Kesan penambahan surfaktan tak-ionik kepada kompleks Al(III)-morin dalam penentuan aluminium (III) akues secara spektrofotometri

Dalam kajian ini, kesan surfaktan tak-ionik terhadap kompleks Al(III)-morin telah dijalankan. Surfaktan tak-ionik didapati telah meningkatkan bacaan serapan kompleks Al(III)-morin. Penambahan triton X-100 kepada kompleks Al(III)-morin telah membolehkan penentuan ion Al(III) dalam kuantiti submikrogram pada pH4.00 dijalankan. Bacaan serapan maksimum adalah pada 425 nm dengan serapan molar, ε, 9.31 × 103 l.mol-1.cm-1. Graf kalibrasi bagi penentuan ion Al(III) adalah linear daripada 0.03 hingga 2.0 μg mL-1 dengan had pengesanan 0.015 μg mL-1 telah diperoleh dalam kajian ini. Sisihan ralat relatif (r.s.d) ialah 2.2% bagi kepekatan Al(III) 1.0 μg mL-1. Kesan penambahan ion lain terhadap kompleks Al(III)-morin turut dijalankan dan didapati ion Cu(II), Zn(II) dan Pb(II) memberi gangguan yang lebih berbanding ion-ion lain

THE EFFECTS OF CHANGING MEMBRANE COMPOSITIONS AND INTERNAL ELECTROLYTES ON THE RESPON OF POTASSIUM ION SENSOR

A study on the changing of membrane compositions and internal solution towards the response potassium ion sensor was carried out. Potassium ion sensor based on photocured cross linking poly(n-butyl acrylate) membranes with varying composition of valinomycin (val), sodium tetrakis [3.5-bis(trifluoro-methyl) phenyl] borat (NaTFPB), types ion of internal solution were investigated. Effects of varying composition of val, NaTFPB, types and concentration of internal solution were observed on potassium ion sensor. The effect of higher val composition was lower LOD, wider linear range, lower sensitivity but increase selectivity. Higher NaTFPB compositions lead to lower LOD, higher sensitivity and selectivity. The effect of changing internal electrolyte lead to lower LOD, wider linear response range and higher selectivity according to internal electrolyte consisting Na+, Ca2+ and K+, and sensitivity increase following internal electrolyte with Ca2+, K+ and Na+.Key words: ion sensor, ion selective membrane, ionofor, lipofilik sal

THE EFFECTS OF CHANGING MEMBRANE COMPOSITIONS AND INTERNAL ELECTROLYTES ON THE RESPON OF POTASSIUM ION SENSOR

A study on the changing of membrane compositions and internal solution towards the response potassium ion sensor was carried out. Potassium ion sensor based on photocured cross linking poly(n-butyl acrylate) membranes with varying composition of valinomycin (val), sodium tetrakis [3.5-bis(trifluoro-methyl) phenyl] borat (NaTFPB), types ion of internal solution were investigated. Effects of varying composition of val, NaTFPB, types and concentration of internal solution were observed on potassium ion sensor. The effect of higher val composition was lower LOD, wider linear range, lower sensitivity but increase selectivity. Higher NaTFPB compositions lead to lower LOD, higher sensitivity and selectivity. The effect of changing internal electrolyte lead to lower LOD, wider linear response range and higher selectivity according to internal electrolyte consisting Na+, Ca2+ and K+, and sensitivity increase following internal electrolyte with Ca2+, K+ and Na+. Key words: ion sensor, ion selective membrane, ionofor, lipofilik sal

Simple and Low-Cost On-Package Sticker Sensor based on Litmus Paper for Real-Time Monitoring of Beef Freshness

A simple sticker sensor has been constructed using litmus paper and tests have been conducted to detect the freshness of beef samples. The results show that the sticker sensor can be used to determine the degree of beef freshness, since the color change of the litmus paper and the quality degradation of the beef during storage time had a similar trend, where the decay of the beef could be detected clearly (when the red litmus paper changed to blue). The sticker sensor reacted accurately to the beef's freshness in terms of pH change due to beef deterioration from pH 5.61 to 6.24 and from pH 5.67 to 6.02 as shown by its color change in real time at room and chiller temperature respectively. Thus, the sticker sensor can be used as an effective tool for monitoring the microbial quality of packaged fresh meat that correlates with the increased pH of the beef, where the total viable count (TVC) of 5 x 106 cfu/g or 6.698 log cfu/g correlates with a pH of 6.24. These levels were reached at 10 hrs and 7 days at room and chiller temperature respectively. This study provides a foundation for developing a simple sensor for beef freshness

