Principal component analysis and hierarchical cluster analysis for homogeneity evaluation during the preparation of a wheat flour laboratory reference material for inorganic analysis

The development of a homogeneity study during the preparation of a wheat flour laboratory reference material (LRM) for use in the quantification of metals and metalloids is reported. Inductively coupled plasma optical emission spectrometry (ICP OES) was used with validation performed using a certified reference material of wheat flour furnished by the National Institute of Standards and Technology (NIST). Copper, iron, manganese, phosphor, strontium and zinc were studied in a within-bottle homogeneity test whereas barium, copper, iron, zinc, manganese, strontium, phosphor and calcium were included in a between batch homogeneity study. Standard univariate analysis of variance (ANOVA) was performed for all analytes. Furthermore an alternative multivariate analysis for homogeneity is proposed by performing ANOVA of principal component scores and by inspection of principal component score graphs and hierarchical cluster analysis dendrograms. The ANOVA F-tests performed on both, the univariate and multivariate parameters, were not significant at the 95% confidence level and indicated homogeneous wheat flour samples. A 10 kg amount of material was processed, which was distributed in 100 bottles, each containing 100 g. For the between-bottle homogeneity test, three replicates were taken from each of 10 bottles selected of the 100 bottles obtained. The results were evaluated using an F-test, which demonstrated no significant difference for the between-bottle results. It is indicative that this material is homogeneous. Afterwards, the influence of the sample mass on the homogeneity of the material was also evaluated by quantification of the elements for 100, 300, 500, 700 and 1000 mg sample masses with all the experiments being performed in triplicate. The F-test was also used for evaluation of these results and demonstrated that the material is homogeneous for masses taken in the 100 to 1000 mg range. All these results were further evaluated employing the principal component analysis (PCA) and hierarchical cluster analysis (HCA) multivariate techniques. Both techniques also demonstrated that the material is perfectly homogeneous for use as laboratory reference material.     

Direct analysis of trace level bisphenol A,octylphenols and nonylphenol in bottled water and leached from bottles by ultra‐high‐performance liquid chromatography/tandem mass spectrometry

A high‐throughput method was developed for the direct analysis of trace level bisphenol A (BPA), 4‐n‐octylphenol (4‐n‐OP), 4‐tert‐octylphenol (4‐t‐OP) and 4‐n‐nonylphenol (4‐n‐NP) in water samples by ultra‐high‐performance liquid chromatography/tandem mass spectrometry (uHPLC/MS/MS) using an isotope‐labeled internal standard. Aliquots of water samples were spiked with the internal standard and analyzed without sample cleanup or enrichment. All target analytes were chromatographically separated within 3 min and detected using the highly selective multiple reaction monitoring (MRM) detection mode. The method detection limits were statistically calculated and ranged from 0.040 ppb (BPA) to 0.057 ppb (4‐n‐NP). Excellent correlation of determination was achieved for each analyte with r greater than 0.995. Precision was achieved within 8% relative standard deviation (RSD) for all analytes, and recoveries from spiked samples ranged from 97% to 106.2% except for 4‐n‐OP which may be corrected by using an isotope‐labeled analog as internal standard. This method was used for analyzing eight randomly selected bottled water samples and found no detectable target analytes. This method was also used to analyze target analytes leached from bottles (6 low cost bottles and 6 brand‐name baby‐feeding bottles). Low levels of BPA were found in three bottles after they had been heated in a microwave oven, and a trace amount of 4‐n‐NP was also found in three bottles. 4‐t‐OP, which has not been reported as a leachable chemical, was found in two brand name baby‐feeding bottles from the same manufacturer, and was confirmed with bottles from different batches. Copyright © 2010 John Wiley & Sons, Ltd.     

An actual case of examination of counterfeited whisky

In this paper it is presented a case of falsification of whisky in which empty bottles of genuine spirit were re-used as containment for low price whisky. Activation analysis was made of bottle-caps (a lead and tin alloy) of counterfeited bottles and of genuine imported ones as well as of a stock of bottle-caps found at the place where the material was apprehended. Results for trace and main elements indicated common origin for the bottle-caps in the counterfeited bottles and the ones found at the place where the material was apprehended and different origin for the bottle-caps in the imported bottles, indicating re-use of the imported bottles.     

