Determination Of Total Nitrogen Research Articles

Simultaneous Determination of Chemical Oxygen Demand, Total Nitrogen, Ammonia, and Phosphate in Surface Water Based on a Multielectrode System.

A technique for monitoring chemical oxygen demand (COD), total nitrogen (TN), ammonia (N-NH4), and phosphate (P-PO4) in surface water with a targeted signal multielectrode system (Cu, Ir, Rh, Co(OH)2, and Zr(OH)4 electrodes) is proposed for the first time. Each water quality index is specifically detected by at least two electrodes with distinct selectivity sensing mechanisms. Cyclic voltammetry and electrochemical impedance measurements are employed for multidimensional signal acquisition, complemented by normalization and Least Absolute Shrinkage and Selection Operator (LASSO) for principal feature extraction and dimension reduction. Multiple linear regression (MLR), partial least-squares (PLS), and eXtreme Gradient Boosting (XGBoost) were employed to evaluate the established prediction model. The precisions of the multielectrode system are ±10%/±5 ppm of COD, ±10%/±0.2 ppm of TN, ±5%/±0.1 ppm of N-NH4, and ±5%/±0.01 ppm of P-PO4. The analysis time of the multielectrode system is reduced from hours to minutes compared with traditional analysis, without any sample pretreatment, facilitating continuous online monitoring in the field. The developed multielectrode system offers a feasible strategy for online in situ monitoring of surface water quality.

Determination of Soil Organic Matter and Total Nitrogen from Visible Near-Infrared Spectroscopy by Multivariate Models and Variable Selection Techniques

Determination of Soil Organic Matter and Total Nitrogen from Visible Near-Infrared Spectroscopy by Multivariate Models and Variable Selection Techniques

CRUDE PROTEIN CONTENT IN PIGEON PEA GRAIN LINES

Pigeon pea (Cajanus cajan (L.) Millspaugh) is a multipurpose legume, which can be used as a grain producer, fodder and soil improver. Its nutritional composition has high protein, on average 22%, characterizing a relevant species in several emerging countries. Although it is an important crop in semi-arid regions of other countries, in Brazil has been little used and studied, so that it is still considered a subsistence culture. The goal of the present study was to evaluate the protein content in 21 lines of pigeon pea, from the breeding program of Embrapa Semiárido, including the control variety ‘guandu Petrolina’. The experiments were conducted in Barbalha/CE, Petrolina/PE and Juazeiro/BA, years of 2019, 2020 and 2021, distributed in four environments, three under irrigated cultivation and one under rainfed cultivation. The experiments were arranged in plots with two planting lines measuring 2.4m x 2.5m, spaced between rows by 1.2m and between plants by 0.5m, with two plants per hole, using a randomized block design with three replications. The cultural treatments consisted of manual weeding, without any type of fertilization in the experimental area. The determination of total nitrogen and crude protein was performed using the Kjeldahl method. The genotype × environment interaction was highly significant (p<0.01) for protein content. There was no significant difference between the levels of protein under irrigated and rainfed cultivation. After joint analysis of variance among the four environments, the control cultivar 'Petrolina presented the highest average, with 24.60%. The lowest protein average was presented by treatment 17 (ICPL 900053 x Anagé), 20.12%. Lines 12 (ICPL 90053 x D2 Type), 9 (ICPL 90045 x ICPL 89027) and 19 (ICPL 89027 x D3 Type) expressed acceptable values for protein content, 22.35, 21.99 and 22.72%, respectively, associated with high productivity, broad adaptability and good predictability, showing great potential to be new cultivars to the Brazilian semiarid region.

Comparison of Multiple NIR Spectrometers for Detecting Low-Concentration Nitrogen-Based Adulteration in Protein Powders.

Protein adulteration is a common fraud in the food industry due to the high price of protein sources and their limited availability. Total nitrogen determination is the standard analytical technique for quality control, which is incapable of distinguishing between protein nitrogen and nitrogen from non-protein sources. Three benchtops and one handheld near-infrared spectrometer (NIRS) with different signal processing techniques (grating, Fourier transform, and MEM-micro-electro-mechanical system) were compared with detect adulteration in protein powders at low concentration levels. Whey, beef, and pea protein powders were mixed with a different combination and concentration of high nitrogen content compounds-namely melamine, urea, taurine, and glycine-resulting in a total of 819 samples. NIRS, combined with chemometric tools and various spectral preprocessing techniques, was used to predict adulterant concentrations, while the limit of detection (LOD) and limit of quantification (LOQ) were also assessed to further evaluate instrument performance. Out of all devices and measurement methods compared, the most accurate predictive models were built based on the dataset acquired with a grating benchtop spectrophotometer, reaching R2P values of 0.96 and proximating the 0.1% LOD for melamine and urea. Results imply the possibility of using NIRS combined with chemometrics as a generalized quality control tool for protein powders.

