Description and Discussion
Spectrophotometer calibrations made at full aperture may not be acceptable when the beam is masked by flow cells or microcells, as with HPLC UV detectors. Starna Gold references enable a holistic approach to instrument qualification by allowing measurements using the same flow cell, sipper system or other sampling accessory used in the actual analysis, and over the same wavelength range. The references are supplied in vials with crimp closure and can be transferred to the instrument under test using a syringe without disturbing the cell alignment, often critical in such systems. Each vial contains 4.0 ml of solution.
Four different solution references are available to check wavelength and absorbance accuracy and absorbance linearity in the UV region, or in the UV and visible regions.
The references are:
Wavelength references:
RM-LCUV/RE– Starna Cerium oxide solution (RM-RE) in dilute sulfuric acid
5 characteristic peaks covering the wavelength range from 200 nm to 270 nm.
Approximate peak wavelength values (in nm) are:
201, 211, 223, 240, 254
RM-LCUV/HL – Starna holmium oxide solution (RM-HL) in dilute perchloric acid
14 characteristic and well-defined peaks covering the wavelength range from 240 to 650 nm.
Approximate peak wavelength values (in nm) are:
241, 250, 278, 288, 334, 346, 361, 385, 417, 451, 468, 485, 537, 641
Absorbance reference:
RM-LCUV/NA– Four Starna nicotinic acid solutions: RM-06A, RM-12A, RM-18A, RM-24A (6, 12, 18 & 24 mg/l) in dilute (0.1 M) hydrochloric acid. Supplied with a 0.1 M hydrochloric acid blank (RM-LCUV/00A). Covers the wavelength range 210 nm to 260 nm.
Nicotinic acid has peaks at 213 and 215 nm. Typical absorbance values at these wavelengths for the different concentrations are as follows:
Note: the above three references are all recognised by major pharmacopoeias for instrument qualification.
Wavelength and Absorbance reference:
RM-LCUV/SG – Four Starna Green dye solutions, RM-25G, RM-50G, RM-75G, RM-100G,with nominal concentrations of 25, 50, 75 and 100 respectively. Supplied with a solvent blank (RM-LCUV/00G).
References with sharp absorption bands are unsuitable for qualification of broad bandwidth instrumentation. Starna Green is a specially formulated dye solution with three broad but well-defined peaks that can be certified for both wavelength and absorbance value in the UV and visible regions, from 250 nm to 650 nm, at bandwidths up to 20nm.
