A simple vapour phase decomposition (VPD) of quartz powder in a polypropylene vessel and determination of phosphorus by spectrophotometry

A simple, low pressure, low temperature vapour phase decomposition (VPD) of quartz powder has been developed for the determination of phosphorus. A platinum dish containing the quartz or silicon powder was placed inside a polypropylene vessel containing 40 ml of 1:1 mixture of HF and HNO(3). After capping the vessel, the entire assembly was heated on a water bath at approximately 90 degrees C for 8 h. The platinum dish was removed from the vessel, the sample solution was treated with 0.5 ml of H(2)SO(4) and 0.5 ml of HClO(4) and was heated on a hot plate till HClO(4) fumed out. The resultant solution was diluted to 40 ml ( approximately 0.4N), analysed for phosphorus by spectrophotometry as an ion-pair of molybdophosphate with crystal violet. Phosphorus contamination by reagents has been drastically reduced (around 250 times) compared to the conventional dissolution procedure. The optimum reaction conditions were [H(+)]=0.42N, [H(+)]/Mo=62 for the formation of molybdophosphate and its extraction into n-butyl acetate. No interferences due to fluoride, silicate (active silica) and arsenic (V) upto 6.7x10(3),2.7x10(3) and 2.0x10(3) times the content of phosphorus, respectively were observed. The LOD was found to be 0.066 mug g(-1) (+/-3 s). RSD is 0.4-2.3% and the molar absorptivity is 2.7x10(5) l mole(-1) cm(-1).     

Interaction between peroxide ion and phenol group which are coordinated to the same iron(III) ion

We have prepared several new iron(III) complexes with ligands which contain a phenol group; these are tetradentate [(X-phpy)H, X and H(phpy) represent the substituents on the phenol ring and N,N-bis(2-pyridylmethyl)-N-(2-hydroxybenzyl)amine, respectively] and pentadentate ligands [(R-enph-X)H; R=ethyl(Et) or methyl(Me) derivative and H(Me-enph) denotes N,N-bis(2-pyridylmethyl)-N″-methyl-N″-(2″-hydroxyl-benzylamine)ethylenediamine] and have determined the crystal structures of Fe(phpy)Cl₂, Fe(5-NO₂-phpy)Cl₂, and Fe(Me-enph)ClPF₆, which are of a mononuclear six-coordinate iron(III) complex with coordination of one or two chloride ion(s). These compounds are highly colored (dark violet) due to the coordination of phenol group to an iron(III) atom. When hydrogen peroxide was added to the solution of the iron(III) complex, a color change occurs with bleaching of the violet color, indicating that oxidative degradation of the phenol moiety occurred in the ligand system. The bleaching of the violet color was also observed by the addition of t-butylhydroperoxide. The rate of the disappearance of the violet color is highly dependent on the substituent on the phenol ring; introduction of an electron-withdrawing group in the phenol ring decreases the rate of bleaching, suggesting that disappearance of the violet band should be due to a chemical reaction between the phenol group and a peroxide adduct of the iron(III) species with an η¹-coordination mode and that in this reaction the peroxide adduct acts as an electrophile towards phenol ring. The intramolecular interaction between the phenol moiety and an iron(III)-peroxide adduct may induce activation of the peroxide ion, and this was supported by several facts that the solution containing an iron(III) complex and hydrogen peroxide exhibits high activities for degradation of nucleosides and albumin.     

碘酸钾滴定法测定分银渣中的锡含量

采用碘酸钾滴定法测定分银渣中的锡含量。试样用过氧化钠熔融,水浸酸化,加铁粉过滤除杂质;加铝片还原,待反应平静后加热煮沸至冒大泡,冷却至室温;以淀粉为指示剂,碘酸钾滴定至淡蓝色为终点。对试样进行11次平行测定,相对标准偏差(RSD)小于1.2%,加标回收率在99%~101%。方法流程短,除杂质效果好,结果准确。     

Determination of femtomole concentrations of catecholamines by high-performance liquid chromatography with peroxyoxalate chemiluminescence detection.

