Repeatability Relative Standard Deviation Research Articles

Validation of the Test Method-Determination of Available Carbohydrates in Cereal and Cereal Products, Dairy Products, Vegetables, Fruit, and Related Food Products and Animal Feeds: Collaborative Study, Final Action 2020.07.

A simple, accurate, and reliable method to measure available carbohydrate components of food products, including cereal and dairy products, fruits, vegetables, processed food, food ingredients, and animal foods, was developed by Megazyme (product K-AVCHO, Bray, Ireland). A single-laboratory validation of the enzymatic method resulted in First Action status as Official Method of AnalysisSM2020.07. A collaborative study was conducted to evaluate the repeatability and reproducibility of Official Method 2020.07 for the measurement of available carbohydrates, including digestible starch, lactose, sucrose, isomaltose, maltose, glucose, fructose, and galactose in a broad range of food and feed products. Samples are defatted if containing >10% fat content, and incubated with pancreatic α-amylase and amyloglucosidase under conditions that simulate those in the small intestine (pH 6, 37°C, 4 h). The reaction solution is clarified and diluted, and an aliquot is incubated with sucrase, maltase, oligo-1,6-α-glucosidase, and β-galactosidase to hydrolyze sucrose, maltose, isomaltose, and lactose to glucose, fructose, and galactose, which are then measured enzymatically. The multi-laboratory validation (MLV) matrixes included cereal, animal feeds, fruit, vegetables, infant formula, powdered milk drink, a dessert product, and mushrooms. Additional materials were analyzed by collaborators as "practice samples." All MLV matrixes resulted in repeatability relative standard deviations (RSDr) <3.91% and reproducibility relative standard deviations (RSDR) ranging from 3.51 to 11.58% with 9 of the 10 matrixes having RSDR of <6.19%. For the practice samples, the RSDR ranged from 2.7 to 11.4% with 7 of the 8 samples having RSDR of <4.4%. Official Method 2020.07 meets the AOAC requirements for repeatability and reproducibility, and the data support Final Action status. Official Method 2020.07 is a robust, simple to use, and reproducible method for the analysis of available carbohydrates in a wide range of matrixes.

Research and application of direct mercury analyzer (DMA-80) quickly determination of total mercury contents in dietary supplements

The Direct Mercury Analyzer (DMA-80) was studied and investigated to quickly and&amp;nbsp;accurately determine the total mercury content in health supplements. The method shows&amp;nbsp;high specificity, and the calibration curve has a good correlation coefficient with R2 greater&amp;nbsp;than 0.995; the limit of detection (LOD) and limit of quantification (LOQ) were 1.88 &amp;micro;g/kg&amp;nbsp;and 6.26 &amp;micro;g/kg, respectively; The relative repeatability standard deviation (RSRr) was in the&amp;nbsp;range of 2.46 - 7.34% and the recovery (R) was in the range of 85.7 - 100%. The method&amp;nbsp;was applied to evaluate the mercury content in 39 health supplement samples taken in Hanoi&amp;nbsp;city. The initial research results indicated preliminary&amp;nbsp;mercury&amp;nbsp;contamination in 13 health&amp;nbsp;supplement products on the market in the range of 5.41 - 450 &amp;micro;g/kg. &amp;nbsp;

Development and validation of a multi-residue method for determination of antimicrobial sulfonamides, macrolides and quinolones in Iranian feta cheese by SPE clean-up and LC-MS/MS

A selective and sensitive multi-residue/multi-class ultra-performance liquid chromatography–tandem mass spectrometry method has been validated for simultaneous analysis of 25 antibiotic residues belong to sulfonamides, macrolides, and quinolones groups, as well as griseofulvin and trimethoprim, in Iranian feta cheese samples. Two specific precursor – product ion transitions were acquired per target compound by a positive electrospray ionisation in multiple reaction monitoring mode. Results were obtained as follows: limit of detection (LOD) and limit of quantification (LOQ) were respectively 3.3 ng g−1 and 10 ng g−1 (except for josamycin, LOD: 8.33 and LOQ: 25 ng g−1). Average recovery ranged between 70% and 120% and relative standard deviation of repeatability was lower than 20%. Finally, the method was applied to determination of target analytes in feta cheese samples obtained from the local hypermarkets and traditional dairy product markets in Tehran, Iran.

