Evaluation of results of an interlaboratory comparison test on determination of acrylamide in crispbread samples

The European Commission's Directorate General Joint Research Centre has organized several proficiency tests on the determination of acrylamide (AA) in food. This paper presents the results and outcome of a proficiency test that focused on the determination of AA in crispbread samples. One of the goals was the identification of the influence of different parameters such as analyte extraction or instrument calibration on the analytical results. A set of samples, containing 3 different crispbread samples as well as extracts of one crispbread sample and AA standard solutions, was shipped to each participant. A total of 42 European laboratories reported analytical results that were evaluated by applying internationally accepted protocols and procedures. The study found that, for each sample, the results of 4-8 laboratories were outside the range formed by the target value plus or minus the 2-fold of the target standard deviation; thus, they did not perform satisfactorily. In transferring this knowledge to the data of monitoring databases of AA in food, care must be taken that data are quality controlled, as it is likely that some of them may be biased.     

Evaluation of the results from an inter-laboratory comparison study of the determination of acrylamide in crispbread and butter cookies

Analytical methods currently employed for determination of acrylamide (AA) in two carbohydrate-rich food samples, crispbread and butter cookies, obtained commercially, and native and spiked bread extract samples have been evaluated in a collaborative study. The objective of the study was to obtain information about the performance of the participating laboratories when analysing samples with an AA content close to the limit of quantification (LOQ) and at a higher AA level, and to investigate the influence of sample-preparation procedures on the results of the analysis. For this purpose an aqueous native extract of white bread crumb, a fortified extract, and AA standard solutions, the analyte content of which were not disclosed to the participants, were included in the study. A total of 62 laboratories, applying seven different measurement techniques and a broad spectrum of analyte extraction and sample-preparation procedures reported their analytical results. Because the measurement data were not normally distributed, they were evaluated by application of robust statistics. The relative performance of the laboratories was highlighted by calculation of z-scores. For the crispbread sample, especially, a large percentage of the calculated z-scores were outside the satisfactory range. From their distribution it became obvious that one of the analytical techniques might be biased, if not applied correctly. Consequently, the impact of the applied methods was examined in more detail. Information about the analytical technique, extraction solvent, quantity weighed, calibration method, clean-up, and the experience of the participating laboratories were extracted from the analytical protocols and transcribed into a data matrix which was evaluated by multifactor analysis of variance. The applied measurement technique seems to have a statistically significant influence on the analytical results.     

Evaluation of the long-term performance of water-analyzing laboratories

After 7 years of successful operation, the database of the proficiency testing (PT) scheme for water analysis organized by the Institute for Agrobiotechnology (IFA), Tulln contains nearly 4,000 data sets from over 300 interlaboratory comparison samples. About 70 analytical parameters (major ions, metals, trace ions, herbicides, volatile halogenated hydrocarbons, organochlorine pesticides and polycyclic aromatic hydrocarbons) were covered by the PT scheme. The data were evaluated using robust statistics in order to determine a set of coefficients of variation (CV) for each analytical parameter. Concentration and time dependence of the CV were checked. The CV were combined to obtain standard deviations for proficiency assessment (Z-score criteria). Furthermore, a viewer program was designed to facilitate monitoring of the analytical performance of participating laboratories.     

固相萃取-超高效液相色谱法测定卷烟主流烟气中丙烯酰胺

建立了一种固相萃取-超高效液相色谱法(SPE-UPLC)快速检测主流烟气中丙烯酰胺的方法。使用剑桥滤片和吸收瓶捕集主流烟气后,蒸馏水做萃取溶剂,采用C18固相萃取小柱对样品液进行纯化,用UPLC检测,外标法定量。UPLC方法采用ACQUITY UPLCTMBEH C181.7μm 2.1×50 mm色谱柱,柱温30℃,流动相为V(乙腈)∶V(水)=6∶94,流速为0.15 mL/min,紫外检测器(TUV)检测波长为202 nm,分析时间为6 min。烤烟型香烟主流烟气中丙烯酰胺的含量为4.75μg/cig。方法的线性范围为0.1~10 mg/mL,线性相关系数为0.9999;平均回收率为98.7%;检出限为10 ng/mL(S/N=3);相对标准偏差为2.3%。该方法适合主流烟气中丙烯酰胺的快速检测。     

