Determination of promethazine in forensic samples using multi-walled carbon nanotube-gold nanoparticle electrochemical sensor.

An electrochemical sensor was developed based on a glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWCNTs) and gold nanoparticles (AuNPs) for the determination of promethazine (PMZ) in 'purple drank', pharmaceutical formulations, and synthetic saliva. The oxidation of PMZ at the modified electrode occurred at a higher cathodic potential and produced a higher sensitivity compared to the unmodified GCE. The morphology of the modified electrode was characterized using field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM). The presence of MWCNTs and AuNPs was confirmed. The optimized parameters included the concentration and pH of the supporting electrolyte, amount of modifiers used to fabricate the electrode, deposition potential, and time. Using these optimized conditions, the method has a linear range from 0.5 to 100 µmol L-1, with a R2 value of 0.9991. The limit of detection (3SDblank/slope) was 0.13 µmol L-1. The proposed electrochemical sensor was successfully applied for the determination of PMZ in 'purple drank', pharmaceutical formulations, and spiked synthetic saliva samples. The results obtained from this sensor were in statistical agreement with the values obtained using the reference gas chromatography-flame ionization method.

Data independent acquisition for gas chromatographic MS/MS analysis of volatile compounds.

This study presents a novel tandem mass spectrometry (MS/MS) approach utilizing a data independent acquisition (DIA) concept specifically designed with gas chromatography-electron ionization-triple quadrupole mass spectrometry (GC-EI-QqQMS). This allows compound identification based on comparison between all the experimental MS/MS product ion spectra and the simulated library data of >1,000 MS/MS transitions of 71 compounds. The simulation data were generated by using the Competitive Fragmentation Modeling (CFM-ID) 3.0 program. The approach for calculation of the DIA MS/MS library match scores was then established and applied for identification of a range of terpenoids and oxygenated compounds in perfume. The identity of each peak was confirmed using 4-241 MS/MS transitions. The established data collection and analysis methods are expected to be useful for increased confidence in volatile compound analysis.

Measurement of sucrose concentration using Imbibition length on paper: A device for equipment-free and environmentally-friendly detection.

The Lucas-Washburn equation is commonly used to predict the distance (L) that a liquid travels through paper. This equation establishes that L2 is linear with time and inversely proportional to the viscosity of the liquid. However, there is currently no theoretical equation connecting the viscosity of a solution to its concentration. In this study, the imbibition flow of a sucrose solution was measured along the length of a horizontal strip of filter paper, featuring a printed, thermometer-shaped hydrophobic boundary. A sample (38 µL) was dispensed onto the bulb area, and the solution's flow was visually tracked using a red dye added to the sample. The imbibition length (L) was measured by a vernier caliper at 10.0 min after the sample addition. An empirical equation, based on literature values of the viscosity (η) and concentration (C) of sucrose solutions, was proposed. By integrating this empirical equation with the Lucas-Washburn equation, the following equation was derived: L = a⋅exp{-(bC + cC2)}, where 'a', 'b' and 'c' are parameters. This equation was fitted to the dataset of L and C, covering C values from 0 to 60 % w/w standard sucrose solutions, resulting in a coefficient of determination of 0.9987. The plot of L against C was observed to closely follow a linear line, with a fitting providing a coefficient of determination of 0.9986. The sucrose contents in samples, such as soft drinks, syrups, and sugarcanes, determined using the imbibition length method and conventional refractometry, were in statistical agreement via the paired t-test at the 95 % confidence level. This method is simple, instrument-free, requiring only a small amount of safe red food dye, and can be conducted on-site.

Capillary surface modification using millimolar levels of aminosilane reagent for highly efficient separation of phenolic acids and flavonols by capillary electrophoresis with UV detection.

