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At least 19 recordsLinked to original sources
PubMed1987

A rapid vapor-phase acid (hydrochloric acid and trifluoroacetic acid) hydrolysis of peptide and protein.

A new method for the acid hydrolysis of protein is presented. Peptide bonds are cleaved by the action of an HCl/trifluoroacetic acid (TFA) vapor mixture. Contamination for the hydrolysis mixture is reduced to low levels (1-3 pmol). Recovery of hydrophobic amino acid is improved. Short reaction times are achieved and rapid removal of acids is facilitated. The reaction temperature is 158 degrees C for reaction times of 22.5 and 45 min with 7 M HCl and 10% TFA containing 0.1% phenol.

Amino Acids↗
PubMed1981

Atomic absorption spectrometric determination of tin in canned foods using nitric acid-hydrochloric acid digestion and nitrous oxide-acetylene flame.

Foods (5-40 g) are digested sequentially with HNO3 and HCI, diluted to 100 mL, and filtered, and tin is determined by atomic absorption using an N2O-C2H2 flame. Synthetic standards in 10% HCl are used. A positive interference by potassium is compensated by adding 100 micrograms potassium/mL to both standards and samples. Recoveries for 17 foods spiked with tin at levels between 40 and 500 micrograms/g ranged from 85 to 110% with a mean of 101%. Results agreed well with a solvent extraction atomic absorption method and a direct X-ray fluorescence method.

Acetylene↗
PubMedDate not supplied

Atomic absorption spectrophotometric determination of tin in canned foods, using nitric acid-hydrochloric acid digestion and nitrous oxide-acetylene flame: collaborative study.

Twenty-six collaborators participated in a study to evaluate an atomic absorption spectrophotometric (AAS) method for the determination of tin in canned foods. The 5 foods evaluated were meat, pineapple juice, tomato paste, evaporated milk, and green beans, each spiked at 2 levels. The concentration range of tin in the samples was 10-450 micrograms/g, and each level was sent as a blind duplicate. Statistical treatment of results revealed no laboratory outliers and 6 individual or replicate-total outliers, accounting for 3.3% of the data. Repeatability (within-laboratory) coefficient of variation (CVo) ranged from 2.2 to 48%, depending on the tin level and food evaluated. For samples containing greater than or equal to 80 micrograms/g of tin, repeatability CV averaged 5.6% including outliers and 3.7% after their rejection. Overall among-laboratories coefficient of variation (CVx) varied from 3.3 to 58%; at levels greater than or equal to 80 micrograms/g, it averaged 7.3% with outliers and 5.3% after their rejection. Recovery of tin, based on spiking levels, ranged from 100.0 to 112.8% and averaged 105.4%. Detection limit range is 2-10 micrograms/g, and lower quantitation limit is 40 micrograms/g. This method has been adopted official first action.

Acetylene↗
PubMedDate not supplied

Determination of low nanogram/millilitre levels of volatile organic compounds in on-purpose and by-product hydrochloric acids.

Hydrochloric acid (HCl) is used in the food industry as a processing aid in the manufacture of certain foods. HCl is manufactured, either directly from inorganic sources, i.e. "on-purpose' or indirectly as a by-product from the production of organic compounds generally intended for non-food applications. By-product HCl potentially may contain traces of the manufactured product, its precursors, and other reaction by-products. Many of the potential contaminants are volatile organic compounds (VOCs) such as vinyl chloride and benzene. A study was conducted to determine whether there were differences between the levels of VOCs found in HCl samples collected from two on-purpose HCl manufacturers and two by-product HCl manufacturers. Process water used to manufacture the HCl also was analysed. Twenty-nine VOCs were determined by purge- and-trap concentration and capillary gas chromatography/mass spectrometry. Of these, nine were found in the process water and in both the by-product and on-purpose HCl samples at total VOC levels of less than 116 ng/ml. The levels of total VOCs identified in the two on-purpose HCl samples were 58 and 80 ng/ml; the levels of total VOCs identified in the two by-product samples were 41 and 115 ng/ml. The process water appeared to be the source of most of the contaminants. These results show that the levels of VOCs found in the two types of acid are comparable.

Food Handling↗
PubMed1990

Gas chromatography of tryptophan together with other amino acids in hydrochloric acid hydrolysates.

The classical hydrolysis of proteins with hydrochloric acid using tryptamine [3-(2-aminoethyl)indole] as additive revealed that tryptophan can be measured without destruction together with other amino acids by gas chromatography. An extensive study was made to establish the optimum conditions for protein hydrolysis (time and temperature of hydrolysis, amount of tryptamine) and for the derivatization of amino acids. The amino acid contents (including tryptophan) of standard proteins such as lysozyme, bovine and human albumin, human gamma-globulin, casein and alpha-chymotrypsin and protein matrices (meat and fish meals, sunflower) were determined, after hydrochloric acid hydrolysis (4 h, 145 degree C) in the presence of tryptamine. as N, O, (S)-trifluoroacetyl isobutyl esters with SE-30 as the stationary phase. The reproducibility of the measurements was 4.6% (relative standard deviation) or less.

