Sensitive and selective determination of molybdenum by flow injection chemiluminescence method combined with controlled potential electrolysis technique

A sensitive and selective flow injection chemiluminescence (CL) method combined with controlled potential electrolysis technique was described for the determination of molybdenum. The method is based on the chemiluminescence reaction of luminol with unstable molybdenum(III) in alkaline solution. The molybdenum(III) was on-line reduced from molybdenum(VI) via controlled potential electrolysis technique using a homemade flow-through carbon electrolytic cell at the potential of −0.6 V (versus Ag/AgCl). The method allows the determination of molybdenum in the 5.0×10⁻¹⁰ to 5.0×10⁻⁷ g ml⁻¹ range with a limit of detection (3σ) of 5×10⁻¹¹ g ml⁻¹ molybdenum. The relative standard deviation is 2.6% for the 1.0×10⁻⁹ g ml⁻¹ molybdenum solution in 11 repeated measurements. This method was successfully applied to the determination of molybdenum in water samples.     

流动注射时间扫描荧光分析法测定青霉素V钾

研究了H2SO4颜色反应用于青霉素V钾(PMPP)荧光测定的新方法。PMPP为弱荧光物质,与浓H2SO4反应后荧光显著增强。结合流动注射进样技术,借助时间扫描荧光方式,提出了流动注射时间扫描荧光分析法测定PMPP的新方法。在最大激发236.0 nm、最大发射波长306.0 nm处,PMPP在3.6×10-5g/L~4.0×10-2g/L范围内与荧光强度呈良好的线性关系,相关系数为0.9999。方法检出限为1.0×10-5g/L,相对标准偏差为0.6%(n=11,ρ=1.0×10-3g/L),进样量为0.18 mL。方法已用于药物及尿样中PMPP的测定。     

Improved method for shipboard determination of iron in seawater by flow injection analysis

A flow injection analysis (FIA) catalytic spectrophotometric method for the determination of dissolved iron in seawater was further developed to yield a more sensitive assay with a low detection limit. The method employs an initial sample acidification step followed by an iron pre-concentration step involving an in-line 8-hydroxy-quinoline (8-HQ) metal-chelating resin column. The copper capacity and elution efficiency, as well as the iron FIA performance of three trace-metal clean resins were compared, resulting in the selection of a clean silica gel support for the 8-HQ ligand. The concentrated sample is eluted from the resin with an acidic carrier and mixed with reagents, initiating an iron-catalyzed, color-forming reaction. Increasing the reaction temperature from 18 to 30 °C doubled the sensitivity; reaction temperature control was necessary to obtain good reproducibility in the field. Reagent blanks were as low as 0.05 nM and a detection limit of 0.016 nM was obtained from three times the S.D. of a 0.06 nM seawater sample repeated six times. A 0.06 nM detection limit was calculated from shipboard experiments where total dissolved iron was determined for 10 different samples from the same station. The instrumental sensitivity and precision evolved to the point where the blank associated with the technique is the major factor influencing its detection limit.     

Flow injection potentiometric determination of clobutinol hydrochloride

New clobutinol (Clob) ion-selective polyvinyl chloride (PVC) membrane electrodes, based on the ion-associates of Clob with phosphotungstic acid or phosphomolybdic acid were prepared using dibutyl phthalate as plasticizing solvent. The electrodes were characterized in terms of membrane composition, temperature and pH. The sensors showed a near-Nernstian response over the concentration ranges (6.31 × 10⁻⁶)-(1.00 × 10⁻²) and (5.01 × 10⁻⁵)-(1.00 × 10⁻²) M in the case of clobutinol-phosphotungstate ((Clob)₃-PT) applying batch and flow injection (FI) analysis, respectively, and (1.58 × 10⁻⁵)-(1.00 × 10⁻²) and (5.01 × 10⁻⁵)-(1.00 × 10⁻²) M in case of clobutinol-phosphomolybdate ((Clob)₃-PM) for batch and FI analysis systems, respectively. The electrodes were successfully applied for the potentiometric determination of ClobCl in pharmaceutical preparation and urine in steady state and flow injection conditions. The electrodes exhibit good selectivity for Clob with respect to a large number of inorganic cations, sugars and amino acids.     

Flow injection potentiometric sensor for determination of phenylpropanolamine hydrochloride

A new polymeric membrane electrode has been constructed for the determination of phenylpropanolamine hydrochloride. The electrode was prepared by solubilizing the phenylpropanolamine-phosphomolybdate ion associate into a polyvinyl chloride matrix plasticized by dibutylphthalate as a solvent mediator. The electrode showed near-Nernstian response over the concentration range of 1 × 10^?5–1 × 10^?2 M with low detection limit of 6.3 × 10^?6 M. The electrode displays a good selectivity for phenylpropanolamine with respect to a number of common inorganic and organic species. The electrode was successfully applied to the potentiometric determination of phenylpropanolamine ion in its pure state and its pharmaceutical preparation in batch and flow injection conditions.     

