Glass cuvette wrong measurement?

[simon48]

Have the alk checker and always use syringe to add water the level marker is way out!

[this is me]

Never trust the marking on the vial. It's the fault of the vial manufacturer and they usually have their +/-tolerances in marking where the mark should be.

[shaggss]

So Hanna which is it? Do we use the marking on the vial or measure with a syringe? Another long silence from Hanna........

[Blurry]

Use a syringe and mark the vile yourself. Be sure to mark at the bottom of the miniscous as mentioned in post #5

[Barfly]

Originally Posted by shaggss

So Hanna which is it? Do we use the marking on the vial or measure with a syringe? Another long silence from Hanna........

I have personally tested the vials. I have the PO4 Checker and the Alk checker. The cuvettes are marked differently. The PO4 cuvettes seem to be spot on, but the Alk cuvettes are without a doubt marked wrong. I have also tested the cuvettes that came with a friends Ca checker and those were marked wrong as well.

To test I used a 10ml syringe and filled each cuvette. I ran the test 5 times and varied the order in which the cuvettes were filled. Bottom line, regardless of what Hanna claims, the cuvettes are not marked correctly.

As I've stated before, I will not purchase another item, including reagents, from Hanna until they prove to me that they care about the end user. In my opinion, Hanna has failed terribly in this regard.

[LinkinReef]

Nothing from Hanna huh?...

[Confuse]

Bump for an answer to this age old question? Also, does anyone know where I can buy a graduated cylinder locally?

[xp964]

While I personally feel that using a syringe to measure water is preferable, and is certainly never wrong, Chemistry has told us several times that:
1. On every shipment of cuvets we receive, they perform sample checks to ensure that the 10 mL line is measured correctly.
2. For every method we have, they have run analysis on filling the cuvet to the line versus measuring with a syringe, and found no statistically significant difference in the results.

Thank you,
Hanna USA

[chercm]

I used the syringe and measured 10 ml but it still goes below the line in the viral

[Blurry]

Originally Posted by xp964

While I personally feel that using a syringe to measure water is preferable, and is certainly never wrong, Chemistry has told us several times that:
1. On every shipment of cuvets we receive, they perform sample checks to ensure that the 10 mL line is measured correctly.
2. For every method we have, they have run analysis on filling the cuvet to the line versus measuring with a syringe, and found no statistically significant difference in the results.

Thank you,
Hanna USA

If every shipment the vial line is measured and they are all correct why do an analysis of filling to the line or using a syringe?

[BrklynArch]

i just found this thread and i also get a higher 10ml line when i measure w a syringe. I thought it was either my mistake or my 10 ml syringes were off.
But i must be wrong because "Chemistry said".....i have been completely turned off to this company and the way they handle customer service. I am done with Hanna

[xp964]

Originally Posted by BrklynArch

i just found this thread and i also get a higher 10ml line when i measure w a syringe. I thought it was either my mistake or my 10 ml syringes were off.
But i must be wrong because "Chemistry said".....i have been completely turned off to this company and the way they handle customer service. I am done with Hanna

I wish that I could give you other answers, but unfortunately we're limited to the information to which we have access. The chemistry department at Hanna Inc (our international parent company) is responsible for analyzing the accuracy of the cuvettes, and they have repeatedly told us that they check each batch to makes sure the markings are within a tolerated accuracy range, and that within that range there is no statistically significant difference in results.
This does does not preclude the possibility of individual cuvettes being incorrect, as we purchase thousands of cuvettes yearly, and there is no practical way for us to check each individual one. We do lot checks, which is an accepted industry standard. If you feel that your cuvette is significantly in error, please contact tech support (tech @ hannainst.com, 1-800-426-6287 x 34) for replacement.

I am sorry that you find our customer service lacking. We have certain personnel that respond on this forum, and we frequently do not have the answers you are looking for. We have always and will always do our best to obtain them for you, but we are one branch office out of 60. Our requests for information and/or analysis must be submitted to senior management for review and approval before it is even assigned to the appropriate department's schedule. As such, we who respond here frequently refrain from doing so if we have nothing new to add, as such responses seem to instigate a negative response, which serves no one.

