A comparative study of AgX (X = Cl(-), Br(-), I(-) and N(3)(-)) solid-phase reactors for flow-injection determination of cyanide in electroplating wastewater.

In this study, a rapid flow injection-flame atomic absorption spectrometry for cyanide detection was developed. Different AgX (where X is Cl(-), Br(-), I(-) and N(3)(-)) solid-phase reagents (SPR) were tested for indirect determination of cyanide. In a single-line FIA system, the cyanide was allowed to react with AgX SPR, which in turn changed Ag ions in AgX to silver cyanide complexes in a sodium hydroxide carrier stream. The eluent containing the analyte as silver cyanide complexes was measured by FAAS. The calibration curve was linear up to 30 mg l(-1) with a detection limit of 0.05 mg l(-1) for cyanides. The sampling rate and the relative standard deviation were <1.09% and >200 h(-1), respectively. The method was applied to the determination of cyanide in electroplating wastewater.     

o-Dianisidine: a new reagent for selective spectrophotometric, flow injection determination of chlorine.

A flow injection analysis (FIA) procedure for the determination of free chlorine in industrial formulations and water samples is proposed. The manifold is provided with a gas-diffusion unit which permits the removal of interfering species and also the preconcentration of chlorine. The determination of chlorine is performed on the basis of the oxidation by o-dianisidine as a chromogenic reagent to a coloured product which can be monitored at 445 nm. The method (for a preconcentration step of 60 s) is linear over the range 0.04-1.00 mg l(-1) of chlorine, the limit of detection is 0.04 mg l(-1), the reproducibility of the procedure (as RSD of the slope) is 3.7% for a series of four independent calibrations, the precision (as RSD of a series of 30 continuous FIA peaks of 0.56 mg l(-1) of chlorine) is 1.4% and the sample throughput is 40 h(-1). A detailed comparative study of the analytical characteristics of a single mono-channel reverse FIA assembly and the same system but provided with a Fluoropore membrane filter of 0.5 microm pore size was performed to check the advantages of the new approach in terms of sensitivity, selectivity and limit of detection.     

Determination of iodide by derivatization to 4-iodo-N,N-dimethylaniline and gas chromatography-mass spectrometry

A real-time determination of iodide is proposed which involves the oxidation of iodide with 2-iodosobenzoate in the presence of N,N-dimethylaniline. The reaction is completed within 1 min to yield 4-iodo-N,N-dimethylaniline, which is extracted in cyclohexane and determined by GC-MS. It was also possible to determine iodine by derivatization in the absence of 2-iodosobenzoate, and iodate by its reduction with ascorbic acid to iodide and subsequent derivatization. A rectilinear calibration graph was obtained for 0.02-50 micrograms l-1 iodide with a correlation coefficient of 0.9998. The limit of detection was 8 ng l-1 iodide. The method was applied to the determination of iodate in iodized table salt and free iodide and total iodine in sea-water, and to spiked samples when the recovery was in the range 96.8-104.3% (RSD 1.9-3.6%). A sample clean-up by solid-phase extraction with a LiChrolut EN cartridge is proposed.     

Flow injection-spectrophotometric determination of metoclopramide hydrochloride

The determination of metoclopramide hydrochloride is spectrophotometrically determined by the Bratton-Marshall method in a flow injection assembly. The required nitrite is prepared on-line in the flow assembly by reducing a nitrate solution with the aid of a copperised cadmium solid-phase reactor. The calibration graph is linear over the range 0.5-85 mg l(-1), with a relative standard deviation (RSD) of 0.89%, and sample throughput of 51 samples h(-1). The method is easy and simple, and it is applied to determination of metoclopramide in some pharmaceutical formulations. The method eliminates the need for frequent preparation of unstable nitrite solutions.     

