A provenance study of coffee by photon activation analysis

Photon activation analysis (PAA) is a multi-elemental radioanalytical technique in trace elements analysis with high accuracy and precision. Researchers at the Idaho accelerator center performed PAA analysis on coffee samples from several locations around the world as an initial step in assessing the relationship between trace elements in illicit drugs and the soils in which they were grown. The preliminary results show coffees from different locations have different concentrations of trace elements. In the three cases where we have soil samples, the matrices of elements in the coffee samples are closely related to the matrices of the elements of the local soil samples. The majority of trace elemental content is similar to that of the local soil sample in which the coffee is planted. It may be that coffee assimilates numerous elements from the soil where it is grown in similar ratios as is found in the soil. Thus, it is conceivable that the elemental content could serve as “fingerprint” to trace the origins of the coffee. To verify our analytical results we applied X-ray fluorescence (XRF) methods as well. Our PAA results are consistent with XRF experimental data. The future of tracing the origin of illicit drugs with the PAA technique is promising.     

Elemental analysis of soils from Toshki by using instrumental neutron activation analysis techniques

Instrumental neutron activation analysis has allowed performing a complete characterization of the chemical composition of thirty soil samples soil samples from ten locations collected from the Toshki area in Upper Egypt. The samples were irradiated with thermal neutrons at the Mainz TRIGA research reactor. Gamma-ray spectra were recorded using a high efficiency HPGe detector to determine the contents of major, minor and trace elements in these samples. As a result of the analysis, altogether 32 elements were identified qualitatively and quantitatively. These elements are: Al, As, Ba, Ca, Ce, Co, Cr, Cs, Eu, Fe, Ga, Hf, K, La, Lu, Mg, Mn, Na, Nb, Nd, Rb, Sc, Sm, Sn, Ta, Ti, Th, U, V, Yb, Zn and Zr. In several cases, X-ray fluorescence analysis was used for comparison. The results obtained for U and Th were compared with data reported in literature.     

An accurate quantitative analysis of polymorphs based on artificial neural networks

Measurement precision based on homogeneous and accurate standard samples has been reported to result in significant improvement in the sensitivity and accuracy of the quantitative analysis of polymorphic mixtures. The purpose of this study was to further improve the accuracy of the quantitation based on data processing by artificial neural networks (ANNs), using such high quality standard samples. Homogeneous powder mixtures of - and γ-forms of indomethacin (IMC) at various ratios (0–50% -form content) were subjected to X-ray powder diffractometry. The two diffraction peaks selected as the best combination in multiple linear regression (MLR) were used in the ANN with an extended Kalman filter as a training algorithm. The results obtained by ANN had better predictive accuracy at lower contents (0–5%) compared to those of MLR. ANNs for the diffraction data based on high quality standard samples provide an extremely precise and accurate quantification for polymorphic mixtures.     

Flow injection analysis of high chloride levels in electroplating baths using on-line dialysis and potentiometric detection

A method for the flow injection analysis (FIA) of high concentrations of chloride in electroplating baths using potentiometric detection is proposed. The system includes a unit of dialysis to promote dilution of samples and a tubular electrode with an homogeneous crystalline membrane as detector. The system was optimized in order to analyse samples within a broad range of concentrations and at high levels of chloride, thereby making pretreatment of the samples unnecessary. It results in a simple manifold applicable over the 4.0×10^–2 and 3.0 mol L^–1 range with a throughput of about 30 samples/h. Seven different plating bath samples were analysed by the proposed method and the quality of the results compared with those obtained by the conventional procedure. Satisfactory agreement was observed.     

Zilpaterol—a new focus of concern in residue analysis

The results of an investigation on the residue behaviour of Zilpaterol in urine, plasma, muscle, liver, kidney and retina of cattle and pig are presented. Two heifers and 16 pigs were orally treated with ZILMAX™. The animals were slaughtered after withdrawal times varying from 1 to 10 days. The Zilpaterol concentrations in the samples were measured by means of LC-MS/MS. Zilpaterol was detectable at each point of time examined in all matrices but plasma after a withdrawal period of 10 days. A strong accumulation of Zilpaterol was observed in retinal tissue, where persistently high concentrations were measured.     