Combination of headspace single-drop microextraction with smartphone-based on-drop colorimetric detection for determination of ammonia and total nitrogen in environmental and food samples

In the present study, a simple, environmentally friendly and inexpensive analytical method was proposed based on the combination of headspace single-drop microextraction with smartphone-based on-drop colorimetric detection for determination of ammonia (free ammonia and ammonium ion) in environmental and food samples. This method was also coupled with micro Kjeldahl digestion for determining total nitrogen content (or protein) in foods. Ammonia was extracted into an aqueous microdrop containing o-phthalaldehyde (OPA)-Na2SO3 reagent, and simultaneously converted to a colored derivative (1-sulfonatoisoindole). The colored microdrop was directly imaged by smartphone camera as a detector, and the captured image was processed with a color recognition app for ammonia quantification. The influence of experimental variables on the sensitivity of this method was studied. The linear range of the method was achieved from 0.25 to 10 mg L−1 for ammonium with the detection limit of 0.07 mg L−1. The intraday and interday relative standard deviations were between 2.5 and 5.5 % at the concentration levels of 0.5 and 5 mg L−1. This method was satisfactorily applied to determining ammonia and total nitrogen in environmental and food samples with ammonia and total nitrogen recoveries in the range of 90–109 %. In comparison with the Berthelot and classical Kjeldahl methods, there was no considerable difference in accuracy between these methods and the present method.

Precise determination of the total nitrogen content in activated sludge by ultrasonic pre-treatment assisted wet method

ABSTRACT The study proposed a method for determining total nitrogen (TN) content in activated sludge by ultrasound pre-treatment assisted wet method. Based on the single-factor experiment, with the TN content as the response value, the response surface methodology was employed to examine the individual and interactive effects of three factors: the dilution multiple of the sludge mixture, ultrasonic time, and ultrasonic power. At the same time, the physico-chemical parameters and the digestion–oxidation parameters were optimised. The results indicated that the optimal parameters were as follows; sludge dilution multiple of 225 times, stirring rate of 400 r/min, ultrasonic time of 22 minutes, ultrasonic power of 720 W, and optimal added volume of potassium persulfate at 8 mL with a digestion time of 40 minutes. The relative standard deviation (RSD) for the parallel determination of TN in sludge samples using ultrasonic pre-treatment assisted wet method was ≤2.77%, with a spike recovery rate of 98.49–101.43%. The method, ultrasonic pre-treatment assisted wet method to determine TN concentration in activated sludge, was simpler to operate, more accurate.

Effects of Bacillus subtilis and Lactobacillus plantarum probiotics on the Litopenaeus vannamei growth performance, hemolymph factors, and physicochemical parameters

The present study aimed to investigate the effects of two probiotics, namely Bacillus subtilis (ATCC 6633) and Lactobacillus plantarum (RITCC 1273), on the postlarvae of Litopenaeus vannamei (between 0.5 and 1.5 g). Different combinations of B. subtilis and L. plantarum in two concentrations of B. subtilis (B1 (106 CFU.mL−1) and B2 (3 ×106 CFU.mL−1)) and two concentrations of L. plantarum (L1 (105 CFU.mL−1) and L2 (3 ×105 CFU.mL−1)), were added to the water in five treatment groups (T1 = L1 × B2, T2 = L1 × B1, T3 = L2 × B2, T4 = L2 × B1, and Control). The objective was to assess probiotics' impact on hemolymph indices, salinity stress, growth rate, and productive parameters of Litopenaeus vannamei. After farming shrimps for 60 days under modified conditions using probiotics, the shrimps were harvested and transferred to store at − 18 ℃ for 60 days, and the effects of probiotics on the shelf-life of shrimps under freezing preservation were determined. Nutritional values, pH, Thiobarbituric acid reactive substances (TBARS), Total volatile nitrogen determination (TVB-N), Water holding capacity (WHC), drip loss, and texture profile were assessed. The results indicated that water quality remained relatively stable throughout the aquaculture phase, with no significant (P > 0.05) alterations observed in pH, ammonia nitrogen, nitrate-nitrogen, and nitrite-nitrogen levels. The growth performance tests revealed that treatment T1 (L1 × B2) exhibited the highest weight gain (WG), survival rate (SR), specific growth rate (SGR), and relative feed conversion efficiency (RFC). Conversely, T4 (L2 × B1) displayed significantly lower levels of triglycerides (274.51 ± 17 mg/dL) and higher levels of cholesterol (3581.61 ± 1222 mg/dL). Regarding shrimp storage, T4 demonstrated the best performance with the highest WHC (31.9 ± 7.8%) and lowest drip loss (4.7 ± 0.4%) among the treatments on day 60.

