Spectrofluorimetric determination of formaldehyde in maple syrup

A quick and simple method was developed for determination of formaldehyde in maple syrup. In this method, formaldehyde reacts with Fluoral P to form a complex which is chemically extracted by isobutanol and determined by spectrofluorimetry. Performance, as gauged by the limits of detection (0.16 mg/kg) and quantitation (0.21 mg/kg), recovery (>79%), and variability (1.9-16.1%, depending on fortification level and class of syrup) were superior to the current official AOAC standard method.     

Determination of naturally occurring formaldehyde levels in sap and wood tissue of maple trees using gas chromatgraphy/mass spectrometry

The occurrence of formaldehyde in sap and wood tissue of treated and untreated maple sugar trees was investigated using GC/MS. Samples were collected at different periods of the 2009 season and at different locations in Quebec, Canada. The natural concentration of formaldehyde found in untreated samples varied according to periods and locations and ranged from below the LOQ to 1.82 mg/kg for sap samples and from 2.39 to 8.92 mg/kg of fresh tissue for wood samples. Late season samples tended to have higher concentrations of formaldehyde. Samples of sap and wood tissue from tapholes treated with solutions of formaldehyde showed increased concentrations of formaldehyde for many days after treatment and were clearly distinct from untreated samples. These results will be useful to elaborate new inspection procedures for sugarbushes to control the illegal use of formaldehyde.     

Detection of added beet or cane sugar in maple syrup by the site-specific deuterium nuclear magnetic resonance (SNIF-NMR) method: collaborative study

Results of a collaborative study are reported for the detection of added beet or cane sugar in maple syrup by the site-specific natural isotope fractionation-nuclear magnetic resonance (SNIF-NMR) method. The method is based on the fact that the deuterium content at specific positions of the sugar molecules is different in maple syrup from that in beet or cane sugar. The syrup is diluted with pure water and fermented; the alcohol is distilled with a quantitative yield and analyzed with a high-field NMR spectrometer fitted with a deuterium probe and fluorine lock. The proportion of ethanol molecules monodeuterated at the methyl site is recorded. This parameter (D/H)I is decreased when beet sugar is added and increased when cane sugar is added to the maple syrup. The precision of the method for measuring (D/H)I was found to be in good agreement with the values already published for the application of this method to fruit juice concentrates (AOAC Official Method 995.17). An excellent correlation was found between the percentage of added beet sugar and the (D/H)I isotopic ratio measured in this collaborative study. Consequently, all samples in which exogenous sugars were added were found to have a (D/H)I isotopic ratio significantly different from the normal value for an authentic maple syrup. By extension of what is known about plants having the C4 cycle, the method can be applied to corn sweeteners as well as to cane sugar. One limitation of the method is its reduced sensitivity when applied to specific blends of beet and cane sugars or corn sweeteners. In such case, the C13 ratio measurement (see AOAC Official Method 984.23, Corn Syrup and Cane Sugar in Maple Syrup) may be used in conjunction.     

水发食品中甲醛现场测定的样品快速前处理新方法研究

提出了一种用于现场测定水发食品中甲醛含量的样品快速前处理新方法,采用乙酸锌和亚铁氰化钾沉淀样品中的蛋白质和脂肪,在弱酸性介质和沸水浴条件下提取了样品中的甲醛,并与乙酰丙酮立即发生显色反应.研究了不同样品前处理方法对甲醛提取和测定的影响,探讨了水发食品中的甲醛本底值及其是否被人为添加甲醛的判断标准.此方法的特点是样品前处理与显色反应同时进行,在10min内即可完成对水发食品中甲醛含量的定量测定.     

Analysis of Reducing Carbohydrates and Fructosyl Saccharides in Maple Syrup and Maple Sugar by CE

Reducing carbohydrates in maple syrup and maple sugar were separated by capillary electrophoresis using derivatization with 1-phenyl-3-methyl-5-pyrazolone (PMP) and the characteristics of these samples were studied. Reducing carbohydrate standards including nine monosaccharides and five disaccharides as PMP derivatives could be easily resolved by using 200 mM borate buffer (pH 10.5) as a background electrolyte. Glucose was the most abundant reducing sugar in both maple samples, and mannose was abundant relative to the other sugars. The other monosaccharides (xylose, arabinose, ribose, galactose and N-acetylglucosamine) were also detected. When maple syrup and maple sugar were treated with invertase, which removed fructose residues from the reducing ends of fructosyl saccharides, melibiose was detected, suggesting that raffinose exists in both samples. The differences of carbohydrate contents between maple syrup and maple sugar were also discussed.

