Test Portions Research Articles

Evaluation of heating times for loss-on-drying at 105 °C for estimation of laboratory dry matter in animal feeds.

Dry matter is a routine test for all animal feeds, facilitating feed comparisons and diet formulation. It is the most frequent test, yet the most challenging with respect to precision and accuracy. Our objective was to evaluate the accuracy, repeatability, and physicochemical impacts of oven-drying times on laboratory dry matter test results in animal feeds obtained by loss on drying at 105 °C. Eighteen primary samples collected from different feed sources were grouped into high- and low-moisture content materials. The tested methods were based on loss on drying: at 105 °C and Karl Fischer titration was adopted as the reference method. Test portions were oven dried at 105 °C for 3, 6, 12, 16, and 24 h, and test results were compared to the reference method. Test portions were also subjected to a color evaluation using a colorimetric technique. The method based on 3 h of drying provided the closest estimates to those obtained by Karl Fischer titration. Extending heating time (i.e., above 3 h) increases the bias, especially for high moisture feeds, which was attributed to a higher occurrence of non-enzymatic reactions. This was corroborated by the color of the residues, which became darker with increased heating time. The repeatability of loss on drying methods was considered adequate, ranging from 0.32 to 0.73%. The loss-on-drying method based on the binomial 105 °C × 3 h minimizes the bias in the water recovery and causes less non-enzymatic browning in the test portions. The loss-on-drying method recommended for laboratory dry matter in animal feeds is drying the test portions at 105 °C for 3 h.

Assessing the feasibility of machine learning-based modelling and prediction of credit fraud outcomes using hyperparameter tuning

Both the actual theft of a credit card and the deletion of private credit card data are considered forms of credit card fraud. For detection, there are numerous machine learning algorithms accessible. So, several algorithms that can be used to categorize transactions as fraudulent or lawful are illustrated in this study. In this experiment, the credit card fraud prediction dataset was utilized. The dataset is extremely skewed, hence undersampling is used rather than oversampling. The dataset is separated into test and training data portions, and feature selection is made. The experiment uses the methods of Logistic Regression, Random Forest, SVM, ADABoost, XGBoost, and LightGBM. Moreover, the SMOTE and Optuna's hyperparameter tweaking ways provide model customization. The findings suggest that specific algorithms may be capable of accurately recognizing credit card fraud.

Development of a QuEChERS method for simultaneous analysis of 3-Monochloropropane-1,2-diol monoesters and Glycidyl esters in edible oils and margarine by LC-APCI-MS/MS

A simple, fast and effective direct method based on HPLC-APCI-QqQ-MS/MS has been developed to simultaneously determine four 3-monochloropropane-1,2-diol monoesters (3-MCPDE) esterified with palmitic, linoleic, stearic, and oleic acid, and two glycidyl esters (GE) with palmitic and oleic acid in margarine and olive oil using a QuEChERS approach. Factors affecting the efficiency of the extraction process were assessed, including type and amount of salt, extraction solvent, test portion amount, and clean-up sorbent. The analytical method was validated according to Food and Drug Administration (FDA) guidelines using matrix-matched calibration with internal standards and showed good results in terms of linearity (r2 > 0.9992), accuracy (80<Recovery<120%), and precision (RSD<15%). The method was successfully applied for the first time to 11 margarine samples for simultaneous analysis of 3-MCPDE and GE.

The inherent variability of some environmental analytical methods hampers the circular economy of materials

This paper is the third part of three papers on sampling by the number of particles, focusing on analytical variability. The objective is to propose a target variability of waste and contaminated soil analyses (extraction and quantification), that can be used for calculation of the size of a representative sample. Data of intra- and inter-laboratory variability are presented. As the variability of the quantification step (after extraction) is limited in waste and soil analyses to about 0.01, the analytical variability stems from three main sources: (i) non-homogeneous test portions; (ii) for partial extraction methods, variable extraction rate, due to presence of options in the method or insufficient time for equilibrium (leaching or percolation test, biotests); and (iii) ill-defined solid/liquid separation (leaching or percolation tests), critical since there are colloids and nanoparticles in the leachates, representing from 0 to 100% of the element fraction in the leachate. Counter-intuitively, the centrifugation (annex E of EN 12457) series before the 450 nm-filtration delivers leachates more concentrated in particles (median size 150 nm, 1 sample) and statistically more concentrated in elements (+13%, 27 samples, 287 paired data). Without centrifugation, the filter cake that builds up on the membrane is an additional filter. A target intra-laboratory variability of CVr = 0.10 (10%) and inter-laboratory variability of CVR = 0.20 (20%) is proposed for all analytical methods. The methods with higher CVr and CVR should be revisited to not jeopardise the sampling and characterisation efforts of waste and soil, particularly for valorisation in the circular economy.

