Mixing Coil Research Articles

Upgrading API and Specific Gravity Specifications of Iraqi Crude Oil Using a Laboratory-Built Multipumping Fuel Analysis (MPFA) System

Iraqi heavy crude oil (26.85 API) is processed by a laboratory-made fuel injection system and through the deasphalting oil (DAO) extraction process by different solvents and the application of different variables. The system was built with low-cost parts found in local markets. The purpose of a manufactured fuel system is to enhance the API and specific gravity (Sp.gr.) specifications of the collected samples and obtain the reduced crude oil through the DAO process. The extraction was carried out with a temperature range, a solvent flow rate, a mixing coil length, a solvent entry time, and different types of solvents. In general, results show that the API and Sp.gr of DAO increased from 26.85 and 0.8936 to 39.28 and 0.8132, respectively. Also, sulfur content decreased from 4.1967 wt.% to 2.201 wt.% at optimum conditions. The semi-automated MPFA system was successfully used to enhance crude oil specifications sensitive and accurate manner.

Determination of Total Ammonia Nitrogen by Gas-Diffusion Flow Injection Analysis (GD-FIA)-Spectrophotometry using Minnieroot Flower (Ruellia tuberosa) as Natural Reagent

Total ammonia nitrogen (TAN) is a pollutant agent found in water and generated from the metabolisms of living organisms and the decomposition of organic matter. This research aims to develop an efficient, low-cost, and environmentally friendly TAN analysis method. The principle of this method is based on the reaction of TAN injected in the donor stream with NaOH to form alkaline gaseous ammonia. The gaseous ammonia diffuses through a hydrophobic membrane into an acceptor stream containing Ruellia tuberosa extract. The presence of NH3 gas in the acceptor stream changes the extract color from pinkish to green, which is monitored by spectrophotometer at 620 nm. This method was also validated based on linearity, selectivity, and accuracy. Under the obtained optimum conditions of 1 M NaOH, 5% extract, a 120 cm mixing coil, and a 200 µL sample volume, the proposed method showed excellent linearity at 10–1000 ppm (R2 = 0.993). The selectivity test result shows that this method was selective against sulfite and nitrite compounds up to 600 ppm with a % error value <10%. This method was applied to measure the total ammonia concentration in agricultural water, and satisfying results were shown by high recoveries of 95.03%–98.84%.

A Continuous Flow Injection/Indirect Photometric Method for the Detection of Fosetyl Aluminum in Commercial Pesticide Formulations

AbstractBecause of their Physico‐chemical characteristics and its composition, the development of new specific analytical methodologies to determine some highly polar pesticides are required. The reported methods demand long analysis time, expensive instruments and prior extraction of pesticide for detection. The current work presents a new flow injection analysis method combined with indirect photometric detection for the determination of Fosetyl‐Aluminum (Fosetyl‐Al) in commercial formulations, with rapid and highly accurate determination involving only construction of manifold system combined with photometric detector without need some of the pre‐treatments to the sample before the analysis such as extraction or separation. The proposed method is based on the reaction between the Fosetyl‐Al with the colorimetric reagent (Aluminon dye) in an aqueous medium of sodium nitrite resulting in the formation of a red complex and its absorbance is measured using the photometric detector. The proposed method included optimization of several parameters such as sodium nitrite concentration, flow rate, sample volume, Aluminon dye concentration, mixing coil and light intensity. The linear range of the detector response was in the range of 0.005–1.8 mmol/L for the sample with r (coefficient of determination) 0.9909, R2 (correlation coefficient) 0.9954 at 95 % and 0.0041 mmol/L as a limit of detection. The relative standard deviation was less than 1.5 % for 0.005 mmol/L of the analyte (n=11). The proposed method was validated and applied successfully for the determination of Fosetyl‐Al in commercial formulations and can be used as an alternative method for quality control assessment.

