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PubMed2005

Analysis of perchlorate in water by reversed-phase LC/ESI-MS/MS using an internal standard technique.

A new method was developed for the analysis of perchlorate in water by using reversed-phase liquid chromatograhy/electrospray ionization-mass spectrometry/mass spectrometry (LC/ESI-MS/MS) in the negative ESI mode. Selective and sensitive perchlorate detection was obtained by monitoring the 35ClO4- --> 35ClO3- and 37ClO4- --> 37ClO3- mass transitions. The 35ClO4- --> 35ClO3- transition was quantitated against the internal standard oxygen-labeled sodium perchlorate (NaCl18O4). Sample pretreatment for the removal of major common anions and dissolved metal ions along with internal standard quantitation sufficiently compensated for ion suppression caused by the matrix. The 37ClO4- --> 37ClO3- transition was examined to provide additional specificity. The method sensitivity, accuracy, and precision were investigated by analyzing fortified blank samples, field samples, and performance evaluation samples. The results (1.01-13.5 microg/L) for the proficiency evaluation samples differed from the certified values (1.04-14.1 microg/L) by 3-18%. The developed reversed-phase LC/ESI-MS/MS method was rapid, accurate, and reproducible. The calculated method detection limits were 0.007 microg/L for deionized reagent water and 0.009 microg/L for synthesized reagent water, respectively. The minimum reporting limit was conservatively set to 0.05 microg/L.

Journal Article↗
PubMed2006

Ferroelectric ordering in imidazolium perchlorate.

Imidazolium perchlorate has been synthesized and studied over a wide range of temperatures by differential scanning calorimetry, x-ray diffraction, proton magnetic resonance, optical observation, and dielectric spectroscopy. Polymorphic solid-solid phase transitions have been disclosed at 487, 373, and 247 K. The crystal structure at 298 K has been determined as trigonal, space group R3m, Z=1 with a=5.484(1) A and alpha=95.18(2) degrees. The imidazolium cations are strongly disordered, while the perchlorate ions are well ordered. At 385 K the crystal structure remains trigonal, space group R3m, a=5.554(1) A and alpha=95.30(2) degrees . Both ionic sublattices are orientationally disordered. Temperature evolution of the molecular dynamics of the imidazolium cation has been characterized. In spite of a high cationic disorder, dielectric measurements have revealed the polar properties of the crystal. It appears to be a new ferroelectric compound with the Curie point at 373 K. The spontaneous polarization originates predominantly from the behavior of slightly distorted perchlorate anion.

Journal Article↗
PubMed1999

Ribonuclease activity of rat liver perchloric acid-soluble protein, a potent inhibitor of protein synthesis.

Rat liver perchloric acid-soluble protein (L-PSP) is a potent inhibitor of cell-free protein synthesis; however, its mechanism of action is not known. Here we show that the protein is a unique ribonuclease and that this activity is responsible for the inhibition of translation. The addition of perchloric acid-soluble protein to a rabbit reticulocyte cell-free system at a concentration of 6.2 microM led to an almost complete inhibition of protein synthesis. The kinetics are unlike those of hemin-controlled inhibitor, a protein that acts at the initiation step. The inhibition appears to be due to an endoribonucleolytic activity of perchloric acid-soluble protein because L-PSP directly affects mRNA template activity and induces disaggregation of the reticulocyte polysomes into 80 S ribosomes, even in the presence of cycloheximide. These effects were observed with authentic as well as recombinant L-PSP. Analysis by thin-layer chromatography of [alpha-32P]UTP-labeled mRNA incubated with the protein showed production of the ribonucleoside 3'-monophosphates Ap, Gp, Up, and Cp, providing direct evidence that the protein is an endoribonuclease. When either 5'- or 3'-32P-labeled 5 S rRNA was the substrate, L-PSP cleaved phosphodiester bonds only in the single-stranded regions of the molecule.

Animals↗
PubMed2003

Redetermination of hydronium perchlorate at 193 and 293 K.

