Repeatability Relative Standard Deviation Research Articles

AMPEROMETRIC IMMUNOSENSORS BASED ON CARBON NANOMATERIALS AND RHENIUM CLUSTERS FOR THE DETERMINATION OF TRICYCLIC ANTIDEPRESSANTS IN A SEQUENTIAL INJECTION SYSTEM

A method of sequential injection determination of tricyclic antidepressants (amitriptyline, desipramine, imipramine) using amperometric immunosensors based on screen-printed graphite electrodes modified by carbon nanomaterials (carbon nanotubes, graphene oxide or fullerene) in combination with hexarhenium chalcogenide clusters is proposed. Sequential injection analysis was performed at a sweep rate of 10 mV/s; the flow rate (supporting electrolyte – phosphate buffer solution with pH 7.0) was also varied from 20 to 40 µl/s. Composition of the modifier affects the analytical capability of immunosensors. Screening of various types of modifiers showed that the immunosensor based on graphene oxide and cyanide complexes of rhenium chalcogenide clusters exhibited the highest sensitivity of 23.9±0.9 with a range of working concentrations of 1·10–10–1·10–5 M, and even wider range of detectable concentrations, 1·10–10–1·10–4 M was observed for the immunosensor based on fullerene and cyanide complexes of rhenium chalcogenide clusters. The lowest limit of the determined contents was (4–7)·10–11 M. Relative standard deviation of repeatability (Sr) did not exceed 0.046. The results obtained show that the proposed immunosensors can be used in sequential injection determination of trace amounts of medicinal compounds (antidepressants) in biomedical objects.

Development and Validation of a Simple Method to Quantify Contents of Phospholipids in Krill Oil by Fourier-Transform Infrared Spectroscopy.

This study focuses on developing a quantification method for phosphatidylcholine (PC) and total phospholipid (PL) in krill oil using Fourier-transform infrared (FT-IR) spectroscopy. Signals derived from the choline and phosphate groups were selected as indicator variables for determining PC and total PL content; calibration curves with a correlation coefficient of >0.988 were constructed with calibration samples prepared by mixing krill oil raw material and fish oil in different ratios. The limit of detection (LOD, 0.35–3.29%) of the method was suitable for the designed assay with good accuracy (97.90–100.33%). The relative standard deviations for repeatability (0.90–2.31%) were acceptable. Therefore, both the methods using absorbance and that using second-derivative were confirmed to be suitable for quantitative analysis. When applying this method to test samples, including supplements, the PC content and total PL content were in good agreement with an average difference of 2–3% compared to the 31P NMR method. These results confirmed that the FT-IR method can be used as a convenient and rapid alternative to the 31P NMR method for quantifying PLs in krill oil.

Quantification of total sugars and reducing sugars of dragon fruit-derived sugar-samples by UV-Vis spectrophotometric method

In the present work, the phenol-sulfuric acid method and the 3,5-dinitrosalicylic acid (DNS) method were developed with the aim to quantitatively analyze total sugars and reducing sugars, respectively. In regard with the phenol-sulfuric acid assay, 1.0 mL of sample was treated with 1.0 mL of 5% phenol, 5.0 mL of concentrated H2SO4 and measured at 485 nm, with the linearity range of 10–100 ppm for total sugars. The DNS method was performed on 2.0 mL of sample, using 1.5 mL of DNS at 80 °C for 10 minutes and measured at 510 nm, with the linearity range of 50–400 ppm for reducing sugars. The sugar contents of white dragon fruit-derived sugar-samples (extracted from species in Binh Thuan province, Vietnam) were also estimated by the above measured methods, exhibiting the total sugars of above 90% and the reducing sugars of above 5%. The methods were well-performed with the acceptable relative standard deviations of repeatability in accordance with the Association of Official Analytical Chemists (AOAC).

