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

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

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.      

Validation of a new planar chromatographic method for quantification of the heterocyclic aromatic amines most frequently found in meat

A new HPTLC method, in which all the HPTLC steps are performed automatically, has been established for quantification of the five most frequently found heterocyclic aromatic amines (HAA: PhIP, MeIQx, 4,8-DiMeIQx, norharmane, and harmane). The method was used for trace analysis (low μg kg⁻¹ range) of HAA in meat samples and found to be a cost-effective alternative to HPLC, because it enables simultaneous chromatography of up to 20 samples within 30 min. After preconditioning of the HPTLC silica gel layer with ammonia vapour the plate was developed with methanol–chloroform, 1:9 (v/v). At least 4ó separations were obtained and selectivity for the meat matrix was achieved. In repeatability tests relative standard deviations (RSD, n = 14, peak height) were less than or equal to ±3.3%. In tests of intermediate precision (mean value for 14 tracks on six different plates on six different days) RSDs were better than ±2% (peak height). Measurement of the reproducibility of migration distances on six different plates resulted in RSDs less than or equal to ±1.3%. Limits of detection and quantification (S/N 3 and 10, respectively) for the five HAA ranged between 0.4 and 5 ng per band and between 0.8 and 14 ng per band, respectively. With paraffin–n-hexane, 3:7 (v/v), as fluorescence enhancer more sensitive determinations (up to 8.5-fold greater signal intensities) were achieved for PhIP, norharmane, and harmane. In the working range (1:10) polynomial regressions for PhIP, MeIQx, and 4,8-DiMeIQx and linear regressions for norharmane and harmane resulted in RSDs between ±1.9 and 3.6%. To confirm the absence of potentially coeluting minor HAA, rarely formed in meat, mass spectra were occasionally recorded by online ESI–MS. Robustness tests showed that preconditioning with ammonia was essential for successful separation and that relative humidity had only a minor effect on the chromatography. Analysis of HAA in a meat sample by HPTLC/UV-FLD and confirmation of MelQx by MS     

Fast quantitation of 5-hydroxymethylfurfural in honey using planar chromatography

An approach for rapid quantitation of 5-hydroxymethylfurfural (HMF) in honey using planar chromatography is suggested for the first time. In high-performance thin-layer chromatography (HPTLC) the migration time is approximately 5 min. Detection is performed by absorbance measurement at 290 nm. Polynomial calibration in the matrix over a range of 1:80 showed correlation coefficients, r, of ≥ 0.9997 for peak areas and ≥ 0.9996 for peak heights. Repeatability in the matrix confirmed the suitability of HPTLC–UV for quantitation of HMF in honey. The relative standard deviation (RSD, %, n = 6) of HMF at 10 ng/band was 2.9% (peak height) and 5.2% (peak area); it was 0.6% and 1.0%, respectively, at 100 ng/band. Other possible detection modes, for example fluorescence measurement after post-chromatographic derivatization and mass spectrometric detection, were also evaluated and can coupling can be used as an additional tool when it is necessary to confirm the results of prior quantitation by HPTLC–UV. The confirmation is provided by monitoring the HMF sodium adduct [M + Na]⁺ at m/z 149 followed by quantitation in TIC or SIM mode. Detection limits for HPTLC–UV, HPTLC–MS (TIC), and HPTLC–MS (SIM) were 0.8 ng/band, 4 ng/band, and 0.9 ng/band, respectively. If 12 μL honey solution was applied to an HPTLC plate, the respective detection limits for HMF in honey corresponded to 0.6 mg kg⁻¹. Thus, the developed method was highly suitable for quantitation of HMF in honey at the strictest regulated level of 15 mg kg⁻¹. Comparison of HPTLC–UV detection with HPTLC–MS showed findings were comparable, with a mean deviation of 5.1 mg kg⁻¹ for quantitation in SIM mode and 6.1 mg kg⁻¹ for quantitation in TIC mode. The mean deviation of the HPTLC method compared with the HPLC method was 0.9 mg kg^-1 HMF in honey. Re-evaluation of the same HPTLC plate after one month showed a deviation of 0.5 mg kg⁻¹ HMF in honey. It was demonstrated that the proposed HPTLC method is an effective method for HMF quantitation in honey.      