A sample of hydronium perchlorate, H(3)O(+) x ClO(4)(-), crystallized from ethanol at ambient temperature, was found to be orthorhombic (space group Pnma) at both 193 and 293 K, with no phase transition observed in this temperature range. This contrasts with the earlier observation [Nordman (1962). Acta Cryst. 15, 18-23] of a monoclinic phase (space group P2(1)/n) at 193 K for crystals grown at that temperature from perchloric acid. The hydronium and perchlorate ions lie across a mirror plane but it is not possible to define at either temperature a simple description of the H-atom positions due to the three-dimensional tumbling of the hydronium cation.

Journal Article↗
PubMed1991

Tris[(2-pyridinium)methyl]amine perchlorate.

Nitrilotrismethylenetri-2-pyridinium perchlorate, C18H21N4(3+).3C1O4-, Mr = 591.74, cubic, P2(1)3, a = 13.289 (3) A, V = 2347 (2) A 3, Z = 4, Dx = 1.675 (2) g cm-3, lambda(Mo K alpha) = 0.71069 A, mu = 4.60 cm-1, F(000) = 1216, T = 189 (3) K, R = 0.056 for 1073 unique observed reflections with I greater than sigma(I). All four ions lie on threefold axes. The perchlorate ions are nearly regular tetrahedra. The bond lengths and angles in the ions are normal. As the name implies, the cation is protonated on the pyridine N atoms and not on the amine N atom. Each H atom attached to an N atom is part of a three-centered hydrogen bond in which the H-atom acceptors are O atoms on two different perchlorate ions.

Models, Molecular↗
PubMed1999

The tert-butylammonium perchlorate complex of 2,3-naphtho-18-crown-6 at 115 K.

In the title complex, tert-butylammonium perchlorate-2,5,8,11,14,17-hexaoxatricyclo[16.8.0.0(20,25]hexac osa- 1(26),18,20(25),21,23-pentaene-ethyl acetate-dichloromethane (4/4/1/1), C4H12N+.C20H26O6.ClO4-.0.25C4-H8O2.0.25CH2Cl2 , the tert-butylammonium cation binds to the macrocyclic host (Chemical Abstracts name: 2,3,5,6,8,9,11,12,14,15-decahydro-1,4,7,10,13,16-hexaoxanaphtho [2,3- b]cyclooctadecin) in the expected tripod arrangement, while the perchlorate anion links naphthyl groups in the crystal through C-H...O-Cl-O...H-C interactions. Thermal motion analysis indicates that the tert-butylammonium group and the perchlorate anion each librate with respect to the host, with amplitudes of 6.2 (4) and 11.4 (2) degrees, respectively.

Crown Ethers↗
PubMed1987

Duration of antithyroid action of methimazole estimated with an intravenous perchlorate discharge test.

We have used a method based on a perchlorate discharge test to estimate the duration of antithyroid effect of two doses of methimazole (MMI). Six patients with diffuse toxic goitre took 5 mg MMI twice daily and six took 20 mg twice daily over the study period of 12 weeks. Biochemical control of hyperthyroidism was achieved in all patients and thyroid hormone supplementation was required by all of the patients in the higher dose group to avoid hypothyroidism. Discharge of radioiodine from the thyroid by perchlorate diminished in both groups with time after MMI. After 5 mg MMI, perchlorate discharge as a percentage of the 30-min uptake (mean +/- SD), was 81.7 +/- 3.3% at 2.2 h, 69.3 +/- 18.9% at 5.9 h, 22.6-23.4% at 13.4 h and 2.7-6.7% at 25.1 h. After 20 mg MMI, the discharge was 92.5 +/- 1.9% at 2.2 h, 84.3 +/- 8.8% at 6.3 h, 64.8 +/- 24.1% at 13.3 h and 26.9-29.4% at 25.1 h. Only four patients (one in the lower dose group) showed a detectable discharge at 25 h and one of the patients treated with the lower dose showed no discharge at 13 h. These estimates of the effect of MMI on thyroidal iodide organification are not in keeping with published thyroidal MMI concentrations which do not show a fall between 3-6 h and 17-20 h after carbimazole. The explanation for this disparity is not clear but may be based on a redistribution of thioureylenes within the thyroid with time after dosage.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2002

Perchloric acid enhances sensitivity and reproducibility of the ferric-xylenol orange peroxide assay.

