Repeatability Standard Deviation Research Articles

Development of a hydrophilic magnetic amino-functionalized metal-organic framework for the highly efficient enrichment of trace bisphenols in river water samples

Bisphenols, a typical pollutant with endocrine acting the scientific attention for their ascertained toxicity and wide uses. The magnetic Zr-MOFs (Fe3O4@PDA@UiO-66-NH2), functionalized with amino groups and proved by a series of material characterization techniques, were successfully prepared as adsorbents for magnetic solid-phase extraction (MSPE) of five bisphenols (including bisphenol A, bisphenol B, bisphenol S, bisphenol AP and bisphenol AF) from water samples. Liquid chromatography coupled with tandem mass spectrometry was used for sample analysis and quantification. Good linearity was obtained for each analyte with correlation coefficients larger than 0.990. The low limits of detection (LOD) and qualification (LOQ) were 0.013–0.290 μg/L (S/N = 3) and 0.088–1.800 μg/L (S/N = 10), respectively. The repeatability standard deviations in spiked lake water samples were 0.57–1.67%. In addition, the amount of the materials (40 mg), the adsorption time (30 min), pH value (7), elution time (30 min) and elution solvent (methanol) were determined as the optimal parameters in bisphenol extraction. Satisfactory results were obtained when the developed MSPE method was applied to determine the five bisphenols in real lake water samples, and the maximum extraction efficiency was up to 78.2%. The developed MSPE method using the Fe3O4@PDA@UiO-66-NH2 as adsorbent provides time saving, high selectivity and sensitivity for the analysis of trace bisphenols, suggesting that the Fe3O4@PDA@UiO-66-NH2 had a broad application prospect in water analysis.

Simple Label-Free Electrochemical Immunosensor in a Microchamber for Detecting Newcastle Disease Virus

In this study, a simple, label-free, electrochemical immunosensor system, including a three-electrode transducer and a microchamber, was designed, fabricated, and integrated with focus toward the detection of Newcastle disease virus (NDV). The chicken egg yolk antibodies (IgY) against NDV were used as the biological recognition element, replacing purified IgG antibodies that require a complex extraction process and time-consuming. The IgY against NDV was immobilized on the sensor surface using PrA/GA and SAM/NHS approaches. The immunosensor showed high sensitivity with NDV concentrations ranging from 106 to 102 EID50/mL with good specificity, repeatability, and small standard deviations. Compared to traditional methods, the immunosensor with advantages such as simple fabrication, quick response, direct detection, and possibility for miniaturization by integrating the immunosensor with the microchamber is potential for applications in contamination studies and field measurements.

Development and validation of two robust simple chromatographic methods for estimation of tomatoes specific pesticides’ residues for safety monitoring prior to food processing line and evaluation of local samples

Combination of pesticides; acetamiprid, flutolanil and etofenprox are usually used for tomato fruits for protecting them against pest infection. Generally, pesticides, residues could be one of the health hazard sources. Two specific simple sensitive chromatographic methods are developed for simultaneous estimation of the concerning pesticides’ residues using simple economic steps of field sample preparation. The first method is HP- TLC method. Hexane: methanol: acetone: glacial acetic acid (8:2:0.5:0.1, by volume) is proposed as a developing system. The second one is RP- HPLC. Acetonitrile: water (75:25, v/v) is proposed as a mobile phase. The recommended methods are completely validated regarding ICH guidelines. Their means percentages and standard deviations of accuracy range 100.32 ± 0.89 to 99.27 ± 0.9. The methods’ repeatability and intermediate precision relative standard deviation percentages range 0.395–0.894. They are successfully applied for estimating the pesticides in pure and commercial forms and field samples.

A novel multiplex real-time PCR for the detection of Echinococcus multilocularis, Toxoplasma gondii, and Cyclospora cayetanensis on berries.