The Stability of Precipitation Samples under Field Conditions

Abstract

Eight wet-only samplers. placed in one location were used to sample precipitation. Subsamples were taken from the sample bottles directly after the precipitation event and at regular intervals up to a period of 2100 hours and analysed, while the samples stayed in the samplers under field conditions.

Outliers were deleted by means of conventional statistical techniques. The resulting data base was tested by means of the F-test for consistency and for changes in the chemical composition of precipitation samples directly after sampling or after an extended stay under field conditions. Eighty-one percent of the samples showed consistent results and no clear indication of chemical changes was found.

Regression analysis indicated that the uncertainties for samples analysed after 1 week are less than 5% generally for the bulk elements and less than 14% for the trace elements. After a period of 400 hours the uncertainties for the buld elements increase to a level of 5–10% and 5–30% for the trace elements.

Contamination, as a result of handling the samples to obtain subsamples, seems the main cause for the increase of the concentrations which was observed.

Contamination during sample pretreatment and analysis in the laboratory is probably of minor importance.     

茶碱标准物质的研制与定值

建立了茶碱标准物质的制备和定值方法.将市售茶碱原料纯化、干燥、混匀后.分装成500瓶样品.随机抽取其中11瓶做均匀性检验.经F检验和T检验.结果表明在95%置信范围内样品的均匀性良好;稳定性检验按短期稳定性(1月)和长期稳定性(12月)分别进行,长期稳定性结果通过了T检验,表明在20℃条件下茶碱的稳定期不少于12个月....     

Preparation and homogeneity study of a mussel candidate reference material for certification of organotin compounds

Organotin compounds are currently determined in various environmental matrices (in particular water, sediment and shellfish) to form the basis of control measures for the levels of contamination, as required in some EC Directives. Accurate measurements are a prerequisite for the enforcement of this legislation, which implies that good quality control of determinations should be ensured. One of the tools for achieving accuracy is to use certified reference materials (CRMs). With regard to tin species, however, CRMs are rather scarce and mainly concern sediment and fish matrices certified for their butyltin content. The present study deals with the preparation of a mussel candidate reference material and the verification of its homogeneity prior to the certification of the contents of butyl- and phenyl-tin compounds. 100kg of mussels (Mytilus edulis) were collected, carefully washed with fresh water in order to eliminate matrix salts and immediately frozen by immersion in liquid nitrogen. The mussels were shelled (in the frozen state) and the edible part was stored in thermally sealed polyethylene bags which were stored at –25 °C. The frozen material was ground in a Teflon-coated grinding mill, spread on sterilized flat trays and freeze-dried. The freeze-dried material was then ground for 15 days in a zirconia ball mill and sieved on a titanium sieve to separate the fibrous part. Successively, the material was mixed for 15 days under argon atmosphere in a special polyethylene-lined mixing drum and bottled in brown Pyrex-glass bottles. 21 bottles were selected during the course of the bottling procedure to verify the within- and between-bottle homogeneity of the overall batch. The within-bottle homogeneity was verified by determining the organotin (butyl- and phenyltins) content for subsamples of 500 mg in ten replicates from one bottle, whereas the between-bottle homogeneity was controlled by one organotin measurement from each of 20 bottles. The analyses were performed by GC-MS. The results showed that the homogeneity of the material makes it suitable as a candidate reference material.     

Assessing bias in total mercury results after removing a subsample from the bottle

U.S. EPA Method 1631 for total mercury (THg) analysis in water recommends that bromine monochloride (BrCl) be added to the original bottle in which the sample was collected, to draw into solution any Hg that may have adsorbed to the bottle walls. The method also allows for the removal of a subsample of water from the sample bottle for methylmercury (MeHg) analysis prior to adding BrCl. We have demonstrated that the removal of a subsample from the sample bottle prior to THg analysis can result in a positive concentration bias. The proposed mechanism for the bias is that ‘excess’ inorganic Hg, derived from the subsample that was removed from the bottle, adsorbs to the bottle walls and is then drawn into solution when BrCl is added. To test for this bias, we conducted an interlaboratory comparison study in which nine laboratories analysed water samples in fluorinated polyethylene (FLPE) bottles for THg after removing a subsample from the sample bottle, and analysed a replicate sample bottle from which no subsample was removed. We received seven complete data sets, or 63 unique sample pairs. The positive concentration bias between the bottles was significant when comparing all samples in aggregate (1.76 ± 0.53 ng/L after subsample removal, 1.57 ± 0.58 ng/L with no subsample removal, P < 0.05), however when comparing each of the three samples individually, the only significant bias was in the saline sample (Site UJ; 1.51 ± 0.31 ng/L after subsample removal, 1.32 ± 0.47 ng/L with no subsample removal, P < 0.05). Based on the findings presented here, we conclude that water chemistry, volume of water poured off, and the sample storage temperature explain some but not all of the observed bias, and we recommend collecting THg and MeHg samples in separate bottles whenever possible.     