Flow Injection Analysis with Turbidity Detection for the Quantitative Determination of Mebeverine Hydrochloride in Pharmaceutical Formulations

The main objective of this paper is to develop and validate flow injection method, a precise, accurate, simple, economic, low cost and specific turbidimetric method for the quantitative determination of mebeverine hydrochloride (MbH) in pharmaceutical preparations. A homemade NAG Dual &amp; Solo (0-180º) analyser which contains two identical detections units (cell 1 and 2) was applied for turbidity measurements. The developed method was optimized for different chemical and physical parameters such as perception reagent concentrations, aqueous salts solutions, flow rate, the intensity of the sources light, sample volume, mixing coil and purge time. The correlation coefficients (r) of the developed method were 0.9980 and 0.9986 for cell 1 and 2 respectively and showed the linearity of response against concentration over the range of 1.0 to 6.5 and 0.7-6.5mmol/L for cell 1 &amp; 2 respectively. The limit of detections (LOD) for cell 1 and cell 2 were 0.28 and 0.21 mmol/L respectively. The intra-day and inter-day precision for two serial estimations of 3.5 and 5.5 mmol/L of MBH exhibited a relative standard deviation of 0.46%, 0.28%, 0.23%, 0.26% and 0.39%, 0.79%, 0.14%, 0.05% for cell 1 &amp; 2 respectively. The accuracy of the developed method has expressed a recovery percentage (Rec %) and error % which was between 99.22 to 101.13 and 99.39 to 101.17 for cell 1 and cell 2 respectively. The ICH guidelines were followed for method validation. The developed method was successfully applied for the determination of MbH in pure and pharmaceutical preparations and the method can be conveniently used for routine analysis in laboratory as a quality control method since the method permits quantitively determination of 60 samples/h.

Voltammetric Determination of Trace Heavy Metals by Sequential‐injection Analysis at Plastic Fluidic Chips with Integrated Carbon Fiber‐based Electrodes

AbstractThis work describes a sequential injection analysis (SIA) method for on‐line strippping voltammetric determination of Pb(II), Cd(II) and Zn(II) using an injection‐moulded electrochemical fluidic chip consisting of 3 conductive carbon fiber‐loaded polymer electrodes embedded in a plastic fluidic holder. The sample containing the target metals and a solution containing Bi(III) were aspirated in the holding coil of the SIA manifold. Then, the flow was reversed and the two solutions were directed to the fluidic cell through a mixing coil which induced mixing of the two zones. Upon reaching the cell, simultaneous reduction of the target metals and Bi(III) occurred resulting in the formation of a metal‐Bi alloy on the working electrode. Finally, the accumulated metals were stripped off the bismuth‐film electrode via a positive potential scan and the oxidation current was recorded. The experimental variables (concentration of the bismuth plating solution, deposition potential, sample volume, stripping mode) were investigated and the potential interferences were assessed. The limits of quantification were 2.8 μg L−1 for Pb(II), 3.6 μg L−1 for Cd(II) and 4.2 μg L−1 for Zn(II) and the the within‐chip and between‐chip % relative standard deviations were ≤6.3 % and ≤14 %, respectively. Finally, the sensor was applied to the determination of trace metals in a fish food sample.

Automated Spectrophotometric Multi-Pumping Flow System for the Determination of Total Iron in Wine

A new automated system based on a multi-pumping flow system (MPFS) for the spectrophotometric determination of total iron in various wine samples is presented. This analytical protocol is based on the complex formation between Fe (II) and 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (Br-PADAP). The addition of ascorbic acid allows the determination of total iron by reducing the Fe (III) present in the samples to Fe (II). Several physical and chemical parameters, including the mixing coil length, the sample volume, the chromogenic reagent concentration, the pH, and the ascorbic acid concentration have been characterized in order to optimize the analytical conditions. The limits of detection and quantification were 34 µg L−1 and 114 µg L−1 respectively. The developed procedure requires minimal sample preparation.

A comparison of the performance of the cupric reducing antioxidant potential assay and the ferric reducing antioxidant power assay for the analysis of antioxidants using reaction flow chromatography

The cupric reducing antioxidant capacity (CUPRAC) assay is an established procedure used to measure antioxidant content. Recently, the CUPRAC assay was adapted for use in post column derivatisation coupled with high performance liquid chromatography (HPLC-PCD). In prior works reported in the literature, CUPRAC HPLC-PCD assays used large post column mixing coils leading to a deterioration in the observed separation efficiency. In this work we used the CUPRAC PCD assay with reaction flow (RF) chromatography. No reaction loop was required, thus preserving the efficiency of the separation. We subsequently compared the performance of the CUPRAC assay to that of an antioxidant assay that we have previously converted to RF chromatography, namely the ferric reducing antioxidant potential (FRAP) assay, both in RF mode. The relative response factor with respect to trolox was measured for both RF assays via the separation of a standard mixture of 16 compounds. Sample analysis of coffee and green tea via both RF assays was used to compare their ability to screen for bioactive candidates in complex natural products. In general, the CUPRAC assay is recommended as the RF PCD methodology of choice as it provided a higher level of performance compared to the FRAP assay, demonstrating less baseline noise interference, greater sensitivity, wider linear dynamic range and better assay precision.