Determination of tetracycline residues in soil by pressurized liquid extraction and liquid chromatography tandem mass spectrometry

An optimized extraction and cleanup method for the analysis of chlortetracycline (CTC), doxycycline (DC), oxytetracycline (OTC) and tetracycline (TC) in soil is presented. Soil extraction in a pressurized liquid extraction system, followed by extract clean up using solid-phase extraction (SPE) and tetracycline determination by liquid chromatography tandem mass spectrometry (LC-MS/MS) provided appropriate efficiency and reproducibility. Different dispersing agents and solvents for soil extraction and several SPE cartridges for cleanup were compared. The best extraction results were obtained using ethylenediamine tetraacetic acid-treated sand as dispersing agent, and water at 70 °C. The most effective cleanup was obtained using Strata-X^TM sorbent in combination with a strong anion exchange cartridge. Recoveries ranged from 71% to 96% and precision, as indicated by the relative standard deviations, was within the range of 8–15%. The limits of quantification (LOQs) by using LC-MS/MS, based on signal-to-noise ratio (S/N) of 10, ranged from 1 μg kg⁻¹ for TC to 5 μg kg⁻¹ for CTC. These results pointed out that this technique is appropriate to determine tetracyclines in soils. Analysis of 100 samples taken in the Valencian Community revealed that, in soil, up to 5 μg kg⁻¹ CTC, 15 μg kg⁻¹ OTC, 18 μg kg⁻¹ TC, and 12 μg kg⁻¹ DC could be detected. Detection of the analytes in several samples, which typify great part of the Spanish agricultural soils, should be outlined as most important result of this study. Electronic supplementary material  The online version of this article (doi: ) contains supplementary material, which is available to authorized users.     

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.      

UPLC-MS/MS determination of doxazosine in human plasma

A sensitive, selective and rapid method for the analysis of doxazosine (DOX) in human plasma based on ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) is described. DOX and tamsulosin, used as an internal standard (IS), were extracted by liquid-liquid extraction, and the chromatography was performed on a C18 UPLC column packed with 1.7 μm particles. The total run time was 2 min. Detection was achieved by the multiple reaction monitoring of the following transitions: m/z 452→344 and m/z 409→228 for DOX and IS, respectively. Transitions of m/z 452→247 and m/z 409→271 were also collected for confirmation purposes. The calibration curve based on peak area ratio was linear up to at least 100 ng ml⁻¹, with a detection limit of 0.02 ng ml⁻¹ (a signal-to-noise ratio of 3). The method showed satisfactory reproducibility, and the short-term stability of the analyte was assessed. The method was successfully applied to the analysis of DOX in human plasma.     

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     

Enzyme-linked immunosorbent assay and colloidal gold immunoassay for sulphamethazine residues in edible animal foods: investigation of the effects of the analytical conditions and the sample matrix on assay performance

To determine sulphamethazine (SMZ) residues in edible animal foods (pig muscle, chicken muscle, egg, fish, milk and liver), a competitive direct enzyme-linked immunosorbent assay (ELISA) and a colloidal gold immunoassay were established. The limits of detection of the ELISA and the colloidal gold immunoassay were 0.02 and 0.5 μg kg⁻¹, respectively. The specificity of the ELISA developed to the SMZ was high according to the results of cross-reactivity testing with 14 kinds of sulphonamides. To obtain a more sensitive immunoassay, buffer solution (30 mmol L⁻¹ phosphate-buffered saline with 0.05% Tween 20, pH 8.5) was optimized through the whole test procedure. A simple and efficient extraction method for the rapid detection of SMZ residues in foods was developed, with recoveries between 74 and 117.5%. Matrix effects can be avoided by 1:10 dilution of pig muscle, chicken muscle, egg, fish, milk and liver with optimal buffer. The detection limit of SMZ was 5 μg kg⁻¹ in liver and 2 μg kg⁻¹ in the other five samples. For the validation of the ELISA tests, sample extracts were analysed by ELISA and high-performance liquid chromatography. The results obtained by these two methods showed a good correlation (r ²) which was greater than 0.9. The colloidal gold immunoassay presented in this assay was successfully applied to determine SMZ in pig muscle, milk and fish below or equal to the maximum residue level (20 μg kg⁻¹).     

