Effects of γ-irradiation on caprolactam level from multilayer PA-6 films for food packaging: Development and validation of a gas chromatographic method

A gas chromatographic method to determine caprolactam in multilayer PA-6 films used for meat foodstuffs and cheese was developed and validated. A wide linear range (0.8–400 μg/ml), RSD4.1% and recovery higher than 90.0% were obtained for the chromatographic system, while precision and accuracy of the method showed RSD3.8%, recovery from 95.5–100.0% and LOQ of 32 μg/g. Irradiated (3, 7 and 12 kGy) and non-irradiated commercial films were analyzed. Most of them increased caprolactam levels with the increase of irradiation doses.     

Identification and migration of degradation compounds from irradiation of multilayer polyamide 6 films for meat foodstuffs and cheese

The aim of this work was to identify the degradation compounds produced during irradiation of multilayer polyamide 6 (PA-6) films and to study their migration into water and 95% ethanol food simulant. After irradiation of multilayer PA-6 films at 3, 7 and 12 kGy, degradation compounds were extracted using solid-phase microextraction, for which the time and temperature of extraction and stirring were optimized, and identified by gas chromatography–mass spectrometry. Caprolactam, 2-cyclopentylcyclopentanone and aldehydes, among other compounds, were identified in the headspace of the films. Polydimethylsiloxane was considered the best fiber for extraction. The optimum conditions of time, temperature and stirring to extract the compounds were 20 min, 80 °C and 225 rpm. For validation purposes, the compounds were quantified in water and 95% ethanol and the results showed high sensitivity, good precision and accuracy. Migration of compounds from irradiated and non-irradiated multilayer PA-6 films into water and 95% ethanol food simulants was carried out at 40 °C for 10 days. The method was efficient for the quantification of decaldehyde, 2-cyclopentylcyclopentanone and caprolactam that migrated from multilayer PA-6 films into food simulants.     

Determination of antioxidant migration levels from low-density polyethylene films into food simulants

An analytical method for the determination of specific migration levels of phenolic antioxidants from low-density polyethylene (LDPE) into food simulant has been developed. The screening and response surface experimental designs to optimize the liquid-liquid extraction (LLE) of these antioxidants have been tested and the analyses have been carried out by reversed-phase high-performance liquid chromatography (HPLC) coupled with ultraviolet diode-array detector. The procedure developed has been applied to specific migration tests in different commercial LDPE films. The considered antioxidants have not been found upper the legislation limits although Ethanox 330 and Irgafos 168 have been found at trace level.     

PVC塑料包装中化学物总迁移的研究

食品包装安全是食品安全的一个重要环节.食品容器、包装等接触材料与食品长期接触会发生"迁移",分为总迁移(overall migration)和特定迁移(specific migration)[1].其中,特定迁移是指某一特定物质在食品包装或容器与食品接触过程中发生的迁移;总迁移是从塑料材料或制品样品到试验媒介的组分总体迁移量.就物质而言,有可知物与未知物,就过程而言,有包装向食品的迁移,也有食品向包装的渗透、吸收等.进行总迁移实验有助于更全面了解一种材料与食品接触会发生的总体变化,对特定迁移的研究起有辅助与补充作用.欧盟对于食品模拟物、样品及前处理[2]、迁移测试方法[3]都有相应规定[4],本实验采用整体浸泡法,研究了PVC材料中化学物在不同食品模拟物中的总迁移.1 实验部分1.1 实验试剂和器材     

The validation of a method for determining the migration of trace elements from food packaging materials into food

A new radiotracer method has been developed to measure the migration of trace elements from food contact packaging into four standard food simulants; acetic acid, ethanol, olive oil, deionised water. A sample of material is irradiated in a thermal neutron flux of 10¹⁶n·m^–2·s^–1 to activate the trace elements and produce a range of radionuclides. The sample is then placed in the food simulant and the migration of the radionuclides is monitored by performing -ray spectrometry on a sample of the simulant. Any radionuclides measured must be due entirely to the migration of the elements present in the plastic, since the simulant itself is not radioactive. Preliminary studies have shown that detection limits of around 0.2g·dm^–2 (0.002 mg/kg) can be achieved for antimony in a sample of polyethylene terephthalate. This method can now been extended to measure migration into real foods. This will highlight any differences between the standard simulants currently used and real foods. Since the method only involves irradiation of the packaging material, any food matrix can be studied.     