Dual-labeling ratiometric electrochemical strategy initiated with ISDPR for accurate screening MecA gene

An outstanding dual-labeling ratiometric electrochemical biosensor based on isothermal strand displacement polymerization reaction (ISDPR) for highly sensitive and selective detection of mecA gene has been proposed. Concretely, in the presence of mecA gene, the addition of methylene blue (MB)-labeled primer and polymerase induced recycling amplification to change the structure of the ferrocene (Fc)-labeled hairpin probe, thereby releasing abundant target gene to realize the signal amplification and dual-signal output. Through this process, the electrochemical responses of Fc (IFc) and MB (IMB) were both substantially reduced and increased proportionally, ensuring that the value of IMB/IFc can accurately reflect the true detection level of mecA gene. Benefiting from the “signal-on/off” strategy, the fabricated biosensor exhibited outstanding sequence specificity to discriminate mismatched mecA gene, which verified to be 2.72 times that of single-label detection for perfect match/single base mismatch (PM/MM) discrimination ratio. This strategy effectively integrated the advantages of signal amplification and ratiometric modes, making the biosensor exhibit a broad working range with 10 fM - 3000 pM and a limit of detection (LOD) with 3.33 fM (S/N = 3). Moreover, the proposed biosensor has good feasibility for mecA gene determination in water samples due to acceptable recoveries (95–115%) and repeatability relative standard deviations (RSD) value of 4%. This will provide a powerful sensing platform for improving accuracy and decreasing background signal of sensor for ARGs screening in environmental monitoring.

A liquid chromatography coupled to tandem mass spectrometry method for the quantification of spiramycin and its active metabolite neospiramycin in milk of major and minor species: Validation using the accuracy profile

A liquid chromatography with tandem mass spectrometry (LC-MS/MS) method was developed for the simultaneous quantification of residues of spiramycin, a macrolide antibiotic, and its active metabolite neospiramycin in cow's milk as well as in minor species ‘milk, goat and ewe. Spiramycin-d3 was used as internal standard for quantification of both analytes. This analytical method was validated using a global accuracy profile as a graphical decision tool built according to the trueness and the precision of the method. A unique and optimal linear model with logarithm transformation (with a determination coefficient of 0.9991) allowed the measurement of both analytes in the milks of the three animal species, in a wide range from 0.2 to 10 times the Maximal Residue Limit (MRL) (40–2000 µg.kg−1). The limits of detection and quantification were 13 µg.kg−1 and 40 µg.kg−1, respectively. The accuracy profile was established to get 80% of future measurements in routine assays that will fall within the acceptance limits. Trueness of the method, expressed as relative bias, was comprised between –1.6% and 5.7% over the whole range of concentrations. The mean relative standard deviation for repeatability and intermediate precision were comprised between 1.1% and 2.7%; 2.5 and 4.2%, respectively, in all levels of concentration for the three milks. Moreover, a two-order polynomial function was used to model the relative expanded uncertainty with a determination coefficient of 0.834. This function aimed to determine the uncertainty of the future quantifications within the validated dosing range. Overall, the global accuracy profile highlighted the reliability of the method for the routine assays of spiramycin and neospiramycin even in milk from minor species (goat, ewe) by using the most accessible milk (often from cow), while guaranteeing a very high proportion of samples within the fixed acceptance limits. The applicability of this method was tested during a depletion study of spiramycin and neospiramycin in the milk of cow, goat and ewe. The developed analytical method will be useful to assess the distribution profile of the antibiotic and its metabolite in milk of minor species where few studies are available.

Automated spectrophotometric platform for the quantification of multiple nucleic acid samples

A novel automated spectrophotometric platform was developed to upgrade a conventional prototype instrument platform for commercial use. A pulsed xenon flash lamp was chosen as the light source to improve the light output and a microsampling system was employed to precisely and rapidly aspirate micro-volume sample solutions. In addition, a three-axis positioning system was devised to increase the measurement capacity. All electrical components of the developed platform were linked and controlled with an integrated system. To verify the measurement performance and automated operation, a series of experiments were carried out. Double-stranded DNA samples at seven concentrations were automatically quantified. The concentrations were estimated with high linearity (R 2 ≒ 0.9998), repeatability (relative standard deviation ≤10.3%), and accuracy (>87.5%) across the concentration range from 0.25 to 10 ng/μL. In addition, this platform can be used in many different ways by changing a few parts or a sub-system and will be most useful in laboratories that handle a large number of samples. It is expected that the developed platform will be utilized for measuring circulating cell-free DNA and for quality control of next-generation sequencing, forensic medicine, noninvasive prenatal tests, and liquid biopsies.

