in this issue:

Analytical Quick Tips  IV Line Humor  Samples containing Tungsten (W)  Guides and Papers  News from the Lab

Like the IV Line?   Tell a friend!

Problem with Au Stability in ICP-MS
Hi, I have a problem with Au stability in ICP-MS. I use 10% HCl. I get good calibration curves for other pgm's except for Au which increases with an increase in standards. How can I overcome this? What's the best argon flow rate I could use? What is the best container for storage and rinsing solution? read more...

Concerns About OsO₄ Formation in Multi-element Standards
Hello Dr. Gaines, I recently bought some individual standards from IV including Os@100ug/mL. I was planning on making an intermediate standard in a 2%HNO₃/0.5%HCl acid matrix. This will be a multi-element standard at varying concentrations. I'm concerned about the OsO₄ formation but I'm wondering if the presence of the other elements along with the 0.5%HCl will minimize this formation. read more...

Quantify Silicon in Silicone Oil by ICP-OES
Dr. Gaines answers two questions about quantify silicon in silicone oil by ICP-OES.
Read the first question as well as the follow-up question.

More Tips

Tungsten (W) is the most abundant of the group 6 elements (Cr, Mo, W) with an average concentration in the earth's crust of 190 ppm (140 ppm for Cr and 1.2 ppm for Mo). The element is found in minerals high in silica and is commonly found as the tungstate (WO₄= ) and associated with Ca⁺², Cu⁺², Fe⁺² and Mn⁺². Tungsten also occurs as the sulfide (WS₂, tungstenite). In addition to the analysis of W ores analytical chemists are asked to measure W in alloys, steels, ferrotungsten, silico-tungsten, tungstic oxide, tungsten powder, alkali tungstates and high purity metals such as niobium, tantalum, titanium, zirconium and their alloys. The analytical techniques used include ICP-MS (dl~ .000005 mg/L), cathodic stripping voltammetry ( dl~.001 mg/L), neutron activation analysis (dl ~ 0.005 mg/L), UV-Vis spectrophotometry (dl ~0.01 mg/L) and ICP-OES (dl~ 0.01 mg/L). Tungsten has the highest melting point (3370 C°) of the metals which has led to its use in incandescent light filaments. It is also used in cutting tools, steel, springs, valves, axles, contact points in spark plugs, and many other products where strength, hardness, durability, and resistance to corrosion are important in addition to a high melting point.

The chemistry of W is much more similar to that of Mo and bears little resemblance to the chemistry of Cr. Tungsten exists in oxidation states ranging from +6,+5,+4,+3, +2, 0 -1,-2 and -4. Tungsten's isotopes and relative natural abundances are (amu- atomic %) 180-0.13, 182-26.3, 183-14.3, 184-30.7, and 186-28.6. ICP-MS spectroscopists favor the 182 and 184 isotopes but all of the masses are subject to MO interferences from the appropriate Rare Earth elements. Sample preparations of ores and alloys typically involve the combined use of HNO₃ and HF making +6 the most common oxidation state. In neutral and acidic media tungstates (+6) have a great tendency to hydrolyze out of solution as WO₃ (yellow powder), making HF an almost essential co-acid in sample preparations where higher W concentrations may require a considerable excess amount of HF ( ~ 3% v/v HF for concentrations of ~ 1 to 10 g/L W). The tungstate is stable in basic media making alkali fusions followed by dissolution in water possible when the use of HF is not acceptable. Inorganic Ventures prepares single element 1000 µg/mL and 10,000 µg/mL W CRMs from the metal (W°) using HNO₃ and HF where HF is in excess (~ 3% v/v) to prevent hydrolysis. At Inorganic Ventures we prepare multi elemental blends of W matrices that favor dilute nitric with trace HF, and we have found solutions down to the low ppb level to be chemically stable for months to years. Tungsten should not be mixed with elements that form insoluble fluorides (group IIA and IIIA) unless the concentrations are = 1 mg/L of each and the acid content is at least 1 % v/v and preferably = 5% v/v.

Like Mo, W is determined in a wide range of environmental, biological, agricultural, metallurgical, and industrial (chemical industry) samples. There is a great risk of contamination when grinding, cutting and mixing equipment is used in the sampling/sample preparation. The following precautions should be considered:

• Many tools that pulverize, mix, cut, pulverize, etc. contain W. Attempt to use devices made of ceramics, silica/quartz, and polymers where possible.
• The collection of biological samples are also at risk of contamination due to the very low (ppb) levels of W typically present. The use of steel needles, and scalpels or any metallic object that may contain W should be avoided.

The risk of contamination is great for the group VI B elements (Cr, Mo, W) when alloys, steels and grinding equipment are used in some part of the sample collection or preparation. For more on sample contamination risks see chapters 8, 9 and 10 of the Inorganic Ventures 'Trace analysis Guide':
http://www.inorganicventures.com/tech/trace-analysis/environmental-contamination

For general information on sampling and sub-sampling see:
http://inorganicventures.com/tech/trace-analysis/sampling-and-subsampling

To read full article, click here.

Upgraded Technical Guides with New Content 12-6-2011 · Permalink

We have just upgraded several of our online technical guides! If you haven't seen them yet, Sample Preparation, ICP Operations, and Trace Analysis are great resources for a variety of needs and applications. Check them out and let us know what you think!

SOLIDS... one of our most Popular Quality Control CRMs EVER! 10-15-2011 · Permalink

Solids CRM analytes include: Dissolved Solids (filterable residue), Suspended Solids (non-filterable residue), Total Solids (total residue). These CRMs have an expiration date of one year and follow the ISO Guide 34 and ISO 17025 guidelines.

Metals in Cyanide Matrix CRMs from Inorganic Ventures 9-15-2011 · Permalink

Check out our popular line of Metals in Cyanide Matrix CRMs. These CRMs have an expiration date of one year and follow the ISO Guide 34 and ISO 17025 guidelines. If you do not see what you need ask for a custom! Ninety-nine percent of customs ship in 5 business days and free rush service is available!

Complete Line of pH CRMs 8-15-2011 · Permalink

This pH line ranges from pH of 2 to pH of 12 with multiple volumes in stock! These CRMs have an expiration date of one year and follow the ISO Guide 34 and ISO 17025 guidelines.
 

Q: Anyone know any jokes about sodium?
A: Na

Making bad chemistry jokes because all the good ones Argon

Q: What is the most important rule in chemistry?
A: Never lick the spoon!

Helium walks into a bar,
The bar tender says "We don't serve noble gasses in here."
Helium doesn't react.

Silver walks up to Gold in a bar and says, "AU, get outta here!"

Two chemists go into a restaurant.
The first one says "I think I'll have an H₂O."
The second one says "I think I'll have an H₂O too" -- and he died.

Q: What did the scientist say when he found 2 isotopes of helium?
A: HeHe

Q: Why was the mole of oxygen molecules excited when he left the singles bar?
A: He got Avogadro's number!

Sample Preperation Guide  · UPDATED
This Sample Preparation guide is intended to provide specific and highly detailed information about certain elements in regards to sample preparation.

Trace Analysis Guide  · UPDATED
Dr. Paul Gaines presents an essential guide for trace analysts at any level of experience. Topics cover all phases of sample collection, preparation, measurement, and data analysis.

ICP Operations Guide  · UPDATED
This guide is intended for anyone operating and preparing samples and standards for measurement using ICP.

Interactive Periodic Table
An interactive periodic table that identifies each element's name, atomic weight, and oxidation state(s) as you scroll over an element's symbol.