Repeated migration of additives from a polymeric article in food simulants

The migration of three additives from polypropylene samples into a series of five liquid food simulants was investigated at 60 °C in a repeated migration regime. This regime was simulated by 20 migration periods each of 8 h and using initially additive free food simulants. Between these migration periods the bare samples were stored in an air conditioned room at around 23 °C for 16 h at working days and for 64 h during weekends. An asymptotic decrease of the additive level in the food simulants in the successive migration periods, from a maximum values towards zero, was observed when the additives easily solve in the food simulants. In contrast when the additives solve poorly in the food simulants this additive level decrease is almost linear and shows a slow decrease rate. In the first case the leaching/migration of the additives is controlled mainly by their diffusion in the matrix of the polymer. In the latter case this process is controlled mainly by the partitioning of the additives between the polymer and food simulants. Two approaches were used to model theoretically these results.In the first approach the mass transport equation was solved by using as input parameters overestimated diffusion and partitioning coefficients as estimated for polypropylene homopolymer, the used food simulants and the three additives according to the recommendations of a practical guidance document in support of migration modelling as stipulated in the Regulation (EU) 10/2011. As expected the results of these calculations overestimate the vast majority of the migration levels determined experimentally. However there are also situations in which this approach leads to underestimations of the real migration levels.In the second approach numerical fitting was applied with the same equation and using the diffusion and partition coefficients as adjustable parameters to obtain a best-fit between experimental and calculated results. It was found that the so obtained “realistic” diffusion coefficients are all lower than the overestimated ones mentioned above. Moreover these “realistic” coefficients depend not only on the nature of the additive but also on the nature of the food simulant in contact with the polymer. This suggests that interaction of food simulants with the polypropylene occurs, which changes the properties of the polymer and thus the mobility of the additive molecules in its matrix. For the “realistic” partition coefficients it was found that they all are higher than the conservative ones mentioned above. Using these “realistic” parameters a good fit between calculated and experimental migration results was found.     

Analytical tools for identification of non-intentionally added substances (NIAS) coming from polyurethane adhesives in multilayer packaging materials and their migration into food simulants

Adhesives used in food packaging to glue different materials can provide several substances as potential migrants, and the identification of potential migrants and migration tests are required to assess safety in the use of adhesives. Solid-phase microextraction in headspace mode and gas chromatography coupled to mass spectrometry (HS-SPME-GC-MS) and ChemSpider and SciFinder databases were used as powerful tools to identify the potential migrants in the polyurethane (PU) adhesives and also in the individual plastic films (polyethylene terephthalate, polyamide, polypropylene, polyethylene, and polyethylene/ethyl vinyl alcohol). Migration tests were carried out by using Tenax(?) and isooctane as food simulants, and the migrants were analyzed by gas chromatography coupled to mass spectrometry. More than 63 volatile and semivolatile compounds considered as potential migrants were detected either in the adhesives or in the films. Migration tests showed two non-intentionally added substances (NIAS) coming from PU adhesives that migrated through the laminates into Tenax(?) and into isooctane. Identification of these NIAS was achieved through their mass spectra, and 1,6-dioxacyclododecane-7,12-dione and 1,4,7-trioxacyclotridecane-8,13-dione were confirmed. Caprolactam migrated into isooctane, and its origin was the external plastic film in the multilayer, demonstrating real diffusion through the multilayer structure. Comparison of the migration values between the simulants and conditions will be shown and discussed.     

气相色谱-质谱法测定聚氯乙烯包装材料和食品模拟物中的46种增塑剂

建立了46种增塑剂在聚氯乙烯(PVC)食品包装材料中的含量及其在水、3%乙酸、10%乙醇和橄榄油4种食品模拟物中迁移量的气相色谱-质谱(GC-MS)测定方法。食品包装材料、水质模拟物和橄榄油中增塑剂分别采用溶解-沉淀法、正己烷液-液萃取和凝胶渗透色谱(GPC)法提取。采用GC-MS法,在选择离子监测模式(SIM)下对46种增塑剂进行定性,采用外标法进行定量测定。各种增塑剂在0.1～2.0 mg/L质量浓度范围内呈线性,相关系数为0.9910～0.9999,各组分检出限均在0.005～0.05 mg/kg之间。在2种食品模拟物中,3个浓度添加水平下46种增塑剂的加标回收率在69.51%～107.21%之间,精密度(RSD, n=6)为3.53%～18.95%。该方法可满足PVC食品接触制品及4种不同性质的食品模拟物中多种类增塑剂的快速筛查和准确定性、定量测定要求。     