Foodborne parasites (FBP) are of major public health importance and warrant appropriate detection and control strategies. Most of the FBP considered for risk-ranking by a panel of experts are potentially transmitted via consumption of contaminated fresh produce, including berries. In this study we focused on the potential of three FBP, namely Echinococcus multilocularis, Toxoplamsa gondii, and Cyclospora cayetanensis, as contaminants of berries. Surveys to assess these parasites as contaminants of fresh produce in general, and berries in particular, are scanty or non-existent mainly due to the lack of optimized laboratory methods for detection. The aim of the present study was to develop and evaluate a novel multiplex qPCR for the simultaneous detection of E. multilocularis, T. gondii, and C. cayetanensis from berry fruits. The efficiency and linearity of each channel in the multiplex qPCR were within the acceptable limits for the range of concentrations tested. Furthermore, the method was shown to have good repeatability (standard deviation ≤0.2 Cq) and intermediate precision (pooled standard deviation of 0.3-0.6 Cq). The limit of detection was estimated to 10 oocysts for Toxoplasma and Cyclospora, and 5 eggs for Echinococcus per 30 g of raspberries or blueberries. In conclusion, evaluation of the present method showed that the newly developed multiplex qPCR is highly specific, precise, and robust method that has potential for application in food-testing laboratories.

Quantification of staphylococcal enterotoxin type A in cow milk by using a stable isotope-labelled peptide via liquid chromatography–tandem mass spectrometry

ABSTRACTIn this study, the staphylococcal enterotoxin type A (SEA) contaminant was quantified in cow milk by liquid chromatography–tandem mass spectrometry (LC–MS/MS) with the use of a stable isotope-labelled peptide of SEA as an internal standard. SEA was cleaned up in a two-step process that included pH control and trichloroacetic acid (TCA) precipitation. The pH control phase eliminated other proteins. TCA precipitation cleaned up SEA without special equipment. An appropriate enzyme-to-protein ratio maximised tryptic digestion. A desalting process guaranteed the stable retention of SEA-digested peptides. The coverage of amino-acid sequences (>10%) clearly identified the toxin’s presence. SEA was accurately quantified using LC-MS/MS based on a multiple-reaction monitoring mode. The developed method was validated based on spiked recovery tests at 50 and 100 µg kg−1 conducted with two samples collected on a daily basis for five days based on Japanese validation guidelines. The new method exhibited good accuracy which ranged from 80% to 82%. The relative standard deviations of repeatability were 13–14% and the relative standard deviations of within-laboratory reproducibility were 13–18%. These standard deviations satisfied the criteria of the Japanese validation guidelines. The quantification limit was estimated to be 10 µg kg−1.

Generation and characterization of monoclonal antibodies against thyroid-stimulating hormone for newborn screening of congenital hypothyroidism

ABSTRACT Congenital hypothyroidism (CH) is one of the most frequent inherited-metabolic diseases in the world, and the main cause of treatable mental retardation in children. Because signs and symptoms of this disease are often scarce and not easily recognizable, newborns are screened for the early CH detection at birth. The Center of Immunoassay (CIE) has developed the UMELISA® TSH Neonatal and UMELISA® TSH to determine neonatal thyroid-stimulating hormone (TSH) levels in dried blood and serum samples. Both reagent kits use the same polystyrene plates coated with anti-β-TSH monoclonal antibodies (MAbs), but one of these is commercially acquired. Obtaining appropriate anti-TSH MAbs at the CIE would guarantee economic independence and security in the production of these kits. Immunization of mice with TSH led to the generation of 7G11E3, an anti-β-TSH IgG1-secreting hybridoma. The high affinity of 7G11E3 MAb and its characteristic epitopic recognition explain its better performance when adsorbed to UMELISA® plates for capturing low amounts of TSH in comparison with the studied MAbs. Performance of assays using polystyrene plates coated with 7G11E3 MAb was studied. Recovery percentages (100.0–106.7% for UMELISA® TSH NEONATAL and 97.3–99.0% for UMELISA® TSH) and intra (5.2–7.9% for UMELISA® TSH NEONATAL and 3.2–5.3% for UMELISA® TSH) and inter (6.6–7.7% for UMELISA® TSH NEONATAL and 5.2–8.0% for UMELISA® TSH) coefficients of variation were similar to the ones described for the commercial kits. Limits of detection and quantification were 1.0 and 3.8 mIU/L for UMELISA® TSH NEONATAL, and 0.3 and 0.6 mIU/L for UMELISA® TSH, respectively. The results also showed high overall concordance between assays (n = 2 019, ρc = 0.90 for UMELISA® TSH NEONATAL and n = 200, ρc = 0.94 for UMELISA® TSH). The 7G11E3 MAb meets the requirements for its use in the plates of UMELISA® TSH kits for CH newborn screening in Cuba. Abbreviations: CECMED, Center for the State Control of Medicaments and Medical Equipment and Devices; CH, congenital hypothyroidism; CIE, Center of Immunoassay; CLSI, Clinical and Laboratory Standards Institute; CV coefficient of variation; DBS, dried blood spots; LOB, limit of blank; LOD, limit of detection; LOQ, limit of quantitation; SD, standard deviation; Sr, repeatability standard deviation; SUMA, Ultra Micro Analytic System; UMELISA, ultramicro enzyme-linked immunosorbent assay.