Results of an Interlaboratory Comparison of a Liquid Chromatography-Isotope Ratio Mass Spectrometry Method for the Determination of 13C/12C Ratios of Saccharides in Honey.

BackgroundStable carbon isotope analysis of sugars in honey by LC–isotope ratio mass spectrometry (IRMS) is a useful tool for detecting adulteration of honey with extraneous sugar. Purity criteria based on 13C/12C ratios of saccharides in honey, determined by LC–IRMS of a large number of authentic honey samples, have been elaborated. However, no interlaboratory comparison (ILC) has yet been performed to estimate the precision of the method under reproducibility conditions.ObjectiveTo address this knowledge gap an ILC involving 14 laboratories and using six honey samples was conducted.MethodsThe participants were allowed to use their LC–IRMS-based method of choice for sample preparation and compound separation.ResultsThe precision figures were estimated according to ISO 5725:1994. The repeatability relative standard deviation (RSDr) for the determination of δ13C values of fructose and glucose varied between 0.3 and 0.5%, with 0.3 and 1.0% for disaccharides, and 0.7 and 2.8% for trisaccharides. The RSDR varied between 0.8 and 1.8% for the monosaccharides, 1.0 and 1.5% for disaccharides, and 1.4 and 2.8% for trisaccharides.ConclusionBased on the obtained precision data the LC–IRMS method for the determination of 13C/12C ratios of saccharides in honey was considered fit for the conformity assessment of honey with established purity criteria.HighlightsPrecision estimates for a LC–IRMS method to determine 13C/12C ratios of saccharides in honey were obtained through an ILC. The data created can form the basis for the standardization of the method by interested standards-developing organizations for use in official control.

Multitoxin immunoaffinity analysis of aflatoxins and ochratoxin A in spices

AbstractA multitoxin method for aflatoxins (AFs) and ochratoxin A (OTA) was modified and validated to analyze black pepper, colorífico, nutmeg, paprika, and turmeric. The method consisted of acetonitrile, NaHCO3 and methanol extraction solution, multimycotoxin immunoaffinity column purification and isolation, reversed‐phase liquid chromatography separation, and fluorescence detection. The limit of detection was <0.1 ng/g for AFs and OTA. Mean recoveries of added AFs ranged from 68 to 88% with relative standard deviation of repeatability (RSDr) values <15%; aflatoxin B1 (AFB1) from 69 to 92% with RSDr <17%; and OTA from 75 to 110% with RSDr <10% at spiked levels ranged from 8 to 40 ng/g for AFs, 4 to 20 ng/g for AFB1, and 4 to 20 ng/g for OTA, respectively. Recoveries of added aflatoxin G2 were approximately 50% at spiked levels ranged from 1 to 5 ng/g. Recoveries of aflatoxin B2 and aflatoxin G1 were >70%. The linearity of the method for AFs ranged from 0.4 to 100 ng/g, for OTA from 0.2 to 40 ng/g with R2 values exceeding 0.99. Results of a single laboratory validation study validated the performance of this method meeting the method acceptability criteria. No differences in toxin detection were determined in robustness testing in which minor changes were introduced to the method.

Determination of Alternaria Toxins in Tomato, Wheat, and Sunflower Seeds by SPE and LC-MS/MS-A Method Validation Through a Collaborative Trial.