Fluorimetric determination of phytic acid based on the activation of the oxidation of 2,2'-dipyridyl ketone hydrazone catalysed by Cu(II)

Phytic acid exerts an activation effect on the oxidation of 2,2'-dipyridyl ketone hydrazone catalysed by Cu(II) ion and the oxidation product is highly fluorescent. A fixed time method for the fluorimetric determination of phytic acid based on this effect is described. The calibration graph is linear over the range 0.05-0.6 mg l-1 phytic acid, resulting in a limit of detection of 0.03 mg l-1 phytic acid. The relative standard deviation is in the range 1.4-1.8%, depending on the sample analysed. The method was successfully applied to the determination of phytic acid in human urine (20 samples) and food samples (nine different products). The results obtained for urine samples ranged from 0.31 to 3.6 mg l-1 phytic acid and for food samples from 3.8 to 22 mg g-1 phytic acid. This is the first procedure to be reported for the determination of phytic acid based on fluorimetric measurements.     

Spectrophotometric determination of iron with ferrozine by flow-injection analysis

Two methods for the determination of iron by normal FIA and reversed FIA were developed using sodium 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine-4',4'-disulphonate (ferrozine). The reagent formed a chelate with Fe(II) in hexamethylentetramine buffered medium at pH 5.5. In one previous reaction coil Fe(III) was reduced to Fe(II) by ascorbic acid and in the other reaction coil the complexation reaction was developed. The linear range of the determination was 0.5-6 and 0.1-5 mug ml(-1) of iron for normal FIA and reversed FIA respectively. The proposed method was sensitive (detection limit 0.012 and 0.010 mug ml(-1)), rapid and reproducible (RSD 0.3 and 0.28%). The method was satisfactorily applied to the determination of iron in waste water, toadstool tissue, potato leaves, human hair and bauxites at a sampling rate of 90 and 50 samples h(-1) for normal FIA and reversed FIA respectively.     

Flow injection analysis with in-line solid phase extraction for the spectrophotometric determination of sulfonated and unsulfonated Quinoline Yellow in Cologne

An integrated solid-phase spectrophotometry/ FIA method is proposed for the determination of the synthetic colorant matter Quinoline Yellow (QYWS) in the presence of its unsulfonated derivative QYSS. The procedure is based on the retention and preconcentration of the low level QYSS on a C-18 silica gel minicolumn, followed by sequential measurement of its absorbance at lambda = 410 nm after its elution with methanol. The applicable concentration range, the detection limit and the relative standard deviation were the following: for QYWS, from 0.10 to 30.0 mg L(-1); 0.013 mg L(-1); and 0.6%; and for QYSS, between 10 and 1.000 microg L(-1); 2 microg L(-1); and 1.3%, respectively. The method was applied to the determination of small amounts of QYSS present in QYWS in Colognes. Percentages of recovery between 98% and 99% were obtained in all instances. The method was also satisfactorily applied to the determination of these compounds in samples of commercial Colognes comparing the results for QYWS with those offered by an HPLC reference method and also validating the results chemometrically.     

Mechanised flow system for on-line microwave digestion of food samples with off-line catalytic spectrophotometric determination of cobalt at ng l-1 levels

A mechanised system for on-line slurry food sample digestion was developed and an off-line cobalt determination was performed. The stabilised slurry sample was introduced into an air carrier stream until reaching the digestion coils located inside a household microwave oven. Software written in Visual Basic 3.0 was developed to permit the transport of the slurry samples and the programming of the microwave oven and also the control of the mineralization valve. The proposed system was optimized for determination of cobalt in certified samples such as mussels, bovine liver and fish and also uncertified fish samples. The digestion parameters were established as 3 mol l-1 HNO3 for mussels, 3 mol l-1 HNO3 plus 0.16% v/v H2O2 for bovine liver and 12 mol l-1 HNO3 for fish employing maximum power for 5 min of microwave actuation. In the subsequent spectrophotometric method for the catalytic determination of cobalt, the Tiron and hydrogen peroxide concentrations were 1.8 x 10(-3) and 3.0 x 10(-4) mol l-1, respectively, and the sample residence time was 300 s as determined by an optimisation process. The proposed method features a linear range from 10 to 200 ng l-1 Co (r > 0.996) with detection and quantification limits of 1.7 and 5.5 ng l-1 Co, respectively. The precision, expressed as RSD, was 2.4% (n = 12) for repeatability and 5.2% (n = 10) for reproducibility and the accuracy of the proposed method was assessed by using certified samples and an alternative technique (ETAAS).     