Dynamic calibration and automated instrumental analysis

The role of the analytical machine and the computer command in automated instrumental analysis are discussed and the eminent role of true and adapted reference material is stressed. The application of charts in process control (SPC) neglects the analytical potential which is contained in trends. As an improvement on-line calibration is suggested employing a set of high quality reference samples in a moving manner with subsequent regressions after each new analysis of one of the members of the set. The number of members of the set and the sequence of their analysis determine the corrective force of the system and weighted regression provides for large concentration ranges. The performance of the correction system was tested by simulation and results of application to OES and XRF in practice over long periods of time are communicated. The analysis of steel and oxide matter in form of iron ore sinter and blast-furnace slag resulted at any time in negligible bias between nominal and observed values of the set of reference samples. Residual standard deviations near or equal to the repeatabilities of the methods were observed.     

Chemical analysis of archaeological copper and brass fron northeastern Ontario

Since it is now possible, with some reliability, to separate native from European copper using chemical analysis, we now sort archaeological copper into geological (North American) or smelted (European) groups and thereby help address issues relating to the cultural impact of earliest aboriginal — European contact in northeastern Ontario. Twenty six metal samples from 11 archaeological sites, dating from the 17th to 19th centuries, were analyzed by INAA. The results were compared with reference data for native copper and European trade copper and indicate that of the 17 copper samples in the suite, an archaeologically-unexpected high number of 12 were made of native copper. The majority of these samples (7 of 8) derived from the post-contact early 17th century Providence Bay Odawa village. The remaining samples were made of brass (8) and zinc (1). Two of the brass samples, from Point Louise, have remarkably similar chemistries and probably came from the same object, or at least from the same batch of brass.     

Determination of iodine in diverse botanical and dietary matrices by pre-irradiation combustion followed by neutron activation analysis

Summary The method chosen for determination of iodine in this investigation is an extension of an existing analytical technique to food samples which was developed for environmental samples. The method is based on pre-irradiation combustion of the sample to liberate iodine, trapping the iodine on charcoal, and quantitating the element by neutron activation analysis (NAA). Existing botanical and dietary reference materials were used to check the validity of the method. Several mixed diet samples with high fat content from the U.S. Total Diet Study and composites of cereals with both low and high iodine content were analyzed. This method of pre-irradiation combustion followed by NAA has been shown to be a viable technique for the determination of iodine in dietary samples. However, with a detection limit of about 50 ng of iodine, large amounts of sample (>1 g) are typically required for each determination.     

The external quality assurance of phylloquinone (vitamin K1) analysis in human serum

The vitamin K external quality assurance scheme (KEQAS) aims to assist in the harmonization of phylloquinone (vitamin K₁) analysis in order to improve the comparability of clinical and nutritional studies. Serum samples were despatched to 17 groups from eight countries during 2000–2006. Using pilot data (1996–1999), an analytical performance target of 20% absolute difference from the all‐laboratory trimmed mean (ALTM) was assigned and formed the basis for interlaboratory comparison. Assay specificity, analytical bias and assay performance were evaluated. From 21 batches of samples distributed, 414 results were reported of which 2.7% were outliers. The mean interlaboratory absolute difference from the ALTM was 21.7% with 47% of groups consistently meeting the performance target. The mean interlaboratory coefficient of variation was 29.6%. The false positive rate for phylloquinone depleted samples was high at 35%. Bias was found to be independent of HPLC‐detector type (fluorescence vs electrochemical). Assay characteristics for the measurement of phylloquinone in human serum compare favourably with methods for analytes at equivalent concentrations. The high proportion of false positive results suggest that poor assay specificity at low phylloquinone concentrations is a common problem, which in the clinical setting could lead to underreporting of vitamin K deficiency. Copyright © 2009 John Wiley & Sons, Ltd.     