A Portable Optical Fiber Tip Facet LSPR Aptasensor for Detection of Fumonisin B1

Fumonisin B1 (FB1) is a mycotoxin that mainly contaminates food crops. To avoid the harmful effect of FB1 on the human body, it is necessary to establish a convenient, sensitive, and accurate FB1 detection method. In this study, an optical fiber tip facet biosensor based on the localized surface plasmon resonance (LSPR) that adapts to a general detection platform was developed. An optical fiber end face was assembled with –NH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , Au nanoparticles (AuNPs), and aptamer, and the fabricating parameters were optimized. The results showed that the optical fiber LSPR biosensor had a good linear relationship ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}^{\text {2}}$ </tex-math></inline-formula> = 0.9817) between the logarithmic FB1 concentration and the LSPR peak shifts within the linear range of concentrations of 0.8–200.0 ng/mL and a low limit of detection (LOD) of 0.17 ng/mL, as well as selectivity, recovery rates (96.08%–112.23%), and repeatability relative standard deviation (RSD) of 3.37%. It was validated by corn. Therefore, it was feasible that a tip facet optical fiber LSPR biosensor could be used to detect FB1, with advantages of convenience, renewability, and low cost. It is easy to popularize and apply.

Preformulation and UV-Spectrophotometric Analytical Method Validation Studies for Assessment of Canagliflozin

&gt;The objectives of the present investigation were the physicochemical examination of canagliflozin to authenticate the drug’s characteristics and validation of straightforward and rapid ultraviolet-spectroscopy technique for evaluation of canagliflozin in phosphate buffer, pH 6.8. X-ray diffraction study revealed numerous peaks i.e. 11.41, 16.35, 16.5, 16.65, 18.53, 18.58, 19.55, 20.11, 20.46, 20.71, 21.62, 23.96, 24.17, 24.77, 26.5, 27.08, 27.68, 28.22, 28.73 and 32.6 at °2θ which demonstrated extremely crystalline character of drug. The regression equation for the standard plot was Y = 0.01957X + 0.036, and correlation coefficient was 0.9936. The method was found linear as indicated by correlation coefficient values of 0.9933, 0.9938, and 0.9943 for three consecutive standard plots. The average recovery of Canagliflozin was found to be 100.033% which was inside the prerequisite specification of the range 98 to 102%. The percentage relative standard deviation for repeatability, inter-day precision, intermediate precision, and robustness was less than 2%. The limit of detection (LoD) for Canagliflozin was 2.38 μg/mL, and the limit of quantitation was 7.24 μg/mL, which established the sensitivity of the UV-spectroscopy analytical method. In conclusion, the validation parameters like linearity, accuracy, repeatability, inter-day precision, intermediate precision, robustness, and sensitivity were found acceptable for the UV-spectroscopy analytical technique for analysis of Canagliflozin.

Quality by design assisted high‐performance liquid chromatography parameters for simultaneous estimation of simvastatin and fenofibrate

AbstractIn a present study quality by design was used to develop a reliable high‐performance liquid chromatography method for simultaneous estimation of simvastatin and fenofibrate. A robust chromatographic setting for quality peaks and appropriate component separation within a reasonable run duration was generated. Furthermore, to determine critical quality attributes (CQA), a quantitative relationship between critical material attributes and CQA was established using Box‐Behnken design to produce analytical design space and develop a control approach. The mathematical models used three independent characteristics, acetonitrile volume, buffer molarity, and flow rate. The optimum and expected conditions were acetonitrile and potassium dihydrogen orthophosphate buffer (pH 2.9 adjusted, with orthophosphoric acid) (80.65:19.35 v/v) as an optimized mobile phase at a flow rate of 0.99 ml/min. We achieved adequate baseline separation of both drugs in just 10 min with these optimum parameters. The amount of acetonitrile was revealed to be the most important factor determining the perturbation plot responses. The %recoveries for both medicines were 99.15%–101.86% at all three levels. Both drugs showed relative standard deviations for repeatability, and intermediate precision were less than 2%. As a result, a simple, accurate, and repeatable high‐performance liquid chromatography approach for routine quality control testing was developed.