Fluorimetric determination of fluoride in a flow assembly integrated on-line to an open/closed FIA system to remove interference by solid phase extraction

A simple flow injection fluorimetric method for fluoride determination is proposed. The method is based on the enhanced fluorescence of quercitin-Zr(IV) complex when fluoride ion is present in the sample. An open/closed FIA manifold with a mini-column of Dowex 50W X8 resin was used to remove the most important interference (aluminum). The two FIA assemblies were integrated on-line to automate the pretreatment of the water sample and fluoride determination. The calibration graph was linear over the range 0.1-3.0 mug ml(-1) of fluoride with a correlation coefficient of 0.999 and LOD 0.06 mug ml(-1). The relative standard deviation was 2.5% and the sample throughput was 52 h(-1) without pretreatment and 10 h(-1) with pretreatment of the sample. The method was applied to the determination of fluoride in water samples.     

Gran's plot titration and flow injection titration of sulfate in ground and drinking water with a barium ion-selective electrode

The application of a barium ion-selective electrode for the determination of sulfate is reported. Titrations in the batch mode using the Gran's plot method [1] have been carried out. In the presence of a lithium acetate buffer and after the addition of isopropanol it has been possible to determine sulfate with a relative standard deviation (RSD) of 1.5%. The concentration range of the samples was 5–400 mg sulfate/l. Interfering ions were separated by cation-exchange. This indirect titration constituted the basis of a flow injection titration (FIA titration) system for the continuous determination of sulfate. By plotting the peakwidth vs. the logarithm of the sulfate concentration of the injected samples, linear calibration graphs in the range of 50–200 mg sulfate/l were obtained. In this system, the sample stream was pumped through an ion-exchange column, mixed with a buffer stream of lithium acetate and injected in a reagent stream of a BaCl₂ solution. The resulting free Ba(II) concentration was monitored with a barium ion-selective electrode. The content of sulfate in ground and drinking water samples has been determined with a RSD between 1.2% and 1.3%.     

Flow injection spectrophotometric determination of cyanide by the phenolphthalin method

The phenolphthalin method for the determination of cyanide has been modified and adapted to a continuous flow system based on the flow injection principle. Aqueous cyanide samples are injected into a carrier stream (0.001 M NaOH), which is then merged with the combined reagent stream of phenolphthalin and carbonate buffer (pH 10.3), and the mixture is passed through an on-line cupric sulfide packed column. The resulting phenolphthalein (the oxidized form of phenolphthalin) is measured in a flow-through spectrophotometer at 552 nm, to determine the cyanide content. The chemical factors and flow injection analysis (FIA) variables influencing the system are discussed. The calibration graph is linear from 0.6 to 4.3 ppm cyanide. At a sampling rate of about 70 samples h(-1) with 50 mul sample injections, precision was about 1% relative S.D.     

Evaluation of headspace solid-phase microextraction for the analysis of volatile carbonyl compounds in spirits and alcoholic beverages

A method was developed for the determination of C1-C6 carbonyl compounds in alcoholic solutions using pentafluorobenzoxymation followed by headspace sampling solid-phase microextraction and subsequent analysis by GC with electron-capture detection. Experimental conditions-alcohol content, exposure time, temperature and sample agitation were optimised. In this method, a spirit or distilled alcoholic beverage is first adjusted to 20% (v/v) alcohol. Detection limits for particular aldehydes and ketone varied from 0.05 to 0.5 microg/l and relative standard deviation was between 2.3 and 20%. Generally, the method showed good linearity for the tested concentration range 8 microg/l-0.32 mg/l with regression coefficients ranging between 0.9434 and 0.9983. The method was applied to the analysis of real alcoholic beverages (vodkas).     

