The photosynthetic oxygen evolution does not exclude the important role and contribution of bicarbonate photolysis

Photosynthesis is the most important biochemical reaction on Earth. It has co-evolved and developed with the Earth, driving the biogeochemical cycle of all elements on the planet and serving as the only chemical process in nature that can convert light energy into chemical energy. Some heavy oxygen isotopic(^(18)O) labeling experiments have"conclusively" demonstrated that the oxygen released by photosynthesis comes only from water and are written into textbooks. However, it is not difficult to find that bicarbonate has never been excluded from the direct substrate of photosynthesis from beginning to end during the history of photosynthesis research. No convincing mechanism can be used to explain photosynthetic oxygen evolution solely from water photolysis. The bicarbonate effect, the Dole effect, the thermodynamic convenience of bicarbonate photolysis, the crystal structure characteristics of photosystem Ⅱ, and the reinterpretation of heavy oxygen isotopic labeling(^(18)O)experiments all indicate that the photosynthetic oxygen evolution does not exclude the important role and contribution of bicarbonate photolysis. The recently proposed view that bicarbonate photolysis is the premise of water photolysis, bicarbonate photolysis and water photolysis work together with a 1:1(mol/mol) stoichiometric relationship, and the stoichiometric relationship between oxygen and carbon dioxide released during photosynthetic oxygen evolution is also 1:1, has excellent applicability and objectivity, which can logically and reasonably explain the precise coordination between light and dark reactions during photosynthesis, the bicarbonate effect, the Dole effect, the Kok cycle and the neutrality of water and carbon in nature.This is of great significance for constructing the bionic artificial photosynthetic reactors and scientifically answering the question of the source of elemental stoichiometric relationships in nature.

A cascade of in situ conversion of bicarbonate to CO_(2) and CO_(2) electroreduction in a flow cell with a Ni-N-S catalyst

Combination of CO_(2) capture using inorganic alkali with subsequently electrochemical conversion of the resultant HCO_(3)^(-)to high-value chemicals is a promising route of low cost and high efficiency.The electrochemical reduction of HCO_(3)^(-)is challenging due to the inaccessible of negatively charged molecular groups to the electrode surface.Herein,we adopt a comprehensive strategy to tackle this challenge,i.e.,cascade of in situ chemical conversion of HCO_(3)^(-)to CO_(2) and CO_(2) electrochemical reduction in a flow cell.With a tailored Ni-N-S single atom catalyst(SACs),where sulfur(S)atoms located in the second shell of Ni center,the CO_(2)electroreduction(CO_(2)ER)to CO is boosted.The experimental results and density functional theory(DFT)calculations reveal that the introduction of S increases the p electron density of N atoms near Ni atom,thereby stabilizing^(*)H over N and boosting the first proton coupled electron transfer process of CO_(2)ER,i.e.,^(*)+e^(-)+^(*)H+^(*)CO_(2)→^(*)COOH.As a result,the obtained catalyst exhibits a high faradaic efficiency(FE_(CO)~98%)and a low overpotential of 425 mV for CO production as well as a superior turnover frequency(TOF)of 47397 h^(-1),outcompeting most of the reported Ni SACs.More importantly,an extremely high FECOof 90%is achieved at 50 mA cm^(-2)in the designed membrane electrode assembly(MEA)cascade electrolyzer fed with liquid bicarbonate.This work not only highlights the significant role of the second coordination on the first coordination shell of the central metal for CO_(2)ER,but also provides an alternative and feasible strategy to realize the electrochemical conversion of HCO_(3)^(-)to high-value chemicals.

