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PubMed2006

Ionic liquid matrices with phosphoric acid as matrix additive for the facilitated analysis of phosphopeptides by matrix-assisted laser desorption/ionization mass spectrometry.

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a powerful tool for the analysis and characterization of protein phosphorylation on the peptide level. In this study, the applicability of ionic liquid matrices (ILM) formed by combination of the crystalline MALDI matrix 2,5-dihydroxybenzoic acid (DHB) with pyridine or n-butylamine was tested for the analysis of phosphopeptides. Low ionization efficiency in both positive and negative ion mode was observed in acid-free sample preparations. Upon addition of 0.1% trifluoroacetic acid (TFA), ion formation was increased, but analogously to the situation described earlier for pure DHB, best results were obtained upon use of 1% phosphoric acid as matrix additive. The samples prepared in this way were significantly more homogeneous than preparations with pure DHB, thus avoiding the need for time-consuming search for hot spots. Other characteristics like metastable fragmentation of phosphopeptides did not differ from that observed in classical preparations. The limits of detection for synthetic phosphopeptides and singly or multiply phosphorylated peptides from tryptic digests of alpha- and beta-casein were comparable with those obtained when using pure DHB; in some cases even higher signal intensities could be observed in the ILM. The use of ILM in combination with 1% phosphoric acid as matrix additive significantly facilitates analysis of phosphopeptides by MALDI-MS.

Caseins↗
PubMed2003

Phosphoric acid and various transition metal salt solutions as a combined etchant and activator prior to the use of an anaerobic adhesive.

OBJECTIVES: The objectives of this experiment were to determine whether various transition metal salts in 37% o-phosphoric acid could both activate and etch an enamel surface prior to the use of an anaerobic adhesive. METHOD: Stainless steel attachments were bonded to human enamel using an anaerobic adhesive. In each case, the enamel was etched and activated using a solution of 37% o-phosphoric acid containing various transition metal sulfates and chlorides. After bench curing, the specimens were shear bond tested to failure and the load at debond recorded in each case. RESULTS: The results were analyzed using mean force to debond (N) and 95% confidence intervals. Kaplan-Meier survival probabilities and log-rank tests were also performed.Conclusions. Under the conditions of this experiment, the sulfate and chloride of copper in acid were the most effective etching/activating solutions. There was no significant difference in the mean force to debond between the copper (II) sulfate and copper (II) chloride. The chloride in acid was, however, the only one of the two to produce a conventional etch pattern on the surface of the enamel. SIGNIFICANCE: It is possible to render the enamel surface both retentive and active towards anaerobic adhesives, such that relatively unreactive substrates can be bonded to enamel using such adhesives.

Acid Etching, Dental↗
PubMed2006

Self-etching primer and a non-rinse conditioner versus phosphoric acid: alternative methods for bonding brackets.

The objective of this study was to evaluate the effectiveness of a self-etching primer, Transbond Plus Self Etching Primer (TSEP, 3M Unitek), and a non-rinse conditioner (NRC, Dentsply DeTrey) for bonding brackets, compared with the acid-etch technique. The brackets were bonded to extracted premolars using Transbond XT (3M Unitek). One of the following three conditioning protocols were used: (1) 37 per cent phosphoric acid (n = 25), (2) TSEP (n = 25), and (3) NRC (n = 15). Shear bond strength (SBS) was measured with a universal testing machine. The adhesive remaining after debonding was determined using image analysis equipment. Scanning electron microscope (SEM) observations were also carried out on 12 premolars to observe the enamel surfaces. No significant differences were observed in SBS between the three groups (P = 0.56). TSEP and NRC left significantly less adhesive on the tooth than the traditional acid-etch technique (P = 0.004 and P = 0.000, respectively). NRC left significantly less adhesive than TSEP (P = 0.001). SEM observations showed that NRC produced a less aggressive etch pattern than TSEP, and that the etching effect of TSEP approximated that of phosphoric acid.

Acid Etching, Dental↗
PubMed1993

Whole-body exposures to a phosphoric acids aerosol: II. Food/water/weight effects in wild rodent and avian species.

