External services

Analytical Chemistry

Service presentation

The Analytical Chemistry Laboratory (LabQA) is equipped with a continuous flow autoanalyser, (FUTURA model manufactured by ALLIANCE INSTRUMENTS), a TOC-L analyser with TNM-L module for TOC manufactured by SHIMADZU, and an ion chromatograph for the analysis of major ions from METROHM.

The ALLIANCE FUTURA is equipped to analyse the concentration of dissolved inorganic nutrients (Nitrate, Nitrite, Ammonium, Phosphate, Silicate).

The SHIMADZU TOC-TN is equipped to analyse the concentration of total organic carbon (TOC), non-purgeable organic carbon (NPOC), and total nitrogen (TN).

The METROHM ion chromatograph is equipped to analyse the concentration of cations (Calcium, Sodium, Magnesium, Ammonium, Potassium) and major anions (Fluoride, Bromide, Chloride, Nitrate, Nitrite, Phosphate and Sulphate).

All three systems can handle liquid samples. They can be adapted for both freshwater and saltwater sample analysis.

Applications

Nutrient analysis applications include:

Phytoplankton control and biomass production in certain areas of interest.
Characterisation of water quality in different environments.
Analysis and early detection of environmental pollution in aquatic ecosystems.
Temporal evaluation of indicative variables of changes in the trophic level of the system that may affect fish productivity.
Wet atmospheric deposition analysis.

Total organic carbon (TOC), total nitrogen (TN) and major ion analysis applications include:

Characterisation of water quality and dissolved organic matter in various environments.
Analysis and early detection of environmental pollution in aquatic ecosystems.
Environmental research of various kinds in surface freshwater, soil, groundwater and marine environments.

Information for users

The service can be hired by both internal (CSIC) and external staff (other research centres), as well as by companies. If you require any information or advice on sample treatment and conservation, please contact the responsible technician.

Internal staff, whether from the centre or temporarily attached to it, also have access to the other laboratories (without associated service).

Contact

The responsible technician will provide you with the necessary information on service conditions, fees and other specifications.

Analytical methods

The analytical methods used are scientifically validated and certified by international certifications such as ISO, AOAC, BATF, USEPA, AFNOR and COFRAC.

NITRATES + NITRITES

Nitrates are reduced to nitrites using Vanadium (III) chloride. Nitrites react with sulphanilamide under acidic conditions to form a diazo compound. With N-(1-Naphthyl)ethylenediamine, the mixture turns pink. Optical density is measured at a wavelength of 520/540nm.

Reference: Doane TA and Horwath WR. 2003. Spectrophotometric determination of nitrate with a single reagent. Analytical Letters 36(12):2713-2722; Miranda KM, Espey MG, Wink DA. 2001. A rapid, simple spectrophotometric method for simultaneous detection of nitrate and nitrite. Nitric Oxide: Biology and Chemistry 5(1):62-71.)

PHOSPHATES

Ammonium heptamolybdate reacts with orthophosphate under acidic conditions to form phosphomolybdic acid. This mixture is reduced to molybdenum blue with ascorbic acid. The reaction is catalysed with antimony and potassium tartrate. Optical density is measured at a wavelength of 880nm.

Reference: Grasshoff K, Kremling, K, Ehrhardt M. 1999. Methods of Seawater Analysis. 3^rd revised and extended edition. Wiley, Weinheim, Germany.

AMMONIUM

The method is based on the reaction of ammonium with ortho-phthalaldehyde (OPA) in the presence of sulphite at 70ºC. The resulting complex passes through a detector equipped with a fluorescence black lamp, which excites the complex at 370nm and records the resulting emission at 460nm.

Reference: Kérouel R and Aminot A. 1997. Fluorometric determination of ammonia in sea and estuarine waters by direct segmented flow analysis. Marine Chemistry 57: 265-275.

NITRITES

Nitrites react with sulphanilamide under acidic conditions to form a diazo compound. With N-(1-Naphthyl)ethylenediamine, a pink compound is formed. Optical density is measured at a wavelength of 520/540nm.

Reference: Grasshoff K, Kremling, K, Ehrhardt M. 1999. Methods of Seawater Analysis. 3^rd revised and extended edition. Wiley, Weinheim, Germany.

SILICATES

Silicate reacts with molybdate under acidic conditions (1<pH<2) to form a complex when the Si:Mo ratio is 1:12. This is reduced with ascorbic acid to form a blue compound measured at 810nm. Oxalic acid is added to prevent interference caused by the phosphomolybdic complex.

Reference: Grasshoff K, Kremling, K, Ehrhardt M. 1999. Methods of Seawater Analysis. 3^rd revised and extended edition. Wiley, Weinheim, Germany.

TOTAL ORGANIC CARBON

The liquid sample undergoes oxidative combustion at high temperature (680ºC) after removing inorganic carbon by acidification.

Reference: Álvarez-Salgado X and Miller AEJ.1998. Simultaneous determination of dissolved organic carbon and total dissolved nitrogen in seawater by high temperature catalytic oxidation: conditions for accurate shipboard measurements. Marine Chemistry 62: 325–333.

TOTAL NITROGEN

The liquid sample undergoes oxidative pyrolysis (720ºC) and the resulting nitric oxide, after contacting O3, is converted to N2O, subsequently emitting a photon detected by chemiluminescence.

MAJOR IONS

Ion chromatography allows the analysis of soluble anions and cations in aqueous samples. Ions are separated by ion exchange between the mobile and stationary phases (column). The ions are retained in the column based on their charge, sequentially detected by a conductivity detector, and recorded in a chromatogram, representing the signal intensity of each ion according to its retention time.

Reference: Haddad, P.R., and Jackson, P.E. 1990. Ion chromatography. Principles and applications. Elsevier, Kensington, Australia, vol 46, 1^st ed. 775pp.