Determination of norfloxacin in human urine by capillary electrophoresis with electrochemiluminescence detection

A fast and sensitive approach that can be used to detect norfloxacin in human urine using capillary electrophoresis with end-column electrochemiluminescence (ECL) detection of is described. The separation column was a 75-μm i.d. capillary. The running buffer was 15 mmol L⁻¹ sodium phosphate (pH 8.2). The solution in the detection cell was 50 mmol L⁻¹ sodium phosphate (pH 8.0) and 5 mmol L⁻¹ The ECL intensity varied linearly with norfloxacin concentration from 0.05 to 10 μmol L⁻¹. The detection limit (S/N=3) was 0.0048 μmol L⁻¹, and the relative standard deviations of the ECL intensity and the migration time for eleven consecutive injections of 1.0 μmol L⁻¹ norfloxacin (n=11) were 2.6% and 0.8%, respectively. The method was successfully applied to the determination of norfloxacin spiked in human urine without sample pretreatment. The recoveries were 92.7–97.9%.      

Determination of 2-isopropyl thioxanthone and 2-ethylhexyl-4-dimethylaminobenzoate in milk: comparison of gas and liquid chromatography with mass spectrometry

Liquid chromatography–tandem mass spectrometry (LC-MS/MS) and gas chromatography–mass spectrometry (GC-MS) have been compared for the analysis of 2-isopropyl thioxanthone (ITX) and 2-ethylhexyl-4-dimethylaminobenzoate (EHDAB). Pressurized liquid extraction (PLE) was applied for the extraction of ITX and EHDAB from milk and milk-based beverages. Samples were homogenized with sea sand and anhydrous sodium sulfate, and were extracted with ethyl acetate at 100 °C and 10.3 × 10⁶ Pa in one cycle of 10 min at 90% flush. Both, GC-MS and LC-MS/MS were suitable to determine these photoinitiators in the PLE extracts, providing appropriate identification and quantification. The recoveries obtained ranged from 70 to 99% for ITX and from 70 to 95% for EHDAB. These recoveries were equal as those obtained by a conventional liquid–liquid partitioning with acetonitrile and tert-butyl methyl ether–hexane. The quantification limits using GC-MS, based on a signal-to-noise ratio of 10, were 0.5 μg/L for ITX and 1 μg/L for EHDAB. The repeatability of the method, as indicated by the relative standard deviations, was within the range 0.9–16.1%. The same parameters calculated using LC-MS/MS result in quantification limits of 0.1 μg/L for ITX and 0.02 μg/L for EHDAB and repeatability within the range 5.2–19.4%. These results pointed out that both techniques are appropriate to determine these compounds in food samples. The method was applied to milk and milk-based beverages from different supermarkets. The ITX and EHDAB contents ranged from 2.5 to 325 μg/L and from 8 to 126 μg/L, respectively. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

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.     

Application of inductively coupled plasma–mass spectrometry (ICP–MS) and quality assurance to study the incorporation of strontium into bone,bone marrow,and teeth of dogs after one month of treatment with strontium malonate

The strontium content of serum, bone, marrow, and teeth was determined by inductively-coupled plasma mass spectrometry (ICP–MS). Significant correlations were obtained after the data were subjected to quality assurance (QA) performed according to validated procedures. After four weeks of treatment with strontium malonate, strontium levels increased from 76 ± 9 μg g⁻¹ in placebo-treated dogs to levels of 7.2 ± 1.7 mg g⁻¹, 9.5 ± 2.7 mg g⁻¹, and 9.8 ± 2.7 mg g⁻¹ in groups treated with 300, 1000, and 3000 mg kg⁻¹ day⁻¹, respectively. Strontium induced a highly significant increase in the bone formation marker, bone-specific alkaline phosphatase (BSAP), and an excellent correlation was found with the bone-strontium content. In females, the placebo-treated group showed a decrease in BSAP of 53%, whereas the three strontium malonate-treated groups showed an increase of 60, 276, and 278% for the groups treated with 300, 1000, and 3000 mg kg⁻¹ day⁻¹, respectively. For males the corresponding values were −44%, +142%, +194%, and +247% increases in BSAP in the placebo, 300, 1000, and 3000 mg kg⁻¹ day⁻¹ groups respectively.     

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.     