Separate inhalation-chamber studies were conducted to assess acute/subacute food intake (g), water intake (ml), and body weight (g) effects of four whole-body phosphoric-acids-aerosol exposures in black-tailed prairie dogs (Cynomys ludovicianus); subacute effects of two exposures were studied in rock doves (Columba livia). A 95% red phosphorus/5% butyl rubber (RP/BR) mixture was burned to produce the aerosol. Each study involved (1) 3 RP/BR target concentration groups (0.0, 1.0, and 4.0 mg/L), (2) 24 prairie dogs or doves (8/group), with gender included as a factor in each study, and (3) a successive 3-phase paradigm (2 d preexposure; 4 and 2 d of approximately 80 min/d exposures to RP/BR for prairie dogs and rock doves, respectively; and 6 d postexposure). Results showed that in-chamber atmospheres were uniform and acceptable for all exposures. No prairie dogs died, but 1 male rock dove died on d 3 postexposure to 4.0 mg/L aerosol. Concentration and gender main effects were significant for the acute (2 h out-of-chamber) food intake, water intake, and weight change of prairie dogs, with aerosol-exposed and male rodents showing decrements. Gender and day main effects were also significant for the subacute (23 h/d) variables in prairie dogs; females weighted less than males, and reduced food/water/weight was evident for all animals during the 4 exposure days and first 3 postexposure days. For rock doves, subacute gender and day main effects, plus concentration x day and concentration x gender x day interactions, characterized the data. A transitive relationship was evident among RP/BR aerosol conditions (0.0 < 1.0 < 4.0 mg/L) and mean decreased food intakes on the exposure days (d2 < d1). Enhanced postexposure water replenishment by female versus male doves exposed to 4.0 mg/L RP/BR aerosol was a main finding. Results are explained based upon a temporal model of phosphoric acid caused ulcers/edema. Effects are compared to prior evidence for albino rats, prairie dogs and rock doves; these are also discussed relative to certain human health and ecotoxicological literature.

Aerosols↗
PubMed1977

[Chronic broncopneumopathy and pneumoconiosis in workers employed in phosphoric acid production (author's transl)].

Thirty-five subjects employed in a phosphoric acid producing plant were studied by the authors. The investigation included: history, according to the C.E.C.A. questionnaire for chronic bronchitis and emphysema; physical examination, chest X-ray spirometry and lung diffusing capacity for carbon monoxide by the steady state method (DLCOSS). High prevalence of chronic bronchitis (45.7%), obstructive spirometric impairment (37.1%), and decreased values of DlcoSS (31.4%) were detected. Two subjects were found to be affected with p 1/0 and 7 with p 0/1 pneumoconiosis. Such findings were significantly related to the lenght of working activity as well as to dust and gaseous fluoride (hydrofluoric acid, hexafluorosilicic acid and silicon tetrafluoride) exposure.

Adult↗
PubMed2005

Bond strength between four luting systems and enamel modified with phosphoric acid.

The purpose of this study was to investigate the effect of phosphoric acid etching on the bond strength between enamel and three luting materials employing self-etching primer (PanaviaF2.0, Linkmax, and Multibond). A luting material without self-etching primer (Super-Bond) was used as a control. Two etching agents (K-etchant and Red Activator) were prepared. The surfaces of bovine enamel were ground, etched with either K-etchant or Red Activator, and then bonded to a stainless steel rod. Tensile bond strengths were determined following 24-hour immersion in water. Without etching, all of the luting materials showed the same statistical bond strength. When K-etchant was applied, the bond strengths of PanaviaF2.0, Linkmax, Multibond, and Super-Bond were significantly greater than that of non-etched control. No significant differences were found between K-etchant and Red Activator. Strongest bonds were obtained for Super-Bond in conjunction with K-etchant (23.6 +/- 6.3 MPa) or Red Activator (21.0 +/- 6.5 MPa), whereby the values were statistically comparable.

Acid Etching, Dental↗
PubMed2001

Treatment of phosphoric acid plant wastewater using Fenton's reagent and coagulants.