INTRODUCTION: Phytochemical analysis of phenolic acids and flavonols poses a challenge, necessitating the development of an efficient separation method. This facilitates the quantification of these compounds, yielding valuable insights into their benefits. OBJECTIVE: To develop a highly effective separation of phenolic acids and flavonols by capillary electrophoresis and ultraviolet (UV) detection through the modification of the capillary surface using 3-aminopropyltriethoxysilane (APTES) at millimolar concentrations. METHODS: The capillary surface is modified with 0.36 mM-APTES solution. The electrolyte is 20.0 mM borate buffer (pH 9.0). Separation performance (plate number N, resolution Rs ), stability, and reproducibility of the coating procedure are evaluated using the analysis of phenolic acids, rutin and quercetin. RESULTS: The modified capillary provided efficient separation with plate numbers N ≥ 1.0 × 104 m-1 and resolution Rs ≥ 0.8 for all pairs of adjacent peaks of the separation of five selected phenolic acids, rutin, quercetin, caffeine and methylparaben (as internal standard). The precisions of the relative migration times for 17 consecutive analyses of samples over 3 h were 1% relative standard deviation (RSD) for rutin and 7% RSD for quercetin. The analysis of rutin and quercetin in 12 dietary supplement product samples only required a simple dilution step for sample preparation. CONCLUSION: A straightforward modification technique utilising millimolar concentrations of APTES resulted in highly efficient separation of phenolic acids, rutin and quercetin, accompanied by high precision and surface stability. The modified capillary proved successful in analysing rutin and quercetin content in dietary supplements.

Transparent Cross-Flow Platform as Chemiluminescence Detection Cell in Cross Injection Analysis.

This work presents the use of a transparent 'Cross Injection Analysis' (CIA) platform as a flow system for chemiluminescence (CL) measurements. The CL-CIA flow device incorporates introduction channels for samples and reagents, and the reaction and detection channels are in one acrylic unit. A photomultiplier tube placed above the reaction channel detects the emitted luminescence. The system was applied to the analysis of (i) Co(II) via the Co(II)-catalyzed H2O2-luminol reaction and (ii) paracetamol via its inhibitory effect on the catalytic activity of Fe(CN)63- on the H2O2-luminol reaction. A linear calibration was obtained for Co(II) in the range of 0.002 to 0.025 mg L-1 Co(II) (r2 = 0.9977) for the determination of Co(II) in water samples. The linear calibration obtained for the paracetamol was 10 to 200 mg L-1 (r2 = 0.9906) for the determination of pharmaceutical products. The sample throughput was 60 samples h-1. The precision was ≤4.2% RSD. The consumption of the samples and reagents was ca. 170 µL per analysis cycle.

Multi-well plate as headspaces for paper-based colorimetric detection of sulfur dioxide gas: An alternative method of sulfite titration for determination of formaldehyde.

This work describes the analysis of formaldehyde using a 96-well microplate as multiple headspaces for the separation of sulfur dioxide gas generated from the sulfite remaining after its reaction with the formaldehyde in the sample. The quantitation of the gas is by colorimetric detection of an indicator paper placed over the microplate. The samples are aqueous extracts of various foods that are possibly adulterated with formaldehyde. A known excess amount of sulfite is added to the extract solution aliquoted in the well. The remaining sulfite is acidified with hydrochloric acid to generate sulfur dioxide gas which diffuses through the headspace above the solution to be absorbed at the moist strip of the indicator paper placed over the mouth of the wells. Anthocyanins extracted from the butterfly pea flower is used as the pH indicator giving a color change from the increase of hydrogen ions by hydrolysis of the absorbed sulfur dioxide gas. The exposed paper strip is scanned, and the digital images of the colored region analyzed using ImageJ software. The optimized method has a linear range of 200-1000 mg L-1 formaldehyde with limit of detection ((2.57*SD of intercept)/(slope of calibration line)) of the aqueous extract of 40 mg L-1 and coefficient of determination (r2) > 0.9979. Samples of fresh produce, such as seafood, meat, and vegetables, and various processed food were analyzed for their possible formaldehyde content. The results obtained from the headspace paper-based colorimetric detection are not statistically different from the values obtained from the titration method by paired t-tests.

A simple cost-effective paper-based electrochemical device for detection of adulterated sibutramine in slimming products.

