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In this work, we present for the first time, a simplified fabrication of a laminated paper-based analytical device (LPAD) with a free-mobile app, Palette Cam, for image analysis. A filter paper is cut in a rectangular shape (9 × 3 cm) and placed between a top laminating sheet with punched holes and a bottom laminating sheet. The holes allow accessibility of liquid on the paper. Thermal lamination is then employed to complete the fabrication of LPAD. Our simplified design reduces a tedious alignment of small pieces of paper to the holes. We demonstrated the LPAD with an analysis of salicylic acid in pharmaceutical products. Each 4 μL of ferric reagent and sample was dispensed on the LPAD. Smartphone was used to capture images. The RGB (red green blue) color intensity from the Palette Cam was converted into a logarithm color ratio. Our LPAD is simplified, cost-effective and able to be a portable device.

Fluorescent polymer nanocomposites of silsesquioxane cage-based anthracene (An-PSQ) and pyrene (Py-PSQ) were obtained by cross-linked polymerization of octavinylsilsesquioxane (OVS) with 9,10-dibro...

This work presents two simple methods for estimating the firing distance from the gunshot residues (GSRs) on fabric targets. Four types of fabric targets, namely twill weave denim cotton-polyester (80/20), jersey knitting 100% cotton, plain weave cotton-polyester (80/20) and plain weave cotton-polyester (60/40), were employed. The firing tests were carried out using these white fabrics as targets at distances of 5–100 cm, respectively. In the first method, digital images of the black GSRs on fabric materials were recorded inside an illuminated box and the inverted gray intensity values were plotted against the firing distances. Since the plots of all fabrics are not significantly different, the estimation of firing distance employs the same exponential curve for all test fabrics. Although simple, the imaging method is not suitable for dark-colored materials. A chemical-based method was therefore developed as an alternative method. In the second method, a small disposable microfluidic paper-based analytical device (μPAD) was employed for detecting Pb(II) extracted from the GSRs. The μPAD method uses the measurement of the length of a narrow band of a pink color resulting from reaction between rhodizonate reagent and the Pb(II) extract. The plots indicated that the data of thick denim material are significantly different to other test fabrics which are much thinner. These three fabrics share the same estimation curve. However, it is recommended that the separate estimation curve for denim materials must be used. Both methods are suitable for short range firing distance, no further than 60 cm, since at greater distances the inverted gray intensity and the ‘band-length’ methods are unable to detect the GSRs.

This work presents a simple and innovative protocol employing a microfluidic paper-based analytical device (µPAD) for equipment-free determination of mercury. In this method, mercury (II) forms an ionic-association complex of tetraiodomercurate (II) ion (HgI42−(aq)) using a known excess amount of iodide. The residual iodide flows by capillary action into a second region of the paper where it is converted to iodine by pre-deposited iodate to liberate I2(g) under acidic condition. Iodine vapor diffuses across the spacer region of the µPAD to form a purple colored of tri-iodide starch complex in a detection zone located in a separate layer of the µPAD. The digital image of the complex is analyzed using ImageJ software. The method has a linear calibration range of 50–350 mg L−1 Hg with the detection limit of 20 mg L−1. The method was successfully applied to the determination of mercury in contaminated soil and water samples which the results agreed well with the ICP-MS method. Three soil samples were highly contaminated with mercury above the acceptable WHO limits (0.05 mg kg−1). To the best of our knowledge, this is the first colorimetric µPAD method that is applicable for soil samples including mercury contaminated soils from gold mining areas.

The program WinMLR has been developed to quantify sorbic and benzoic acids in soft drinks, fruit juices, and soy sauce by making a multilinear regression treatment of experimental data to a linear combination of standard signals. The spectra of sorbic and benzoic acid and samples were obtained from a conventional spectrophotometer, which has been saved in an ASCII file to be applied with the WinMLR program. Before to determine sorbic and benzoic acids in samples, the wavelength validation and calibration parameters were studied. Standard solutions of sorbic and benzoic acids were used for the calibration parameters to measure the individual analyte. If the sample has simultaneously both compounds, it is better to choose the synthetic mixture for the calibration parameters. This technique provides a good recovery in the range of 80.4–104.8% without a complicated and expensive instrument.