Validation of the Assurance® GDS for Cronobacter Tq II in Infant Formulas, Infant Cereals, Ingredients, and Environmental Samples Collaborative Study: First Action 2021.08.

The Assurance® GDS for Cronobacter Tq II assay is a nucleic acid amplification system for the qualitative detection of Cronobacter. The method uses an upfront concentration of the target organism from the enrichment by immunomagnetic separation (IMS) using the PickPen®device. The Assurance GDS for Cronobacter Tq II method was evaluated for Official Methods of AnalysisSM certification. The matrix was compared to the ISO 22964:2017: Microbiology of the Food Chain-Horizontal Method for the Detection of Cronobacter spp. standard and using an alternative confirmation procedure. The alternative method was evaluated using 10 g test portions in an unpaired study design for powdered infant formula (milk based with iron and DHA) containing probiotics. Eleven technicians from eight laboratories located within the United States and Europe participated in the collaborative study. Statistical analysis was conducted according to the probability of detection (POD) statistical model as presented in the AOAC validation guidelines. The difference in laboratory POD (dLPODC) values with 95% confidence intervals across collaborators was calculated for each level between the candidate and reference method results and between the candidate presumptive and confirmed results. Results obtained for the low inoculum level test portions produced a dLPOD value with a 95% confidence interval of 0.03 (-0.18, 0.15). The dLPOD results indicate equivalence between the candidate method and reference method for the matrix evaluated. The method also demonstrated acceptable inter-laboratory reproducibility as determined in the collaborative evaluation. There were no false negative results; the false positive rate was determined and produced a value of <2%. Based on the data generated, the method demonstrated Assurance GDS for Cronobacter Tq II assay produced acceptable interlaboratory reproducibility data and statistical analysis. The Assurance GDS for Cronobacter Tq II method is suitable for the rapid qualitative detection of Cronobacter in infant formulas, infant cereals, ingredients, and environmental samples.

Piloting a Proficiency Testing Program for Laboratory Sampling of Animal Feed Materials.

Laboratory sampling is a significant source of error in feed testing. Proficiency testing programs such as the Association of American Feed Control Officials Proficiency Testing Program are an effective means of assessing error in and among analytical methods. However, all proficiency test items are comminuted and blended to control variability among items, effectively minimizing sampling error. Currently there is no mechanism for monitoring sampling error among laboratories. The objective of this work was to investigate the feasibility of a proficiency testing program for laboratory sampling methods and provide insight into a program to advance the performance of sampling in laboratories. The study involved the fabrication of identical feed test items from feed ingredients and shipping the uncomminuted materials to volunteer laboratories. The volunteer laboratories followed in-house procedures for selecting test portions for routine feed tests. Tests on all the test portions for a single analyte were performed by a single laboratory, so that the variability in test results could be attributed to laboratory sampling processes to select test portions. The average RSD, %, for Item A and Item B, respectively, were as follows: protein, 5.08 and 5.23; non-protein nitrogen, 8.90 and 16.6; crude fat, 3.45 and 5.67; vitamin A, 33.9 and 26.9; calcium, 21.9 and 23.6; zinc, 17.9 and 27.9; and copper, 17.4 and 27.9. This study suggests that a proficiency testing program for laboratory sampling is feasible with manual manufacture of the test items, and data can be used to monitor laboratory sampling proficiency and also to compare the performance of different laboratory sampling methods. The data illustrates that each analyte has unique distributional and compositional heterogeneity, thus unique sampling error, even when multiple analytes are determined from a single test portion.

