A simple and reliable new microchip electrophoresis method for fast measurements of imidazole dipeptides in meat from different animal species.

Microchip electrophoresis (ME) was applied for the separation of two physiologically important imidazole dipeptides-carnosine and anserine. The capacitively coupled contactless conductivity detector (C4D) was employed for quantification of both dipeptides after separation in a new home-built ME unit. The separation parameters were optimized as follows to enable quantitative, baseline separation of both dipeptides: injection time 16 s, injection voltage 900 V/cm, and separation voltage 377.1 V/cm. The C4D detector responded linearly to both imidazole dipeptides in the range 0-20 mg L-1. The known addition methodology was applied to test the accuracy of the measurement of imidazole dipeptides in a complex sample. The recoveries for measurement of carnosine in the mixture ranged from 96.1 to 105.0%, whereas those for anserine amounted to 96.6 to 102.0%. This method was also applied to real biological samples. The results exhibited a satisfactory agreement with a standard HPLC method. The proposed ME method represents a cheap, fast, and simple alternative to the existing, more complicated and expensive HPLC methods. This method does not demand either the optical detectors nor tedious derivatization of sample, which are unavoidable in HPLC methods. The method was succesfuly applied for animal species determination in unknown meat samples using the carnosine/anserine ratio, and subsequently, it could be used in a food fraud prevention process. Graphical abstract Microchip electrophoresis portable device with a C4D detector for determination of imidazole dipeptides in model samples and real meat samples from different animal species.

Effect of Amino Acids on Growth Performance, Carcass Characteristics, Meat Quality, and Carnosine Concentration in Broiler Chickens.

The aim of this research was to investigate the deposition of carnosine in broiler muscles by feeding treatments comprising ß-alanine, L-histidine, and magnesium oxide in various concentrations. The research was carried out on 120 Cobb 500 broilers divided into four groups. From weeks four to six, broilers were fed finisher mixtures as follows: P1, control group; P2, 0.5% ß-alanine + 0.24% MgO; P3, 0.25% L-histidine + 0.24% MgO; and P4, 0.20% ß-alanine + 0.10% L-histidine + 0.24% MgO. This paper presents the weights of broilers and their carcasses, portions of main parts of carcasses, technological quality of breast muscles, and concentrations of carnosine in breast and thigh muscles. The following traits of muscle tissue quality were measured: initial and final pH value (45 min after slaughtering pH1, and 24 h after cooling pH2), drip loss, color (Minolta colorimeter, expressed as CIE L*, CIE a*, and CIE b* values), meat softness, and cooking loss. Data on relative concentration of protein carbonyl (nmol/mg protein) in the muscles of breasts and thighs and levels of thiobarbituric acid-reactive substances (TBARS) in fresh and frozen breasts muscles (nmol/mg of tissue) are presented. Statistical analysis proved that feeding treatments had an effect on the live weight of broilers in the 4th, 5th, and 6th weeks of fattening (P<0.05), as well as on the carcass quality at slaughter (P<0.05; except the portion of wings), pH1 value (P=0.035), CIE a* indicator (P=0.007), drip loss (P=0.002), and meat texture (P=0.008). Compared to the control group, synthesis and deposition of carnosine were increased in breast muscles in groups P2, P3, and P4 by 7.51%, 10.62%, and 62.93%, respectively, and in thigh muscles by 61.05%, 78.95%, and 89.52%, respectively. It was also confirmed that feeding treatments influenced the level of TBARS in frozen broiler breast muscles (P=0.014).

A novel, fast responding, low noise potentiometric sensor containing a carbon-based polymeric membrane for measuring surfactants in industrial and environmental applications.

