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  • Using ultrapure water in ion chromatography to run analyses at the ng/L level 15250398

    Thanks to enhanced capabilities, ion chromatography (IC) occupies an increasing position in many types of applications. Achieving ideal performances for an extended life-time can only be reached, however, if the IC system is operated in optimum experimental conditions. Among the various parameters that need to be controlled, water is particularly important, because it is used throughout the analysis, from sample preparation to column rinsing, elution, and mobile phase preparation. More and more, devices are included in IC systems to generate the eluent in situ, and ultrapure water becomes the major reagent. Data of pre-concentration of high purity water show that detection limits at the ng/L level can be expected with water purified using the right combination of technologies.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple
    Product Catalog Name:
    Multiple

  • Using ultrapure water in ion chromatography to run analyses at the ng/L level 15250398

    Thanks to enhanced capabilities, ion chromatography (IC) occupies an increasing position in many types of applications. Achieving ideal performances for an extended life-time can only be reached, however, if the IC system is operated in optimum experimental conditions. Among the various parameters that need to be controlled, water is particularly important, because it is used throughout the analysis, from sample preparation to column rinsing, elution, and mobile phase preparation. More and more, devices are included in IC systems to generate the eluent in situ, and ultrapure water becomes the major reagent. Data of pre-concentration of high purity water show that detection limits at the ng/L level can be expected with water purified using the right combination of technologies.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple

  • Urinary metanephrine and normetanephrine determined without extraction by using liquid chromatography and coulometric array detection. 8375055

    We describe a procedure for the direct measurement of metanephrine (MN) and normetanephrine (NMN) in hydrolyzed urine, using HPLC with coulometric array detection. Acid-hydrolyzed samples were diluted and filtered before separation by isocratic reversed-phase ion-pair chromatography. Eight serial coulometric sensors, set at incrementally increasing anodic potentials, were used to screen lower-oxidizing interferences and provide stepwise oxidation of the metanephrines. Voltammetric behavior across three adjacent sensors was used to assess resolution and aid in peak identification. Values obtained in commercial controls were consistently within the specified target range. Variability, expressed as CV, was 5.45-9.22% between runs and 1.60-4.52% within-run for both compounds. The limit of detection was 2.6 micrograms/L for MN and 2.8 micrograms/L for NMN, with a linear response to 15.0 mg/L for both analytes. Results from patients' samples correlated well with those by a method involving dual ion-exchange extraction (r = 0.963, n = 82 for MN; r = 0.9768, n = 83 for NMN). This procedure provided high selectivity and objective peak purity information while greatly simplifying sample preparation.
    Document Type:
    Reference
    Product Catalog Number:
    20-176
    Product Catalog Name:
    100X GTPγS, 10mM

  • Analysis of 8-methoxypsoralen by high-performance liquid chromatography. 2242576

    We report a simple and rapid procedure for assaying 8-methoxypsoralen (8-MOP) in plasma by high-performance liquid chromatography (HPLC). The standard curve for the assay is linear for 8-MOP from 15 to 500 micrograms/L (y = 0.002x-0.01, r = 0.99) with a lower limit of detection of 1.5 micrograms/L. Intra-assay precision (CV) was 6.0% at the 100 micrograms/L concentration and 10.0% at 50 micrograms/L (n = 30 each). Interassay precision was 6.4% at 100 micrograms/L and 7.0% at 50 micrograms/L (n = 50 each). Extraction recovery of 8-MOP was 98%. Common antiarrhythmics, sedatives, and hypnotics were found not to interfere.
    Document Type:
    Reference
    Product Catalog Number:
    20-176
    Product Catalog Name:
    100X GTPγS, 10mM

  • Rapid detection of the addition of soybean proteins to cheese and other dairy products by reversed-phase perfusion chromatography 16546880

    The undeclared addition of soybean proteins to milk products is forbidden and a method is needed for food control and enforcement. This paper reports the development of a chromatographic method for routine analysis enabling the detection of the addition of soybean proteins to dairy products. A perfusion chromatography column and a linear binary gradient of acetonitrile-water-0.1% (v/v) trifluoroacetic acid at a temperature of 60 C were used. A very simple sample treatment consisting of mixing the sample with a suitable solvent (Milli-Q water or bicarbonate buffer (pH¼11)) and centrifuging was used. The method enabled the separation of soybean proteins from milk proteins in less than 4 min (at a flow-rate of 3 ml/min). The method has been successfully applied to the detection of soybean proteins in milk, cheese, yogurt, and enteral formula. The correct quantitation of these vegetable proteins has also been possible in milk adulterated at origin with known sources of soybean proteins. The application of the method to samples adulterated at origin also leads to interesting conclusions as to the effect of the processing conditions used for the preparation of each dairy product on the determination of soybean proteins.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple

  • Sensitive quantitative analysis of C-peptide in human plasma by 2-dimensional liquid chromatography-mass spectrometry isotope-dilution assay. 16556683

    BACKGROUND: Isotope-dilution assays (IDAs) are well established for quantification of metabolites or small drug molecules in biological fluids. Because of their increased specificity, IDAs are an alternative to immunoassays for measuring C-peptide. METHODS: We evaluated a 2-dimensional liquid chromatography-mass spectrometry (2D LC/MS) IDA method. Sample preparation was by off-line solid-phase extraction, and C-peptide separation was performed on an Agilent 1100 2D LC system with a purification method based on high-pressure switching between 2 high-resolution reversed-phase columns. Because of the low fragmentation efficiency of C-peptide, multiple-reaction monitoring analysis was omitted and selective-ion monitoring mode was chosen for quantification. Native and isotope-labeled ([M+18] and [M+30]) C-peptides were monitored in the +3 state at m/z 1007.7, 1013.7, and 1017.7. RESULTS: The assay was linear (r(2) = 0.9995), with a detection limit of 300 amole (1 pg) on column. Inter- and intraday CVs for C-peptide were or =2%. Comparison with an established polyclonal-based RIA showed high correlation (r = 0.964). Plasma concentrations of total C-peptide measured by RIA were consistently higher than by IDA LC/MS, consistent with the higher specificity of IDAs compared with immunoassays. CONCLUSIONS: The 2D LC/MS IDA approach eliminates matrix effects, enhancing assay performance and reliability, and has a detection limit 100-fold lower than any previously reported LC/MS method. Isotope-labeled C-peptide(s) can be clearly differentiated from endogenous C-peptide by the difference in m/z ratio, so that both peptides can be quantified simultaneously. The method is highly precise, robust, and applicable to pharmacokinetic detection of plasma peptides.
    Document Type:
    Reference
    Product Catalog Number:
    HCP-20K
    Product Catalog Name:
    Human C-Peptide RIA

  • Plasma and urinary oxalate and glycolate in healthy subjects. 8419038

    High-performance ion chromatography (HPIC) has been widely used for oxalate analysis and, more recently, for glycolate analysis. We describe a procedure for sample preparation in which the plasma ultrafiltrate is acidified during harvesting with a cation-exchange resin, and the chloride is removed before the ion chromatography, which is performed with a newly developed AS10 column. The same ultrafiltrate sample is analyzed for glycolate. For plasma oxalate, the mean recovery of sample in eluted fractions was 95-96%, and intraassay CV was 6.2-8.1%. The reference interval (mean +/- 2 SD) for men was 0.8-3.2 mumol/L and for women, 1.0-2.6 mumol/L. For urinary oxalate, the reference interval for men was 175-560 mumol/day and for women, 107-432 mumol/day. For plasma glycolate, the mean analytical recovery was 96-98%, and the intra-assay CV was 2.4-6.2%. The reference interval for men was 1.9-7.5 mumol/L and for women, 1.4-7.4 mumol/L. For urinary glycolate, the reference interval for men was 0-1400 mumol/day and for women, 91-1001 mumol/day.
    Document Type:
    Reference
    Product Catalog Number:
    20-176
    Product Catalog Name:
    100X GTPγS, 10mM

  • Impact of purified water quality on molecular biology experiments. 12747591

    Purified water is a reagent used in a variety of molecular biology experiments, for sample and media preparation, in mobile phases of liquid chromatography techniques, and in rinsing steps. The combination of several technologies in water purification systems allows delivering high-purity water adapted to each application and technique. Through a series of examples, the importance of water quality on biotechnology experiments, such as single nucleotide polymorphism (SNP) analysis by denaturating HPLC, RNA preparation and PCR, is presented. Results obtained on DNA mutation and single nucleotide polymorphism analysis using the denaturating HPLC (DHPLC) technique highlight the benefits of organic removal by UV photooxidation process. Comparative gel electrophoresis data show that ultrafiltration is as efficient as diethylpyrocarbonate (DEPC) treatment for suppressing RNase activity in water. Gel electrophoresis and densitometry measurement also point out the benefits of ultrafiltration to carry out reverse transcriptase-polymerase chain reaction quantitatively.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple
    Product Catalog Name:
    Multiple