New flow injection potentiometric graphite coated ion-selective electrode for the determination of VO ions

A new coated ion-selective electrode for the determination of trace vanadyl ions (VO²⁺) by flow injection potentiometry (FIP) with a home-made flow cell has been developed. The PVC-based membrane was coated on a graphite electrode with an effective area of 4.90 mm². The optimum membrane contains 5 wt.% 1,8-diaminonaphtalene as ionophore, 35 wt.% plasticizer 2-nitrophenyl octyl ether, 55 wt.% PVC and 5 wt.% additive potassium tetrakis (p-chlorophenyl) borate. The electrode in flow injection potentiometry resulted in well defined peaks for vanadyl ions with a very high sampling rate (180 injections/h). Linear calibration was obtained from 1.14×10⁻⁷ to 1.14×10⁻¹ M vanadyl ions, with a slope of 28.3±0.3 mV per decade change in vanadyl concentration, and very low detection limit of 1.14×10⁻⁷ M and the electrode can be used for at least 1 months without any considerable change in potential response. Selectivity coefficients for several ions were obtained by the matched potential method with respect VO²⁺ ions. The flow cell is simple to construct and free from memory effect problems over long periods of use. The sensor was used for the recovery of trace VO²⁺ ions from tap water and the determination of VO²⁺ in synthetic sample.     

流动注射化学发光法测定佐米曲谱坦

在碱性条件下,佐米曲谱坦对鲁米诺-K3[Fe(CN)6]化学发光体系有较强的抑制作用,据此建立了佐米曲谱坦的流动注射化学发光分析法。该法的化学发光抑制值ΔI与佐米曲谱坦质量浓度在2.0×10-6~1.2×10-4g/mL范围内,呈良好的线性关系,检出限为7.6×10-7g/mL。对2.5×10-5g/mL佐米曲谱坦测定的相对标准偏差为1.2%(n=11)。方法适用于佐米曲谱坦片中佐米曲谱坦的测定。     

流动注射化学发光法测定那格列奈

在碱性介质中,那格列奈对Luminol-H2O2体系的化学发光有很强的抑制作用,据此建立了流动注射化学发光抑制法测定那格列奈的新方法.该法的化学发光抑制值△I与那格列奈的质量浓度在2.0×10-8～1.0×10-6 g/mL范围内,呈良好的线性关系,检出限为1.4×10-8 g/mL;对4.0×10-7 g/mL那格列奈连续进行11次平行测定,相对标准偏差为1.0%;通过对荧光光谱的研究,对机理进行了初步探讨.     

A clean method for flow injection spectrophotometric determination of cyclamate in table sweeteners

A flow system based on the multicommutation is proposed for fast and clean determination of cyclamate. The procedure exploits the reaction of cyclamate with nitrite in acidic medium and the spectrophotometric determination of the excess of nitrite by iodometry. The flow system was designed with a set of solenoid micro-pumps to minimize reagent consumption and waste generation. The detection limit was estimated as 30 μmol L⁻¹ (99.7% confidence level) with linear response ranging up to 3.0 mmol L⁻¹. The coefficient of variation was estimated as 1.7% for a solution containing 2.0 mmol L⁻¹ cyclamate (n = 20). About 60 samples can be analyzed per hour, consuming only 3 mg KI and 1.3 μg NaNO₂, and generating 2.0 mL of effluent per determination, thus providing an environmentally friendly alternative to previously proposed procedures. Common artificial and natural sweeteners did not interfere when present in concentrations 10-times higher than cyclamate. The procedure was successfully applied for determination of cyclamate in artificial table sweeteners with results in agreement with the reference method at the 95% confidence level.     

流动注射化学发光法测定褪黑素

在强碱性介质中,铁氰化钾可直接氧化褪黑素产生化学发光。基于此,建立了一种测定褪黑素的流动注射化学发光分析方法。线性范围为1.9×10-6~2.3×10-4g/mL,检出限为5×10-7g/mL,该法已用于药物中褪黑素的测定。     

快速化学发光联用流动注射技术测定西咪替丁

在NaOH-NaHCO3介质中,铁氰化钾氧化西咪替丁产生快速化学发光反应,0.5 s后发光达到最大,2 s后迅速衰减至零。本文结合流动注射技术,建立了一种化学发光测定西咪替丁的新方法。针对这一快速发光反应,设计了与之相应的管路系统和最短的反应管道来捕捉最大化学发光信号,发光强度与西咪替丁质量浓度在5×10-7~1×10-4g/mL范围内呈线性关系,检出限为1.1×10-7g/mL。对5×10-6g/mL西咪替丁进行11次平行测定,相对标准偏差为1.8%。本法已用于西咪替丁片剂的测定。     