Extraction and gas chromatographic evaluation of plasticizers content in food packaging films

Cling films are prepared by adding (5-30% w/w) adipates, citrates, and phthalates. The adverse effects on human health of the plasticizers have been demonstrated, and then their content in food contact plastics and possible migration to foodstuffs must be carefully checked. To offer an easier tool to perform these controls, a Soxhlet extraction by ethyl acetate and a multi residue chromatography analysis, with Flame Ionization Detector, have been optimised for the application in evaluating both the real content of plasticizers in films and freezing bags, and their migrated amounts in simulants. The average extraction yield was 95 ± 10%. The chromatographic analysis was able to determine 16 different compounds, clearly separated, taking only 25 min to complete the assay. The detection limits ranged from 0.07 to 0.7% (w/w). The total amount of plasticizers in the packaging products was comprised between 3 and 10% (w/w). Extracted and migrated amounts were compared, and they resulted in good agreement. No migration of Phthalates, whose presence has been demonstrated in some samples, has been observed. It has been also demonstrated that a prolonged contact (till 60 days) did not increase the amount of migrated plasticizers, and then the risks for health.     

Effect of gamma irradiation on physico-mechanical properties of spice packaging films

Physico-mechanical properties of two types of laminated films, commercially used for spice packaging, are investigated after gamma irradiation at 8, 10 and 15 kGy. Data showed that polyethylene terephthalate/polyethylene terephthalate/linear low density polyethylene (PET/PET/LLDPE) was more resistant to radiation compared to biaxially oriented polypropylene/cast polypropylene (BOPP/CPP) and its barrier properties slightly improved up to 15 kGy. Oxygen transmission rate of BOPP/CPP was increased by 25%, and the melting peak temperature was decreased by 3.9% at 15 kGy, which may lead to oxidation of packaged spices and loss of their aroma/flavour, respectively.     

Method development and validation of a high-performance liquid chromatographic method for pyrethrum extract.

A robust analytical methodology is developed for the quantitative determination of all six insecticidal components of pyrethrum extract: jasmolin I, cinerin I, pyrethrin I, jasmolin II, cinerin II, and pyrethrin II. This method, based on the separation technique normal-phase high-performance liquid chromatography, offers selectivity, accuracy, precision, linearity, range, ruggedness, and robustness as well as efficiency and ease.     

Development and validation of a gas chromatographic method for analysis of fosfomycin in chicken muscle samples

Summary A gas chromatographic method for the determination of residues of Fosfomycin in chicken muscle samples has been developed. Muscle samples were homogenised with TRIS buffer, containing phenylphosphonic acid (as internal standard) and Fosfomycin using a tissue homogenizer. Afterwards, the samples were ultrafiltered and the ultrafiltrate was evaporated to dryness. A silylation reagent for derivatization was used in order to reconstitute the residue. The linear concentration range of application was 10–150 μgg⁻¹, with a detection and quantitation limit of 3.11 and 10 μgg⁻¹, respectively. The method was efficient with a mean recovery of 87.83% from spiked muscle. The results obtained show that gas chromatography is a useful method for the determination of Fosfomycin residues in chicken muscle samples.     

Influence of oxygen and long term storage on the profile of volatile compounds released from polymeric multilayer food contact materials sterilized by gamma irradiation

The profile of volatile compounds released from 13 different multilayer polymeric materials for food use, before and after their exposure to gamma radiation, has been assessed by solid-phase microextraction–gas chromatography–mass spectrometry. Thermosealed bags of different materials were filled with either air or nitrogen to evaluate the oxygen influence. One-third of the samples were analyzed without irradiation, whereas the rest were irradiated at 15 and 25 kGy. Half of the samples were processed just after preparation and the other half was stored for 8 months at room temperature prior to analysis. Very significant differences between unirradiated and irradiated bags were found. About 60–80 compounds were released and identified per sample. A huge peak of 1,3-ditertbutylbenzene was present in most of the irradiated samples. An outstanding reproducibility in all the variables evaluated (chromatograms, oxygen percentage, volume of bags) was noticed. Independently of filling gas, the results of unirradiated materials were almost identical. In contrast, the chromatographic profile and the odor of irradiated bags filled with nitrogen were completely different to those filled with air. Principal component analysis was performed and 86.9% of the accumulated variance was explained with the first two components. The migration of compounds from irradiated materials to the vapor phase was much lower than the limits established in the Commission Regulation (EU) No 10/2011.     