A new design of a membraneless vaporization (MBL-VP) unit coupled with a specific flow system is presented for the determination of arsenic at trace levels using a hydride generation process. The MBL-VP unit contains two concentric conical reservoirs, with the outer cone selected as the donor reservoir. The volume of the outer donor reservoir is thereby greater than the acceptor volume, necessary for holding sufficient sample and reagents for the generation of arsine gas by reaction between As(iii) and sodium borohydride under acidic conditions. The arsine gas diffuses into the narrow headspace and is absorbed by an aliquot of 150 μL of mercuric chloride acceptor solution. The resulting reaction produces hydronium ions which is monitored by the absorbance change at 530 nm of the methyl orange indicator added in the acceptor solution. To decrease the detection limit, the aspiration and removal of the donor plug, comprising the sample, borohydride and acid, into and out of the donor cone are repeated several times, while the acceptor solution is kept unchanged. As a result, analysis of arsenic was achieved in the range of 10 to 100 μg L-1 with a detection limit of 8 μg L-1. Application to surface water was investigated. Percent recoveries of spiked surface water samples were in the range of 94-110%. For comparison of total arsenic (As(iii) and As(v)), the results obtained from the developed method are not statistically different from the ICP-OES method.

A flow injection analysis system (FIA) for the simultaneous determination of salinity, carbonate and ammoniacal nitrogen has been developed and reported in this paper. FIA incorporating membrane units was used, not only for the separation of the gaseous carbon dioxide and ammonia, but also for on-line dilution in the salinity measurement. The sample was injected via a 10-port valve with two sample loops. One loop was used for salinity and carbonate measurements and the second loop for ammoniacal nitrogen determination. A dual-channel capacitively coupled contactless conductivity detector was assembled in a single shielding box. Input voltage from the same AC power supply was fed to the input electrodes of both C4D cells. One channel of the C4D was used to monitor the change in conductivity of an acceptor stream that carried a zone of the water sample that has passed through the on-line dilution unit. Conductivity of this zone relates directly to the salinity of the sample. The same sample zone was next acidified to generate carbon dioxide gas that diffused through a hydrophobic membrane of the first gas diffusion (GD) unit. The zone of dissolved carbon dioxide in acceptor stream of water flowed into the same C4D cell as for the salinity measurement, but arriving at a later time. Concurrently, the second channel of the C4D monitored the change in conductivity of the acceptor stream in the second GD unit due to the diffusion of ammonia gas generated by the reaction of base with the sample injected from the second sample loop. The change in conductivity at this second C4D cell correlates with the concentration of ammoniacal nitrogen present in the sample. The proposed method is low cost, simple, rapid and sensitive. The limit of quantitation for salinity, carbonate and ammoniacal nitrogen are 0.31mmolL−1, 1.85 µmol L−1, respectively. Throughput of 20 samples h−1 for simultaneous analysis can be achieved with RSD of less than 3.8%. The system had been applied to the determination of salinity, carbonate and ammoniacal nitrogen in 15 water samples, with results in agreement with those obtained using comparison methods.