High‐Throughput Synthesis and Screening of Combinatorial Heterogeneous Catalyst Libraries

In less than one minute the catalytic activity and selectivity of a single catalyst was measured in combinatorial libraries of ternary Rh‐Pd‐Pt‐Cu alloys. Only slightly more than two hours were needed to complete a library with 136 elements. The elements of the libraries (ca. 2–4 μg of material) are contained in a two‐dimensional array synthesized by a thin‐film technique. The analysis was performed by a scanning mass spectrometer (see picture).     

4,9-脱水河豚毒素国家标准样品的研制

研制4,9-脱水河豚毒素国家标准样品。以河豚鱼卵巢为原料,提取制备4,9-脱水河豚毒素,采用红外光谱(IR)、高分辨质谱和核磁共振谱(NMR)进行结构确证。样品分装成140瓶后,采用柱后衍生–高效液相荧光法进行均匀性、稳定性检验和定值分析。从样品中随机抽取15瓶进行均匀性检验,经F检验表明在95%的置信区间范围内样品均匀性良好;稳定性考察按照40℃加速试验稳定性(6个月)进行,结果表明在考察期间内样品稳定性良好;标准样品经国内8家具有分析资质的实验室进行协同定值,并评定了定值结果的不确定度,4,9-脱水河豚毒素标准样品定值结果为97.77%,相对扩展不确定度为0.4%(k=1.96)。该标准样品达到国家标准样品的技术要求,可用于有关脱水河豚毒素的方法校正和质量控制。     

Preparation and certification of hijiki reference material, NMIJ CRM 7405-a, from the edible marine algae hijiki (Hizikia fusiforme)

A certified reference material, NMIJ CRM 7405-a, for the determination of trace elements and As(V) in algae was developed from the edible marine hijiki (Hizikia fusiforme) and certified by the National Metrology Institute of Japan (NMIJ), the National Institute of Advanced Industrial Science and Technology (AIST). Hijiki was collected from the Pacific coast in the Kanto area of Japan, and was washed, dried, powdered, and homogenized. The hijiki powder was placed in 400 bottles (ca. 20 g each). The concentrations of 18 trace elements and As(V) were determined by two to four independent analytical techniques, including (ID)ICP-(HR)MS, ICP-OES, GFAAS, and HPLC-ICP-MS using calibration solutions prepared from the elemental standard solution of Japan calibration service system (JCSS) and the NMIJ CRM As(V) solution, and whose concentrations are certified and SI traceable. The uncertainties of all the measurements and preparation procedures were evaluated. The values of 18 trace elements and As(V) in the CRM were certified with uncertainty (k = 2).     

New reference material for analysis of elements in glutinous rice produced at the National Institute of Metrology (Thailand)

Reference materials play an important role for evaluating the accuracy of analytical results, and are essential parts of good laboratory practice. They represent a key tool for quality control of chemical analyses. In Thailand, the demand of food and environmental reference materials is constantly increasing, and the National Institute of Metrology (NIMT, Thailand) is responding to the urgent needs for affordable materials, which require collaborative efforts at the national level. This paper describes the preparation of a new glutinous rice reference material, along with homogeneity and stability studies and the analytical work carried out for the certification of the contents of inorganic elements. The incurred material was collected from an actual rice paddy field. Material preparation along with homogeneity and stability testing were carried out at the Environmental Research Training Centre (ERTC). The homogeneity study was designed to have three experimental conditions; (A) 10 bottles of candidate materials being analyzed each with 2 replicates, (B) 20 bottles with 2 replicates, (C) 10 bottles with 7 replicates, in order to study the suitable treatments for homogeneity testing in the reference material production. It was shown that a minimum number of 10 bottles with duplicate analyses are enough to demonstrate the homogeneity of candidate reference material. Certification of a candidate reference material in a single laboratory using reference method was confirmed with an interlaboratory comparison participated by a certain number of well recognized testing laboratories in Thailand. Further elaborative results will be discussed.     