Comparison characterization of copper selenide thin layers prepared on polyamide 6 films by sorption-diffusion method

Some earlier synthesized copper selenide (Cu _x Se) layers formed on the surface of polyamide 6 by sorption-diffusion method using potassium selenotrithionate (K₂SeS₂O₆) as precursor of selenium were characterized by the XRD, XPS and SEM methods. According to the results of the SEM studies, the most uniform Cu _x Se layers form at the 2.5 h polyamide seleniumized duration at the temperature of 60°C. The thickness of layers, which dependeds on the duration of seleniumization, changed in the range of 0.8–3.2 µm. The XRD patterns of not previously studied Cu _x Se layers showed their phase composition of six copper selenides: Cu₂Se, two phases of CuSe₂, Cu₃Se₂, berzellianite, Cu_2-x Se, and bellidoite Cu₂Se. Analysis of the XRD and XPS data shows that the macrostructure and composition of the Cu_xSe layers depend on the conditions of formation of these layers.      

Development and validation of a stability-indicating gas chromatographic method for quality control of residual solvents in blonanserin: a novel atypical antipsychotic agent

Blonanserin is a novel atypical antipsychotic agent for the treatment of schizophrenia. Ethyl alcohol, isopropyl alcohol and toluene are utilized in the synthesis route of this bulk drug. A new validated gas chromatographic (GC) method for the simultaneous determination of residual solvents in blonanserin is described in this paper. Blonanserin was dissolved in N, N-dimethylformamide to make a sample solution that was directly injected into a DB-624 column. A postrun oven temperature at 240°C for approximately 2 h after the analysis cycle was performed to wash out blonanserin residue in the GC column. Quantitation was performed by external standard analyses and the validation was carried out according to International Conference on Harmonization validation guidelines Q2A and Q2B. The method was shown to be specific (no interference in the blank solution), linear (correlation coefficients ≥0.99998, n = 10), accurate (average recoveries between 94.1 and 101.7%), precise (intra-day and inter-day precision ≤2.6%), sensitive (limit of detection ≤0.2 ng, and limit of quantitation ≤0.7 ng), robust (small variations of carrier gas flow, initial oven temperature, temperature ramping rate, injector and detector temperatures did not significantly affect the system suitability test parameters and peak areas) and stable (reference standard and sample solutions were stable over 48 h). This extensively validated method is ready to be used for the quality control of blonanserin.     

Liquid chromatographic method to determine narasin in feedingstuffs and premixtures: development, validation, and interlaboratory study

A reversed-phase liquid chromatography (LC) method for narasin in feedingstuffs and premixtures was developed, validated, and interlaboratory studied. The extraction solvent was methanol-K2HPO4 solution (9 + 1, v/v). Narasin was detected at 600 nm after post-column derivatization with dimethylamino-benzaldehyde. Recovery was >90%. The repeatability (RSDr) in feed (20-140 mg/kg) ranged between 1.2 and 10.5%; the within-laboratory reproducibility (RSD(R)) ranged between 2.2 and 4.9%. The limit of determination was <20 mg/kg. Other feed additives did not interfere in the assay. The method showed ruggedness against changes in the composition of extraction solvent, eluent, and conditions for post-column reactions. In an interlaboratory study, 5 broiler feeds (4 positive, 1 blank) and 1 premixture were analyzed by 13 laboratories. The RSDr of the feedingstuffs (20-120 mg/kg) varied between 2.17 and 7.57%. The HORRAT ranged between 0.77 and 0.88, with recoveries between 82 and 104%. One laboratory detected small signals in the blank sample, calculated as 0.6 and 2.8 mg/kg. For the premixture, acceptable results for reproducibility could only be obtained after modification of the method: the RSDr was 4.42% and the HORRAT was 1.56 (12 laboratories).     