Simultaneous determination of inulin and p-aminohippuric acid (PAH) in human plasma and urine by high-performance liquid chromatography

Inulin and p-aminohippuric acid (PAH) clearances are used for the estimation of glomerular filtration rate (GFR) and effective renal plasma flow (ERPF). A simple and rapid high-performance liquid chromatography (HPLC) method with UV detection is described for the simultaneous determination of inulin and PAH in the same chromatogram in the plasma and urine of humans. Plasma and urine samples were hydrolyzed with perchloric acid (0.7%) in boiling water. The mobile phase consisted of 0.01 M potassium dihydrogenphosphate with 0.02 M tetramethylammonium chloride and o-phosphoric acid (pH 3)-acetonitrile (94:6, v/v), pumped at a rate of 1.2 ml min-1 on a C8 reversed-phase column. Tannic acid was used as the internal standard and UV detection at 285 nm was employed. The calibration curves were linear over the concentration range of 12.5-100 mg l-1 for inulin and 6.25-50 mg l-1 for PAH with determination coefficients greater than 0.997. The method is accurate (bias < 13%) and reproducible (intra- and inter-day relative standard deviation less than 11%), with a limit of quantitation of 12.5 mg l-1 and 6.25 mg l-1 for inulin and PAH, respectively. Analytical recoveries from urine and plasma were ranged from 81 to 108% for both compounds. This fully validated method, which allows the simultaneous determination of inulin and PAH clearances, is simple, rapid (total run time < 10 min) and requires only a 200 microliters plasma or urine sample.     

Fluorescence determination of the pesticide asulam by flow injection analysis.

This paper presents the analytical determination of the pesticide Asulam based on its native fluorescence. The method was optimized in either a flow injection analysis (FIA) assembly or in batch. The maximum fluorescence intensity was observed for basic pH solutions and at a lamda(ex) of 258 nm and a lamda(em) of 342 nm. The influence of different empirical parameters, such as the pH, the presence of surfactants, solvent polarity or solved oxygen amount, was studied. The calibration range was fitted with a linear equation from 0.01-3 mg l(-1) Asulam and 0.005-15 mg l(-1) Asulam for batch and continuous-flow, respectively. The RSD for both procedures was 1.0%. After testing the influence of a large series of potential interferents, the method was applied to water samples from different locations.     

Application of Ag2X (X = SO3, Cr2O7, C2O4 and CO3) solid-phase reagents for indirect determination of cyanide in the industrial effluent using FIA-FAAS system

Four solid-phase reagents have been tested for indirect determination of cyanide using flow injection analysis-flame atomic absorption spectrometry (FIA-FAAS). The method is based on insertion of aqueous cyanide solutions into an on-line Ag₂X (where X are SO₃²⁻, Cr₂O₇²⁻, C₂O₄²⁻ and CO₃²⁻) packed column (25%, m/m suspended on silica gel beads) and re-distilled water or sodium hydroxide are used as the carrier stream. The eluent containing the analyte as silver cyanide complexes, produced from reaction between Ag₂X and cyanide, measured by flame atomic absorption spectrometry. The method is simple, fast and selective than other published FIA procedures. A relative standard deviation (R.S.D.) better than 1.12% was obtained in a repeatability study. The method was applied to the determination of cyanide in industrial electrolytic baths.     

Determination of aliphatic amines in air by on-line solid-phase derivatization with HPLC-UV/FL

An easy, rapid, and efficient method using on-line solid-phase derivatization in HPLC is developed for the trace determination of aliphatic amines in air. Some fundamental studies on stop-flow, on-line, solid-phase derivatizations in HPLC are also investigated, such as optimization of the reaction detection HPLC system and band broadening. Air is sampled with silica gel tubes from different sites, including sewage areas, fish cleaning and processing rooms, and an organoleptic lab of the U.S. Food & Drug Administration (FDA). The trapped amines are desorbed with an acidic aqueous-organic solution, followed by pH adjustment of the eluates to pH 10. The resulting solution is directly injected into an on-line, precolumn, solid-phase derivatization and reversed-phase HPLC-UV/FL system, not requiring any further sample workup steps. The percent derivatizations are as high as 88 +/- 5% (n = 3) for primary amines, and 75 +/- 4% (n = 3) for diethylamine under optimized conditions (60 degrees C for 10 min). The recoveries for all amines are above 90%. The method is validated by a single-blind, spiked experiment with 1.1-4.4% relative standard deviation (RSD) in the range of 15-47 ppm. These results are confirmed by a GC-FID method performed in another lab. Amines are quantitated via calibration plots, with final concentrations from 0.02 to 0.38 mg/m3 air. It is suggested that this newer approach for the determination of amines and polyamines, using polymeric solid-phase reagents on-line, precolumn in HPLC, should prove generally successful for other amines and other sample types in the future.     

