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The purpose of this study was to study the effect of the percentage of the addition of conductivity material in phosphorylation starch to modify GCE (glassy carbon electrode) for detection of Cr(VI). In this study, the technique used is DPV (Differential Pulse Voltammetry). The conductivity material used in this study is activated carbon and Fe3O4 nanoparticles. The method used is an optimization of conductivity material in phosphorylation starch and determination of the performance of the obtained sensor. The optimum percentage of conductivity materials, both activated carbon and Fe3O4 nanoparticles, in the phosphorylation starch matrix is 5%. The form of amorphous activated carbon and the structure trigonal of Fe3O4 nanoparticles affects the current of Cr(VI). The addition of conductive material increases the current of Cr(VI) and shifts the peak potential to the left. The performance of PSC1 sensor is a detection limit of 5,09 ppm and sensitivity of 0,2098 ppm/µA in the linear concentration range of 2,6 – 15,6 ppm. However, the performance of PSN1 sensor is the detection limit of 3,48 ppm and sensitivity of 0,2120 ppm/µA in the linear concentration range of 2,6 – 18,2 ppm.

The membraneless-gas separation microfluidic paper-based analytical device (ML-GS μPAD), consisting of donor, spacer, and acceptor layers, was developed to monitor total ammonia in fish pond water. The principle of the analysis involved the addition of sodium hydroxide solution to the sample zone in the donor layer containing ammonia/ammonium, and the produced ammonia gas diffuses through the spacer to the detection zone in the acceptor layer containing red rose extract to produce a color change from pink to blue corresponding to the ammonia/ammonium concentration. Under optimum conditions, the proposed method provided good linearity of ammonia in the range concentration of 0-100 mg L

Arrowroot starch membrane-modified glassy carbon electrode were constructed for the determination of uric acid. The membrane consist of arrowroot starch, polyvinyl alcohol, uric acid, and crosslinker. The crosslinker used was sodium tripolyphosphate, citric acid, and glutaraldehyde. Carbon material was added to increase the sensitivity. The composition of membrane influences the electrodes sensitivity. The best composition of arrowroot starch membrane is UA1 using 0.1% uric acid in membrane and STPP as crosslinker. The linearity concentration, sensitivity, and detection limit were 100-500 µM, 0.0509 A/M and 76 µM, respectively.

Mercury is one of the most toxic heavy metals causing harmful effects on the human body; meanwhile, mercury is found in some face cream products to give a whitening effect. The upper limit concentration of mercury in skin-lightening products defined by the Food and Drug Administration (FDA) is under one mg/L as Hg

Untuk meningkatkan kompetensi pedagogik guru kimia di Sekolah Menengah Kejuruan telah dilakukan pelatihan metode analisa kuantitatif konvensional (titrimetri) untuk menentukan parameter kimia air sebagai bentuk kerja sama Pengabdian kepada Masyarakat (PkM). Kegiatan pelatihan dilaksanakan dalam dua cara yaitu daring pada tanggal 23 Juli 2022 berisi penyampaian materi dan praktikum secara luring pada tanggal 6 Agustus 2022. Kegiatan pelatihan daring diikuti oleh 65 peserta berasal dari beberapa daerah di Indonesia. Jumlah peserta dari Jawa Timur paling banyak yaitu 53 orang. Sementara, kegiatan praktikum secara luring dihadiri oleh 39 peserta dimana 36 berasal dari Provinsi Jawa Timur. Keterampilan para peserta yang hadir dinilai menggunakan rubrik keterampilan. Diantara keempat materi titrasi yang dilakukan oleh peserta, titrasi asam-basa untuk menentukan kadar alkalinitas memiliki skor keterampilan tertinggi yaitu 3,8±0,2. Setelah mengikuti kegiatan pelatihan, peserta mengikuti evaluasi akhir kegiatan. Dari hasil evaluasi, kegiatan pengabdian yang dilaksanakan dapat menambah pengetahuan, meningkatkan kemampuan daya nalar, dan kemampuan berkarya secara mandiri. Namun, pelatihan yang diberikan masih kurang dalam meningkatkan kemampuan berfikir dan pembekalan keterampilan lain untuk peserta pelatihan.Training on conventional quantitative analysis methods (titrimetric) for determining water chemistry parameters has been carried out to improve the pedagogical competencies of chemistry for teachers in Vocational High Schools as a form of community service cooperation. The training activities were carried out in two ways, online on July 23, 2022, containing the delivery of training subjects, and offline demonstration class on August 6, 2022. The online training was attended by 65 participants from several regions in Indonesia. The number of participants from East Java was the highest, 53 people. Meanwhile, the offline demonstration class was attended by 39 participants, of which 36 came from East Java Province. The skills of the participants who attended were assessed using the skills rubric. Among the four titration materials carried out by the participants, the acid-base titration to determine alkalinity levels had the highest skill score of 3.8±0.2. After participating in the training activity, participants followed the final evaluation. The evaluation showed that the service activities could increase knowledge, reasoning ability, and skills. However, this training could not increase participants' thinking ability and other skills.