Droplet-based luminescent sensor supported onto hydrophobic cellulose substrate for assessing fish freshness following smartphone readout.

In this work, two sensitive droplet-based luminescent assays with smartphone readout for the determination of trimethylamine nitrogen (TMA-N) and total volatile basic nitrogen (TVB-N) are reported. Both assays exploit the luminescence quenching of copper nanoclusters (CuNCs) produced when exposed to volatile nitrogen bases. In addition, hydrophobic-based cellulose substrates demonstrated their suitability as holders for both in-drop volatile enrichment and subsequent smartphone-based digitization of the enriched colloidal solution of CuNCs. Under optimal conditions, enrichment factors of 181 and 153 were obtained with the reported assays for TMA-N and TVB-N, respectively, leading to methodological LODs of 0.11mg/100g and 0.27mg/100g for TMA-N and TVB-N, respectively. The repeatability, expressed as RSD, was 5.2% and 5.6% for TMA-N and TVB-N, respectively (N=8). The reported luminescent assays were successfully applied to the analysis of fish samples, showing statistically comparable results to those obtained with the reference methods of analysis.

Intelligent and Active Packaging System Application in Evaluating and Maintaining the Tuna (Thunnus Sp.) Fillets’ Quality at Cold Temperature

This study developed intelligent and active packaging combined for tuna fillets. The purposes of this study were to determine the colour change of packaging indicator labels and the effectiveness of edible coatings (citronella oil concentrations of 0%, 0.5%, and 1%), as well as to establish a correlation between the colour analysis values of intelligent indicator and observed spoilage criteria of tuna stored at refrigerated temperatures (4±1°C). The parameters tested included the determination of Total Volatile Bases Nitrogen, Total Plate Count, pH, and sensory analysis. The test was carried out every three days for 18 days, with two replications. The findings indicated that the intelligent indicator label (Bromothymol blue + Methyl Red (1:1)) changed colour from deep red to yellow and then green. Edible coating with 0.5% citronella oil gave the best result in this study. The correlation between the colour analysis of the intelligent indicators and the parameters of the fish spoilage test is positive, suggesting a consistent trend pattern in determining the degree of decay in tuna fillets. Correlation coefficient values vary from 0.98 to 0.99, showing a significant correlation. The combination of intelligent and active packaging in a single packaging system allows for monitoring tuna's quality while increasing its shelf life.

Portable beef-freshness detection platform based on colorimetric sensor array technology and bionic algorithms for total volatile basic nitrogen (TVB-N) determination

Portable beef-freshness detection platform based on colorimetric sensor array technology and bionic algorithms for total volatile basic nitrogen (TVB-N) determination

Improving Nutritional and Microbiological Properties of Monterey Cheese Using Lactobacillus acidophilus

The study was conducted to produce healthy monterey cheese and it is physical and chemical properties were studied. In addition, microbiological tests were carried out by adding a therapeutic bacterium to cheese, Lb.acidophilus, and it was compared with the control treatment containing the standard cheese starter (Lactococcus lactis subsp lactis, Lactococcus lactissubsp. cremors). The ripening period was 90 days in anaerobic conditions at 15°C. The tests were conducted over three storage periods as follows: first day, 45 days, and 90 days. Chemical tests for the above treatments include : Determination of moisture, ash, total nitrogen, non-protein nitrogen, acidity, pH and fat. Whole cow’s milk has been used in the two treatments mentioned above. As for the microbial assays, they were as follows: the number of yeasts, molds, staph.aurues, E.coli, Survivability in cheese with storage and survivability in gastric juice were calculated for the proteolysis study, SEM and electrophoresis. Through this study, it was concluded that there are differences between the two treatments T1 and T2, where it is noted that the second treatment obtained higher values and that was in the examination of moisture, ash, acidity, pH, protein and NPN assay, while in the examination of carbohydrates the value of the first treatment was higher than the second treatment where it reached 1.33%, As for the preparation of therapeutic bacteria in Monterey cheese during storage, it reached 175×107 (CFU\\g) ; As for the viability of bacteria in the gastric juice, the number of bacteria reached T1 40 × 107 (CFU\\g), as for the second treatment, the number of bacteria reached 76 × 107 (CFU\\g).