Background Alternaria toxins are ubiquitous contaminants in highly consumed food products. Therefore, they are candidates to be regulated by EU legislation. In this context, the availability of reliable analytical methods is a keystone both for protecting the health of citizens and smooth functioning of the European market.ObjectiveThis paper describes an advanced LC-MS/MS method based on isotope dilution quantification suitable for the determination of altenuene, alternariol, alternariol monomethyl ether, tenuazonic acid, and tentoxin in tomato puree, wheat, and sunflower seeds.MethodsThe method has been validated in an interlaboratory study that included the analysis of both spiked and naturally contaminated food commodities. Twenty-three participants contributed with analytical data.ResultsThe average recoveries and relative standard deviations for repeatability and reproducibility obtained across the tested matrixes were: 97, 8.0, and 23%, for altenuene, respectively; 95, 9.2, and 17% for alternariol, respectively; 98, 6.4, and 13% for alternariol monomethyl ether, respectively; 97, 4.2, and 9.3% for tenuazonic acid, respectively; and 102, 5.6, and 15% for tentoxin, respectively. The method enabled the determination of all tested Alternaria toxins close to or below 1 µg/kg.ConclusionOverall, the method showed a satisfactory trueness and precision, complying with the requirements for the monitoring of mycotoxins in food in the EU. It is currently under evaluation by the European Committee for Standardization for adoption as a standard method.HighlightsIsotope dilution mass spectrometry method for the determination of Alternaria toxins in food.

In-House Validation of an SPE-GC-FID Method for the Detection of Free and Esterified Hydroxylated Minor Compounds in Virgin Olive Oils.

Minor compounds in vegetable oils are distributed between free and esterified forms, and the ratio of these two fractions could represent an important parameter for assessment of oil authenticity. A simple method based on offline SPE-GC-FID for the analysis of free and esterified hydroxylated minor compounds in olive and sunflower oils has been developed and in-house validated. A satisfactory repeatability relative standard deviation (<7.5%) was obtained in all cases. The method, which requires simple instrumentation, allows for reliable quantification in a single chromatographic run with the advantages of minimizing sample manipulation, use of toxic solvents and reagents, and time consumption. The analytical procedure was applied to pure oil samples, including 15 authentic extra virgin olive oils collected from different European countries (Spain, Italy, Greece, and Portugal). Finally, the proposed SPE-GC-FID methodology could detect changes in the ratio between the free and esterified forms in pure extra virgin olive oil when mixed with refined sunflower oil at different percentages of 2, 5, 10, 15, and 20% (w/w) to simulate adulteration.

Determination of 2, 4-Dichlorophenol, 2, 4-Dinitrophenol, and Bisphenol a in River Water by Magnetic Solid-Phase Extraction (MSPE) Using β-Cyclodextrin Modified Magnetic Ferrite Microspheres and High-Performance Liquid Chromatography – Diode Array Detection (HPLC-DAD)

β-Cyclodextrin modified magnetic microspheres were synthesized and used as an effective adsorbent for the solid-phase extraction of three phenols from water samples. Scanning electron microscopy and Fourier transform infrared spectrometry were used to characterize the adsorbents. The major parameters affecting the extraction and desorption efficiencies, such as adsorbent dosage, extraction time, pH, ionic strength, and eluent type were systematically optimized. Under these conditions, three phenols in water samples were extracted and determined by high performance liquid chromatography (HPLC) with diode array detection (DAD). Limits of detection (LODs) of 0.04–0.34 ng mL−1 and limits of quantification (LOQs) from 0.13 to 1.14 ng mL−1 were achieved with good repeatability (relative standard deviation <7.5%). The developed method was applied for the determination of 2,4-dichlorophenol, 2,4-dinitrophenol and bisphenol A in spiked Yangtze River water, and the recoveries were from 81.0% to 94.9%. The results demonstrated that the combination of magnetic solid-phase extraction (MSPE) with HPLC-DAD is suitable for the determination of trace phenolics in environmental water.

Development of an advanced DNA biosensor for pathogenic Vibrio cholerae detection in real sample

Due to the epidemics of emerging microbial diseases worldwide, the accurate and rapid quantification of pathogenic bacteria is extremely critical. In this work, a highly sensitive DNA-based electrochemical biosensor has been developed to detect Vibrio cholerae using gold nanocube and 3-aminopropyltriethoxysilane (APTES) modified glassy carbon electrode (GCE) with DNA carrier matrix. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) experiments were performed to interrogate the proposed sensor at each stage of preparation. The biosensor has demonstrated high sensitivity with a wide linear response range to target DNA from 10−8 to 10−14 (R2= 0.992) and 10−14 to 10−27 molL−1 (R2= 0.993) with a limit of detection (LOD) value of 7.41 × 10−30 molL−1 (S/N = 5). The biosensor also exhibits a selective detection behavior in bacterial cultures that belong to the same and distant genera. Moreover, the proposed sensor can be used for six consecutive DNA assays with a repeatability relative standard deviations (RSD) value of 5% (n = 5). Besides, the DNA biosensor shows excellent recovery for detecting V. cholerae in poultry feces, indicating that the designed biosensor could become a powerful tool for pathogenic microorganisms screening in clinical diagnostics, food safety, and environmental monitoring.