Hydroquinone is an organic antioxidant widely used for skin lightening products which can cause negative impact in excessive use. This study is focused on the development of fast method for the determination of hydroquinone using flow injection-indirect spectrophotometry based on the formation of red complex Iron(II)-phenanthroline. In this method, hydroquinone reduced iron(III) to iron(II) which in the presence of phenanthroline formed Iron(II)-phenanthroline complex detected at maximum wavelength of 510 nm. The common operational and chemical conditions were optimized and the effect of several interfering compounds was also studied to achieve the highest sensitivity with acceptable analysis time. The optimum method performance was obtained under the conditions of 100 µL sample volume, 50 cm mixing coil-1and 75 cm mixing coil-2, 5 ml/min flow rate, 100 mgL -1 Iron(III) concentration, and 0.15 % phenanthroline. Under these conditions the proposed FI-spectrophotometry gave results to linear calibration over the concentration range from 2-100 mgL -1 (y = 0.028x and R 2 of 0.999). The method was not interfered in the presence of vitamin C 1 mgL -1 and resorcinol up to 10 mgL -1 . However, the higher concentration of vitamin C ³10 ppm and resorcinol ³ 20 ppm gave significant error of measurements. Method validation using standard additions gave results to average recovery value of 97.02 %, which indicates that the FI-spectrophotometry method can be used as an alternative method for determining hydroquinone in cosmetic. Key words : Hydroquinone, flow injection, spectrophotometry, iron, phenanthroline.

Curcuma longa , C. xanthorrhiza , C. heyneana , and Zingiber cassumunar contain high curcuminoid and have relatively the similar yellow color. Therefore, that they are potentially adulterated and difficult to differentiate in the form of powder. Hence, it is necessary to characterize the fingerprints compound profile by a simple and rapid method . This research aims to determine fingerprint compound profile of curcuminoid using Thin Layer Chromatography (TLC) and digital image analysis. The result of the research identified that the fingerprint compound profile of curcuminoid on the four rhizomes was obtained by TLC method using silica gel 60 GF 254 as the stationary phase, chloroform:dichloromethane:methanol (13:6:1) as the mobile phase, and observation under UV 254 nm light and citroborate reagent. Thereafter, the digital image analysis was carried out using Image J software according to the gray value and % of RGB (red-green-blue) value. Based on gray value and % of RGB, both Curcuma and Zingiber genera were differentiated through curcumin compound (R f 0.63), demethoxycurcumin (R f 0.34), bisdemethoxycurcumin (R f 0.21). The profile of fingerprint compound on Curcuma longa, C. xanthorrhiza, C. heyneana, and Zingiber cassumunar was differentiated through R f 0.26; R f 0.17; and R f 0.10.