Effects of inhomogeneity and contamination in k<Subscript>0</Subscript>-INAA of low (K,Th, U)-content sand for the annual radiation dose determination in luminescence dating

It was demonstrated that for the determination of the annual radiation dose for use in luminescence dating of sediments, one should be aware of possible material inhomogeneities when applying analysis methods (such as k ₀-INAA) with sample intakes of the order of the gram (to be compared with Ge gamma-ray spectrometry in cylindrical or Marinelli geometry, the latter involving ∼1.5 kg material). Moreover, when trying to remove the inhomogeneity, care should be taken to avoid contamination of the elements investigated, especially in the case of low (K, Th, U)-content sand with a considerable abrasive action (such as the Ossendrecht coversand dealt with in the present work). Whereas contamination was indeed shown to happen when grinding the material in a porcelain mortar, a satisfactory technique proved to be agate-ball milling.     

Evaluation of relative comparator and <Emphasis Type="Italic">k</Emphasis><Subscript>0</Subscript>-NAA for characterization of Aboriginal Australian ochre

Ochre is a significant material in Aboriginal Australian cultural expression from ceremonial uses to its application on many types of artifacts. However, ochre is a complex material, with associated surrounding minerals potentially challenging the overall analysis. In recent literature several studies have attempted to characterize ochre by a variety of techniques to understand procurement and trade. However, ochre is difficult to differentiate on major elemental or mineralogical composition and requires a detailed analysis of its geochemical “fingerprint”. Neutron activation analysis (NAA) provides the high sensitivity (sub-ppm), precision and accuracy in multi-elemental analysis required for ochre. The elements of interest for ochre generally include rare earth elements (REEs) and certain transition metal elements as well as arsenic and antimony. Data from relative comparator NAA (MURR, University of Missouri, USA) is compared with data from k ₀-NAA OPAL (ANSTO, Lucas Heights, Australia). A discussion of the two methods will be examined for their utility in “fingerprinting” the provenance of ochre. The continuing importance of NAA to archaeometry will also be discussed.     

<Emphasis Type="Italic">Perna perna</Emphasis> mussel reference material: short term stability assessment

Instrumental neutron activation analysis was used at a 2-month long isochronous short term stability test performed on a Perna perna mussel candidate reference material. The assessment of the analysis of variance test, as well as, the normalized results to the control temperature showed no systematic changes in the concentration of Ag, As, Br, Co, Cr, Cs, Fe, Eu, La, Na, Rb, Se, Sc, Th and Zn during the test period. The result showed that the candidate reference material may be transported under normal transport conditions without significant changes in composition for the determined elements.     

Implementation of the <Emphasis Type="Italic">k</Emphasis><Subscript>0</Subscript>-NAA method by using <Emphasis Type="Italic">k</Emphasis><Subscript>0</Subscript>-IAEA software and the NAA#3 irradiation hole at the HANARO research reactor

This study intended to demonstrate the use of k ₀-IAEA software with the NAA#3 irradiation hole in the HANARO research reactor and the gamma-ray spectrometers at the NAA laboratory in the Korea Atomic Energy Research Institute (KAERI). NIST SRM 2586-Soil was chosen as a sample to validate the analytical protocol by using the k ₀-IAEA software. Twenty four elements were determined and the resultant deviations between the experimental results and the certified values were all within 10% except for Dy. In addition, an analysis of three types of synthetic multielement standards (SMELS) prepared by the Institute for Reference Materials and Measurements (IRMM) and Institute of Nuclear Science (INW) in Belgium was executed. The analytical results agreed well with the assigned values and the U-scores for most of the elements were lower than 2.     

New human hair certified reference material for methylmercury and trace elements

 A new human hair certified reference material (NIES CRM No. 13) for mercury speciation and trace element analysis was prepared at the National Institute for Environmental Studies (NIES), Environmental Agency of Japan. Scalp hair from Japanese males, which is identical with the original material for the previous human hair CRM (NIES CRM No. 5), was used. Special attention was paid to reduce contamination from a grinding vessel during the preparation procedure. A newly-prepared ceramic/Teflon disc mill was used for cryogenic grinding of the hair. 1,000 bottles (3 g each) were produced after sieving and blending of the hair powder. Certified values for total mercury and methylmercury, as well as other trace elements of toxicological and nutritional significance (antimony, cadmium, copper, lead, selenium, and zinc), were determined based on analyses from extensive collaborations. Reference values for 12 elements (aluminium, arsenic, barium, calcium, cobalt, iron, magnesium, manganese, silver, sodium, sulfur and vanadium) were also given. Received: 8 February 1996/Accepted: 4 April 1996     