高效液相色谱法测定方便面中丙烯酰胺

建立了一种检测方便面中丙烯酰胺的液相色谱方法。萃取剂选择1g/L的蚁酸溶液,将萃取液以12000r/min,2℃离心18min,上清液再以14500r/min,0℃离心18min,可分离基质中淀粉、蛋白质、脂肪等干扰物;方法采用ZORBAX SB-C18(250mm×4.6mm,5μm)色谱柱,流动相为A(乙腈∶水=1∶24(V/V))和B(乙腈),流速0.5mL/min,在丙烯酰胺的最大吸收197nm处检测,提高了方法的检出限及回收率。该方法有良好的线性关系(r=1.00000),检出限为48.0μg/kg。回收率94.4%～109.8%,相对标准偏差为4.9%～5.6%。     

The effects of quality-management systems on external quality-assessment performance in Finnish clinical chemistry laboratories

The effects of the implementation of quality-management systems and technological changes on the performance of 23 Finnish clinical chemistry laboratories were studied in external quality-assessment (EQA) schemes organized by Labquality Ltd., Finland, during 1993 to 1999. The investigated serum analytes were sodium, calcium, glucose, cholesterol, and alanine aminotransferase. According to the results, the improvements in analytical quality due to the quality programs were rather small. The effects to the proportions of satisfactory results in terms of precision and deviation from the target value were 5–15% (95% confidence intervals for the proportions ±1–5%). At the same time the laboratories were implementing quality-management systems new technology and characteristics of quality-control materials affected the EQA performance. Both improvements and deteriorations in analytical quality due to these factors were identified. The effects and their total outcomes differed substantially between the five analytes.     

Analysis of acrylamide in coffee and dietary exposure to acrylamide from coffee

An analytical method for analysing acrylamide in coffee was validated. The analysis of prepared coffee includes a comprehensive clean-up using multimode solid-phase extraction (SPE) by automatic SPE equipment and detection by liquid chromatography tandem mass spectrometry using electrospray in the positive mode. The recoveries of acrylamide in ready-to-drink coffee spiked with 5 and 10 μg l⁻¹ were 96±14% and 100±8%, respectively. Within laboratory reproducibility for the same spiking levels were 14% and 9%, respectively. Coffee samples (n = 25) prepared twice by coffee machines and twice by a French Press Cafetière coffee maker contained 8±3 μg l⁻¹ and 9±3 μg l⁻¹ acrylamide. Five ready-to-drink instant coffee prepared twice contained 8±2 μg l⁻¹. Hence, the results do not show significant differences in the acrylamide contents in ready-to-drink coffee prepared by coffee machine, French Press or from instant coffee. Medium roasted coffee contained more acrylamide (10 μg l⁻¹) than dark roasted coffee (5 μg l⁻¹). Males aged 35–45 years, drinking on average 1.1 l coffee per day are exposed to the highest doses of acrylamide from coffee. The dietary intake of acrylamide from coffee comprises, on an average, 10 μg day⁻¹ for males and 9 μg day⁻¹ for females aged 35–45 years. Probabilistic modelling of the exposure of Danish consumers (all adults) to acrylamide from coffee shows a mean exposure of 6.5 μg day⁻¹ and a 95 percentile of 18 μg day⁻¹.     

固相萃取-超高效液相色谱法测定烟用水基胶中丙烯酰胺

建立了采用固相萃取-超高液相色谱/紫外检测测定烟用水基胶中丙烯酰胺的分析方法。样品经超纯水进行超声提取,固相萃取柱进行富集净化后,经HSS T3色谱柱分离,以甲醇和水为流动相等度洗脱,紫外检测,外标法定量。结果显示,丙烯酰胺在浓度0.01~20.0μg·mL-1范围内有良好的线性关系,相关系数为0.9999。丙烯酰胺三个不同浓度的加标回收率为91.7%~105.1%;相对标准偏差为1.3%~4.7%(n=6);检出限为3.5μg·L-1。该方法分析时间短、结果准确可靠,满足烟用水基胶中丙烯酰胺的测定。     

