That being said, in practice it is more nuanced. Claims are considered to be definite, as required by the second paragraph of 35 U.S.C. § 112, when they define the metes and bounds of a claimed invention with a reasonable degree of precision and particularity. See In re Venezia, 530 F.2d 956,958, 189 USPQ 149, 151 (CCPA 1976). The issue then becomes whether a PHOSITA would have understood, as of the time of the filing of the application, what the scope of the claim was and what the trademark stood for.

For example, say you have the following claim:
A method comprising: sending an email to a computer, wherein said computer is running Windows. (poorly drafted just to show point).

This is clearly indefinite because there are a large number of goods that sell under the umbrella of the Windows trademark (95, 98, Me, XP, Vista, 7) and likely includes future unknown and undefined versions of Windows.

Now what distingishes good practitioners/examiners is how they argue the harder question of when the claim is for Windows 7.

Assume Shell gasoline is, as of today, composed of chemicals A, B, and C. Assume further that today I claim a new type of engine that runs on “Shell Gasoline,” and that using trademarks in claims is OK (again, just for explanation’s sake).

What I’ve really invented is an engine that runs on a gasoline made of A, B, and C, and that’s all I should be entitled to in a patent. But I haven’t claimed an engine that runs on ABC gasoline, I’ve claimed an engine that runs on “Shell” gasoline. So what if, two years from now, Shell changes their formula to A, B, C, and D. Assuming my engine also runs on the new ABCD Shell Gasoline, I will have become entitled to a broader invention than I actually conceived of by virtue of Shell changing its product. When I filed my app, all I had invented was a machine that ran on ABC Shell gasoline, but now my invention covers other types of gas because I described it in the claims as “Shell Gasoline,” which would theoretically cover ABC Shell gasoline and also ABCD gasoline.

I think that’s why they don’t let you use trademarks in claims. They only identify the producer and not the particular product. The producer can change the product, so when you claim “Shell gasoline,” it is indefinite under 112, 2nd as to what you are claiming.

2173.05(d) Exemplary Claim Language (“for example,” “such as”) [R-1]

Description of examples or preferences is properly set forth in the specification rather than the claims. If stated in the claims, examples and preferences >may< lead to confusion over the intended scope of a claim. In those instances where it is not clear whether the claimed narrower range is a limitation, a rejection under 35 U.S.C. 112, second paragraph should be made.

The presence of a trademark or trade name in a claim is not, per se, improper under 35 U.S.C. §112, second paragraph.
2100-29 If the trademark or trade name is used in a claim as a limitation to identify or describe a particular material or product, the claim does not comply with the requirements of the 35 U.S.C. §112, second paragraph.

Still, I believe something like “a phosphate based synthetic surfactant detergent” is needed to make it definite.

“Claim 5. The method of claim 1, wherein clothes are washed with a detergent such as Tide. Would not be rejected.”

is correct.

796.03(d):
Claim [1] contains the trademark/trade name [2]. Where a trademark or trade name is used in a claim as a limitation to identify or describe a particular material or product, the claim does not comply with the requirements of 35 U.S.C. 112, second paragraph. See Ex parte Simpson, 218 USPQ 1020 (Bd. App. 1982). The claim scope is uncertain since the trademark or trade name cannot be used properly to identify any particular material or product. A trademark or trade name is used to identify a source of goods, and not the goods themselves. Thus, a trademark or trade name does not identify or describe the goods associated with the trademark or trade name. In the present case, the trademark/trade name is used to identify/describe [3] and, accordingly, the identification/description is indefinite.

The example dgspambot uses is applicable to the specification. Here one needs to add info to make the trademark ref enabling.

That said, I think something more definite like “a phosphate based synthetic surfactant detergent, such as Tide” would be more appropriate for the specification.