A-121 Drinking Behavior and Impulsivity in College Students

Abstract Objective: Individuals with chronic alcohol abuse have been shown to be more impulsive. Our objective in the present study was to assess drinking behavior in healthy college students and examine potential relationships between these drinking habits and impulsive behavior. Method: College students (n = 22) completed a survey about drinking behaviors, the Barratt Impulsiveness Scale (assessing various subscales of impulsivity), and the Color-Word Inference Test portion of the Delis Kaplan Executive Function System (DKEFS). The Color-Word Inference Test is a variation of the Stroop Test, testing the ability to inhibit prepotent responses. Results: We found a significant relationship (r = 0.428, p = 0.047) between total number of drinks per week (M = 5.59, SD = 5.70) and the Barratt motor impulsiveness subscale (M = 2.12, SD = 0.455). Looking for behavioral evidence of this relationship, we examined this same group with the DKEFS Color-Word Inference Test and found total number of self-corrected errors (M = 0.909, SD = 1.02) was positively associated with total number of drinks consumed per week (r = 0.446, p = 0.037). Conclusion(s): Preliminary results show a relationship between alcohol consumption and motor impulsivity. We propose that greater alcohol consumption may be an indicator that our subjects made errors on the Color-Word Inference Test due to impulsive tendencies and are then catching and correcting their errors soon after they are made. These findings are of interest considering the population examined are young and otherwise healthy college students, suggesting fairly mild but acute effects of moderately heavy alcohol consumption.

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.

Validation of the 3M™ Molecular Detection Assay 2-STEC Gene Screen (stx and eae) for Detection of Shiga Toxin Gene (stx1 and/or stx2) and Intimin Gene (eae) in Dried Cannabis Flower and Dried Hemp Flower: AOAC Performance Tested MethodSM 071902.

The 3M™ Molecular Detection Assay 2-STEC Gene Screen (stx and eae) method is based on gene amplification by the use of real time loop-mediated isothermal amplification when used with the 3M Molecular Detection System for the rapid and specific detection of Shiga toxin gene (stx1 and/or stx2) and intimin gene (eae) from Shiga toxin-producing Escherichia coli (STEC) in enriched products. The 3M Molecular Detection Assay 2-STEC Gene Screen (stx and eae) was approved as AOAC Performance Tested MethodSM Certificate No. 071902. This matrix extension study evaluated the 3M Molecular Detection Assay 2-STEC Gene Screen (stx and eae) method for detection of STECs in dried cannabis flower [>0.3% delta 9-tetrahydrocannabinol (THC)] and dried hemp flower (≤0.3% THC) at a 10 g test portion size. Testing followed procedures outlined in 3M Molecular Detection Assay 2-STEC Gene Screen (stx and eae) product instructions and Standard Method Performance Requirements (SMPR®) for Detection of Shiga Toxin-Producing Escherichia coli in Cannabis and Cannabis Products (AOAC SMPR 2020.012). The method was evaluated at low, high, and non-inoculated levels. Results showed no statistically significant difference between the presumptive positive 3M Molecular Detection Assay 2-STEC Gene Screen (stx and eae) results and the SMPR 2020.012 recommended cultural confirmations. This study provides data that demonstrate the 3M Molecular Detection Assay 2-STEC Gene Screen (stx and eae) is a reliable method for the rapid and specific detection of STEC organisms in dried cannabis flower and dried hemp flower. The 3M Molecular Detection Assay 2-STEC Gene Screen (stx and eae) method is suitable for the rapid and specific detection of STEC organisms in dried cannabis flower and dried hemp flower.

Validation of the 3M™ Molecular Detection Assay 2-STEC Gene Screen (stx) for Detection of Shiga Toxin Gene (stx1 and/or stx2) in Dried Cannabis Flower and Dried Hemp Flower: AOAC Performance Tested MethodSM 071903.

