan yellow systems and their applications in analytical chemistry

Tetracycline antibiotics (TCs) such as doxycycline (DOTC), chlortetracycline (CTC), oxytetracycline (OTC), and tetracycline (TC) react with Cu(II) in pH 3.5 BR buffer medium to form 1:1 cationic chelates, which further react with titan yellow to form 2:1 ion association complexes. These result in great enhancement of resonance Rayleigh scattering (RRS) and the appearance of new RRS spectra. The ion association complexes of DOTC, CTC, OTC, and TC have similar spectral characteristics and their maximum RRS wavelengths are all located at 464 nm. The quantitative determination ranges and the detection limits (3σ) of the four TCs are 0.037–4.8 μg mL⁻¹ and 11.2 ng mL⁻¹ for DOTC, 0.041–5.2 μg mL⁻¹ and 12.4 ng mL⁻¹ for CTC, 0.050–4.8 μg mL⁻¹ and 15.1 ng mL⁻¹ for TC, and 0.088–5.0 μg mL⁻¹ and 26.3 ng mL⁻¹ for OTC, respectively. The optimum reaction conditions, the effects of foreign substances, the structure of ternary complexes, and the reaction mechanism are discussed. A sensitive, rapid, and simple RRS method for the determination of DOTC has been developed.     

Capillary zone electrophoresis determination of oxytetracycline in pig tissue samples at maximum residue limits

Summary The determination of the antibiotic oxytetracycline (OTC), in pig tissues was investigated by capillary zone electrophoresis (CZE) with a prior solid-phase extraction (SPE) using alkyl-bonded silica and polymeric cartridges. The methodology developed allows determination of OTC in pig kidney, liver and muscle samples with detection limits below maximum residue limit values, and the procedures to extract OTC and clean-up the matrix are simple and reliable. The limit of detection for OTC was 160, 120 and 85 μg kg⁻¹ for kidney, liver and muscle samples, respectively. The average recoveries from spiked samples (200 μg kg⁻¹ and 1600 μg kg⁻¹) were in excess of 63% with coefficients of variation between 2.0 and 9.8%. This method would be useful for routine monitoring of oxytetracycline residues in pig tissues.     

Determination of antibacterials in animal feed by pressurized liquid extraction followed by online purification and liquid chromatography-electrospray tandem mass spectrometry

A fully automated method has been developed for analysis of eighteen antibacterial compounds, including penicillins, cephalosporins and sulfonamides, in animal feed with limits of quantification in the range 0.25–5.79 μg kg⁻¹. The method is based on pressurized liquid extraction of 3 g homogenized feed with water and online clean-up of 500 μL of the extract with C₁₈HD cartridges. The purified sample was directly analysed by liquid chromatography–electrospray tandem mass spectrometry (SPE–LC–ESI-MS–MS). Chromatographic separation was achieved within 10 min by use of a C₁₂ Phenomenex Hydro-RP reversed-phase analytical column and a mobile phase gradient (water + 0.1% formic acid–methanol + 0.1% formic acid). The method was validated, revealing capability for detection of concentrations as low as 0.09 μg kg⁻¹, decision limits (CCα) and detection capabilities (CCβ) in the range 10–174 μg kg⁻¹ and 22–182 μg kg⁻¹, respectively, and inter-day precision ranging from 0.7 to 8.3%. Recovery, with internal standard correction, was in the range 93–134% for all analytes. The method was then applied to analysis of fifteen feed samples, nine of which contained at least one antimicrobial at concentrations between 0.006 and 1.526 mg kg⁻¹. The performance data and results from the method were compared with those from a previous method developed by our group, using offline SPE, by analyzing the same set of samples by both methods. The online SPE approach resulted in slightly improved sensitivity, with LODs of 0.09–2.12 μg kg⁻¹ compared with 0.12–3.94 μg kg⁻¹ by the offline approach. In general, better recovery was achieved by use of online purification (for 72% of the analytes) and the correlation between the two methods was good. The main advantages of the new online method are rapid and automated sample pre-treatment, and reduction of sample manipulation, enabling high-throughput analysis and highly accurate results. Because of all these characteristics, the proposed method is applicable and could be deemed necessary within the field of food control and safety.     