New method of local adjuvant therapy with bicarbonate Ringer’s solution for tumoral calcinosis: A case report

BACKGROUND Tumoral calcinosis is a condition characterized by deposits of calcium phosphate crystals in extra-articular soft tissues,occurring in hemodialysis patients.Calcium phosphate crystals are mainly composed of hydroxyapatite,which is highly infilt-rative to tissues,thus making complete resection difficult.An adjuvant method to remove or resolve the residual crystals during the operation is necessary.CASE SUMMARY A bicarbonate Ringer’s solution with bicarbonate ions(28 mEq/L)was used as the adjuvant.After resecting calcium phosphate deposits of tumoral calcinosis as much as possible,while filling with the solution,residual calcium phosphate deposits at the pseudocyst wall can be gently scraped by fingers or gauze in the operative field.A 49-year-old female undergoing hemodialysis for 15 years had swelling with calcium deposition for 2 years in the shoulders,bilateral hip joints,and the right foot.A shoulder lesion was resected,but the calcification remained and early re-deposition was observed.Considering the difficulty of a complete rection,we devised a bicarbonate dissolution method and excised the foot lesion.After resection of the calcified material,the residual calcified material was washed away with bicarbonate Ringer’s solution.CONCLUSION The bicarbonate dissolution method is a new,simple,and effective treatment for tumoral calcinosis in hemodialysis patients.

Combined effect of bicarbonate and water in photosynthetic oxygen evolution and carbon neutrality

Carbon neutrality is widely concerned and highly valued by many countries.Biosphere has always maintained the balance between oxidized organic substances and assimilated organic matter,resulting in netzero carbon dioxide(CO_(2)) emissions and maintaining its own carbon neutrality.Nature has set a good example for human beings to coordinate oxygen(O_(2)) balance and CO_(2)balance,and achieve carbon neutrality.How does photosynthetic oxygen evolution initiate carbon and water neutrality?My synthesis shows that photo system Ⅱ functions as carbonic anhydrase to catalyze the reaction of CO_(2)hydration under physiological conditions,and CO_(2)hydration coupled with chemical equilibrium,H^(+)+HCO_(3)^(-)→1/2O_(2)+2e^(-)+2H^(+)+CO_(2),occurs in a photosystem Ⅱ corecomplex.Meanwhile,I focused on the revisiting of four classical heavy oxygen(O^(18)) labeling experiments and found that bicarbonate can promote photo synthetic oxygen evolution,and that photo synthetic oxygen evolution can alternately come from bicarbonate and water,not only water.Bicarbonate photolysis and water photolysis account for half of the photo synthetic oxygen evolution respectively,which can well explain the bicarbonate effect,Dole effect and plants’ environmental adaptability.Photosynthetic oxygen evolution initiated the journey of water metabolism and carbon metabolism in nature,which led to the coupling as 1:1(mol/mol) stoichiometric relationship between the reduction of CO_(2)and oxidation of organic carbon,coordinated the evolution of the atmosphere,hydrosphere,lithosphere and biosphere,and realized "carbon neutrality" in the whole Earth system.

Bicarbonate activation of hydrogen peroxide: A new emerging technology for wastewater treatment

The serious limitations of available technologies for decontamination of wastewater have compelled researchers to search for alternative solutions. Catalytic treatment with hydrogen peroxide, which appears to be one of the most efficient treatment systems, is able to degrade various organics with the help of powerful ·OH radicals. This review focuses on recent progress in the use of bicarbonate activated hydrogen peroxide for wastewater treatment. The introduction of bicarbonate to pollutant treatment has led to appreciable improvements, not only in process efficiency, but also in process stability. This review describes in detail the applications of this process in homogeneous and heterogeneous systems. The enhanced degradation, limited or lack of leaching during heterogeneous degradation, and prolonged catalysts stability during degradation are salient features of this system. This review provides readers with new knowledge regarding bicarbonate, including the fact that it does not always harm pollutant degradation, and can significantly benefit degradation under some conditions.

