Search Results (39)

Hundreds of veterinary drugs are widely used in agricultural activities and continuously enter aquatic environments through various pathways, posing potential risks to ecosystem. Considering that sediments function both as sinks and sources of these contaminants, it is crucial to promptly and accurately acquire veterinary drug residue level in sediments. In this study, a highly effective analytical method for simultaneous determination of 103 veterinary drugs from 16 classes in sediments was developed using high-performance liquid chromatography–tandem mass spectrometry (HPLC-MS/MS). The extraction procedure was performed twice by ultrasound-assisted extraction with an acetonitrile-buffer mixture consisting of Na₂EDTA, Na₃PO₄·12H₂O, and Na₃C₆H₅O₇·2H₂O. The supernatant was cleaned using 500 mg/6 mL Oasis HLB solid-phase cartridges. The elution solutions were concentrated and redissolved in formic acid–methanol–water (0.1/20/79.9, v/v, FA-MeOH-H₂O) for detection. Results showed that all 103 target drugs exhibited good linearity with R² > 0.990 over a concentration range of 0.010 to 1000 μg·L⁻¹, and method detection limits (MDLs) ranged from 0.025 to 5 μg·kg⁻¹. The recoveries at three spiking levels (2, 5, and 10 times of the method quantification limits, MQLs) varied from 33% to 150%, 32% to 140%, and 40% to 140%, respectively, with relative standard deviations (RSDs, n = 3) of 0.7%~29%, 0.8%~23%, and 0.5%~20%. The matrix effects for all compounds ranged from –85% to 84% with 32 targets negligible, 51 moderate, and 20 significant. An isotope-labeled surrogate method was proposed for quantitation to effectively overcome matrix effects and improve accuracy with better recoveries of 60%~120% for 93 target drugs and RSDs (n = 3) all below 20%. This method was applied to determine 12 sediment samples collected from the Jiulong River, and 16 target drugs were detected in the concentrations range of 0.1~7.6 μg·kg⁻¹. The method is accurate, sensitive, and efficient, providing a powerful analytical tool for behavior and effect studies of multi-classed veterinary drug residue in sediment environments. Full article

Charge-free gaseous molecules labeled with deuterium ²H (D) atoms elute earlier than their protium-analogs ¹H (H) from most stationary GC phases. This effect is known as the chromatographic H/D isotope effect (hdIE_C) and can be calculated by dividing the retention times (t_R) of the protiated (t_R(H) ) to those of the deuterated (t_R(D)) analytes: hdIE_C = t_R(H)/t_R(D). Analytes labeled with ¹³C, ¹⁵N or ¹⁸O have almost identical retention times and lack a chromatographic isotope effect. Derivatives of cis- and trans-analytes such as cis- and trans-fatty acids also differ in their retention times. Analytes that contain trans-C=C-double bonds elute earlier in gas chromatography-mass spectrometry (GC-MS) than their cis-C=C-double bonds containing congeners. The chromatographic cis/trans-effect (ctE_C) can be calculated by dividing the retention times of the cis- by those of the trans-analytes: ctE_C = t_R(c)/t_R(t). In the present work, the hdIE_C and ctE_C values of endogenous and exogenous substances were calculated from previously reported GC-MS analyses and found to range each between 1.0009 and 1.0400. The examination suggests that the H/D-isotope effects and the cis/trans-effects observed in GC-MS are based on differences in the inter-molecular interaction strengths of the analyte derivatives with the stationary phase of GC columns. The deuterium atoms, being larger than the H atoms of the analytes, attenuate the interaction of the skeleton of the molecules with the GC stationary phase. The angulation of trans-analytes decreases the interaction of the skeleton of the molecules with the GC stationary phase, as only parts of the molecules are close enough to the GC stationary phase to interact. Other chromatographic effects caused by hydrogen (H) and fluorine (F) atoms and by stereo-isomerism are considered to be based on a similar mechanism due to the different orientation of the side chains. Full article