A highly sensitive method for determination of the plasma catecholamines, norepinephrine (NE), epinephrine (E) and dopamine (DA) is described. The method consists of the extraction of the catecholamines, using 3,4-dihydroxybenzylamine as internal standard, from plasma with alumina (5 mg), followed by a reversed-phase column separation, on-column fluorogenic derivatization with ethylenediamine (ED) and post-column peroxyoxalate chemiluminescent reaction detection utilizing bis[4-nitro-2-(3,6,9-trioxadecyl-oxycarbonyl)phenyl] oxalate (TDPO) and hydrogen peroxide. In order to optimize the reaction conditions for high-performance liquid chromatography to obtain highly sensitive detection, the effects of changing reagent compositions on the chemiluminescence yield were investigated. The following are the optimized conditions. Eluent, a mixture of 50 mmol l-1 potassium acetate (pH 3.20)-50 mmol l-1 potassium phosphate (pH 3.20)-acetonitrile (90.15 + 4.85 + 3 v/v/v) containing 1 mmol l-1 sodium hexanesulfonate (40 degrees C) and flow rate, 0.5 ml min-1. Fluorogenic reagent solution, 105 mmol l-1 ED and 175 mmol l-1 imidazole in acetonitrile-ethanol (90 + 10 v/v) and flow rate, 0.25 ml min-1. Reaction coil (15 m x 0.5 mm i.d.) heated at 80 degrees C. Chemiluminogenic reagent solution, 0.25 mmol l-1 TDPO, 150 mmol l-1 hydrogen peroxide and 110 mmol l-1 trifluoroacetic acid in dioxane-ethyl acetate (50:50 v/v) and flow rate, 1.4 ml min-1. The detection limits for all the catecholamines were 1 fmol (signal-to-noise ratio at 2). The standard deviations of the method for the determination of NE, E and DA added to rat plasma (2.5 nM) were 3, 3 and 4%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Determination of phenol, m-, o- and p-cresol, p-aminophenol and p-nitrophenol in urine by high-performance liquid chromatography

A method for the biological monitoring of human exposure to aromatic hydrocarbons, nitrocompounds, amines and phenols has been developed. Phenol, cresols, p-aminophenol, p-nitrophenol and their glucorono- or sulpho-conjugates, were quantified by HPLC; 4-chlorphenol was added as internal standard. After enzymatic hydrolysis, the free compounds were extracted with an organic solvent and analyzed by an isocratic HPLC Perkin Elmer system at ambient temperature and at a flow-rate of 1 ml/min. The column was a reversed-phase Pecosphere 3 x 3 C18 Perkin Elmer; the mobile phase was a 30:70:0.1 (v/v/v) methanol-water-orthophosphoric acid mixture and the chromatogram was monitored at 215 nm. Identification was based on retention time and quantification was performed by automatic peak height determination, corrected for the internal standard. The recovery was ca. 95% for phenol and cresols; 90% for p-nitrophenol; 85% for p-aminophenol; the coefficients of variance were less than 6% within analysis (n = 20) and less than 10% between analysis (n = 20). The detection limits, at a signal/noise ratio of 2, were 0.5 mg/l for phenol and cresols and 1 mg/l for p-aminophenol and p-nitrophenol.     

Mechanism of Phenol Hydroxylation with Hydrogen Peroxide Catalyzed by Iron Complex Oxide

Dihydroxybenzene are both very important chemical products. The oxidation of phenol to produce catechol and hydroquinone has been researched extensively since the 1970s. In this paper, the iron complex oxide was prepared by the air oxidation of aqueous suspension method and the catalytic activities were investigated in the hydroxylation of phenol with H₂O₂ to catechol and hydroquinone. The results showed that the catalyst had higher catalytic activities and the phenol conversion could reach 24% when the phenol/H₂O₂ (mole ratio) was 3 and the catechol/hydroquinone (mole ratio) 1.5 in products. Furthermore, the interaction of the catalyst with H₂O₂ had also been demonstrated by IR spectrometry. In the presence of H₂O₂ a band at 956 cm^-1 appeared and disappeared when the H₂O₂ is replaced by H20 or the catalyst was heated over 373 K, at which temperature decomposition of iron peroxide was very likely. The band at 956 cm^-1 was due to the formation of structure of iron peroxide species and the stretching vibration of surface 0-0 species. The results of IR studies suggested that the catalyst might be react with hydrogen peroxide to form iron peroxide, which decomposed to produce·OOH radical. In the presence of DMPO (5,5-dimethyl-1-pyrroline-N-oxide) the·OH radical was also successfully captured in the hydroxylation of phenol by H₂O₂ over iron complex oxide catalyst in the first time that has been confirmed by means of ESR spectrometry. The results of ESR suggested the process of hydroxylation of phenol with H₂O₂ was probably a radical process. A possible mechanism of the catalytic process was proposed.     

