At 11:50 AM 6/29/01 -0400, Mike wrote:
>We are currently using Quantab titrator strips for chloride for our salt
>analysis to determine %water phase salt in product.
>
>While the strips work OK, I am looking for a better accuracy in
>determining salt content and % water phase salt.
>
>However, we would like to keep costs and time expenditures low, and also
>stay away from wet chemistry procedures (we don't really have a
>chemistry lab). Kind of looks like we want both ends and the middle
>here, but I may as well go for it.
The least expensive and reliable method for salt in this type of material
is via conductivity measurement. Brine content would obviously require a
moisture analysis (typically microwave for rapid, drying oven for slow).
The Quantab system is specific for chloride (or other silver precipitating
anions), while conductivity is non-specific, and would be influenced by
phosphates, for example. Conductivity measures "total salts", so you will
have a slight high bias vs standard chloride analysis.
The Quantab system is very accurate on pure salt solutions when the test
kit is fresh. It deteriorates over time, either in the bottle or from
reopening the bottle over shorter times. So unless you have a high rate of
turnover of bottles (e.g., every 2 weeks), the Quantab system may be
unreliable. It is for this reason that I no longer recommend it for salt
analysis of foods.
Sample preparation is of some importance: You need to extract the salt from
the muscle adequately. Cold water with a 10x - 25x dilution will generally
work in a blender. If you're using Quantabs, make sure you filter the
extract through a coarse filter (fast qualitative paper or a coffee
filter), otherwise you may impede uptake into the test strip.
Other rapid methods include ion-selective electrodes, such as chloride or
sodium to replace the measurement method.
Typically conductivity measurements result in an precision of about 0.2%
standard deviation and a bias < 0.3% relative to the Volhard standard method.
You should keep the dilution rate high (e.g., 25x) and the conductivity low
(e.g., < 2000 uS) in order to keep the conductivity response linear.
Let me know if you are interested in obtaining a method and equipment for
conductivity salt testing, email me privately and I can supply sources.
================================================================
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS e-mail: ral@lcfltd.com
Least Cost Formulations, Ltd. URL: http://lcfltd.com/
824 Timberlake Drive Tel: 757-467-0954
Virginia Beach, VA 23464-3239 Fax: 757-467-2947
"Vere scire est per causas scire"
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