Background: Acute and chronic pre-traumatic cigarette smoke exposure increases morbidity and mortality after trauma and hemorrhage. In mice with a genetic deletion of the H₂S-producing enzyme cystathione-γ-lyase (CSE^−/−), providing exogenous H₂S using sodium thiosulfate (Na₂S₂O₃) improved organ function after chest trauma and hemorrhagic shock. Therefore, we evaluated the effect of Na₂S₂O₃ during resuscitation from blunt chest trauma and hemorrhagic shock on CSE^−/− mice with pre-traumatic cigarette smoke (CS) exposure. Since H₂S is well established as being able to modify energy metabolism, a specific focus was placed on whole-body metabolic pathways and mitochondrial respiratory activity. Methods: Following CS exposure, the CSE^−/− mice underwent anesthesia, surgical instrumentation, blunt chest trauma, hemorrhagic shock for over 1 h (target mean arterial pressure (MAP) ≈ 35 ± 5 mmHg), and resuscitation for up to 8 h comprising lung-protective mechanical ventilation, the re-transfusion of shed blood, fluid resuscitation, and continuous i.v. noradrenaline (NoA) to maintain an MAP ≥ 55 mmHg. At the start of the resuscitation, the mice randomly received either i.v. Na₂S₂O₃ (0.45 mg/g_bodyweight; n = 14) or the vehicle (NaCl 0.9%; n = 11). In addition to the hemodynamics, lung mechanics, gas exchange, acid–base status, and organ function, we quantified the parameters of carbohydrate, lipid, and protein metabolism using a primed continuous infusion of stable, non-radioactive, isotope-labeled substrates (gas chromatography/mass spectrometry) and the post-mortem tissue mitochondrial respiratory activity (“high-resolution respirometry”). Results: While the hemodynamics and NoA infusion rates did not differ, Na₂S₂O₃ was associated with a trend towards lower static lung compliance (p = 0.071) and arterial PO₂ (p = 0.089) at the end of the experiment. The direct, aerobic glucose oxidation rate was higher (p = 0.041) in the Na₂S₂O₃-treated mice, which resulted in lower glycemia levels (p = 0.050) and a higher whole-body CO₂ production rate (p = 0.065). The mitochondrial respiration in the heart, kidney, and liver tissue did not differ. While the kidney function was comparable, the Na₂S₂O₃-treated mice showed a trend towards a shorter survival time (p = 0.068). Conclusions: During resuscitation from blunt chest trauma and hemorrhagic shock in CSE^−/− mice with pre-traumatic CS exposure, Na₂S₂O₃ was associated with increased direct, aerobic glucose oxidation, suggesting a switch in energy metabolism towards preferential carbohydrate utilization. Nevertheless, treatment with Na₂S₂O₃ coincided with a trend towards worsened lung mechanics and gas exchange, and, ultimately, shorter survival. Full article

To further understand the influence of n-heptane on the ignition process of ammonia, an isotope labeling method was applied in the current investigation to decouple the influence of the chemical effect, the thermal effect, and the effect of O radical from the oxidation of n-heptane on the ignition delay times (IDTs) of ammonia. An analysis of the time evolution of fuel, analysis of the time evolution of temperature, rate of consumption and production (ROP) analysis, and sensitivity analysis were conducted to gain a further understanding of the mechanism of the influence of the chemical effect, the thermal effect, and the effect of O radical on the ignition of ammonia. The results showed that the negative temperature coefficient (NTC) behavior of n-heptane is mitigated by the blending of ammonia, and this mitigated effect of ammonia is mainly due to the chemical effect. The IDTs of ammonia under low and medium temperatures are significantly shortened by the chemical effect at a n-heptane mass fraction of 10%. The promoting effect of the chemical effect decreases when the n-heptane mass fraction increases. The time evolution of n-heptane for NC₇H₁₆/ND₃-G can be classified into three stages at 800 K, and the rapid consumption stage is mitigated by an increase in temperature. The rapid consumption stage is suppressed by the chemical effect of ammonia, while O radical has a promoting effect on the rapid consumption stage. The chemical effect will enhance the sensitivities of reactions associated with ammonia. As the n-heptane mass fraction increases, the sensitivities of reactions associated with n-heptane are enhanced. Correspondingly, the effect of reactions associated with ammonia is weakened. When the n-heptane mass fraction is 30%, only reactions related to n-heptane have a great influence on the ignition of ammonia/n-heptane fuel blends under the thermal effect + the effect of O radical or only the thermal effect. Full article