A new analytical device for mercury detection has been developed by doping dithizone on to hydrophobic PTFE (polytetrafluoroethylene) membrane to form a blue dithizone membrane which instantaneously changed to orange color of mercury(II)-dithizonate complex, when this dithizone membrane was contacted to mercury(II) solution. The higher concentration of mercury showed the greater intensity of the orange colour mercury(II)-dithizonate complex. The design and chemicals were optimized to obtain the best performance for mercury measurement. This method is prospective as mercury test kit for simple, low cost, and rapid semi-quantitative method for mercury(II) determination from 1-10 mgL-1 suits for on-site mercury detection and has been applied to cosmetics with satisfactory results.

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.

Methods of obtaining diazinone and chlorantraniliprol in soil samples have been developed. Analytes were extracted using acetonitrile by using an ultrasonic solvent extraction method (USE). The discovery uses high performance liquid chromatography using a UV detector. The optimum conditions for the separation of both pesticides are Acetonitrile composition: Air (60:40), flow rate 0.4 mL / min, and at 220 nm wavelength. The more the amount of acetonitrile in the eluent mixture the faster the retention time in the column. Retention time respectively, chlorantraniliprol 10,525, and diazinon 21,029.

Myrmeleon sp is a typical of insect larva which has been used in Indonesia for diabetes treatment. However, there is no sufficient scientific report explaining the bioactive compounds in this insect. Based on our preliminary research, this insect contained metformin, i.e. one of bioactive compounds for the treatment of type-2 diabetes. Therefore, this study is focused on the development of separation technique using high performance liquid chromatography (HPLC) on a reverse phase C-18 column with UV detection to identify and quantify metformin in methanol extract of Myrmeleon sp. Several parameters of HPLC method were optimized with respect to high resolution of separation and accurate determination of metformin. Satisfied separation was obtained under gradient elution mode using aqueous methanol mobile phase varied from 50-90 % of methanol with flow rate of 0.5 mL/min and detection wavelength of 233 nm. The method performed total separation for all compounds in less than 11 minutes. Spiking technique was chosen for metformin identification and quantitation. Metformin in extract Myrmeleon sp was eluted at retention time (t R ) of 4.095 minutes, similarly with retention time of standard metformin of 4.092 minutes. The quantity of metformin in Myrmeleon sp can be simply determined by comparing the additional area of standard metformin with area of metformin from extract Myrmeleon sp . The results confirmed that methanol extract of Myrmeleon sp contained anti-diabetes compound of metformin of 0.58 mg/g Myrmeleon sp larvae with acceptable coefficient variation of 5.56 %.

Elektroda selektif ion (ESI) metanil yellow tipe kawat terlapis telah dibuat menggunakan bahan aktif aliquat 336-kitosan, bahan pendukung campuran polivinilklorida (PVC), dan pemlastis dioktiloftalat (DOP) dengan perbandingan aliquat 336:kitosan:PVC:DOP = 0,5%:5 %:34,5 %:60% b/b dilarutkan dalam pelarut tetrahidrofuran (THF) (1:3 b/v). Namun, ESI ini belum diuji selektifitasnya. Maka, pada penelitian ini ingin diketahui pengaruh ion asing terhadap kinerja ESI metanil yellow tipe kawat terlapis bermembran aliquat 336-kitosan serta aplikasinya pada sampel tahu. Pengaruh ion asing ditentukan dengan menentukan koefisien selektivitas (K i,j ) membran dengan metode larutan tercampur. Larutan yang diukur mengandung ion utama metanil yellow dengan rentang konsentrasi 10 -5 –10 -2 M dan ion asing benzoat (C 7 H 5 O 2 - ), klorida (Cl - ), dan asetat (CH 3 COO - )dengan konsentrasi tetap 10 -3 M. Hasil penelitian menunjukkan keberadaan ion asing C 7 H 5 O 2 - , Cl - , CH 3 COO - tidak mempengaruhi kinerja ESI yang ditunjukkan oleh nilai K i,j kurang dari 1, dengan urutan selektivitas C 7 H 5 O 2 - >CH 3 COO - >Cl - . Aplikasi pada penentuan kadar metanil yellow secara potensiometri menggunakan ESI metanil yellow tipe kawat terlapis berbasis aliquat 336-kitosan hasilnya dibandingkan dengan metode standar spektrofotometri menggunakan uji-t dengan tingkat kepercayaan 90% menunjukkan hasil tidak berbeda secara bermakna, sehingga ESI ini dapat digunakan sebagai metoda alternatif untuk pengukuran kadar metanil yellow dalam tahu. Kata kunci: Aliquat 336, Elektroda selektif ion metanil yellow, Ion asing, Kitosan,Validasi.