Determination of Insoluble, Soluble, and Total Dietary Fiber in Foods Using a Rapid Integrated Procedure of Enzymatic-Gravimetric-Liquid Chromatography: First Action 2022.01.

A simple, accurate, and reliable method for the measurement of total dietary fiber (TDF) according to the Codex definition (2009) was developed and successfully validated as AOAC Official Method of Analysis (OMA) 2017.16. Subsequently, OMA 2017.16 was modified to allow separate measurement of soluble dietary fiber (SDF) and insoluble dietary fiber (IDF) fractions. To perform a collaborative study to evaluate the repeatability and reproducibility of OMA 2017.16 modification for the measurement of total dietary fiber (TDF) as IDF and SDF measured as (1) water SDF that precipitates in 78% aqueous ethanol (SDFP), and (2) water SDF that remains soluble in 78% aqueous ethanol (SDFS) of degree of polymerization ≥3. Duplicate test portions are incubated with pancreatic α-amylase (PAA), amyloglucosidase (AMG), and protease under the conditions employed in OMA 2017.16. For the measurement of IDF, the digestate is filtered and the IDF determined gravimetrically. SDFP in the IDF filtrate is precipitated with alcohol and captured by filtration and determined. SDFS in the SDFP filtrate is recovered and quantitated by LC. The matrixes included cereal products and flours, vegetables, health food snacks, soup, chocolate, and beans. Additional materials were analyzed by collaborators as "practice samples". With the diethylene glycol internal standard, all multi-laboratotu (MLV) matrixes resulted in repeatability relative standard deviations (RSDr) for TDF analyses of <3.60% and RSDR ranging from 4.55 to 9.26%. For the practice samples, the RSDR for TDF ranged from 6.69 to 11.68%. OMA 2022.01 meets the AOAC requirements for repeatability and reproducibility and the data support First Action status. OMA 2022.01 is a robust and reproducible method for the analysis of insoluble, soluble (SDFP and SDFS), and TDF in a wide range of matrixes.

An improved surface enhanced Raman spectroscopic method using a paper-based grape skin-gold nanoparticles/graphene oxide substrate for detection of rhodamine 6G in water and food.

Organic toxins are persistent chemicals of global concern capable of accumulating in environment and food. Surface enhanced Raman spectroscopy (SERS) is a promising technique that facilitates onsite detection of organic toxins. However, the fabrication of a SERS substrate is complicated and difficult to provide flexibility, fastness and cost-effectiveness. This study aims to develop a paper-based SERS method using grape skin-gold nanoparticles/graphene oxide (GE-AuNPs/GO) as SERS substrate and evaluate its efficiency with rhodamine 6G (Rh6G) as a model organic toxin and a real water and food contaminant. GE-AuNPs synthesized by green method using grape skin waste extract and GE-AuNPs/GO showed a surface plasmon resonance at 536 and 539nm, particle size 18.6 and 19.5nm, and zeta potential -44.6 and -59.7mV, respectively. Paper-based SERS substrates were prepared by coating a hydrophobic thin-film of 30% polydimethylsiloxane solution in hexane on Whatman no. 1 filter paper, followed by drop-casting GE-AuNPs or GE-AuNPs/GO and drying. The SERS signals of Rh6G showed an enhancement factor of 5.8×104 for GE-AuNPs and 1.92×109 for GE-AuNPs/GO, implying that a combination of electromagnetic surface plasmon, charge transfer and molecular resonances may be responsible for a higher enhancement of signal by the latter. A low detection limit of 7.33×10-11M in the linear range of 10-11-10-5M was obtained for GE-AuNPs/GO, while the relative standard deviation of repeatability and reproducibility was 9.6 and 12.6%, respectively. Paper-based GE-AuNPs/GO SERS substrate was highly stable as <20% loss in efficiency was shown over a 60-day storage period. Application to real samples showed a high recovery of Rh6G from tap water (93.9-100.8%) as well as food samples such as red chilli powder (91.0-95.4%), red glutinous rice ball (96.6-98.3%) and tomato ketchup (98.9-102.3%) after QuEChERS extraction. Collectively, the developed paper-based GE-AuNPs/GO can be a potential substrate for sensitive onsite detection of rhodamine 6G by SERS method.