液相色谱法测定环氧氯丙烷工业中间体中的己二酸

建立了液相色谱仪测定环氧氯丙烷工业中间体中己二酸含量的方法。样品采用甲醇-10mm01／L磷酸缓冲液（体积比5：95）溶液提取,C18固相萃取柱净化,紫外检测器检测,外标法定量。己二酸在100～2000mg／L范围内线性良好,相关系数大于0．9999,按10s／Ⅳ计算,己二酸定量限为25．0mg／kg。添加回收率为91．1％～112．2％．测定结果的相对标准偏差为4．7％～7．9％（n=5）。该方法简单快速,回收率高,重现性好,满足工业分析要求。     

Flow injection analysis for residual chlorine using Pb(II) ion-selective electrode detector

A simple flow injection analysis (FIA) system for residual chlorine in tap water has been developed by using a Pb(II) ion-selective electrode (ISE) detector. The method is based on a specific response of the Pb(II)-ISE to residual chlorine. The FIA system consists of a millivolt meter, a peristaltic pump, a Pb(II)-ISE detector and a recorder. A linear working curve between peak height and concentration of residual chlorine was obtained from 0.1 to 1 mg l(-1) for the developed FIA system. The relative standard deviation for repeated injections of a 0.2 mg l(-1) residual chlorine sample was 2%. The regression line and its correlation factor between the conventional o-tolidine colorimetric method and the present method were Y=0.75X+0.17 and 0.967, respectively, for this determination.     

FIA-FT-IR determination of ibuprofen in pharmaceuticals

A method has been developed for the determination of Ibuprofen (2-[4-isobutylphenyl]-propionic acid) in pharmaceuticals by FT-IR, using the carbonyl band which this compound presents at 1710 cm(-1) in carbon tetrachloride solutions. Samples are dissolved in carbon tetrachloride. In this solvent the excipients are not soluble and so the drug can be directly determined without any additional treatment. The use of a simple FIA manifold permits one to carry out this analysis with a low consumption of reagent and the FT-IR provides a continuous monitoring of the spectral base-line which permits an accurate determination of the maximum in the absorbance band. Also, the FIA system permits easy and fast sampling and cleaning of the measurement cell. The method has a dynamic range between 0.5 and 20 mg/ml with a sensitivity of 0.366 +/- 0.004 au . mg(-1) . ml . mm(-1) and a variation coefficient of 0.8% for 5 independent measurements of a real sample containing 200 mg of Ibuprofen per capsule. The developed procedure provides concentration values comparable with those found by UV spectrophotometry in the analysis of real samples but is free from matrix interferences.     

Determination of ammonium in Kjeldahl digests by gas-diffusion flow-injection analysis with a bulk acoustic wave-impedance sensor

A novel flow-injection analysis (FIA) system has been developed for the rapid and direct determination of ammonium in Kjeldahl digests. The method is based on diffusion of ammonia across a PTFE gas-permeable membrane from an alkaline (NaOH/EDTA) stream into a stream of diluted boric acid. The trapped ammonium in the acceptor is determined on line by a bulk acoustic wave (BAW)-impedance sensor and the signal is proportional to the ammonium concentration present in the digests. The proposed system exhibits a favorable frequency response to 5.0 x 10(-6)-4.0 x 10(-3) mol l(-1) ammonium with a detection limit of 1.0 x 10(-6) mol l(-1), and the precision was better than 1% (RSD) for 0.025-1.0 mM ammonium at a through-put of 45-50 samples h(-1). Results obtained for nitrogen determination in amino acids and for proteins determination in blood products are in good agreement with those obtained by the conventional distillation/titration method, respectively. The effects of composition of acceptor stream, cell constant of conductivity electrode, sample volume, flow rates and potential interferents on the FIA signals were discussed in detail.