Environmental pollution is an influx of energy substances, living creatures, or other components into the environment so that the quality of the One type of pollutant is heavy metals lead (Pb). Pb of metal in irrigation found in the form of PbOH+, Pb2+, PBSO4, PbCO+, and PbHCO3. Lead can be analyzed using a UV-Vis spectrophotometer and test kit (colorimetry). The Test kit is created by adding a reagent to the sample so that there is a complex bond that occurs between the reagent and lead. The reagent often used in determining lead analysis is dithizone. Has been conducted to determine the activity of dithizone as a metal ion complex Pb+2 using spectrophotometry UV-Vis. Determination of the activity of dithizone in monomers and after forming complex indicates the concentration optimum of reagent dithizone in solvent 2-propanol is 60 ppm. Time measurement and optimum pH of Pb (II)-dithizone complex is 10 minutes in pH 4 for achieved complex stability. Geometry modeling and electronic transitions monomer Dithizone and Pb (II)-dithizone complex are performed in computing using semi-empirical AM1/SCF (ground state) and AM1/TD-SCF (excited state) methods. The results showed the total energy modeling dithizone: 0266 a.u and Pb (II)-dithizone: 1,125 a.u the ground state. The transition type in each molecule indicates the type of transition n → π ⃰ Orbital molecules involved in the excitation of the electron dithizone are HOMO-6/39, HOMO-2/43, HOMO/45, and LUMO/46. Meanwhile, the Pb (II)-Ditizon complex has 3 orbitals are HOMO-4/85, HOMO/89, and LUMO/90 involved.Keywords: Austin Model 1; Modeling; Pb (II)-Dithizone; UV-Vis Spectrophotometry ABSTRAK Pencemaran lingkungan merupakan masuknya zat, energi, makhluk hidup, atau komponen lain ke dalam lingkungan sehingga kualitas lingkungan turun hingga yang menyebabkan lingkungan menjadi kurang berfungsi lagi sesuai dengan peruntukkannya. Salah satu jenis polutan adalah logam berat Timbal (Pb). Logam Pb diperairan ditemukan dalam bentuk PbOH+, Pb2+, PbSO4, PbCO+, dan PbHCO3. Timbal dapat dianalisis langsung menggunakan spektrofotometer UV-Vis dan tes kit larutan (kolorimetri). Tes kit larutan dibuat dengan cara menambahkan suatu pereaksi pada sampel sehingga terbentuk adanya ikatan kompleks yang terjadi antara pereaksi dengan timbal. Pereaksi yang sering digunakan dalam penentuan analisis timbal yaitu ditizon. Telah dilakukan penentuan aktivitas ditizon sebagai pengompleks ion logam Pb+2 secara spektrofotometri UV-Vis. Hasil penentuan aktivitas ditizon dalam keadaan monomer dan sesudah membentuk kompleks menunjukan konsentrasi pereaski optimum ditizon, yaitu 60 ppm pada pelarut 2-propanol. Pengukuran waktu dan pH optimum pembentukan kompleks menunjukkan bahwa pada waktu 10 menit di pH 4 tercapainya kestabilan kompleks. Pemodelan geometri dan transisi elektronik monomer ditizon dan kompleks Pb(II)-ditizon dilakukan secara komputasi menggunakan metode semi empiris AM1/SCF (ground state) dan AM1/TD-SCF (excited state). Hasil menunjukan energi total pemodelan ditizon: 0.266 a.u dan Pb(II)-ditizon: 1.125 a.u pada ground state. Tipe transisi pada masing-masing molekul menunjukan tipe transisi n→π⃰ Orbital molekul yang terlibat dalam eksitasi elekteron ditizon, yaitu HOMO-6/39, HOMO-2/43, HOMO/45, dan LUMO/46. Sementara itu, kompleks Pb(II)-ditizon terdapat 3 orbital, yaitu HOMO-4/85, HOMO/89, dan LUMO/90 yang terlibat.