The 3M™ Molecular Detection Assay 2-STEC Gene Screen (stx) method is based on gene amplification by the use of real-time loop-mediated isothermal amplification when used with the 3M Molecular Detection System for the rapid and specific detection of Shiga toxin gene (stx1 and/or stx2) from Shiga toxin-producing Escherichia coli (STEC) in enriched products. The 3M Molecular Detection Assay 2-STEC Gene Screen (stx) was approved as AOAC Performance Tested MethodSM Certificate No. 071903. This matrix extension study evaluated the 3M Molecular Detection Assay 2-STEC Gene Screen (stx) method for detection of STECs in dried cannabis flower [>0.3% delta 9-tetrahydrocannabinol (THC)] and dried hemp flower (≤0.3% THC) at a 10 g test portion size. Testing followed procedures outlined in 3M Molecular Detection Assay 2-STEC Gene Screen (stx) product instructions and Standard Method Performance Requirement (SMPR®) for Detection of Shiga Toxin-Producing Escherichia coli in Cannabis and Cannabis Products (AOAC SMPR 2020.012). The method was evaluated at low, high, and non-inoculated levels. Results showed no statistically significant difference between the presumptive positive 3M Molecular Detection Assay 2-STEC Gene Screen (stx) results and the SMPR 2020.012 recommended cultural confirmations. This study provides data that demonstrate the 3M Molecular Detection Assay 2-STEC Gene Screen (stx) is a reliable method for the rapid and specific detection of STECs in dried cannabis flower and dried hemp flower. The 3M Molecular Detection Assay 2-STEC Gene Screen (stx) method is suitable for the rapid and specific detection of STECs in dried cannabis flower and dried hemp flower.

Validation of the 3MTM Molecular Detection Assay 2-Salmonella for detection of Salmonella in Dried Cannabis Flower and Dried Hemp Flower: AOAC Performance Tested MethodsSM 091501.

The 3M™ Molecular Detection Assay 2-Salmonella method is based on real-time loop-mediated isothermal amplification when used with the 3M Molecular Detection System for the rapid and specific detection of Salmonella in enriched products. The 3M Molecular Detection Assay 2-Salmonella was approved as AOAC INTERNATIONAL (AOAC) Performance Tested MethodSM (PTM) Certificate No. 091501 and as AOAC Official Method of AnalysisSM2016.01. This matrix extension study evaluated the 3M Molecular Detection Assay 2-Salmonella for detection of Salmonella in dried cannabis flower [>0.3% delta 9-tetrahydrocannabinol (THC)] and dried hemp flower (≤0.3% THC) at a 10 g test portion size. Matrix studies in dried cannabis and hemp flowers followed procedures outlined in 3M Molecular Detection Assay 2-Salmonella product instructions and Standard Method Performance Requirement (SMPR®) for Detection of Salmonella species in Cannabis and Cannabis Products (AOAC SMPR 2020.002). The method was evaluated at low, high, and non-contaminated levels. Results showed no statistically significant difference between the presumptive positive 3M Molecular Detection Assay 2-Salmonella results and the SMPR 2020.002 recommended cultural confirmations. This study demonstrates that the 3M Molecular Detection Assay 2-Salmonella is a reliable method for the rapid and specific detection of Salmonella in dried cannabis flower and dried hemp flower. The 3M Molecular Detection Assay 2-Salmonella method is suitable for the rapid and specific detection of Salmonella in dried cannabis flower and dried hemp flower.

Challenges of sampling grain for mycotoxin analysis

During growth and post-harvest storage, fungi can infect grain and produce secondary metabolites known as “mycotoxins ”. Some mycotoxins are regulated due to their potential hazardous health effects. Thusly, analysis of bulk grain consignments for mycotoxins is common in the grain trade. The heterogeneity of bulk grain with respect to deoxynivalenol (DON) and ochratoxin A (OTA), two regulated mycotoxins, was investigated. Variation of concentrations amongst individual wheat kernels was assessed, along with the variation within sub-samples and test portions produced from 10 kg laboratory samples, and amongst 500 t increments sampled during loading of bulk shipments (4,600 to 55,000 t). Concentrations in individual kernels ranged from &lt; 0.02 to 583 mg/kg for OTA and &lt; 0.3 to 414 mg/kg for DON. Analysis of the distribution of concentrations was limited due to the difference between the sample sets available for use; one was naturally infected (DON) and the other was inoculated and incubated under laboratory conditions (OTA). Bulk shipments were sampled during loading using a Canadian Grain Commission-approved automated cross-stream diverter-type sampler and in-line divider. Increments were combined, and 10 kg laboratory samples were prepared from the resulting composite using a Boerner divider, comminuted using a rotor beater mill, and sub-sampled using rotary sample division to produce representative sub-samples and test portions. Concentrations of OTA in the 500 t increment samples varied from &lt; 0.25 to 22.9 µg/kg; DON varied from &lt; 0.05 to 0.67 mg/kg. Within shipments, the OTA concentrations varied more amongst increments than did DON. The coefficients of variation for OTA ranged from 42 to 95% which were 2-4× greater than for DON. The results illustrate heterogeneity of bulk wheat relevant to international trade and regulated mycotoxins. Differences observed for DON and OTA also reflect how biological differences in mycotoxin production contributes to the challenges faced in analysing bulk whole grain for mycotoxins.

