Determination Of Total Amino Acids Research Articles

Determination of Total Amino Acids in Infant Formulas, Adult Nutritionals, Dairy, and Cereal Matrixes by UHPLC-UV: Interlaboratory Validation Study, Final Action 2018.06.

A method for the quantification of total amino acids (including taurine and excluding tryptophan) using ultra- HPLC separation coupled to UV detection (UHPLC-UV) was granted First Action status (AOAC 2018.06) by the AOAC INTERNATIONAL Stakeholder Program for Infant Formula and Adult Nutritionals (SPIFAN) in 2018. An interlaboratory study was conducted to further assess method performance against the AOAC Standard Method Performance Requirements (AOAC SMPR® 2014.013). Dairy and cereal matrixes were added to expand the scope of the method in collaboration with IDF (International Dairy Federation), ISO (International Organization for Standardization), and AACCI (American Association of Cereal Chemists International, now Cereals & Grains Association). Sixteen different matrixes were chosen to cover the requirements of AOAC, IDF/ISO, and AACCI. Blind duplicate samples were organized into specific series to ensure that each pair was analyzed on the same day. Fifteen laboratories returned results. Data from four laboratories were considered invalid and removed from the dataset. Remaining data were assessed according to the Appendix D of the AOAC Official Methods of AnalysisSM (guidelines for collaborative study procedures). This method generally met the requirements listed in the SMPR for infant formulas and adult nutritionals, except for taurine. Method performance was comparable in dairy and cereal matrixes. Five different UHPLC instruments were used with either commercial or in-house reagents, demonstrating that the method is not limited to a single supplier. This method was recommended for Final Action in infant and adult/pediatric nutritional formulas by the AOAC SPIFAN Nutrients Expert Review Panel in April 2021, with the exception of taurine. The corresponding IDF/ISO Draft International Standard (DIS) was approved by national bodies in May 2022, and comments collected during the ballot were incorporated into this manuscript. AOAC Official Method 2018.06 for the determination of total amino acids in infant formulas, adult nutritionals, dairy, and cereal matrixes was successfully validated in an interlaboratory study.

A novel biosensor based on Blu-ray disc coating film for determination of total amino acid content in tea leaves.

Biosensor substrate materials are a key research focus in the field of sensors. Blu-ray discs (BDs) as universal sensor substrates are advantageous in comparison with other substrates (conventional paper and polycarbonate) in terms of easier activity treatment and higher density of reactive groups on the film surface. In this study, a novel and simple microfluidic biosensor based on BD coating film was developed by treating with sodium hydroxide solution and a piece of filter paper at slightly elevated temperatures. There are no significant physical damages to the substrate morphology, and the aging effect is minimal. The unique wetting, optical, and self-cleaning properties of the modified surfaces can be demonstrated in the paper. We have tested this new type of biosensor substrates for assay applications (the determination of total amino acids in tea leaves), which showed excellent performance in terms of sensitivity and reproducibility. The novel biosensor substrate material based on a simple BD coating film displayed preferable merits with easy making, low cost, easy using, and extensive application prospect.

Total Amino Acids by UHPLC–UV in Infant Formulas and Adult Nutritionals, First Action 2018.06

Abstract Background: An acid hydrolysis ultrahigh-performance LC–UV method was evaluated for the determination of total amino acids in infant formula and adult/pediatric nutritional formula. Objective: It was assessed for compliance against AOAC INTERNATIONAL Standard Method Performance Requirements (SMPR®) established by the Stakeholder Panel for Infant Formula and Adult Nutritionals (SPIFAN). Methods: A single-laboratory validation (SLV) study was conducted as a first step in the process to validate the method. In this SLV, 17 SPIFAN matrices representing a range of infant formula and adult nutritional products were evaluated for their amino acid content. Results: The analytical range was found to be within the needs for all products; some may require a dilution. Evaluation of trueness performed on Standard Reference Material 1849a (Infant/Adult Nutritional Formula) showed all compounds met the SMPR theoretical value, with exceptions for threonine and tyrosine. These may have a bias for the National Institute of Standards and Technology (NIST) data, depending on hydrolysis used in the determination of the NIST certificate of analysis. Conclusions: Based on the results of this SLV, this method met the SMPR and was approved as a First Action method by the AOAC Expert Review Panel on Nutrient Methods on August 28, 2018.