超高效液相色谱-大气压化学电离-串联质谱法测定烘焙咖啡中丙烯酰胺

建立了烘焙咖啡中丙烯酰胺的超高效液相色谱-大气压化学电离-串联质谱（UHPLC-APCI-MS/MS）分析方法。样品经甲醇提取，HLB固相萃取（SPE）小柱净化，Brownlee validated AQ C18色谱柱分离，采用大气压化学电离（APCI）源，正离子扫描和多反应监测（MRM）模式对丙烯酰胺进行检测，内标法定量。结果表明，丙烯酰胺在0.5~100.0 μg/L范围内具有良好的线性关系，相关系数（r²）为0.999，方法检出限为5.0 μg/kg，定量限为10.0 μg/kg。在100.0、200.0和1000.0 μg/kg添加水平下，丙烯酰胺的回收率为94.6%~115.0%，相对标准偏差（RSD）值为2.8%~3.6%（n=6）。本方法采用APCI源作为离子化方式，能有效地减少咖啡基质对丙烯酰胺的基质干扰，前处理简单，灵敏度高，适用于咖啡中丙烯酰胺的日常检测。     

Thermal behavior and fire performance of nylon-6,6 fabric modified with acrylamide by photografting

Our previous study shows that surface photografting modification with maleic anhydride followed by reacting with triethanolamine can improve the flame retardancy of nylon-6,6 fabric. In this study, acrylamide was used as a grafting monomer to improve the flame retardancy of nylon-6,6 fabric. The effects of monomer concentration and irradiation time on photografting were investigated. The surface structure of the sample was analyzed by attenuated total reflection infrared spectroscopy (ATR-FTIR). Flame retardancy was characterized by limiting oxygen index test (LOI), the vertical burning test and cone calorimeter. The grafted sample has a higher LOI value than the untreated sample, and has no melting drip during the vertical burning test. The improvement of the flame retardancy and char formation of the nylon-6,6 fabric have also been verified by the thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) analysis.     

Synthesis and flocculation performance of graft and random copolymer microgels of acrylamide and diallyldimethylammonium chloride

Graft (from linear homopolymers) and random (from a linear random copolymer) copolymer microgels of diallyldimethylammonium chloride (DADMAC) and acrylamide were synthesized via a free-radical mechanism using a γ-radiation technique. These copolymer microgels were evaluated as flocculants on a model dilute TiO₂ colloid suspension using a turbidimeter and a disc centrifuge photosedimentometer, and their performances were compared with the linear homopolymers and their blends. It was found that microgels produced after an appropriate irradiation time showed improved flocculation behavior over their nonirradiated linear counterparts. The graft microgels performed better than the corresponding random microgels. For a γ-radiation dosage of 100 krad/h, the graft microgels obtained by irradiating a 30% DADMAC (by weight) homopolymer blend for 3 h showed the maximum reduction in the relative turbidity of the TiO₂ suspension as well as the largest fraction of larger particles flocculated. Received: 18 May 1999 Accepted in revised form: 1 June 1999     

Synthesis, characterization and flocculation performance of zwitterionic copolymer of acrylamide and 4-vinylpyridine propylsulfobetaine

A novel zwitterionic polyacrylamide AMVPPS copolymer containing sulfobetaine groups was synthesized by copolymerizing acrylamide (AM) and 4-vinylpyridine propylsulfobetaine (4-VPPS) in 0.5 mol/L NaCl solution with potassium persulfate (K₂S₂O₈) and sodium bisulfite (NaHSO₃) as initiator. The structure and composition of AMVPPS copolymer were characterized by FT-IR spectroscopy, ¹H NMR and elemental analyses. Thermal stability and solution properties of AMVPPS copolymer were studied by thermogravimetry analysis (TGA) and viscometry. Anti-polyelectrolyte behavior was observed and was found to be enhanced with increasing 4-VPPS content in copolymer. The flocculation performance for 2.5 g/L kaolin suspension and 2.5 g/L hematite suspension was evaluated by transmittance measurement and phase contrast microscopy. The effects of 4-VPPS content in the copolymer, intrinsic viscosity and the added salt on the flocculation performance were investigated. It was found that AMVPPS copolymer was a good flocculant for both anionic kaolin and cationic hematite suspensions and the flocculation performance of copolymer was much better than that of pure polyacrylamide (PAM). A very wide range of the optimum flocculation concentration, named as “flocculation window”, was found for both suspensions. These flocculation characteristics were mainly dependent on the charge neutralization, the intragroup conformation transition from water to NaCl solution and then the interchain bridging of the zwitterionic AMVPPS copolymer.     