Simplified liquid-chromatographic determination of residues of tetracycline antibiotics in eggs

Summary A high-performance liquid chromatographic (HPLC) procedure is described for the identification and quantification of residues of tetracycline antibiotics (TCA) (oxytetracycline, tetracycline, chlortetracycline, and doxycycline), in eggs. Spiked and blank samples were prepared by homogenization with 1∶1 (v/v) acetonitrile-mixed Mcllvaine buffer and EDTA solution (pH 4.0) then centrifugal ultrafiltration. HPLC was performed on a reversed-phase column with acetonitrile-5% (v/v) aqueous acetic acid, 35∶65 (v/v), as mobile phase and photo-diode array detection. Average recoveries (each drug spiked at 0.1, 0.2, 0.3, 0.5 and 1.0 μg g⁻¹) were >-77% with standard deviations (SD) between 1.5 and 3.5%. The inter-assay variabilities and theirSD were <3.4% and <0.7%, respectively, and intra-assay variability was between 2.0 and 3.9%. The limits of quantitation (LOQ) were 0.064 0.087, 0.121, and 0.131 μg g⁻¹ for OTC, TC, CTC, and DC, respectively. The total time required for the analysis of one sample was less than 30 min.     

Rapid residue analysis of four triazolopyrimidine herbicides in soil, water, and wheat by ultra-performance liquid chromatography coupled to tandem mass spectrometry

A sensitive and effective method for simultaneous determination of triazolopyrimidine sulfonamide herbicide residues in soil, water, and wheat was developed using ultra-performance liquid chromatography coupled with tandem mass spectrometry. The four herbicides (pyroxsulam, flumetsulam, metosulam, and diclosulam) were cleaned up with an off-line C18 SPE cartridge and detected by tandem mass spectrometry using an electrospray ionization source in positive mode (ESI+). The determination of the target compounds was achieved in <2.0 min. The limits of detection were below 1 μg kg⁻¹, while the limits of quantification did not exceed 3 μg kg⁻¹ in different matrices. Quantitation was determined from calibration curves of standards containing 0.05–100 μg L⁻¹ with r ² > 0.997. Recovery studies were conducted at three spiked levels (0.2, 1, and 5 μg kg⁻¹ for water; 5, 10, and 100 μg kg⁻¹ for soil and wheat). The overall average recoveries for this method in water, soil, wheat plants, and seeds at three levels ranged from 75.4% to 106.0%, with relative standard deviations in the range of 2.1–12.5% (n = 5) for all analytes.     

Comparison of adsorbents for on-line solid-phase extraction of polycyclic aromatic hydrocarbons before liquid chromatography with UV detection

Summary On-line solid-phase extraction (SPE) coupled with reversed-phase liquid chromatography and UV detection at 254 nm has been used for the determination of trace-level polycyclic aromatic hydrocarbons (PAH) in soil extracts. Five commercially available adsorbents (C₈, C₁₈, PLRP-S, PRP-1, and Bond-Elut Env) were evaluated. Results showed that recovery of the PAH decreased with increasing molecular weight, because of their poorer solubility. Recovery of high-molecular-weight PAH was significantly improved by addition of 10% (v/v) acetonitrile to the sample before loading of the SPE adsorbent. PAH recovery ranged from 64.0 to 108% when a 50 mL sample spiked with 1 μg L⁻¹ was applied to these adsorbents. Determination of PAH was possible with detection limits below 0.05 μg L⁻¹, which corresponds to 0.2 μg kg⁻¹ soil. The method was successfully used to determine PAH in soil extracts.     