Cholangiocyte anion exchange and biliary bicarbonate excretion

Primary canalicular bile undergoes a process of fluidization and alkalinization along the biliary tract that is influenced by several factors including hormones, innervation/neuropeptides, and biliary constituents. The excretion of bicarbonate at both the canaliculi and the bile ducts is an important contributor to the generation of the so-called bile-salt independent flow. Bicarbonate is secreted from hepatocytes and cholangiocytes through parallel mechanisms which involve chloride efflux through activation of Cl- channels, and further bicarbonate secretion via AE2/SLC4A2-mediated Cl-/HCO3- exchange. Glucagon and secretin are two relevant hormones which seem to act very similarly in their target cells （hepatocytes for the former and cholangiocytes for the latter）. These hormones interact with their specific G protein-coupled receptors, causing increases in intracellular levels of cAMP and activation of cAMP-dependent Cl- and HCO3- secretory mechanisms. Both hepatocytes and cholangiocytes appear to have cAMP-responsive intracellular vesicles in which AE2/SLC4A2 colocalizes with cell specific Cl- channels （CFTR in cholangiocytes and not yet determined in hepatocytes） and aquaporins （AQP8 in hepatocytes and AQP1 in cholangiocytes）, cAMP-induced coordinated trafficking of these vesicles to either canalicular or cholangiocyte lumenal membranes and further exocytosis results in increased osmotic forces and passive movement of water with net bicarbonate-rich hydrocholeresis.

Passivation process of X80 pipeline steel in bicarbonate solutions

The passivation process of X80 pipeline steel in bicarbonate solutions was investigated using potentiodynamic, dynamic electro-chemical impedance spectroscopy （DEIS）, and Mott-Schottky measurements. The results show that the shape of polarization curves changes with concentration. The critical ＇passive＇ concentration is 0.009 mol/L for X80 pipeline steel in bicarbonate solutions. No anodic current peak exists in solutions when the concentration is lower than 0.009 mol/L, whereas there are one and two anodic current peaks when the concentration ranges from 0.009 to 0.05 mol/L and is higher than 0.1 mol/L, respectively. DEIS measurements show that there exist active dissolution range, transition range, pre-passive range, passive layer formation range, passive range, and trans-passive range for X80 pipeline steel in the 0.1 mol/L solutions. The results of DEIS measurements are in complete agreement with the potentiodynamic diagram. An equivalent circuit containing three sub-layers is used to explain the Nyquist plots in the passive range. Analyses are well made for explaining the corresponding fitted capacitance and impedance. The Mott-Schottky plots show that the passive film of X80 pipeline steel is an n-type semiconductor, and capacitance measurements are in good accordance with the results of DEIS experiment.

Stress corrosion cracking of X80 pipeline steel exposed to high pH solutions with different concentrations of bicarbonate

Susceptibilities to stress corrosion cracking （SCC） of X80 pipeline steel in high pH solutions with various concentrations of HC03 at a passive potential of-0.2 V vs. SCE were investigated by slow strain rate tensile （SSRT） test. The SCC mechanism and the effect of HC03 were discussed with the aid of electrochemical techniques. It is indicated that X80 steel shows enhunced susceptibility to SCC with the concentration of HCO3 increasing from 0.15 to 1.00 mol/L, and the susceptibility can be evaluated in terms of current density at -0.2 V vs. SCE. The SCC behavior is controlled by the dissolution-based mechanism in these circumstances. Increasing the concentration of HCO3 not only increases the risk of rupture of passive films but also promotes the anodic dissolution of crack tips. Besides, little susceptibility to SCC is found in dilute solution containing 0.05 mol/L HCO3 for X80 steel. This can be attributed to the inhibited repassivation of passive films, manifesting as a more intensive dissolution in the non-crack tip areas than at the crack tips.

Preparation of Fine Spherical Particle Sized Ceria by Precipitation Method with Ammonium Bicarbonate

Fine spherical particle sized ceria (CeO_2) was prepared by homogeneous precipitation method with ammonium bicarbonate as precipitant. The prepared CeO_2 has the primary particle size of 10～50 nm when calcined between 400～700 ℃ analyzed by XRD and the aggregated particle size is about 300 nm measured by LASER particle sizer. SEM, TG-DTA and Zeta-potential analyzer were employed individually to study the morphology and the formation of CeO_2 product. It was found that excess NH_4NO_3 can serve as an sphericallization agent to prepare spherical CeO_2 powder by precipitation method.