Construction and performance characterization of ion-selective electrodes for potentiometric determination of phenylpropanolamine hydrochloride applying batch and flow injection analysis techniques

New phenylpropanolamine hydrochloride (PPA.Cl)-selective electrodes of the conventional polymer membrane type, based on incorporation of phenylpropanolamine-tetraphenylborate (PPA-TPB) ion-pair or phenylpropanolamine-phosphotungstate (PPA-PT) ion-associate in a poly(vinyl chloride) (PVC) membrane plasticized with dioctylphethalate (DOP) or dibutylphethalate (DBP), have been constructed. The electrodes were fully characterized in terms of the membrane composition, temperature, and pH. The electrodes were applied to the potentiometric determination of PPA.Cl in pure solutions and in pharmaceutical preparations under batch and flow injection conditions. The sensors showed fast, stable, and Nernstian slope over the concentration ranges 1.0×10⁻⁵ to 8.91×10⁻³ M and 10⁻⁵ to 10⁻² M in the case of PPA-TPB applying batch and flow injection analysis (FIA), respectively, and 5.01×10⁻⁶ to 1.25×10⁻³ M and 10⁻⁵ to 10⁻² M in the case of PPA-PT for batch and FIA systems, respectively. The electrodes exhibited good selectivity for PPA.Cl with respect to a large number of inorganic cations, sugars, amino acids, and components other than phenylpropanolamine of the mixed drugs. The effect of temperature on the electrodes was also studied.     

鲁米诺-铁氰化钾化学发光体系测定双嘧达莫

在碱性条件下,铁氰化钾氧化鲁米诺产生化学发光,双嘧达莫对该体系的化学发光有显著的增强作用。基于此并结合流动注射技术建立了测定双嘧达莫的新方法。该方法检出限为5.7×10-11g mL(IUPAC),线性范围为1.0×10-10～5.0×10-8g mL,对5.0×10-9g mL双嘧达莫平行测定11次,其相对标准偏差为1.9%。     

A novel spectrophotometric method for batch and flow injection determination of sulfite in beverages

A novel spectrophotometric assay method for batch and flow injection determination of sulfite in beverages is described. The method involves a reaction with diaquacobyrinic acid heptamethyl ester (diaquacobester, DACbs) in acetate buffer of pH 3 to form a highly stable sulfite cobester complex (SO₃Cbs). In the absence of sulfite, the reagent displays three absorption maxima at 349, 409 and 525 nm. Addition of sulfite is associated with the development of a new absorption band at 313 nm, an increase in the intensity of the band at 425 nm and a decrease in the absorbance of the bands at 349 and 525 nm. Variations of the absorptions at 313, 349, 425 and 525 nm are linearly proportional to sulfite concentrations over the range of 0.05–25 μg ml⁻¹with a detection limit of 0.01–0.2 μg ml⁻¹. Negligible interferences are caused by most common ions. Validation of the method according to the quality assurance standards shows suitability for quality control assessment of sulfite in complex matrices without prior treatment. The method has the advantages of high selectivity, good sensitivity, fast reaction, high stability of the reagent and reaction product and absorbance measurements at four different wavelengths in the same run. The method is successfully applied to determine the sulfite contents of some beverages. The results compare fairly well with data obtained using the standard method.     

Design of a flow injection method for chlorophyll determination in in vitro plants

A flow injection (FIA) method was designed for the determination of chlorophylls a and b in small in vitro Dieffenbachia maculata “Sublime” plants. In the first step, the pigments from spinach leaves were separated, purified by solvent extraction and freeze–dried, to obtain standards for the FIA optimization. The sample extraction procedure was optimized. Four solvents were tested: diethyl ether, methanol, acetone and ethanol. The ethanol 96% was the optimal solvent for FIA purposes. It allows to the efficient extraction of the pigments and water can be used as carrier. The best FIA conditions found for the quasi-simultaneous quantification of chlorophylls a and b were a flow rate of 10.84 mL min⁻¹, a sample injection volume of 1.45 mL and a reactor length of 63 cm. The detection was performed with the automatic wavelength scanning Cintra 10e spectrometer, at 649 and 665 nm. The results obtained by the FIA method were compared to those obtained by the Arnon method. A deviation less than 5% was found between results for both methods. The concentration (mg g⁻¹) of chlorophylls a and b during three periods of the plants (in vitro, acclimatization, and adult) was determined to evaluate the whole in vitro procedure. It was found an increment of both pigment concentrations since the in vitro step till the adult stage, while the chlorophylls a to b ratio decreases. The designed method is suitable especially for the determination of the pigments at low concentrations in small samples with appropriate analytical quality.     