The ferrous oxidation in xylenol orange (FOX) assay for hydroperoxides suffers from very narrow pH optimum in the range 1.7-1.8. Most published protocols recommend 25 mM sulfuric acid as the solvent, but this in practice does not ensure the maintenance of correct pH in the presence of materials such as samples of biological origin. Substitution of perchloric for the sulfuric acid resulted in a lowering of the optimum pH of the assay to 1.1, a decreased dependence of the absorbance of the ferric-xylenol orange complex on acid concentration and decreased sensitivity to added compounds. Molar absorption coefficients of hydrogen peroxide, cumene, and butyl hydroperoxides and of hydroperoxide groups generated in oxidized protein and lipids were determined and found to be higher than in sulfuric acid. The optimum concentration of perchloric acid proved to be 110 mM. The new assay was designated as PCA-FOX, to distinguish it from the FOX methods based on sulfuric acid.

Animals↗
PubMed1980

Quantitation of thyroidal binding of iodide by compartmental analysis verified by an intravenous perchlorate discharge test.

Compartmental analysis was applied to 123I-iodide uptake data to quantitate iodine binding in the human thyroid gland. The method allowed for arterio/venous differences in plasma tracer level and for an "instantaneous" phase of thyroid uptake. Results were checked by an intravenous perchlorate discharge test. Observations in eleven normal and untreated thyrotoxic subjects confirmed earlier findings that iodine binding takes place rapidly, the binding rate constant being much greater than the exit rate constant. A lower limit of 0.15 min-1 for the binding rate constant in the uninhibited gland was estimated from the observations in one subject who demonstrated a small perchlorate discharge. The method was used in the study of eight subjects with an intrinsic binding defect and of twenty-four thyrotoxic subjects being treated with 5 mg or 20 mg carbimazole, twice daily. Binding rate constants (range 0.003--0.105 min-1) were typically less than the exit rate constants (range 0.027--0.156 min-1), the net clearance of iodide ranging from 1.5 to 67.9% of the unidirectioinal clearance, compared to 72% in the uninhibited gland. The method proved useful in assessing the severity of an intrinsic binding defect and in the investigation of lack of response to antithyroid drug therapy.

Computers↗
PubMed1976

Loss of ATP in micromolar amounts after perchloric acid treatment.

Treatment of fluid samples containing known amounts of ATP with 6.0 N perchloric acid (PCA) results in a total loss of 65-71% when the initial concentrations of ATP ranged between 0.5 to 50 muM. Half of this loss was attributed to desensitization of firefly extract (luciferin-luciferase reaction) while the remaining loss was presumably due to adsorption of ATP to perchlorate precipitate upon neutralization. Similar treatment of solutions with higher initial concentrations (100-1000 muM) resulted in apparent total losses averaging 22%. These losses were due solely to desensitization of firefly extract by neutralized PCA. Both the adsorption and desensitization phenomena must be taken into account when the ATP content is measured from tissue extracts and fluid samples subjected to this procedure.

Adenosine Triphosphate↗
PubMed2006

Simultaneous bio-reduction of nitrate, perchlorate, selenate, chromate, arsenate, and dibromochloropropane using a hydrogen-based membrane biofilm reactor.