A new high-sensitivity potentiometric sensor for anionic surfactants was fabricated using the dimethyldioctadecylammonium-tetraphenylborate (DDA-TPB) ion associate as an ionophore that was incorporated into a liquid PVC membrane. Carbon powder was used for immobilization of the ionophore in the membrane, thus significantly reducing its ohmic resistance and reducing its signal drift. The sensor exhibits a sub-Nernstian response for both dodecylbenzenesulfonate (DBS) and dodecyl sulfate (DS) in H2O (55.3 and 58.5mV/decade of activity, respectively) in a range between 3.2×10-7 and 4.6×10-3M for DS and 2.5×10-7 and 1.2×10-3M for DBS. The sensor also exhibited a sub-Nernstian response for DS and DBS in 10mM Na2SO4 (55.4 and 57.7mV/decade of activity, respectively) between 2.5×10-7 and 4.6×10-3M for DS and 1.5×10-7 and 8.8×10-4M for DBS. The detection limits for DS and DBS in H2O were 2.5×10-7 and 2.0×10-7 M and in 10mM Na2SO4 the detection limits were 2.5×10-7 and 1.2×10-7 M, respectively. The response time of the sensor was less than 5s for changes at higher concentration levels (above 1×10-4M) in both water and 10mM Na2SO4. At lower concentrations (below 1×10-5M) the response times were 8 and 6s in water and 10mM Na2SO4, respectively. The signal drift of the sensor was 1.2mV/hour. The new carbon-based sensor exhibited excellent selectivity performance for DS over almost all of the anions commonly present in commercial formulations and it was successfully employed as an end-point detector in potentiometric titrations of anionic surfactants in a pH range from 3 to 12. Three-component mixtures containing sodium alkanesulfonate (C10, C12 and C14) were successfully differentially titrated.

Determination of anti-oxidative histidine dipeptides in poultry by microchip capillary electrophoresis with contactless conductivity detection.

A home-made microchip electrophoresis (MCE) device was used to quantitate two biologically important histidine dipeptides, carnosine and anserine, using capacitively coupled contactless conductivity detection (C4D), at pH 2.7. The C4D detector exhibited a linear response to both carnosine and anserine in the range of 0-200µM for the individual dipeptides and in the range of 0-100µM for each dipeptide when both were present as a mixture. The limit of detections (LOD) for the dipeptides in the mixture were 0.10µM for carnosine and 0.16µM for anserine. Standard addition was used to detemine the accuracy of the method. For carnosine and anserine the recoveries were in the range of 96.7±4.9-106.0±7.5% and 95.3±4.5-105.0±5.1% in thigh muscle and 97.5±5.1-105.0±7.5% and 95.3±5.4-97.3±5.6% in breast muscle, respectively.

Direct potentiometric determination of starch using a platinum redox sensor.

Here, we describe the development of a platinum redox sensor for the direct potentiometric quantification of starch in solution. The sensor measures the decrease in free triiodide ion after it complexes with starch to form a starch-triiodide complex. This decrease was, therefore, correlated with starch concentration, and the composition and stability of the potassium triiodide solution were optimised. The starch-triiodide complex was characterized potentiometrically at variable starch and triiodide concentrations. We also propose a response mechanism for the platinum redox sensor towards starch and an appropriate theoretical model. The optimised method exhibited satisfactory accuracy and precision and was in good agreement with a standard spectrophotometric method. The sensor was tested over a range of 0.4-9 mg starch, with recoveries ranging from 97.8% to 103.4% and a detection limit of 0.01 mg starch.

Direct potentiometric determination of diastase activity in honey.

A novel method for the determination of diastase activity is reported. The method is based on a direct potentiometric measurement of triiodide ion that is released when a starch-triiodide complex is hydrolysed by honey diastase. The increase of free triiodide ion concentration in a sample is found to be directly proportional to the diastase activity of the sample. A response mechanism of the platinum redox electrode is proposed, allowing a calculation of the diastase activity factor (F). The sensor and analyte parameters, including F, were obtained by least squares fitting of potentiometric data using the optimisation function of the Solver add-in of Microsoft Excel. The values of F obtained by the new direct potentiometric method were compared with those obtained using the standard Phadebas method (DN values), and the two values were found to agree within experimental error. Finally, the diastase activity of nine varieties of honey was determined using the novel method developed here.

A rapid method for the determination of honey diastase activity.

A new rapid method for the determination of honey diastase activity using direct potentiometric principles has been proposed. A platinum redox sensor has been used to quantify the amount of free triiodide released from a starch triiodide complex after starch hydrolysis by honey diastase. The method was tested on honey samples with varying diastase activities. The first 5 min of data for each sample were used for linear regression analysis in order to calculate diastase activity. The new method was compared with classical Schade and commercial Phadebas procedures. The results showed good correlations with both methods and offered a simple method for unit conversion to DN units for diastase activity, making the method suitable for routine analysis.

A new potentiometric sensor for the determination of α-amylase activity.