Nitrogen is an essential nutrient required by majority of plants to enhance metabolic processes for growing. Insufficient supply of nitrogen leads to severe plant disorders in flowering and fruiting; however, there are many false fertilizers available in markets. This project is focused on developing a smart method as a means for quality detection of nitrogen fertilizer. The smart ammonia analyzer was constructed on a normal smartphone which filled with Qpython3 software functions as an information processing application to analyze the level of nitrogen-ammonium and Color Grab application to process the RGB image of coloured product reaction of nitrogen-ammonium to be measured. The image of blue indophenol as the coloured product of the nitrogen was developed on a paper containing phenate reagent by releasing nitrogen ammonia from sample. The measurement process using the constructed “Smart Ammonia Analyzer’ involving taking image by smartphone camera, measuring image intensity on position with RED readings, and analyzing process to change the RED-value to concentration of nitrogen-ammonium. The chemicals used for colour formation of blue indophenol were 0.2 M NaOCl, 0.5 M HCl, 0.003 M MnSO4 M, and 2 M phenate with 0.1 M of NaOH for releasing agent of nitrogen fertilizer as ammonia. The developed smart ammonia analyzer resulted linear relation between the absorbance of blue indophenol image to concentration of nitrogen ammonia (y = 0.0181x + 0.2834, R2 = 0.9726) and has been successfully applied to nitrogen fertilizer. Development of smart ammonia analyzer has been achieved to provide an easy, inexpensive, and fast device for detecting quality of nitrogen fertilizer with satisfactory results.

This research is focused on the development of a new indirect spectrophotometry for the determination of hydroquinone in cosmetics based on the capability of hydroquinone as reducing agent for chromium(VI). The principle of the determination is based on the decrease of the color intensity of the red-violet complex of chromium(VI)-Diphenylcarbazide (DPC) due to the reduction of the available chromium(VI) by hydroquinone to chromium(III). Thus, only the remaining chromium(VI) reacted with DPC to form a red-violet complex detected by spectrophotometry at 542 nm. All chemical parameters were optimized with respect to sensitivity and selectivity of measurements. Under the obtained optimum conditions (reaction time of 5 minutes, chromium(VI) of 1 mgL−1, sulfuric acid of 0.05 M, and DPC of 0.0125%), the method gave linear calibration for hydroquinone concentration from 0.2-2.5 mgL−1 (R2 = 0.996). The proposed method also provided good sensitivity shown by low values of LoD and LoQ (0.07 and 0.1 mgL−1) and satisfactory selectivity towards the common interfering ions present in cosmetics. Satisfactory results with recoveries of close to 100 % were observed when the method was applied to facial whitening and black spot removal cosmetics. This result suggests that the developed method is able to be used for monitoring of hydroquinone in skin lightening cosmetics.