Penentuan Cepat Toksisitas Logam Perak Menggunakan Bioluminesen Bakteri Laut Aliivibrio fischeri, Beijerinck, 1889 (Gammaproteobacteria: Vibrionaceae)

Rapid determination of toxicity based on changes in the bioluminescent signal of marine bacterium Aliivibrio fischeri (A. fischeri) to evaluate toxicity of Ag(I) has been successfully developed. Assessment of toxicity was designed using inhibition of bioluminescent signal from A. fischeri bacteria, which was exposed with toxic material of Ag(I). This metal ion was utilized as a model of toxic material to evaluate the effects of cytotoxicity on bacteria cell. Measurement of bioluminescent were taken based on differences in bacterial cell signals before and after exposure to Ag(I) ion at an emission wavelength of 488±2 nm. The concentration of bacterial cell was used to assess the toxicity of Ag(I) at optical density (OD600 nm) of 0.78 Abs. The results found that the linear response of Ag toxicity was in the range of 0.05–10 mg/L, with EC50% of 8.42 mg/L for 4 minutes. The repeatability value within the relative standard deviation (RSD) was 2.5-4.7% (n=8).  The results demonstrated that the marine bacteria of A. fischeri have good potential to evaluate toxicity of toxic material in environmental samples. Penentuan cepat toksisitas berdasarkan perubahan sinyal bioluminesen bakteri laut Aliivibrio fischeri (A. fischeri) untuk mengevaluasi toksisitas logam perak (Ag(I)) telah sukses dikembangkan. Penilaian toksisitas didesain berdasarkan penghambatan sinyal bioluminesen bakteri A. fischeri oleh bahan toksik. Ion logam Ag(I) digunakan sebagai model bahan toksik untuk menilai efek sitotiksisitas pada sel bakteri. Pengukuran bioluminesen diambil berdasarkan perbedaan sinyal sel bakteri sebelum dan sesudah diekspos pada ion logam Ag(I) pada panjang gelombang emisi 488±2 nm. Konsentrasi sel bakteri yang digunakan untuk menilai toksisitas Ag(I) pada optikal densitas 600 (OD 600 nm) = 0.78 Abs.  Hasil kajian ditemukan bahwa respons linear toksisitas Ag(I) pada rentang 0.05–10 mg/L, dengan nilai EC50% sebesar 8.42 mg/L pada waktu respons 4 menit dan nilai repeatibilitas toksisitas diperoleh sebesar 2.5-4.7 % RSD (relatif standar deviasi, n=8). Hasil ini menunjukkan bahwa bakteri laut A. fischeri memiliki potensi yang baik untuk menilai toksisitas bahan toksik dalam sampel lingkungan

Application of the cellular oxidation biosensor to Toxicity Identification Evaluations for high-throughput toxicity assessment of river water

Toxicity Identification Evaluation (TIE) is a useful method for the classification and identification of toxicants in a composite environment water sample. However, its extension to a larger sample size has been restrained owing to the limited throughput of toxicity bioassays. Here we reported the development of a high-throughput method of TIE Phase I. This newly developed method was assisted by the fluorescence-based cellular oxidation (CO) biosensor fabricated with roGFP2-expressing bacterial cells in 96-well microplate format. The assessment of four river water samples from Langat river basin by this new method demonstrated that the contaminant composition of the four samples can be classified into two distinct groups. The entire toxicity assay consisted of 2338 tests was completed within 12 h with a fluorescence microplate reader. Concurrently, the sample volume for each assay was reduced to 50 μL, which is 600 to 4700 times lesser to compare with conventional bioassays. These imply that the throughput of the CO biosensor-assisted TIE Phase I is now feasible for constructing a large-scale toxicity monitoring system, which would cover a whole watershed scale

