Voltammetric sensor based on the copper (II) amino acid complex for the determination of tryptophan enantiomers

A voltammetric sensor based on a composite of polyarylene phthalide and graphitized carbon black Carboblack C modified with chelate complexes of L-argenato-L-alaninate of copper (II) has been developed for the recognition and selective determination of tryptophan enantiomers. The conditions for modifying the sensor are optimized, the effective surface area (A = 4.38 ± 0.06 mm2) and the effective resistance (Ret = 1.29 ± 0.08 kΩ) are calculated. The optimal conditions for recording voltammograms of tryptophan enantiomers are selected: the range of operating potentials is 0.5-1.2 V, the potential sweep rate is 20 mV/s, the holding time of the electrode in the test solution is 5 s. The electrochemical and analytical characteristics of the sensor were studied when registering differential pulse voltammograms of tryptophan enantiomers. It is shown that the dependence of the analytical signal on the concentration is linear in the range from 1.25·10-6 to 1·10-3 M with detection limits of 0.90·10-6 M for L-Trp and 0.66·10-6 M for D-Trp. The developed sensor shows the greatest sensitivity to D-Trp. The sensor has been successfully tested to determine the content of L- and D-Trp in enantiomer solutions in the presence of excipients that are part of medicines and biologically active additives. The proposed sensor allows the determination of tryptophan enantiomers in human urine and blood plasma. To evaluate the analytical capabilities of the sensor, the "entered-found" method was used. When determining tryptophan enantiomers in model solutions, the relative standard deviation does not exceed 2.3 %, and the relative error is 1.7 %. When determining D- and L-Trp in biological fluids, the relative standard deviation ranges from 0.3-1.7 %, and the relative error ranges from 0.3-5.6 %. The research results show that there is no significant systematic error.

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Voltammetric Determination of Metals in Copper Alloys at Trace and Ultratrace Concentrations

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20031437 ◽

2003 ◽

Vol 68 (8) ◽

pp. 1437-1448 ◽

Cited By ~ 4

Author(s):

Clinio Locatelli ◽

Giancarlo Torsi

Keyword(s):

Standard Deviation ◽

Relative Standard Deviation ◽

Relative Error ◽

Analytical Procedure ◽

Copper Alloys ◽

Voltammetric Determination ◽

Standard Reference Materials ◽

Relative Standard ◽

Precision And Accuracy

The present work describes the analytical procedures for the voltammetric determination of Cu, Pb, Cd, Zn, Fe, Mn, Co, Ni, Sn, Sb and Bi in copper alloys. The possibility of determining simultaneously metal concentrations in the case of interference of the voltammetric signals due to the peak overlapping is also highlighted and discussed. The analytical procedure was verified by the analysis of the standard reference materials: commercial bronze A NIST-SRM 1115, gunmetal BCS-CRM 207/2, high tensile brass BCS-CRM 390. Precision and accuracy, expressed as relative standard deviation and relative error, respectively, were in all cases lower than 6%. The limits of detection for each element were also reported.

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An Automated Procedure for the Determination of Ammonia in Tobacco

Beiträge zur Tabakforschung International/Contributions to Tobacco Research ◽

10.2478/cttr-2013-0287 ◽

1972 ◽

Vol 6 (4) ◽

Cited By ~ 1

Author(s):

P.F. Collins ◽

W.W. Lawrence ◽

J.F. Williams

Keyword(s):

Standard Deviation ◽

Relative Standard Deviation ◽

Distillation Method ◽

Relative Standard ◽

Tobacco Sample ◽

Automated Determination

AbstractA procedure for the automated determination of ammonia in tobacco has been developed. Ammonia is extracted from the ground tobacco sample with water and is determined with a Technicon Auto Analyser system which employs separation of the ammonia through volatilization followed by colourimetry using the phenate-hypochlorite reaction. The procedure has been applied to a variety of tobaccos containing from 0.02 to 0.5 % ammonia with an overall relative standard deviation of 2 %. The accuracy of the procedure as judged by recovery tests and by comparison to a manual distillation method is considered adequate