This study presents a simple flow-based system for the determination of the preservative agent sulfite in food and beverages. The standard method of conversion of sulfite ions into SO2 gas by acidification is employed to separate the sulfite from sample matrices. The sample is aspirated into a donor stream of sulfuric acid. A membrane gas&ndash, liquid separation unit, also called a &lsquo, gas-diffusion (GD)&rsquo, unit, incorporating a polytetrafluoroethylene (PTFE) hydrophobic membrane allows the generated gas to diffuse into a stream of deionized water in the acceptor line. The dissolution of the SO2 gas leads to a change in the conductivity of water which is monitored by an in-line capacitively coupled contactless conductivity detector (C4D). The conductivity change is proportional to the concentration of sulfite in the sample. In this work, both clear (wine) and turbid (fruit juice and extracts of dried fruit) were selected to demonstrate the versatility of the developed method. The method can tolerate turbidity up to 60 Nephelometric Turbidity Units (NTUs). The linear range is 5&ndash, 25 mg L&minus, 1 SO32&minus, with precision &lt, 2% RSD. The flow system employs a peristaltic pump for propelling all liquid lines. Quantitative results of sulfite were statistically comparable to those obtained from iodimetric titration for the wine samples.

This work presents a new dual-purpose detector for photometric and conductivity measurements in flow-based analysis. The photometric detector is a paired emitter&ndash, detector diode (PEDD) device, whilst the conductivity detection employs a capacitively coupled contactless conductivity detector (C4D). The flow-through detection cell is a rectangular acrylic block (ca. 2 &times, 2 &times, 1.5 cm) with cylindrical channels in Z-configuration. For the PEDD detector, the LED light source and detector are installed inside the acrylic block. The two electrodes of the C4D are silver conducting ink painted on the PEEK inlet and outlet tubing of the Z-flow cell. The dual-purpose detector is coupled with a sequential injection analysis (SIA) system for simultaneous detection of the absorbance of the orange dye and conductivity of the dissolved oral rehydration salt powder. The detector was also used for sequential measurements of creatinine and the conductivity of human urine samples. The creatinine analysis is based on colorimetric detection of the Jaff&eacute, reaction using the PEDD detector, and the conductivity of the urine, as measured by the C4D detector, is expressed in millisiemens (mS cm&minus, 1).

In this work, a new flow system was developed for investigating the efficiency of synthesized TiO2 photocatalysts for NO2 degradation. The system consists of two parts: the gas flow reactor and an on-line NO2 monitoring system. The latter is based on the conversion of NO2(g) to NO2−(aq) with subsequent spectrophotometric detection of the nitrite anion by the Griess-Saltzman reaction. Simplex optimization was employed to obtain the required sensitivity for the NO2 monitoring. The developed flow system was employed to measure the catalytic efficiency of photodegradation of NO2 by various types of TiO2-based synthesized photocatalysts and a commercial TiO2 photocatalyst, ‘P25’. The TiO2 photocatalysts were synthesized using titanium isopropoxide (TTIP), tetrabutyl orthotitanate (TBOT) and titanium oxysulfate (TiOSO4) as precursors. Glass beads, coated with the TiO2 photocatalyst, were packed in a quartz tube reactor. Standard NO2 gas mixture (50 ppmv) was continuously flowed through the reactor under UV radiation. Residual NO2 from the outlet of the reactor was measured using the on-line NO2 monitoring system which employs a gas diffusion unit and an acceptor stream of triethanolamine solution. The NO2(g) was converted into NO2−(aq) which was measured spectrophotometrically at 540 nm using the Griess-Saltzman reaction. The photocatalytic efficiency of the synthesized photocatalysts was compared. The effects of oxygen and humidity were also studied in order to investigate the mechanism of photodegradation of NO2by the TiO2 catalyst. We observed that at low humidity (12% RH), the OH• radical generated from moisture plays an important role for photooxidation process of NO2.