Assessment and Quantification of Homovanillic Acid and Vanillylmandelic Acid in Rodent Urine Samples Using a Validated High-Performance Liquid Chromatography-Ultraviolet Method

Objective: The purpose of this study was to establish a validated analytical method for estimating the biogenic amine metabolites vanillylmandelic acid (VMA) and homovanillic acid (HVA) simultaneously using the high-performance liquid chromatography-ultraviolet (HPLC-UV) method. Materials and Methods For the analysis of VMA and HVA in artificial urine samples, an HPLC method was devised and validated. The chromatographic separation was achieved on Kromasil C8, 5 μm (125 mm × 4.6 mm) column at an ambient temperature of 25°C, with mobile phase combination of acetonitrile: 0.1% orthophosphoric acid in ratio of 30:70 v/v at a flow rate 0.5 mL/min using Agilent HPLC system. For the separation of these two metabolites, different mobile phases were used on a trial and error basis. In terms of linearity, accuracy, repeatability, precision, and robustness, the developed technique was validated according to ICH guidelines. Results A high-resolution HPLC method was devised for the separation of VMA and HVA. VMA and HVA were found to be linear over the concentration range of 10 to 35 μg/mL, with coefficients of determination (r 2) of 0.955 and 0.963 for both metabolites, respectively. VMA and HVA had detection limits of 1.7 and 1.8 μg/mL, respectively, and quantification limits of 5.2 and 5.3 μg/mL. The results showed a low value of % relative standard deviation for repeatability, intra- and inter-day precision, and robustness studies. Conclusion A validated HPLC-UV method was developed for estimating VMA and HVA in urine samples.

Chiral separation of new chiral insecticide pyraquinil isomers and establishment of analytical methods in vegetables

以全新手性杀虫剂唑虫酯为研究对象,通过筛选手性色谱柱和优化流动相比例,建立了唑虫酯及其氧化代谢物异构体的拆分方法,在此基础上开发利用高效液相色谱-串联质谱(HPLC-MS/MS)同时测定小白菜和蕹菜中唑虫酯及其氧化产物手性异构体的分析方法。以纤维素-三(3,5-二氯苯基氨基甲酸酯)共价键合手性柱(Chiral INC)(250 mm×4.6 mm, 5 μm)为分析柱,乙腈和2 mmol/L甲酸铵水溶液作为流动相进行梯度洗脱分离,在多反应监测负离子模式下进行检测,唑虫酯4个异构体分离度分别为1.63、2.83和1.74,唑虫酯氧化产物异构体分离度为5.82。通过衍生化的方法进一步确定出峰顺序为RS-唑虫酯、SS-唑虫酯、RR-唑虫酯、SR-唑虫酯、S-唑虫酯氧化产物和R-唑虫酯氧化产物。唑虫酯和其氧化产物的手性异构体分别在1.25~1250 μg/L和2.5~2500 μg/L范围内具有良好的线性关系,相关系数(R2)大于0.99。在蕹菜和小白菜样品中同时添加唑虫酯和唑虫酯氧化产物消旋体进行添加回收试验,添加水平为1、20、400 μg/kg(即唑虫酯异构体为0.25、5、100 μg/kg;唑虫酯氧化代谢产物异构体为0.5、10、200 μg/kg),回收率为72.6%~110.6%,相对标准偏差(RSD)均在9.4%以下,其中日内重复性的RSD在0.5%~9.4%之间;日间重复性的RSD在1.0%~8.6%之间,表明该方法具有良好的回收率和精密度。该研究可为唑虫酯这一新型手性农药的环境行为研究及后续质量控制、药效评价等提供相应的分析技术,为新农药开发应用提供有力的技术支撑。

Lactose Concentration in Low-Lactose and Lactose-Free Milk, Milk Products, and Products Containing Dairy Ingredients by High Sensitivity Enzymatic Method (K-LOLAC), Collaborative Study: Final Action 2020.08.