We tested the hypothesis that the H(2)-based membrane biofilm reactor (MBfR) is capable of reducing multiple oxidized contaminants, a common situation for groundwater contamination. We conducted bench-scale experiments with three groundwater samples collected from California's San Joaquin Valley and on two synthetic groundwaters containing selenate and chromate. The actual groundwater sources had nitrate levels exceeding 10 mg-N l(-1) and different combinations of anthropogenic perchlorate + chlorate, arsenate, and dibromochloropropane (DBCP). For all actual groundwaters, the MBfR reduced nitrate to less than 0.01 mg-N l(-1). Present in two groundwaters, perchlorate + chlorate was reduced to below the California Notification Level, 6 microg-ClO(4) l(-1). As(V) was substantially reduced to As(III) for two groundwaters samples, which had influent As(V) concentrations from 3 to 8.8 microg-As l(-1). DBCP, present in one groundwater at 1.4 microg l(-1), was reduced to below its detection limit of 0.01 microg l(-1), which is well below California's 0.2 microg l(-1) MCL for DBCP. For the synthetic groundwaters, two MBfRs initially reduced Se(VI) or Cr(VI) stably to Se degrees or Cr(III). When we switched the influent oxidized contaminants, the new oxidized contaminant was reduced immediately, and its reduction soon was approximately the same or greater than it had been reduced in its original MBfR. These results support that the H(2)-based MBfR can reduce multiple oxidized contaminants simultaneously.

Arsenates↗
PubMed1983

Hypothyroidism associated with positive results of the perchlorate discharge test in elderly patients.

In 172 patients over the age of 55, determinations were made of thyrotropin concentrations in plasma. Although they showed such symptoms or signs of hypothyroidism as puffy face, dry skin, general malaise, cold intolerance, or constipation, there were no clinical indications of overt hypothyroidism. All the patients were apparently in a normal nutritional state, without any specific medication that might cause thyroid abnormalities. Seventeen (six men and 11 women, 9.9 percent) of the 172 patients, aged 58 to 83, had elevated plasma thyrotropin levels, ranging from 12.1 microU/ml to 170 microU/nl. To investigate the characteristics of hypothyroidism in the elderly, the perchlorate discharge test was performed in these patients. In 15 of the 17 patients, 123I thyroid uptake diminished markedly immediately after the administration of 1 g perchlorate. Thirteen of these 15 patients showed markedly diminished thyroxine (T4) levels in serum, whereas the magnitude of diminution in serum 3,5,3'-triiodothyronine (T3) values was small. Two patients with the negative discharge results showed normal T4 and T3 levels in serum. Four patients had a very small goiter, and the remaining 13 patients had no detectable goiter. Fifteen of the 17 patients had no detectable circulating thyroid antibodies in repeated determinations, and the histologic features of Hashimoto's thyroiditis were not found in the thyroid specimens obtained from two patients. These findings suggest the existence of hypothyroidism attributable to iodine organification defect without evidence of autoimmune thyroiditis in some cases in elderly patients.

Aged↗
PubMed1991

Phosphorus 31 magnetic resonance spectroscopy of human placenta and quantitation with perchloric acid extracts.

Phosphorus 31 magnetic resonance spectroscopic studies of fresh placental tissue are reported that indicate resonances for adenosine triphosphate, inorganic phosphate, sugar phosphates-phosphomonoesters, and phosphodiesters. Perchloric acid extract methods were used to further characterize and quantitate phosphorous metabolites in term human placentas by phosphorus 31 magnetic resonance spectroscopy. The perchloric acid extracts give enhanced resolution of phosphorus signals and allow identification of other phosphorus metabolites including small amounts of phosphocreatine. Emphasis was placed on quantitating adenosine triphosphate levels in the acid extracts with the use of the external reference standard hexachlorocyclotriphosphazene in a coaxial capillary system. Adenosine triphosphate levels measured in this way ranged from 0.404 to 0.709 mumol per gram wet weight. Comparison with an internal standard method with phosphocreatine is also reported. Contribution to the measured high-energy phosphate pool from blood in the highly vascularized tissue was found to be relatively large and could range from 30% to 50% of the total adenosine triphosphate measured.

2,3-Diphosphoglycerate↗
PubMed1984

A rapid and safe method of estimating nanomole quantities of P, K+, Na+, Ca2+, and Mg2+ in plant material by perchloric acid digestion.