A green analytical flow method was developed for the determination of total sulfite in white wine. The method employs the membraneless vaporization (MBL-VP) technique for gas–sample separation allowing direct analysis of wine. Sulfite in an aliquot of sample was converted to SO2 gas via acidification. Dissolution of the gas into the water acceptor led to a change in the conductivity of the acceptor which was monitored using a ‘capacitively coupled contactless conductivity detector’ (C4D) flow cell. Only a minute amount of common acid (100 μL of 1.5 mol L−1 H2SO4) is used. The MBL-VP unit was incorporated into the flow system to separate the SO2 gas from the wine sample using the headspace above the donor and acceptor compartments as a virtual membrane. The method provides a linear working range (10–200 mg L−1 sulfite) which is suitable for most wines with calibration equation y = (0.056 ± 0.002)x + (1.10 ± 0.22) and r2 = 0.998. Sample throughput is 26 samples h−1. The lower limit of quantitation (LLOQ = 3SD of blank per slope) is 0.3 mg L−1 sulfite for 20 s diffusion time with good precision (%RSD = 0.8 for 100 mg L−1 sulfite, n = 10). We also present a simple modification of the MBL-VP unit by the addition of a third cone-shaped reservoir to provide two acceptor zones leading to improvement in sensitivity of more than three-fold without use of heating to enhance the rate of diffusion of SO2.

This work presents a novel method for simultaneous spectrophotometric determination of phosphate and silicate by using a cross injection analysis (CIA) coupled with the use of partial least squares (PLS) for data evaluation. The detection principle is based on the well-known ‘molybdenum blue’ method. The molybdate ions in the presence of stannous chloride in acidic medium give phosphomolybdenum blue and silicomolybdenum blue as products. In this work, all the liquids, including sample and reagents were simultaneously introduced into a CIA platform by using two peristaltic pumps for controlling the x-channel and y-channel flow which was automatically manipulated by using in-house control board. Crossflow provides sufficient mixing inside the platform prior detection of the absorption spectra of blue complexes in the wavelength of 400–900 nm. Since spectra of the blue colour product of phosphate and silicate are resemblant, these two analytes therefore reciprocally interfere with one another. This r...

This work reports the preparation and utility of cysteine-functionalized carbon-coated Fe3O4 materials (Cys-C@Fe3O4) as efficient sorbents for remediation of Hg(II)-contaminated water. Efficient removal (90%) of Hg(II) from 1000 ppb aqueous solutions is possible, at very low Cys-C@Fe3O4 sorbent loadings (0.01 g sorbent per liter of Hg(II) solution). At low metal concentrations (5&ndash, 100 ppb Hg(II)), where adsorption is typically slow, Hg(II) removal efficiencies of 94&ndash, 99.4% were achievable, resulting in final Hg(II) levels of &lt, 1.0 ppb. From adsorption isotherms, the Hg(II) adsorption capacity for Cys-C@Fe3O4 is 94.33 mg g&minus, 1, around three times that of carbon-coated Fe3O4 material. The highest partition coefficient (PC) of 2312.5 mgg&minus, 1&micro, M&minus, 1 was achieved at the initial Hg (II) concentration of 100 ppb, while significantly high PC values of 300 mgg&minus, 1 and above were also obtained in the ultralow concentration range (&le, 20 ppb). Cys-C@Fe3O4 exhibits excellent selectivity for Hg(II) when tested in the presence of Pb(II), Ni(II), and Cu(II) ions, is easily separable from aqueous media by application of an external magnet, and can be regenerated for three subsequent uses without compromising Hg(II) uptake. Derived from commercially available raw materials, it is highly possible to achieve large-scale production of the functional sorbent for practical applications.

This work highlights an application of Cu–Zn hydroxide nitrate (denoted as 6Cu–Zn) as a highly effective and reusable catalyst for catalytic wet peroxide oxidation of phenol under mild conditions (35 °C). PXRD and XANES experiments were carried out to confirm a single phase of copper hydroxide nitrate in the 6Cu–Zn sample. The catalytic activity of 6Cu–Zn for degrading phenol was reported in terms of the percent phenol conversion, and chemical oxygen demand (COD) removal efficiency. Treatment of 100, 200, and 500 ppm aqueous phenol solutions with H2O2/6Cu–Zn resulted in complete phenol degradation within 10 min. The 6Cu–Zn catalyst can be reused for up to five consecutive runs while maintaining complete phenol conversion and COD removal efficiency (greater than 90%) after water washing. This work introduces a simple, mild, energy efficient and effective pretreatment method for highly toxic wastewater which could be applied prior to feeding the pretreated wastewater to subsequent conventional treatment units.