Total Amino Acids by UHPLC-UV in Infant Formulas and Adult Nutritionals, First Action 2018.06.

Background: An acid hydrolysis ultrahigh-performance LC-UV method was evaluated for the determination of total amino acids in infant formula and adult/pediatric nutritional formula. Objective: It was assessed for compliance against AOAC INTERNATIONAL Standard Method Performance Requirements (SMPR®) established by the Stakeholder Panel for Infant Formula and Adult Nutritionals (SPIFAN). Methods: A single-laboratory validation (SLV) study was conducted as a first step in the process to validate the method. In this SLV, 17 SPIFAN matrices representing a range of infant formula and adult nutritional products were evaluated for their amino acid content. Results: The analytical range was found to be within the needs for all products; some may require a dilution. Evaluation of trueness performed on Standard Reference Material 1849a (Infant/Adult Nutritional Formula) showed all compounds met the SMPR theoretical value, with exceptions for threonine and tyrosine. These may have a bias for the National Institute of Standards and Technology (NIST) data, depending on hydrolysis used in the determination of the NIST certificate of analysis. Conclusions: Based on the results of this SLV, this method met the SMPR and was approved as a First Action method by the AOAC Expert Review Panel on Nutrient Methods on August 28, 2018.

Quantitative Determination of Total Amino Acids Based on Surface-Enhanced Raman Scattering and Ninhydrin Derivatization.

In the present study, we propose a simple and sensitive method for the determination of total amino acids without any separation steps. The procedure described here is based on the ninhydrin derivatization reaction with amino acids, followed by surface-enhanced Raman scattering (SERS) measurements of the producing mixtures. A good linear correlation of excess ninhydrin SERS signals and the log values of the total amino acids concentrations is obtained; the detection limit of the method is 4.3 × 10-9 mol L-1. The derivatization reaction is reliable and the whole experimental procedure is very simple. The sensitivity of the proposed protocol allows quantitative analysis of total amino acids at picomole levels without any separation procedures. On the basis of the conventional ninhydrin reaction, we put forward a simple SERS method for determining the total amino acids concentrations with high sensitivity, which is a promising way for routine detection.

EFEITO DA SOLUÇÃO DE HOAGLAND NO TEOR DE AMINOÁCIDOS TOTAIS E NA NODULAÇÃO DE LEUCENA

Plants of Leucaena leucocephala (Lam.) de Wit were evaluated for nodulation and nitrogenous compounds. The plants (n = 18) were grown on substrates of sand, in plastic tubes, in treatments with distilled water (control) and Hoagland solution for a period of five months. Growth evaluations (measures of average height and counted the number of leaves, number of active nodes) and determination of total amino acids were performed. Data were subjected to analysis of variance with 95% probability (Tukey 5%).There was no difference in stem growth and leaf production among treatments. However, the number of nodules was higher in plants treated with distilled water. There was no difference in the content of free amino acids between treatments. We conclude that although the growth in acid soils is lower, this factor does not interfere with the content of amino acids and the formation of nodules.

Some observations on the automation by flow injection analysis of the spectrophotometric determination of amino acids and proteins witho-phthalaldehyde

Automation by flow injection analysis with Spectrophotometric detection of the determination of total amino acids and proteins witho-phthalaldehyde is not straightforward. The use of spectrophotometry, instead of spectrofluorimetry, and of N-acetyl-L-cysteine, instead of the conventional mercaptoethanol is advantageous because of the lower variability of absorptivities with respect to fluorescence yields, and the larger stability of the derivatives. Under adequate working conditions and with leucine as reference, the procedure can be used for the evaluation of total amino acids. A similar procedure is proposed for the analysis of proteins in a sample. Limits of detection are ≈ 1 × 10−5M for amino acids, and ≈ 1 × 10−6M for proteins, respectively.

Segmental flow-injection analysis: device and applications

A segmental flow-injection system which possesses features of both flow-injection analysis (FIA) and continuous-flow analysis (CFA) has been built. The whole sample zone is segmented by only two air bubbles. A valve has been designed to inject the sample and the bubbles into the carrier stream in a quantitative way. The position of the segmentation can be accurately controlled and the amount of the air introduced is minimized (only 5% of the bubbles in CFA) so that the stability of flow-rate can be improved. In this system, longer residence times (10 min or more) and higher reaction temperatures (up to 95 °C) can be obtained without loss of peak height or loss of sampling frequency in comparison with FIA. Owing to the good reproducibility the determination can still be performed when the equilibrium stare is is not obtained. The determination of total amino acids in tea with ninhydrin reagent, ammonia in natural water with phenol-sodium hypochlorite reagent and trace amounts of Cu(II) and V(V) by means of catalytic spectrophotometry are given as examples.