Τhyreostats (TSs) are veterinary drugs used in livestock farming for fattening. Their administration is banned in the European Union since 1981, and their monitoring for food quality and safety control requires sensitive and confirmatory methods. The present study describes the development and validation of a hydrophilic interaction liquid chromatography tandem mass spectrometry (HILIC-MS/MS) method for the simultaneous determination of 2-thiouracil (TU), 6-methyl-2-thiouracil (MTU), 6-propyl-2-thiouracil (PTU), 6-phenyl-2-thiouracil (PhTU), tapazole (TAP), and 2-mercaptobenzimidazole (MBI) in bovine muscle tissues. Investigation of the retention mechanism of the six analytes on the selected amide-based stationary phase showed that hydrophilic partition was the dominant interaction. The sample preparation included extraction with ACN/H₂O (80/20), followed by dispersive solid-phase extraction (d-SPE) with C18 sorbent and hexane partitioning. The method was validated according to European guidelines using internal standards, including isotopically labelled ones. The method’s LODs ranged between 2.8 ng g⁻¹ (6-phenyl-2-thiouracil) and 4.1 ng g⁻¹ (2-thiouracil). Application of the proposed method to 48 bovine tissue samples showed non-detectable results. Full article

Reclaimed water (RW), as a reliable and renewable secondary water source, has become a crucial strategy for many countries to supplement agricultural water usage and alleviate water scarcity. However, despite the increasing use of RW, there has been limited research on the factors affecting soil nitrous oxide (${\mathrm{N}}_2\mathrm{O}$) emissions under RW irrigation. Understanding these factors is essential for guiding RW irrigation practices and controlling greenhouse gas emissions. This research, conducted from 2014 to 2015, includes field experiments designed to systematically assess the effects of soil chemistry properties and temperature on soil ${\mathrm{N}}_2\mathrm{O}$ emissions under RW irrigation. Subsequent to these field studies, soil samples were collected for ¹⁵N isotope trials to examine the impact of RW on the soil ${\mathrm{N}}_2\mathrm{O}$ production process, including autotrophic nitrification, heterotrophic nitrification, and denitrification. The results showed that RW irrigation influenced soil ${\mathrm{N}}_2\mathrm{O}$ emissions by affecting soil pH, but not through changes in soil total nitrogen (TN) or soil organic carbon (SOC) content. Moreover, compared to groundwater (UW) irrigation, RW irrigation significantly reduced the temperature sensitivity of soil ${\mathrm{N}}_2\mathrm{O}$ emissions. The ¹⁵N isotope labeling trial indicated that autotrophic nitrification was the primary pathway for soil ${\mathrm{N}}_2\mathrm{O}$ production under RW irrigation, contributing 60.46%—significantly higher than that observed with UW irrigation. Primary treated sewage (PW) significantly increased soil ${\mathrm{N}}_2\mathrm{O}$ emissions through the heterotrophic nitrification process compared to RW, with contributions rising from 11.31% to 13.23%. Additionally, RW, compared to UW, significantly increased the copy numbers of soil nitrification genes (ammonia-oxidizing archaea [AOA-amoA]) and denitrification genes (nitrite reductase [nirK and nirS]). Therefore, it is important to appropriately control the nitrification process and balance soil pH to manage soil ${\mathrm{N}}_2\mathrm{O}$ emissions under RW irrigation. Full article

Verifying the geographical origin of soybeans (Glycine max [Linn.] Merr.) is a major challenge as there is little available information regarding non-parametric statistical origin approaches for Chinese domestic and imported soybeans. Commercially procured soybean samples from China (n = 33) and soybeans imported from Brazil (n = 90), the United States of America (n = 6), and Argentina (n = 27) were collected to characterize different producing origins using stable isotopes (δ²H, δ¹⁸O, δ¹⁵N, δ¹³C, and δ³⁴S), non-metallic element content (% N, % C, and % S), and 23 mineral elements. Chemometric techniques such as principal component analysis (PCA), linear discriminant analysis (LDA), and BP–artificial neural network (BP-ANN) were applied to classify each origin profile. The feasibility of stable isotopes and elemental analysis combined with chemometrics as a discrimination tool to determine the geographical origin of soybeans was evaluated, and origin traceability models were developed. A PCA model indicated that origin discriminant separation was possible between the four soybean origins. Soybean mineral element content was found to be more indicative of origin than stable isotopes or non-metallic element contents. A comparison of two chemometric discriminant models, LDA and BP-ANN, showed both achieved an overall accuracy of 100% for testing and training sets when using a combined isotope and elemental approach. Our findings elucidate the importance of a combined approach in developing a reliable origin labeling method for domestic and imported soybeans in China. Full article