A miniaturized detection system for chemiluminescence that is generated on a microfluidic paper-based analytical device (μPAD) was developed using optical fibers and was applied to the determination of Cr(III). The μPAD was fabricated by wax printing and consisted of 6 separate channels in a parallel alignment. Each channel was composed of an injection zone for a reagent solution, a reaction zone, and a waste zone. The μPAD was placed on a plastic holder equipped with 6 optical fibers to collect chemiluminescence (CL). The other ends of the optical fibers were bundled and introduced into a small photomultiplier tube module to obtain the CL signals. The CL reaction was based on luminol oxidation by hydrogen peroxide in the presence of Cr(III), which catalyzed the reaction in an alkaline medium. The reaction conditions, including the use of an enhancer and a masking agent, were optimized to obtain high sensitivity and selectivity. Under the optimal conditions, a linear range was obtained at 0.05 to 1.00 ppm with a detection limit of 0.02 ppm. The analysis time was less than 1 min per one μPAD in order to obtain 6 measurements of differing concentrations with a precision of

This work presents the use of a single membraneless vaporization unit (MBL-VP unit) in a flow system for the simultaneous determination of ethanol and total sulfite in white wine. The flow system comprises a MBL-VP unit with three cone-shaped reservoirs and two in-house detectors, a paired emitter-detector diodes (PEDD) and a capacitively coupled contactless conductivity detector (C4D). The sample of white wine is first acidified in the flow system. Then 200-μL of the acidified sample is delivered to the donor reservoir of the MBL-VP unit in which the two acceptor reservoirs contain 200-μL of the gas acceptor reagents, viz. acidic permanganate solution and deionized water. Vaporization of ethanol and SO2(g) (converted from sulfite) from the donor into the acceptor reservoirs is carried out for 15 s. The two acceptor solutions are then simultaneously transferred for separate detection at the PEDD and C4D detectors. Decolorization of the permanganate solution by the reduction reaction with absorbed ethanol gives an increase in the PEDD signal, whereas dissolution of the SO2(g) in the water acceptor leads to an increase in conductivity and detected by the C4D. Linear calibrations were obtained in the range of 5.0–15.0% (v/v) for ethanol (PEDD signal = ((4.0 ± 0.03) × 10−2) · (%(v/v) ethanol) – ((1.85 ± 0.35) × 10−2): r2 = 0.999) and 10–200 mg L−1 for sulfite (C4D signal = ((0.64 ± 0.015) × 10−2) · (mg L−1 sulfite) – ((3.25 ± 1.64) × 10−2): r2 = 0.999). The analysis is rapid with total analysis time of 2.5 min. Percentage of recoveries were 81–104% and 88–110% for ethanol and sulfite, respectively. The method was compared with gas chromatographic analysis and iodometric titration for ethanol and sulfite, respectively, with no statistically significant difference for the analysis of seven white wine samples.

A low-cost and user-friendly microfluidic paper-based analytical device (μPAD) was developed for identification of bullet hole from gunshot residue (GSR) on cotton fabric target. The device (25 × 82 mm) is made of filter paper with a printed pattern consisting of a circular sample loading reservoir (6 mm i.d.), a circular waste reservoir (4 mm i.d.) and a straight flow channel (3 mm wide and 60 mm long). A sticker with a ruler scale in millimeters was mounted alongside the channel. The straight channel is first impregnated with rhodizonate and dried at ambient temperature. Tartrate extract of the target fabric is loaded on the sample reservoir. If Pb(II) ions are present in the extract, pink streak of Pb(II)-rhodizonate precipitate is formed as the sample solution flows from the reservoir along the channel. The length of the pink strip is employed to estimate the firing distance.