The results of treatability studies viz., Fenton reaction and physico-chemical (coagulation) treatment using lime, alum, Fe salts and polyaluminium chloride (PAC) performed on wastewater generated from a unit manufacturing technical grade phosphoric acid are reported. Due to low biochemical oxygen demand (BOD) chemical oxygen demand (COD) ratio and very low pH, this wastewater is not amenable for biological treatment. The treatability studies indicated that it is possible to remove 75-80% COD using Fenton's reagent at optimum doses of 1.0 g/L FeSO4 and 2 ml of 30% H2O2. Simultaneously, significant quantities of suspended solids, phosphate and fluoride are also removed. Polyaluminium chloride is found to be more effective towards suspended solids (SS), COD, phosphate and fluoride removal, when compared to other coagulants used in the present study. Addition of an anionic polyelectrolyte (Magnafloc 156) to PAC improved the performance further. A treatment scheme that consists of neutralization (pH 4) + Fenton's reagent + neutralization (pH 7.5) + PAC/Magnafloc 156 is found to be effective in treating phosphoric acid plant wastewater to meet marine discharge standards.

Alum Compounds↗
PubMed1993

Whole body exposures to a phosphoric acids aerosol: I. Spontaneous activity effects in wild rodent and avian species.

Two inhalation-chamber studies were conducted to assess acute (2-h out-of-chamber) and subacute (< or = 6 d postexposure) spontaneous activity effects of whole-body phosphoric acids aerosol exposure(s) in black-tailed prairie dogs (Cynomys ludovicianus) and rock doves (Columba livia). The aerosol was generated using a red phosphorus/butyl rubber (RP/BR) mixture under development as a military obscurant. Each study involved (1) 3 RP/BR target concentration groups [0.0 (controls), 1.0, and 4.0 mg/L], (2) 24 prairie dogs or rock doves (8/group), with gender included as a factor, (3) a successive 3-phase paradigm (2 d preexposure; 4 and 2 d of about 80 min/d exposures to RP/BR for prairie dogs and rock doves, respectively; and 6 d postexposure), and (4) infrared detection of the rodents'/birds' home-cage movements. In-chamber atmospheres were uniform and acceptable for all exposures; median aerosol mass concentrations ranged from 0.76 to 0.89 mg/L and 3.46 to 3.74 mg/L for the 1.0 and 4.0 mg/L groups, respectively, with median phosphoric acid (H3PO4) readings of between 67.2 and 74.3%; median particles were < or = 0.85 microns. Mortality was negligible; no prairie dogs died, but 1 male rock dove died on d 3 postexposure to two 4.0 mg/L target concentrations of RP/BR aerosol. Group x session interactions were significant for the acute activity counts of both species. The acute mean ambulatory (e.g., walking) counts of prairie dogs and the acute mean ambulatory and horizontal (e.g., preening) counts of rock doves exposed to 4.0 mg/L RP/BR aerosol were relatively less than those of the other groups after the first 2 or 1 exposures, respectively. Nevertheless, acute session means for all groups approximated or exceeded the 23 h/d activity measured during the pre- and postexposure phases--data indicating that chamber confinement caused a temporary, sharp increase in activity for both species irrespective of RP/BR aerosol concentrations. No RP/BR concentration-related, subacute shifts in the activity of the rodents/birds were observed.

Administration, Inhalation↗
PubMed2004

Phosphoric acid enhances the performance of Fe(III) affinity chromatography and matrix-assisted laser desorption/ionization tandem mass spectrometry for recovery, detection and sequencing of phosphopeptides.