     

液相色谱/元素分析-同位素比值质谱联用法鉴定蜂蜜掺假

采用液相色谱/元素分析-同位素比值质谱联用法(LC/EA-IRMS)对国内蜂蜜掺假情况进行了研究。基于测定得到的38个纯正蜂蜜样品的碳同位素δ13C值数据,提出了纯正蜂蜜样品的δ13C值要求: 蛋白质和蜂蜜的δ13C差值(Δδ13CP-H)≥~0.95‰,果糖和葡萄糖的δ13C差值(Δδ13CF-G)在~0.64‰至0.53‰范围内,各个组分间的δ13C最大差值(Δδ13Cmax)＜2.09‰。对150个日常检测样品、蜂农和蜂蜜供应商的蜂蜜样品分别采用本文建立的LC/EA-IRMS和国家标准方法(EA-IRMS)进行鉴定,LC/EA-IRMS方法检出58个掺有C3或C4植物糖浆的阳性样品,而EA-IRMS方法仅检出7个掺有C4植物糖浆的阳性样品,可见新方法大大提高了对蜂蜜掺假的鉴别能力。     

Application of Total Reflection X-Ray Fluorescence Spectrometry in the Textile Industry

 In the present study, the determination of arsenic, lead, cadmium, chromium, cobalt, copper, nickel, mercury and zinc in various cloth samples produced in Kayseri-Turkey was performed after extraction with artificial sweat solution and decomposition with nitric acid. TXRF is shown to be suitable for the determination of 7 trace elements, down to the 0.001 (cobalt) to 0.004 (copper) mg/kg level in textile extract except for mercury and cadmium. The extractable part of the toxic metals by artificial sweat solution is relatively low. In a few extracts the concentration values of Pb and Ni have exceeded their critical values of 0.2 mg/kg for lead and 1.0 mg/kg for nickel given by ?ko-Tex and determined for babys cloths. In addition, it was observed that the element pattern of textile samples resembled ‘finger print type’, TXRF-spectra. This technique can also be used for the identification of textile sample in forensic investigation. Received April 16, 2001 Revision October 1, 2001.     

Effects of ammonium chloride and heat treatment on residual formaldehyde contents of melamine-formaldehyde microcapsules

Microencapsulated n-octadecane with melamine–formaldehyde resin (MF) shell was synthesized by in situ polymerization. Ammonium chloride was used to reduce the residual formaldehyde content of microencapsulated phase change materials (microPCMs) caused by the inherent characteristics of MF. Moreover, microPCMs were heat-treated at 160 °C for 30 min. The surface morphology of the microPCMs fabricated at various microencapsulation periods was examined, and the shell thickness was measured. The effects of heat treatment on the surface morphology, residual formaldehyde content, phase change properties, and thermal stability of the microcapsules were systematically investigated. The globular surface of microcapsules fabricated at microencapsulation period of 120 min was smooth and compact with an average diameter about 2.2 μm, and the shell thickness was ranged from 30 to 70 nm. The thermal stability of heat-treated microcapsules enhanced significantly as microencapsulation period increased; in addition, the residual formaldehyde content of microcapsules decreased from 125 ± 1 mg/kg to 19 ± 1 mg/kg.     

Determination of lead, cadmium, zinc, copper, and iron in foods by atomic absorption spectrometry after microwave digestion: NMKL Collaborative Study