Large-scale prediction of stream water quality using an interpretable deep learning approach

Deep learning methods, which have strong capabilities for mapping highly nonlinear relationships with acceptable calculation speed, have been increasingly applied for water quality prediction in recent studies. However, it is argued that the practicality of deep learning methods is limited due to the lack of physical mechanics to explain the prediction results of water quality changes. A knowledge gap exists in rationalizing the deep learning results for water quality predictions. To address this gap, an interpretable deep learning framework was established to predict the spatiotemporal variations of water quality parameters in a large spatial region. Mereological, land-use, and socioeconomic variables were adopted to predict the daily variations of stream water quality parameters across 138 sub-catchments in a total of over 575,250 km2 in southern China. The coefficients of determination of chemical oxygen demand (COD), total phosphorus (TP), and total nitrogen (TN) predictions were over 0.80, suggesting a satisfactory prediction performance. The model performance in terms of prediction accuracy could be improved by involving land-use and socioeconomic predictors in addition to hydrological variables. The SHapley Additive exPlanations method used in this study was demonstrated to be effective for interpreting the prediction results by identifying the significant variables and reasoning their influencing directions on the variation of each water quality parameter. The air temperature, proportion of forest area, grain production, population density, and proportion of urban area in each sub-catchment as well as the accumulated rainfall within the previous 3 days were identified as the most significant variables affecting the variations of dissolved oxygen, COD, ammoniacal nitrogen(NH3–N), TN, TP, and turbidity in the stream water in the case area, respectively.

Effect of some organic acids on spoilage and pathogenic bacteria in broiler carcasses

A Total of six groups of fresh broiler carcasses randomly collected from different poultry shops at Alexandria province. After examination of an untreated samples, the samples were classified into six groups, each group was represented by their muscle samples which were dipped in acid solutions as follows; the 1st group was dipped in 1% lactic acid solution v/v for five min., the 2nd group was dipped in 2% lactic acid solution v/v for five min., the 3rd group was dipped in 1% acetic acid solution v/v for five min., the 4th group was dipped in 2% acetic acid solution v/v for five min., the 5th group was dipped in 1% mixture of lactic and acetic acids v/v for five min. and the 6th group was dipped in 2% mixture of lactic and acetic acids v/v for five min. Determination of spoilage markers including determination of pH and total volatile nitrogen (TVN) was performed beside determination of aerobic plate count (APC), psychrophilic bacteria count and Enterobacteriaceae count. The inhibitory effect of lactic acid and acetic acid on microbial population has long been used to preserve food from spoilage, while much of the effect can be accounted for pH and temperature of storage. Immersion of the examined samples with 1, 2 % (lactic, acetic acids). chilled for 1, 2, 4, 6, 8, 10 and 12 days resulted in population reductions of aerobic bacteria, psychrophilic and Enterobacteriaceae. Effect of organic acids as lactic acid, acetic acid and mixture of lactic and acetic acids are mainly affecting growth of microorganisms mainly by lowering of pH and increase acidity of media. The acids have effect until 10 days of storage at chilling condition in case of 1% concentration, but its effect reach to 12 days in case of 2% concentration.

Determination of total nitrogen and phosphorus in soil by ion chromatography with conductivity detector following persulfate digestion method

This study introduces a new method to determine both TP and TN in one process, reducing the analytical cost and time. During this procedure, soil samples were digested in alkaline potassium persulfate (K2S2O8) at 150 °C for two hours in a reactor to convert organic N (including NH3/NH4+) and P species to the highest oxidation states NO3-, PO43-. After that, H2O2 removes the color of the digest, which could influence the efficiency of the analytical process. Finally, ions NO3- and PO43- were separated on the anion-exchange column and quantified by a conductivity detector. According to the spiked samples, which were made by mixing Bovine serum albumin (BSA) with organic nitrogen and triphenyl phosphate containing organic phosphorus with real soil matrix, the recovery of TN and TP was 85% and 97%, respectively. Both TN and TP linear concentration ranges were between 0.50 and 50 µg.mL-1. The results of relative standard deviation and limit of detection for TN were from 4.2%, and 0.31 mg.kg-1; and for TP were from 3.5%, and 0.25 mg.kg-1.