Development and validation of a method for determination of residues of 15 pyrethroids and two metabolites of dithiocarbamates in foods by ultra-performance liquid chromatography-tandem mass spectrometry

This paper reports a novel approach for the detection, confirmation, and quantification of 15 selected pyrethroid pesticides, including pyrethins, and two metabolites of dithiocarbamates in foods by ultra-performance liquid chromatography–tandem mass spectrometry (UPLC–MS–MS). The proposed method makes use of a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) procedure that combines isolation of the pesticides and sample cleanup in a single step. Analysis of pyrethroids and dithiocarbamate metabolites was performed by UPLC–MS–MS operated with electrospray and atmospheric pressure chemical ionization, respectively. Two specific precursor–product ion transitions were acquired per target compound in multiple reaction monitoring (MRM) mode. Such acquisition achieved the minimum number of identification points according to European Commission (EC) document no. SANCO/10684/2009, thus fulfilling the EC point system requirement for identification of contaminants in samples. The method was validated with a variety of food samples. Calibration curves were linear and covered from 1 to 800 μg kg⁻¹ in the sample for all target compounds. Average recoveries, measured at mass fractions of 10 and 100 μg kg⁻¹ for pyrethroids and 5 and 50 μg kg⁻¹ for dithiocarbamate metabolites, were in the range of 70–120% for all target compounds with relative standard deviations below 20%. Method limits of quantification (MLOQ) were 10 μg kg⁻¹ and 5 μg kg⁻¹ for pyrethroids and dithiocarbamate metabolites, respectively. The method has been successfully applied to the analysis of 600 food samples in the course of the first Hong Kong total diet study with pyrethroids and metabolites of dithiocarbamates being the pesticides determined.     

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.     

Detection of residual bacitracin A, colistin A, and colistin B in milk and animal tissues by liquid chromatography tandem mass spectrometry

Liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-MS/MS) was applied to the determination of residual bacitracin A, colistin A, and colistin B in milk and animal tissue samples. Prior to instrumental analysis, samples were subjected to acid extraction followed by solid-phase cleanup using Strata-X cartridges. Mass spectral acquisitions were performed under selective multiple reaction monitoring (MRM) mode at m/z 199 and 670 from triply charged precursors of bacitracin A (m/z 475); m/z 385 and 379 from triply charged precursors of colistin A (m/z 391); and m/z 380 and 374 from triply charged precursors of colistin B (m/z 386). Method precision was evaluated from spike recovery of samples fortified at concentrations corresponding to 2/5 of the maximum residue limits (MRLs) for each of the analytes under study. Intra-day and inter-day variations were found to range from 90.9 to 104% with relative standard deviation (RSD) <6.5%, and from 90.1 to 106% with RSD <9.1%, respectively. Limits of quantification (LOQs) were defined as the spiking concentrations at 2/5 MRL, and limits of detection (LODs) were 10–47 μg kg⁻¹ for bacitracin A, 1–16 μg kg⁻¹ for colistin A, and 6–14 μg kg⁻¹ for colistin B in milk and animal tissues. The presented method has good precision and high sensitivity and was applied as a fast screening protocol and a quantitative tool for monitoring of the concerned polypeptides in foods as part of a surveillance program.      

High-performance liquid chromatographic determination/identification of oxytetracycline and sulphadimidine in meat and eggs

Summary A rapid method for the simultaneous determination/identification of residual oxytetracycline (OTC) and sulphadimidine (SDD) in meats (beef, pork, chicken) and eggs by high-performance liquid chromatography (HPLC) was developed. The extraction of OTC and SDD was performed using a Sep-Pak^? CN cartridge. The extracts contained OTC/SDD analytes when examined by HPLC using a LiChrospher^? 100 RP-8 end-capped column and a mobile phase of acetonitrile-acetic acid-water (28:4:68, v/v/v) with a photodiode array detector. The average recoveries from spiked samples (0.1 μg g⁻¹ and 1.0 μg g⁻¹) were in excess of 80.2% with coefficients of variation between 1.5 and 5.0%. The limits of detection for OTC and SDD were 0.05 and 0.02 μg g⁻¹, respectively.     