A new spectrophotometric method for mercury determination has been developed based on the complexation of mercury(II) in ascertained excess of thiocyanate. The remaining thiocyanate is reacted with iron(III) to form a red iron(III)-thiocyanate complex which gave maximum absorbance at 460 nm. The concentration of mercury(II) is inversely proportional to the decrease absorbance of the complex. The method was optimized to the concentrations of thiocyanate and iron(III). Selectivity of the method has also studied based on percent recovery of mercury(II) in the presence of common metal ions in the tailing waters of gold mine. Under the optimum conditions, the method showed linear correlation to mercury(II) concentration from 1-30 mg L−1 with detection limit of 0.58 mg L−1. The method was not interfered in the presence of all metal ions studied up to 50 mg L−1, except of silver which was tolerated at 10 mg L−1. The developed method has been satisfactorily applied for mercury(II) determination in synthetic and tailing waters of gold mine samples.

Modifications of glassy carbon electrodes (GCE) as working electrodes have been carried out by polyvinyl alcohol (PVA)-Fe3O4 membranes. The PVA-Fe3O4 membrane was superimposed on the surface of a glassy carbon electrode. This study influences the percentage of paracetamol in the membrane, the effect of modulation time, the effect of modulation amplitude, the effect of scan rate, the effect of pH and supporting electrolytes. The performance evaluation of the modified electrode was based on a voltammogram of cyclic voltammetry (CV) and the analysis was carried out with a differential pulse voltammetry (DPV) method. The effect of pH was studied in the range of 2-7 by Britton – Robinson buffer. The results showed that the percentage of paracetamol in the membrane affected the diffusion of current. The best performance of GCE modified was produced by a membrane with paracetamol percentage of 3% (w/w). The optimum operational condition of the instrument was at modulation amplitude of 10 mV, the modulation time of 0.1 s and the scan rate of 12.5 mV/s. pH affects the shift of the anodic peak of paracetamol in a more negative direction. The results of the analysis of paracetamol using DPV method showed that more sensitivity was achieved when phosphate buffer as a supporting electrolyte was used. The sensitivity of the GCE modified by the PVA-Fe3O4 membrane was 0.2922 µA/µM in the linear concentration range of 0-100 µM and limit of detection (LoD) of 8 µM.

One point of the halal concepts is the food does not contain any lard or any pigs derivatives. UV-vis spectrophotometry using natural dyes, among other methods, can be developed for animal fat analysis. One factor that influence the analysis is the solubility of animal fats and natural dyes in organic solvents. This research was conducted to study the differences of UV-vis spectrum profile in animal fats (chicken, beef, lamb, pork) using various natural dyes (namely Curcuma longa Linn., Curcuma zanthorriza, Curcuma heyneana, Zingiber montanum, Uncaria, Caesalpinia sappan, and Areca catechu) in different type of solvents. The research consists of four main steps: 1) screening of plant dyes in several solvents with different polarity, 2) screening of animal fat in several solvents with different polarity, 3) screening of animal fats mixed with plant dyes in selected solvents, and 4) analysis of animal fats mixed with plant dyes in selected solvents by UV-Vis spectrophotometry. The results showed that plant dyes from C. longa Linn., C. zanthorrhiza, A. catechu, and Uncaria, well as all animal fats used in this work, were soluble in ethyl-acetate and isopropanol. UV-vis spectrum profile of the animal fats with turmeric dyes in ethyl-acetate for chicken, beef, pork, and lamb fats, shows peaks at λ of 484, 792, 488.5, and 741 nm with absorbance of 3.913, 0.816, 3.524, and 0.175 respectively. Meanwhile in isopropanol, the profile for chicken, beef, pork, and lamb fats have λ of 751, 787, 712, 499 nm with absorbance of 0.007, 1.012, 0.479, and 3.913, respectively. Therefore, the UV-vis spectrum profile of animal fat with C. longa Linn dyes in ethyl-acetate can distinguish lard from the beef and lamb fats. In isopropanol, the lard cannot be distinguished from the chicken and beef fats, but it can differentiate lard from the lamb fats. The C. zanthorrhiza dyes in ethyl-acetate cannot distinguish lard from the chicken, beef, and lamb fats, but C. zanthorrhiza dyes can distinguish lard from the beef fat using isopropanol as the solvent. For A. catechu and Uncaria dyes in ethyl-acetate and isopropanol, they all cannot distinguish lard from the chicken, beef and lamb fats.