A method for determination of lead, cadmium, zinc, copper, and iron by atomic absorption spectrometry (AAS) after microwave digestion was subjected to a collaborative study in which 16 laboratories participated [including users of inductively coupled plasma (ICP) and ICP-mass spectrometry (MS)]. The types of samples included in the study were minced fish, wheat bran, milk powder, bovine and pig liver, mushroom, 2 simulated diets, and bovine muscle; the last 4 were certified reference materials. These were analyzed as single (4 samples), double blind (1 sample), or split level (2 samples) samples. Before the collaborative study, a pretrial was conducted in which 4 ready-made solutions and one fish tissue sample were analyzed for Pb and Cu. The reproducibility relative standard deviation (RSDR) values, for results above the detection limit, ranged from 59% at 0.155 mg/kg to 16% at 1.62 mg/kg for Pb, from 28% at 0.0124 mg/kg to 11% at 0.482 mg/kg for Cd, from 9.3% at 35.3 mg/kg to 1.7% at 147 mg/kg for Zn, from 39% at 0.241 mg/kg to 3.0% at 63.4 mg/kg for Cu, and from 17% at 7.4 mg/kg to 5.9% at 303 mg/kg for Fe. The RSDR values agreed well with the norms described by the International Union of Pure and Applied Chemistry. As a complement to the AAS determinations, a number of laboratories analyzed the samples either by ICP or by ICP-MS. The results of these analyses agreed well with the AAS results. On the basis of the results of the collaborative study, the method was adopted Official First Action by AOAC INTERNATIONAL.     

衍生液提取-高效液相色谱法快速测定香菇中的游离甲醛

以2,4-二硝基苯肼乙腈溶液-pH 5磷酸盐缓冲液(体积比为1:1)为提取溶液,提取香菇中游离的甲醛,采用高效液相色谱法测定。结果表明,乙腈-pH 5磷酸盐缓冲液(体积比为1:1)能够有效地抑制香菇中酶反应释放甲醛,达到提取香菇中游离甲醛的目的。在提取液中加入衍生化试剂2,4-二硝基苯肼,将甲醛的提取和衍生化反应相结合,此衍生液提取方法有效地提高了检测效率。鲜香菇样品中分别添加5.0、10.0、20.0 mg/kg的甲醛,平均回收率分别为89.2%、91.7%和90.4%,相对标准偏差(n=6)＜5.0%。方法的定量限（S/N＞10）为5.0 mg/kg。该方法适用于香菇中游离甲醛的检测,且快速简便、重现性好,是确定香菇中甲醛天然本底值的有效方法。     

紫外可见分光光度法测定壁纸中甲醛的不确定度评定

采用紫外可见分光光度法测定壁纸中甲醛含量,对测定结果的不确定度进行评定。依据GB 18585–2001《室内装饰装修材料壁纸中有害物质限量》标准,对壁纸中甲醛含量的检测过程进行研究,系统地分析了整个检测过程不确定度的来源,包括重复测定、样品溶液的移取、标准工作溶液的配制、标准曲线的拟合和测定仪器等引入的不确定度。结合日常检测数据,首次采用欧洲标准化差值标准偏差的方法,对各不确定度分量进行评定。当壁纸中甲醛含量范围为0.54~28.47 mg/kg时,测定结果在95%置信区间时的相对扩展不确定度为0.035 2(k=2)。不确定度主要来源于样品移取过程中移液枪的使用、样品重复测定和标准曲线的拟合。     

Determination of the 13C/12C ratio of ethanol derived from fruit juices and maple syrup by isotope ratio mass spectrometry: collaborative study

A collaborative study of the carbon-13 isotope ratio mass spectrometry (13C-IRMS) method based on fermentation ethanol for detecting some sugar additions in fruit juices and maple syrup is reported. This method is complementary to the site-specific natural isotope fractionation by nuclear magnetic resonance (SNIF-NMR) method for detecting added beet sugar in the same products (AOAC Official Methods 995.17 and 2000.19), and uses the same initial steps to recover pure ethanol. The fruit juices or maple syrups are completely fermented with yeast, and the alcohol is distilled with a quantitative yield (>96%). The carbon-13 deviation (delta13C) of ethanol is then determined by IRMS. This parameter becomes less negative when exogenous sugar derived from plants exhibiting a C4 metabolism (e.g., corn or cane) is added to a juice obtained from plants exhibiting a C3 metabolism (most common fruits except pineapple) or to maple syrup. Conversely, the delta13C of ethanol becomes more negative when exogenous sugar derived from C3 plants (e.g., beet, wheat, rice) is added to pineapple products. Twelve laboratories analyzed 2 materials (orange juice and pure cane sugar) in blind duplicate and 4 sugar-adulterated materials (orange juice, maple syrup, pineapple juice, and apple juice) as Youden pairs. The precision of that method for measuring delta13C was similar to that of other methods applied to wine ethanol or extracted sugars in juices. The within-laboratory (Sr) values ranged from 0.06 to 0.16%o (r = 0.17 to 0.46 percent per thousand), and the among-laboratories (SR) values ranged from 0.17 to 0.26 percent per thousand (R = 0.49 to 0.73 percent per thousand). The Study Directors recommend that the method be adopted as First Action by AOAC INTERNATIONAL.     