This work presents the first paper-based electrochemical device, or ePAD, for direct detection of adulterated sibutramine in slimming products. The ePAD was fabricated using a screen-printing technique for defining the hydrophilic area for sample loading and for the working, reference and counter electrodes. The ePAD gave reproducible responses comparable to both conventional rod electrodes and commercial screen-printed electrodes (SPEs). Use of paper to fabricate the ePAD device provides advantages over the conventional SPE platforms (e.g. glass, ceramics and polymers) in terms of biocompatibility, strong capillary action and environmental friendliness. To detect sibutramine, square wave voltammetry was employed after sample loading on the circular hydrophilic area. The linear range is 2.51 to 83.7 mg L-1 sibutramine, with a precision of 6 %RSD (n = 3) and an instrumental limit of detection (3SD of intercept/slope) of 2.46 mg L-1 sibutramine. Recovery of spiked samples ranged from 83 to 116%. The samples were capsules, slimming coffee powders and nutraceutical beverages. The samples were appropriately diluted to give concentrations within the linear calibration range. Filtration of undissolved solids found with the capsules and coffee powder samples was not required, demonstrating that the method is not susceptible to solid particles. The ePAD is cost-effective (

Silica nanolayer coated capillary by hydrothermal sol-gel process for amines separation and detection of tyramine in food products.

A hydrothermal sol-gel method for reproducible formation of silica nanolayer on the wall of silica capillaries was developed for electrochromatography. The formulation was optimized by observation of uniform gel formation on an optical microscope. The variables of the formulation include types of solvent, water-TEOS ratio, CTAB and urea contents, and mixing method. The procedure produced a coating of silica ca. 100 nm thick layer on the wall of the capillary. Surface morphology of the coating was characterized by SEM, contact angle and chemical composition by FT-IR spectroscopy and X-ray powder diffraction. The coating reduced the electroosmotic mobility producing enhanced separation performance. Eight standard amines (including tyramine and benzhydrylamine, as an internal standard) were separated with peak resolution Rs ≥ 2 for all adjacent peaks and plate number N ≥ 3.0 × 104 m-1. Calibration was linear from 5 to 200 µg L-1, with r2 > 0.9985 and instrumental LOD of 4.9 µg L-1. Five samples of food products were diluted and analyzed for the amines using the coated capillary and only tyramine was detected. Intra-day and inter-day precisions were less than 1.2%RSD. Percent recoveries of spiked tyramine in samples were 95 ± 3 to 106 ± 7% (n = 3).

Disposable Microchamber with a Microfluidic Paper-Based Lid for Generation and Membrane Separation of SO2 Gas Employing an In Situ Electrochemical Gas Sensor for Quantifying Sulfite in Wine.

This work presents a fully disposable microchamber for gas generation of a sample solution. The microchamber consists of a cylindrical well-reactor and a paper-based microfluidic lid (µFluidic lid), which also serves as the reagent loading and dispensing unit. The base of the reactor consists of a hydrophobic membrane covering an in-house graphene electrochemical gas sensor. Fabrication of the gas sensor and the three-layer µFluidic lid is described. The µFluidic lid is designed to provide a steady addition of the acid reagent into the sample solution instead of liquid drops from a disposable syringe. There are three steps in the procedure: (i) acidification of the sample in the reactor to generate SO2 gas by the slow dispensing of the acid reagent from the µFluidic lid, (ii) diffusion of the liberated SO2 gas through the hydrophobic membrane at the base of the reactor, and (iii) in situ detection of SO2 by cathodic reduction at the graphene electrode. The device was demonstrated for quantitation of the sulfite preservative in wine without heating or stirring. The selectivity of the analysis is ensured by the combination of the gas-diffusion membrane and the selectivity of the electrochemical sensor. The linear working range is 2-60 mg L-1 SO2, with a limit of detection (3SD of intercept/slope) of 1.5 mg L-1 SO2. This in situ method has the shortest analysis time (8 min per sample) among all voltammetric methods that detect SO2(g) via membrane gas diffusion.

A ninety-six well plate as headspaces with moist starch indicator paper as a cover for the determination of ascorbic acid by iodate oxidation and formation of volatile iodine.