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Indirect and Direct Determination of the Casein Content of Milk by Kjeldahl Nitrogen Analysis: Collaborative Study

Journal of AOAC International ◽

10.1093/jaoac/81.4.763 ◽

1998 ◽

Vol 81 (4) ◽

pp. 763-774 ◽

Cited By ~ 58

Author(s):

Joanna M Lynch ◽

David M Barbano ◽

J Richard Fleming

Keyword(s):

Standard Deviation ◽

Nitrogen Content ◽

Relative Standard Deviation ◽

Collaborative Study ◽

Direct Determination ◽

Raw Milk ◽

Method Performance ◽

Relative Standard ◽

Milk Casein

Abstract The classic method for determination of milk casein is based on precipitation of casein at pH 4.6. Precipitated milk casein is removed by filtration and the nitrogen content of either the precipitate (direct casein method) or filtrate (noncasein nitrogen; NCN) is determined by Kjeldahl analysis. For the indirect casein method, milk total nitrogen (TN; Method 991.20) is also determined and casein is calculated as TN minus NCN. Ten laboratories tested 9 pairs of blind duplicate raw milk materials with a casein range of 2.42- 3.05℅ by both the direct and indirect casein methods. Statistical performance expressed in protein equivalents (nitrogen ⨯ 6.38) with invalid and outlier data removed was as follows: NCN method (wt%), mean = 0.762, sr = 0.010, SR = 0.016, repeatability relative standard deviation (RSDr) = 1.287℅, reproducibility relative standard deviation (RSDR) = 2.146%; indirect casein method (wt℅), mean = 2.585, repeatability = 0.015, reproducibility = 0.022, RSDr = 0.560℅, RSDR = 0.841; direct casein method (wt℅), mean = 2.575, sr = 0.015, sR = 0.025, RSDr = 0.597℅, RSDR = 0.988℅. Method performance was acceptable and comparable to similar Kjeldahl methods for determining nitrogen content of milk (Methods 991.20, 991.21,991.22, 991.23). The direct casein, indirect casein, and noncasein nitrogen methods have been adopted by AOAC INTERNATIONAL.

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Determination of Nitrate in Water by HPLC

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.448-453.406 ◽

2013 ◽

Vol 448-453 ◽

pp. 406-408

Author(s):

Jing Liu ◽

Xiao Na Ji ◽

Qing Kai Ren ◽

Sheng Shu Ai ◽

Li Jun Wan ◽

...

Keyword(s):

High Performance Liquid Chromatography ◽

Liquid Chromatography ◽

Standard Deviation ◽

Relative Standard Deviation ◽

Recovery Rate ◽

High Performance ◽

Separation Efficiency ◽

Fast Analysis ◽

Relative Standard

We established a method fordetermination of nitrate in water by High Performance Liquid Chromatography(HPLC). The sample was analysed by HPLC-ADA and was quantitated by externalstandard method after being simply processed. This methd has the advantages ofhigh separation efficiency and fast analysis. The experiment result showed thatthe linearly dependent coefficient was0.994, the recovery rate was between 98.7%～105.7%,the relative standard deviation（RSD）wasless than 2.1 %, and the lowest detectable limit is 0.01ng (S/N=1.6).

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Determination of 1,3-Dichloropropanol in Soy Sauce and Related Products by Headspace Gas Chromatography with Mass Spectrometric Detection: Interlaboratory Study

Journal of AOAC International ◽

10.1093/jaoac/88.5.1404 ◽

2005 ◽

Vol 88 (5) ◽

pp. 1404-1412 ◽

Cited By ~ 4

Author(s):

Sarah Hasnip ◽

Colin Crews ◽

Nicholas Potter ◽

Paul Brereton ◽

Henri Diserens ◽

...

