The BioUltra label has been assigned to a group of basic reagents with a well-defined high purity. These reagents are principally used in biochemistry and life science applications. BioUltra products are basic reagents designed for use in biochemical and biological techniques where large amounts of reagent are required in comparison to the quantities under investigation.

The BioUltra Reagent Certification guarantees:

  • a homogeneous appearance (form, color)
  • a homogeneous and clear appearance in solution (solubility test)
  • zero residue in the filter test
  • limited UV absorbance at key biochemical wavelengths
  • the pH value of an aqueous solution within a defined range

BioUltra reagents are carefully handled to ensure a very high quality product at the time of packaging. Cross-contamination is avoided by packing BioUltra products in a controlled environment, void of both dust and moisture. Each package is securely scaled by screw cap and is identifiable by a batch number and packaging date.

BioUltra Reagents Tests

Solubility and Appearance in Solution

Solubility is usually checked in a 1 M test solution in water (Product No. 95304) at 20 °C. Where appropriate, more diluted or more concentrated solutions in water or hydrochloric acid are used. The appearance of the solution is checked for absence of foreign color and is described as follows: Solubility: completely soluble, colorless (0.5 M in water, 20 °C)

Checking for Insoluble Matter by Filter Test

Filter test results are the appropriate criteria for confirming the absence of insoluble matter. 20 ml of the test solution are filtered through a Millipore 0.45 mm filter membrane. After air-drying the filter membrane is compared with a blank. This result is expressed as follows: Insoluble matter: passes filter test.

Ultraviolet Absorption (UV)

The UV absorption of the appropriate test solution is measured at wavelengths of 260 and 280 nm in a 1 cm quartz cell against the solvent. The figures are shown in dimensionless absorption units (OD). These results are given as: UV: A260< 0.02 A280< 0.01 (3 M in water).

pH of Solution

The pH of the test solution is measured by a combined glass electrode at 20 °C. The results are given in pH units (-log [H+]). Very dilute solutions including those in hydrochloric acid are not determined. The result is expressed as follows: pH: 3.0-4.0 (0.5 M in water, 20 °C)

BioUltra reagents for Molecular Biology


Reagents belonging to the group BioUltra for Molecular Biology are tested, in addition to the general BioUltra tests, for their suitability in molecular biology experiments. Sigma guarantees for its molecular biology reagents absence of the following enzyme traces:

  • RNases
  • DNases
  • Phosphatases
  • Proteases

Absence of the above mentioned enzyme traces is measured by the following methods:


RNase traces are determined by following the fluorescence decrease of the MS 2 RNA complex with a fluorescing RNA intercalator of the appropriate wave length.


DNase traces are measured by following the fluorescence decrease of a complex of the plasmid DNA with a fluorescing DNA intercalator.


Protease traces are checked by following the fluorescence increase in a system containing the substrate resorufin-casein.


The tests for phosphatase traces are performed by measuring the fluorescence increase in a system containing the substrate 4-methylumbelliferyl phosphate.

Analysis and BioUltra Reagent Guarantee

In addition to the previously described tests (see BioUltra Certification and special quality for molecular biology), BioUltra Reagents are subject to strict analysis in our laboratories to meet the indicated guarantee requirements. The following list provides information on the methods.

Content Determination and identification of molecular composition: GC, HPLC, TLC, UV, NMR.
Determination of a functional group: titration.
Determination of enantiomeric purity.
Determination of the elemental composition of the molecule: elemental analysis, atomic absorption spectroscopy (AAS).

Titration Aqueous (T), non-aqueous (NT), redox (RT), argentometric (AT), complexometric (KT)

C H N automatic elemental analysis
Assay of halogens, sulfur and phosphorus

Chromatography Composition by peak area percentage in:
- gas chromatography (GC)
- liquid chromatography (HPLC)
- thin layer chromatography (TLC)

Spectroscopy Identity control and purity by means of:
- infrared spectroscopy (IR)
- proton resonance spectroscopy (NMR)
- ultraviolet spectroscopy (UV)
- fluorescence spectroscopy (FL)

Trace analysis Assay of trace impurities with:
- inductively coupled plasma atomic emission spectrometry (ICP-AES) atomic -
  absorption spectrometry (AAS)
- polarography (PG)

Physical data - Melting point (mp) in an open capillary
- Solidification point (sp)
- Boiling point (bp) acc. to an improved Siwoloboff method or determination of the
  boiling range acc. to A.S.T.M., ACS, Ph. Eur. etc.
- Density (d204), at 20 °C based on the density of water at 4 °C.
- Refractive index (n20D) at 200 and 589 nm.
- Optical rotation ( [ a ]20546, [ a ]20D) measured at the specified wavelength at 20 °C.
- pH value of the specified solution, measured with a combined glass electrode