This work presents the use of a 96-well plate as headspaces for the determination of ascorbic acid in samples loaded in the 96-well plate. Ascorbic acid in the sample is oxidized to iodide by the addition of excess acidic iodate solution into the well. The iodide is further oxidized by the remaining iodate to molecular iodine. A single sheet of moist starch indicator paper is immediately placed over the 96-well plate after the addition of the iodate with the moisture forming a gas seal. The iodine gas in each well diffuses through the headspace to react with the starch paper producing circular areas of a colored starch-iodine complex. After 15 min the indicator paper is scanned, and the digital images of the complex are analyzed by using ImageJ software to obtain blue intensity values. The precision of the intensity values from 12 wells containing 20 µL of 2.84 mM standard ascorbic acid is <2% relative standard deviation. Optimal conditions for detection were investigated, including the starch concentration, the acidic iodate reagent, and the measurement time. The linear calibration range of ascorbic acid is 0.284-2.84 mM, based on the plot of concentration vs. -log(reflectance). The coefficient of determination (r2) is >0.998. Samples of fruit juice and dietary supplements were analyzed for their ascorbic acid contents. The results obtained from the headspace reflectance method are not statistically different from values obtained from the titration method using paired t-tests (α = 0.05).

Simple gunshot residue analyses for estimating firing distance: Investigation with four types of fabrics.

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.

Experimental determination of phase ratio of C8 columns employing retention factors and octane-mobile phase partition coefficients of homologous series of linear alkylbenzenes.

This work proposes an experimental method for the estimation of the phase ratio of reversed-phase C8 columns by employing the equation log(k)=alog(Kom)+log(Φ), where k is the retention factor, Komis the octane-mobile phase partition coefficient, a is a proportionality constant and Φ is the phase ratio (defined as volume ratio of the stationary phase to the mobile phase). The immiscible liquid octane and mobile phase are chosen as the surrogate model for the C8 stationary phase and mobile phase of the chromatographic system. The octane-mobile phase is used for measuring the partition coefficient Kom of six compounds of the homologous series of linear alkylbenzenes, viz. benzene, toluene, ethylbenzene, propylbenzene, butylbenzene and pentylbenzene. The distribution of a compound between the octane and mobile phase is proposed to simulate the partitioning process in the chromatography. The retention factor k of each compound is measured using the same mobile phase for two C8 columns (Zorbax Eclipse XDB-C8 and Symmetry C8). The set of data of k and Kom is fitted to the above linear equation to give the best-fit values of a and log(Φ) for each column and various mobile phase compositions (methanol-water or acetonitrile-water). The regression analyses have coefficients of determination r2 > 0.992. This observed linear relationship can therefore be expressed as k=KomaΦ. The experimental values of Φ for the C8 columns are in the range of 0.206 to 0.842, with a from 0.544 to 0.811, respectively.

Genotype-Phenotype Correlation of ß-Thalassemia in Malaysian Population: Toward Effective Genetic Counseling.

Effective prevention of ß-thalassemia (ß-thal) requires strategies to detect at-risk couples. This is the first study attempting to assess the prevalence of silent ß-thal carriers in the Malaysian population. Hematological and clinical parameters were evaluated in healthy blood donors and patients with ß-thal trait, Hb E (HBB: c.79G>A)/ß-thal and ß-thal major (ß-TM). ß-Globin gene sequencing was carried out for 52 healthy blood donors, 48 patients with Hb E/ß-thal, 34 patients with ß-TM and 38 patients with ß-thal trait. The prevalence of silent ß-thal carrier phenotypes found in 25.0% of healthy Malaysian blood donors indicates the need for clinician's awareness of this type in evaluating ß-thal in Malaysia. Patients with ß-TM present at a significantly younger age at initial diagnosis and require more blood transfusions compared to those with Hb E/ß-thal. The time at which genomic DNA was extracted after blood collection, particularly from patients with ß-TM and Hb E/ß-thal, was found to be an important determinant of the quality of the results of the ß-globin sequencing. Public education and communication campaigns are recommended as apparently healthy individuals have few or no symptoms and normal or borderline hematological parameters. ß-Globin gene mutation characterization and screening for silent ß-thal carriers in regions prevalent with ß-thal are recommended to develop more effective genetic counseling and management of ß-thal.

