Fast and sensitive method for phosphorus determination in dairy products

The spectrophotometric molybdenum blue method for phosphorus determination was adapted to a multiwell plate format. The method was sensitive and allowed for the simultaneous determination of phosphorus in many samples. It was cheap and eco-friendly due to application of small volumes of reagents and, therefore, it meets the requirements for “green” or sustainable chemistry. The method’s limit of detection (LOD) is 0.37 μg/mL and its limit of quantification (LOQ) is 1.13 μg/mL. Its linearity is up to 30 μg of phosphorus/mL. The method was applied for the determination of phosphorus in 65 dairy products (yogurts, yogurt drinks, buttermilks, kefirs and homogenized cheeses) of strawberry, peach, forest fruits, vanilla and other flavours. The phosphorus content was 143–226 mg/100 g in flavoured yogurts, 78–204 mg/100 g in yogurt drinks, 89–218 mg/100 g in kefirs, around 195 mg/100 g in buttermilks, and 165–277 mg/100 g in homogenized cheeses. The presented method can be used in the routine quantitative analysis of the total phosphorus content in dairy products.

Total phosphorus determination in eutrophic tropical river sediments by laser-induced breakdown spectroscopy techniques

Total phosphorus (TP) in sediments is an important chemical variable in the study of the extent of eutrophication in water bodies.

Total Phosphorus Determination in Soils Using Laser-Induced Breakdown Spectroscopy: Evaluating Different Sources of Matrix Effects

Laser-induced breakdown spectroscopy (LIBS) is a potential alternative to wet chemical methods for total soil phosphorus determination, but matrix effects related to physical and chemical sample properties need to be further understood. The aim of this study was to explore matrix effects linked to particle size distribution and chemical form of phosphorus on LIBS response and the ability of LIBS to predict total phosphorus in a range of different soil types. Univariate calibration curves were developed by spiking the soils with increasing doses of phosphorus, and limits of detection for LIBS determined phosphorous (P) (LIBS-P) were calculated. Different particle size distributions in otherwise identical soils were obtained by four milling treatments and effects of chemical form of phosphorus were examined by spiking soils with identical amounts of phosphorus in different chemical compounds. The LIBS-P response showed a high correlation (R2 > 0.99) with total phosphorus for all soils. Yet, the sensitivity of LIBS differed significantly among soils, as the slope of the calibration curves increased with increasing sand content, resulting in estimated limits of detection of 10 mg kg−1 for the sandiest and 122 mg · kg−1 for the most clayey soils. These limits indicate that quantitative evaluation of total phosphorus in sandy and loamy sandy soils by LIBS is feasible, since they are lower than typical total phosphorus concentrations in soil. A given milling treatment created different particle size distributions depending on soil type, and consequently different LIBS-P results. Thus, procedures that specify the required degree of homogenization of soil samples prior to analysis are needed. Sieving after milling could be an option, but that should be tested. The soils spiked with Fe(III) phosphate, potassium phosphate and phytic acid had similar LIBS-P, except for soils with hydroxyapatite, which resulted in markedly lower response. These results suggested that matrix effects related to the chemical nature of phosphorus would be minor for non-calcareous soils in humid regions, where apatites comprise only a small fraction of total phosphorus. Strategies to overcome matrix effects related to particle size and content of apatite-phosphorus by combining multivariate models and soil type groupings should be further investigated.

REGIONAL FEATURES AND EVALUATION OF THE METHODS AIMED AT LABILE PHOSPHATES DETERMINATION IN THE SOIL OF NOVOSIBIRSK REGION

The paper summarizes the results of many-year research on applying the existing methods for determining labile phosphates aimed at evaluation of the phosphorus fertilizers effect. The standard methods of phosphorus determination according to Truog and Chirikov suggests extracting a large amount of hard-to-reach forms from the soil. The existing scales for determining the soil needs inside this element for crops do not allow to evaluate objectively the fertility of black soil in the Novosibirsk Region. The application of buffer mixtures, acid and salt extractants for the diagnosis of phosphorus nutrition of plants is discussed. The authors suggest to explore black soil according to the Nikolov method and the LAC- method. They characterize the actual reserves of available phosphorus in the soil. During the growing season, it is necessary to carry out operational diagnostics using Karpinsky–Zamyatina method. The method determines the degree of transition of phosphorus to the soil fluid and the presence of residual phosphates. The amount of energy required to extract phosphorus from soil compounds is suggested to be determined by the Scofield method. Its value depends on the absorption properties of the soil and is regional in nature. For all the methods studied the new scales for the supply of black soil in the Novosibirsk Region were proposed. These scales give opportunity to find out the appropriateness of applying phosphorus fertilizers and give a correct assessment during the study of the diagnosis of phosphorus nutrition of plants.