Level of Detection (LOD50) of Campylobacter Is Strongly Dependent on Strain, Enrichment Broth, and Food Matrix.

The detection of thermotolerant Campylobacter in food may be difficult due to the growth of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae during enrichment, resulting in false-negative samples. Therefore, the ISO protocol (ISO 10272-1:2017) suggests that, next to Bolton broth (BB), Preston broth (PB) is used as an enrichment broth to inhibit competitive flora in samples with suspected high levels of background microorganisms, such as ESBL-producing bacteria. However, the application of the strains used for validation of this ISO was not clearly characterized. This study examined the LOD50 (level of detection, the concentration where the probability of detection is 50%) of the validation strains (three C. jejuni and two C. coli strains) in BB and PB using different food matrices, namely, raw milk, chicken skin, frozen minced meat, and frozen spinach. The LOD50 was calculated by inoculating multiple portions with at least two inoculum levels. For each reproduction, eight test portions were used for each inoculum level and the test portion size was 10 g (chicken skin, frozen minced meat, and frozen spinach) or 10 mL (raw milk). Furthermore, the effect of artificially inoculated ESBL-producing E. coli on the LOD50 was examined to mimic the presence of ESBL-producing background microorganisms in the food matrices, namely, raw milk and chicken skin. In BB, the LOD50 of all strains tested in raw milk, chicken skin, and frozen spinach was rather low (0.4–37 CFU/test portion), while the LOD50 in frozen minced meat was higher and much more variable (1–1,500 CFU/test portion), depending on the strain. Generally, enrichment in PB resulted in higher LOD50 than in BB, especially for C. coli. Co-inoculation with ESBL-producing E. coli increased the LOD50 in BB, while PB successfully inhibited the growth of this competitive microorganism. In conclusion, food matrix and enrichment broth may have a large influence on the LOD50 of different Campylobacter strains. Therefore, it is not possible to give an unequivocal advice on when to use which enrichment broth, and this advocates the use of both methods in case of doubt. Furthermore, this study indicates specific strains that would be a good choice to use for Campylobacter method verification as described in ISO 16140-3:2021.

Determination of Re, Os, Ir, Ru, Pt, Pd Mass Fractions and 187Os/188Os Ratios of Organic‐Rich Geological Reference Materials

At present, reported data for Re‐PGE mass fractions (in particular) and 187Os/188Os isotope ratios of organic‐rich reference materials (RMs) are rare, hampering the comparison of data quality between different laboratories. In this study, we measured the Re‐PGE (Os, Ir, Ru, Pt and Pd) mass fractions, as well as 187Os/188Os isotope ratios of five shale RMs, including USGS SGR‐1b (oil shale), SBC‐1 (marine shale), SCo‐2 (silty marine shale), ShTX‐1 (calcareous organic‐rich shale) and ShCX‐1 (calcareous shale), and one oil RM, NIST RM 8505. The results show that the five shale RMs have similar upper continental crust‐normalised PGE‐Re patterns and are generally homogeneous in Re‐PGE mass fractions and 187Os/188Os isotope ratios at test portions of 0.2–0.5 g, and thus can be used as matrix‐matched RMs for Re‐Os and PGE of shale samples. The oil RM NIST 8505 and its asphaltene separates are also roughly homogeneous in Re‐PGE mass fractions and 187Os/188Os isotope ratios at test portions of 0.1–0.3 g and can potentially be used as an oil RM for Re‐Os and PGE.