Dual-Purpose Photometric-Conductivity Detector for Simultaneous and Sequential Measurements in Flow Analysis.

This work presents a new dual-purpose detector for photometric and conductivity measurements in flow-based analysis. The photometric detector is a paired emitter-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 × 2 × 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 Jaffé reaction using the PEDD detector, and the conductivity of the urine, as measured by the C4D detector, is expressed in millisiemens (mS cm-1).

Contactless conductivity sensor employing moist paper as absorbent for in-situ detection of generated carbon dioxide gas.

This work presents an unconventional use of capacitively coupled contactless conductivity detector (C4D) for detection of gas absorption by moist paper with potential application for chemical analysis. To be suitable for measuring conductivity of moist paper absorbent, the C4D sensor was therefore designed in planar configuration. A layer of dry filter paper, only 20 mm × 25 mm in size, was placed on the C4D sensor and the device installed inside a specifically designed vaporization chamber. A vial (16 mm i.d., 8 mm high) containing a 150-µL solution of sodium bicarbonate was placed alongside. The filter paper was loaded with 110 µL of deionized water through an injection hole in the cover lid. A 100-µL aliquot of 2 M hydrochloric acid solution was directly dispensed into the vial through a second hole in the lid to generate CO2 gas from the bicarbonate solution. It was observed that the C4D sensor gave real-time response that corresponded to the absorption of the gas and subsequent production of H+ and HCO3- in the moist paper. The monitored signal reached a constant value at 160 s after the addition of the acid. Chemistry of the absorption process and equivalent circuit for the C4D are proposed. Direct measurement of cement powder was chosen to demonstrate the potential use of this device for quantifying the CaCO3 content of the cement. The calibration curve for 0.5-3 mg CaCO3 was linear for signals recorded at 160 s: Vdc = (0.172 ± 0.005) · (mg CaCO3) + (0.016 ± 0.009), with coefficient of determination of 0.9965. Linear calibrations were also observed when the signals were monitored at various time less than 160 s. The limit of quantitation (3 SD of intercept/slope) was 0.17 mg CaCO3. The method provided acceptable precision with %RSD of 4.6 (2 mg CaCO3, n = 10).

Development of a Simple Reversible-Flow Method for Preparation of Micron-Size Chitosan-Cu(II) Catalyst Particles and Their Testing of Activity.

A simple flow system employing a reversible-flow syringe pump was employed to synthesize uniform micron-size particles of chitosan-Cu(II) (CS-Cu(II)) catalyst. A solution of chitosan and Cu(II) salt was drawn into a holding coil via a 3-way switching valve and then slowly pumped to drip into an alkaline solution to form of hydrogel droplets. The droplets were washed and dried to obtain the catalyst particles. Manual addition into the alkaline solution or employment of flow system with a vibrating rod, through which the end of the flow line is inserted, was investigated for comparison. A sampling method was selected to obtain representative samples of the population of the synthesized particles for size measurement using optical microscopy. The mean sizes of the particles were 880 ± 70 µm, 780 ± 20 µm, and 180 ± 30 µm for the manual and flow methods, without and with the vibrating rod, respectively. Performance of the flow methods, in terms of rate of droplet production and particle size distribution, are discussed. Samples of 180 µm size CS-Cu(II) particles were tested for catalytic reduction of 0.5 mM p-nitrophenol to p-aminophenol by 100-fold excess borohydride. The conversion was 98% after 20 min, whereas without the catalyst there was only 14% conversion.

Simple and fast fabrication of microfluidic paper-based analytical device by contact stamping for multiple-point standard addition assay: Application to direct analysis of urinary creatinine.