Gas chromatographic determination of total amino acids and protein in sediments using the ninhydrin-CO2 reaction

A sensitive modification of the ninhydrin-CO2 method involving the gas chromatographic determination of the total protein and amino acid content of sediment is described. The method gives a linear response over the amino acid concentration range 10−5 M to 4 × 10−2 M. It can be used for whole sediment, hydrolysates and interstitial water. The performance of the method is compared with the fluorescamine method for primary amines.

Gas chromatographic determination of total amino acids and protein in sediments using the ninhydrin-CO2 reaction

Gas chromatographic determination of total amino acids and protein in sediments using the ninhydrin-CO2 reaction

A Simple Determination Method of Total Amino Acids in Tea

A colorimetric method for the simple determination of total amino acids in tea based on the reaction with ninhydrin was investigated.The method was as follows : A weiged tea powder sample (100mg) was infused by hot water (20ml) in test tube for 25 minutes, and then polychlar AT (300mg) was added to the infusion. After 15 minutes the infusion was filtrated. To an availably diluted filtrate (5ml) was added ninhydrin reagent (1ml). The mixed solution was heated in boiling water bath for 20 minutes and was allowed to stand at room temperature 30 minutes, The intesity of the color of the solution was determined using wave length 560nm.Amount of total amino acids was calculated from the calibration curve made by simultaneously measured standard amino acids solutions.The relative standard deviation of this method was 5--10%. A high correlation (r=0.954) was observd between the total amino acids content of this method and the sum of each amino acid content by an automatic amino acids analyzer.

An automated fluorescence method for the determination of total amino acids in natural waters

An automated procedure, with o-phthaldialdehyde as a fluorogenic reagent for the determination of total α-amino acids in natural waters is given. The response of different amino acids, dipeptides and amino sugars has been tested as well as the interference of other nitrogen-containing substances. The method is well suited to determinations of the amino acid content in the range 0.05–15 μM with an analysis rate of 20 samples per hour.

An Automated Procedure for the Determination of Total Amino Acids and its Application to the Analysis of Tobacco

AbstractAn automated procedure for the determination of total alpha-amino acids in aqueous solution has been developed which utilizes the Technicon Auto Analyser I. The procedure is based in part on a manual method proposed by Van Slyke wherein the CO

A Quantitative Determination of Amino Acids in the Tea Leaves (Part 2)

A simple determination of total amino acids in tea leaves was investigated by ninhydrin method.The method was as follows : Sample solution prepared from 1g. of dried tea leaves by extraction with hot water is treated with the routine method of basic lead acetate. This solution is made to 100 ml. with water, after removed Pb with H2S. Take 0.25 ml. of sample solution, add 0.12ml. of pH 8 phosphate buffer solution and 0.1 ml. of ninhydrin solution to a test tube. Heat the mixed solution in a boiling water bath continuously 10 minutes. Make to 10 ml. with water, cool, and measure the absorbancy of the coloured solution at 570mμ with a spectrophotometer. Amount of total amino acids was calculated from the measured absorbancy by the calibration curve of theanine.The coefficents of variation of this method were 4.70-4.90%. A high correlation (r=0.980) was observed between the total amino acids content of this method and the sum of each amino acid content by an automatic amino acids analyzer.

Effects of Chemical Preservatives and Storage on Constituents Used to Characterize Lemon Juice

Abstract The effects of sulfur dioxide, sodium benzoate, and potassium sorbate preservatives on the analytical methods for chemically characterizing lemon juice were studied. None of the preservatives had any effects on the analyses for total acidity as citric acid, the l-malic acid, the UV absorbance at the 330 m/x peak (referred to as the total phenolics), or the formol determination of total amino acids (after expelling the S02 by boiling 1 min). The study was continued over storage periods of up to 17 weeks at room temperature and 6 weeks at 30 °C. The constituents measured remained relatively stable except for some small but statistically significant changes that were apparently a function of both the juice and, in the case of the total phenolics, the preservative used. For practical applications, the changes did not affect the multiple regression approach to the chemical characterization of lemon juice