Thiocyanate Determination using Technique of Flow Injection-Gas Diffusion Spectrophotometry with Cerium (IV)-Ninhydrin Reagent.

Numerous food plants contain thiocyanate, which can inhibit iodine uptake of thyroid gland and induce to the risk of iodine deficiency disorders (IDD). This research is focused on the development of new method for thiocyanate determination based on the formation of red hydrindantin using spectrophotometric flow injection (FI)–gas diffusion technique. In this technique, thiocyanate is oxidized by cerium (IV) in the acid donor stream to form hydrogen cyanide which diffuses through the membrane in the gas diffusion cell and reacts selectively with alkaline ninhydrin in the acceptor stream to form a red hydrindantin detected by spectrophotometer at 485 nm. The common operational conditions including sample volume, the length of mixing coil, and the flow rate as well as chemical parameters (concentration of cerium (IV) and ninhydrin, and pH reaction) were optimized with respect to sensitivity, analysis time, and linearity. The optimum condition notified by highest absorbance with sharp single peak and fast analysis was obtained under flow rate of 2 mL min−1, 300 µL sample volume, 75 cm mixing coil, 0.01 M cerium (IV), 1 % ninhydrin, and pH of 11. The interfering ions frequently exist with thiocyanate were also studied. Under the optimized conditions, the method showed linear for thiocyanate concentration from 5-30 mgL−1 and sampling rate of 120 s/h with a satisfactory reproducibility (RSD < 2% at n=3). This method has been successfully applied to determine thiocyanate in saliva from smoker and non-smoker and the results showed good agreement with those obtained from standard spectrophotometry method.

Development of Flow Injection-Spectrophotometry Method for Hydroquinone Determination Based on The Formation of Blue Starch-Iodine Complex

Hydroquinone (1,4-dihydroxybenzene) is an aromatic organic phenolic compound used in drug and should not be used as cosmetic products. Although the use of hydroquinone has been banned in cosmetics, it is still found at low concentration for skin whitening. The effect for excess use of hydroquinone can cause irritation and changes in skin color become blackish permanently. The determination of hydroquinone can be performed by a flow injection system with spectrophotometric detection based on the redox reaction between hydroquinone and iodine. Under this method, hydroquinone can be determined based on the decreasing intensity of the blue color of the starch-iodine complex when hydroquinone was added to the solution. Hydroquinone will react with the excess iodine, thus iodine is reduced to iodide. The rest of iodine which does not react with hydroquinone, will form a blue complex with starch in an acidic condition (pH = 1). The blue color of the starch-iodine complex was analyzed by visible spectrophotometry at a wavelength of 628 nm. The optimum conditions for determination of hydroquinone using the flow injection system provide at 0.05 % starch and 40 mg/L iodine by the length of mixing coil of 50 cm on the flow rate of 5.8 mL/min, and a sample volume of 100 µL. Under these optimum conditions, the flow injection method showed the linearity from 0 to 15 mg/L with a correlation (R2) of 0.9941.

Optimization of Flow Injection (FI) – Spectrophotometry for Hydroquinone Analysis

Hydroquinone is one of the phenolic compounds used in various cosmetic products for skin lightening as it can inhibit tyrosinase enzyme in producing melanin. However, hydroquinone is classified as a toxic compound, therefore, several countries such as Africa, Canada, and Indonesia prohibits hydroquinone usage in cosmetics. This research was focused on the development of a method for hydroquinone analysis using flow injection (FI) combined with spectrophotometry based on the reaction of hydroquinone with phloroglucinol in alkaline condition producing orange complex detected at 493 nm. The FI method was optimized based on operational factors and chemical factors in order to achieve sensitivity. The maximum sensitivity of FI method was achieved under operational condition of 100 μL sample volume, 100 cm mixing coil 1, 50 cm mixing coil 2 and 2.8 mL/min with the chemical condition of 0.005 mol/L NaOH and 0.001 mol/L phloroglucinol. Under these optimum conditions, the proposed method showed linearity in the range concentration of 2 – 80 mg/L and the method was applied to cosmetic sample with acceptable recovery