Immunoassay utilizing imaging surface plasmon resonance for the detection of cyclopiazonic acid (CPA) in maize and cheese.

α-Cyclopiazonic acid (CPA) is a tremorgenic mycotoxin produced by Aspergillus and Penicillium fungal species, commonly found on agricultural commodities or fermented food products. A sensitive and rapid imaging surface plasmon resonance (iSPR) assay was developed to detect CPA in maize and cheese by combining an indirect competitive immunoassay and signal amplification based upon a secondary antibody (Ab2) conjugated with gold nanoparticles. Matrix-matched calibration curves were used to determine CPA content in maize and cheese samples. Recoveries, at two spiking levels in maize and cheese, were 89 to 126%, with standard deviations of repeatability (RSDr) of less than 16%. The limits of detection were 17 and 6μg/kg in maize and cheese, respectively. To separate the CPA-contaminated samples from uncontaminated samples, a cutoff validation level of 40μg/kg was introduced. The assay was applied to samples of naturally contaminated maize and was compared with competitive inhibition enzyme-linked immunosorbent assay (CI-ELISA). This is the first report to detect CPA using an immuno-biosensor iSPR format.

Evaluation of compaction uniformity of the paving layer based on transverse and longitudinal measurements

ABSTRACT Compaction uniformity is essential to the successful performance of asphalt pavement. Therefore, understanding the characteristic and full evaluation on the overall density distribution in field construction is necessary. An available method capable to assess compaction uniformity of the hot paving layer was proposed by considering both longitudinal and transverse density distribution. Field tests of density distribution behind pavers and rollers were conducted on two test sections, respectively. Then, the quantitative evaluation indexes of uniformity (i.e. the range (R), coefficient of variation (CV), repeatability standard deviation in detection track (Sr), etc.) were used to analyse compaction uniformity and the severity of non-uniformity of the asphalt mat. Moreover, the uniformity variation from paving to rolling was evaluated through the tests and a compaction uniformity model. Results indicated that rolling compaction could intensify the degree of non-uniformity of the paving mat, although all the density after rollers is higher than the density behind pavers, and simulation analysis corresponds with the test results. The uniformity of density distribution in transverse is worse than in longitudinal. Tamper seemed to be more effective than other parameters at improving the initial density, while frequency of vibrator appeared to have the most impact on transverse compaction uniformity.

Simultaneous determination some of b group vitamins in nutritional products by liquid chromatography tamdem mass spectrometry following enzymatic hydrolysis

Liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed for the simultaneous qualification of relevant forms of B group vitamins including vitamin B1, B2, B3 and B6 in nutritional products. Samples are hydrolyzed by enzymatic digestion at 37ºC in the shaking water bath within approximately 12 to 14 hours. Papain and α-amylase enzymes were used to hydrolize the protein and complex carbohydrate. Acid phosphatase was used to cut phosphoryl links to form free vitamin forms. The separation was achieved on a C18 column (100mm×2.1mm×1.7μm). Analytes were eluted with the mobile phase of 10 mM ammonium formate and methanol by gradient program at a flow rate of 0.15 mL/min. The calibration curves ranged from 0.2 to 2000 ng/mL with the correlation coefficients > 0.998. Limits of detection and quantification of method ranged from 2.7 to 3.8 μg/100g and 9.1 - 12.6 μg/100g, respectively. The method was validated at three different concentrations with the recovery of 80 - 110%, relative standard deviation of repeatability, RSDr %, of 2.61 - 4.69%, and intermediate reproducibility, RSDR% of 3.40 - 9.69%. The method was applied to simultaneously determine the four water soluble vitamins in several of nutritional products.  

Determination of hafnium in zirconium materials

An arc atomic emission technique of hafnium determination in zirconium is developed and tested. The study was carried out on a PGS-2 spectrometer equipped with MAÉS analyzer and information processing software «Atom 3.3». («VMK-Optoélektronika», Novosibirsk). Excitation of spectra of pre-oxidized metal was carried out using a medium-frequency generator «Vesuvius» («VMK-Optoélektronika», Novosibirsk). Analytical line of hafnium was free of spectral overlap with the lines of zirconium. We have set a current of the AC arc discharge (20 A), exposure time (30 sec) and the form of the electrode into which the sample is placed («narrow crater») are selected. The effect of buffering additives (graphite powder, bismuth fluoride) on the intensity of the analyte lines was studied. It is shown that high sensitivity of the analyte is observed for oxidized material without additives. Reduction of the random error attributed to the influence of conditions of spectrum excitation and sample preparation is achieved using the intensity ratio of the analyte line and zirconium as an analytical signal. Recommendations regarding preparation of the samples for calibration are given. The lower limit of the determined concentration is 0.01% with a relative standard deviation in repeatability 3%.

C and H stable isotope ratio analysis using solid-phase microextraction and gas chromatography-isotope ratio mass spectrometry for vanillin authentication

It is possible to distinguish precious vanillin from Vanilla species (planifolia or tahitensis) from much less expensive synthetic and nature-identical vanillin on the basis of the stable isotope ratios of H and C (2H/1H, 13C/12C). Analysis is usually performed using GC-IRMS (Gas Chromatography - Isotope Ratio Mass Spectrometry) after solvent extraction of vanillin from the sample. Recently, head-space solid-phase microextraction (HS-SPME) has been proposed as an alternative for determining 13C/12C.The aim of this study was to develop a method to analyse 2H/1H in vanillin using SPME-GC-IRMS for the first time, by testing different operating conditions and comparing the results with those obtained after solvent extraction. The ultimate scope was to develop a quick, robust and effective method to measure 2H/1H and 13C/12C in vanillin to assess the authenticity of labelling.Almost 50 authentic samples from vanilla pods, nature-identical (ex) and synthetic vanillin and 4 commercial food products were taken into account. All the samples were subjected to HS-SPME-GC-IRMS analysis and most of them to GC-IRMS analysis after solvent extraction of vanillin.The SPME method developed for 2H/1H analysis guarantees the absence of isotopic fractionation, repeatability and reproducibility standard deviation of below 7‰ and savings in terms of time (from 30 to 5 min) and solvent.HS-SPME GC-IRMS analysis of δ2H and δ13C can be proposed as a rapid and robust method to discriminate different types of vanillin and assess the authenticity of natural vanillin, also contained in food matrices.

EVALUATION OF THE METROLOGICAL PARAMETERS OF METHODS FOR QUANTITATIVE DETERMINATION OF ACTIVE MICROBIAL STRAINS OF GENERA PSEUDOMONAS AND BACILLUS IN THE AIR OF BIOTECHNOLOGICAL PRODUCTION ZONE

Provision of safety and sanitary-hygienic control of biotechnological processes poses a special medical-biological challenge requiring elaboration and metrological assessment of quantitative methods, which determine concentrations of microorganisms-producers in air of manufacturing zone in compliance with the criteria of the International Organization for Standardization. The results of experimental modeling of microbial sprays comprising bacteria of genera Bacillus and Pseudomonas in air of the production zone as the risk factor affecting health of bioindustry employees have enabled to calculate metrological parameters of methods to control microorganisms-constituents of monocomponent and bicomponent biological preparations. Such metrological parameters (standard deviation of repeatability, standard deviation of intermediate precision, expanded uncertainty) match the requirements set to the measurement methods at the accepted confidential probability level p=95 % and ensure proper control of biotechnological processes.