The CO₂ electrochemical reduction reaction (CO₂RR) is one of the most promising methods to reduce carbon dioxide emissions and store energy. At the same time, the pathways of CO₂ reduction reaction are diverse and the products are abundant. Converting carbon dioxide to C₂₊ products, a critical feedstock, requires a C–C coupling step with the transfer of more than 10 electrons per molecule and, hence, is kinetically sluggish. The production of some key adsorptions is conducive to the formation of C₂₊ products. In this work, we used in situ techniques to figure out the reason why hexagonal-close-packed (hcp) Co nanosheets (NSs) have high activity in CO₂RR to ethanal. According to the in situ Raman spectra, the high local pH environment on the catalyst surface is favorable for CO₂RR. The high pH at low potentials not only suppresses the competing hydrogen evolution reaction but also stimulates the production of COCO* intermediate. The isotopic labeling experiment in differential electrochemical mass spectrometry (DEMS) provides a possible sequence of the products. The ¹³CO is generated when we replace ¹²CO₂ with ¹³CO₂, which identifies the origin of the products. Besides, in situ electrochemical impedance spectroscopy (EIS) shows that the hcp Co at −0.4 V vs. RHE boosts the H₂O dissociation and proton transfer, feeding sufficient H* for CO₂ to *COOH. In the end, by analyzing the transmission electronic microscopy (TEM), we find that the Co (002) plane may be beneficial to the conversion of CO₂ and the adsorption of intermediates. Full article

Mass spectrometry has been an essential technique for the investigation of the metabolic pathways of living organisms since its appearance at the beginning of the 20th century. Due to its capability to resolve isotopically labeled species, it can be applied together with stable isotope tracers to reveal the transformation of particular biologically relevant molecules. However, low-resolution techniques, which were used for decades, had limited capabilities for untargeted metabolomics, especially when a large number of compounds are labelled simultaneously. Such untargeted studies may provide new information about metabolism and can be performed with high-resolution mass spectrometry. Here, we demonstrate the capabilities of high-resolution mass spectrometry to obtain insights on the metabolism of a model plant, Lepidium sativum, germinated in D₂O and H₂¹⁸O-enriched media. In particular, we demonstrated that in vivo labeling with heavy water helps to identify if a compound is being synthesized at a particular stage of germination or if it originates from seed content, and tandem mass spectrometry allows us to highlight the substructures with incorporated isotope labels. Additionally, we found in vivo labeling useful to distinguish between isomeric compounds with identical fragmentation patterns due to the differences in their formation rates that can be compared by the extent of heavy atom incorporation. Full article

Bottled mineral waters originate from groundwater aquifers, their chemical composition being initially determined by geochemical water-rock interaction processes. The waters used for bottling originate from different parts of the hydrological cycle and have a unique hydro-geochemical fingerprint. As water moves through the water cycle, the isotopic composition of oxygen and hydrogen in the water molecule may change. Determining ¹⁸O and ²H can help to characterize the source of bottled water and the natural conditions of the parent water body, of the recharge area, and the influence of various processes during infiltration and water flow within the water body. Usually, the chemical composition is reported on the label of bottled waters, while stable isotopes data are often unreported and are sometimes available from scientific publications. Bottled waters from selected sites of Europe where chemical and stable isotopic composition were available have been considered and accompanying data reinterpreted. The available data have been reinterpreted by obtaining results comparable, within limitations, to traditional sampling and analytical procedures, demonstrating the usefulness of the adopted methodology in emergency cases. Therefore, the utilization of isotopic values of bottled waters should be limited to the observation of general trends in isotopic composition of feeding waters, while more local studies are advised for a better understanding of the hydro-geological circuits. Full article