All-in-One Flow Injection Spectrophotometric System for Field Testing

To date one of the most significant innovative trends in chemical analysis is to develop analytical instruments that have processed to analyze on-site. Such an apparatus should minimize problems related to sample transports, sample handlings and sample storages. Currently, a traditional wet analysis in laboratories has been replaced with a portable device designed to minimize problems from sending samples to the lab. One of the practical chemical methods which can be developed as the mobile device is flow injection analysis (FIA) because the scaled-down FIA manifolds have been already presented. Regarding the detection, the rapid progress in material science and electronic technology consents the construction of portable detection devices, particularly light-emitting-diodes (LEDs) based-spectrometers. In this work, the FIA analyzer integrated with a built-in detector was designed for on-site chemical testing. A double syringes pump was assembled for transporting of the reagent carrier which were merged at the first mixing coil. A plug of a sample solution was inserted automatically by using a six-port-valve and was mixed with the carrier stream at the second mixing coil before directed to the detector. The heart of the developed analyzer is the built-in spectrophotometric sensor, made of the LEDs as a light source and a photodiode as a detector. The continuous stream of the final product was pushed into a quartz flow-through cuvette and then was exposed to the LED light. Finally, the absorbance of the product solution was calculated according to the Beer-Lambert law.

Entropy Generation Analysis through Helical Coil Heat Exchanger in an Agitated Vessel

Entropy Generation have been obtained while conducting the experiments for different sodium carboxymethyl cellulose concentrations 0.05%,0.1%,0.15% and 0.2% of Newtonian and non Newtonian fluids and the data made available by passing the test fluid at different flow rates through a helical coil in a mixing coil using paddle impeller. Heating of fluids depend on operational parameters, geometry of the mixing vessel and the type of impeller used. A new design of heating element was design and fabricated by providing kanthal wire inserted into a glove knitted with fiber glass yarn as glass fabric is flexible, heat resistant and can accommodate to adopt small difference in size of the vessel, perfectly. The knitted fabric is made to the shape of vessel used in the experiment and the heating elements are inserted so that it gets embedded and forms part of the glove knitted with yarn of fiber glass.

A green analytical method for benzoyl peroxide determination by a sequential injection spectrophotometry using natural reagent extracts from pumpkin

A green and environmental friendly method with simple sequential injection spectrophotometry using natural reagent extract from pumpkin (Cucurbita moschata Decne) for determination of benzoyl peroxide (BPO) was developed. The maximum absorption of the yellow crude extract containing the β-carotene compound occurred at a wavelength of 450nm. The yellow extract solution was bleached by BPO to change the color to a colorless solution. The optimum conditions of the proposed method, such as extraction solvent influence of pH, dilution of pumpkin extracts solution, aspiration volume of reagent and sample, flow reversal, incubation time, mixing coil length, and dispensing flow rate were studied and optimized. The linear calibration graph under the optimum conditions in the range of 9.4−100mgL−1 BPO was obtained with good linearity (r2=9985). The limit of detection (LOD) and the limit of quantification (LOQ) were 3.9 and 9.4mgL−1, respectively. Relative standard deviation was achieved at less than 4% (n=7). This system provided sample throughput of 9h−1. Good recoveries were found between 83.42±3.34–112.29±3.49%. The system was successfully employed as a natural reagent extract from pumpkin for determination of BPO in acne treatment samples. Also, the results agreed well with those obtained from the HPLC-UV method.

3D-printed flow system for determination of lead in natural waters

The development of 3D printing in recent years opens up a vast array of possibilities in the field of flow analysis. In the present study, a new 3D-printed flow system has been developed for the selective spectrophotometric determination of lead in natural waters. This system was composed of three 3D-printed units (sample treatment, mixing coil and detection) that might have been assembled without any tubing to form a complete flow system. Lead was determined in a two-step procedure. A preconcentration of lead was first carried out on TrisKem Pb Resin located in a 3D-printed column reservoir closed by a tapped screw. This resin showed a high extraction selectivity for lead over many tested potential interfering metals. In a second step, lead was eluted by ammonium oxalate in presence of 4-(2-pyridylazo)-resorcinol (PAR), and spectrophotometrically detected at 520nm. The optimized flow system has exhibited a linear response from 3 to 120µgL−1. Detection limit, coefficient of variation and sampling rate were evaluated at 2.7µgL−1, 5.4% (n=6) and 4 sampleh−1, respectively. This flow system stands out by its fully 3D design, portability and simplicity for low cost analysis of lead in natural waters.