Coprecipitation with metal hydroxides for the determination of beryllium in seawater by graphite furnace atomic absorption spectrometry

Coprecipitation first with magnesium hydroxide, next with tin(IV) hydroxide is developed for the determination of traces of beryllium in sea-water. To a 200-ml sample is added a sodium hydroxide solution to form magnesium hydroxide at pH 11.5, on which beryllium is quantitatively coprecipitated. The precipitate is separated by centrifugation and dissolved in 2 ml of 12 mol/l hydrochloric acid. The resulting solution (ca. 10 ml) is mixed with 2 mg of tin (IV) carrier and the pH is adjusted to 5.0 to collect the beryllium on tin (IV) hydroxide, leaving magnesium ions in the solution. The tin (IV) hydroxide is centrifuged, dissolved in 0.1 ml of 5 mol/l hydrobromic acid, and then diluted to 1 ml with water. Magnesium is so added as to be 500 g/ml for increasing the sensitivity about four times, and the beryllium in the solution is determined by graphite furnace atomic absorption spectrometry. The experiments with synthetic seawater samples showed that pg — g amounts of beryllium can be coprecipitated on the metal hydroxides and beryllium at the low ng/1 level can be determined with reasonable precision (RSD < 10%). The detection limit of the proposed method is 0.5 ng/l of beryllium in seawater.     

Determination of methylmercury and inorganic mercury in whole blood by headspace, cryofocusing gas chromatography and atomic absorption spectrometry

A method for the determination of different mercury species in whole blood is described. Inorganic mercury (InHg) was determined in 2 ml of standard solutions or blood samples using head space (HS) injection coupled to atomic absorption spectrometry (AAS) after treatment with concentrated sulfuric and tin(II) chloride as a reductant agent in a closed HS vial. After stirring, the InHg was converted to elementary mercury and carried with a nitrogen flow through a quartz cell heated at 200 degrees C and the absorbance signal was evaluated by AAS. For the determination of methylmercury (MeHg), 2 ml of a standard solution or a blood sample were treated with 10 mg of iodoacetic acid and 0.4 ml of concentrated H2SO4. Then, the MeHg species were HS-injected into a gas chromatograph (GC), separated on a semicapillary column (AT-1000) with a flow of helium, then carried to the quartz cell heated at 1000 degrees C and detected by AAS. The high content of salts in blood samples, where sodium chloride is the major component (0.14 mol l-1), affected the gas-liquid distribution coefficient of both mercury species in the HS vial. A linear calibration graph was obtained in the ranges 1-20 and 1-125 micrograms Hg l-1 added as InHg and MeHg, respectively. The detection limits for InHg and MeHg were 0.6 and 0.2 microgram Hg l-1, respectively. The relative standard deviations for eleven independent measurements were 5% for both mercury species. Recovery values ranging from 98 to 106% for InHg and from 95 to 105% for MeHg and from 93 to 95% for ethylmercury (EtHg) were obtained. The accuracy of the proposed method was also established by the analysis of certified whole blood samples for InHg and MeHg. No difference between the sum of these two species determined by our procedure and the recommended total mercury concentrations in the certified samples was observed. Results for the determination of MeHg and InHg in 30 controls and 30 dentists are presented to illustrate the practical utility of the proposed method.     

Isolation and determination of volatile organic sulphur compounds in aqueous solutions

Summary A procedure has been worked out for isolation and determination of volatile organic sulphur compounds in water. These compounds are isolated from an aqueous sample by countercurrent thin-layer head-space (TLHS) technique. After isolation, the sulphur compounds are burned in a quartz tube and the combustion products (SO₂/SO₃ mixture) are absorbed by a 10% solution of hydrogen peroxide. The resulting sulphuric acid is introduced into the heated part of a quartz tube, where the presence of tungsten trioxide at 1150°C ensures its complete decomposition. The sulphur dioxide formed is titrated microcoulometrically with iodine. Organic halogen compounds usually present in different waters do not interfere. The complete procedure has been tested on model solutions of sulphur compounds in the concentration range of 10–200 g S/l.     

Hydroxylation of benzene in the system vanadium(V)-hydrogen peroxide-acetic acid

Hydroxylation of benzene in acetic acid at 323 K was studied in the presence of a sodium orthovanadate catalyst. With hydrogen peroxide as aqueous solution, the yield of phenol was 12–14%. With hydrogen peroxide generated from dry sodium peroxide, the yield of phenol could be improved to 21–23%. The apparent decomposition rate constants of hydrogen peroxide in acetic acid are presented.     