Quantitative Analysis of Sulfonamide Residues in Natural Animal Casings by HPLC

A multiresidue method has been developed for the simultaneous determination of sulfadiazine, sulfathiazole, sulfapyridine, sulfamerazine, sulfamethoxydiazine, sulfamethylthiazole, sulfamethazine, sulfamonomethoxine, sulfamethoxypyridazine, sulfisoxazole, sulfamethoxazole, sulfadimethoxine and sulfaquinoxaline in natural animal casings by HPLC after solid-phase extraction. The sulfonamides were extracted with acetonitrile and the extract cleaned up with an Oasis MCX SPE cartridge prior to analysis. Separation was on a ZOBAX Eclipse XDB-C₈ column using gradient elution with acetonitrile/methanol/0.1% acetic acid. The effect of separation conditions on chromatographic behavior and recovery has been studied. Calibration graphs were linear with very good correlation coefficients (r = 0.9983−0.9996) in the concentration range from 0.02 to 1 μg mL⁻¹. The limits of quantitation (LOQ) for the 13 sulfonamides were in the range of 1.5–2.2 μg kg⁻¹. Decision limits (CCα) and detection capabilities (CCβ) were in the range of 105.2–111.0 and 113.0–120.2 μg kg⁻¹, respectively. The recovery for casings spiked with 1.5–100 μg kg⁻¹ ranged from 65.2 to 85.9%. The relative standard deviations (RSDs) of the sulfonamides for six measurements at 100 μg kg⁻¹ were from 2.2 to 7.7%. The applicability of the method to the analysis of salted swine casings, salted sheep casings and dry casing samples was demonstrated.     

Multiresidue analysis of atrazine, diuron and their degradation products in sewage sludge by liquid chromatography tandem mass spectrometry

A multiresidue method has been developed to analyze atrazine (ATZ), diuron (DIU), and their major degradation products, desethylatrazine (DEA), desisopropylatrazine (DIA), and dichlorophenylmethylurea in sewage sludge. Liquid chromatography coupled to electrospray tandem mass spectrometry (LC–ESI-MS–MS) allowed, in the multiple-reaction monitoring mode, the simultaneous analysis of these pesticides in only one run after their extraction with ethyl acetate–dichloromethane 90:10 (v/v) and a cleanup on a Florisil column. Stable isotopically labeled ATZ and DIU were used as internal standards to overcome matrix effects during the pesticide quantification. Using fortified samples, the method gave rise to 86–115% as mean recovery values depending on the analyte. Limits of detection (LODs) and of quantification (LOQs) ranging from 0.3 (DIA) to 1.5 (DEA) μg kg⁻¹ dw and from 0.4 (DIA) to 2.0 (DEA) μg kg⁻¹ dw, respectively, were sufficient to achieve the monitoring of these molecules in sludge from wastewater treatment plants of the Ile-de-France region.     

Palytoxin in seafood by liquid chromatography tandem mass spectrometry: investigation of extraction efficiency and matrix effect

Blooms of Ostreopsis spp. have been recently reported along the Mediterranean coasts of Spain, France, Italy, and Greece posing serious risks to human health. Occurrence of Ostreopsis spp. may result in palytoxin contamination of seafood and, in order to prevent sanitary risks, the need exists to develop efficient extraction procedures to be coupled to rapid and sensitive monitoring methods of palytoxin-like compounds in seafood. In the present study, the best conditions for both extraction of palytoxin from seafood and palytoxin quantification by using liquid chromatography tandem mass spectrometry (LC-MS/MS) were investigated. Three seafood matrices (mussels, sea-urchins, and anchovies) were selected and five different extraction systems were tested, namely: the official protocol for extraction of lipophilic toxins and various aqueous methanol or acetonitrile solutions (MeOH/H₂O 1:1, MeOH/H₂O 8:2, MeCN/H₂O 8:2 and MeOH 100%). Extraction with MeOH/H₂O 8:2 provided the best results in terms of accuracy and matrix interference on LC-MS/MS detection of palytoxin. Accuracy and intra-day reproducibility (n = 3) were evaluated for all the selected matrices but only for mussels at three spiking concentration levels, including the provisional limit proposed by the Community Reference Laboratory for marine biotoxins (250 μg kg⁻¹). Limits of quantitation of palytoxin in mussels, sea-urchins and anchovies tissues were calculated using matrix-matched standards; taking into account extraction efficiency of MeOH/H₂O 8:2, they resulted to be 228, 343, and 500 μg kg⁻¹, respectively.     