A new highly efficient set-up for cyclic and pseudocyclic short time activation analysis with high count rates

A new counting geometry with a simple sample changer was constructed to enable cyclic and pseudocyclic short-time activation analysis. With the new system it is possible to cycle a sample, or successively an indefinite number of samples up to 20 times. The sample changer acts at the same time as sample catcher for two n-type HPGe detectors and can release the sample into a well-type HPGe detector. The new system enables the simultaneous counting of the irradiated samples by means of two endcap HPGe detectors, and subsequent counting by means of the well HPGe detector or both detector types. A well detector ensures a high counting efficiency which improves the sensitivity of a large number of short lived nuclides. Some standard reference materials (i.e., BCR-176, NIST SRM 1633b, IAEA-336, 335b, 335c) were prepared and analysed in replicates. The results indicate that up to 46 nuclides can be determined in BCR-176 if the samples are irradiated with and without the⁶LiD converter. An automatic evaluation programme was developed that determines the FWHM calibration parameters for each spectrum for accurate peak-area estimation at high count rates.     

Thermodynamics of starch-water systems: An analysis from solution-gel model on water sorption isotherms

The water sorption of several starch samples and resistant starch (RS) samples were analyzed using an equilibrium solution-gel structure model and the results were compared to various sorption theories. It is found that the water sorption relations to water activity in starch in the high water content region could be properly described by the equilibrium two-phase structural model. The results suggested that favorable starch-starch interaction determined the formation of starch gel in water. The gel structure had a high molecular modulus of 10⁸ Pa and thus had limited water sorption capability. Part of the starch also exhibited the solution properties with water due to chain ends and defects of the gel structure. Despite the unfavorable starch-water interaction, starch-water solution might be formed due to the predominant contributions from the entropy of mixing. The solution phase was responsible for the rapid increase of water sorption at high water activity. It was also demonstrated that the starch could maintain a maximum dynamic unfreezable water up to ≈ 36%, which was consistent with the DSC measurements. © 1996 John Wiley & Sons, Inc.     

Needle microextraction trap for on-site analysis of airborne volatile compounds at ultra-trace levels in gaseous samples

Different capillary needle trap (NT) configurations are studied and compared to evaluate the suitability of this methodology for screening in the analysis of volatile organic compounds (VOCs) in air samples at ultra-trace levels. Totally, 22 gauge needles with side holes give the best performance and results, resulting in good sampling flow reproducibility as well as fast and complete NT conditioning and cleaning. Two different types of sorbent are evaluated: a graphitized carbon (Carbopack X) and a polymeric sorbent (Tenax TA). Optimized experimental conditions were desorption in the GC injector at 300°C, no make-up gas to help the transport of the desorbed compounds to the GC column, 1 min splitless time for injection/desorption, and leaving the NT in the hot injector for about 20 min. Cross-contamination is avoided when samples containing high VOC levels (above likely breakthrough values) are evaluated. Neither carryover nor contamination is detected for storage times up to 48 h at 4°C. The method developed is applied for the analysis of indoor air, outdoor air and breath samples. The results obtained are equivalent to those obtained with other thermal desorption devices but have the advantage of using small sample volumes, being simpler, more economical and more robust than conventional methodologies used for VOC analysis in air samples.     