Multi-reverse flow injection analysis integrated with multi-optical sensor for simultaneous determination of Mn(II), Fe(II), Cu(II) and Fe(III) in natural waters

Multi-reverse flow injection analysis (Mr-FIA) integrated with multi-optical sensor was developed and optimized for the simultaneous determination of multi ions; Mn(II), Fe(II), Cu(II) and Fe(III) in water samples. The sample/standard solutions were propelled making use of a four channels peristaltic pump whereas 4 colorimetric reagents specific for the metal ions were separately injected in sample streams using multi-syringe pump. The color zones that formed in the individual mixing coils were then streamed into multi-channels spectrometer, which comprised of four flows through cell and four pairs of light emitting diode and photodiode, whereby signals were measured concurrently. The linearity range (along with detection limit, µgL−1) was 0.050–3.0(16), 0.30–2.0 (11), 0.050–1.0(12) and 0.10–1.0(50)mgL−1, for Mn(II), Fe(II), Cu(II) and Fe(III), respectively. In the interim, the correlation coefficients were 0.9924–0.9942. The percentages relative standard deviation was less than 3. The proposed system was applied successfully to determine targeted metal ions simultaneously in natural water with high sample throughput and low reagent consumption, thus it satisfies the criteria of Green Analytical Chemistry (GAC) and its goals.

Simple flow injection colorimetric system for determination of paraquat in natural water

A simple and low cost flow injection colorimetric system has been developed for determination of paraquat in natural water. The developed method is based on the reduction of paraquat by using sodium dithionite as a reducing agent in an alkaline medium to produce a blue free radical ion that can be detected by a simple light emitting diode-light dependent resistor (LED-LDR) colorimeter. The standard or sample solution was injected via a set of 3-way solenoid valves into a water carrier stream and flowed to merge with reagent to generate a colored product which is proportional to the concentration of paraquat ion in the solution. Under the optimum condition of the system, i.e., mixing coil length 30cm, flow rate 2.0mLmin−1, sample volume 100μL, concentrations of dithionite 0.1% (w/v) and sodium hydroxide 0.06molL−1, a linear calibration graph in the range of 0.2–10.0mgL−1 with a correlation coefficient of 0.9996, and a limit of detection of 0.15mgL−1 were achieved. Relative standard deviation for 9 replicate injections of 1mgL−1 paraquat is 3.7%. A sample throughput of 40 injectionsh−1 was achieved. The limit of detection can be improved by off-line preconcentration of paraquat employing a column packed with Dowex 50WX8-100 (H) cation exchange resin and eluted with 10% (w/v) ammonium chloride in ammonium buffer solution pH 10. The eluting solution was then injected into the FI system for paraquat determination. The proposed system did not suffer from interferences of some possible ions in natural water and other herbicides. Recoveries obtained by spiking 0.5 and 5.0mgL−1 paraquat standard into water samples were in the range of 104–110% and 101–105%, respectively. The developed system can be conveniently applied for screening of paraquat contaminated in natural water.

Simultaneous Injection Effective Mixing Flow Analysis (SIEMA): Its Development and Application

The development and application of a new simultaneous injection- effective mixing flow analysis (SIEMA) is described. The manifold is based on one syringe pump with a two-way solenoid valve, a set of holding coils and three-way solenoid valves, two multiport connectors, a mixing coil and a detector. The system is compact and is controlled by a laptop computer. Some analytical features of SIEMA are compared with other flow-based systems in terms of mixing efficiency, reagent consumption and sample throughput. Applications of the SIEMA system are demonstrated for environmental and clinical analysis.