Effect of Zn deficiency and excessive bicarbonate on the allocation and exudation of organic acids in two Moraceae plants

The effect of zinc(Zn) deficiency and excessive bicarbonate on the allocation and exudation of organic acids in plant organs(root, stem, and leaf) and root exudates of two Moraceae plants(Broussonetia papyrifera and Morus alba) were investigated. Two Moraceae plants were hydroponically grown and cultured in nutrient solution in four different treatments with 0.02 mM Zn or no Zn,combined with no or 10 mM bicarbonate. The variations of organic acids in different plant organs were similar to those of root exudates in the four treatments except B. papyrifera, which was in a treatment that was a combination of 0.02 mM Zn and no bicarbonate. The response characteristics in the production, translocation, and allocation of organic acids in the plant organs and root exudates varied with species and treatments. Organic acids in plant organs and root exudates increased under Zn-deficient conditions,excessive bicarbonate, or both. An increase of organic acids in the leaves resulted in an increase of root-exuded organic acids. B. papyrifera translocated more oxalate and citrate from the roots to the rhizosphere than M. alba under the dual influence of 10 mM bicarbonate and Zn deficiency. Organic acids of leaves may be derived from dark respiration and photorespiration. By comparison, organic acids in stems, roots, and root exudates may be derived from dark respiration and organic acid translocation from the leaves. These results provide evidence for the selective adaptation of plants to environments with low Zn levels or high bicarbonate levels such as a karst ecosystem.

Use of sodium bicarbonate and blood gas monitoring in diabetic ketoacidosis: A review

Diabetic ketoacidosis(DKA) is a severe and toocommon complication of uncontrolled diabetes mellitus. Acidosis is one of the fundamental disruptions stemming from the disease process, the complications of which are potentially lethal. Hydration and insulin administration have been the cornerstones of DKA therapy; however, adjunctive treatments such as the use of sodium bicarbonate and protocols that include serial monitoring with blood gas analysis have been much more controversial. There is substantial literature available regarding the use of exogenous sodium bicarbonate in mild to moderately severe acidosis; the bulk of the data argue against significant benefit in important clinical outcomes and suggest possible adverse effects with the use of bicarbonate. However, there is scant data to support or refute the role of bicarbonate therapy in very severe acidosis. Arterial blood gas(ABG) assessment is an element of some treatment protocols, including society guidelines, for DKA. We review the evidence supporting these recommendations. In addition, we review the data supporting some less cumbersome tests, including venous blood gas assessment and routine chemistries. It remains unclear that measurement of blood gas pH, via arterial or venous sampling, impacts management of the patient substantially enough to warrant the testing, especially if sodium bicarbonate administration is not being considered. There are special circumstances when serial ABG monitoring and/or sodium bicarbonate infusion are necessary, which we also review. Additional studies are needed to determine the utility of these interventions in patients with severe DKA and pH less than 7.0.

Basic and clinical study of increased effect of partial anti-tumor agents by infusing sodium bicarbonate through target artery

Objective： To observe the influence of pH value on the proliferation of LAK cells and on the killing effect of rlL-2, IFN-α2b, TNF-α, LAK cells and doxorubicin on malignant tumor cells, and investigate the possibility of increasing the efficacy of rlL-2 or IFN-α2b and doxorubicin by infusing sodium bicarbonate （NaHCO3） through target arteries. Methods： Separating single nucleus cells from peripheral blood of healthy men, and observing the influence of pH on the activation of single nucleus cells by rlL-2. MTT assay was used to measure the killing effect of rlL-2, IFN-α2b and TNF-α on 7404 cells and the increased effect of doxorubicin on rlL-2 and IFN-α2b, the cytotoxity of LAK cells in different pH. Forty-two patients with advanced primary liver cancer were obtained by stratified random, NaHCO3, rIL-2/IFN-α2b and doxorubicin were infused through target arteries. The efficacy was estimated after two cycles. Results： The conditions of pH 7.3 and pH 7.6 in vitro helped the proliferation of LAK cells and the killing effect of rIL-2, IFN-α2b and LAK cells on 7404 cells. In the condition of pH 6.8 there was almost no killing effect for LAK cells. In the condition of pH 7.0, 7.2, 7.4 and 7.6, the killing rate of TNF-α to 7404 cells increased by degrees, and in pH 7.4 the killing effect was the optimum. After two cycles treatments in the 42 patients with advanced primary liver cancer, the response rate （CR＋PR） was 88% （37/42）. The median overall response and median overall survival were increased, and no complication associated with infusing sodium bicarbonate was observed. Conclusion： The killing effect of rIL-2, IFN-α2b, TNF-α and doxorubicin on malignant tumor cells was enhanced by increasing the pH value.