Gas flow-assisted dispersive liquid-phase microextraction to analyze parabens in personal hygiene products

Gas flow-assisted dispersive liquid-phase microextraction combined with GC-FID was employed for the analysis of parabens in hygienic products. Some strategies have been used to overcome the drawbacks of classic DLLME. In this regard, the flow of a neutral gas was employed to disperse the extraction solvent in the sample. Fatty alcohols as sustainable solvents were replaced by traditional toxic organic extraction solvents. The centrifugation step was deleted by using the salting-out phenomenon. Variables influencing the extraction efficiency, such as the type and volume of extraction, ionic strength, pH, and extraction time, were optimized based on the univariate technique. Under optimal conditions calibration models were linear in the range of 5–10,000 μg L−1. The limits of detection were obtained in the 1.0–1.7 μg L−1 range, and limits of quantitative measurement were between 3.4 and 5.7 μg L−1. The relative standard deviations for repeatability and reproducibility of the method were obtained in the range of 2.05–3.89% and 6.45–9.55%, respectively. A spiking approach using standard material was applied to evaluate accuracy. The relative recoveries were found to be in the 96–103% range. In these tests, the relative standard deviations were < 4.2%, which specified proper accordance with the standard concentrations.

Pesticides in edible mushrooms in Vietnam

ABSTRACT Maximum residue limits (MRLs) for pesticides have been established for edible mushrooms in order to control quality and ensure benefits of consumers in numerous countries, especially areas comprising Europe. In this study, by means of optimising extract purification conditions, a high sensitivity and reliability method to simultaneously determine 180 pesticides in mushrooms has been proposed. Matrix effects were minimised by combining QuEChERS extraction and a mixed mode of SPE cleaned up with different adsorbent materials after sample preparation. The method was completely validated following the requirements of SANTE/12682/2019. The LOQs ranged from 2 to 5 μg/kg, well below the MRLs as regulated by the EU (10–50 μg/kg). Both relative standard deviation of repeatability (RSDr) and reproducibility (RSDR) were less than 20% and recoveries varied from 70 to 120%. Therefore, this method was considered to be suitable for routine analysis of multi-pesticide residues in edible mushrooms.

Critical quality attribute assessment of big brand traditional Chinese medicine: quality control method of Huangjing Zanyu Capsules based on chemical properties of characteristic components

The chemical properties of characteristic components are significant to the manufacturing quality control of big brand traditional Chinese medicine. In this study, the Huangjing Zanyu Capsules were used as the research carrier to determine the content of five characteristic components including icraiin, emodin, schisandrin A, 2,3,5,4'-tetrahydroxystilbene-2-O-β-D-glucoside, and osthole simultaneously by high-performance liquid chromatography(HPLC). The results showed that the chemical properties of five cha-racteristic components had a good linear relationship(r&gt;0.999 9) within the quantitative range; the relative standard deviations(RSD) was 0.11%-2.0% and 0.25%-2.8% respectively for intra-day and inter-day precision; the RSD of repeatability was 1.8%-2.6%; the RSD of stability within 48 hours was 0.19%-2.8%, and the average recovery rate was 95.52%-100.1%, all meeting the requirements of pharmaceutical quantitative analysis. Additionally, the interval estimation method was used to directly reflect the distribution of samples with abnormal chemical properties of characteristic components, and the results showed ten samples were detected beyound the 95% control line of confidence level. Multivariate statistical process control(MSPC) method was used to monitor the abnormal samples of Huangjing Zanyu Capsules collectively, and the results showed that two samples were beyond the 95% control line of Hotelling's T~2 and three samples beyond the 95% control line of squared prediction error(SPE), indicating consistent quality control of Huangjing Zanyu Capsules. In conclusion, the proposed method is not only accurate and efficient but also a compensation for the traditional single-component quality control method, providing a scientific basis for the quality control in manufacturing process of Huangjing Zanyu Capsules. Furthermore, it could also serve as a reference method for the quality control in manufacturing big brand traditional Chinese medicine.