In order to practice green chemistry, a simple and safe spectrophotometric method for iodide determination has been successfully developed based on the formation of a blue starch-iodine complex . Iodide was oxidized to form iodine prior to the addition of a starch solution, and the blue s tarch-iodine complex was directly detected spectrophoto-metrically at a wavelength of 615 nm. The chemical parameters, such as type, reaction time, as well as concentration of oxidizing agents and solution pH were optimized with respect to sensitivity and analysis time. The method showed optimum results under iodate oxidant with a mol ratio of IO 3 - :I - =1:3, reaction time of 5 minutes, and solution pH of 5. Under the se optimum conditions, the method showed linierity measurements from 5-4 0 mg/L iodide with a correlation ( R 2 ) of 0.9 889 . This technique offers a simple, safe, accurate, and relatively fast method for iodide determination, which is prospective for monitoring iodide samples.

Research of speciation analysis Cr(III) and Cr(VI) using hypochlorite and peroxide oxidants with Visible Spectrophotometry has been proposed. This research was carried to obtain optimum conditions of oxidation process Cr(III) into Cr(VI) and the formation of Cr(VI)-Diphenylcarbazide complex to the wavelength, complexing time, oxidizing agent (oxidant) concentration, oxidation temperature, pH, and the influence of foreign ion, so it can be proposed as an alternative method for speciation analysis of Cr(III) and Cr(VI). Optimization results show that the maximum wavelength of Cr(VI)-diphenylcarbazide complex is 542 nm by the stable complex time 16-30 minutes using a hypochlorite (HOCl) oxidant concentration 1 x 10 -3 M, temperature 60 o C and pH 1. This method is compared with standard method. The presently developed method is more simple and faster than standard method. Regarding accuracy and precision, the method is quite comparable with the standard methods. Key words: speciation, Cr(III), Cr(VI), oxidant, hypochlorite, spectrophotometry VIS

Methacrylate-based monolithic columns have been prepared in silanized silicosteel column (100 ´ 0.5 mm id) by in situ polymerization reaction, using glycidyl methacrylate (GMA) as monomer, ethylene dimethacrylate (EDMA) as crosslinker, porogen (1-propanol, 1,4 butandiol, water) and initiator AIBN. Monolith poly-(GMA-co-EDMA) was then modified with diethylamine and benzyl chloride to obtain ammonium quartener as strong anion exchanger. From the characterization of 4 monolith in this study, monolithic columns poly-(GMA-co-EDMA) with %T 40, %C 25 and polymerization time 24 h has good mechanical stability and permeability, adequate molecular recognition sites (indicated by binding capacity value of 10,119 mg/mL), and has good proportion of flow throughpore and mesopores (45,04% and 41,32% respectively). It can successfully separate the mixture sample of anion consisting of fluoride, bromide, sulfate and nitrate ions by indirect UV detection .

Serious disorders of iodine deficiency can cause irreversible cretinism, pregnancy complications, goiter, compromised thyroid hormone production, mental impairment and decreasing cognitive function. In order to detect early indication of Iodine Deficiency Disorders (IDD) a development of simple spectrophotometric method for iodide determination is proposed using hydrogen peroxide (H 2 O 2 ) as an oxidizing agent. Determination of iodide is based on the oxidation reaction of I - to I 2 that form blue complex compound I 2 -starch. The blue color intensity of the complex I 2 -starch produced was measured at wavelength of 611 nm. Several parameters were optimized: complex formation and oxidation time of iodide, the optimum concentration of oxidizing agent, H 2 SO 4 , starch and effect of interfering ions (chloride, bromide, thiocyanate), with optimum conditions obtained of respectively: 10 minute, H 2 O 2 0.1 M, H 2 SO 4 0.05 M, starch 0.2 %. Under these condition, the method showed linearity of 5 - 60 ppm, limit of detection and quantification of 0.62 and 2.09 mg/L, respectively. This method has been successfully applied to synthetic and urine samples and can be recommended for the detection of iodide in patients hyperthyroidism and KI tablets.