Total reflection X-ray fluorescence analysis of river waters in its stream across the city of Cordoba,in Argentina

The aim of this work was to analyze the composition of river waters and to study their quality by detecting possible contaminants. The samples were taken at 32 points of the Suquía River in its stream across the city of Córdoba (in the Province of Córdoba, Argentina). The samples were analyzed with total reflection X-ray fluorescence (TXRF) using beam guides. Beam guides made of two Si plate reflectors were used as sample carriers and to guide the X-ray photons to the sample; the measurements were taken using the characteristic configuration that ensures the best excitation and detection conditions (in TXRF). The analyses were carried out by preconcentration of the water samples and by adding an internal standard (Gallium); small amounts of samples (30 μl) were deposited on the Si reflector plate and they were then analyzed in the total reflection regime. Spectra were analyzed with standard methods using conventional programs. The results show interesting behaviors of the concentration of trace elements along the river: elements of low atomic number (such as Ca, Cl, S, K) present higher concentrations as compared to high Z elements (such as Fe, Zn, Br, Sr); the concentrations of light elements follow a similar behavior along the stream, the same situation is observed in the set of elements with high atomic number. Some samples present high concentrations in certain elements indicating possible sources of contamination.     

Solid-phase extraction for metabolomic analysis of high-salinity samples by capillary electrophoresis-mass spectrometry

Environmental samples such as soil solutions contain inorganic ions such as NH4(+), K(+), Na(+), NO3(-), and PO4(3-) in high concentrations, which must be removed prior to capillary electrophoresis-mass spectrometry analysis to obtain accurate results. However, the separation of these inorganic ions from ionic metabolites, which are the target compounds in capillary electrophoresis-mass spectrometry analysis, is difficult because the physicochemical properties of the inorganic ions are similar to those of the ionic metabolites. In this study, we used various solid-phase extraction (SPE) columns for the purification of the samples containing inorganic ions in high concentrations. We found that cation-exchange SPE columns successfully filtered out the inorganic ions while retaining most of the organic compounds, which were easily collected with high recovery rates. In addition, 17 cationic metabolites in the soil solution were quantified by CE-MS analysis following the SPE purification process. The results suggest that our method can be used to analyze other environmental samples containing inorganic ions in high concentrations.     

Determination of cadmium in soils by neutron-activation analysis

A radiochemical neutron-activation method for the determination of cadmium in soils is presented. The irradiation is carried out in a neutron flux with a high epithermal component, taking advantage of the high ratio of the resonance-activation integral to the thermal-neutron cross-section for (114)Cd to obtain an increased sensitivity. The irradiated samples are decomposed with hydrofluoric acid-nitric acid and cadmium is separated by anion-exchange. Zinc may also be determined. There is good agreement with results obtained by atomic-absorption spectrophotometry based on solvent extraction separation of cadmium.     

Turbidimetric determination of sulphate in plant digests and natural waters by flow injection analysis with alternating streams

An improved flow injection system with alternating streams of reagents is described for the turbidimetric determination of sulphate. Samples are injected into an inert carrier stream which is mixed with barium chloride to form a barium sulphate suspension. The range of the method can be extended to low concentrations by continuously adding sulphate to the sample carrier stream. System performance is improved by automatic alternate pumping of the reagent stream and an alkaline EDTA solution at high flow rate. All operations are controlled by an electronically-operated proportional injector-commutator. Even after routine analysis of 3000 samples of natural waters and plant digests, baseline drift was not observed. The proposed method is suitable for 120 samples per hour with a relative standard deviation less than 1% for sulphate concentrations in the range 1–30 ppm (waters) or 5–200 ppm (plant digests). The results compare well with those obtained by standard manual procedures.     

Approaches to dioxin analysis by HRGC-HRMS and hybrid HRGC-MS-MS

A hybrid mass spectrometer with an EBQQ configuration was used to investigate two approaches to trace dioxin analysis: high resolution gas chromatography – high resolution mass spectrometry (HRGC-HRMS) and high resolution gas chromatography – mass spectrometry – mass spectrometry (HRGC-MS-MS). It is shown that selected ion monitoring (SIM) HRGC-HRMS exhibits better selectivity for dioxins separated on a cyanopropyl column than is otherwise obtained under medium resolution mass spectrometry (3,000 resolution), while optimization of conditions for HRGC-MS-MS allowed the observation of 350 femtograms of the highly toxic 2,3,7,8-TCDF at a S/N ratio of 5:1. Both methods were applied to environmental samples with good results.     