Flow injection analysis of trace chromium (VI) in drinking water with a liquid waveguide capillary cell and spectrophotometric detection

Hexavalent chromium (Cr(VI)) is an acknowledged hazardous material in drinking waters. As such, effective monitoring and assessment of the risks posed by Cr(VI) are important analytical objectives for both human health and environmental science. However, because of the lack of highly sensitive, rapid, and simple procedures, a relatively limited number of studies have been carried out in this field. Here we report a simple and sensitive analytical procedure of flow injection analysis (FIA) for sub-nanomolar Cr(VI) in drinking water samples with a liquid core waveguide capillary cell (LWCC). The procedure is based on a highly selective reaction between 1, 5-diphenylcarbazide and Cr(VI) under acidic conditions. The optimized experimental parameters included reagent concentrations, injection volume, length of mixing coil, and flow rate. Measurements at 540nm, and a 650-nm reference wavelength, produced a 0.12-nM detection limit. Relative standard deviations for 1, 2, and 10nM samples were 5.6, 3.6, and 0.72% (n = 9), and the analysis time was <2min sample(-1). The effects of salinity and interfering ions, especially Fe(III), were evaluated. Using the FIA-LWCC method, different sources of bottled waters and tap waters were examined. The Cr(VI) concentrations of the bottled waters ranged from the detection limit to ∼20nM, and tap waters collected from the same community supply had Cr(VI) concentration around 14nM.

Rapid Enzymatic Method for Pectin Methyl Esters Determination

Pectin is a natural polysaccharide used in food and pharma industries. Pectin degree of methylation is an important parameter having significant influence on pectin applications. A rapid, fully automated, kinetic flow method for determination of pectin methyl esters has been developed. The method is based on a lab-made analyzer using the reverse flow-injection/stopped flow principle. Methanol is released from pectin by pectin methylesterase in the first mixing coil. Enzyme working solution is injected further downstream and it is mixed with pectin/pectin methylesterase stream in the second mixing coil. Methanol is oxidized by alcohol oxidase releasing formaldehyde and hydrogen peroxide. This reaction is coupled to horse radish peroxidase catalyzed reaction, which gives the colored product 4-N-(p-benzoquinoneimine)-antipyrine. Reaction rate is proportional to methanol concentration and it is followed using Ocean Optics USB 2000+ spectrophotometer. The analyzer is fully regulated by a lab written LabVIEW program. The detection limit was 1.47 mM with an analysis rate of 7 samples h−1. A paired t-test with results from manual method showed that the automated method results are equivalent to the manual method at the 95% confidence interval. The developed method is rapid and sustainable and it is the first application of flow analysis in pectin analysis.

Alternative spectrophotometric method for determination of bilirubin and urobilinogen in urine samples using simultaneous injection effective mixing flow analysis

A new approach based on simultaneous injection effective mixing flow analysis (SIEMA) system was developed for the successive spectrophotometric determination of urobilinogen and bilirubin in urinary samples. A 4-channel SIEMA system consisted of a syringe pump, two 5-cross connectors, four holding coils (two of four were used for urobilinogen determination, and other two of four were used for bilirubin determination), five solenoid valves, a mixing coil and a spectrophotometer. For urobilinogen assay, the color development was based on the reaction with p-diethylaminobenzaldehyde (p-DEABA) in the presence of strong hydrochloric acid. On the other hand, bilirubin was measured by the reaction with diazotized sulfanilic acid in the presence of n-octyl-β-D-thioglucoside (OTG) which served as a solubilizing agent to form OTG–azobilirubin. Firstly for bilirubin determination, aliquots of sample and reagent solutions were aspirated into two individual holding coils by a syringe pump, and then the aspirated zones were simultaneously dispensed in the reverse direction to the detector flow cell. Secondary for urobilinogen determination, aliquots of sample and reagent for urobilinogen were aspirated into other two holding coils, followed by the similar spectrophotometric detection. Under optimal conditions, the automated method provided linearity up to 100.0 mg L−1 for urobilinogen and 5.0 mg L−1 for bilirubin. The 3σ limit of detections (LODs) for urobilinogen and bilirubin were 1.0 mg L−1 and 0.003 mg L−1, respectively. The relative standard deviations (RSDs, n = 11) of 30 mg L−1 urobilinogen and 1.0 mg L−1 for bilirubin were 1.5% and 1.0%, respectively. Sample throughput of the whole assay of both urobilinogen and bilirubin was 30 h−1. The proposed method can be applied to trace urobilinogen and bilirubin in urine samples and the results are useful for screening diabetic diagnostic.