Determination of Aflatoxins and Ochratoxin A in Traditional Turkish Cereal-Based Fermented Food by Multi-Affinity Column Cleanup and LC Fluorescence Detection: Single-Laboratory Validation.

Background: Tarhana is a traditional fermented, sun-dried Turkish food containing yogurtand cereals. There are several potential sources of mycotoxins in tarhana, such as contamination of ingredients or formation during preparation, when water activity is suitable for fungal growth and may lead to mycotoxin production during fermentation or subsequent sun-drying. Objective: To optimize an immunoaffinity column method and carry out single-laboratory validation for the determination of aflatoxins B1, B₂, G1, and G₂ together with ochratoxin A (OTA) in tarhana. Method: A homogenized sample was extracted with methanol-acetonitrile-water (25 + 25 + 50) using a high-speed blender. The sample extract was filtered, diluted with phosphate buffered saline (PBS) solution, and applied to a multi-immunoaffinity column (AFLAOCHRA PREP®). Aflatoxins and OTA were removed with neat methanol and then directly analyzed by reverse-phase LC with fluorescence detection using post-column bromination (Kobra® Cell). Results: Test portions of blank tarhana were spiked with a mixture of total aflatoxins and OTA to give levels ranging from 2.5 to 10.0 and 1.5 to 6.0 μg/kg, respectively. Recoveries for total aflatoxins and OTA ranged from 82 to 93 and 78 to 94%, respectively, for spiked samples. Based on results for spiked tarhana (30 replicates, each at three levels), the relative standard deviation for repeatability ranged from 1.4 to 7.2 and 3.6 to 7.7% for total aflatoxins and OTA, respectively. Conclusions: The performance characteristics for recovery, repeatability, and sensitivity have demonstrated that the method meets method performance criteria for use for official purposes. The method was demonstrated as being applicable to naturally contaminated samples of tarhana of varied composition obtained from local markets in Turkey. Highlights: This is the first immunoaffinity column method for simultaneous analysis of aflatoxins and OTA in traditional Turkish food (tarhana). Suitability was demonstrated by single-laboratory validation for official purposes in Turkey. The method was demonstrated as suitable for naturally contaminated samples of tarhana of varied composition.

Identification and quantification of cereulide in cow’s milk using liquid chromatography-tandem mass spectrometry

ABSTRACTIn this study, the presence of cereulide in cow’s milk was identified and quantified using our validated method with liquid chromatography-tandem mass spectrometry. Cereulide was concentrated using protein acid-precipitation and extracted from the precipitate by using acetonitrile twice. The combination of protein acid-precipitation and extraction sufficiently eliminated the matrix compounds from the milk and a further clean-up step utilising solid-phase extraction could be omitted. For robustly measuring the samples and keeping the MS devices clean, the extraction solution was diluted 10-fold using methanol. Owing to the minimisation of the interferences caused by fragmentation patterns, multiple reaction monitoring information-dependent acquisition-enhanced product ion spectra enabled the characterisation and identification of cereulide. Besides the matrix effect (−4%), an external solvent calibration curve was adapted for accurate quantification. The method was validated using fortified recovery tests, at two concentrations (10 and 50 µg kg−1), using three samples daily on five different days based on the Japanese guidelines. This new method exhibited good accuracy ranging from 91% to 94%. The relative standard deviations of repeatability ranged from 2% to 5%, and the relative standard deviation of within-laboratory reproducibility ranged from 5% to 6%. These standard deviations satisfied the criteria for the Japanese validation guidelines. The limit of quantification (LOQ) was estimated to be 2 μg kg−1. On the product ion spectra at the LOQ level, the library match was satisfactory with a purity fit value of >70%. The method was applied to 14 raw milk and three milk samples pasteurised using the low-temperature, long-time process and collected in Tokyo. None of the samples was found to contain the target toxin.