Amino Acids↗
PubMed1993

[Method of simultaneous determination of sulfuric acid and hydrochloric acid in the air of the workplace].

The paper discusses a method for simultaneous determination of sulfuric and hydrochloric acid in the workplace atmosphere. The air samples were collected on the Whatman filter impregnated with 0.2 mol/l sodium carbonate solution. The acids were determined by the turbidimetric method: sulfuric acid with barium chloride and hydrochloric acid with silver nitrate.

Air Pollutants, Occupational↗
PubMed1977

The effect of the synthetic prostaglandin analog 15 (R) 15 methyl-PGE2 methyl ester on gastric mucosal hemorrhage induced in rats by taurocholic acid and hydrochloric acid.

The incidence of mucosal hemorrhage induced in rats by the oral administration of taurocholic acid (TCA) and hydrochloric acid (HCl) both singly and in combination was investigated. The effect of prostaglandin 15 (R) 15 methyl-PGE2 methyl ester (Me-PGE2) on the occurrence of hemorrhage induced by TCA with HCl was also studied. The incidence of hemorrhage induced by TCA (10 mM) alone and HCl (160 mM) alone was minimal and not different from that induced by the control solution. The combination of TCA (10 mM) and HCl (160 mM) produced bleeding in 67.7% of animals. The addition of 15 (R) 15 methyl-PGE2 methyl ester (9.9 micronM, corresponding to 50 microng/Kg) significantly reduced the incidence of hemorrhage induced by the combination of TCA with HCl from 67.7% to 31.3%. This suggests that this synthetic prostaglandin may be of value in conditions thought to be associated with reflux of bile into the stomach.

Animals↗
PubMed1998

Substitution of acetic acid for hydrochloric acid in the bicarbonate buffered dialysate.

In a multicenter study including 5 dialysis units, blood acetate changes during 4 h dialysis sessions in 141 patients treated with a 4 mM acetate-containing bicarbonate dialysate (ABD) were evaluated and compared to the values of 114 patients using an acetate-free bicarbonate dialysate (AFD). Acetate-free bicarbonate dialysate was delivered by a dialysis machine from the mixing with water for dialysis of a 1/26.2 bicarbonate concentrate, and a 1/35 acid-concentrate in which acetic acid was substituted for hydrochloric acid (Soludia, Fourquevaux, France). This new type of dialysate was routinely in use for 3 years on average (range, from 2 to 5 years). All patients fasted before and during dialysis. Blood samples were withdrawn at the start and at the end of dialysis sessions. The acetate plasma concentration was determined using the acetyl-CoA synthetase enzymatic method (Boehringer, Manheim, Germany). In patients treated with ABD whose predialysis blood acetate levels were in the physiologic range of < or = 100 microM (n = 113), the acetate plasma concentration increased from a predialysis mean value of 22+/-3 microM to a postdialysis mean value of 222+/-11 microM in 88 patients (78% of patients) whereas the acetate plasma concentration changes remained in the range of physiologic values from 21+/-6 to 58+/-7 microM in the other 25 patients. In contrast, patients treated with AFD whose predialysis blood acetate levels were in the physiologic range (n = 108), acetate plasma concentration increased from a predialysis mean value of 49+/-6 microM to 160+/-19 microM in only 13 patients (12% of patients) whereas acetate plasma concentration changes remained in the range of physiologic values of 23+/-2 to 41+/-3 microM in most of the patients of this group. In this study, a significant number of patients, whether receiving standard or acetate-free bicarbonate dialysates, exhibited an extremely high acetate plasma concentration at the start of the dialysis session. Hyperacetatemia was controlled with AFD in patients whose predialysis acetate plasma concentration of 316+/-82 decreased to 55 +/-23 microM (n = 6) at the end of the dialysis session whereas the acetate plasma concentration remained high when the predialysis concentration was 580+/-76 microM, with a postdialysis concentration of 233+/-39 microM (n = 28). It is concluded that in patients whose predialysis blood acetate levels were in the physiologic range, acetate-containing bicarbonate dialysate induces hyperacetatemia whereas postdialysis blood acetate remains in the normal range in such dialysis patients treated with acetate-free dialysate. Chronic hyperacetatemia, which could be found in dialysis patients, is well controlled by dialysis using an acetate-free dialysate.

Acetate-CoA Ligase↗
PubMed1994

Echographic evaluation with image analysis of irritant reactions induced by nonanoic acid and hydrochloric acid.