Thank you,
Hanna USA

[bsagea]

Happened on this thread by chance, having 3 checkers I decided to break out the syringe and check the checkers! Five of my cuvettes were identical although slightly higher than the line when filled with the syringe. The sixth cuvette when filled was substancially "above" the 10ml line. Approx. 3/16". Checked that one three times and had the same results each time. I marked that one for emergency use only.

[Bela N]

In part I tend to side with Hanna. One aspect of this discussion that no one has brought up is the "hobby" nature of the testers. Fifty dollars for a single wavelength mini spectrophotometer is extremely reasonable. However most are crying for 2 decimal place accuracy with 0.01% error when it comes to precision . . . . . those are unreasonable exceptions from a $50 piece of equipment. If you were using an $8,000 spectrophotometer, $600 Ependorff pipette, & a $100 cuvette in the hands of properly trained lab tech or researcher then you would have grounds for complaints. FYI our High school has all of the above except the $100 cuvettes, we use a cheap $12 student grade cuvette. Please note: a proper but cheap cuvette is 1/5th the price of the entire checker!

What is a cuvette?

For those that do note know, a proper round cuvette, is optically analyzed while being rotated and if the glass at the sensor opening is within the required tolerance, for the price range, the top of the cuvette is marked with a line. This line MUST always line up with the corresponding line on the spectrophotometer. If the cuvette is not within the required tolerance it is discarded. While on the topic of precision/tolerance, I heard a story of a student at The University of Western Ontario, Chemistry Department, who accidentally put a finger print on a $20,000 analytical cuvette, rendering it useless . . . . that has to hurt!

Hanna Checker Cuvettes?

I don't thinks so!! I am fairly confident they are "vials" intended for "hobby" use and are not true cuvettes. The lack of an alignment mark seems to confirm this. Also these vials, minus the 10 mL mark, are identical to my insect specimen storage vials. I suspect that the quality of glass used in a vial compared to a cuvette are significantly different. Important hint - for those looking to improve their precision (not necessarily accuracy) always put the vial in the same way. I put a mark on my checker & I line up the "1" in the 10 mL making. Since these are vials, the glass thickness could be anywhere from 5-10% thicker on one side then the other. This of course will change the result. Hanna should consider selling true optically matched cuvettes for those, like myself, that would be willing to pay the price (not $20,000 of course but in the $10-$20 range would be nice). We should NOT fault Hanna, you are getting what you pay for! IMO the Checker is an EXCELLENT compromise for the hobbyist.

The Good

The Checker has solved the dreaded human interpretation (subjective & qualitative) problem associated with testing! By that I mean matching the colour or when it turns from pink to blue. I still remember the agony of titration, going from 95% pink with 5% blue to 95% blue with 5% pink, with a 3 drop difference, where does it change colour? Do you pick 50/50 or 100% blue? What if it is more grey? If you use consistent & proper technique you will get more reliable results with the checker (quantitative) than by human subjective interpretation.

The Bad

1. Those _ _ _ _ _ _ packets, I hate them! Not because of the poring, but the sticking of the powder to the sides and especially in the folds (and yes I have seen the video). The worst is when the powder is sealed in the foil and you can not get it out.

PAY ATTENTION HANNNA Follow LaMottes lead and package your powders in compressed pellets (like Aspirin). Yes you have to shake more to dissolve the pellet but it would increase dose consistency 100%.

2. Consistently dispensing 0.1 mL (100 uL). This is not Hanna's fault. It is a mater of stoichiometry and economics. The ratio of components is determined by the chemical reaction (stoichiometry) and is out of Hanna's control. To use a larger proportions would be too expensive. If money is no issue for you then use 10 packets in 100 mL an then add 1mL of salt water and you will get more consistent results, but pay 10X more per test.

I know it is not nice to gloat but I cant help myself. I do not have the 0.1 mL problem. I use a $600 Eppendorf pipette, from my DNA labs. I could if I wanted to, dispense 0.005 mL with 99% accuracy if I needed to Is everyone jealous??? FYI There is a single volume 0.1 mL inexpensive, non-Eppendorf, version available for around $50. By the way, I am not using school equipment at home. I look after our schools 140 gal mixed reef tank. I am an insect & tarantula guy, I do not have a tank with fish & corals at home. Tarantulas, snakes & lizards yes. I should add, I got stuck looking after the tank when the previous caretaker had kids & could not look after it. I am now HOOKED what a FANTASTIC hobby !!!!!!!!!!!!!!