Simultaneous determination of nine acaricides and two metabolites in comb honey by LC/MS/MS

ABSTRACTWe developed a method for the simultaneous determination of acaricides in comb honey using LC/MS/MS. Because methods for honey analysis had not previously been applied to comb honey, we modified three techniques for sample preparation and LC/MS/MS conditions. First, we used a modified QuEChERS method that changed the extraction solution from ethyl acetate to acetonitrile. Second, we replaced the InertSep® MA-1 (30 mg, 1 ml) clean-up cartridge with an Oasis® HLB (60 mg, 3 ml). Third, we changed the ionisation mode from ESI to atmospheric pressure chemical ionisation (APCI). With these modifications, sample matrices had no effect on the identification and quantification of analytes, using an external solvent calibration curve. We verified this new method with nine acaricides and two metabolites on comb honey and honey samples from three different honey origins. The trueness ranged from 74.0 to 99.4%. The relative standard deviation of repeatability (RSDr) ranged from 0.8 to 14.8% and that of within-laboratory reproducibility (RSDWR) ranged from 1.3 to 14.8%. All criteria met Japanese validation guidelines. The LOQ was 1.0 μg kg–1 for all analytes. We applied this method to 10 comb honey and 31 honey samples commercially available in Tokyo. From the results of the analysis of 41 samples, we observed that amitraz remained as N-(2,4-dimethylphenyl)-N-methylformamidine (DMPF) in 9 comb honey and 23 honey samples and that their residual concentrations were less than 20 μg kg–1. Using this new method, we improved recovery and precision, which enabled precise quantitative determination. Furthermore, the residual amitraz value in honey determined by both this new and the previous method were in good agreement.

Total Folate in Infant Formula and Adult Nutritionals by Trienzyme Extraction and LC-MS/MS Quantitation: A Multilaboratory Testing Study, Final Action 2011.06

Background: The need for an updated reference method for folate was identified as a priority by the AOAC's Stakeholder Panel on Infant Formula and Adult Nutritionals (SPIFAN) in 2011. An Expert Review Panel (ERP) found AOAC Official MethodSM 2011.06 suitable for the purpose and approved it as a First Action Official Method. Objective: To determine the repeatability and reproducibility of Method 2011.06: Total Folate in Infant Formula and Adult Nutritionals by Trienzyme Extraction and LC-MS/MS Quantitation. Methods: A multilaboratory collaborative study was conducted. Eleven laboratories located in five countries participated and completed analysis of all multilaboratory testing (MLT) samples. The study was divided into two parts. In the first part, the laboratories analyzed two practice samples (blindly coded) using the updated folate Method 2011.06. The laboratories providing results within the expected range qualified for part two, in which they analyzed 11 MLT samples in blind duplicates. Results: The results were compared with the Standard Method Performance Requirements (SMPR 2011.006) established for folate. The precision results met the requirements stated in the SMPR for all of the samples. Repeatability and reproducibility relative standard deviations ranged from 3.5 to 6.6 and from 9.0 to 15.7%, respectively. Horwitz ratio values for all of the samples were well below 2 (0.61-1.06). Conclusions: The ERP determined that the method performance met the SMPR requirements in September 2017 after reviewing the presented MLT data. Highlights: The ERP recommended the method for Final Action status.

Shape Analysis of the Patellar Bone Surface and Cutting Plane for Knee Replacement Surgery.

