Hellma Cells

Hellma Cells http //hellma-worldwide.com/tochter/Tochter2.htm to get the website for your area. For UK use http //www.hellma.demon.co.uk/... 

A 1 -cm path length quartz cuvette is most often used to make absorbance measurements. However, quartz cuvettes with shorter path lengths, 0.01 to 0.5 cm, are available (e.g., from Hellma Cells or Beckman) these shorter path length cuvettes allow higher concentrations of protein solutions to be measured. Equation B1.3.1 and Equation B 1.3.2 assume the cuvette has a path length of 1 cm when cuvettes of shorter path length are used, the correct value for b must be substituted in the equation. 

A cross-sectional view of one cell assembly of the differential photoacoustic apparatus is shown in Fig. 9. Optical access to the sample solution contained in a 1-cm cuvette (an all-quartz modification of a cuvette from Hellma Cell Inc. No. 221, which reduces the probability of cell fracture) is provided by 6.4 mm apertures in a thermostated aluminium housing. Temperature control is provided by four cartridge heaters (Hot Watt, 100 W/120 V) mounted at the four corners of the aluminium block and connected in series to a 10 A/120 V triac (LOVE Controls Corp). The power output of the triac is controlled by a proportional, integral,... 

UV spectra were recorded on an IBM 9430 UV-VIS Spectrometer and aqueous samples were contained in 0.5 cm path length Ouartz Suprasil cells (Hellma Cells). 

The nematogen used in the experiments was 5CB containing a small quantity of L-dye D81 (EM Chemicals). The glass sample cell spacing was 10 or 100 jum, (Hellma Cells). Uniform parallel alignment of the nematic was achieved by the rubbed PVA process. The glass sample cell was inserted into a temperature controlled aluminum block. 

The formaldoxime, masking and neutralisation streams are added to each other at point A (Fig. 7.1) and mixed by passage through coil M. At point B, the reagents meet the sample zone, which had previously received a reduction stream of ascorbic acid at point C. The formation of the coloured complex takes place in the reduction coil (R) and the absorbance is measured at 455 nm in a Beckman Model 25 spectrophotometer connected to a Beckman Model 24-25 ACC recorder and equipped with a Hellma Type 178 flow cell, light path 10 mm, volume 0.08 ml. 

The contrast factors have been measured interferometrically [87] and with an Abbe refractometer, respectively. The sample is contained in a fused silica spectroscopic cell with 200 pm thickness (Hellma). The sample holder is thermostated with a circulating water thermostat and the temperature is measured close to the sample with a PtlOO resistor. The amplitude of the temperature modulation of the grating is well below 100 pK and the overall temperature increase within the sample is limited to approximately 70 mK in a typical experiment [91], which is sufficiently small to allow for measurements close to the critical point. 

Figure 5.19. Progress in miniaturization of spectrophotometric flowthrough cells, (a) Hellma cuvette, which fits into most commercial photometers, b) Z-cell, where A are the transparent windows B, Teflon made body C, cell house, and CH, the inlet channel, (c) A fiber optic reflectance cell for optosensing at active surfaces [848], where CH is the channel of a microconduit, R is the chemically active reflecting material, OF is the optical fiber.

Figure 5.31 (a) The sample Is pipetted onto the cell window, (b) The cap compresses the sample into a fixed path length. (Graphic courtesy of Hellma Analytics, Mullhelm, Germany, www.hellmausa.com.)... 

Details of the PLP experiments on aqueous solutions of non-ionized MAA are reported in ref. The polymerizations were carried out in a in a QS 110 cell (Hellma-Worldwide) of 10 mm path length. The reaction solutions were purged with nitrogen for 4 min and thermostated for 20 min prior to PLP. For each mixture, at least two PLP experiments were performed. To reach monomer conversions up to 5%, between 25 and 300 pulses were applied. Monomer conversion was determined by weighing the polymer after freeze-drying. The polymer molecular weight distribution was determined via aqueous-phase using two injections for each sample. 

Samples are put into 1 cm path length glass cells (Hellma). 

Hellma, web page. Product cells for flow through measurements, http //www.hellma-analytics.com/text/191/en/flow-through-cell.html. 

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