Determination of fenpyroximate in apples by supercritical fluid extraction and packed capillary liquid chromatography with UV detection

A method using off-line supercritical fluid extraction (SFE) and micro liquid chromatography (μLC) with UV detection at 260 nm, was developed for selective determination of fenpyroximate in apple samples. The packed capillary liquid chromatography method utilises 20 μl injection volumes with on-column focusing. A 350×0.32 mm capillary column packed with Kromasil 100-C₁₈ of 5 μm particle size was used with a mobile phase of acetonitrile–10 mM ammonium acetate (85:15, v/v) at a flow of 5 μl/min. A two-step SFE procedure was used to extract fenpyroximate selectively in 2 g apple samples, with Hydromatrix (HMX) added as a water absorbent at a 1:1 (w:w) ratio. Fenpyroximate was extracted at 200 bar and 90°C for 15 min using carbon dioxide at a flow of 2 ml/min, and solvent trapping collection in 10 ml acetonitrile. The volume of the acetonitrile extract was reduced by evaporation and water was added to a final composition of acetonitrile–water (40:60, v/v). The resulting 2.0 ml solution was filtered using a 0.45 μm poly(vinylidene difluoride) syringe filter before μLC analysis. Validation of the method was accomplished with apple samples spiked with fenpyroximate, covering the range of 0.1 to 1.0 μg/kg. The within-day and between-day repeatabilities were in the range 4–18% relative standard deviation. Accuracy, measured as recovery, was found to be approximately 60%. Apple samples from a field treated with fenpyroximate were analysed. None of the samples contained fenpyroximate above the quantification level.     

Analysis of Plasma Diethyldithiocarbamate–A Metabolite of Disulfiram

Abstract

A reversed-phase high-performance liquid chromatographic analysis was developed for diethyldithiocarbamate in plasma. Following treatment of plasma (1 ml) with methyl iodide (250 μl), biphenyl (internal standard, 1.8 μg) was added in chloroform (6 ml). After shaking (30 min.), the chloroform was separated and evaporated under nitrogen (to 50 μl). Acetonitrile (250 μl) was added and the solution was again evaporated under nitrogen (to 100 μl). Aliquots (25 μl) were chromatographed using acetonitrile: acetate buffer (65:35, pH 4) at 2.5 ml/min on a 5 micron C-8 column with detection at 276 nm. Recovery of methyldiethyldithiocarbamate (MeDDC) was 92.5 ± 3.2%. Retention times and theoretical plates for MeDDC and biphenyl were 3.0 and 4.6 min., and 4660 and 6336 respectively. The analysis was linear over the range 25 to 400 ng/ml with a coefficient of variation of 3.2%. Analysis of samples after intravenous disulfiram (10 mg) administration to rats yielded a total body clearance of 343 ml/min. This supports the view that metabolism is principally by extra-hepatic routes.     

高效液相色谱-串联质谱法同时测定废水中18种酚类污染物

建立了上清液直接进样-高效液相色谱-串联质谱同时测定废水中18种酚类污染物的分析方法。取5.0 mL水样置于具塞离心管中,加氨水调节pH≥12,摇匀,加入1.0 mL二氯甲烷-正己烷(2: 1, v/v)混合溶液并振摇5 min, 4000 r/min离心5 min,用玻璃针筒抽取上清液并经0.22 μ m聚四氟乙烯滤膜过滤,用甲酸调节水样pH至中性;然后采用Thermo Hypersil ODS柱(100 mm×2.1 mm, 5.0 μ m)分离,以甲醇-0.01 mol/L甲酸铵-甲酸水溶液(pH 4.0)为流动相进行梯度洗脱,流速0.2 mL/min,柱温30℃,进样10 μ L,电喷雾负离子电离(ESI^-)模式、多反应监测(MRM)模式进行检测,外标法定量。18种酚类化合物的峰面积与其质量浓度在一定浓度范围内均呈良好的线性关系(r²≥0.9991),方法检出限为0.10~0.88 μ g/L。测定低、中、高加标浓度的样品,18种酚类化合物的相对标准偏差为2.5%~9.9%(n=6);火工药剂废水与石油化工废水样品中的平均加标回收率为68.7%~118%(n=3)。此方法操作简单,灵敏度高,干扰小,分析速度快,可适用于环境废水中18种酚类污染物的同时分析。     

Analysis of buprenorphine and its N-dealkylated metabolite in plasma and urine by selected-ion monitoring