The mixed ionic and electronic oxide LaNi_0.6Fe_0.4O_3−δ (LNF) is a promising ceramic cathode material for solid oxide fuel cells. Since the reaction rate of oxygen interaction with the cathode material is extremely important, the present work considers the oxygen exchange mechanism between O₂ and LNF oxide. The kinetic dependence of the oxygen/oxide interaction has been determined by two isotopic methods using ¹⁸O-labelled oxygen. The application of the isotope exchange with the gas phase equilibrium (IE-GPE) and the pulsed isotope exchange (PIE) has provided information over a wide range of temperatures (350–800 °C) and oxygen pressures (10–200 mbar), as each method has different applicability limits. Applying mathematical models to treat the kinetic relationships, the oxygen exchange rate (r_H, atom × cm⁻² × s⁻¹) and the diffusion coefficient (D, cm²/s) were calculated. The values of r_H and D depend on both temperature and oxygen pressure. The activation energy of the surface exchange rate is 0.73 ± 0.05 eV for the PIE method at 200 mbar, and 0.48 ± 0.02 eV for the IE-GPE method at 10–20 mbar; for the diffusion coefficient, the activation energy equals 0.62 ± 0.01 eV at 10–20 mbar for the IE-GPE method. Differences in the mechanism of oxygen exchange and diffusion on dense and powder samples are observed due to the different microstructure and surface morphology of the samples. The influence of oxygen pressure on the ratio of contributions of different exchange types to the total oxygen exchange rate is demonstrated. For the first time, the rate-determining step in the oxygen exchange process for LNF material has been identified. This paper discusses the reasons for the difference in the mechanisms of oxygen exchange and diffusion. Full article

Nitrite (O=N-O⁻, NO₂⁻) and nitrate (O=N(O)-O⁻, NO₃⁻) are ubiquitous in nature. In aerated aqueous solutions, nitrite is considered the major autoxidation product of nitric oxide (^●NO). ^●NO is an environmental gas but is also endogenously produced from the amino acid L-arginine by the catalytic action of ^●NO synthases. It is considered that the autoxidation of ^●NO in aqueous solutions and in O₂-containing gas phase proceeds via different neutral (e.g., O=N-O-N=O) and radical (e.g., ONOO^●) intermediates. In aqueous buffers, endogenous S-nitrosothiols (thionitrites, RSNO) from thiols (RSH) such as L-cysteine (i.e., S-nitroso-L-cysteine, CysSNO) and cysteine-containing peptides such as glutathione (GSH) (i.e., S-nitrosoglutathione, GSNO) may be formed during the autoxidation of ^●NO in the presence of thiols and dioxygen (e.g., GSH + O=N-O-N=O → GSNO + O=N-O⁻ + H⁺; pK_a^HONO, 3.24). The reaction products of thionitrites in aerated aqueous solutions may be different from those of ^●NO. This work describes in vitro GC-MS studies on the reactions of unlabeled (¹⁴NO₂⁻) and labeled nitrite (¹⁵NO₂⁻) and RSNO (RS¹⁵NO, RS¹⁵N¹⁸O) performed in pH-neutral aqueous buffers of phosphate or tris(hydroxyethylamine) prepared in unlabeled (H₂¹⁶O) or labeled H₂O (H₂¹⁸O). Unlabeled and stable-isotope-labeled nitrite and nitrate species were measured by gas chromatography–mass spectrometry (GC-MS) after derivatization with pentafluorobenzyl bromide and negative-ion chemical ionization. The study provides strong indication for the formation of O=N-O-N=O as an intermediate of ^●NO autoxidation in pH-neutral aqueous buffers. In high molar excess, HgCl₂ accelerates and increases RSNO hydrolysis to nitrite, thereby incorporating ¹⁸O from H₂¹⁸O into the SNO group. In aqueous buffers prepared in H₂¹⁸O, synthetic peroxynitrite (ONOO⁻) decomposes to nitrite without ¹⁸O incorporation, indicating water-independent decomposition of peroxynitrite to nitrite. Use of RS¹⁵NO and H₂¹⁸O in combination with GC-MS allows generation of definite results and elucidation of reaction mechanisms of oxidation of ^●NO and hydrolysis of RSNO. Full article