Determination of Total Ammonia Nitrogen by Gas-Diffusion Flow Injection Analysis (GD-FIA)-Spectrophotometry using Minnieroot Flower (Ruellia tuberosa) as Natural Reagent

Total ammonia nitrogen (TAN) is a pollutant agent found in water and generated from the metabolisms of living organisms and the decomposition of organic matter. This research aims to develop an efficient, low-cost, and environmentally friendly TAN analysis method. The principle of this method is based on the reaction of TAN injected in the donor stream with NaOH to form alkaline gaseous ammonia. The gaseous ammonia diffuses through a hydrophobic membrane into an acceptor stream containing Ruellia tuberosa extract. The presence of NH3 gas in the acceptor stream changes the extract color from pinkish to green, which is monitored by spectrophotometer at 620 nm. This method was also validated based on linearity, selectivity, and accuracy. Under the obtained optimum conditions of 1 M NaOH, 5% extract, a 120 cm mixing coil, and a 200 µL sample volume, the proposed method showed excellent linearity at 10–1000 ppm (R2 = 0.993). The selectivity test result shows that this method was selective against sulfite and nitrite compounds up to 600 ppm with a % error value <10%. This method was applied to measure the total ammonia concentration in agricultural water, and satisfying results were shown by high recoveries of 95.03%–98.84%.

Effects of Eco-Friendly Product Application and Sustainable Agricultural Management Practices on Soil Properties and Phytosanitary Condition of Winter Wheat Crops

Despite the eco-political difficulties that accompany the application of principles of the European Green Deal policy on agriculture in the current world crisis, the need of their implementation seems to be absolutely necessary. The practices recommended within the sustainable agriculture strategy include replacing traditional fertilizers and pesticides with eco-friendly preparations and optimizing the management of biomass produced on farms. The aim of the research was to determine the effect of eco-friendly preparations application combined with straw incorporation on the chemical and microbiological soil parameters and plant sanitary status of winter wheat. The soil analyses included the determination of total organic carbon (TOC) and total nitrogen (TN) content; mineral nitrogen (MN), phosphorus (P), potassium (K), and magnesium (Mg) content, and the pH value. The number of soil bacteria (B), actinobacteria (A), fungi (F), and the total number of microorganisms (TNM) were also analyzed. The application of Effective Microorganisms resulted in an increase in TOC and TN concentration. The influence of biostimulator Asahi was diversified. The beneficial effect of straw on TOC, TN, and K content and microbial growth was also observed. Despite a number of limitations, the potential benefits of application of eco-friendly preparations provide ample reasons to continue experiments with their use.

Evaluation of Uncertainty in Determination of Total Nitrogen in Seawater by Continuous Flow Method

Evaluation of Uncertainty in Determination of Total Nitrogen in Seawater by Continuous Flow Method

TOTAL NITROGEN DETERMINATION IN AMMONIACAL, AMIDIC AND NITRATE NITROGEN CONTAINING FERTILIZERS BY THE RANEY CATALYST METHOD

This paper presents the optimized conditions for the determination of total nitrogen in ammoniacal, amidic, and nitrate nitrogen containing fertilizers by the Raney catalyst method using a Buchi K-436 speed digester and a Buchi K-360 distillation unit.

Determination of Total Volatile Basic Nitrogen (TVB-N) Content in Beef Based on Airflow and Multipoint Laser Technique

Determination of Total Volatile Basic Nitrogen (TVB-N) Content in Beef Based on Airflow and Multipoint Laser Technique

Simplified Method for the Determination of Total Kjeldahl Nitrogen in Wastewater

The increase in total Kjeldahl nitrogen (TKN) concentrations is correlated with increases in cyanobacterial bloom biomass. Standard methods for the measurement of TKN are tedious, costly, time-consuming and involve the use of hazardous catalysts, such as mercury, high temperatures and significant amounts of toxic acids and bases. Since TKN plays a pivotal role in influencing algal blooms, there is an urgent need to develop simpler, safer and more accurate methods for the determination of TKN. The simplified TKN method (s-TKN™) developed by Hach® offers several advantages over the traditional TKN method, including eliminating the use of mercury, requiring low sample and reagent volumes and being cost-efficient and user-friendly. This communication presents preliminary results comparing the efficacy of s-TKN™ and the standard method, using commonly used primary standards and waste, estuarine and lake water matrices. For all primary standards analyzed, the s-TKN™ method exhibited good accuracy across a wide range of concentrations. The repeatability for the glycine–para-toluene sulfonic acid (Gly-PTSA) standard using the s-TKN™ method was 4.1% at the highest concentrations analyzed, with overall repeatability across concentrations comparable to the standard EPA method. For wastewater, estuarine and lake matrices, a good correlation (r2 = 0.9917) between the two methods and no statistical difference in the values (p &gt; 0.05) were obtained between two methods. Preliminary studies indicate that the s-TKN™ method has the potential to reduce the expenditure associated with the cost of analysis and has the potential to be a safer and cheaper alternative, while providing comparable analytical results to the standard method.