A microfluidic system for evaluation of antioxidant capacity based on a peroxyoxalate chemiluminescence assay

A microfluidic system incorporating chemiluminescence detection is reported as a new tool for measuring antioxidant capacity. The detection is based on a peroxyoxalate chemiluminescence (PO-CL) assay with 9,10-bis-(phenylethynyl)anthracene (BPEA) as the fluorescent probe and hydrogen peroxide as the oxidant. Antioxidant plugs injected into the hydrogen peroxide stream result in inhibition of the CL emission which can be quantified and correlated with antioxidant capacity. The PO-CL assay is performed in 800-μm-wide and 800-μm-deep microchannels on a poly(dimethylsiloxane) (PDMS) microchip. Controlled injection of the antioxidant plugs is performed through an injection valve. Of the plant-food based antioxidants tested, β-carotene was found to be the most efficient hydrogen peroxide scavenger (SA _HP of 3.27 × 10⁻³ μmol⁻¹ L), followed by α-tocopherol (SA _HP of 2.36 × 10⁻³ μmol⁻¹ L) and quercetin (SA _HP of 0.31 × 10⁻³ μmol⁻¹ L). Although the method is inherently simple and rapid, excellent analytical performance is afforded in terms of sensitivity, dynamic range, and precision, with RSD values typically below 1.5%. We expect our microfluidic devices to be used for in-the-field antioxidant capacity screening of plant-sourced food and pharmaceutical supplements. Figure Assembled PDMS microchip sandwiched between two glass plates with the top plate containing capillary reservoirs     

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.     

An HPTLC method for the quantitative determination of zearalenone in maize

Summary The high performance liquid chromatographic method adopted by the AOAC [1] for the quantitative analysis of zearalenone has been modified for application to maize, with quantification by high performance thin layer chromatography (HPTLC). The method has been validated by spiking uncontaminated extracts of maize with zearalenone over the range 10 to 320 μg kg⁻¹. A linear relationship was found between 10 and 80 μg kg⁻¹, but at higher levels, the observed values were below the fitted line.     

Certified reference material for quantification of polycyclic aromatic hydrocarbons in sediment from the National Metrology Institute of Japan

The National Metrology Institute of Japan has issued a certified reference material (CRM) of freshwater lake sediment for polycyclic aromatic hydrocarbon (PAHs) analyses. The certification used three extraction techniques: pressurized liquid extraction (PLE) with toluene, PLE with dichloromethane/ethyl acetate (1:1 by volume), and alkaline extraction (1 M KOH in methanol) in combination with microwave-assisted extraction. Both gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/dopant-assisted atmospheric pressure photoionization/MS (LC/DA-APPI/MS) analyses were used. Certified values are provided for 18 PAHs at 1–25 μg kg⁻¹ except for perylene (2.08 × 10³ μg kg⁻¹), and information values are provided for two. Since the values of PAHs in the CRM are much lower than those in other CRMs and are comparable to those found at sites with little human influence, the CRM is suitable for PAH monitoring in sediment and soil samples.     

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.     

Investigating the post-chemiluminescence behavior of phenothiazine medications in the luminol–potassium ferricyanide system: molecular imprinting–post-chemiluminescence method for the determination of chlorpromazine hydrochloride

A new post-chemiluminescence (PCL) phenomenon was observed when phenothiazine medications were injected into the reaction mixture after the chemiluminescence (CL) reaction of luminol and potassium ferricyanide had finished. A possible reaction mechanism was proposed based on studies of the kinetic characteristics of the CL, CL spectra, fluorescence spectra, and on other experiments. The feasibility of determining various phenothiazine medications by utilizing these PCL reactions was examined. A molecular imprinting–post-chemiluminescence (MI-PCL) method was established for the determination of chlorpromazine hydrochloride using a chlorpromazine hydrochloride-imprinted polymer (MIP) as the recognition material. The method displayed high selectivity and high sensitivity. The linear range of the method was 1.0×10⁻⁸∼1.0×10⁻⁶, with a linear correlation coefficient of 0.9985. The detection limit was 3×10⁻⁹ g/ml chlorpromazine hydrochloride, and the relative standard deviation for a 1.0×10⁻⁷ g/ml chlorpromazine hydrochloride solution was 4.0% (n=11). The method has been applied to the determination of chlorpromazine hydrochloride in urine and animal drinking water with satisfactory results.