Keyword(s):

Gas Chromatography ◽

Standard Deviation ◽

Relative Standard Deviation ◽

Internal Standard ◽

Mass Spectrometric ◽

Soy Sauce ◽

Headspace Gas Chromatography ◽

Relative Standard ◽

Headspace Gas

Abstract An interlaboratory study was performed to evaluate the effectiveness of a headspace gas chromatography (GC) method for the determination of 1,3-dichloro-propan-2-ol (1,3-DCP) in soy sauce and related products at levels above 5 ng/g. The test portion is mixed with an internal standard (d5-1,3-DCP) and ammonium sulfate in a sealed headspace vial. After achieving equilibrium, the headspace is sampled either by gas-tight syringe or solid-phase microextraction (SPME) and analyzed by GC with mass spectrometric detection. 1,3-DCP is detected in the selected-ion mode (monitoring m/z 79 and 81 for 1,3-DCP and m/z 82 for the deuterated internal standard) and quantified by measurement against standards. Test materials comprising soy, dark soy, mushroom soy, and teriyaki sauces, both spiked and naturally contaminated, were sent to 9 laboratories in Europe, Japan, and the United States; of these, 5 used SPME and 4 used syringe headspace analysis. Test portions were spiked at 5.0, 10.0, 20.0, 100.0, and 500.0 ng/g. The average recovery for spiked blank samples was 108% (ranging from 96–130%). Based on results for spiked samples (blind pairs at 5, 10, 20, 100, and 500 ng/g) as well as a naturally contaminated sample (split-level pair at 27 and 29 ng/g), the relative standard deviation for repeatability (RSDr) ranged from 2.9–23.2%. The relative standard deviation for reproducibility (RSDR) ranged from 20.9–35.3%, and HorRat values of between 1.0 and 1.6 were obtained.

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Development and validation of spectrophotometric method for phenylephrine hydrochloride estimation in nasal drops formulations

Macedonian Journal of Chemistry and Chemical Engineering ◽

10.20450/mjcce.2008.235 ◽

2008 ◽

Vol 27 (2) ◽

pp. 149 ◽

Cited By ~ 3

Author(s):

Ivana Savić ◽

Goran Nikolić ◽

Vladimir Banković

Keyword(s):

Standard Deviation ◽

Sodium Hydroxide ◽

Relative Standard Deviation ◽

Spectrophotometric Method ◽

Molar Absorptivity ◽

Dosage Forms ◽

Phenylephrine Hydrochloride ◽

Relative Standard ◽

Development And Validation

Simple, accurate and reproducible UV-spectrophotometric method was developed and validated for the estimation of phenylephrine hydrochloride in pharmaceutical nasal drops formulations. Phenylephrine hydrochloride was estimated at 291 nm in 1 mol⋅dm-3 sodium hydroxide (pH 13.5). Beer’s law was obeyed in the concentration range of 10–100 μg⋅cm−3 (r2 = 0.9990) in the sodium hydroxide medium. The apparent molar absorptivity was found to be 1.63×103 dm3⋅mol−1⋅cm−1. The method was tested and validated for various parameters according to the ICH (International Conference on Harmonization) guidelines. The detection and quantitation limits were found to be 0.892 and 2.969 μg⋅cm−3, respectively. The proposed method was successfully applied for the determination of phenylephrine hydrochloride in pharmaceutical nasal drops formulations. The results demonstrated that the procedure is accurate, precise and reproducible (relative standard deviation < 1 %), while being simple, cheap and less time consuming, and hence can be suitably applied for the estimation of phenylephrine hydrochloride in different dosage forms.