Effect of Electrochemical Treatment in Aqueous Ammonium Bicarbonate on Surface Properties of PAN-based Carbon Fibers

The surface properties of PAN-based carbon fibers electrochemically treated in aqueous ammonium bicarbonate before and after treatment were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and Dynamic Contact Angle Analysis (DCAA). The results of characterization indicated that the oxygen and nitrogen contents in carbon fiber surface were significantly increased by electrochemical treatment, and amide groups was introduced onto it, which was related with the electrolyte. The AFM photographs illustrated that the roughness of the fiber surface was also increased. The wettibality of the fibers was improved after treatment because the surface energy especially the polar part of it was increased.

Is bicarbonate directly used as substrate to participate in photosynthetic oxygen evolution

If the photosynthetic organisms assimilated only CO_(2) in the Archean atmosphere,hydroxide ion in the Archean seawater would not increase.If plants would not consume bicarbonate as a direct substrate during photosynthesis,it is difficult to explain the evolution of Earth's environment.To date,it is generally accepted that photosynthetic O_(2) evolution of plants come from water photolysis.However,it should be debated by evaluating the effect of bicarbonate in photosynthetic O_(2) evolution,analyzing the role of carbonic anhydrase(CA) in photosynthetic O_(2) evolution,and the relationship between thylakoid CA and photosynthetic O_(2) evolution.In the paper,I propose that bicarbonate is directly used as substrate to participate in photosynthetic O_(2) evolution.The rationality of bicarbonate photolysis of plants is discussed from the thermodynamics and evolution of Earth's environment.The isotopic evidence that bicarbonate is not the direct substrate of photosynthetic O_(2) release is reexamined,and the new explanation of bicarbonate photolysis in photosynthetic O_(2) evolution is proposed.

Bicarbonate use and carbon dioxide concentrating mechanisms in photosynthetic organisms

Photosynthesis is crucial to the reduction of carbon dioxide in the atmosphere.The key enzyme of photosynthesis,Ribulose-1,5-bisphosphate carboxylase/oxygenase(Rubisco),has two mutably competing substrates,CO2 and O2.It has features of carboxylase and oxygenase.Rubisco performs the function of carboxylase to reduce inorganic carbon to form organic substances,which precondition is that more carbon dioxide accumulates around it.Carbon dioxide concentrating mechanisms(CCMs)are vital to cope with the limit of carbon dioxide.Various bicarbonate use pathway has a differential contribution to inorganic carbon assimilation.Bicarbonate transport,extracellular bicarbonate dehydration,or H+-ATPase-driven bicarbonate uptake,which induced CCMs,can support a considerable share of photosynthesis in photosynthetic organisms.However,CCMs in thylakoid membranes may be the most important.The CCMs occurred in the plasma membrane were secondary,evolutionary,and inducible,while CCMs coupled with photosynthetic oxygen evolution in thylakoid membranes,were primitive,major,and indispensable.A hypothetical schematic model of CCMs occurred in the plasma membrane and thylakoid membranes being proposed.