Kalman滤波流动注射化学发光法同时测定铂钯的研究

利用Luminol H2O2 OP Pt(Pd)化学发光新体系以及Kalman滤波化学计量学方法建立了流动注射化学发光法同时测定铂钯的新方法。方法的检出限:铂为2.2×10-8g mL、钯为2.4×10-8g mL,铂钯相对标准偏差分别为0.9%和3%。采用阳离子交换树脂静态吸附分离,消除贱金属离子的干扰。可用于贫铂矿中铂、钯的同时测定。     

流动注射化学发光法测定DL-酪氨酸

在甲醛存在下 ,高锰酸钾与DL 酪氨酸能够发生化学发光反应 ,产生很强的化学发光。据此采用流动注射技术 ,建立了一种测定DL 酪氨酸的化学发光分析法。方法的检出限为 2 .9× 1 0 - 8g/mL ,相对标准偏差为 1 .5 % ( 1 .0× 1 0 - 6g/mLDL 酪氨酸 ,n =1 1 ) ,线性范围为 1 .0× 1 0 - 7g/mL～ 5 .0× 1 0 - 6g/mL。     

On-line flow injection solid sample introduction, leaching and potentiometric determination of fluoride in phosphate rock

A flow injection method with on-line solid sample dissolution was developed for the determination of fluoride in phosphate rock. The fluoride was selectively leached (98-102.4 % recovery) from a 50-mg powdered phosphate rock sample with 0.50 M citric acid. Using the zone sampling technique the fluoride in the buffered leachate was determined by injecting 87 μL into the carrier stream using a fluoride ion-selective electrode detector. The sensing element of the electrode was housed in a home-made sleeve-type flow-through cell. On-line solid sample digestion with 0.50 M citric acid at 55 °C resulted in minimum dissolution of interfering iron and aluminum ions with improved accuracy and calibration linearity. The incorporation of relatively high level of fluoride in the carrier stream (40 μg mL⁻¹) facilitated the determination of high levels of fluoride in phosphate rock (up to 4.1%) with out the need for excessive on-line dilution.The optimized flow system was applied for the determination of fluoride in phosphate rocks samples and a reference material at a rate of nine samples per hour with a relative standard deviation (n = 5) of 2.95-4.0 %. Comparison of the proposed flow injection method with the standard method, which involves steam distillation from sulfuric acid solution and manual titration with thorium nitrate, showed no evidence of bias at the 95% confidence level.     

A novel spectrophotometric method for batch and flow injection determination of cyanide in electroplating wastewater

A sensitive and highly selective spectrophotometric method is described for the determination of cyanide. It is based on a reaction of cyanide with aquacyanocobyrinic acid heptamethyl ester (ACCbs) reagent (orange color) at pH 9.5 to give dicyanocobester (DCCbs) (violet color). The increase of the absorption bands of the reaction product at 368 and 580 nm and the decrease of the reagent band at 353 nm are linearly proportional to the cyanide concentration. The method is used in static mode for determining cyanide over the concentration range 0.04-1.20 μg ml⁻¹ with a detection limit of 0.02 μg ml⁻¹ and for hydrodynamic analysis of 0.4-5.2 μg ml⁻¹ cyanide. Application for batch and flow injection monitoring of cyanide in electroplating wastewater samples gives results agree within ± 1.2% with those obtained by the standard potentiometry using the cyanide ion selective electrode. The method is practically free from interferences by PO₄³⁻, NO₃⁻, NO₂⁻, SO₄²⁻, F⁻, Cl⁻, Br⁻, I⁻, S²⁻ and SCN⁻ ions and gives results with average recoveries of 97.6-99.2%. Advantages offered by using ACCbs as a chromogen for cyanide assay are: (i) high selectivity and sensitivity of the coordination site of the reagent towards cyanide ion; (ii) fast reaction, since legation takes place at the axial position of the reagent; (iii) good solubility and stability of the reagent in aqueous solutions over a wide pH range; (iv) high stability of the reagent (ACCbs) and the colored complex product (DCCbs) and (v) possible absorbance measurements at three different wavelengths.     

鲁米诺-铁氰化钾流动注射化学发光法测定头孢拉定

在碱性介质中,铁氰化钾氧化鲁米诺产生化学发光,头孢拉定对该体系有显著的增强作用。基于此并结合流动注射技术建立了测定头孢拉定含量的化学发光新方法。该法线性范围为0.16~160 mg/L,检出限为0.028 mg/L;对80 mg/L的头孢拉定进行平行测定11次,其相对标准偏差为0.99%。用本法对胶囊中头孢拉定进行测定,并初步探讨了该化学发光的反应机理。