Search: calcium

Calcium in wort is measured using AAS by directly aspirating the diluted sample into a nitrous oxide-acetylene flame; the measurement is made at 423 nm.

Lanthanum chloride reduces interference.

Magnesium ions are calculated by subtracting concentration of calcium ions (W-000.17.031 - Calcium in Wasser, Komplexometrische Bestimmung mit EDTA) from the total hardness (W-000.11.031 - Gesamthärte in Wasser). 

Inductively coupled plasma optical emission spectroscopy (ICP-OES) is a fast and reliable method for the laboratory analysis of metals. Inductively coupled plasma (ICP), a high frequency field of ionized gas, serves as a medium for atomizing and exciting the substances found in samples. Liquid, dissolved or aerosol samples are injected into the ionized gas stream. In emission spectroscopy, ICP can be used in conjunction with a number of optical and electronic systems either simultaneously or sequentially in multi-element spectrometers. In the plasma, the atoms and ions are excited to a higher energy state bringing about the emission of electromagnetic radiation (light), primarily in the ultraviolet and visible region of the spectrum. Metals ordinarily occur as ions in the temperature range typical for ICP of 6000 to 10000 K; however, non-metals and metalloids are only partially ionized.

ICP-OES operates within a very wide range. This usually encompasses six orders of magnitude in concentrations smaller than μg/l up to g/l, depending upon the element and the concentrations used for the set of analysis data. With ICP-OES, beer and wort can also be analyzed without prior processing of the samples, in contrast to AAS. Methods for determining the following in beer and wort will be described below: Al, B, Ba, Ca, Co, Cu, Fe, K, Mg, Mn, Mo, Na, P, Si, Sr, Sn and Zn.

According to DIN 38409 part 6 (January 1986) “hardness” is defined as the calcium and magnesium ion content of a water sample. In particular cases, barium and strontium ions may also contribute to hardness. Even though the term hardness is not a scientific one and in principle is even legally objectionable since no SI unit exists for it, hardness is still indispensable, as it simplifies the terminology. For this reason, the somewhat dated units are still deemed acceptable alongside the current mg/l, mval/l and mmol/l. The unit “Deutscher Grad” (degrees German hardness), 1 °d (in the past, also known as 1°dH) is equivalent (based on CaO) to 0.3566 mval = 0.179 mmol/l: *)

*) SI units recognized in legal and commercial transactions, whereby °d should be expressed in mmol/l

10.00 mg/l CaO = 7.15 mg/l Ca²⁺ = 0.3566 mval/l

7.19 mg/l MgO = 4.34 mg/l Mg²⁺ = 0.3566 mval/l

For the unit 1 mval/l, the values shown above are higher by a factor of 2.804 (1/10 of the CaO equivalent weight).

28.04 mg/l CaO = 20.04 mg/l Ca²⁺ = 2.804 °d

20.15 mg/l MgO = 12.15 mg/l Mg²⁺ = 2.804 °d

An alkaline earth ion concentration of 1 mg/l corresponds to:

1 mg/l Ca²⁺ = 0.1399 °d = 0.0499 mval/l hardness

1 mg/l Mg²⁺ = 0.2306 °d = 0.0822 mval/l hardness

Calcium and magnesium are the principal alkaline earth metal ions found in natural waters.

For certain applications and/or treatment processes, knowing the total hardness is insufficient, since understanding which alkaline earth metals are responsible for it is important (usually calcium or magnesium ions). These cations are also paired with anions, in which case the ions of carbonic acid play a significant role (carbonate and hydrogen carbonate ions).

The subgroups of hardness can be characterized as follows:

Calcium or lime hardness (Ca-H):

The portion of the water hardness caused by calcium ions.

Magnesium or magnesia hardness (Mg-H):

The portion of the water hardness caused by magnesium ions.

Total hardness (TH):

This term encompasses the sum of the individual types of hardness (Ca-H + Mg-H).

Carbonate hardness (CH):

The carbonate hardness corresponds to the concentration of alkaline earth metal ions equivalent to the hydrogen carbonate and carbonate ions present in the water. These ions are measured in mval/l through determination of the m value. Water that does not require acid for neutralization to reach the m value possesses no carbonate hardness (pH < 4.3). The m value corresponds to the carbonate hardness in mval/l. This is true as long as this value does not exceed the total hardness in mval/l, since by definition the carbonate hardness cannot exceed the total hardness. Water with an m value that exceeds the total hardness in mval/l is called “sodium alkaline” since it contains sodium. In selecting the treatment process, it is advisable to differentiate between calcium and magnesium carbonate hardness (Ca-CH and Mg-CH).

Non-carbonate hardness (NCH):

This is defined as the difference between total hardness and the carbonate hardness and thus, as that portion of calcium and magnesium ions for which no equivalent bicarbonate and carbonate ions are present in the water, but for which an equivalent quantity of other ions exist (e.g., hydroxide, chloride, sulfate, nitrate, phosphate, silicate, humate). Waters, whose m value is ≥ TH (mval/l), do not exhibit non-carbonate hardness.

Required analysis data:

• calcium ion content in mg/l or mval/l

• magnesium ion content in mg/l or mval/l

• acid required to reach the m value in mval/l

Calcium ions are bound by the disodium salt of ethylenediaminetetraacetic acid (EDTA) as water-soluble chelates (undissociated complexes). Calconcarboxylic acid serves as an indicator due to its specificity for calcium ions.

Inductively coupled plasma atomic emission spectroscopy (ICP-AES) is an analytical technique for detecting and determining concentrations of elements by measuring their line-emission spectra. The solution under analysis is atomized and the aerosol is transported into an inductively coupled plasma (ICP) with the aid of a carrier gas at which point the elements enter an excited and unstable state. When they return to their ground state, the atoms radiate. Their emission spectra are measured using a spectrophotometer. The intensity of the emission spectra is measured with detectors (photomultipliers). Quantitative results are possible through calibration with a standard, though over a wide range (normally multiple orders of magnitude) a linear relationship between the intensity of the line-emission spectra and the concentration of the elements exists. The elements can either all be determined simultaneously or each one sequentially.