The AOAC Stakeholder Panel on Strategic Food Analytical Methods issued a call for methods in 2018 for the measurement of lactose in low-lactose and lactose-free products under Standard Method Performance Requirement (SMPR®) 2018.009. Megazyme's Lactose Assay Kit (K-LOLAC) was reviewed and accepted as a First Action Official MethodSM in 2020 (2020.08). A collaborative study was conducted to evaluate the to evaluate the reproducibility of AOAC Official MethodSM2020.08 for the measurement of lactose concentration in low-lactose and lactose-free milk, milk products, and products containing dairy ingredients. Samples are deproteinated and clarified by treatment with Carrez reagents, and then free glucose is removed using a glucose oxidase and catalase treatment system. Quantification of lactose is based on the hydrolytic activity of β-galactosidase, which hydrolyses lactose to glucose and galactose. Any remaining free D-glucose is first measured using a hexokinase (HK)/glucose 6-phosphate dehydrogenase (G-6PDH)/6-phosphogluconate dehydrogenase (6-PGDH) based assay procedure, and then β-galactosidase is added to hydrolyze the lactose in the same reaction vessel with concurrent measurement of the released D-glucose. The samples analyzed included a number of lactose-free and low-lactose milk samples, lactose-free infant formula, lactose-free milkshake, lactose-free adult nutritional drink, lactose-free cream, and lactose-free cheese. All materials had repeatability relative standard deviations (RSDr) <7%. The reproducibility relative standard deviation (RSDR) varied from 3.8 to 14.9% with seven of the 10 test samples having an RSDR of <10%. The Lactose Assay Kit (K-LOLAC) meets the requirements for reproducibility set out under SMPR 2018.009. The Lactose Assay (K-LOLAC) is a robust, simple, and reproducible method for analysis of lactose in foodstuffs and beverages.

Single and multi-laboratory validation of a droplet digital PCR method

The authorisation of genetically modified food and feed in the EU is subject to the provision of evidence of safety and of the availability of reliable analytical methods. These methods represent an essential tool for official laboratories to enforce a harmonised market control.Here the validation of droplet digital PCR (dPCR) methods has been performed for studying if the performance and acceptance parameters set by EU and other international guidelines for the analysis of genetically modified organisms (GMO) in food and feed are suitable and achievable also with such methods. The single-laboratory validation study showed that performance requirements set for GMO analysis by real time PCR can also be used to assess dPCR-based methods. Moreover, trueness and precision were assessed for both simplex and duplex formats in a multi-laboratory validation study organised according to international standards. Overall, the data on trueness, repeatability and reproducibility precision resulting from the collaborative study are satisfying the acceptance criteria for the respective parameters as stipulated in the EU and other international guidance such as the Codex Committee on Methods of Analysis and Sampling (CCMAS). For instance, the duplex droplet dPCR method for MON810 showed relative repeatability standard deviations from 1.8% to 15.7%, while the relative reproducibility standard deviation was found to be between 2.1% and 16.5% over the dynamic range studied. Moreover, the relative bias of the dPCR methods was well below 25% across the entire dynamic range.In addition, other aspects supporting the application of digital PCR for the control of GMOs on the market were experimentally assessed such as the conversion of the measurement results from copy number ratio to mass fraction, the influence of the DNA extraction step and of the ingredient content. It was found that the DNA extraction step added only a limited contribution to the variability of the measurement results under the studied conditions. The decreasing amount of the target ingredient content may decrease the level of precision of the method, although within the acceptance range of GMO performance parameters.

An integration of UPLC-Q-TOF/MS and chemometrics analysis for the holistic quality evaluation of different geographical Paederia scandens.