If forum members are interested I could talk more about equipment, technique & methodology.

Bela

[BeanAnimal]

Originally Posted by xp964

The chemistry department at Hanna Inc (our international parent company) is responsible for analyzing the accuracy of the cuvettes, and they have repeatedly told us that they check each batch to makes sure the markings are within a tolerated accuracy range

This brings me back to the published accuracy rates. Real world or ideal? (rhetorical)...

What strikes me as odd:

Originally Posted by xp964

8/15/2012
...we purchase thousands of cuvettes yearly, and there is no practical way for us to check each individual one. We do lot checks, which is an accepted industry standard.

Originally Posted by xp964

8/31/2011

Our cuvettes are hand blown on site by a technical glass blower.
The lines are marked by volume.

I am not trying to be confrontational (at all), but am confused by the statements. Are the cuvettes purchased from a 3rd party or blown on-site by Hanna International (the parent?) and resold to Hanna child companies? Not that it really matters... (well it kind of does, as it is complete waste of time to pay somebody to hand mark these and if it is done in house, then don't bother and just send 10ml syringes with the kits).

[BeanAnimal]

Originally Posted by Bela N

In part I tend to side with Hanna. One aspect of this discussion that no one has brought up is the "hobby" nature of the testers. Fifty dollars for a single wavelength mini spectrophotometer is extremely reasonable. However most are crying for 2 decimal place accuracy with 0.01% error when it comes to precision . . . . . those are unreasonable exceptions from a $50 piece of equipment.

Respectfully Bela, that is not what most are crying about.

The general gripe is that with a little thought these products could be so much better. They are plagued with small problems that are mostly design choices that could have (can be) easily corrected and what appears to be QC issues with reagents (cuvettes, syringe tips, etc). I will leave the CA checker out of that heading, as it (in my opinion) has bigger problems.

1. Those _ _ _ _ _ _ packets, I hate them! Not because of the poring, but the sticking of the powder to the sides and especially in the folds (and yes I have seen the video). The worst is when the powder is sealed in the foil and you can not get it out.

Yes, pellets or 2-part pill capsules, even break off tab hard capsules would be better.

To that end and back to THIS topic...

Why does Hanna spend the time and money to "hand mark, test and then batch test" cuvettes, when INSTEAD of marking them at all, they could just put a 10 cent plastic syringe in the package or reagent refill.

1) You can't fill the cuvettes to any degree of accuracy without a syringe or pipette
2) It would save cost on hand marking each vial (cuvette, whatever)


Why does Hanna spend the money to design and manufacture a different size clamshell case for each checker instead of using a one-size-fits-all case that actually fits the kit, tools and refills. Silly and costly.

Simple things, but they all add up and erode value and user friendliness.

Back to my point about the "complaints" there are a dozen little issues like this that erode away at the value of these checkers and the high per test cost. These checkers could be an awesome value instead of a constant headache. Most of us don't mind the cost and in fact would pay more if they would just work out the bugs and problems.

[xp964]

Originally Posted by BeanAnimal

This brings me back to the published accuracy rates. Real world or ideal? (rhetorical)...

What strikes me as odd:




I am not trying to be confrontational (at all), but am confused by the statements. Are the cuvettes purchased from a 3rd party or blown on-site by Hanna International (the parent?) and resold to Hanna child companies? Not that it really matters... (well it kind of does, as it is complete waste of time to pay somebody to hand mark these and if it is done in house, then don't bother and just send 10ml syringes with the kits).

Hi Beananimal,
In the year between those postings, we switched from making them ourselves to purchasing them, as the volume was too great for our glassblower to keep up with.

As for your other points, they are valid criticisms and we have passed them on to Hanna International, who is responsible for all manufacturing decisions.

Thank you,
Hanna USA

[BeanAnimal]

Thank you for the response. It is (and has been) my hope that Hanna is willing to listen to the end user issues and make changes to better the products. It would not take much to greatly improve the checker products.