Content determination and health risk assessment of polycyclic aromatic hydrocarbon in fish tissue samples from Perhentian Island, Malaysia

The concentration of polycyclic aromatic hydrocarbon (PAH) in three fish species with different feeding habits and habitat i.e. Lolong (Selar boops), Kerisi (Nemipterus peronii) dan Mengkarong (Trachinocephalus myops) from offshore of Perhentian Island, Malaysia was determined. Three individuals from each species were taken at random and the PAHs contents were determined in the muscles. Ten PAH compounds, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(e)pyrene and dibenzo(a,h)anthracene were determined. PAH in fish tissues was extracted using Soxhlet method and detected using gas chromatography – mass spectrometry (GC-MS). The level of PAH in fish tissue ranged from 17.89 – 42.18 ng/g wet weight and 393.98 – 511.07 ng/g lipid weight. The order of PAH concentration in wet weight was Kerisi (511.07 ng/g)> Mengkarong (409.50 ng/g)> Lolong (393.98 ng/g) but in terms of lipid weight, the order was Kerisi (511.07 ng/g)> Mengkarong (409.50 ng/g)> Lolong (393.98 ng/g). Kerisi has the lowest lipid content of 3.5% compared to Lolong (6.5 %) and Mengkarong (10.3 %). No obvious significant difference (p>0.05) of PAH levels in three fish spesies was observed (ANOVA, p>0.05). There was no significant relationship between lipid content and PAH accumulation in fish. Based on fish consumption rate of 142.2 g/day, the Potency Equivalent Concentration (PEC), which is a carcinogenic potency value for PAH, was found to be ranged from 0.41 – 0.63 ng/g wet weight in all three species of fish. This value is below the limit set by USEPA, which is 0.67 ng/g wet weight for human consumption

Acrylamide optical sensor based on hydrolysis using Bacillus sp. strain ZK34 containing amidase properties

In this work, a new optical screening method for acrylamide was developed. Bacterial Bacillus sp. strain ZK 34 was used to hydrolyse acrylamide to the corresponding acid and ammonia. Nessler’s reagent was used to detect the produced ammonia and the yellow complex formed was treated as signal. Bacterial pellet was immobilised in the alginate membrane. The optimum composition of alginate used is 2%. The mass ratio of alginate:bacterial of 1:0.5 gave the optimum respond. Optimum concentration for NaOH and Nessler’s reagent were 0.075 M and 2.5 mM, respectively. The yellow complex of mercury (II) amido-iodine formed was directly proportional to the concentrations of acrylamide up to 50.00 ppm with the limit of detection of 1.30 ppm. This sensor shows a good reproducibility which the relatives standard deviation (RSD) values from 3.17-6.15%. Therefore, the detection of acrylamide based on the amidase hydrolysis is suitable for screening this carcinogen compound

A simple potentiometric biosensor based on carboxylesterase for the analysis of aspartame

A potentiometric aspartame biosensor was fabricated by simply depositing the carboxylesterase (CES)-bonded poly(n-butyl acrylate-n-acryloxysuccimide) [CES-poly(nBA-NAS)] microspheres on a Ag/AgCl screen-printed pH selective electrode. The pH transducer was made from non-plasticized polyacrylate membrane containing a hydrogen ionophore and lipophilic salt. The immobilized CES enzyme catalyzed the enzymatic hydrolysis of aspartame to L-aspartic acid (L-Asp), L-phenylalanine and methanol. Potentiometric determination of aspartame concentration was performed by quantifying the hydrogen ion concentration produced from L-Asp. The potentiometric determination of aspartame exhibited good selectivity with near Nernstian response. The sensitivity of the biosensor was closed to the Nernstian value, i.e., 50-52 mV decade-1 with a dynamic linear response range from 10-5 to 10-2 M and detection limit approaching 10-6 M. The aspartame biosensor demonstrated good repeatability and reproducibility with relative standard deviation (RSD) of 1.9% and 1.6%, respectively (n=3). The potentiometric aspartame biosensor was demonstrated to be reliable for determining aspartame content in sweetener samples and was comparable to the conventional high-performance liquid chromatography (HPLC) method for aspartame analysis