A method for the determination of nanomole amounts of P and major cations in samples of dried plant tissue is described. Samples weighing 2-7 mg were digested by refluxing tissue in a mixture of perchloric and nitric acids, under conditions which minimized the hazards associated with perchloric acid digestion. In most tissues analyzed, reproducibility between triplicate samples was less than +/- 5%. However, where the amount of P in the tissue was very low (samples contained about 50 nmol P each), the variation between triplicates was greater.

Calcium↗
PubMed1990

Colorimetric micromethods for glutaraldehyde determination by means of phenol and sulfuric acid or phenol and perchloric acid.

Aqueous micromolar solutions of glutaraldehyde produce a yellow color when treated with 20% phenol in ethanol followed by concentrated sulfuric acid or with phenol in 70% perchloric acid. The absorbance at 482 or 479 nm, respectively, is linearly related to the glutaraldehyde concentration. Of the two methods developed, the sulfuric acid-phenol assay gives a higher sensitivity and the perchloric acid-phenol assay allows the determination of glutaraldehyde in the presence of sugars and proteins.

Aldehydes↗
PubMed1980

1H-NMR and rosonance Raman spectra of octaethylporphyrinatoiron(III) perchlorate and its mono imidazole adduct.

The 1H-NMR spectra and the resonance Raman spectra of intermediate spin complex, octaethylporphyrinatoiron (III) perchlorate (OEP-Fe(III)ClO4) and its mono imidazole adduct have been recorded and analyzed. The perchlorate complex was determined to be an intermediate-spin state (S = 3/2) in dichloromethane. The mono imidazole and 2-methylimidazole adducts of OEP-Fe(III)ClO4 were of the high-spin state in dichloromethane, which is a good model for the ferrihemoproteins such as metmyoglobins. The spin state of OEP-Fe(III)ClO4 varies the polarity of solvent from typical high-spin (S = 5/2) to typical low-spin (S = 1/2) state including intermediate-spin state (S = 3/2). The resonance Raman studies of the intermediate-spin complex in various solvents indicate that the complex is a plausible model to reproduce anomalous physico-chemical properties of the ferricytochrome c' at physiological condition.

Cytochrome c Group↗
PubMed1975

Rapid radioimmunoassay of carcinoembryonic antigen (CEA) in ultrafiltered perchloric acid extracts: results of a clinical survey.

Perchloric acid treatment of the carcinoembryonic antigen (CEA) results in subunits of approximate mol. wt 40 000 to 50 000 with different electrophoretic mobilities and amtogenic deficiences as demonstrated by immunoelectrophoresis. An improved radioimmunoassay is described for the quantitation of CEA using rapid ultrafiltration of serum or plasma extracts. The assay was designed to take into account the changes CEA undergoes during perchloric acid extraction. Absorption of antibodies against a crossreacting non-specific antigen from CEA antiserum did not improve the specificity of the radioimmunoassay as was shown by clinical use of the test in almost 1800 patients.

Animals↗
PubMed2004

Challenges encountered in extending the sensitivity of US Environmental Protection Agency Method 314.0 for perchlorate in drinking water.

Concerns about the potential adverse health effects of perchlorate at concentrations below the minimum reporting level (MRL) of US Environmental Protection Agency (EPA) Method 314.0 (generally recognized as 4.0 microg/l) have led to an interest in increasing the sensitivity of the method. This work describes the use of 2 mm columns with a large-loop direct injection method, a column concentration technique and this concentration technique with a background reduction step, to increase the sensitivity for the analysis of trace levels of perchlorate in high ionic strength matrices. The concentrator columns studied were the Dionex TAC LP-1 and a new Dionex high capacity Cryptand concentrator column. The use of a surrogate to monitor trapping efficiency for the concentration technique and the use of confirmational columns to minimize the potential for false positives are also discussed. The large-loop direct injection method and the column concentration methods provided acceptable data when the samples were pre-treated with solid phase pretreatment cartridges. The background reduction technique did not provide acceptable data with either of the concentrator columns evaluated.

Chromatography, Liquid↗