罗丹明B纯度标准物质的研制

以商购罗丹明B为原料,进行重结晶提纯,制备罗丹明B纯度标准物质。采用红外光谱(IR)、高分辨质谱和核磁共振谱(NMR)进行定性分析。样品分装400瓶后,依据国家《一级标准物质研制技术规范》,采用液相色谱-二极管阵列法对随机抽取的15瓶样品进行均匀性检验,经F检验表明,在95%的置信区间范围内,样品均匀性良好。在室温下,经过30个月稳定性考察,结果表明样品稳定性良好。标准物质经国内8家具有分析资质的实验室进行协同定值,定值结果为99.0%,扩展不确定度为1.0%(k=2)。该标准物质达到了国家标准物质的技术要求,可用于有关罗丹明B的分析方法校正和质量控制。     

Measurement of the δ34S value in methionine by double spike multi‐collector thermal ionization mass spectrometry using Carius tube digestion

Methionine is an essential amino acid and is the primary source of sulfur for humans. Using the double spike (³³S‐³⁶S) multi‐collector thermal ionization mass spectrometry (MC‐TIMS) technique, three sample bottles of a methionine material obtained from the Institute for Reference Materials and Measurements have been measured for δ³⁴S and sulfur concentration. The mean δ³⁴S value, relative to Vienna Canyon Diablo Troilite (VCDT), determined was 10.34 ± 0.11‰ (n = 9) with the uncertainty reported as expanded uncertainties (U). These δ³⁴S measurements include a correction for blank which has been previously ignored in studies of sulfur isotopic composition. The sulfur concentrations for the three bottles range from 56 to 88 µg/g. The isotope composition and concentration results demonstrate the high accuracy and precision of the DS‐MC‐TIMS technique for measuring sulfur in methionine. Published in 2010 by John Wiley & Sons, Ltd.     

New human hair certified reference material for methylmercury and trace elements

A new human hair certified reference material (NIES CRM No. 13) for mercury speciation and trace element analysis was prepared at the National Institute for Environmental Studies (NIES), Environmental Agency of Japan. Scalp hair from Japanese males, which is identical with the original material for the previous human hair CRM (NIES CRM No. 5), was used. Special attention was paid to reduce contamination from a grinding vessel during the preparation procedure. A newly-prepared ceramic/Teflon disc mill was used for cryogenic grinding of the hair. 1, 000 bottles (3 g each) were produced after sieving and blending of the hair powder. Certified values for total mercury and methylmercury, as well as other trace elements of toxicological and nutritional significance (antimony, cadmium, copper, lead, selenium, and zinc), were determined based on analyses from extensive collaborations. Reference values for 12 elements (aluminium, arsenic, barium, calcium, cobalt, iron, magnesium, manganese, silver, sodium, sulfur and vanadium) were also given.     

Certified sediment reference materials for trace element analysis from the National Metrology Institute of Japan (NMIJ)

Two types of sediment reference material (NMIJ 7302-a and 7303-a) for trace elements analysis have been prepared and certified by the National Metrology Institute of Japan in the National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). The original materials were collected from a bay near industrial activity in Kyushu (NMIJ CRM 7302-a; marine sediment) and from Lake Biwa (NMIJ CRM 7303-a; lake sediment). The sediment materials were air-dried, sieved, homogenized, packaged in 1000 glass bottles (60 g each), and radiation sterilized. Certification of these CRM for trace elements was conducted by NMIJ, where each element was determined by at least two independent analytical techniques. Isotope-dilution inductively coupled plasma mass spectrometry (ICP–MS) was applied for certification of all the elements except mono-nuclide elements such as As and Co. Other techniques such as ICP–MS with quadrupole mass spectrometry and sector-field mass spectrometry, inductively coupled plasma atomic emission spectrometry (ICP–AES), and atomic absorption spectrometry (AAS), were also used. Certified values have been provided for 14 elements (Sb, As, Cd, Cr, Co, Cu, Pb, Hg, Mo, Ni, Se, Ag, Sn, and Zn) in both CRM.