A platinum redox sensor for the direct potentiometric determination of α-amylase concentration has been described. The sensor measured the amount of triiodide released from a starch-triiodide complex, which was correlated with the α-amylase activity after biocatalytic starch degradation. The composition and stability of the potassium triiodide solution was optimized. The starch-triiodide complex was characterized potentiometrically at variable starch and triiodide concentrations. The response mechanism of the platinum redox sensor towards α-amylase was proposed and the appropriate theoretical model was elaborated. The results obtained using the redox sensor exhibited satisfactory accuracy and precision and good agreement with a standard spectrophotometric method and high-sensitive fully automated descret analyser method. The sensor was tested on pure α-amylase (EC 3.2.1.1, Fluka, Switzerland), industrial granulated α-amylase Duramyl 120 T and an industrial cogranulate of protease and α-amylase Everlase/Duramyl 8.0 T/60 T. The detection limit was found to be 1.944 mU for α-amylase in the range of 0-0.54 U (0-15 µg), 0.030 mKNU for Duramyl 120 T in the range of 0-9.6 mKNU (0-80 µg) and 0.032 mKNU for Everlase/Duramyl 8.0 T/60 T in the range of 0-9.24 mKNU (0-140 µg).

Simultaneous potentiometric determination of cationic and ethoxylated nonionic surfactants in liquid cleaners and disinfectants.

A sensitive potentiometric surfactant sensor based on a highly lipophilic 1,3-didecyl-2-methyl-imidazolium cation and a tetraphenylborate (TPB) antagonist ion was used as the end-point detector in ion-pair potentiometric surfactant titrations using sodium TPB as a titrant. Several analytical and technical grade cationic and ethoxylated nonionic surfactants (EONS) and mixtures of both were potentiometrically titrated. The sensor showed satisfactory analytical performances within a pH range of 3-10 and exhibited satisfactory selectivity for all CS and EONS investigated. Ionic strength did not influence the titration except at 0.1M NaCl, in which a slight distortion of the second inflexion corresponded with the nonionic surfactant. Two-component combinations of four CS and three EONS were potentiometrically titrated using the sensor previously mentioned as the end-point detector. The quantities of the surfactants varied between 2 and 6 µmol for CS and 2.50 and 7.50 µmol for EONS. The known addition methodology was used for determination of the surfactant with considerably lower concentration in the mixture. Three commercial products containing cationic surfactants as disinfectants and nonionic surfactants were potentiometrically titrated, and the results for both type of surfactants were compared with those obtained with standard conventional methods.

Determination of cationic surfactants in pharmaceutical disinfectants using a new sensitive potentiometric sensor.

A new sensitive potentiometric surfactant sensor was prepared based on a highly lipophilic 1,3-didecyl-2-methyl-imidazolium cation and a tetraphenylborate antagonist ion. This sensor was used as a sensing material and incorporated into the plasticized PVC-membrane. The sensor responded fast and showed a Nernstian response for investigated surfactant cations: cetylpyridinium chloride (CPC), hexadecyltrimethylammonium bromide (CTAB) and Hyamine with slope 59.8, 58.6 and 56.8 mV/decade, respectively. The sensor served as an end-point detector in ion-pair surfactant potentiometric titrations using sodium tetraphenylborate as titrant. Several technical grade cationic surfactants and a few commercial disinfectant products were also titrated, and the results were compared with those obtained from a two-phase standard titration method. The sensor showed satisfactory analytical performances within a pH range of 2-11, and exhibited excellent selectivity performance for CPC compared to all of the organic and inorganic cations investigated. The influence of the nonionic surfactants on the shape of titration curves was negligible if the mass ratio of ethoxylated nonionic surfactants and cationic surfactants (EONS:CS) was not greater than 5.

Nonionic surfactant-selective electrode and its application for determination in real solutions.

A liquid membrane nonionic surfactant sensitive electrode has been prepared, based on a new barium pseudocationic complex of a highly ethoxylated fatty alcohol polyglycol ether and tetraphenylborate as sensing material. The complex has been incorporated into the plasticized PVC-membrane and used as sensing material. The electrode exhibited positive linear non-Nernstian response toward different nonionic surfactants and sub-Nernstian response toward tetraphenylborate with the lower detection limit of 3.3 x 10(-7) mol dm(-3) in barium chloride solution. The interfering effect of some alkaline, alkaline earth, and heavy metal cations, has been demonstrated by displaying their calibration curves compared with that of Triton X-100. The electrode has been used as an end-point indicator for potentiometric titration of analytical and technical grade polyethoxylated nonionic surfactants, modelled detergent products, and commercial detergents.