The determination of C, H and N in solid/liquid samples is performed using an automatic PE 2400 Series II CHNS/O Analyser. The sample weighed in a tin capsule is combusted in oxygen atmosphere. Final combustion products include N2, CO2 and H2O. Elements such as halogens and sulphur are removed by scrubbing reagents in the combustion zone. The resulting gases are separated by a frontal chromatography and detected by a thermal conductivity detector. The whole procedure excludes determination of the ash.
Method principle: A solid, liquid or powder sample is excited in a sample compartment of the analyzer with X-rays emitted from an X-ray tube. During the relaxation, the atoms emit secondary X-rays. The radiation frequencies are characteristic for each element. The intensity of a particular line corresponds to the content of the element in the sample. SPECTRO XEPOS P instrument uses adapted primary radiation for increased sensitivity if specific groups of elements are determined. The analysis is non-destructive, thus the sample can be used further after the analysis.
The method allows rapid screening of the present elements, whether they are desirable or not in the sample, e.g. residual halogenated reagents, heavy metals from the catalysts used in the synthesis (Pd, Pt, Ni…) etc. Detection limits are most often in the range from 0.1 to 10 mg/kg. Quantitative determination of P, S, Cl, Br and I or other elements is most often done after dissolving a precisely weighed sample amount in methanol as a well-defined matrix against external calibration. Water or other solvents that do not contain interfering elements can be used, too.
Optical emission spectrometry with inductively coupled plasma (ICP-OES)
Method principle: The sample is transformed into a solution (dissolved or burned in O2 atmosphere and then dissolved). The solution is nebulized and aerosol is carried to high-temperature plasma by a stream of argon. In the plasma, compounds are atomized and atoms are excited to higher energy states. During following relaxation, the atoms emit characteristic radiation in visible and ultraviolet region. Radiation´s wavelength is characteristic for each element and its intensity is related to the element´s concentration in the sample. The method can determine most chemical elements. Limits of detection vary among different matrices and elements, in general they are between 0.01 and 10 µg/L (in analyzed solution). In comparison with “classic” titrimetric methods, ICP-OES offers faster analysis, lower limits of detection, lower sample consumption, simultaneous determination of multiple elements and lower risk of interferences.
Optical emission spectrometry with inductively coupled plasma and electrothermal vaporization (ETV-ICP-OES)
Method principle: Electrothermal vaporization represents an alternative way of sample introduction to ICP-OES. The sample is weighted into graphite boats and inserted into a graphite furnace. In the furnace, sample is heated according to chosen temperature program up to a maximum of 3000 °C. During this heating sample decomposes and analytes evaporate. A small amount of CCl2F2 (freon R12) is added to the furnace during heating to transform elements into their more volatile compounds. A stream of argon flows through the furnace, carrying vapors and dry aerosol to high-temperature plasma.
Unlike in the common ICP-OES, when ETV is used, element´s signal is not constant during the analysis (compounds evaporate at different temperatures and therefore at different moments) and therefore transient signal needs to be recorded. Electrothermal vaporization improves limits of detection of ICP-OES (up to units of µg/kg in the material itself), lowers sample consumption and enables analysis without sample preparation. Another advantage is removal of interferences by optimization of temperature program so that interfering elements evaporate at different moments.
Measurement of optical rotation
By default, measurements are made in cell A (1.5 mL) at a wavelength of 589 nm, alternatively it can be measured at wavelengths of 365, 405, 436, 546 and 633 nm.
- measurement in transmission mode in solution and in KBr pellets
- measurement using micro techniques (< 1 mg of sample)
- measurement in aqueous solution (transmission in D2O and H2O, ATR; peptides and proteins)
- GC-IR analysis
- spectra interpretation
- Raman spectroscopy and Raman optical activity
Circular dichroism (CD)
- ECD and absorption spectra in solutions
- temperature dependences in the interval of 5-85 °C
- kinetics measurements
- folding study (peptides, proteins and nucleic acids
- magnetic circular dichroism