The preparation and utilization of performance evaluation soils for evaluating radioassay laboratories engaged in site remediation work

Site remediation projects dealing with uranium, thorium or radium require the services of a radioassay laboratory during the site characterization, remediation and final site survey/verification phases. In the U.S., regulatory agencies and industry guidelines recommend that the remediation contractor conduct an external laboratory QC program to ensure the quality of the analytical results. The commercial availability of certified natural soil matrices is extremely limited not only by nuclide and nuclide concentration but also by soil type. In most cases, the applicability of these materials for an external QC program is questionable since the chemical constituents of the certified soil may not be representative of the remediation soil type. Also, such materials are typically only suitable as single blind performance evaluation (PE) samples. The Yankee Atomic Environmental Laboratory (YAEL) has characterized soil materials from several uranium mining and milling sites for use in two laboratory PE programs. The site specific PE materials were prepared in accordance with their intended use and quality performance requirements. One PE material was dried, pulverized to a particle size of approximately 10 microns and homogeneously blended. The second PE material (total of 1,024 kg) was methodically field blended and aliquoted to produce 1,000 separate homogeneous 1 kg samples. Both PE materials were characterized for radionuclide concentration and heterogeneity or sample distribution. A summary of the characterization studies of the different PE materials as well as the quality performance criteria developed for evaluating the laboratory's performance and the advantages and disadvantages of using each PE material will be discussed and summarized.     

Determination of acrylamide and methacrylamide by normal phase high performance liquid chromatography and UV detection

A method using normal phase high performance liquid chromatography (NP-HPLC) with UV detection was developed for the analysis of acrylamide and methacrylamide. The method relies on the chromatographic separation of these analytes on a polar HPLC column designed for the separation of organic acids. Identification of acrylamide and methacrylamide is approached dually, that is directly in their protonated forms and as their hydrolysis products acrylic and methacrylic acid respectively, for confirmation. Detection and quantification is performed at 200 nm. The method is simple allowing for clear resolution of the target peaks from any interfering substances. Detection limits of 10 microg L(-1) were obtained for both analytes with the inter- and intra-day RSD for standard analysis lying below 1.0%. Use of acetonitrile in the elution solvent lowers detection limits and retention times, without impairing resolution of peaks. The method was applied for the determination of acrylamide and methacrylamide in spiked food samples without native acrylamide yielding recoveries between 95 and 103%. Finally, commercial samples of french and roasted fries, cookies, cocoa and coffee were analyzed to assess applicability of the method towards acrylamide, giving results similar with those reported in the literature.     

Do proficiency tests always verify laboratories’ performance? The case of FAPAS PT 0270

In this paper, the case of FAPAS PT 0270 “Doramectin and Oxfendazole in Sheep Liver” is discussed. During evaluation of the data received from participants (determination of total, oxidised oxfendazole residue and calculation of the sum of oxfendazole and oxfendazole sulfone residues), significant differences were observed between the results obtained by use of two analytical approaches. This phenomenon can be explained by the route of oxfendazole metabolism, which results in the presence of fenbendazole in the sample. This was not predicted by the provider; consequently, not all the necessary tests on the material were conducted. Due to the high uncertainty of the z-scores in this test, the results of the PT cannot be used for purposes of evaluation, and the benefits of participation in PT 0270 are questionable.     

How to interpret information from proficiency test exercises concerning the relative performance of accredited laboratories

If the results from various proficiency tests are used to compare the performance of accredited and non-accredited laboratories, great care must be taken not to come to contradicting conclusions when interpreting them. This paper intends to draw the attention to various aspects that should be taken into account when trying to make conclusions from the relative performance of accredited laboratories in proficiency testing.     

Accreditation of pathology laboratories in Finland

 The Finnish Accreditation Service (FINAS) accredits testing laboratories in all fields including medical laboratories according to European standard EN 45001 and ISO Guide 25. At the beginning of 1998, FINAS published a recommendation on how to apply general standards in histo- and cytopathology. Four pathology laboratories have been accredited to date. FINAS has not included autopsies in these accreditations. The International Academy of Pathology (IAP)-Finnish Division has recognized 21 pathology laboratories according to standards of their own. Although accreditation by FINAS is not connected to the system of the IAP-Finnish Division, the requirements are very similar in both. Less than half of the pathology laboratories in Finland participate in national quality improvement programme or have been accredited by FINAS.     

Spontaneous polymerization of acrylamide in glycerol

The spontaneous polymerization of acrylamide in glycerol in the range of 250–350°C has been first observed and investigated. It has been shown that the polymerization proceeds during dissolution of acrylamide in glycerol and leads to formation of gel globules in which the growth of polymer chains takes place. The reaction occurs without termination of kinetic chains in the living polymerization mode. The effective chain transfer at a low concentration of active centers ensures a high yield of the polymer.