UV spectrophotometric flow-injection assay of tetracycline antibiotics retained on Sephadex QAE A-25 in drug formulations

A flow injection analysis system with solid phase spectrophotometric transduction has been developed for the assay of tetracycline (TC), doxycicline (DTC), oxycicline (OTC) and chlortetracycline (CTC). The packing material of the flow-through cell consists of Sephadex QAE A-25 resin on which tetracyclines are temporarily retained. The carrier itself acts as the desorbing solution. The measurements of the intrinsic absorbance of tetracyclines (1000 μl of sample volume) were made at 380 nm (TC, DTC and OTC) and 387 nm (CTC). The detection limits were found to be 0.069 (TC and OTC), 0.081 (DTC) and 0.121 (CTC) μg ml⁻¹ and the linear dynamic range extended between 0.5 and 12 (TC, DTC and OTC) and 1–20 μg ml⁻¹ (CTC). The relative standard deviations (n=10) ranged between 0.7 and 1.2%. A study of the potentially interfering species was carried out. Using the proposed method, tetracyclines were satisfactorily determined without any interference from excipients in pharmaceutical preparations.     

A comparative study of extraction apparatus in HPLC analysis of ochratoxin A in muscle

Ochratoxin A (OTA) is a secondary fungal metabolite produced by several moulds, mainly by Aspergillus ochraceus and by Penicillium verrucosum, that occurs in meat products. The aim of this work was to optimize an efficient extraction procedure for the determination of OTA in muscle tissue in order to assess its occurrence in meat samples. Three different apparatus, a Waring blender, a switching apparatus, and an ultrasonic processor, were evaluated to verify the efficiency of extraction. The analytical methods proposed involve the extraction with chloroform-orthophosphoric acid, cleanup through an immunoaffinity column, high-performance liquid chromatography/fluorescence detection for separation and identification of OTA, and confirmation with liquid chromatography/FD after methylation of OTA in muscle tissue. The limit of quantification of the proposed method was 0.04 μg kg⁻¹. Recoveries of OTA, using switching apparatus, ranged from 90.3 to 103.2% for chicken muscle spiked at 2.4 and 0.48 μg kg⁻¹, respectively, with a within-day relative standard deviation of 17 and 15.3%. The proposed method was applied to 38 chicken, swine, and turkey muscle samples and the presence of OTA was confirmed in five samples. Finally, the estimated daily intake of OTA in this study was between 23 pg kg⁻¹ body weight per day for swine samples and 18 pg kg⁻¹ body weight per day for turkey samples.     

Multi-component analysis of tetracyclines, sulfonamides and tylosin in swine manure by liquid chromatography–tandem mass spectrometry