In terms of isotopic technologies, it is essential to be able to produce materials with an enriched isotopic abundance (i.e., a compound isotopic labelled with ²H, ¹³C, ⁶Li, ¹⁸O or ³⁷Cl), which is one that differs from natural abundance. The isotopic-labelled compounds can be used to study different natural processes (like compounds labelled with ²H, ¹³C, or ¹⁸O), or they can be used to produce other isotopes as in the case of ⁶Li, which can be used to produce ³H, or to produce LiH that acts like a protection shield against fast neutrons. At the same time, ⁷Li isotope can be used as a pH controller in nuclear reactors. The COLEX process, which is currently the only technology available to produce ⁶Li at industrial scale, has environmental drawbacks due to generation of Hg waste and vapours. Therefore, there is a need for new eco-friendly technologies for separation of ⁶Li. The separation factor of ⁶Li/⁷Li with chemical extraction methods in two liquid phases using crown ethers is comparable to that of COLEX method, but has the disadvantages of low distribution coefficient of Li and the loss of crown ethers during the extraction. Electrochemical separation of lithium isotopes through the difference in migration rates between ⁶Li and ⁷Li is one of the green and promising alternatives for the separation of lithium isotopes, but this methodology requires complicated experimental setup and optimisation. Displacement chromatography methods like ion exchange in different experimental configurations have been also applied to enrich ⁶Li with promising results. Besides separation methods, there is also a need for development of new analysis methods (ICP-MS, MC-ICP-MS, TIMS) for reliable determination of Li isotope ratios upon enrichment. Considering all the above-mentioned facts, this paper will try to emphasize the current trends in separation techniques of lithium isotopes by exposing all the chemical separation and spectrometric analysis methods, and highlighting their advantages and disadvantages. Full article

The effects of temperature, salinity, and illumination on the nitrite uptake rate of the microalgae–bacteria consortia of Oocystis borgei and Rhodopseudomonas palustris were investigated. The absorption rates of nitrite and the contribution rate of each component in the consortia under different temperatures (15, 20, 25, 30, 35 °C), illuminations (0, 15, 25, 35, 45 μmol·m⁻²·s⁻¹), and salinities (0, 5, 15, 25, 35‰) were determined by stable isotope labeling technique. The single and combined effects of three environmental factors on nitrite uptake by the microalgae–bacteria consortia were analyzed using single-factor and orthogonal experiments. The single-factor experiment showed that the microalgae–bacteria consortia could absorb nitrite efficiently when the temperature, salinity, and illumination were 20~30 °C, 0~15‰, and 25~45 μmol·m⁻²·s⁻¹, respectively, with the highest absorption rates were 2.086, 3.058, and 2.319 μg∙g⁻¹∙h⁻¹, respectively. The orthogonal experiment showed that the most efficient environmental conditions for nitrite uptake were 30 °C, 5‰ salinity, 35 μmol·m⁻²·s⁻¹ illumination, and the rate of nitrite uptake by the microalgae–bacteria consortia was 3.204 μg∙g⁻¹∙h⁻¹. The results showed that the nitrite uptake rate of the O. borgei–R. palustris consortia was most affected by temperature, followed by salinity, and least by illumination. Under the same conditions, the nitrite absorption capacity of the microalgae–bacteria consortia was greater than that of single bacteria or algae, and R. palustris played a major role in the nitrite absorption of the consortia. The O. borgei and R. palustris consortia still maintain high nitrite absorption efficiency when the environment changes greatly, which has broad application prospects in the regulation and improvement of water quality in shrimp culture. Full article

While the demand for Spirulina dietary supplements continues to grow, product inspection in terms of authenticity and safety remains limited. This study used the stable isotope ratios of light elements (C, N, S, H, and O) and the elemental composition to characterize Spirulina dietary supplements available on the Slovenian market. Forty-six samples were labelled as originating from the EU (1), non-EU (6), Hawaii (2), Italy (2), Japan (1), Portugal (2), Taiwan (3), India (4), and China (16), and nine products were without a declared origin. Stable isotope ratio median values were –23.9‰ (–26.0 to –21.8‰) for δ¹³C, 4.80‰ (1.30–8.02‰) for δ¹⁵N, 11.0‰ (6.79–12.7‰) for δ³⁴S, –173‰ (– 190 to –158‰) for δ²H, and 17.2‰ (15.8–18.8‰) for δ¹⁸O. Multivariate statistical analyses achieved a reliable differentiation of Hawaiian, Italian, and Portuguese (100%) samples and a good separation of Chinese samples, while the separation of Indian and Taiwanese samples was less successful, but still notable. The study showed that differences in isotopic and elemental composition are indicative of sample origins, cultivation and processing methods, and environmental conditions such that, when combined, they provide a promising tool for determining the authenticity of Spirulina products. Full article