Geometry of the patella (kneecap) remains poorly understood yet is highly relevant to performing the correct patellar cut to reduce pain and to improve function and satisfaction after knee replacement surgery. Although studies routinely refer to “parallel to the anterior surface” and “the patellar horizon,” a quantitative definition of these is lacking and significant variability exists between observers for this irregularly-shaped bone. A 2D-3D shape analysis technique was developed to determine the optimal device configuration for contacting the patellar surface. Axial and sagittal pseudo-X-rays were created from 18 computed tomography (CT) scans of cadaveric knees. Four expert surgeons reviewed three repetitions of the X-rays in randomized order, marking their desired cut plane and their estimate of the anterior surface. These 2D results were related back to the 3D model to create the desired plane. There was considerable variability in perceptions, with intra- and intersurgeon repeatability (standard deviations) ranging from 1.3° to 2.4°. The best configuration of contact points to achieve the desired cutting plane was three pegs centred on the patellar surface, two superior and one inferior, forming a 16 mm equilateral triangle. This configuration achieved predicted cut planes within 1° of the surgeon ranges on all 18 patellae. Implementing this, as was done in a subsequent prototype surgical device, should help improve the success and satisfaction of knee replacement surgery.

Repeatability of Contour Method Residual Stress Measurements for a Range of Materials, Processes, and Geometries

Abstract This article examines the precision of the contour method using five residual stress measurement repeatability studies. The test specimens evaluated include the following: an aluminum T-section, a stainless steel plate with a dissimilar metal slot-filled weld, a stainless steel forging, a titanium plate with an electron beam slot-filled weld, and a nickel disk forging. These specimens were selected to encompass a range of typical materials and residual stress distributions. Each repeatability study included contour method measurements on five to ten similar specimens. Following completion of the residual stress measurements, an analysis was performed to determine the repeatability standard deviation of each population. In general, the results of the various repeatability studies are similar. The repeatability standard deviation tends to be relatively small throughout the part interior, and there are localized regions of higher repeatability standard deviations along the part perimeter. The repeatability standard deviations over much of the cross section range from 5 MPa for the aluminum T-section to 25 MPa for the nickel disk forging. There is a strong correlation between the elastic modulus of the material and the repeatability standard deviation. These results demonstrate the precision of the contour method over a broad range of specimen geometries, materials, and stress states.

Validation and Optimization of a Method for Sb Determination from Bottled Natural Mineral Waters by ICP-OES

In the present work, it was developed a simple, cheap and quick method for Sb determination from mineral water, using ICP-OES, using two different calibration proceedings: calibration curve method (CCM) and standard additions method (SAM). On the studied concentration range, the parameters such as the calibration curve slope, linearity expressed through correlation coefficient r = 0.9992, limits of detection LoD = 0.67 �g L-1 and quantification LoQ = 2.01 �g L-1, the standard deviation of repeatability of 0.25 �g L-1, the accuracy of 0.16 �g L-1 satisfy the performance criteria. The value of extended uncertainty with a confidence level of 95 % (k = 2), is 1.0 �g L-1 obtained for Sb content of 4.10 �g L-1. The mineral waters were analyzed also by the addition standard method. One of the advantages of this method is to eliminate interference from the matrix. By the method of standard additions, the detection limit decreased from LoD=0.67 �g L-1 to 0.16 �gL-1.

The Validation of the Dai Nippon Medi·Ca SA Method for AOAC Research Institute Performance Tested MethodsSM Certification.

A ready-made dry medium method for Staphylococcus aureus count, the Medi·Ca SA method incubated at 35 or 37°C, was compared with the Baird-Parker method (AOAC Official MethodSM 975.55) for 11 food matrices: raw beef, raw ground beef, raw lamb, cooked ham, raw salmon, frozen prawn, fresh chilled pasta, pasteurized milk, natural cheese, cream puff, and potato salad. The mean difference between the two methods at each contamination level for each matrix was <0.5 log10, and the 95% confidence intervals on the mean differences fell within the range of -0.50 to 0.50. Standard deviation of repeatability and RSDr values of the Medi·Ca SA method were generally the same level as those of the Baird-Parker method, and r2 ranged from 0.98 to 1.00. Product consistency and stability studies showed little variability between productions lots and a shelf-life of 16 months. Incubation time within the range of 22-26h and variations to the sample volume did not adversely affect the results. These results showed that the Medi·Ca SA method is a reasonable alternative to the reference method for selected food matrices and makes it possible to simultaneously detect and enumerate S. aureus in only 24h.