A novel spectrophotometric method for the determination of bromide has been developed using the Multisyringe Flow Injection Analysis technique (MSFIA). This method is based on the decolorization of methylene blue by the bromine released from the oxidation of bromide by bromate under acidic conditions. By incorporating a gas-diffusion unit into the MSFIA system the transferred bromine reacts with methylene blue in the acceptor stream. The decrease of the methylene blue absorbance is monitored at 745 nm. The oxidation conditions are not strong enough to oxidize chloride to chlorine, which is a major component of both natural and seawater. The proposed method provides linearity for the determination of bromide over a range of 1 × 10−5 mol L−1 to 6 × 10−5 mol L−1 in 5 × 10−2 mol L−1 of chloride, with a correlation coefficient (r2) of 0.9939, and a precision of 3.1% (%RSD for 3 × 10−5 mol L−1 Br− in 5 × 10−2 mol L−1 Cl−, n = 10). The limit of detection (3σ) is 0.5 × 10−5 mol L−1. The proposed method has been applied to the determination of Br− in water samples, obtaining recoveries in the analysis of spiked tap, natural, and seawater samples in the range of 90–106%.

The evolution of an entirely green analytical system for industrial quality control of carbonated drinks is described. The developed flow system is capable of providing analytical data of the dissolved CO2, sucrose, and color of a sample consecutively in real-time. The system has been carefully designed on the basis of “reagent-free”, meaning that no added chemicals are required for the analysis. The system first vaporizes CO2 from the soft drink in a gas–liquid separation chamber, with a channel for a flow of pure water as the CO2 acceptor. The dissolved CO2 alters the conductivity of the water stream, which is directly related to the concentration of CO2 in the soft drink. The sucrose content is measured based on the “schlieren effect”, the sample plug flows out of the vaporization chamber into a colorimeter with a near-infrared/light-emitting diode (NIR/LED) as light source. The schlieren effect arises at the boundary of pure water and soft drink with refraction of light in proportion to the sugar concentration. The system also measures the absorbance of the sample using an RGB-LED. The related principles and preliminary experiments as proof of concept are described as well as the construction of the flow system for this completely reagent-free analyzer. A simple flow injection system using the schlieren effect was also developed for rapid quantitative analysis of sugar in noncarbonated soft drinks.

Cobalt has been reported for being abused as an illegal doping agent due to its ability as an erythropoiesis-stimulating agent for enhancing performance in racehorses. Since 2015, cobalt is listed as a prohibited substance by the International Federation of Horseracing Authorities (IFHA) with a urinary threshold of 0.1 μg cobalt per mL urine. To prevent the misuse of cobalt in racehorse, a simple method for detection of cobalt is desirable. In this work, the detection of cobalt is based on the spectrometric detection of the complex formation between cobalt(II) and 2-(5-bromo-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl)amino]aniline at pH 4. The absorbance of the complex is monitored at 602 nm. The metal:ligand ratio of the complex is 1:2. The calibration graph was linear in the range of 0 – 2.5 μM {Absorbance = (0.0825 ± 0.0013)[Co2+] + (0.0406 ± 0.0003), r2 = 0.999} and the detection limit (3 SD of intercept)/slope) was 0.044 μM. The proposed method has been successfully applied to horse urine samples with the recoveries in the range 91 – 98%.

A simple CE-C 4 D method has been developed for the determination of glucosamine by direct injection of human serum and pharmaceutical samples. Glucosamine was electrokinetically injected and analysed in its protonated form using 20 mM MES/His (pH 6) as background electrolyte in order to separate it from the matrix and to provide a better response to the C 4 D detector. Separation of glucosamine in human serum and pharmaceutical samples was performed in 3 min without the need for protein precipitation or matrix removal. Good precision in terms of %RSD for the migration time and peak area were less than 1.91% ( n = 10). The conductivity signal was linear with glucosamine concentration in the range 0.10–2.50 mg/mL, with a detection limit of 0.03 mg/mL. Recoveries of glucosamine in serum and pharmaceutical samples were 86.5–104.78%. The method was successfully applied for the determination of the glucosamine content in pharmaceutical formulations and validated with high performance liquid chromatography (HPLC). Good agreements were observed between the developed method, label values and the HPLC method. Glucosamine could be detected in spiked serum sample by direct injection. This was not possible by HPLC due to co-eluting interferences.