Due to the special geographical location and climate of China, there are large differences in the chemical composition and content of Paederia scandens (PS) from different origins, which will have a large impact on its efficacy. An efficient quality control method for PS was established by combining ultra-high-performance liquid chromatography (UPLC) and electrospray ionization mass spectrometry analyses. First, a UPLC-quadrupole time-of-flight mass spectrometry system was employed to identify the chemical composition of PS from seven different origins. Then, the chemical variation in 73 batches of PS samples was subsequently investigated by quantitation of four marker compounds. A total of 15 common compounds were identified in the samples of PS from seven origins. And four of the marker compounds were chosen based on VIP values to characterize the differences between PS samples of different origins. The linearity ranged between 0.005 and 2.500 mg/mL; the correlation coefficients (r2 ) ranged from 0.999 to 1; the limits of detection ranged from 0.013 to 0.033 μg/mL; and the relative standard deviations for repeatability, precisions, and stabilities were below 0.2%, 1.6%, and 0.6%, respectively. The results show that the method can be effective and comprehensive in evaluating the quality of PS from different origins. And this comprehensive strategy proved to be a powerful technique used to differentiate between different geographical herbs.

A novel thiolysis-high-performance liquid chromatography method for the determination of proanthocyanidins in grape seeds.

A novel thiolysis-high-performance liquid chromatography method for the quantitative determination of total proanthocyanidins and the mean degree of polymerization in grape seeds has been developed. Following thiolysis with formic acid and benzyl mercaptan, reaction products were separated and purified. Three proanthocyanidin monomers and three derivatives were obtained and their structures were identified by liquid chromatography-mass spectrometry, FTIR spectroscopy, and NMR spectroscopy. A decomposition model of the thiolysis products and a correction formula for proanthocyanidins concentration were established. This thiolysis-high-performance liquid chromatography method displayed good calibration linearity (R2 >0.999 over the concentration range 0.01 to 10mg/mL), excellent accuracy (recoveries of 97.9-99.6%), and precision (repeatability relative standard deviations of 0.45-0.75%). This method is suitable for the quantitative analysis of proanthocyanidins in grape seed products.

Improving consistency at testing cementitious materials in the Dynamic Surface Leaching Test on the basis of the European technical specification CEN/TS 16637–2 – Results of a round robin test

The environmental impact assessment of materials is usually based on laboratory tests, mostly in combination with models describing the longterm fate of the substances of interest in the targeted environmental compartment. Thus, laboratory tests are the fundamental link to achieve appropriate assessment conclusions which makes it essential to generate consistent results. This just as applies to the leaching of cementitious materials. In Europe, the leaching behavior of monolithic building materials is tested in the Dynamic Surface Leaching Test following the specification CEN/TS 16637–2. An interlaboratory comparison on European level regarding this technical specification showed relatively high intra- and interlaboratory variations for the tested materials (monolithic copper slag and cement stabilized coal fly ash). Therefore the German Committee for Structural Concrete (DAfStb) framed a guideline to specify additional testing conditions for cementitious materials. To assess the possible improvement by this guidelines measures, a round robin test with 11 participants from Germany and the Netherlands was conducted. This work aims to provide insight into the factors to be considered in the testing of alkaline materials, including sample preparation, and highlights crucial procedures and their manifestation in the results. All evaluated parameters showed improved results compared to the earlier round robin test. The relative standard deviations for repeatability (RSDr) and reproducibility (RSDR) of the elements calcium, barium, antimony, chromium, molybdenum and vanadium, which are the parameters evaluated in both round robin tests, were RSDr = 4%, 4%, 2%, 5%, 5%, and 5% respectively (4% in average) for this work, in comparison to the European round robin test with an average RSDr of 29% (17%, 17%, 20%, 40%, 36%, and 42%). The RSDR improved from 41% (30%, 36%, 29%, 57%, 40%, and 56%) to 14% (12%, 8%, 6%, 28%, 15%, and 12%). CO2 ingress during testing and the inaccuracy of eluate analytics for concentrations close to the determination limits were identified as the main sources of error.

Reliability in viscosity measurement of thickening agents for dysphagia management: Are results obtained by cone-and-plate rheometers reproducible between laboratories?

