Chromium

Analytical Periodic Table
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Location:  Group 6, Period 4
Atomic Weight:  51.9961
Coordination Number:  6
Chemical Form in Solution:  Cr(H2O)63+

Storage & Handling:  Keep tightly sealed when not in use. Store and use at 20 ± 4°C. Do not pipet from container. Do not return portions removed for pipetting to container.

Chemical Compatibility:  Stable in HCl, HNO3, H2SO4, HF, H3PO4. Avoid basic media. Stable with most metals and inorganic anions in acidic media.

Stability:  2-100 ppb levels stable for months in 1% HNO3 / LDPE container. 1-10,000 ppm solutions chemically stable for years in 1-5% HNO3 / LDPE container.

Cr Containing Samples (Preparation & Solution):  Metal (soluble in HCl); Oxides / Ores (chrome ore/oxides are very difficult to dissolve. The following procedures A - D are commonly used:

A. Fusion with KHSO4 and extraction with hot KCl. The residue fused with Na2CO3 and KClO3, 3:1
B. Fusion with NaKSO4 and NaF, 2:1
C. Fusion with magnesia or lime and sodium or potassium carbonates, 4:1
D. Fusion with Na2O2 or NaOH and KNO3 or NaOH and Na2O2.

Nickel, iron, copper, or silver crucibles should be used for D. Platinum may be used for A, B, and C; Organic Matrices (ash at 450°C followed by one of the fusion methods above or sulfuric / hydrogen peroxide acid digestions may be applicable to non oxide containing samples).

Atomic Spectroscopic Information:  (red text indicates severe at ~ concs.)
Technique / LineEstimated D.L.*OrderTypeInterferences
ICP-OES 205.552 nm0.006/.0008 µg/mL1ionOs
ICP-OES 284.325 nm0.008/.0007 µg/mL1ion 
ICP-OES 276.654 nm0.01/.001 µg/mL1ionCu, Ta, V
ICP-MS 52 amu40 pptn/aM-36S16O, 36Ar16O**
*ICP-OES D.L.'s are given as radial / axial view
**The 50Cr, 53Cr, 54Cr lines suffer from many more potential interferences from sulfur, chlorine, and argon compounds of oxygen, nitrogen, and carbon.

Chromium (Cr) Single-Element Standard
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