In this work, a microfluidic paper-based analytical device (µPAD) for simultaneous multiple-point standard addition assay was fabricated by rubber stamping the hydrophobic barrier pattern onto a laboratory filter paper. The µPAD has a central zone from which an applied sample flows into eight surrounding narrow channels to which had been added the standard solutions. Each channel is connected to a circular area loaded with the reagent. The opposite end of this reagent zone is connected by second narrow channel to the final circular detection zone. The µPAD was applied to the measurement of creatinine in human urine. After addition of a urine sample, the orange-colored product arising from the Jaffé reaction is formed at the eight detection zones. A digital image of the µPAD is then recorded and the ratio of the red/green (R/G) intensity obtained using the ImageJ™ program is used in the quantitation of creatinine. The normal standard addition calibration line is constructed using the intensity ratio against the added creatinine concentrations (50-1000 mg L-1). Good linearity was achieved (r2 ˃ 0.99). There were no significant differences between the creatinine content using an HPLC method (paired t-test at 95% confidence, tstat = 1.78, tcritical = 2.26, n = 10). The use of simultaneous multiple-point standard addition calibration allows rapid determination of creatinine in urine with elimination of matrix interference.

Rapid measurement of indole levels in Brassica vegetables using one millilitre binary organic extraction solvent and capillary electrophoresis-UV analysis.

INTRODUCTION: Brassica vegetables contain high levels of indole compounds which have been found to provide health benefits, especially as cancer-preventive agents. An efficient and rapid method using solvent extraction with capillary electrophoresis (CE) and ultraviolet (UV) detection was developed for the determination of four major indoles from four types of Brassica vegetables. MATERIALS AND METHODS: Freeze-dried samples of four Brassica vegetables, i.e. broccoli, cauliflower, Chinese cabbage and cabbage, were selected. Hence, 1 mL of the binary solvent dimethylformamide (DMF)-methanol, 4:1 (v/v), was used for sample extraction. The extracts were diluted with the running buffer and directly analysed using CE with UV detection of four indole compounds. RESULTS: The binary solvent DMF-methanol, 4:1 (v/v) was selected from studies of the extraction efficiency of standard indoles spiked in ivy gourd (as the negative control sample) and using diphenylamine as the internal standard. Recovery was 80(±10)-120(±3)% for the four indoles: indole-3-carbinol (I3C), indole-3-acetonitrile (I3A), indole-3-acetic acid (IAA), and 3,3'-diindolylmethane (DIM). For direct analysis suitable dilution of the extract with the running buffer was required. The linear range of the quantitation is 0.75-25.0 µg/mL, limit of detection (LOD) of 0.14-0.52 µg/mL and r2 > 0.998. The amount of indole in the Brassica vegetables are in the order I3C > > IAA, I3A > DIM. CONCLUSION: A rapid method for extraction and quantitation of four indoles in four Brassica vegetables using CE with UV detection was developed. It has the potential as an efficient technique for generating data for use in agricultural and nutritional studies.

Contactless conductivity detector from printed circuit board for paper-based analytical systems.

This work presents a capacitively coupled contactless conductivity detector (C4D) etched out from a printed circuit board (PCB) as potential sensor for paper-based analytical systems. Two lines of any desirable pattern forming 35-µm thick planar copper electrodes were produced on a PCB plate (40 mm × 60 mm) by photolithography. The final PCB plate was covered with polypropylene film to serve as the insulating layer for the C4D detector. The film also protected the copper electrodes from corrosion. Electrodes made in this planar geometry make the PCB-C4D suitable as sensor for flat devices such as paper-based analytical devices. For this work, plain paper strips were employed as sample reservoir and as fluidic channel without hydrophobic pattern. A dried paper strip was first placed over the sensor, followed by dispensing a fixed volume of the liquid sample onto the paper. Entrapment of the liquid sample in the paper strip leads to reproducible size and position of the detection zone of the sample liquid for the capacitive coupling effect. High precision was obtained with %RSD ≤1% (n = 18) for standard solutions of KCl. Soil suspensions could be analyzed without prior filtration by placing a drop onto the paper strip extending away from the detector zone. The paper strip filtered out soil particles at the surface of the paper. Therefore, only soil filtrate moved towards the detection zone by lateral flow. The C4D detection using paper strip showed high tolerance to soil suspension with turbidity up to 6657 NTU, offering direct analysis of soil salinity. Cleaning with moist tissue paper between samples is adequate even for dirty samples such as soil suspension. We also monitored conductivity of acid-base reaction in the microfluidic paper channels, which was later applied to the quantification of bicarbonate in water and in antacid tablet ("Soda Mint Tablet").