Viscosity measurement using a cone-and-plate rheometer is considered to provide an objective and reliable evaluation of thickening agents for dysphagia management. Here, we showed its measurement uncertainty in the context of an inter-laboratory study. Eight test samples (i.e., four viscosity standard liquids, one xanthan gum reagent powder, and three commercial thickening agent powders) were distributed to 10 laboratories in a blinded manner. According to the same standard operating procedure, each laboratory dissolved the xanthan gum or thickening agents at four concentrations (0.5-4.0 g/100 g) and then measured their viscosity (35-803 mPa∙s). As for the viscosity of the standard liquids, the grand means were 98-100% of the certified values, and the relative standard deviations for repeatability (RSDr ) and reproducibility (RSDR ) were ca. 1% and ca. 5%, respectively, suggesting good accuracy in the measurement process. On the other hand, as for the viscosity of the thickening agents, RSDr and RSDR were ca. 2-6% and ca. 5-8%, respectively; however, heterogeneity in the preparation process comprising a manual dissolving step may increase these to near 60%. Furthermore, RSDr and RSDR of estimated additive concentrations to achieve targeted viscosities (50-500 mPa∙s) based on concentration-viscosity curves were ca. 1-3% and ca. 3-5%, respectively, with a few exceptions. These findings suggest that a strictly standardized procedure provides reliable data on the viscosity measurements for thickening agents.

Validation of the CompactDry "Nissui" YMR for Enumeration of Yeasts and Molds in a Variety of Foods: AOAC Performance Tested MethodSM 092002.

The CompactDry "Nissui" YMR is a ready-to-use dry media sheet using a chromogenic medium with selective agents for the detection and enumeration of yeasts and molds in products after incubation at 25 ± 1°C for 3 days. The CompactDry "Nissui" YMR method was validated in order to achieve AOAC Performance Tested MethodsSM certification. The performance of the CompactDry "Nissui" YMR was compared to that of ISO 21527-1:2008 for 10 matrixes including cooked prawns, deli vegetable salad, tuna pâté, fermented yogurt drink, spinach and ricotta quiche, egg custard tarts, fruit and vegetable smoothie, cream cheese, egg salad sandwich, and deli pasta salad. Performance indicators included repeatability, difference of means (DOM), and inclusivity/exclusivity. After log10 transformation of the data, the relative standard deviation of repeatability (RSDr) was <10% for all 30 materials (10 matrixes each at 3 levels) analyzed by the CompactDry "Nissui" YMR method and for 29 of the 30 matrix/level combinations analyzed by the reference method. The DOM ranged from -0.284 (-0.310, -0.257) log10 CFU/g to 0.307 (-0.013, 0.627) log10 CFU/g. Method equivalence was demonstrated in 29 of the 30 matrix/level combinations based on the 90% confidence interval of the DOM being within (-0.5, 0.5). All 51 inclusivity strains showed expected or atypical results, and all 32 exclusivity organisms showed no growth on the medium. The method was shown to be robust to changes in sample volume, incubation temperature, and incubation time, and data are presented supporting product consistency and a 24-month shelf life. The CompactDry "Nissui" YMR method is validated for the determination of yeasts and molds in a variety of matrixes. The CompactDry "Nissui" YMR method is equivalent to the ISO 21527-1:2008 reference method and is suitable for Performance Tested MethodsSM certification for the matrixes tested.

Data accuracy and method validation of chemical soil properties in long-term experiments: Standard operating procedures for a non-certified soil laboratory in Latin America