This work presents a flow analysis method for direct quantitation of calcium carbonate in cement without pretreatment of the sample. The method is based on online vaporization of CO 2 gas following acidification of the sample inside a small chamber that has a flow of acceptor solution passing around it. Solubilization of the CO 2 gas into the acceptor stream changes the conductivity of the acceptor solution causing an increase of signal at the capacitively coupled contactless conductivity detection (C 4 D) placed at the outlet of the vaporization chamber. This chamber is an adaption from previous work reported on ‘membraneless vaporization’ (MBL-VP). The method can be used in the quality control of production of mixed cement. These cement materials usually have calcium carbonate contents at high concentration range (e.g., 33–99% (w/w) CaCO 3 ). Analysis of samples by this method is direct and convenient as it requires no sample pretreatment. The method is low-cost with satisfactory accuracy and acceptable precision.

An in-house flow-injection capillary electrophoresis with capacitively coupled contactless conductivity detection method was developed for the direct measurement of colistin in pharmaceutical samples. The flow injection and capillary electrophoresis systems are connected by an acrylic interface. Capillary electrophoresis separation is achieved within 2 min using a background electrolyte solution of 5 mM 2-morpholinoethanesulfonic acid and 5 mM histidine (pH 6). The flow-injection section allows for convenient filling of the capillary and sample introduction without the use of a pressure/vacuum manifold. Capacitively coupled contactless conductivity detection is employed since colistin has no chromophore but is cationic at pH 6. Calibration curve is linear from 20 to 150 mg/L, with a correlation coefficient (r(2) ) of 0.997. The limit of quantitation is 20 mg/L. The developed method provides precision, simplicity, and short analysis time.

A simple and fast flow injection spectrophotometric method for the determination of bromate in water samples was developed. The detection system is based on the oxidation of prochlorperazine (PCP) with bromate in strongly acidic medium. Large amounts of chloride and bromide was found, for the first time, to act as an activator, and to enhance the sensitivity for bromate detection. The oxidation product of PCP gives pink color, which can be used to monitor the reaction spectrophotometrically at 525 nm. Under the optimal conditions, the method is selective; only nitrite, chlorite and hypochlorite can interfere with the determination of bromate. The elimination of these three ions is discussed. The calibration graph for bromate determination was linear in the range of 10-130 microg L(-1) with a detection limit of 2.3 microg L(-1). The repeatability was satisfactory, with the relative standard deviation of 1.1% (25 microg L(-1), n=10). The sample throughput was 44 h(-1). The proposed method was found to be highly reliable for screening drinking waters containing bromate, which is above or below legislation limit of 10 microg L(-1).

A simple, sensitive and selective method for the determination of bromide in seawater by using a flow injection/stopped-flow detection technique was examined. The detection system was developed for a new kinetic-spectrophotometric determination of bromide in the presence of chloride matrix without any extraction and/or separation. The detection was based on the kinetic effect of bromide on the oxidation of methylene blue (MB) with hydrogen peroxide in a strongly acidic solution. Large amounts of chloride could enhance the sensitivity of the method as an activator. The decolorisation of the blue color of MB was used for the spectrophotometric determination of bromide at 746 nm. A stopped-flow approach was used to improve the sensitivity of the measurement and provide good linearity of the calibration over the range of 0-3.2 p,g ml(-1) of bromide. The relative standard deviation was 0.74% for the determination of 2.4 jig ml(-1) bromide (n=5). The detection limit (3 sigma) was 0.1 mu g ml(-1) with a sampling frequency of 12 h(-1). The influence of potential interfering ions was studied. The proposed method was applied to the determination of bromide in seawater samples and provided satisfactory results.