Skin reactions to 40% nonanoic acid in propanol (NON) and to 4% hydrochloric acid were evaluated by image analysis of 20 MHz B scan recordings (Dermascan C, Cortex Technology). 18 women, aged 18 to 45, were patch tested with 24-h application time, and clinical and instrumental evaluations were performed at the beginning of the experiment, and 24 and 48 h after patch testing. To check possible regional variations in reactivity to NON and HCl, both substances were applied 2 x on the same forearm. As control tests, saline solution, propanol and sodium lauryl sulfate (SLS) 3% were applied. Echographic images were processed by a program enabling numerical representation of picture data, based on attribution of fictional values to the echoes' amplitudes, selection of amplitude bands of interest, binary transformation of the image, and calculation of the extension of areas reflecting within the same amplitude range. Sonographic recordings were evaluated by an amplitude interval marking hyporeflecting parts of the dermis (corresponding to edema and inflammatory infiltration), and by a band highlighting the entrance echo (epidermis). Our evaluations showed that extension of the hypoechogenic area of the dermis increases according to intensity of inflammatory reaction for all irritant substances. A clear decrease in reflectivity of the epidermis echo at 24 h was visible at SLS patch test test sites, whereas at patch test sites performed with NON and HCl, there was a trend towards an increase in values of hyperreflecting pixels. No significant variations between data recorded at proximal compared to distal skin sites were observed for NON and HCl. In conclusion, the echographic technique provides a method for quantification of the dermal inflammatory reaction, and also for description of skin reactions induced by irritant substances, according to their specific epidermal effects.

Adolescent↗
PubMed1982

A rapid method for acid hydrolysis of protein with a mixture of trifluoroacetic acid and hydrochloric acid.

Proteins have regions which resist hydrolysis with mineral acid. The presence of a strong organic acid was found to be efficient for hydrolysis of a hydrophobic peptide bond. The proposed condition, a 2:1 (by vol.) mixture of concentrated hydrochloric acid and trifluoroacetic acid at 166 degrees C for 25 min was observed to be equivalent to the conventional conditions (6 M HCl at 110 degrees C for more than 24 h) without significant decomposition of amino acids. The method was shown to be superior to the conventional conditions, especially for hydrophobic proteins. The present method destroys tryptophan, as the conventional acid hydrolysis does.

Acetates↗
PubMed1988

Effect of ruminal infusion of glucose, volatile fatty acids and hydrochloric acid on mineral metabolism in sheep.

Two experiments were conducted to study the effects of alterations in ruminal pH and volatile fatty acid (VFA) concentrations on utilization of Mg and other minerals. In Exp. 1, two metabolism trials were conducted with 12 ruminally cannulated crossbred wethers fed 800 g/d of orchard-grass (Dactylis glomerata, L.) hay. After each feeding, wethers were ruminally infused with 500 ml (4.2 ml/min) or either 1) deionized water, 2) 40% (w/v) glucose solution, 3) .26 M propionic and .17 M butyric acid solution or 4) .35 M HCl. The pH of the VFA solution was adjusted to 6.8 with 10N NaOH. In Exp. 2, a metabolism trial was conducted with 12 ruminally cannulated crossbred wethers fed 600 g of orchard-grass hay and infused with a buffered VFA solution prepared as in Exp. 1 or with an unbuffered solution. In both experiments each trial consisted of a 5-d adaption period followed by four 5-d collections of feed, feces and urine. Compared with the glucose treatment, infusion of the buffered VFA solution produced similar acetic and propionic and higher (P less than .05) butyric acid concentrations (Exp. 1). The HCl solution produced changes in ruminal and pH values similar to those of the glucose infusion. In Exp. 1, apparent absorption of Mg was increased over twofold by the glucose infusion (P less than .05), but the other infusions had no effect. Apparent absorption of P was decreased (P less than .05) by HCl infusion, and K absorption was decreased by HCl and glucose infusions. In Exp. 2, infusion of the unbuffered VFA solution decreased apparent Mg absorption by 15.7%, compared with infusion of the buffered solution. These experiments suggest that the increased Mg absorption observed with carbohydrate supplementation is not due to alterations in ruminal pH or VFA levels.

Animals↗
PubMed1989

Reactions of hydroxyamino acids during hydrochloric acid hydrolysis.

Chlorosubstitution reactions occur readily during HCl hydrolysis of delta- and epsilon-hydroxynorleucines (Hnle), the products of deamination of poly-L-lysine by nitrite at low pH. During amino acid analysis, chloronorleucines elute as new peaks after delta- and epsilon-Hnle. To determine if other hydroxyamino acids undergo similar changes during hydrolysis, they were subjected individually to HCl hydrolysis conditions with and without added phenol. Amino acid analyses indicated that terminal hydroxy groups on linear side chains undergo reactions during HCl hydrolysis; the products appear as new peaks which may be chloroderivatives. In contrast, no new peaks are observed in HCl hydrolysates of delta-hydroxylysine or amino acids with beta-hydroxy groups (beta-hydroxynorvaline, serine, and threonine). Phenol did not protect linear amino acids from reactions during HCl hydrolysis but did prevent loss of the cyclic amino acids tyrosine, hydroxyproline, and 3,4-dihydroxyphenylalanine. Although the gamma-hydroxy group of homoserine would be expected to undergo reaction, HCl catalyzes its cyclization to form homoserine lactone instead.

Amino Acids↗