An integrated analytical strategy for enrichment, detection and sequencing of phosphorylated peptides by matrix-assisted laser desorption/ionization (MALDI) tandem mass spectrometry (MS/MS) is reported. o-Phosphoric acid was found to enhance phosphopeptide ion signals in MALDI-MS when used as the acid dopant in 2,5-dihydroxybenzoic acid (2,5-DHB) matrix. The effect was largest for multiply phosphorylated peptides, which exhibited an up to ten-fold increase in ion intensity as compared with standard sample preparation methods. The enhanced phosphopeptide response was observed during MALDI-MS analysis of several peptide mixtures derived by proteolytic digestion of phosphoproteins. Furthermore, the mixture of 2,5-DHB and o-phosphoric acid was an excellent eluant for immobilized metal affinity chromatography (IMAC). Singly and multiply phosphorylated peptide species were efficiently recovered from Fe(III)-IMAC columns, reducing sample handling for phosphopeptide mapping by MALDI-MS and subsequent phosphopeptide sequencing by MALDI-MS/MS. The enhanced response of phosphopeptide ions in MALDI facilitates MS/MS of large (>3 kDa) multiply phosphorylated peptide species and reduces the amount of analyte needed for complete characterization of phosphoproteins.

Amino Acid Sequence↗
PubMed1980

[Paramagnetic diethyleneimides of urethane phosphoric acids as antitumor agents].

Under study were paramagnetic diethylene imides of urethan phosphoric acids containing three type groups showing carcinostatic activity. There was found small toxicity and a wide spectrum of the antitumor effect of the compounds, also the correlation between the chemical structure and carcinostatic effect was investigated. The nitroxyl radical was shown to participate in the antitumor effect manifestation.

Animals↗
PubMed2006

Hydrolysis of sorghum straw using phosphoric acid: evaluation of furfural production.

Sorghum straw is a waste that has been studied scarcely. The main application is its use as raw material for xylose production. Xylose is a hemicellulosic sugar mainly used for its bioconversion toward xylitol. An alternative use could be its conversion toward furfural. The objective of this work was to study the furfural production by hydrolysis of sorghum straw with phosphoric acid at 134 degrees C. Several concentrations of H(3)PO(4) in the range 2-6% and reaction time (range 0-300 min) were evaluated. Kinetic parameters of mathematical models for predicting the concentration of xylose, glucose, arabinose, acetic acid and furfural in the hydrolysates were found. Optimal conditions for furfural production by acid hydrolysis were 6% H(3)PO(4) at 134 degrees C for 300 min, which yielded a solution with 13.7 g furfural/L, 4.0 g xylose/L, 2.9 g glucose/L, 1.1g arabinose/L and 1.2g acetic acid/L. The furfural yield of the process was 0.1336 g furfural/g initial dry matter was obtained. The results confirmed that sorghum straw can be used for furfural production when it is hydrolyzed using phosphoric acid.

Acetic Acid↗
PubMed2000

X-Ray Photoelectron Spectroscopy Analysis of Di-(2-ethylhexyl) Phosphoric Acid Activated Membranes.

Surface chemical characterization of activated composite membranes, which consist of a polyamide/polysulfone support containing different amounts of di-(2-ethylhexyl) phosphoric acid as carrier, was performed by X-ray photoelectron spectroscopy (XPS) in order to obtain information about the nature of the chemical bonding between the carrier and the membrane top layer. XPS spectra of the top layer of the polymeric support (polyamide) show bands in the C 1s, N 1s, O 1s, and P 2p regions. The N 1s and O 1s signals of the polyamide layer were asymmetric and could be deconvoluted in two peaks that correspond to the coexistence of free and hydrogen bonded polyamide. To support this assignment, primary amides such as benzamide and n-butyramide, which can associate themselves forming hydrogen bonding, and a tertiary amide, N-benzoyl morpholine, unable to form hydrogen bonding, were also studied by XPS. The N 1s asymmetric signals of benzamide and n-butyramide were deconvoluted in two peaks due to the coexistence of free and hydrogen bonded species, while the N 1s signal of N-benzoyl morpholine is symmetric and corresponds to the existence of free amide alone. As a result of the addition of di-(2-ethylhexyl) phosphoric acid to the polymeric matrix, the N 1s signal intensities decrease, while the P 2p signal intensities increase with carrier concentration to a maximum corresponding to surface site saturation. Upon acid addition, the polyamide was protonated and an expected chemical shift of the N 1s signal to higher binding energies was observed due to the increase of the positive charge of the nitrogen atom. This type of chemical interaction allows to fix the carrier in the membrane without its complete immobilization. On the other hand, the surface concentration of N and P, determined by XPS, indicates that a concentration of 400 mM of the carrier in the casting solution is sufficient to saturate the surface of the membrane. Copyright 2000 Academic Press.