In this paper, we describe a Microfluidic Paper-based Analytical Devices (μPADs) for the simultaneous quantification of two important biomarkers of kidney function in blood. This paper provides a simple, disposable, portable, and inexpensive colorimetric method for the quantification of Blood Urea Nitrogen (BUN) and serum creatinine (sCRE). BUN detection is based on the Berthelot reaction, in which urea is converted to ammonium by the use of urease, ammonium ion which then reacts with a mixture of salicylate, sodium nitroprusside, and hypochlorite to yield a blue-green chromophore. sCRE detection is based on the Jaffe reaction, in which sCRE under alkaline conditions react with picrate ions forming an orange complex. The intensity of the color formed is proportional to the BUN & sCRE concentration in the sample. Various experimental parameters were optimized to achieve the best performance of the μPADs. There were no significant differences between the results obtained using the μPADs and a comparative method.

Formaldehyde is a toxic and dangerous compound that is still often used freely by irresponsible traders or producers as food additives. At low concentrations, formaldehyde can cause eye, nose, throat and skin irritations. Exposure to large amounts of formaldehyde can cause severe pain, vomiting, coma, and even death. According to the International Program on Chemical Safety (IPCS), the threshold for formaldehyde in food that can still be tolerated in adult bodies is 1.5 mg to 14 mg per day while in a drinking water is 0.1 ppm. Determination of formaldehyde generally employ a titration method, which requires a large amount of sample and reagent, and long analysis time. This work aims to determine the formaldehyde in tofu commercially available in traditional markets of Malang City by Sequential Injection Analysis method using acetoacetanilide (AAA) at optimum conditions. Determination of formaldehyde is based on the Hantzsch reaction, which involves a cyclization between AAA and formaldehyde in the presence of ammonia so that it will produce a yellow dihydropyridine derivative product detected at a wavelength of 359 nm. The optimum condition for the formation of the reaction product occurred at an AAA concentration of 0.03 M, an ammonium acetate concentration of 1.5 M, a reaction time of 50 s and a flow rate of 75 µL/s. Excellent sensitivity and accuracy could be attributed to our developed formaldehyde detection method as the detection limit of 4.5 ppb and the recovery values of > 95 were achieved. Low reagent consumption, less waste production, and high throughput analysis are other advantages of our proposed method.

The determination of the antioxidant activity in green tea using FRAP essays developed in a Microfluidic Paper-Based Analytical Device (μPADs) was observed. μPAD was prepared on the chromatographic paper with a suitable pattern and then printed using a solid ink printer. The solid printing was intended to obtain a hydrophobic barrier and a hydrophilic channel on the chromatographic paper. A preliminary study was done to determine the optimum time and temperature used on the penetration of obtaining the hydrophobic barrier to avoid leakage in the channel. Optimization of temperature and time was calculated by the average velocity, the optimum condition was obtained at 120 °C for 90 seconds with an average speed of 0.1 mm.s−1. The green tea samples were prepared by extracting its active compound using demineralized water at 25 °C and 90 °C with 2 hours of immersion time. For the measurement of antioxidant activities, the analysis was carried out by placing 0.5 μl in the detection zone and 5 μl samples into the sample zone μPAD. Then, the color reaction product, which propagates from the sample zone to the detection zone, is processed by Image J software to measure color intensity in CMYK mode. Extracts of green tea samples at 25 °C and 90 °C has a significant difference in antioxidant activity. These results indicate that the method developed in this work can be used as an alternative method for analyzing antioxidant activity in green tea extract. The results of the average amount of antioxidant activity in green tea samples were shown with Fe2+ concentration. High-speed detection, low cost, high accuracy, and ease of use can be attributed to the advantages of our μPAD method.