A selected-ion monitoring method was developed for determination of buprenorphine and its N-dealkylated metabolite (norbuprenorphine) in human plasma and urine. N-Propylnorbuprenorphine was added as internal standard to 2-3 ml of sample and the alkaloids were extracted with toluene-2 butanol at pH 9.4. After back-extraction in dilute sulphuric acid, the compounds were heated at 110 degrees C. This procedure led to quantitative loss of methanol followed by ring formation between the 6-methoxy group and the branched side-chain of all compounds. The derivatives were extracted into dichloromethane-2-butanol and treated with pentafluoropropionic anhydride. The resulting derivatives were suitable for selected-ion monitoring analysis. The coefficient of variation was found to be 4.5% at 5 ng/ml and 8.9% at 50 ng/ml in urine. The corresponding values for plasma were 6.2% and 5.3%, respectively. The lower limit of detection in plasma was 150 pg/ml, permitting analysis of plasma levels of buprenorphine for 24 h and urine levels of buprenorphine and norbuprenorphine for more than seven days after a therapeutic dose of buprenorphine. This method is the first with sufficient specificity and sensitivity for characterization of the clinical pharmacokinetics of buprenorphine.     

Evaluation of luminol-H(2)O(2)-KIO(4) chemiluminescence system and its application to hydrogen peroxide, glucose and ascorbic acid assays

A novel chemiluminescence (CL) system was evaluated for the determination of hydrogen peroxide, glucose and ascorbic acid based on hydrogen peroxide, which has a catalytic-cooxidative effect on the oxidation of luminol by KIO(4). Hydrogen peroxide can be directly determined by luminol-KIO(4)-H(2)O(2) CL system. The detection limit was 3.0x10(-8) mol l(-1) and the calibration graph was linear over the range of 2.0x10(-7)-6.0x10(-4) mol l(-1). The relative standard deviation of H(2)O(2) was 1.1% for 2.0x10(-6) mol l(-1) (N=11). Glucose was indirectly determined through measuring the H(2)O(2) generated by the oxidation of glucose in the presence of glucose oxidase at pH 7.6. The present method provides a source for H(2)O(2), which, in turn, coupled with the luminol-KIO(4)-H(2)O(2) CL reaction system. The CL was linearly correlated with glucose concentration of 0.6-110 mug ml(-1). The relative standard deviation was 2.1% for 10 mug ml(-1) (N=11). Detection limit of glucose was 0.08 mug ml(-1). Ascorbic acid was also indirectly determined by the suppression of luminol-KIO(4)-H(2)O(2) CL system. The calibration curve was linear over the range of 1.0x10(-7)-1.0x10(-5) mol l(-1) of ascorbic acid. The relative standard deviation was 1.0% for 8.0x10(-7) mol l(-1) (N=11). Detection limit of ascorbic acid was 6.0x10(-8) mol l(-1). These proposed methods have been applied to determine glucose, ascorbic acid in tablets and injection.     

Spectrophotometric determination of osmium based on its catalytic effect on the oxidation of carminic acid by hydrogen peroxide

A highly sensitive spectrophotometric method is described for the determination of trace amounts of osmium(VIII), based on its catalytic effect on the oxidation of carminic acid by hydrogen peroxide. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of carminic acid at 540 nm after 3 min of mixing the reagents. The optimum reaction conditions were 1x10(-4) mol l(-1) carminic acid, 0.013 mol l(-1) hydrogen peroxide and pH 10 at 25 degrees C. By using the recommended procedure, the calibration graph was linear from 0.1 to 1.5 ng ml(-1) of osmium; the detection limit was 0.02 ng ml(-1); the RSD for five replicate determinations of 0.2-1.4 ng ml(-1) was in the range of 1.8-4.7%. The influence of several foreign ions on osmium determination were studied and the effect of interfering ions were removed by extracting osmium into isobuthyl methyl ketone and back extracting into sodium hydroxide solution.     