Identification, synthesis, and quantification of a novel carbazole derivative as an impurity in the anthraquinone dye Ext. D&C Violet No. 2 (Acid Violet 43)

The anthraquinone anionic dye Acid Violet 43 (AV43, Colour Index No. 60730) is certifiable in the United States as Ext. D&C Violet No. 2 (EV2) for use as a color additive in externally applied cosmetics. The dye is also permitted in cosmetics in the European Union, Japan, and other countries. To be certified in the U.S., the dye may not contain more than 1% subsidiary colors. The present work was aimed at identifying an impurity, presumed to be a subsidiary color, found in batches of AV43 submitted for certification as EV2. The concentration level of the impurity in a sample of EV2 was enriched from ∼5.5% to ∼33%, and the enriched sample, 260 mg, was subjected to high-speed countercurrent chromatography (HSCCC). The resulting 50.7 mg of the isolated impurity was sufficient for its identification by spectroscopic methods as the sulfonated phthaloyl-carbazole derivative 6-hydroxy-9-methyl-5H-naphtho[2,3-a]carbazole-5,13(12H)-dione-11-sulfonic acid (AV43C). That previously unreported compound was synthesized (0.5 g) for use as a reference material to quantify the impurity in batches of EV2. Test portions of 29 batches, produced by 11 manufacturers from six countries, were analyzed by HPLC and UHPLC. The levels of AV43C ranged from <0.05% to 5.66% across batches. Carbazolization through an intramolecular Scholl-type reaction in the sulfonation step of the manufacturing process is suggested as the likely source of AV43C formation. Control of the conditions that enable carbazolization is proposed as a way to reduce or eliminate contamination by AV43C.

Determination and Identification of Nicarbazin, Measured as 4,4'-Dinitrocarbanilide (DNC), in Chicken Tissues by Liquid Chromatography With Tandem Mass Spectrometry: Final Action 2013.07.

BackgroundAOAC Method 2013.07 was adopted as First Action in 2013. Since then, the method has been used in numerous residue depletion studies with favorable comments from analysts.ObjectiveTo analyze data from residue depletion studies to support Final Action status.MethodTen residue depletion studies were conducted during May 2014 through May 2019. For each study, harvested incurred tissues were analyzed for nicarbazin using AOAC Method 2013.07 in 1 of 4 laboratories. Each analytical run included one or more fortified quality control test portions. The data from these known fortified matrix test portions were analyzed for reproducibility and repeatability.ResultsFor muscle tissues, relative recovery was 90.4% (95% CI 83.8 to 97.5); RSDr was 5.4% (95% CI 3.8 to 9.2); and RSDR was 7.9%. In the liver, values were 94.5% (95% CI 91.1 to 98.0), 5.8% (95% CI 4.1 to 9.9), and 6.8%, respectively. In the kidney, values were 91.5% (95% CI 85.3 to 98.1), 5.2% (95% CI 3.7 to 8.8), and 9.0%, respectively. In skin with adhering fat, values were 94.5% (95% CI 89.2 to 100.1), 8.9% (95% CI 6.3 to 15.1), and 8.9%, respectively. In all cases, repeatability and reproducibility were within acceptable limits.ConclusionsThe data and positive feedback support the transition of AOAC Method 2013.07 from First Action to Final Action.HighlightsFinal action status is supported by data collected during routine use of the method rather than a traditional multi-laboratory collaborative study. Data were subjected to statistical analysis using the pC-metamer, and then transformed back to the traditional C-metamer.

Measurement of Water Activity in the Presence of High Volatile Concentrations Using a Tunable Diode Laser-Single Laboratory Validation, First Action 2021.04.

Water activity is measured by equilibrating a test portion with a sealed head space and measuring the test portion temperature and the vapor density of the head space. The water activity is the ratio of head space vapor density to the saturation vapor density at test portion temperature. Headspace vapor density is typically measured using capacitance or chilled mirror sensors, but, when volatiles in significant concentration are present, these measurements may fail. Evaluate the accuracy of a tunable diode laser (TDL) for measuring the headspace vapor density and water activity of pharmaceutical preparations and food in the presence of non-aqueous volatiles. A commercial TDL water activity meter was calibrated against standards of known water activity and used to measure water activity of pharmaceutical preparations and food with high concentrations of non-aqueous volatiles. When no volatiles other than water vapor are present, this method is capable of measuring water activity with an accuracy of 0.005 or better. When high concentrations of volatiles such as ethanol, isopropanol, propylene glycol, tetrahydrofuran, or acetonitrile are present the uncertainty of the measurement increases. This is at least partly due to the uncertainty of the standards. Based on uncertainties in the water activity estimates of the water-organic mixtures, the uncertainties in water activity measurements with high concentrations of non-aqueous solvents is 0.02 or less up to mass fractions of the organic of 0.97. The theoretical background for TDL measurement of water activity is presented showing that the water vapor concentration is proportional to the area of the absorption line which is not affected by the presence of other volatiles.