An LC-MS/MS Method for the Determination of Antibiotic Residues in Distillers Grains: Collaborative Study.

Antibiotics are used in ethanol production to discourage the growth of bacteria that would lower the yield of the product. Any antibiotic residues remaining in distillers grain (DG) co-product could lead to antimicrobial resistance, which is a public health concern. The U.S. Food and Drug Administration (FDA) Center for Veterinary Medicine (CVM) previously developed an LC-MS/MS analytical method to detect residues of erythromycin A, penicillin G, virginiamycin M1, and virginiamycin S1 in DG to enable regulatory decision making. The objective of this study was to ensure the method's robustness by carrying out a multi-laboratory validation of the method. Test portions were extracted with a mixture of acetonitrile and buffer. The extract was cleaned by solid phase extraction. The concentrated eluant was reconstituted and analyzed by LC-MS/MS. Eight laboratories participated in the study. Average accuracies for the combined three matrixes for all four compounds at all fortification levels ranged from 83->109% with repeatability relative standard deviation (RSDr; within laboratory) ≤17% and reproducibility relative standard deviation (RSDR; between laboratory) ≤21%. The Horwitz ration (HorRat) values ranged 0.4-1.0 indicating that method reproducibility is acceptable. An interlaboratory study was successfully conducted to evaluate an LC-MS/MS method for the determination of the drugs of interest in DG. The results demonstrate that the method is fit for purpose to determine the drugs in DG and could serve as a regulatory method capable of being used for compliance actions for DG containing these antibiotic contaminants. The method was posted to the FDA/Foods Program Compendium of Analytical Laboratory Methods.

An International Collaborative Study on Trypsin Inhibitor Assay for Legumes, Cereals, and Related Products

AbstractFor determining trypsin inhibitor activity (TIA) in soy products, the American Oil Chemists' Society (AOCS) Method Ba 12‐75 has been used. It measures differences in absorbance at 410 nm of bovine trypsin activity toward a synthetic substrate (Nα‐benzoyl‐DL‐arginine‐p‐nitroanilide) in the absence and presence of an inhibitor. Recently, a significantly improved method was developed (JAOCS, 2019, 96:635–645), featuring 5 mL of total assay volume, enzyme‐last sequence, and single inhibitor level in duplicate. It is proposed as the AOCS Method Ba 12a‐2020. As a part of the AOCS method approval process, a collaborative study involving 12 international laboratories was conducted to evaluate the performance of the proposed method. The study involved measuring TIA in 10 selected test samples plus a blind duplicate. They included soybeans, pulses, cereals, and their processed products (flours, concentrates, and isolates). After rigorous statistical treatment of the data, only three outliers were removed from the data of two samples. Repeatability relative standard deviations (RSDr) for the 11 samples ranged from 0.99% to 5.52%. Reproducibility RSD (RSDR) ranged from 7.07% to 22.92%, with seven samples having RSDR around 10% or less. The remaining four samples had very low TIA, and their RSDR values ranged from 13.34% to 22.92%. The study has demonstrated reliable performance of the proposed AOCS method. Several collaborators carried out additional experiments addressing some aspects of the method, leading to further refinements. The proposed method is undergoing evaluation by the AOCS Uniform Methods Committee for adoption as an Official Method for measuring TIA in various legume and grain products.

Determination of Lactose Concentration in Low-Lactose and Lactose-Free Milk, Milk Products, and Products Containing Dairy Ingredients, Enzymatic Method: Single-Laboratory Validation First Action Method 2020.08.