Enhanced spectrophotometric determination of chromium (VI) with diphenylcarbazide using internal standard and derivative spectrophotometry

In the present work, erioglaucine A was applied as internal standard to enhanced spectrophotometric determination of chromium (VI) with diphenylcarbazide. The following procedure was used: (1) addition of internal standard and formation of ion pairs of Cr (VI) with benzyltributylammonium bromide (BTAB) (sample volume 100 ml), (2) extraction to 10 ml of methylene chloride, (3) evaporation in nitrogen stream, and (4) redissolution in a micro-volume with addition of diphenylcarbazide for color development (final volume 200 mul). The preconcentration factor achieved was about 400 and it was shown that, using internal standard, the analytical errors due to sample treatment were reduced. The analytical signals for chromium and internal standard were obtained at 591.30 and 653.50 nm from first derivative spectra, normalized against (1)D(653.50nm). The analytical characteristics evaluated were: detection limit = 0.06 mug l(-1), quantification limit = 0.19 mug l(-1), precision for 1 mug l(-1) 14.2%, and for 10 mug l(-1) 3.2%, correlation coefficient of linear regression was 0.9985. The proposed procedure was applied to determination of chromium (VI) in tap water. Total chromium was determined by electrothermal atomic absorption spectrometry, the recovery of hexavalent chromium added was then evaluated and compared with the results of the proposed procedure. In this experiment, good agreement was obtained between results obtained by the two methods.     

La détermination du vanadium par la méthode spectrophotométrique en solution non-aqueuse

On mixing small quantities of an aqueous solution of vanadium, containing hydrogen peroxide and acidified with HCl, with anhydrous dioxan containing gaseous hydrogen chloride in molar concentration, an intense red-yellow colour appears, in the presence of as little as 5 μg/ml vanadium.If a drop of salicylic aldehyde is added to the solution thus obtained, the colour changes to violet-blue, which shows an absorption maximum at 565 mμ, clearly visible even with 1 μg/ml vanadium.This reaction, though a sensitive method for the detection of vanadium, is not suitable for quantitative measurement of this substance because the small quantity of water introduced in the form of the vanadium solution hydrolyses the coloured compounds.Very good results can be obtained by dissolving the dry residue (at 100°C) of the solution under examination in 0.2 ml of N HCl in 2% aqueous H₂O₂ solution, and then in 5 ml of a solution made up of 40% acetic anhydride containing gaseous HCl (1 N), 40% glacial acetic acid, and 20% methyl Salicylate.By this method as little as 1 μg of vanadium can be determined.Co, Mo, and W, interfere; the other elements do not.     

The separation of platinum, palladium and gold from silicate rocks by the anion exchange separation of chloro complexes after a sodium peroxide fusion: an investigation of low recoveries

A series of experiments was undertaken to measure the recovery efficiency of platinum, palladium and gold from silicate rocks using a sodium peroxide fusion followed by anion exchange separation of the analytes as chloro complexes. Results obtained by graphite furnace atomic absorption spectrometric analysis of standard solutions prepared in dilute HCl or HCl-acidified sodium peroxide solution showed that recoveries were near quantitative. However, when standard solutions were added to an alkaline sodium peroxide solution, which was then acidified, low results were obtained for platinum and gold (46% and 76% respectively). Low and variable results were also obtained when standard solutions were added to a peridotite sample that had been dissolved by the state procedure, and in the analysis of the South African Bureau of Standards certified reference material, SARM 7. Various experiments were undertaken to investigate these low recoveries, but the reason proposed here is the formation of hydroxychloro compounds in alkaline solution which are not, on acidification with HCl, converted quantitatively to the chloro complex necessary for quantitative anion exchange separation. It is concluded that a sodium peroxide fusion followed by an anion-exchange separation does not appear to form the basis of a successful technique for the determination of platinum, palladium and gold in silicate rocks.     

Monitoring the removal of carbonate from alkali metal hydroxide solutions using gas diffusion flow injection

Monitoring the removal of carbonate from alkali metal hydroxide (MOH, M = K, Na) solutions with calcium oxide (CaO) was studied using a newly developed method for the determination of trace amounts of total carbonate (TC) in alkaline solutions based on a flow injection (FI) technique coupled with a gas diffusion system. The optimized conditions of the FI system were as follows: the flow rate of each carrier, reaction solution (H2SO4) and receptor solution (Cresol Red, pH 8.9) was 0.25 ml min(-1), the sample size was 0.1 ml and the concentration of H2SO4 in the reaction solution was 0.09 M. The limit of detection of TC by the proposed method was 4 x 10(-7) M. The removal efficiency of carbonate was affected by the amount of CaO added, the shaking time of the solutions and the concentration of MOH. For 1 M NaOH and KOH solution, the removal efficiency of carbonate was about 99% and the concentration of residual carbonate was 4 x 10(-5) and 1.2 X 10(-4) M, respectively, when the amount of CaO added was 2 g l(-1) and the shaking time was 16 h.