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Badanie stabilności barwnych znaczników fluorescencyjnych w silnie zasiarczonych wodach złożowych

Nafta-Gaz ◽

10.18668/ng.2021.02.03 ◽

2021 ◽

Vol 77 (2) ◽

pp. 82-91

Author(s):

Katarzyna Wojtowicz ◽

Keyword(s):

Standard Deviation ◽

Relative Standard Deviation ◽

Rhodamine B ◽

Water Reservoir ◽

Distilled Water ◽

Test Results ◽

Fluorescent Tracers ◽

Reservoir Water ◽

Relative Standard

The article presents the issues related to the determination of colored fluorescent tracers such as fluorescein, eosin yellowish, rhodamine B and uranine in reservoir waters by spectrophotometric method. For this purpose, the influence of the pH of the solution on the absorption spectra of the tested tracers was checked. Test results show that fluorescein, rhodamine B and uranine are sensitive to changes in the buffer pH, therefore it is advisable to use stable tracer solutions as well as to control and possibly correct pH in further tests. As part of the study, calibration curves of fluorescein, eosin yellowish, rhodamine B and uranine in distilled water, reservoir water A4 and highly sulfated reservoir waters A5 and A6 were plotted and the analytical methods were validated. Analytical validation included determination of linearity, standard deviation and relative standard deviation of the tested tracers solutions. High values of the regression parameters (0.9927–0.9998) of the analyzed tracers prove a good linear fit, while low values of standard deviation and relative standard deviation prove its repeatability and precision. Particular attention was paid to testing the stability of colored fluorescent tracers in highly sulfated reservoir waters. For this purpose, solutions of the tested tracers were prepared at concentrations of 10 mg/dm3 in distilled water, A4 reservoir water and highly sulfated A5 and A6 reservoir waters. Measurements of the tested tracers in the prepared solutions were performed every 2 days over the period of 1 month. The test results show that fluorescein, eosin yellowish, rhodamine B and uranine solutions are stable in the distilled water and A4 reservoir water, while they degrade in the A5 and A6 reservoir waters. Fluorescein and uranine turned out to be the most sensitive, as they degraded completely in the A6 reservoir water after 20 (fluorescein) and 22 (uranine) days. Yellowish eosin and rhodamine B turned out to be slightly more stable in highly sulfated reservoir waters, as they degraded completely in the A6 reservoir water after 24 days.

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Interlaboratory Evaluation of Two Enzyme-Linked Immunosorbent Assay Kits for the Determination of Crustacean Protein in Processed Foods

Journal of AOAC International ◽

10.1093/jaoac/91.1.123 ◽

2008 ◽

Vol 91 (1) ◽

pp. 123-129 ◽

Cited By ~ 26

Author(s):

Shinobu Sakai ◽

Rieko Matsuda ◽

Reiko Adachi ◽

Hiroshi Akiyama ◽

Tamio Maitani ◽

...

Keyword(s):

Standard Deviation ◽

Relative Standard Deviation ◽

Immunosorbent Assay ◽

Soluble Protein ◽

Enzyme Linked Immunosorbent Assay ◽

Processed Foods ◽

Relative Standard ◽

High Level

Abstract The labeling of foods containing material derived from crustaceans such as shrimp and crab is to become mandatory in Japan because of increases in the number of allergy patients. To ensure proper labeling, 2 novel sandwich enzyme-linked immunosorbent assay (ELISA) kits for the determination of crustacean protein in processed foods, the N kit (Nissui Pharmaceutical Co., Ltd, Ibaraki, Japan) and the M kit (Maruha Nichiro Holdings, Inc., Ibaraki, Japan), have been developed. Five types of model processed foods containing 10 and/or 11.9 g/g crustacean soluble protein were prepared for interlaboratory evaluation of the performance of these kits. The N kit displayed a relatively high level of reproducibility relative standard deviation (interlaboratory precision; 4.08.4 RSDR) and sufficient recovery (6586) for all the model processed foods. The M kit displayed sufficient reproducibility (17.620.5 RSDR) and a reasonably high level of recovery (82103). The repeatability relative standard deviation (RSDr) values regarding the detection of crustacean proteins in the 5 model foods were mostly <5.1 RSDr for the N kit and 9.9 RSDr for the M kit. In conclusion, the results of this interlaboratory evaluation suggest that both these ELISA kits would be very useful for detecting crustacean protein in processed foods.