Flow-injection analysis of serum urea using o-phthalaldehyde and naphthylethylenediamine

An analytical procedure is developed for the determination of urea using flow injection analysis. The methodology is based on the color that develops (lambda(max), 517 nm) when urea reacts with o-phthalaldehyde in the presence of naphthylethylenediamine under acidic conditions. Calibration curves are found to be linear up to 51 mg urea N/dl when the FIA manifold is operated at 42 degrees , utilizing 90-mul samples and a flow-rate of 0.44 ml/min. By manual injection up to 40 samples can be analysed per hour. Recovery yields varied between 95-99%. The within day CV was 0.5-2.2% whereas the day to day CV was 2.1-3.9%. When applied to the analysis of urea in serum samples, excellent correlations (0.998) are obtained when the FIA results are compared with those obtained for the same serum samples analysed by the free urease/Berthelot's and the hospital method (employing the Abbot Bichromatic Analyser). Interferences are observed with sulphur compounds such as sulphanilamide (0.76 mg/dl) as well as with many amino acids but at relatively high concentrations (21 mg/dl).     

耐压多样品微量衍生反应装置在气相色谱-质谱联用法分析极性杂环胺中的应用

设计并制作了耐压多样品微量衍生反应装置。在该装置中采用N-(叔丁基二甲基硅烷基)-N-甲基三氟乙酰胺(MTBSTFA,含1%叔丁基二甲基氯硅烷)硅烷化试剂高温衍生极性杂环胺,衍生产物可以直接在气相色谱-质谱联用仪上分析。使用该装置,既可以在比试剂沸点高的温度下实现衍生反应,也可以实现多个微量样品的同时衍生。着重考察了衍生化过程中反应瓶的顶空体积、试剂蒸发面积、温度、时间等实验条件的影响。结果表明,在90 ℃衍生时,与普通衍生装置相比,使用耐压衍生装置可以有效地减小挥发损失,显著增大衍生产量;在150 ℃衍生时,由于试剂挥发损失严重导致普通衍生装置无法使用,而采用耐压衍生装置却可以实现定量衍生,但通过加温加压方式来加快衍生反应速率的效果并不十分明显。     

Thermo-XRD analysis of the adsorption of Congo-red by montmorillonite saturated with different cations

The adsorption of the organic anionic dye Congo red (CR) by montmorillonite saturated with Na⁺, Cs⁺, Mg²⁺, Cu²⁺, Al³⁺ and Fe³⁺ was investigated by XRD of unwashed and washed samples after equilibration at 40% humidity and after heating at 360 and at 420°C. The clay was treated with different amounts of CR, most of which was adsorbed. Clay samples, untreated with CR, after heating showed collapsed interlayer space. Unwashed and washed samples, which contained CR, before heating were characterized by three peaks or shoulders, labeled A (at 0.96-0.99 nm, collapsed interlayers), B (at 1.24-1.36 nm) and C (at 2.10-2.50 nm). Peak B represents adsorbed monolayers of water and dye anions inside the interlayer spaces. Peak C represents interlayer spaces with different orientations of the adsorbed water and organic matter. Diffractograms of samples with small amounts of dye were similar to those without dye showing peak B whereas diffractograms of most samples with high amounts of dye showed an additional peak C. Heated unwashed and washed samples were also characterized by three peaks or shoulders, labeled A' (at 0.96 nm), B' (at 1.10-1.33 nm) and C' (at 1.61-2.10 nm), representing collapsed interlayers, and interlayers with charcoal composed of monolayers or multilayers of carbon. When the samples were heated from 360 to 420°C some of the charcoal monolayers underwent rearrangement to multilayers. In the case of Cu the charcoal decomposed and oxidized. The present results show that most of the adsorbed dye was located inside the interlayer space.This revised version was published online in November 2005 with corrections to the Cover Date.