蜂蜜中外源性γ-淀粉酶残留量的测定

采用液相色谱-同位素质谱联用法(LC-IRMS)建立了测定蜂蜜中外源性γ-淀粉酶残留量的方法。先采用凝胶色谱柱对蜂蜜样品进行预分离,将样品中所含的酶与糖分离开。根据γ-淀粉酶可将底物麦芽糖酶解为葡萄糖的原理,在55 ℃、pH 4.5的0.03 mol/L磷酸盐缓冲液中将γ-淀粉酶与麦芽糖反应48 h后,采用LC分离麦芽糖和葡萄糖,以IRMS测定酶解产物葡萄糖的含量来确定γ-淀粉酶的残留量。本方法的线性范围为5～200 U/kg,定量限为5 U/kg,回收率为89.6%～108.2%,相对标准偏差为3.3%～4.9%。采用本方法对市售蜂蜜和大米糖浆共38个样本进行了考察,γ-淀粉酶的检出率为76.3%。为了进一步验证本方法的检测能力,测定了掺入15%(质量分数)大米糖浆的蜂蜜样品,测得γ-淀粉酶的含量为10.2 U/kg。本方法能够有效地从酶学的角度鉴定蜂蜜中是否含有大米糖浆。     

分光光度法快速测定毒鼠强的研究

本文将毒鼠强在酸性条件下分解,分解产生的甲醛用水蒸汽蒸馏使之与干扰物质分离,再根据Hantzsch反应原理,用乙酰丙酮-乙酸铵溶液作显色剂分光光度法测定甲醛,从而间接测定毒鼠强的含量。本法的线性范围为5~40 mg/kg。本法干扰少,操作简便、快速,可用于中毒样品的测定。     

Rapid fluorescence screening assay for tetracyclines in chicken muscle

A simple, rapid fluorescence assay was developed for screening tetracyclines in chicken muscle at the U.S. tolerance level (2 mg/kg). The method requires only a homogenization of the tissue in acetonitrile-ammonium hydroxide, centrifugation, addition of Mg+2, and another centrifugation before fluorescence of the supernatant is measured at 505 nm (excitation at 385 nm). Comparison of the fluorescence of control chicken muscle extracts with extracts from muscle fortified with either 2 mg/kg tetracycline, oxytetracycline, or chlortetracycline showed no overlap. A threshold level set at the average fluorescence for a series of fortified 2 mg/kg samples minus 3sigma minimized false-negative responses to provide a successful screening method. The method was tested with blinded samples as controls or samples fortified with tetracycline, oxytetracycline, or chlortetracycline in order to demonstrate its utility. This approach can provide an alternative to microbial screening assays.     

GC/MS法测定大米中精噁唑禾草灵和氰氟草酯残留量

采用乙腈提取,NH2固相萃取柱净化,GC/MS测定,建立了大米中精噁唑禾草灵和氰氟草酯残留量的测定方法。添加精噁唑禾草灵质量分数为0.02,0.2,0.5mg/kg,平均回收率分别为82.3%,88.8%和90.7%,相对标准偏差分别为6.8%,8.2%和3.7%,检出限为0.02 mg/kg;添加氰氟草酯质量分数为0.02,0.2,0.5mg/kg,平均回收率分别为87.7%,94.2%和92.3%,相对标准偏差分别为8.6%,5.6%和7.3%,检出限为0.02mg/kg。     

Preliminary study of HCHO spatial and temporal distribution from Coastal to Plateau areas in Antarctica

Formaldehyde concentrations were determined in over 1800 snow samples (snowpit, firn cores and superficial snow) from Antarctica by a sensitive spectrofluorimetric Flow Injection Analysis method. The method performances (detection limit: 55?ng/L; reproducibility: 2.5% at 1?µg/L level; linear range: 0.1–3000?µg/L) allowed a reliable determination of formaldehyde content in all the collected samples. The range of determined concentrations was 0–70?µg/L with a mean concentration of 7.7?µg/L and a median concentration of 5.8?µg/L. The formaldehyde background level was estimated at a few micrograms per liter in coastal and plateau areas of Northern Victoria Land. In some stations the background values are modulated by HCHO deposition events recurring over relatively large time periods.     