Journal Article↗
PubMed2005

Highly electrophilic, 16-electron [Ru(P(OMe)(OH)(2))(dppe)(2)](2+) complex turns H(2)(g) into a strong acid and splits a Si-H bond heterolytically. Synthesis and structure of the novel phosphorous acid complex [Ru(P(OH)(3))(dppe)(2)](2+).

The highly electrophilic, 16-electron, coordinatively unsaturated [Ru(P(OMe)(OH)(2))(dppe)(2)][OTf](2) complex brings about the heterolytic activation of H(2)(g) and spontaneously generates HOTf. In addition, trans-[Ru(H)(P(OMe)(OH)(2))(dppe)(2)](+) and an unprecedented example of a phosphorous acid complex, [Ru(P(OH)(3))(dppe)(2)](2+), are formed. The [Ru(P(OMe)(OH)(2))(dppe)(2)][OTf](2) complex also cleaves the Si-H bond in EtMe(2)SiH in a heterolytic fashion, resulting in the trans-[Ru(H)(P(OMe)(OH)(2))(dppe)(2)](+) derivative.

Journal Article↗
PubMed2001

Cassava starch maltodextrinization/monomerization through thermopressurized aqueous phosphoric acid hydrolysis.

Kinetic conditions were established for the depolymerization of cassava starch for the production of maltodextrins and glucose syrups. Thin-layer chromatography and high-performance liquid chromatography analyses corroborated that the proper H3PO4 strength and thermopressurization range (e.g., 142-170 degrees C; 2.8-6.8 atm) can be successfully explored for such hydrolytic purposes of native starch granules. Because phosphoric acid can be advantageously maintained in the hydrolysate and generates, after controlled neutralization with ammonia, the strategic nutrient triplet for industrial fermentations (C, P, N), this pretreatment strategy can be easily recognized as a recommended technology for hydrolysis and upgrading of starch and other plant polysaccharides. Compared to the classic catalysts, the mandatory desalting step (chloride removal by expensive anion-exchange resin or sulfate precipitation as the calcium-insoluble salt) can be avoided. Furthermore, properly diluted phosphoric acid is well known as an allowable additive in several popular soft drinks such as colas since its acidic feeling in the mouth is compatible and synergistic with both natural and artificial sweeteners. Glycosyrups from phosphorolyzed cassava starch have also been upgraded to high-value single-cell protein such as the pigmented yeast biomass of Xanthophyllomyces dendrorhous (Phaffia rhodozyma), whose astaxanthin (diketo-dihydroxy-beta-carotene) content may reach 0.5-1.0 mg/g of dry yeast cell. This can be used as an ideal complement for animal feeding as well as a natural staining for both fish farming (meat) and poultry (eggs).

Biomass↗
PubMed2004

Improved detection of multi-phosphorylated peptides in the presence of phosphoric acid in liquid chromatography/mass spectrometry.

In contrast to lower phosphorylation states (e.g. the tryptic monophosphopeptide FQpSEEQQQTEDELQDK from bovine beta-casein), the specific detection of multi-phosphorylated peptides (e.g. the tetraphosphopeptide RELEELNVPGEIVEpSLpSpSpSEESITR from tryptic digestion of bovine beta-casein) has often been problematic for liquid chromatographic mass spectrometric (LC/MS) analysis owing to their high affinity for adsorption to exposed surfaces. We observed an enhancement in the overall detection of phosphopeptides on addition of phosphoric acid (0.1-1.0%) to the sample solution; a 10-fold increase in sensitivity was determined for the detection of two tryptic phosphopeptides and also a significant improvement in the detection of the tetraphosphopeptide. Using capillary LC with ion trap tandem MS for detection and identification, the achievable detection limits were 50 fmol and 50 pmol for the monophosphopeptide and the tetraphosphopeptide, respectively. Phosphoric acid is believed to act as a blocking agent to available silanol groups on both the silica capillary surface and the C(18)-bonded stationary phase silica surface.

Animals↗