BackgroundThe AOAC Stakeholder Panel on Strategic Food Analytical Methods issued a call for methods 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 developed specifically to address the need for accurate enzymatic testing in lactose-free samples.ObjectiveK-LOLAC was validated for measurement of lactose in low-lactose and lactose-free milk, milk products, and products containing dairy ingredients. A single-laboratory validation (SLV) of the method is reported.MethodK-LOLAC is an accurate and sensitive enzymatic method for the rapid measurement of lactose in low-lactose or lactose-free products. Validation analysis was performed on a sample set of 36 commercial food and beverage products and a set of 10 certified reference materials. Parameters examined during the validation included working range and linear range, selectivity, LOD, LOQ, trueness (bias), precision (repeatability and intermediate precision), robustness, and stability.ResultsFor all samples tested within the lower range (10–100 mg/100 g or mL), recoveries varied from 93.21–114.10%. Recoveries obtained for samples in the higher range (>100 mg/100 g or mL) varied from 94.44–108.28%. All materials had repeatability relative standard deviations (RSDr and RSDir) of <9%.ConclusionsThe commercial K-LOLAC assay kit, as developed by Megazyme, meets the requirements set out under SMPR 2018.009.HighlightsK-LOLAC is a robust, quick, and easy method for analysis of lactose in foodstuffs and beverages.

Validation of a multi-analyte HPLC method for the determination of carotenoids used as feed additives in fish and poultry feed: results of an interlaboratory study

ABSTRACT The performance characteristics of a multi-analyte method for the determination of all 10 carotenoids authorised as feed additives within the EU were assessed via an interlaboratory study. The analytical method is based on reversed phase high performance liquid chromatography (RP-HPLC) coupled to an optical detector set at 410 nm. The analysis is particularly challenging due to the presence of various stereoisomers of each carotenoid, and the use of these compounds via natural or synthetic formulations, requiring a special sample preparation. EU regulations specifying the conditions of use set legal limits for these substances in compound feedingstuffs ranging from 6 mg kg−1 to 138 mg kg−1, depending on the individual carotenoid and the target animal for which the feed is supplemented with this carotenoid. The purpose of the multi-analyte method validated in this paper is to facilitate the monitoring of carotenoids at relevant levels when used as feed additives in compound feedingstuffs and pre-mixtures. The interlaboratory study delivered precision data for 43 different analyte/mass fraction/matrix combinations, covering a mass fraction range of the target analytes from 2.6 mg kg−1 to 3861 mg kg−1. The relative standard deviations for repeatability (RSDr) varied from 2.2 to 16.2 % with a mean value of 6 %, while the relative standard deviations for reproducibility (RSDR) varied from 6.8 to 39 % with a mean value of 21 %. Given the broad scope of the method covering 10 carotenoids added to compound feedingstuffs and pre-mixtures via different formulations, this multi-analyte method is considered fit for the intended purpose.

INFRAVERMELHO PORTÁTIL NA REGIÃO DO PRÓXIMO (NIR) APLICADO NO CONTROLE DE QUALIDADE DE CAFÉS ADULTERADO POR BORRA

PORTABLE NEAR INFRARED SPECTROSCOPY APPLIED TO THE QUALITY CONTROL OF COFFEE ADULTERED BY GROUNDS. The objective of this work was to control the purity level of canephora coffees (Conilon coffee) from the state of Espírito Santo (Brazil), as a function of the addition of grounds produced by the coffees themselves using a portable microspectrometer in the infrared region. (microNIR), associated with chemometric tools. The PCA model grouped the coffees according to the level of adulterant in the samples and showed that the presence of moisture and polysaccharides is important for the discrimination between pure and adulterated samples. PLS-DA and SIMCA classification models were built with commercial samples and resulted in the discrimination of authentic and non-authentic samples with accuracy values above 90% and 82% for PLS-DA and SIMCA, respectively. The quantification results presented by the PLS model were satisfactory for all models, reaching the best results at 75 °C with RMSEP values of 6.13 wt%, R2p = 0.9917; and LOD in the range of 5.6-8.9 wt%; LOQ = 17-26.8 wt%, according to IUPAC; relative standard deviation for repeatability of 1.0 and 1.7 wt%; and intermediate precision of 3.4 and 1.1 wt% for low (&lt;10 wt%) and high (≈ 90 wt%) levels of adulterants, respectively. Therefore, this work represents the first exploratory study to analyze adulterations with coffee grounds by portable NIR, demonstrating the potential of the equipment against this type of adulteration.