Liquid chromatographic method for nicarbazin in broiler feeds and premixtures: development, validation, and interlaboratory study

A reversed-phase liquid chromatography method for nicarbazin in broiler feeds and premixtures was developed, validated, and interlaboratory studied. The extraction solvent was an acetonitrile-methanol (1 + 1) mixture. For feedingstuffs, water was also added. The 4,4'-dinitrocarbanilide moiety of nicarbazin was detected at a wavelength of 350 nm. Recovery was > or =87%. At 20 mg/kg, the repeatability was 0.7% and the within-laboratory reproducibility was 2.7%. The limit of determination was <20 mg/kg. Other feed additives did not interfere in the assay that proved to be applicable to broiler feeds from different European Union countries. In an interlaboratory study, 4 positive broiler feeds, 1 blank pig feed, and 1 broiler premixture were analyzed by 19 laboratories using the method developed in this study. The relative standard deviation for repeatability (RSDr) of the feedingstuffs (20-240 mg/kg) varied between 2.6 and 10.2%. The HORRAT ranged between 0.70 and 1.22. Recoveries were 91-108%. Three laboratories detected small signals in the blind blank samples, ranging from 0.4 to 2 mg/kg. For the premixture, acceptable results for reproducibility could only be obtained after the sample weight and volume of extraction had been doubled. To avoid excessive dilution of the extracts, the range of the calibration curve had also been doubled. With this modified method, the RSDr was 5.7% and the HORRAT was 1.95 (10 laboratories).     

Measurement of carbonaceous aerosols: validation and comparison of a solvent extraction-gas chromatographic method and a thermal optical transmittance method

A solvent extraction-gas chromatographic method was developed for the measurement of four classes of solvent-extractable organic compounds (SEOC), viz., aliphatic hydrocarbons, polynuclear aromatic hydrocarbons, fatty acids and alkanols, in ambient carbonaceous aerosols. The selectivity and recovery of the method using different solvents commonly used in the analysis of SEOC was evaluated. The composition of SEOC in aerosol and urban dust samples was found to vary with the choice of solvent. Such variation was not observed in filters spiked with standards of SEOC. The developed method was validated by the analysis of reference urban dust SRM 1649a from the National Institute of Standards and Technology. The concentrations of selected polynuclear aromatic hydrocarbons in the reference dust were found to fall within the certified and reference concentrations. The thermal characteristics of aerosol samples collected in an urban area of Hong Kong and the four classes of identified SEOC were also studied using a thermal optical transmittance (TOT) method as specified in NIOSH Method 5040. Correlations were made to compare the method-dependent SEOC content obtained by the solvent extraction method and the results for total carbon, organic carbon and elemental carbon obtained by the TOT method.     

Residue analysis of triazine herbicides in soil: Comparison of a capillary gas chromatographic and a high-performance liquid chromatographic method

Summary Two methods for the determination of triazines in soil were developed and compared. After extraction of the residues with methanol and clean-up by gel permeation chromatography, the samples evaporated were analysed for triazines by splitless capillary gas-chromatography with NP-detector (GC-NPD) and microbore high performance liquid chromatography with UV detector (HPLC-UV) at 222 nm. Both methods gave similar results. The microbore HPLC method was suitable for the analysis of a number of triazines at 10 ppb whereas capillary GC method was used for the analysis of triazines at 5 ppb. Satisfactory average recoveries for the two methods were obtained at 80 ppb and 20 ppb, respectively.

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Rückstandsanalytik von Triazin-Herbiciden im Boden: Vergleich zwischen einer capillar-gas-chromatographischen und einer hochleistungs-flüssig-chromatographischen Methode

Zusammenfassung Zwei Methoden zur Bestimmung von Triazinen im Boden wurden entwickelt und miteinander verglichen. Nach der Extraktion der Rückstände mit Methanol und clean-up durch Gelpermeations-Chromatographie wurden die Proben eingeengt und auf Triazin-Rückstände hin untersucht. Zur Detektion wurden die splitlose Capillar-Gas-Chromatographie mit NP-Detektor (GC-NPD) und die Microbore-Hochdruckflüssig-Chromatographie mit UV-Detektor (HPLC-UV) bei 222 nm verwendet. Beide Methoden ergaben vergleichbare Ergebnisse bei einem Minimum an Zeit- und Materialaufwand und der Möglichkeit der Automatisation der Rückstandsanalytik. Die Microbore-HPLC-Methode erreichte nach einfachem GPC clean-up eine Nachweisgrenze von 10 ppb im Vergleich zu 5 ppb bei der Capillar-GC-Methode. Zufriedenstellende Wiederfindungsraten wurden für beide Methoden bei 80 ppb und 20 ppb ermittelt.

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On leave from: Institute of Hydrobiology, Academia Sinica, Wuhan, P. R. China