Effect of Test Portion Mass on Vitamin A Testing in Animal Feed Materials.

BackgroundVitamin A test results have historically been notorious for poor repeatability and reproducibility. This problem has been discussed at length in Association of American Feed Control Officials Laboratory Methods and Services Committee meetings.ObjectiveThe objective of this work was to assess the effect of test portion mass on the repeatability of vitamin A test results.MethodsThe study was conducted in two parts. In Part I, fundamental sampling error (FSE) was determined experimentally through replicated (n = 16) vitamin A testing of three animal feed materials. The testing followed rigorous test portion selection for 10 g and 100 g test portions. In Part II, FSE calculations were made (1) using theoretical equations based on vitamin A as a liberated analyte and (2) on representing the particles in feed materials. Particle size characterization of vitamin A ingredients was estimated by microscopy and further evaluated by particle size analysis.ResultsRSDs, % for vitamin A determinations ranged from 10.5–24.7, and 2.26–10.7 for 10 g and 100 g test portions, respectively. FSE calculated for Ingredient A ranged from 18.3–101% and 5.79–32.0% for 10 g and 100 g test portions, respectively, and for Ingredient B, ranged from 10.2–56.2% and 3.21–17.8% for 10 g and 100 g test portions, respectively.ConclusionTest portion mass has a substantial impact on FSE and is an important factor in controlling the random error in vitamin A testing. FSE equations are useful to approximate minimum test portion mass.HighlightsVitamin A method development should use theoretical predictions and experimental verification to guide test portion mass. Strategies to deal with the larger test portion masses will be key to validating new methods.

Are sample size and sample preparation for mycotoxin quantitation in grain products getting trivialized?

Sampling and sample preparation (grinding and subsampling) are largest sources of variability that negate precision and accuracy of mycotoxin quantitation, particularly in grains. In general, halving sample or sub-sample (e.g., ground test portion) size doubles variance. Therefore, this paper reports on trends in sample and test portion masses used for the quantification of mycotoxin in maize between 1991 and 2020 by reviewing articles on mycotoxin quantitation in maize (grain and flour) published during this period. About 50% of the articles did not explicitly state the sample mass that was ground. Sample and test portion masses show a significant (p < 0.05) decline over the study period. In addition, over two-thirds of the articles did not specify the type of grinder and sieve sizes used in their analysis. Therefore, our findings suggest that standardized sampling plans with emphasis on laboratory sample size and sample preparation methods for maize are increasingly being overlooked during mycotoxin quantitation and increasing the uncertainty associated with estimating the true mycotoxin concentration in grain lots.

Sampling and sub-sampling of granular waste: size of a representative sample in terms of number of particles

This paper elucidates the theoretical principles behind the calculation of the size of a representative sample of granular solid waste. The key concept is the number of particles that must be present in a sub-portion of matter to be representative of a larger portion of matter. This depends on the fraction of particles in the waste batch showing the properties of interest, which shall be measured. A representative sample must include a fraction of particles of interest reliably similar to that of the waste batch to be characterized, with a controlled variability. In this context, it is demonstrated that the number of particles of interest that must be collected in a representative sample is 100. From this requirement, the mass of a representative sample can be calculated based on the knowledge of the frequency of particles of interest of the waste lot to be characterized. Data on particles concentrations in different samples of WEEE plastic scraps exemplifies how the presence in the sample of enough rare particles showing the property of interest is key to ensure reliable measurements. Further, the assumptions made on the controlled degree of variability to determine the minimum number of particles are discussed based on data on achievable intra- and inter-laboratory variability of analytical standards for waste characterization. Accordingly, the mass of laboratory samples and test portions recommended in published sampling plans or analytical standards are assessed for the occurring number of particles.