Serum bicarbonate may independently predict acute kidney injury in critically ill patients:An observational study

AIM: To explore whether serum bicarbonate at admission to intensive care unit(ICU) predicted development of acute kidney injury(AKI).METHODS:We studied all patients admitted to our ICU over a 2 year period(February 2010 to 2012).The ICU has a case mix of medical and surgical patients excluding cardiac surgical,trauma and neurosurgical patients.We analysed 2035 consecutive patients admitted to ICU during the study period.Data were collected by two investigators independently and in duplicate using a standardised spread sheet to ensure accuracy.Ambiguous data were checked for accuracy where indicated.AKI was defined using the Kidney Disease Improving Global Outcomes criteria.Patients were divided into two groups;patients who developed AKI or those who did not,in order to compare the baseline characteristics,and laboratory and physiologic data of the two cohorts.Regression analysis was used to identify if serum bicarbonate on admission predicted the development of AKI.RESULTS:Of 2036 patients 152(7.5%)were excluded due to missing data.AKI developed in 43.1%of the patients.The AKI group,compared to the nonAKI group,was sicker based on their lower systolic,diastolic and mean arterial pressures and a higher acutephysiology and chronic health evaluation(APACHE)Ⅲand SAPSⅡscores.Moreover,patients who developed AKI had more co-morbidities and a higher proportion of patients who developed AKI required mechanical ventilation.The multi-regression analysis of independent variables showed that serum bicarbonate on admission(OR=0.821;95%CI:0.796-0.846;P<0.0001),APACHEⅢ(OR=1.011;95%CI:1.007-1.015;P<0.0001),age(OR=1.016;95%CI:1.008-1.024;P<0.0001)and presence of sepsis at ICU admission(OR=2.819;95%CI:2.122-23.744;P=0.004)were each significant independent predictors of AKI.The area under the ROC curve was 0.8(95%CI:0.78-0.83),thereby demonstrating that the predictive model has relatively good discriminating power for predicting AKI.CONCLUSION:Serum bicarbonate on admission may independently be used to make a diagnosis of AKI.

Comparison between the Quality Traits of Phosphate and Bicarbonate-Marinated Chicken Breast Fillets Cooked under Different Heat Treatments

Because the use of phosphates has being recently diminished in meat industry due to the nutritional drawbacks of phosphates, some researchers started to evaluate sodium bicarbonate as phosphate replacer in meat products. The aim of this study was to evaluate the effect of different temperature combinations of dry air-cooking treatments (Air and Core temperatures: 160 - 76, 160 - 80, 200 - 76 and 200℃ - 80℃, respectively) on chemical composition, texture properties, water activity, freezable water and bound water, color, pH, and water binding capacity of phosphate and bicarbonate-marinated chicken breast. A batch of 24 h post-mortem broiler breast meat of 80 fillets was divided into two groups of marination treatments (0.3% sodium bicarbonate n = 40, 0.3% sodium tripolyphosphate n = 40) and was vacuum tumbled (45 min, ?0.95 mbar, 20 rpm). Different temperature-combinations cooking treatments significantly modified the chemical composition. Bicarbonate marinated fillets showed higher ability to retain water (67.3% vs. 65.7%, P 0.05) during severe heat treatment and lower cook losses (30.7% vs. 33.4%, P 0.05) when compared with phosphate-marinated fillets. The effect of changing the cooking temperatures on Texture Profile Analysis (hardness, cohesiveness, gumminess, springiness, and chewiness) was more tangible in phosphate marinated fillets than bicarbonate. Bicarbonate-marinated fillets showed significant differences in the percentage of bound water, latent heat, and water activity after cooking in comparison to phosphate-marinated fillets. The results of this study revealed that phosphate-marinated fillets interacted with heat treatments in different patterns in comparison with bicarbonate-marinated fillets.