A multi-component method focussing on thorough sample preparation has been developed for simultaneous analysis of swine manure for three classes of antibiotic—tetracyclines, sulfonamides, and tylosin. Liquid manure was initially freeze-dried and homogenised by pulverization before extraction by pressurised liquid extraction. The extraction was performed at 75°C and 2,500 psig in three steps using two cycles with 0.2 mol L⁻¹ citric acid buffer (pH 4.7) and one cycle with a mixture of 80% methanol with 0.2 mol L⁻¹ citric acid (pH 3). After liquid–liquid extraction with heptane to remove lipids, the pH of the manure was adjusted to 3 with formic acid and the sample was vacuum-filtered through 0.6 μm glass-fibre filters. Finally the samples were pre-concentrated by tandem SPE (SAX-HLB). Recoveries were determined for manure samples spiked at three concentrations (50–5,000 μg kg⁻¹ dry matter); quantification was achieved by matrix-matched calibration. Recoveries were >70% except for oxytetracycline (42–54%), sulfadiazine (59–73%), and tylosin (9–35%) and did not vary with concentration or from day-to-day. Limits of quantification (LOQ) for all compounds, determined as a signal-to-noise ratio of 10, were in the range 10–100 μg kg⁻¹ dry matter. The suitability of the method was assessed by analysis of swine manure samples from six different pig-production sites, e.g. finishing pigs, sows, or mixed production. Residues of antibiotics were detected in all samples. The largest amounts were found for tetracyclines (up to 30 mg kg⁻¹ dry matter for the sum of CTC and ECTC). Sulfonamides were detected at concentrations up to 2 mg kg⁻¹ dry matter (SDZ); tylosin was not detected in any samples.      

Simple and rugged SPE method for the determination of tetracycline antibiotics in serum by HPLC using a volatile mobile phase

Summary A simple and rugged SPE method for the determination of tetracycline (TC), minocycline (MC) and demeclocycline (DCC) in porcine serum by high performance liquid chromatography (HPLC) was developed. The spiked serum sample was pretreated with 2% phosphoric acid followed by a simple and rugged solid-phase extraction procedure using the Oasis^TM HLB extraction cartridges. High and reproducible recoveries were obtained even though the cartridges were run dry. The extracted sample analytes were injected onto a Waters SymmetryShield^TM RP₈ column. The mobile phase was a simple volatile solution containing 0.1% TFA, 2% methanol and 7% acetonitrile in Water. The antibiotics were detected at 350 nm. The calibration curves were linear from 2.0 to 25.0 μg mL⁻¹ of TC and MC with DCC as the internal standard at a concentration of 25.0 μg mL⁻¹. For six replicate analyses, the average recoveries of TC and MC from porcine serum sample fortified at the level of 2.5 μg mL⁻¹ were 96.1% with 1.3% RSD and 101% with 0.54% RSD; at level of 0.5 μg mL⁻¹ the average recoveries were 88% with 1.6% RSD and 97.8% with 1.4% RSD.     

Determination of fumonisins B1 and B2 in Portuguese maize and maize-based samples by HPLC with fluorescence detection

Fumonisins B₁ (FB₁) and fumonisin B₂ (FB₂) are the main members of a family of mycotoxins produced by Fusarium verticillioides, Fusarium proliferatum, and other fungi species of the section Liseola. The present work shows the results of comparative studies using two different procedures for the analysis of fumonisins in maize and maize-based samples. The studied analytical methods involve extraction with methanol/water, dilution with PBS, and clean-up through immunoaffinity columns. Two reagents (o-phthaldialdehyde and naphthalene-2,3-dicarboxaldehyde) were studied for formation of fluorescent derivatives. The separation and identification were carried out by high-performance liquid chromatography with fluorescence detection. The optimized method for analysis of fumonisins in maize involved extraction with methanol/water (80:20), clean-up with an immunoaffinity column, and derivatization with naphthalene-2,3-dicarboxaldehyde (NDA). The limit of detection was 20 μg kg⁻¹ for FB₁ and 15 μg kg⁻¹ for FB₂. Recoveries of FB₁ and FB₂ ranged from 79% to 99.6% for maize fortified at 150 μg kg⁻¹ and 200 μg kg⁻¹, respectively, with within-day RSDs of 3.0 and 2.7%. The proposed method was applied to 31 samples, and the presence of fumonisins was found in 14 samples at concentrations ranging from 113 to 2,026 μg kg⁻¹. The estimated daily intake of fumonisins was 0.14 μg kg⁻¹ body weight per day.     

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.     

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