This work presents a new flow injection strategy, called ‘cross injection analysis’ or CIA, an alternative cost-effective approach in flow analysis. The flow platform is made from a rectangular acrylic block, approximately 5×3×1.5 cm ( x × y × z ), with crossing cylindrical channels drilled out along the x - and y -axis of the block. The outlet from the single x -axis channel is connected to a detector flow cell. This channel is filled with the carrier solution. The flow in the x -axis channel is driven by a computer controlled single-channel peristaltic pump. The multiple y -axis channels, running perpendicular to the x -channel, are connected to a multi-channel peristaltic pump. These channels contain the sample and reagent solutions that flow across the intersection zones of the channels. To mix the sample and reagent with subsequent detection of the reaction zone, flow is applied along the x -axis channel, while flow in the y -axis channels is stopped. We successfully demonstrated the validity of the CIA technique by the spectrometric determination of Fe(II) using 1,10-phenanthroline and the speciation of Fe(II) and Fe(III). To place the CIA technique within the context of flow analysis, a brief overview of the evolution of flow injection analysis and its later innovative development is included.

A new apparatus, called 'membraneless vaporization' (MBL-VP) unit was designed and developed for direct analysis of solid samples. Solid analyte was converted into a gaseous form which then reacts with an indicator reagent. Change in absorbance was used to quantitate the analyte. Stirring with a magnetic bar was employed to facilitate the evaporation of the gas. Unlike the pervaporation technique, hydrophobic membrane was not required for this MBL-VP technique. Application of the membraneless technique for direct determination of calcium carbonate in calcium supplements, has shown to be very precise (R.S.D.=2.5% for 0.16 mmol CO3(2-)), with detection limit of 0.5 mg CaCO3. Results by this method agreed well with flame atomic absorption spectrometric method. Sample throughput was 20 samples h(-1).

A novel simple, sensitive and rapid kinetic-spectrophotornetric method is proposed for the determination of trace amounts of bromide. The method is based on its catalytic effect on the oxidation of methylene blue (MB) by hydrogen peroxide in strongly acidic solution. The oxidation reaction is activated by large amounts of chloride and can be monitored spectrophotometrically by measuring the decrease in the absorbance of MB at 746 run. The determination of bromide is performed by a fixed-time method at the first 100 s from the initiation of the reaction. Unlike other kinetic-spectrophotornetric methods for the determination of bromide, the proposed method does not require heating the solution. Bromide can be determined in the range from 80 to 960 mu g l(-1) with the detection limit of 35 mu g l(-1). The relative standard deviation of ten replicate determination of 480 mu g l(-1) bromide was 1.4%. The influence of potential interfering ions was studied. The proposed method was satisfactorily applied to the determination of bromide in seawater without interfering effect from chloride ion.

This work presents a flow injection (FI) system that was developed for determination of iodate. The system utilizes the oxidation of iodide by the analyte to iodine, which subsequently forms tri-iodide. In the presence of starch, the blue I3−–starch complex is developed within the sample zone and can be colorimetrically detected at 590 nm. Optimization was carried out to make the system suitable for quantitating iodate added to table salts. To prevent accumulation of the blue complex residue on walls of tubing and the flow cell, a port was placed in the system for injection of 10−3 M thiosulfate plug (100 μl). An injection of this cleaning solution after each sample injection is recommended to avoid positive baseline shift. By means of the paired t-test, the amounts of iodine (mg I kg−1) were statistically compared with the results determined by titration and by iodide ion selective electrode. No significant disagreement at 95% confidence was observed. The proposed system is very simple, uses common chemicals and provides rapid analysis (65 injections per h) with high precision (R.S.D.=0.66%, n=10). A detection limit of 2 mg I kg−1 salt can be achieved.