Application of DSC as a tool for honey floral species characterization and adulteration detection

The thermal behaviour of authentic honeys and sugar syrups (industrial and homemade) was investigated by DSC. To confirm the first previous results concerning the effect of adulteration on the thermal behaviour of authentic honeys, 30 honey samples (Robinia, Lavender, Chestnut and Fir) were analyzed by DSC and their T _g were measured following a suited experimental protocol. The results indicated that this parameter was useful to characterize and to distinguish significantly these varieties between them. Applied to honey samples artificially adulterated with different industrial syrups, DSC showed a detection level of 5–10% depending on the type of syrup. An endothermic phenomenon occurring between 40–90°C during the heating was studied by TMDSC and a new thermal transition similar to a glass-transition was highlighted.This revised version was published online in November 2005 with corrections to the Cover Date.     

Examination of proficiency and control recovery data from analyses for pesticide residues in food: sources of variability.

We examined a number of large proficiency and control databases supporting the values reported for pesticide residues in agricultural commodities at fractions of a part per million (mg/kg). The average recovery from >100,000 recovery records in 13 databases was 94%. The overall average single-value relative standard deviation (RSD) of the reported recoveries was 17% at a mean concentration (C) of about 10(-7) (0.1 mg/kg). The average apparent HORRAT value (RSD found/RSDR predicted from the Horwitz formula [2*C(-0.1505)]) was 0.8. Analysis of variance indicated that about 60-70% of the variance could not be associated with any particular factor or combination of factors-analyte, commodity, method, laboratory, concentration, database, or their interactions. The most predominant factor, analyte, and its third-order interaction with laboratory and concentration contributed most of the assignable variance. These findings suggested that most of the variability of trace analysis for pesticide residues is "random" in the sense of being inherent and not assignable to specific factor fluctuations.     

Physicochemical profile studies of soil along the banks of Ubu river in Ekwusigo and Nnewi local government areas of Anambra State of Nigeria

A physicochemical profile study on the soil along the banks of the Ubu river that runs across Ekwusigo and Nnewi Local Government Areas (LGA) of Anambra State of Nigeria was investigated for possible evidence of industrial waste disposal by the various large to medium scale industrial activities taking place within the two LGAs. When compared with soil samples from Uzoakwa Ihiala (pH 5.44) with little or no industrial activities, the soil along the banks of the course of the river were found to be more acidic with mean pH values that are lower than 4.7. Similarity in mean sulphate (7.01 mg/kg), phosphate (12.95 mg/kg) and chloride (242 mg/kg) contents was observed between the soils from the banks at Nnewi with those of the Uzoakwa Ihiala that was used as control. This was attributed to contributions from domestic sources rather than from industrial sources, and partly to the similarity of their soil chemistry that may be indigenous to both areas. Electrical conductivity values (55 -74 microS/cm) show that the ionic content of the soil is lower than those of the control (129 microS/cm). This may have been explained by the higher extractible Ca (175.73 mg/kg), K (34.32 mg/kg), and Mg (1.94 mg/kg) recorded for the control. The abundance of the metals extractible from the soils of the river banks follow the sequence Ca>K>Na>Fe. Results for the digested soil samples show that Fe is the most abundant metal in the soil with mean values that are close to 13,000 mg/kg, but is much lower than the mean value of 39,210 mg/kg recorded for the control. Both bank and control samples can be characterized as ferrous. The relative abundance of metal ions observed in the digested soil samples from the river banks follow the sequence Fe>Al>Ca>Na>K>Zn>Cr. Values of 4,565 mg/kg and 300 mg/kg were recorded for total hydrocarbon content and lead respectively for soils around Cento Group, indicating that there were industrial waste disposal or spillages on soil around the area, which was not observed in other areas.