Effects of Hyperventilation on Venous-Arterial Bicarbonate Concentration Difference: A Possible Pitfall in Venous Blood Gas Analysis

Objectives: Recent reports on venous blood gas analysis have shown that venous bicarbonate concentration is useful in the evaluation of the body acid-base status. Most of these reports have been based on the Bland-Altman analysis comparing arterial and venous blood gas values. We intended to elucidate any factors that decrease the agreement between venous and arterial bicarbonate concentrations, which might impair the usefulness of venous blood gas analysis. Methods: Healthy volunteers and patients with various diseases (n = 141) were evaluated by simultaneous arterial and venous blood sampling and Bland-Altman analysis. The venous-arterial bicarbonate concentration difference was compared between healthy volunteers and untreated respiratory alkalosis patients. Intentional hyperventilation (30 or 60 breaths/min, for 3 min) was also performed on 6 healthy volunteers and the venous-arterial bicarbonate concentration difference was evaluated. Results: The relative average bias in bicarbonate concentration was 2.00 mEq/l with venous bicarbonate higher than arterial bicarbonate with 95% limits of agreement of ±4.15 mEq/l. Hyperventilation challenges increased the venous-arterial bicarbonate concentration difference in an intensity-dependent manner. The venous-arterial bicarbonate concentration difference was higher in untreated respiratory alkalosis patients than in healthy volunteers (P Conclusion: Although venous bicarbonate may be useful to evaluate the body acid-base status, hyperventilation increases the venous-arterial bicarbonate concentration difference. Physicians should keep this phenomenon in mind.

Thermally decarboxylated sodium bicarbonate:Interactions with water vapour,calorimetric study

Isothermal titration calorimetry （ITC） was used to study interactions between water vapour and the surface of thermally converted sodium bicarbonate （NaHCO3）. The decarboxyla- tion degree of the samples was varied from 3% to 35% and the humidity range was 54-100%. The obtained enthalpy values were all exothermic and showed a positive linear correlation with decarboxylation degrees for each humidity studied. The critical humidity, 75% （RHo）, was determined as the inflection point on a plot of the mean-AH kJ/mole Na2CO3 against RH. Humidities above the critical humidity lead to complete surface dissolution. The water uptake （m） was determined after each calorimetric experiment, complementing the enthalpy data. A mechanism of water vapour interaction with decarboxylated samples, including the formation of trona and Wegscheider＇s salt on the bicarbonate surface is proposed for humidities below RHo.

A comparative in vitro study on the cerumenolytic effect of docusate sodium versus 2.5%sodium bicarbonate using UVevisible absorption spectroscopy

Objective:To compare cerumenolytic effects of docusate sodium and of 2.5%sodium bicarbonate-In vitro study;observe characteristics of the solution,using ultravioletevisible(UV/Vis)spectroscopy,and measurement of cholesterol levels.Methods:Samples of human cerumen were mixed to form a relatively homogenous paste.Samples of about 500mg were weighed and packed at the bottom of the test tubes.To each tube was added 1.5 ml of either docusate sodium or 2.5%sodium bicarbonate.Tubes were incubated at 36.4C in a water bath for 15,30 or 60 min.Following incubation,the supernatant solution was pipetted into a cuvette.The cerumenolytic efficacy was defined as the absorbance(recorded at 350 nm and 400 nm)of the solutions.Results were the average of three replicates.A cholesterol level of each sample was then determined to confirm the result.Results:Turbidity was much greater in tubes containing 2.5%sodium bicarbonate,indicating dissolution of cerumen.Mean difference of absorbance values measured at 350 nm and 400 nm after 15,30,60 min digestions were 1.93[95%CI 1.49e2.38,p-value<0.001]and 1.81[95%CI 1.21e2.41,p-value<0.001],respectively.Furthermore,levels of cholesterol were greater in tubes containing 2.5%sodium bicarbonate solution after digestion than in tubes containing docusate sodium;11 mg/dl[95%CI 1.47e24.14,pvalue?0.083]Conclusion:Both spectrophotometric and cholesterol level assessments suggest that 2.5%sodium bicarbonate has a higher cerumenolytic effect than docusate sodium.In other words,cerumen can be dissolved in 2.5%sodium bicarbonate much better than docusate sodium in a time-dependent manner.