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Liquid Chromatographic Determination of Ampicillin Residues in Porcine Muscle Tissue by a Multipenicillin Analytical Method: European Collaborative Study

Journal of AOAC International ◽

10.1093/jaoac/85.4.889 ◽

2002 ◽

Vol 85 (4) ◽

pp. 889-900 ◽

Cited By ~ 1

Author(s):

Eric Verdon ◽

Pierric Couëdor ◽

Pierre Maris ◽

Michel Laurentie ◽

P Batjoens ◽

...

Keyword(s):

Mass Spectrometry ◽

Standard Deviation ◽

Relative Standard Deviation ◽

Muscle Tissue ◽

Phosphate Buffer ◽

Collaborative Study ◽

Porcine Muscle ◽

Relative Standard ◽

Liquid Chromatographic

Abstract A collaborative study involving 14 laboratories was conducted to determine residues of ampicillin in porcine muscle tissue by using a liquid chromatographic method developed for multipenicillin analysis that can quantitate 8 penicillin compounds (benzylpenicillin, phenoxymethylpenicillin, ampicillin, amoxicillin, nafcillin, oxacillin, cloxacillin, and dicloxacillin) at trace levels in muscle tissue. This method involves extraction of the penicillins with phosphate buffer, pH 9, followed cleanup and concentration on a C18 solid-phase extraction column and reaction with benzoic anhydride at 50°C and with 1,2,4-triazole and mercury(II) chloride solution, pH 9.0, at 65°C. The derivatized compounds are eluted isocratically on a C8 column with a mobile phase of acetonitrile and phosphate buffer (pH 6; 0.1M) containing sodium thiosulfate and the ion-pair reagent tetrabutylammonium hydrogen sulfate. The penicillins are detected by UV absorption at 325 nm. The limit of detection and the limit of determination (quantitation) of the method were calculated to be approximately 3–5 and 25 μg/kg, respectively, in accordance with the criteria of European Union (EU) Decision No. 93/256/EEC. In this first interlaboratory study, collaborators were instructed to monitor 4 different penicillin compounds (benzylpenicillin, phenoxymethylpenicillin, ampicillin, and amoxicillin) by analyzing 8 blind samples of muscle tissue in triplicate. These samples were prepared from 2 materials containing different concentrations of incurred ampicillin (63.5 μg/kg for material No. 1 and 358.1 μg/kg for material No. 2) and 1 blank material. The repeatability relative standard deviation and the reproducibility relative standard deviation were 10.2 and 17.4%, respectively, for material No. 1 and 7.0 and 16.0%, respectively, for material No. 2. These results demonstrate that the method is suitable for the determination of ampicillin residues in muscle tissue at the EU maximum residue limit (50 μg/kg) and above. However, the identification of positives by this procedure may need additional confirmation by techniques with greater specificity, such as liquid chromatography combined with mass spectrometry, or tandem mass spectrometry. Investigations regarding the basis of interlaboratory testing studies will further demonstrate the suitability of multiresidue methodology for detecting and quantitating other compounds in the family of penicillin antibiotics.

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Gas-Liquid Chromatography of Trichlorfon in Soluble Powder Formulations

Journal of AOAC INTERNATIONAL ◽

10.1093/jaoac/57.5.1128 ◽

1974 ◽

Vol 57 (5) ◽

pp. 1128-1131

Author(s):

Phil B Bowman ◽

Peter W Dame

Keyword(s):

Liquid Chromatography ◽

Standard Deviation ◽

Relative Standard Deviation ◽

Trimethylsilyl Ether ◽

Gas Liquid Chromatography ◽

Mass Spectral ◽

Powder Formulation ◽

Relative Standard ◽

Quantitative Recovery

Abstract A procedure is described for the determination of trichlorfon in a soluble powder formulation by gas-liquid chromatography. Silylation prevents on-column degradation of trichlorfon to dichlorvos. The procedure provides quantitative recovery from the formulation as demonstrated by a spiking study. A relative standard deviation of less than 2% was obtained for 6 replicate assays of a single lot of formulation. The mass spectral fragmentations of trichlorfon and trichlorfon-trimethylsilyl ether are described.

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