Long-term agricultural experiments (LTE) are essential to detect cumulative treatment effects on soil properties and to design sustainable production systems. However, to ensure high quality of long-term soil data and their correct interpretation, several analytical issues regarding the accuracy and analytical laboratory bias need to be considered. This paper aims to (1) evaluate laboratory precision and trueness of analytical soil data for the evaluation of long-term trends in LTE and to (2) assess the limitations and challenges for non-certified soil laboratories that might compromise the quality of analytical soil data. A data set of internal reference soil materials (IRM) collected over 16 years and interlaboratory data from eleven years were analyzed to verify method precision, trueness, and the subsequent long-term dataset reliability for several soil quality parameters: organic carbon (SOC, determined either by wet or dry combustion), pH (water), extractable phosphorous (either Bray I or citric acid; Bray-P or citric acid-P), and exchangeable potassium (Kexch). Results showed that IRM used by the laboratory were homogenous in terms of physical and chemical composition and appropriate to confirm the precision of long-term soil survey data. The relative standard deviation for repeatability and reproducibility (RSDR) ranged from 1.5% for SOC by wet combustion to 9.5% for citric acid-P. HorRat values (the ratio of the estimated standard deviations of reproducibility and the repeatability found for individual analytical procedures) for all chemical soil properties were within the acceptable ranges of <2.0. Interlaboratory trials for soil pH and SOC showed tolerable standard Z-Scores under 2.0 (Z-Score, calculated from the difference between laboratory results and the assigned value divided by the standard deviation), verifying the trueness of data. The results of this study reinforce the validity of analytical soil data originating from the non-certified laboratory in Uruguay obtaining both precise and true soil quality data over a long period of time for most soil analytes. Nevertheless, the analytical flaws in LTE soil monitoring were revealed and can only be minimized in ongoing and future studies through the inclusion of certified reference material. These recommendations should guide future research activities in LTE studies on analytical data quality management as a requirement for long-term soil monitoring. Finally, the paper proposes a proficiency testing procedure for soil laboratories to achieve and maintain high analytical quality for LTE soil research.

Tissue distribution and changes in dopamine during development and stress responses in Malus germplasm

Dopamine is a catecholamine and an anti-oxidant which functions in responses to stress and it interacts with plant hormones to mediate plant development. At present, there are few studies on the functions of dopamine in apple. This study developed a method for dopamine determination which was used to analyze dopamine in Malus germplasm, in order to clarify the tissue distribution, developmental changes, diurnal variations, and stress responses in apple trees. First, the proposed method was verified. The linear range of quantification was robust from 0.1 to 20 ng mL−1. The instrumental, inter-day precision, and sample repeatability relative standard deviations were 1.024, 5.607, and 7.237%, respectively. The spiked recovery was greater than 100%, indicating the feasibility of the method and its suitability for the rapid analysis of dopamine in Malus. Next, the dopamine content was measured in 322 Malus tissues. The results showed that the dopamine level in Malus was low and the average dopamine content in leaf was higher than in peel and flesh. The dopamine had a skewed distribution that deviated to the right in cultivars and wild accessions. Finally, the tissue specificity, developmental changes, diurnal changes, and responses to stress were analyzed. In cultivar ‘Pinova’ (Malus domestica), the dopamine concentration was the highest in leaf buds and lowest in flesh. The dopamine contents in leaf and flesh decreased with the growth and development of cultivar ‘Liangxiang’ (Malus domestica). The dopamine content of apple leaves was higher after either drought or salinity stress as compared to the control. In this study, a dopamine detection method for apple was established based on HPLC-MS and shown to be a robust approach. This study provides a framework for future research on elucidating the tissue distribution, developmental changes, diurnal variation, and stress responses of dopamine in apple trees.

Phospholipid composition analysis of krill oil through HPLC with ELSD: Development, validation, and comparison with 31P NMR spectroscopy

A method wherein a high-performance liquid chromatography (HPLC) system is combined with an evaporative light scattering detector (ELSD) was developed and validated as an alternative to the official phosphorous-31 nuclear magnetic resonance (31P NMR) technique to analyze phospholipids in krill oil. A quadratic calibration curve with a good correlation coefficient (>0.999) in the 100–1000 μg mL−1 range was obtained for each phospholipid. The limit of detection (2–7.5 μg mL−1) of the designed assay for the phospholipids in krill oil was good, and the accuracy (99.6–101.0 %) was excellent. The relative standard deviations for repeatability (<1%) and intermediate precision (2.3 %–6.9 %) were acceptable. The results of the developed HPLC-ELSD method applied to krill oil samples were in agreement with those of 31P NMR spectroscopy. Moreover, statistical comparison indicated no significant difference between two methods. Thus, the HPLC-ELSD method can be applied for analyzing the phospholipid composition of krill oil.